Iqsoft Guarantees Satisfaction

Or Your Money back !!!

Ask for a quote
Ingenuity Mars Helicopter Gets Off the Ground

NASA’s Ingenuity Mars Helicopter Succeeds in Historic First Flight


NASA’s Ingenuity Mars Helicopter took this shot while hovering over the Martian surface on April 19, 2021
NASA’s Ingenuity Mars Helicopter captured this shot as it hovered over the Martian surface on April 19, 2021, during the first instance of powered, controlled flight on another planet. It used its navigation camera, which autonomously tracks the ground during flight.
Credits: NASA/JPL-Caltech

Monday, NASA’s Ingenuity Mars Helicopter became the first aircraft in history to make a powered, controlled flight on another planet. The Ingenuity team at the agency’s Jet Propulsion Laboratory in Southern California confirmed the flight succeeded after receiving data from the helicopter via NASA’s Perseverance Mars rover at 6:46 a.m. EDT (3:46 a.m. PDT).


“Ingenuity is the latest in a long and storied tradition of NASA projects achieving a space exploration goal once thought impossible,” said acting NASA Administrator Steve Jurczyk. “The X-15 was a pathfinder for the space shuttle. Mars Pathfinder and its Sojourner rover did the same for three generations of Mars rovers. We don’t know exactly where Ingenuity will lead us, but today’s results indicate the sky – at least on Mars – may not be the limit.”


The solar-powered helicopter first became airborne at 3:34 a.m. EDT (12:34 a.m. PDT) – 12:33 Local Mean Solar Time (Mars time) – a time the Ingenuity team determined would have optimal energy and flight conditions. Altimeter data indicate Ingenuity climbed to its prescribed maximum altitude of 10 feet (3 meters) and maintained a stable hover for 30 seconds. It then descended, touching back down on the surface of Mars after logging a total of 39.1 seconds of flight. Additional details on the test are expected in upcoming downlinks.


In this video captured by NASA’s Perseverance rover, the agency’s Ingenuity Mars Helicopter took the first powered, controlled flight on another planet on April 19, 2021.
Credits: NASA/JPL-Caltech/ASU/MSSS

Ingenuity’s initial flight demonstration was autonomous – piloted by onboard guidance, navigation, and control systems running algorithms developed by the team at JPL. Because data must be sent to and returned from the Red Planet over hundreds of millions of miles using orbiting satellites and NASA’s Deep Space Network, Ingenuity cannot be flown with a joystick, and its flight was not observable from Earth in real time.


NASA Associate Administrator for Science Thomas Zurbuchen announced the name for the Martian airfield on which the flight took place.


“Now, 117 years after the Wright brothers succeeded in making the first flight on our planet, NASA’s Ingenuity helicopter has succeeded in performing this amazing feat on another world,” Zurbuchen said. “While these two iconic moments in aviation history may be separated by time and 173 million miles of space, they now will forever be linked. As an homage to the two innovative bicycle makers from Dayton, this first of many airfields on other worlds will now be known as Wright Brothers Field, in recognition of the ingenuity and innovation that continue to propel exploration.”


Ingenuity’s chief pilot, Håvard Grip, announced that the International Civil Aviation Organization (ICAO) – the United Nations’ civil aviation agency – presented NASA and the Federal Aviation Administration with official ICAO designator IGY, call-sign INGENUITY.


These details will be included officially in the next edition of ICAO’s publication Designators for Aircraft Operating Agencies, Aeronautical Authorities and Services. The location of the flight has also been given the ceremonial location designation JZRO for Jezero Crater.


As one of NASA’s technology demonstration projects, the 19.3-inch-tall (49-centimeter-tall) Ingenuity Mars Helicopter contains no science instruments inside its tissue-box-size fuselage. Instead, the 4-pound (1.8-kg) rotorcraft is intended to demonstrate whether future exploration of the Red Planet could include an aerial perspective.


This first flight was full of unknowns. The Red Planet has a significantly lower gravity – one-third that of Earth’s – and an extremely thin atmosphere with only 1% the pressure at the surface compared to our planet. This means there are relatively few air molecules with which Ingenuity’s two 4-foot-wide (1.2-meter-wide) rotor blades can interact to achieve flight. The helicopter contains unique components, as well as off-the-shelf-commercial parts – many from the smartphone industry – that were tested in deep space for the first time with this mission.


“The Mars Helicopter project has gone from ‘blue sky’ feasibility study to workable engineering concept to achieving the first flight on another world in a little over six years,” said Michael Watkins, director of JPL. “That this project has achieved such a historic first is testimony to the innovation and doggedness of our team here at JPL, as well as at NASA’s Langley and Ames Research Centers, and our industry partners. It’s a shining example of the kind of technology push that thrives at JPL and fits well with NASA’s exploration goals.”


Parked about 211 feet (64.3 meters) away at Van Zyl Overlook during Ingenuity’s historic first flight, the Perseverance rover not only acted as a communications relay between the helicopter and Earth, but also chronicled the flight operations with its cameras. The pictures from the rover’s Mastcam-Z and Navcam imagers will provide additional data on the helicopter’s flight.   


“We have been thinking for so long about having our Wright brothers moment on Mars, and here it is,” said MiMi Aung, project manager of the Ingenuity Mars Helicopter at JPL. “We will take a moment to celebrate our success and then take a cue from Orville and Wilbur regarding what to do next. History shows they got back to work – to learn as much as they could about their new aircraft – and so will we.”


Perseverance touched down with Ingenuity attached to its belly on Feb. 18. Deployed to the surface of Jezero Crater on April 3, Ingenuity is currently on the 16th sol, or Martian day, of its 30-sol (31-Earth day) flight test window. Over the next three sols, the helicopter team will receive and analyze all data and imagery from the test and formulate a plan for the second experimental test flight, scheduled for no earlier than April 22. If the helicopter survives the second flight test, the Ingenuity team will consider how best to expand the flight profile.


More About Ingenuity


JPL, which built Ingenuity, also manages the technology demonstration project for NASA. It is supported by NASA’s Science, Aeronautics, and Space Technology mission directorates. The agency’s Ames Research Center in California’s Silicon Valley and Langley Research Center in Hampton, Virginia, provided significant flight performance analysis and technical assistance during Ingenuity’s development.


Dave Lavery is the program executive for the Ingenuity Mars Helicopter, MiMi Aung is the project manager, and Bob Balaram is chief engineer.


For more information about Ingenuity:




More About Perseverance


A key objective for Perseverance’s mission on Mars is astrobiology, including the search for signs of ancient microbial life. The rover will characterize the planet’s geology and past climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and cache Martian rock and regolith (broken rock and dust).


Subsequent NASA missions, in cooperation with ESA (European Space Agency), would send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for in-depth analysis.


JPL built and manages operations of the Perseverance rover. JPL is managed for NASA by Caltech in Pasadena, California.



Alana Johnson / Grey Hautaluoma
Headquarters, Washington
202-672-4780 / 202-358-0668 /

DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.

Last Updated: Apr 19, 2021
Editor: Karen Northon
5G as a wireless power grid


5G has been designed for blazing fast and low-latency communications. To do so, mm-wave frequencies were adopted and allowed unprecedently high radiated power densities by the FCC. Unknowingly, the architects of 5G have, thereby, created a wireless power grid capable of powering devices at ranges far exceeding the capabilities of any existing technologies. However, this potential could only be realized if a fundamental trade-off in wireless energy harvesting could be circumvented. Here, we propose a solution that breaks the usual paradigm, imprisoned in the trade-off between rectenna angular coverage and turn-on sensitivity. The concept relies on the implementation of a Rotman lens between the antennas and the rectifiers. The printed, flexible mm-wave lens allows robust and bending-resilient operation over more than 20 GHz of gain and angular bandwidths. Antenna sub-arrays, rectifiers and DC combiners are then added to the structure to demonstrate its combination of large angular coverage and turn-on sensitivity—in both planar and bent conditions—and a harvesting ability up to a distance of 2.83 m in its current configuration and exceeding 180 m using state-of-the-art rectifiers enabling the harvesting of several μW of DC power (around 6 μW at 180 m with 75 dBm EIRP).


Our era is witnessing a rapid development in the field of millimeter-wave (mm-wave) and Internet of Things (IoT) technologies with a projected 40 billion IoT devices to be installed by 20251. This could result in a huge number of batteries needing to be continuously charged and replaced. The design and realization of energy-autonomous, self-powered systems: the perpetual IoT, is therefore highly desirable. One potential way of satisfying these goals is through electromagnetic energy harvesting. A powerful source for electromagnetic scavenging is mm-wave energy, present in the fifth-generation (5G) of mobile communications bands (above 24 GHz), where the limits of allowable transmitted Effective Isotropic Radiated Power (EIRP) by the Federal Communications Commission (FCC) regulations are pushed beyond (reaches 75 dBm) that of their lower-frequency counterparts. Following the path loss model defined by the 3rd Generation Partnership Project Technical Report 3GPP TR 38.901 (release 16) in outdoor Urban Macro Line of Sight conditions (UMa LOS), the power density expected to be received at 28 GHz for a transmitted power of 75 dBm EIRP is 28 μW cm−2 at a distance of 100 m away from the transmitter. This demonstrates the ability of 5G to create a usable network of wireless power. In addition to the advantage of high transmitted power available at 5G, moving to mm-wave bands allows the realization of modular antennas arrays instead of single elements, thereby allowing a fine scaling of their antenna aperture, which can more than compensate for the high path loss at these frequencies through the addition of extremely-large gains2. However, one limitation accompanies large gain antennas: their inability to provide a large angular coverage. As the relative orientations of the sources and harvesters are generally unknown, the use of large aperture mm-wave harvesters may seem limiting and impossible. Individual rectennas, constituted of small antenna elements, can realistically be DC combined. However, this approach does not increase the turn-on sensitivity (lowest turn-on power) of the overall rectenna system: RF combination is needed.

Beamforming networks (BFNs) are used to effectively create simultaneous beam angular coverage with large-gain arrays, by mapping a set of directions to a set of feeding ports. An important class of these multiple networks is the microwave passive BFN that has been widely used in switched-beam antenna systems and applications. Hybrid combination techniques, based on Butler matrix networks, have been used in previous works for energy harvesting at lower frequencies3,4,—more specifically at 2.45 GHz—to achieve wider angular coverage harvesting. However, these Ultra-High Frequency (UHF) arrays are impractically large for IoT applications and the implementation of their Butler matrices at higher frequencies would necessitate costly high-resolution fabrication. While sub-optimal—because of its large size—in the UHF band, the Rotman lens becomes the BFN of choice in the realm of mm-wave energy harvesting. Compared to their lower frequencies counterpart, fewer implementations are presented in the literature targeting energy harvesting at higher frequencies, more specifically 24 GHz and above. However, these systems later displayed in the table of comparison5,6,7, suffer from a narrow angular coverage.

In this paper, the authors demonstrate a full implementation of an entirely flexible, bending-resilient and simultaneously high gain and large angular coverage system for 5G/mm-wave energy harvesting based on a Rotman lens. For IoT applications, there is a benefit to making extremely low-profile devices that can conformally fit onto any surface in the environment such as walls, bodies, vehicles, etc. Therefore, thanks to the use of mm-waves, antennas with such features can be readily designed and fabricated. A Rotman lens-based rectenna has been first proposed in8, where a preliminary prototype and approach were presented, resulting in a quasi-flexible system, 80° angular coverage and 21-fold increase in the harvested power compared to a non-Rotman-based system. Here, the previously-predicted potential of 5G-powered nodes for the IoT and long-range passive mm-wave Radio Frequency IDentification (RFID) devices, is further taken advantage of, and effectively demonstrated. In order to do so, a thorough analysis of the lens itself—a structure that was not revealed in8—is first presented, exposing its key design parameters and resulting measured broadband behavior tested in both planar and bent conditions over more than 20 GHz of bandwidth. In addition, a scalability study of the approach, outlining the optimal size of such a system is reported, thereby proving the extent of the capability of providing a combination of good array factor and wide beam coverage. The novelty of this system also lies in the realization of a fully-flexible 28 GHz Rotman-lens-based rectenna system, completed by the design of a new DC combiner on a flexible 125 μm-thin polyimide Kapton substrate. The new DC combiner uses a reduced number of bypass diodes and increases the angular coverage of the system by more than 30% compared to8. Furthermore, the frequency-broadband behavior enabled by the use of the Rotman lens makes the full rectenna system bending-resilient, a property now demonstrated through its characterizations in flexing and conformally-mounted configurations. Finally, the system’s potential for long-range mm-wave harvesting is expressed for the first time, by reporting an unprecedented harvesting range of 2.83 m.

Experiments, results and discussions

Rotman lens scalability study for harvesting applications

The Rotman lens, introduced in the 1960s, constitutes one of the most common and cost-effective designs for BFNs and is commonly utilized to enable multibeam phased array system9 and wide-band operation, thanks to its implementation of true-time-delays10. By properly tuning the shape of the lens according to the geometrical optics approximation with the goal of focalizing plane waves impinging on the antenna side of the lens to different focal points on the beam-ports side of the lens, one achieves a lens-shaped structure with two angles of curvatures: one on the beam-ports side, and the other on the antenna side11. Because the lens is capable of focusing the energy coming from a given direction into its geometrically-associated beam port, the proposed scheme loads each of these ports with a rectifier, thereby channeling the energy coming from any direction to one of the rectifiers as shown in Fig. 1a. This subsection investigates the effect of varying the number of antenna ports Na and beam ports Nb in the Rotman lens on its maximum array factor and angular coverage. The (NaNb) set, resulting in the best combination, will define the Rotman lens design parameters used for this work. Structures of varying sizes were designed using Antenna Magus and identical material parameters (substrate, conductors) as the ones of the presented design, before being simulated in CST STUDIO SUITE 2018. The simulated data was then processed in MATLAB to output the array factors created by the respective lens structures using a modified version of Eq. (1)12, presented next in Eq. (2):


where AFnNakdθθ and ββ are, respectively, the lossless array factor, the antenna number, the total number of antenna ports, the wave vector, the spacing between the elements, the direction of radiation and the difference in phase excitation between the elements. Since this formula describes a lossless array with a single antenna port, we introduced the following equation that takes into account the losses induced by the feeding network as well as the introduction of multiple feeding ports.


where AFjAFj and SnjSnj are, respectively, the array factor for beam port j and the S parameters between antenna ports n and beam ports j. The maximum value of the array factors as well as their total (accounting for the aggregated coverage of all ports) 3 dB beamwidths where then tabulated. The five simulated lenses had the following (NaNb) combinations: (4,3), (8,6) representing the system implemented in this work, (16,12), (32,24) and (64,48). Figure 1b shows the increase in the array factor until reaching a peak of around 7.8 dB for a lens surrounded by 16 antennas and 12 beam ports, after which the array factor starts dropping, down to approximately 5.2 dB for a 64 antennas structure with 48 beam ports. The array factor reduction is explained by the increased losses within the lens accompanied by the increase of complexity and internal reflections, as the lens grows in electrical size. The same plot shows the decrease in angular coverage from 180° with 4 antennas down to 80° with 64 antennas. This study shows that the combination composed of eight antennas and six beam ports, offers a nearly optimal compromise, with these materials, between a high array factor of 5.95 dB and a 120° total angular coverage, while maintaining a reasonable number of antennas and beam ports. It should be noted that the choice of the number of beam ports is related to the 3dB-beamwidth of the individual antennas, the reason for which will be detailed later.

Figure 1

(a) Dual combining (RF + DC) enabled by the use of the Rotman lens between the antennas and the rectifiers, (b) plot of the simulated maximum array factors and angular coverages for different-size Rotman lenses and (c) picture of the fabricated Rotman lens structure.

Flexible broadband Rotman lens design

After setting the number of antenna ports and beam ports, the design was printed on flexible copper-clad Liquid Crystal Polymer (LCP) substrate (εr=3.02εr=3.02 and h=180μmh=180μm) using an inkjet-printed masking technique followed by etching, resulting in the structure shown in Fig. 1c. It should be noted that the use of impedance-matched dummy ports is common with Rotman lenses13,14,15,16. Nevertheless, the goal in the implementation hereby described is not (as is usually the case) the generation of clean beam patterns with low side-lobe levels. Here, the lens’ properties are used for harvesting. Consequently, as long as the presence of the side lobes does not significantly interfere with the level of the array factor at broadside, side lobes are of no concern. Such a structure, including eight antenna ports and six beam ports—and, therefore, six radiating directions—was designed, simulated, and tuned. The structure, shown in Fig. 1c, with the antenna ports connected to matched loads, was then tested in planar and bent configurations—cylinders with different bending radii ranging from 1.5 to 2.5 in. radii—to assess the effect of bending on the S parameters behavior. Figure 2a shows the measured reflection coefficient of the Rotman lens at beam port 4 for four different scenarios, in comparison with the simulated structure in a planar position. The results reveal the Rotman lens’ ability to be mounted on curved surfaces down to a radius R = 1.5″, while maintaining a stable matching and minuscule losses compared to being held in a planar position.

Figure 2

(a) Plot of the simulated and measured reflection coefficients at beam port 4 under planar and bent conditions and (b) Plots of the maximum array factors and angular directions of beam ports P1, P3 and P5 with respect to frequency.

The gain and angular bandwidths of this structure—defined by the frequency range in which the maximum array factor and angular direction per beam are stable within 3 dB and 5° respectively,—are studied next. The ultimate assessment of these properties involves calculating the beams’ magnitude and angular directions over a wide range of frequencies17, in order to ascertain their stability or lack thereof. For this purpose, the maximum array factors were calculated and the beams’ angular directions were extracted and plotted in Fig. 2b for the first, third and fifth beam ports, P1, P3 and P5, representing the edge, secondary and central beams in this symmetrical structure. These plots prove the unique capabilities offered by the Rotman lens; although the Rotman lens is designed at a specific frequency—28 GHz in this work—this analysis proves that both the magnitude and the angular direction of the beams remain relatively stable over a very wide frequency range. In Fig. 2b, three plots refer to the maximum array factors of the three beam ports, where minor fluctuations between 4 and 7 dB are observed over the range from 10 to 43 GHz for ports P3 and P5 and similar fluctuations over a fairly reduced frequency range for the extreme edge beam P1. On the same graph, three plots present the angular direction’s stability of P1, P3 and P5 beams, where P3 (in particular) preserves its angular direction over 33 GHz of bandwidth. The lens’ angular coverage resides between ports 1 and 6 and can be extracted from Fig. 2b. Knowing that the structure is symmetrical and that beam port P1 is at around 54−54∘, the overall structure covers an angle larger than 100° in front of the lens, a result further detailed in the next subsection. It should be noted that such a beamwidth is maintained over a large angular bandwidth exceeding 20 GHz, as shown in Fig. 2b. This study demonstrates the stability and robustness of a low-cost, printed and flexible mm-wave Rotman lens structure, tested with respect to bending and frequency, and supports the choice of such an architecture at the heart of the harvesting system proposed in this work.

Flexible, high-gain and wide-angular-coverage mm-wave Rotman-lens-based antenna array

Eight of the linear antenna sub-arrays introduced in8 were then added to the antenna ports of the array, and its beam-ports were extended by microstrip lines to enable their connection to end-launch 2.92μm2.92μm connectors. The antenna sub-array consists of five serially-fed patch antenna elements, providing an operation centered at 28.55 GHz with a reflection coefficient S11S11 lower than 20−20 dB within this range. Their E-plane beamwidth of about 1818∘ (provided by the five antennas) is appropriate for most use cases, where environments expand mostly horizontally. Its simulations showed a gain of 13 dBi and a H-plane beamwidth of 80° in the plane perpendicular to the linear array. In this configuration, six beams were chosen to intersect at angles providing 3dB lower gain than broadside. Eight antennas provide a 3dB-beamwidth of 15°, which covers a total of 6×18=1086×18∘=108∘ in front of the array. The design was then also printed on flexible LCP substrate, resulting in the structure shown in Fig. 3a, mounted on a 1.5″ radius cylinder. The radiation properties of the lens-based antenna system were simulated using the time-domain solver of CST STUDIO SUITE 2018, resulting in the six gain plots shown in Fig. 3b. The gain of the Rotman lens at every port was also accurately measured using a 20 dBi transmitter horn antenna and by terminating all five remaining ports with a 50Ω50Ω load for every port measurement to guarantee the proper operation of the lens. Both simulated and measured radiation patterns (shown in Fig. 3b) display a remarkable similarity with a measured gain of approximately 17 dBi, and an angular coverage of around 110°, thereby validating the operation of the antenna array. The gains on the first three ports were also measured for the bent structure over a curvature of 1.5″ radius, shown in Fig. 3a and compared to the measured results on a planar surface. The previous subsection in addition to previous works18,19 have demonstrated that the performance of the Rotman lens is not deteriorated by wrapping or folding the structure compared to its conventional planar counterpart. However, after adding the antenna arrays, bending the structure can indeed have effects on its phase response, especially if the structure is large and the bending is severe. Figure 3c shows the gains of P1, P2 and P3 for the two scenarios (three ports only because the structure is symmetrical), demonstrating again the ability of the lens in maintaining a stable gain (especially over the center beams) upon bending. The beam located at the edge, however, suffers additional deterioration in received power under bending, because of the shift of the source away from the broadside of the bent antenna arrays.

Figure 3

(a) Picture of the flexible Rotman-lens-based antenna array, (b) measured (solid lines) and simulated (dashed lines) gains of the antenna array held in a planar position and (c) measured gains of the antenna array for beams P1, P2 and P3 only (because of the symmetry of the structure) in planar and bent conditions.

Fully-flexible 28 GHz Rotman lens-based system

Rotman-lens-based rectenna

In this section, the fully-flexible rectenna system—based on the Rotman lens and a new DC combiner network—is presented. This architecture, shown in Fig. 4a, consists of a series of eight antenna sub-arrays attached to the Rotman lens from one side, facing six rectifiers at the opposite side where DC serial combination is implemented. The basic rectenna elements, that are the antenna and the rectifier, are presented in details in8. The diode used in this work is the MA4E2038 Schottky barrier diode from Macom. The Rotman-based rectenna was first characterized as a function of its received power density. The system was positioned at a specific harvesting angle (approximately 25−25∘) and illuminated with a horn antenna with a gain of 20 dBi, placed at a distance of 52 cm away from the rectenna array, within the far field region starting at 23 cm, and outputting powers ranging from 18 to 25 dBm, corresponding to an RF input power sweep from around − 9 dBm to − 2 dBm. The array was loaded with its optimal load impedance of 1 kΩ, corresponding to the optimal load of a single rectifier—since only one rectifier will be “ON” at a time, given that the Rotman lens focalizes all the power to one beam port depending on the direction of the incoming wave—as detailed earlier. The results of this experiment are shown in Fig. 4b, where the harvested voltages and powers of the array are shown. It can be observed that, at low powers, the Rotman-based rectenna effortlessly produces an output. The Rotman-based rectenna turns on well below − 6 dBm cm−2, which compares quite favorably to the literature6. The output voltage of the rectenna was also measured over its operating frequency range. Like in the first experiment, the system was positioned at the same harvesting angle, at a range of 25 cm away from the source’s horn antenna. The output voltages under open load conditions were recorded and plotted, as shown in Fig. 4c for the Rotman lens-based rectenna, for Pd=9dBm cm2Pd=9dBm cm−2Pd=10.5dBm cm2Pd=10.5dBm cm−2 and Pd=12dBm cm2Pd=12dBm cm−2 incident power densities. The plots present a wide frequency coverage—from 27.8 to 29.6 GHz.

Figure 4

(a) Picture of the fully-flexible Rotman-based rectenna, (b) plot of the measured voltages and output powers versus incident power density for the Rotman-based rectenna and (c) plot of the measured voltages with respect to frequency for the Rotman-based rectenna.

Flexible DC combining network

Power summation is very critical when it comes to the unbalanced rectification outputs produced from realistic RF sources, and can be implemented differently depending on its costs and benefits20.

This paper does not rely on a direct voltage summation topology (i.e. back-to-back RF diodes); however, it introduces a minimalist architecture relying on a total of 2×(N1)2×(N−1) bypass diodes, where N is the number of RF or rectifying diodes. Equipped with a low turn-on voltage of 0.1 V, the Toshiba 1SS384TE85LF bypass diodes used in the DC combiner design create a low resistance current path around all other rectifiers that received very low or close to zero RF power. This topology is optimal when only one diode is turned on, which can be assumed if a single, dominant source of power irradiates this particular design from a given direction. This new combiner circuit is shown in the schematic of Fig. 5a. This simplified schematic—shown for four rectifying diodes—uses different colors to highlight the paths that the current will take for every case where an RF diode turning “ON” while the serially-connected diodes are “OFF”. This DC combiner was then fabricated on a flexible 125μm125μm-thin polyimide Kapton substrate and connected to the Rotman lens-based rectenna through a series of single connectors to make the entire system fully flexible and bendable. The harvested power under a load of 1 kΩ versus the angle of incidence of the mm-wave energy source for the Rotman-lens-based rectenna is compared for both rigid (presented in8, and relying on 2×N2×N bypass diodes) and flexible new DC combiners. For this experiment, a horn transmitter antenna was used to send 25 dBm of RF power at 28.5 GHz to the lens placed 70 cm away, as shown in Fig. 5b, while the array was precisely rotated in angular increments of 5°. Figure 6a shows that the new DC combiner, with a reduced number of diodes, was able to provide a complete angular coverage of almost 110° over the entire lens spectrum as presented in Fig. 3b, thus solving the voltage nulling occurring at the first and last ports, using the rigid DC combiner adopted previously in8. The new DC combiner offers therefore, an increase of more than 30% in the system’s spatial angular in addition to enabling a fully-bendable structure due to the unique fabrication on flexible Kapton substrate and connection to the rectenna using individual interconnects.

Figure 5

(a) Rotman-based rectenna power summation network and (b) picture of the setup used to measure the angular response of the rectenna.

Figure 6

(a) Plot of the measured harvested powers by the rectenna with respect to the source’s incidence angle for the two DC combiners, rigid and flexible and (b) plots of the measured harvested powers and voltages with respect to the incident power density under different load conditions for the Rotman lens rectenna with and without the flexible DC combiner.

As mentioned earlier, the DC combiner is mainly used with the Rotman-lens-based rectenna to automatically direct the active rectifier’s output to a single DC common port, independent of which port this might be. An alternative to the DC combiner in the Rotman lens-based system, would be to manually connect to the active port if the location of the source were known. To study the effect of the implemented DC combiner on the turn-on sensitivity of the system, the output voltage of the rectenna was measured for a specific source location with and without the combiner over a range of RF transmitted power and load variations; the direction was chosen such that the non-DC-combined rectifier would output its maximum power. Figure 6b shows eight different plots where three of them represent the harvested power with a direct connection to the active rectifier for 1 kΩ, 10 kΩ and 100 kΩ conditions. Plotted with the same colors are the other three, representing the harvested power with the addition of the DC combiner for the same load values. The last two plots display the measured voltages with and without the combiner under open load conditions. The rectenna was placed 61 cm away from the transmitter horn antenna and the power was swept from 10 to 25 dBm. The results show the performance superiority in all considered load conditions when the contact is made directly to the rectifier and not through the DC combiner. The lens-based system is able to achieve a turn-on power as low as 15dBm cm2−15dBm cm−2 in this case. This behavior is explained by the voltage drop introduced by the bypass diodes present in the combiner—that consistently decrease the expected output voltage by 0.1 to 0.2 V—when one or two diodes are, respectively, added to the current path. The variation of load values also shows that the rectenna can achieve better efficiencies at lower loads. More importantly, the reduction in the turn-on sensitivity—the minimum power density required output 10 mV—induced by the combiner is only of about 2 dB in loaded conditions, while the combiner enables an increase in the angular coverage of the rectenna system from about 18° to 110°. The remarkable angular and high-power turn-on sensitivity offered by the Rotman-lens-based rectenna are finally benchmarked using the following table for comparison with several state-of-the-art works, as presented in literature. In Table 1, the striking performance of the proposed system is displayed, highlighted by its flexibility and ability of achieving an angular coverage as large as 110° at extremely high turn-on sensitivity, thereby allowing mm-wave long-range harvesting in ad-hoc and conformal-mounting implementations.

Table 1 Performance comparison.

Rectenna system performance under bending

This section displays the operation of the Rotman-lens-based system under different bending scenarios. This and previous work18,19 show that the lens is able to maintain an efficient electromagnetic energy distribution across the output ports under convex and concave flexing conditions. The lens-based rectenna was placed on cylinders with different curvatures, 70 cm away from the transmitter sending 25 dBm of power at 28.5 GHz, as shown on Fig. 7a. The voltage was collected using a load of 1 kΩ for the planar and three bent conditions and plotted in Fig. 7b with respect to the source’s angle of incidence. The graph shows an unprecedented consistency and stability in the system’s scavenging and rectification abilities, knowing that several sub-systems are exposed to warping and the pressures of bending: the antenna sub-arrays, the Rotman lens and the rectifiers. Slight attenuation can be observed at the edges, but the system otherwise performs unimpeded by the bending. This remarkable property qualifies this system as a perfect candidate for use in wearables, smart phones and ubiquitous, conformal 5G energy harvesters for IoT nodes.

Figure 7

(a) Picture of the flexible Rotman lens-based rectenna placed on a 1.5″ radius cylinder and (b) measured harvested powers versus incidence angles for different curvatures, (c) long-range harvesting testing setup.

Long-range harvesting

As described earlier, one of the main appeals of the proposed approach is its ability to use the high EIRPs allowed for 5G base-stations while guaranteeing an extended beam angular coverage, which is a necessary feature for ad-hoc ubiquitous harvesting implementations. In order to demonstrate the lens based-rectenna for longer-distance harvesting and detect that maximum range, a high-performance antenna system—comprised of a 19 dBi conical horn antenna and a 300 mm-diameter PTFE dielectric lens (for high directivity) providing an additional 10 dB of gain—was used as shown in Fig. 7c. With a transmitted power of 25 dBm (and an associated EIRP of approximately 54 dBm), corresponding to an incident power density of approximately − 6 dBm cm−2, the lens-based rectenna displayed an extended range of 2.83 m under open load conditions, with an output voltage around 10 mV, thereby demonstrating (to our knowledge) the longest-ranging rectenna demonstration at mm-wave frequencies. With a transmitter emitting the allowable 75 dBm EIRP, the theoretical maximum reading range of this rectenna could extend to 16 m. In addition, the use of advanced diodes—designed for applications within the 5G bands and enabling rectifiers’ sensitivities similar to that common at lower (UHF) frequencies—are showing a potential path towards achieving a turn-on sensitivity of the rectifiers as low as − 30 dBm21,22. If this were practically applied to the Rotman lens system presented in this work, the harvesting range could be extended beyond 180 m (where the received power density for a transmitted power of 75 dBm is 7.8μW cm27.8μW cm−2), which is only slightly smaller than the recommended cell size of 5G networks23. This observation enables the striking idea that future 5G networks could be used not only for tremendously-rapid communications, but also as a ubiquitous wireless power grid for IoT devices.


Through the use of the Rotman lens, this paper demonstrates that the usual paradigm constrained by the (often considered fundamental) trade-off between the angular coverage and the turn-on sensitivity of a wireless harvesting system can be broken. Using the reported architecture, one can design and fabricate flexible mm-wave harvesters that can cover wide areas of space while being electrically large and benefit from the associated improvements in link budget (from source to harvester) and, more importantly, turn-on sensitivity. The approach has been shown, however, to only be scalable up to the degree where the additional incremental losses introduced by the growing lens counterbalance the increase in the aperture of the rectenna. Nevertheless, this inflection point only appears (in the particular context considered in this paper) after the arraying of 16 elements, or up to a scale of 8λ. In the 5G Frequency Range 2 (FR2), this translates to harvesters of 4.5 cm to 9.6 cm in size, which are perfectly suited for wearable and ubiquitous IoT implementations. With the advent of 5G networks and their associated high allowed EIRPs and the availability of diodes with high turn-on sensitivities at 5G frequencies, several μWμW of DC power (around 6 μWμW with 75 dBm EIRP) can be harvested at 180 m. Such properties may trigger the emergence of 5G-powered nodes for the IoT and, combined with the long-range capabilities of mm-wave ultra-low-power backscatterers24, of long-range passive mm-wave RFIDs.


  1. 1.

    Mercer, D. Global Connected and IoT Device Forecast Update (2019).

  2. 2.

    Hester, J. G. D. & Tentzeris, M. M. Inkjet-printed flexible mm-wave Van-Atta reflectarrays: A solution for ultra-long-range dense multi-tag and multi-sensing chipless RFID implementations for IoT smart skins. IEEE Trans. Microw. Theory Tech. 57, 1303–1309 (2017).

    Google Scholar 

  3. 3.

    Lee, D.-J., Lee, S.-J., Hwang, I.-J., Lee, W.-S. & Yu, J.-W. Hybrid power combining rectenna array for wide incident angle coverage in RF energy transfer. IEEE Trans. Microw. Theory Tech. 65, 3409–3418 (2017).

    ADS Article Google Scholar 

  4. 4.

    Kuek, J. et al. A compact butler matrix for wireless power transfer to aid electromagnetic energy harvesting for sensors. In 2017 IEEE Asia Pacific Microwave Conference (APMC) 334–336 (2017).

  5. 5.

    Bito, J. et al. Millimeter-wave ink-jet printed RF energy harvester for next generation flexible electronics. In 2017 IEEE Wireless Power Transfer Conference (WPTC) 1–4 (2017).

  6. 6.

    Ladan, S., Guntupalli, A. B. & Wu, K. A high-efficiency 24 GHz rectenna development towards millimeter-wave energy harvesting and wireless power transmission. IEEE Trans. Circuits Syst. I Regul. Pap. 61, 3358–3366 (2014).

    Article Google Scholar 

  7. 7.

    Okba, A., Takacs, A., Aubert, H., Charlot, S. & Calmon, P.-F. Multiband rectenna for microwave applications. C. R. Phys. 18, 107–117 (2017).

    ADS CAS Article Google Scholar 

  8. 8.

    Eid, A., Hester, J. & Tentzeris, M. M. A scalable high-gain and large-beamwidth mm-wave harvesting approach for 5g-powered IoT. In 2019 IEEE MTT-S International Microwave Symposium (IMS) 1309–1312 (2019).

  9. 9.

    Wang, K., Gu, J.-F., Ren, F. & Wu, K. A multitarget active backscattering 2-d positioning system with superresolution time series post-processing technique. IEEE Trans. Microw. Theory Tech. 65, 1751–1766 (2017).

    ADS Article Google Scholar 

  10. 10.

    Rotman, R., Tur, M. & Yaron, L. True time delay in phased arrays. Proc. IEEE 104, 504–518 (2016).

    Article Google Scholar 

  11. 11.

    Rotman, W. & Turner, R. Wide-angle microwave lens for line source applications. IEEE Trans. Antennas Propag. 11, 623–632 (1963).

    ADS Article Google Scholar 

  12. 12.

    Balanis, C. A. Antenna Theory: Analysis and Design (Wiley, New York, 2016).

    Google Scholar 

  13. 13.

    Attaran, A., Rashidzadeh, R. & Kouki, A. 60 GHz low phase error rotman lens combined with wideband microstrip antenna array using LTCC technology. IEEE Trans. Antennas Propag. 64, 5172–5180 (2016).

    ADS Article Google Scholar 

  14. 14.

    Hassanien, M. A., Hahnel, R. & Plettemeier, D. Wideband rotman lens beamforming technique for 5g wireless applications. In 2019 2nd International Conference on Computer Applications and Information Security (ICCAIS) 1–5 (2019).

  15. 15.

    Tekkouk, K., Ettorre, M. & Sauleau, R. SIW rotman lens antenna with ridged delay lines and reduced footprint. IEEE Trans. Microw. Theory Tech. 66, 3136–3144 (2018).

    ADS Article Google Scholar 

  16. 16.

    Jastram, N. & Filipovic, D. S. Design of a wideband millimeter wave micromachined rotman lens. IEEE Trans. Antennas Propag. 63, 2790–2796 (2015).

    ADS MathSciNet Article Google Scholar 

  17. 17.

    Darvazehban, A., Manoochehri, O., Salari, M. A., Dehkhoda, P. & Tavakoli, A. Ultra-wideband scanning antenna array with rotman lens. IEEE Trans. Microw. Theory Tech. 65, 3435–3442 (2017).

    ADS Article Google Scholar 

  18. 18.

    Rahimian, A., Alfadhl, Y. & Alomainy, A. Design and performance of a flexible 60-GHz rotman lens-based array beamformer. In 12th European Conference on Antennas and Propagation (EuCAP 2018) 1–2 (2018).

  19. 19.

    Vo Dai, T. K. & Kilic, O. Compact rotman lens structure configurations to support millimeter wave devices. Prog. Electromag. Res. B 71, 91–106 (2016).

    Article Google Scholar 

  20. 20.

    Parks, A. N. & Smith, J. R. Active power summation for efficient multiband RF energy harvesting. In 2015 IEEE MTT-S International Microwave Symposium (IMS) 1–4 (2015).

  21. 21.

    Eid, A., Hester, J., Tehrani, B. & Tentzeris, M. Flexible w-band rectifiers for 5g-powered IoT autonomous modules. In 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting 1163–1164 (2019).

  22. 22.

    Gao, H., Leenaerts, D. M. & Baltus, P. A 58-64 GHz transformer-based differential rectifier in 40 nm CMOS with-12 dBm sensitivity for 1 V at 64 GHz. In 2019 IEEE MTT-S International Microwave Symposium (IMS) 1306–1308 (2019).

  23. 23.

    Sulyman, A. I. et al. Radio propagation path loss models for 5g cellular networks in the 28 GHz and 38 GHz millimeter-wave bands. IEEE Commun. Mag. 52, 78–86 (2014).

    Article Google Scholar 

  24. 24.

    Hester, J. G. & Tentzeris, M. M. A mm-wave ultra-long-range energy-autonomous printed RFID-enabled van-Atta wireless sensor: At the crossroads of 5g and IoT. In 2017 IEEE MTT-S International Microwave Symposium (IMS) 1557–1560 (2017).

Download references


This work was supported by the Air Force Research Laboratory and the NSF-EFRI. The work was performed in part at the Georgia Tech Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (Grant ECCS-1542174).

Author information



A.E. and J.H. conceived the idea, designed, and simulated the antenna arrays, rectifiers, Rotman lens, DC combiners and full rectennas. They also performed the measurements, interpreted results and wrote the paper. M.T. supervised the research and contributed to the general concept and interpretation of the results. All authors reviewed the manuscript.

Corresponding author

Correspondence to Aline Eid.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Eid, A., Hester, J.G.D. & Tentzeris, M.M. 5G as a wireless power grid. Sci Rep 11, 636 (2021).

Download citation

Share this article

Anyone you share the following link with will be able to read this content:

Provided by the Springer Nature SharedIt content-sharing initiative


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Rotman Lens-based ‘Rectenna’ Capable of Millimeter-wave Harvesting

Leveraging the 5G Network to Wirelessly Power IoT Devices

Rotman Lens-based ‘Rectenna’ Capable of Millimeter-wave Harvesting at 28-GHz With High Efficiency From All Directions for First Time

No more device batteries? Researchers at Georgia Institute of Technology’s ATHENA lab discuss an innovative way to tap into the over-capacity of 5G networks, turning them into “a wireless power grid” for powering Internet of Things (IoT) devices. The breakthrough leverages a Rotman lens-based rectifying antenna capable of millimeter-wave harvesting at 28 GHz. The innovation could help eliminate the world’s reliance on batteries for charging devices by providing an alternative using excess 5G capacity.


Researchers at the Georgia Institute of Technology have uncovered an innovative way to tap into the over-capacity of 5G networks, turning them into “a wireless power grid” for powering Internet of Things (IoT) devices that today need batteries to operate. 

The Georgia Tech inventors have developed a flexible Rotman lens-based rectifying antenna (rectenna) system capable, for the first time, of millimeter-wave harvesting in the 28-GHz band. (The Rotman lens is key for beamforming networks and is frequently used in radar surveillance systems to see targets in multiple directions without physically moving the antenna system.)

But to harvest enough power to supply low-power devices at long ranges, large aperture antennas are required. The problem with large antennas is they have a narrowing field of view. This limitation prevents their operation if the antenna is widely dispersed from a 5G base station. 

“We’ve solved the problem of only being able to look from one direction with a system that has a wide angle of coverage,” said senior researcher Aline Eid in the ATHENA lab, established in Georgia Tech’s School of Electrical and Computer Engineering to advance and develop novel technologies for electromagnetic, wireless, RF, millimeter-wave, and sub-terahertz applications. 

The findings were reported in the Jan.12 issue of the journal Scientific Reports.

The FCC has authorized 5G to focalize power much more densely compared with  previous generations of cellular networks. While today’s 5G was built for high-bandwidth communication, the high-frequency network holds rich opportunity to “harvest” unused power that would otherwise be wasted. 

Tapping Into 5G High-frequency Power  

“With this innovation, we can have a large antenna, which works at higher frequencies and can receive power from any direction. It’s direction-agnostic, which makes it a lot more practical,” noted Jimmy Hester, senior lab advisor and the CTO and co-founder of Atheraxon, a Georgia Tech spinoff developing 5G radio-frequency identification (RFID) technology.  

With the Georgia Tech solution, all the electromagnetic energy collected by the antenna arrays from one direction is combined and fed into a single rectifier, which maximizes its efficiency.  

“People have attempted to do energy harvesting at high frequencies like 24 or 35 Gigahertz before,” Eid said, but such antennas only worked if they had line of sight to the 5G base station; there was no way to increase their angle of coverage until now.

Operating just like an optical lens, the Rotman lens provides six fields of view simultaneously in a pattern shaped like a spider. Tuning the shape of the lens results in a structure with one angle of curvature on the beam-port side and another on the antenna side. This enables the structure to map a set of selected radiation directions to an associated set of beam-ports. The lens is then used as an intermediate component between the receiving antennas and the rectifiers for 5G energy harvesting. 

This novel approach addresses the tradeoff between rectenna angular coverage and turn-on sensitivity with a structure that merges unique radio frequency (RF) and direct current (DC) combination techniques, thereby enabling a system with both high gain and large beamwidth.

In demonstrations, Georgia Tech’s technology achieved a 21-fold increase in harvested power compared with a referenced counterpart, while maintaining identical angular coverage. 

This robust system may open the door for new passive, long-range, mm-wave 5G-powered RFID for wearable and ubiquitous IoT applications. The researchers used inhouse additive manufacturing to print the palm-sized mm-wave harvesters on a multitude of everyday flexible and rigid substrates. Providing 3D and inkjet printing options will make the system more affordable and accessible to a broad range of users, platforms, frequencies, and applications. 

Replacing Batteries With Over-the-air Charging 

“The fact is 5G is going to be everywhere, especially in urban areas. You can replace millions, or tens of millions, of batteries of wireless sensors, especially for smart city and smart agricultural applications,” said Emmanouil (Manos)Tentzeris, Ken Byers Professor in Flexible Electronics in the School of Electrical and Computer Engineering

Tentzeris predicts that power as a service will be the next big application for the telecom industry, just as data overtook voice services as a major revenue producer. 
The research team is most excited by the prospect of service providers embracing this technology to offer power on demand “over the air,” eliminating the need for batteries.

“I’ve been working on energy harvesting conventionally for at least six years, and for most of this time it didn’t seem like there was a key to make energy harvesting work in the real world, because of FCC limits on power emission and focalization,” Hester said. “With the advent of 5G networks, this could actually work and we’ve demonstrated it. That’s extremely exciting — we could get rid of batteries.”
This work was supported by the Air Force Research Laboratory and the National Science Foundation (NSF) – Emerging Frontiers in Research and Innovation program. The work was performed in part at the Georgia Tech Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the NSF (Grant ECCS-1542174).

CITATION: A. Eid, et al., “5G as a wireless power grid.” (Scientific Reports, 2021)

‘Rectenna’ Harvests Power From 5G Network


This is how scientists can leverage 5G networks to wirelessly power devices.

In a world-first, a team of researchers at the Georgia Institute of Technology has developed a small, 3D-printed rectifying antenna that can harvest electromagnetic energy from 5G signals and use it to power devices, in a way turning 5G networks into “a wireless power grid,” according to a press release by the university.

As explained in the Jan.12 issue of the journal Scientific Reports, the flexible Rotman lens-based rectifying antenna, in other words, rectenna, system can perform millimeter-wave harvesting in the 28-GHz band.

A 21-fold increase in harvesting power

Commonly used in radar surveillance systems to see multiple directions without moving the antenna system, the Rotman lens is especially important for beamforming networks. However, larger antennas, which unfortunately have a narrowing field of view, are needed to harvest enough power to supply devices, and this limits the usage.

The researchers solved this problem by using a system that has a wide angle of coverage. The Rotman lens provides 6 levels of view at the same time in a pattern shaped like a spider. By enabling this structure to map a set of selected radiation directions to an associated set of beam-ports, the lens is used as an intermediate component between the antennas and the rectifiers.

This way, the electromagnetic energy collected by the antenna arrays from one direction is combined and fed into a single rectifier. This maximizes efficiency, enabling a system with both high gain and large beamwidth.

The system achieved a 21-fold increase in harvested power compared with a referenced counterpart in demonstrations. It was also able to maintain identical angular coverage.


The researchers used 3D printers to develop the playing card-sized mm-wave harvesters on numerous substrates that are both flexible or rigid.

This new system could enable technologies where 5G acts like “a wireless power grid” for wearable and IoT applications everywhere. “The fact is 5G is going to be everywhere, especially in urban areas. You can replace millions, or tens of millions, of batteries of wireless sensors, especially for smart city and smart agricultural applications,” said Emmanouil M. Tentzeris, Ken Byers Professor in Flexible Electronics in the School of Electrical and Computer Engineering.

Massacre of the Rohingya

EXECUTION: This photo was taken on the day the 10 Rohingya men were killed. Paramilitary police officer Aung Min, left, stands guard behind them. The picture was obtained from a Buddhist village elder, and authenticated by witnesses.


Massacre in Myanmar



How Myanmar forces burned, looted and killed in a remote village

On Sept. 2, Buddhist villagers and Myanmar troops killed 10 Rohingya men in Myanmar’s restive Rakhine state. Reuters uncovered the massacre and has pieced together how it unfolded. During the reporting of this article, two Reuters journalists were arrested by Myanmar police.


INN DIN, Myanmar – Bound together, the 10 Rohingya Muslim captives watched their Buddhist neighbors dig a shallow grave. Soon afterwards, on the morning of Sept. 2, all 10 lay dead. At least two were hacked to death by Buddhist villagers. The rest were shot by Myanmar troops, two of the gravediggers said.

“One grave for 10 people,” said Soe Chay, 55, a retired soldier from Inn Din’s Rakhine Buddhist community who said he helped dig the pit and saw the killings. The soldiers shot each man two or three times, he said. “When they were being buried, some were still making noises. Others were already dead.”

The killings in the coastal village of Inn Din marked another bloody episode in the ethnic violence sweeping northern Rakhine state, on Myanmar’s western fringe. Nearly 690,000 Rohingya Muslims have fled their villages and crossed the border into Bangladesh since August. None of Inn Din’s 6,000 Rohingya remained in the village as of October.

The Rohingya accuse the army of arson, rapes and killings aimed at rubbing them out of existence in this mainly Buddhist nation of 53 million. The United Nations has said the army may have committed genocide; the United States has called the action ethnic cleansing. Myanmar says its “clearance operation” is a legitimate response to attacks by Rohingya insurgents.

Rohingya trace their presence in Rakhine back centuries. But most Burmese consider them to be unwanted immigrants from Bangladesh; the army refers to the Rohingya as “Bengalis.” In recent years, sectarian tensions have risen and the government has confined more than 100,000 Rohingya in camps where they have limited access to food, medicine and education.

Reuters has pieced together what happened in Inn Din in the days leading up to the killing of the 10 Rohingya – eight men and two high school students in their late teens.

Until now, accounts of the violence against the Rohingya in Rakhine state have been provided only by its victims. The Reuters reconstruction draws for the first time on interviews with Buddhist villagers who confessed to torching Rohingya homes, burying bodies and killing Muslims.

This account also marks the first time soldiers and paramilitary police have been implicated by testimony from security personnel themselves. Members of the paramilitary police gave Reuters insider descriptions of the operation to drive out the Rohingya from Inn Din, confirming that the military played the lead role in the campaign.

The slain men’s families, now sheltering in Bangladesh refugee camps, identified the victims through photographs shown to them by Reuters. The dead men were fishermen, shopkeepers, the two teenage students and an Islamic teacher.

Three photographs, provided to Reuters by a Buddhist village elder, capture key moments in the massacre at Inn Din, from the Rohingya men’s detention by soldiers in the early evening of Sept. 1 to their execution shortly after 10 a.m. on Sept. 2. Two photos – one taken the first day, the other on the day of the killings – show the 10 captives lined up in a row, kneeling. The final photograph shows the men’s bloodied bodies piled in the shallow grave.

The Reuters investigation of the Inn Din massacre was what prompted Myanmar police authorities to arrest two of the news agency’s reporters. The reporters, Burmese citizens Wa Lone and Kyaw Soe Oo, were detained on Dec. 12 for allegedly obtaining confidential documents relating to Rakhine.

Then, on Jan. 10, the military issued a statement that confirmed portions of what Wa Lone, Kyaw Soe Oo and their colleagues were preparing to report, acknowledging that 10 Rohingya men were massacred in the village. It confirmed that Buddhist villagers attacked some of the men with swords and soldiers shot the others dead.

The statement coincided with an application to the court by prosecutors to charge Wa Lone and Kyaw Soe Oo under Myanmar’s Official Secrets Act, which dates back to the time of colonial British rule. The charges carry a maximum 14-year prison sentence.

But the military’s version of events is contradicted in important respects by accounts given to Reuters by Rakhine Buddhist and Rohingya Muslim witnesses. The military said the 10 men belonged to a group of 200 “terrorists” that attacked security forces. Soldiers decided to kill the men, the army said, because intense fighting in the area made it impossible to transfer them to police custody. The army said it would take action against those involved.

Buddhist villagers interviewed for this article reported no attack by a large number of insurgents on security forces in Inn Din. And Rohingya witnesses told Reuters that soldiers plucked the 10 from among hundreds of men, women and children who had sought safety on a nearby beach.

Scores of interviews with Rakhine Buddhist villagers, soldiers, paramilitary police, Rohingya Muslims and local administrators further revealed:


• The military and paramilitary police organized Buddhist residents of Inn Din and at least two other villages to torch Rohingya homes, more than a dozen Buddhist villagers said. Eleven Buddhist villagers said Buddhists committed acts of violence, including killings. The government and army have repeatedly blamed Rohingya insurgents for burning villages and homes.

• An order to “clear” Inn Din’s Rohingya hamlets was passed down the command chain from the military, said three paramilitary police officers speaking on condition of anonymity and a fourth police officer at an intelligence unit in the regional capital Sittwe. Security forces wore civilian clothes to avoid detection during raids, one of the paramilitary police officers said.


• Some members of the paramilitary police looted Rohingya property, including cows and motorcycles, in order to sell it, according to village administrator Maung Thein Chay and one of the paramilitary police officers.

• Operations in Inn Din were led by the army’s 33rd Light Infantry Division, supported by the paramilitary 8th Security Police Battalion, according to four police officers, all of them members of the battalion.


The killings in Inn Din

Michael G. Karnavas, a U.S. lawyer based in The Hague who has worked on cases at international criminal tribunals, said evidence that the military had organized Buddhist civilians to commit violence against Rohingya “would be the closest thing to a smoking gun in establishing not just intent, but even specific genocidal intent, since the attacks seem designed to destroy the Rohingya or at least a significant part of them.”

Evidence of the execution of men in government custody also could be used to build a case of crimes against humanity against military commanders, Karnavas said, if it could be shown that it was part of a “widespread or systematic” campaign targeting the Rohingya population. Kevin Jon Heller, a University of London law professor who served as a legal associate for convicted war criminal and former Bosnian Serb leader Radovan Karadzic, said an order to clear villages by military command was “unequivocally the crime against humanity of forcible transfer.”

In December, the United States imposed sanctions on the army officer who had been in charge of Western Command troops in Rakhine, Major General Maung Maung Soe. So far, however, Myanmar has not faced international sanctions over the violence. Myanmar’s leader, Aung San Suu Kyi, has disappointed many former supporters in the West by not speaking out against the army’s actions. They had hoped the election of her National League for Democracy party in 2015 would bring democratic reform and an opening of the country. Instead, critics say, Suu Kyi is in thrall to the generals who freed her from house arrest in 2010.


Asked about the evidence Reuters has uncovered about the massacre, government spokesman Zaw Htay said, “We are not denying the allegations about violations of human rights. And we are not giving blanket denials.” If there was “strong and reliable primary evidence” of abuses, the government would investigate, he said. “And then if we found the evidence is true and the violations are there, we will take the necessary action according to our existing law.”

When told that paramilitary police officers had said they received orders to “clear” Inn Din’s Rohingya hamlets, he replied, “We have to verify. We have to ask the Ministry of Home Affairs and Myanmar police forces.” Asked about the allegations of looting by paramilitary police officers, he said the police would investigate.

He expressed surprise when told that Buddhist villagers had confessed to burning Rohingya homes, then added, “We recognize that many, many different allegations are there, but we need to verify who did it. It is very difficult in the current situation.”

Zaw Htay defended the military operation in Rakhine. “The international community needs to understand who did the first terrorist attacks. If that kind of terrorist attack took place in European countries, in the United States, in London, New York, Washington, what would the media say?”


Inn Din lies between the Mayu mountain range and the Bay of Bengal, about 50 km (30 miles) north of Rakhine’s state capital Sittwe. The settlement is made up of a scattering of hamlets around a school, clinic and Buddhist monastery. Buddhist homes cluster in the northern part of the village. For many years there had been tensions between the Buddhists and their Muslim neighbors, who accounted for almost 90 percent of the roughly 7,000 people in the village. But the two communities had managed to co-exist, fishing the coastal waters and cultivating rice in the paddies.

In October 2016, Rohingya militants attacked three police posts in northern Rakhine – the beginning of a new insurgency. After the attacks, Rohingya in Inn Din said many Buddhists stopped hiring them as farmhands and home help. The Buddhists said the Rohingya stopped showing up for work.

On Aug. 25 last year, the rebels struck again, hitting 30 police posts and an army base. The closest attack was just 4 km to the north. In Inn Din, several hundred fearful Buddhists took refuge in the monastery in the center of the village, more than a dozen of their number said. Inn Din’s Buddhist night watchman San Thein, 36, said Buddhist villagers feared being “swallowed up” by their Muslim neighbors. A Buddhist elder said all Rohingya, “including children,” were part of the insurgency and therefore “terrorists.”

On Aug. 27, about 80 troops from Myanmar’s 33rd Light Infantry Division arrived in Inn Din, nine Buddhist villagers said. Two paramilitary police officers and Soe Chay, the retired soldier, said the troops belonged to the 11th infantry regiment of this division. The army officer in charge told villagers they must cook for the soldiers and act as lookouts at night, Soe Chay said. The officer promised his troops would protect Buddhist villagers from their Rohingya neighbors. Five Buddhist villagers said the officer told them they could volunteer to join security operations. Young volunteers would need their parents’ permission to join the troops, however.

The army found willing participants among Inn Din’s Buddhist “security group,” nine members of the organization and two other villagers said. This informal militia was formed after violence broke out in 2012 between Rakhine’s Buddhists and Rohingya Muslims, sparked by reports of the rape and murder of a Buddhist woman by three Muslim men. Myanmar media reported at the time that the three were sentenced to death by a district court.

Inn Din’s security group built watch huts around the Buddhist part of the village, and its members took turns to stand guard. Its ranks included Buddhist firefighters, school teachers, students and unemployed young men. They were useful to the military because they knew the local geography, said Inn Din’s Buddhist administrator, Maung Thein Chay.

Most of the group’s 80 to 100 men armed themselves with machetes and sticks. They also had a handful of guns, according to one member. Some wore green fatigue-style clothing they called “militia suits.”


In the days that followed the 33rd Light Infantry’s arrival, soldiers, police and Buddhist villagers burned most of the homes of Inn Din’s Rohingya Muslims, a dozen Buddhist residents said.

Two of the paramilitary police officers, both members of the 8th Security Police Battalion, said their battalion raided Rohingya hamlets with soldiers from the newly arrived 33rd Light Infantry. One of the police officers said he received verbal orders from his commander to “go and clear” areas where Rohingya lived, which he took to mean to burn them.

The second police officer described taking part in several raids on villages north of Inn Din. The raids involved at least 20 soldiers and between five and seven police, he said. A military captain or major led the soldiers, while a police captain oversaw the police team. The purpose of the raids was to deter the Rohingya from returning.

“If they have a place to live, if they have food to eat, they can carry out more attacks,” he said. “That’s why we burned their houses, mainly for security reasons.”


“I want to be transparent on this case. I don’t want it to happen like that in the future.”

A Rakhine Buddhist elder, explaining why he chose to speak to Reuters about the killings

Soldiers and paramilitary police wore civilian shirts and shorts to blend in with the villagers, according to the second police officer and Inn Din’s Buddhist administrator, Maung Thein Chay. If the media identified the involvement of security personnel, the police officer explained, “we would have very big problems.”

A police spokesman, Colonel Myo Thu Soe, said he knew of no instances of security forces torching villages or wearing civilian clothing. Nor was there any order to “go and clear” or “set fire” to villages. “This is very much impossible,” he told Reuters. “If there are things like that, it should be reported officially, and it has to be investigated officially.”

“As you’ve told me about these matters now, we will scrutinize and check back,” he added. “What I want to say for now is that as for the security forces, there are orders and instructions and step-by-step management, and they have to follow them. So, I don’t think these things happened.”

The army did not respond to a request for comment.

A medical assistant at the Inn Din village clinic, Aung Myat Tun, 20, said he took part in several raids. “Muslim houses were easy to burn because of the thatched roofs. You just light the edge of the roof,” he said. “The village elders put monks’ robes on the end of sticks to make the torches and soaked them with kerosene. We couldn’t bring phones. The police said they will shoot and kill us if they see any of us taking photos.”

The night watchman San Thein, a leading member of the village security group, said troops first swept through the Muslim hamlets. Then, he said, the military sent in Buddhist villagers to burn the houses.

“We got the kerosene for free from the village market after the kalars ran away,” he said, using a Burmese slur for people from South Asia.

A Rakhine Buddhist youth said he thought he heard the sound of a child inside one Rohingya home that was burned. A second villager said he participated in burning a Rohingya home that was occupied.

Soe Chay, the retired soldier who was to dig the grave for the 10 Rohingya men, said he participated in one killing. He told Reuters that troops discovered three Rohingya men and a woman hiding beside a haystack in Inn Din on Aug. 28. One of the men had a smartphone that could be used to take incriminating pictures.

The soldiers told Soe Chay to “do whatever you want to them,” he said. They pointed out the man with the phone and told him to stand up. “I started hacking him with a sword, and a soldier shot him when he fell down.”

Similar violence was playing out across a large part of northern Rakhine, dozens of Buddhist and Rohingya residents said.

Data from the U.N. Operational Satellite Applications Programme shows scores of Rohingya villages in Rakhine state burned in an area stretching 110 km. New York-based Human Rights Watch says more than 350 villages were torched over the three months from Aug. 25, according to an analysis of satellite imagery.

In the village of Laungdon, some 65 km north of Inn Din, Thar Nge, 38, said he was asked by police and local officials to join a Buddhist security group. “The army invited us to burn the kalar village at Hpaw Ti Kaung,” he said, adding that four villagers and nearly 20 soldiers and police were involved in the operation. “Police shot inside the village so all the villagers fled and then we set fire to it. Their village was burned because police believed the villagers supported Rohingya militants – that’s why they cleaned it with fire.”

A Buddhist student from Ta Man Tha village, 15 km north of Laungdon, said he too participated in the burning of Rohingya homes. An army officer sought 30 volunteers to burn “kalar” villages, said the student. Nearly 50 volunteered and gathered fuel from motorbikes and from a market.

“They separated us into several groups. We were not allowed to enter the village directly. We had to surround it and approach the village that way. The army would shoot gunfire ahead of us and then the army asked us to enter,” he said.

“Muslim houses were easy to burn because of the thatched roofs. You just light the edge of the roof.”

Buddhist villager Aung Myat Tun

After the Rohingya had fled Inn Din, Buddhist villagers took their property, including chickens and goats, Buddhist residents told Reuters. But the most valuable goods, mostly motorcycles and cattle, were collected by members of the 8th Security Police Battalion and sold, said the first police officer and Inn Din village administrator Maung Thein Chay. Maung Thein Chay said the commander of the 8th Battalion, Thant Zin Oo, struck a deal with Buddhist businessmen from other parts of Rakhine state and sold them cattle. The police officer said he had stolen four cows from Rohingya villagers, only for Thant Zin Oo to snatch them away.

Reached by phone, Thant Zin Oo did not comment. Colonel Myo Thu Soe, the police spokesman, said the police would investigate the allegations of looting.

By Sept. 1, several hundred Rohingya from Inn Din were sheltering at a makeshift camp on a nearby beach. They erected tarpaulin shelters to shield themselves from heavy rain.

Among this group were the 10 Rohingya men who would be killed the next morning. Reuters has identified all of the 10 by speaking to witnesses among Inn Din’s Buddhist community and Rohingya relatives and witnesses tracked down in refugee camps in Bangladesh.

Five of the men, Dil Mohammed, 35, Nur Mohammed, 29, Shoket Ullah, 35, Habizu, 40, and Shaker Ahmed, 45, were fishermen or fish sellers. The wealthiest of the group, Abul Hashim, 25, ran a store selling nets and machine parts to fishermen and farmers. Abdul Majid, a 45-year-old father of eight, ran a small shop selling areca nut wrapped in betel leaves, commonly chewed like tobacco. Abulu, 17, and Rashid Ahmed, 18, were high school students. Abdul Malik, 30, was an Islamic teacher.

According to the statement released by the army on Jan. 10, security forces had gone to a coastal area where they “were attacked by about 200 Bengalis with sticks and swords.” The statement said that “as the security forces opened fire into the sky, the Bengalis dispersed and ran away. Ten of them were arrested.”


Three Buddhist and more than a dozen Rohingya witnesses contradict this version of events. Their accounts differ from one another in some details. The Buddhists spoke of a confrontation between a small group of Rohingya men and some soldiers near the beach. But there is unanimity on a crucial point: None said the military had come under a large-scale attack in Inn Din.

Government spokesman Zaw Htay referred Reuters to the army’s statement of Jan. 10 and declined to elaborate further. The army did not respond to a request for comment.

The Rohingya witnesses, who were on or near the beach, said Islamic teacher Abdul Malik had gone back to his hamlet with his sons to collect food and bamboo for shelter. When he returned, a group of at least seven soldiers and armed Buddhist villagers were following him, these witnesses said. Abdul Malik walked towards the watching Rohingya Muslims unsteadily, with blood dripping from his head. Some witnesses said they had seen one of the armed men strike the back of Abdul Malik’s head with a knife.

Then the military beckoned with their guns to the crowd of roughly 300 Rohingya to assemble in the paddies, these witnesses said. The soldiers and the Rohingya, hailing from different parts of Myanmar, spoke different languages. Educated villagers translated for their fellow Rohingya.


“I could not hear much, but they pointed toward my husband and some other men to get up and come forward,” said Rehana Khatun, 22, the wife of Nur Mohammed, one of the 10 who were later slain. “We heard they wanted the men for a meeting. The military asked the rest of us to return to the beach.”

Soldiers held and questioned the 10 men in a building at Inn Din’s school for a night, the military said. Rashid Ahmed and Abulu had studied there alongside Rakhine Buddhist students until the attacks by Rohingya rebels in October 2016. Schools were shut temporarily, disrupting the pair’s final year.

“I just remember him sitting there and studying, and it was always amazing to me because I am not educated,” said Rashid Ahmed’s father, farmer Abdu Shakur, 50. “I would look at him reading. He would be the first one in the family to be educated.”

A photograph, taken on the evening the men were detained, shows the two Rohingya students and the eight older men kneeling on a path beside the village clinic, most of them shirtless. They were stripped when first detained, a dozen Rohingya witnesses said. It isn’t clear why. That evening, Buddhist villagers said, the men were “treated” to a last meal of beef. They were provided with fresh clothing.

On Sept. 2, the men were taken to scrubland north of the village, near a graveyard for Buddhist residents, six Buddhist villagers said. The spot is backed by a hill crested with trees. There, on their knees, the 10 were photographed again and questioned by security personnel about the disappearance of a local Buddhist farmer named Maung Ni, according to a Rakhine elder who said he witnessed the interrogation.

Reuters was not able to establish what happened to Maung Ni. According to Buddhist neighbors, the farmer went missing after leaving home early on Aug. 25 to tend his cattle. Several Rakhine Buddhist and Rohingya villagers told Reuters they believed he had been killed, but they knew of no evidence connecting any of the 10 men to his disappearance. The army said in its Jan. 10 statement that “Bengali terrorists” had killed Maung Ni, but did not identify the perpetrators.

Two of the men pictured behind the Rohingya prisoners in the photograph taken on the morning of Sept. 2 belong to the 8th Security Police Battalion. Reuters confirmed the identities of the two men from their Facebook pages and by visiting them in person.

One of the two officers, Aung Min, a police recruit from Yangon, stands directly behind the captives. He looks at the camera as he holds a weapon. The other officer, police Captain Moe Yan Naing, is the figure on the top right. He walks with his rifle over his shoulder.

The day after the two Reuters reporters were arrested in December, Myanmar’s government also announced that Moe Yan Naing had been arrested and was being investigated under the 1923 Official Secrets Act.

Aung Min, who is not facing legal action, declined to speak to Reuters.


Three Buddhist youths said they watched from a hut as the 10 Rohingya captives were led up a hill by soldiers towards the site of their deaths.

One of the gravediggers, retired soldier Soe Chay, said Maung Ni’s sons were invited by the army officer in charge of the squad to strike the first blows.

The first son beheaded the Islamic teacher, Abdul Malik, according to Soe Chay. The second son hacked another of the men in the neck.

“After the brothers sliced them both with swords, the squad fired with guns. Two to three shots to one person,” said Soe Chay. A second gravedigger, who declined to be identified, confirmed that soldiers had shot some of the men.

In its Jan. 10 statement, the military said the two brothers and a third villager had “cut the Bengali terrorists” with swords and then, in the chaos, four members of the security forces had shot the captives. “Action will be taken against the villagers who participated in the case and the members of security forces who broke the Rules of Engagement under the law,” the statement said. It didn’t spell out those rules.

Tun Aye, one of the sons of Maung Ni, has been detained on murder charges, his lawyer said on Jan. 13. Contacted by Reuters on Feb. 8, the lawyer declined to comment further. Reuters was unable to reach the other brother.

In October, Inn Din locals pointed two Reuters reporters towards an area of brush behind the hill where they said the killings took place. The reporters discovered a newly cut trail leading to soft, recently disturbed earth littered with bones. Some of the bones were entangled with scraps of clothing and string that appeared to match the cord that is seen binding the captives’ wrists in the photographs. The immediate area was marked by the smell of death.

Reuters showed photographs of the site to three forensic experts: Homer Venters, director of programs at Physicians for Human Rights; Derrick Pounder, a pathologist who has consulted for Amnesty International and the United Nations; and Luis Fondebrider, president of the Argentine Forensic Anthropology Team, who investigated the graves of those killed under Argentina’s military junta in the 1970s and 1980s. All observed human remains, including the thoracic part of a spinal column, ribs, scapula, femur and tibia. Pounder said he couldn’t rule out the presence of animal bones as well.

The Rakhine Buddhist elder provided Reuters reporters with a photograph which shows the aftermath of the execution. In it, the 10 Rohingya men are wearing the same clothing as in the previous photo and are tied to each other with the same yellow cord, piled into a small hole in the earth, blood pooling around them. Abdul Malik, the Islamic teacher, appears to have been beheaded. Abulu, the student, has a gaping wound in his neck. Both injuries appear consistent with Soe Chay’s account.

Fondebrider reviewed this picture. He said injuries visible on two of the bodies were consistent with “the action of a machete or something sharp that was applied on the throat.”

Some family members did not know for sure that the men had been killed until Reuters returned to their shelters in Bangladesh in January.

“I can’t explain what I feel inside. My husband is dead,” said Rehana Khatun, wife of Nur Mohammed. “My husband is gone forever. I don’t want anything else, but I want justice for his death.”

In Inn Din, the Buddhist elder explained why he chose to share evidence of the killings with Reuters. “I want to be transparent on this case. I don’t want it to happen like that in future.”

Massacre in Myanmar

By Wa Lone, Kyaw Soe Oo, Simon Lewis and Antoni Slodkowski

Graphics: Jessica Wang, Simon Scarr and Matthew Weber

Photo editing: Thomas White

Video: Matthew Larotonda and Ryan Brooks

Design: Troy Dunkley

Edited by Janet McBride, Martin Howell and Alex Richardson  

Carbon-fiber battery could revolutionize car


Battery combines carbon-fiber anode and lithium-iron phosphate-coated foil cathode.

Over the next few years, the batteries that go into electric vehicles are going to get cheap enough that an EV should cost no more than an equivalent-sized vehicle with an internal combustion engine. But those EVs are still going to weigh more than their gas-powered counterparts—particularly if the market insists on longer and longer range estimates—with the battery pack contributing 20-25 percent of the total mass of the vehicle.

But there is a solution: turn some of the car’s structural components into batteries themselves. Do that, and your battery weight effectively vanishes because regardless of powertrain, every vehicle still needs structural components to hold it together. It’s an approach that groups around the world have been pursuing for some time now, and the idea was neatly explained by Volvo’s chief technology officer, Henrik Green, when Ars spoke with him in early March:

What we have learned… just to take an example: “How do you integrate the most efficiently a battery cell into a car?” Well, if you do it in a traditional way, you put the cell into the box, call it the module; you put a number of modules into a box, you call that the pack. You put the pack into a vehicle and then you have a standardized solution and you can scale it for 10 years and 10 manufacturing slots.

But in essence, that’s a quite inefficient solution in terms of weight and space, etc. So here you could really go deeper, and how would you directly integrate the cells into a body and get rid of these modules and packs and stuff in between? That is the challenge that we are working with in future generations, and that will change how you fundamentally build cars. You might have thought that time of changing that would have ended, but it has just been reborn.



Tesla is known to be working on designing new battery modules that also work as structural elements, but the California automaker is fashioning those structural modules out of traditional cylindrical cells. There’s a more elegant approach to the idea, though, and a group at Chalmers University of Technology in Sweden led by professor Leif Asp has just made a bit of a breakthrough in that regard, making each component of the battery out of materials that work structurally as well as electrically.


The structural battery combines a carbon-fiber anode and a lithium-iron phosphate-coated aluminum foil cathode, which are separated by a glass fiber separator in a structural battery electrolyte matrix material. The anode does triple duty, hosting the lithium ions, conducting electrons, and reinforcing everything at the same time. The electrolyte and cathode similarly support structural loads and do their jobs in moving ions.



The researchers tested a couple different types of glass fiber—both resulting in cells with a nominal voltage of 2.8 V—and achieved better results in terms of battery performance with thinner, plain weave. The cells using this construction had a specific capacity of 8.55 Ah/kg, an energy density of 23.6 Wh/kg (at 0.05 C), a specific power of 9.56 W/kg (at 3 C), and a thickness of 0.27 mm. To put at least one of those numbers in context, the 4680 cells that Tesla is moving to have an energy density of 380 Wh/kg. However, that energy density figure for the cylindrical cells does not include the mass of the structural matrix that surrounds them (when used as structural panels).

Speaking of structural loads, the greatest stiffness was also achieved with plain glass fiber weave, at 25.5 GPa. Again, to put that number into context, it’s roughly similar to glass fiber-reinforced plastic, whereas carbon fiber-reinforced plastic will be around 10 times greater, depending on whether it’s resin transfer molding or woven sheets pre-impregnated with resin (known as pre-preg).

Professor Asp’s group is now working to see if swapping the cathode’s aluminum foil for carbon fiber will increase both stiffness (which it should) and electrical performance. The group is also testing even thinner separators. He hopes to reach 75 Wh/kg and 75 GPa, which would result in a cell that is slightly stiffer than aluminum (GPa: 68) but obviously much lighter.

Building electric cars or even airplanes out of structural composite batteries is still a longer-term project, and even at their best, structural battery cells may never approach the performance of dedicated cells. But since they would also replace heavier metal structures, the resulting vehicle should be much lighter overall.

Meanwhile, Asp thinks other products could see the benefits sooner. “The next generation structural battery has fantastic potential. If you look at consumer technology, it could be quite possible within a few years to manufacture smartphones, laptops, or electric bicycles that weigh half as much as today and are much more compact,” Asp said.

Listing image by Marcus Folino

Whitest-ever paint could help cool Earth, study shows


New paint reflects 98% of sunlight as well as radiating infrared heat into space, reducing need for air conditioning

Prof Xiulin Ruan, a professor of mechanical engineering, with a sample of the paint.
Prof Xiulin Ruan, a professor of mechanical engineering, with a sample of the paint. Photograph: Jared Pike/Purdue University
 Environment editor



The whitest-ever paint has been produced by academic researchers, with the aim of boosting the cooling of buildings and tackling the climate crisis.

The new paint reflects 98% of sunlight as well as radiating infrared heat through the atmosphere into space. In tests, it cooled surfaces by 4.5C below the ambient temperature, even in strong sunlight. The researchers said the paint could be on the market in one or two years.


White-painted roofs have been used to cool buildings for centuries. As global heating pushes temperatures up, the technique is also being used on modern city buildings, such as in Ahmedabad in India and New York City in the US.

Currently available reflective white paints are far better than dark roofing materials, but only reflect 80-90% of sunlight and absorb UV light. This means they cannot cool surfaces below ambient temperatures. The new paint does this, leading to less need for air conditioning and the carbon emissions they produce, which are rising rapidly.

“Our paint can help fight against global warming by helping to cool the Earth – that’s the cool point,” said Prof Xiulin Ruan at Purdue University in the US. “Producing the whitest white means the paint can reflect the maximum amount of sunlight back to space.”

Infrared image shows how a sample of the ‘whitest paint’ (the dark purple square in the middle) cools the board below ambient temperature.
An infrared image shows how a sample of the ‘whitest paint’ (the dark purple square in the middle) cools the board below ambient temperature. Photograph: Joseph Peoples/Purdue University

Ruan said painting a roof of 93 sq metres (1,000 sq ft) would give a cooling power of 10 kilowatts: “That’s more powerful than the central air conditioners used by most houses.”

The new paint was revealed in a report in the journal ACS Applied Materials & Interfaces. Three factors are responsible for the paint’s cooling performance. First, barium sulphate was used as the pigment which, unlike conventional titanium dioxide pigment, does not absorb UV light. Second, a high concentration of pigment was used – 60%.


Third, the pigment particles were of varied size. The amount of light scattered by a particle depends on its size, so using a range scatters more of the light spectrum from the sun. Ruan’s lab had assessed more than 100 different materials and tested about 50 formulations for each of the most promising. Their previous whitest paint used calcium carbonate – chalk – and reflected 95.5% sunlight.

The barium sulphate paint enables surfaces to be below the ambient air temperature, even in direct sunlight, because it reflects so much of the sun’s light and also radiates infrared heat at a wavelength that is not absorbed by air. “The radiation can go through the atmosphere, being directly lost to deep space, which is extremely cold,” said Ruan.

The researchers said the ultra-white paint uses a standard acrylic solvent and could be manufactured like conventional paint. They claim the paint would be similar in price to current paints, with barium sulphate actually cheaper than titanium dioxide. They have also tested the paint’s resistance to abrasion, but said longer-term weathering tests were needed to assess its long-term durability.

Ruan said the paint was not a risk to people’s eyesight: “Our surface reflects the sunlight diffusely, so the power going in any particular direction is not very strong. It just looks bright white, a bit whiter than snow.”

A patent for the paint has been filed jointly by the university and research team, which is now working with a large corporation towards commercialisation: “We think this paint will be made widely available to the market, in one or two years, I hope, if we do it quickly.”

Lukas Schertel, a light-scattering expert at the University of Cambridge, UK, who was not part of the research team, said: “Using paint for cooling is not new but has still a high potential to improve our society, as it is widely used. This study makes a step towards commercially relevant solutions. If further improved, I am convinced such technology can play a role in reducing carbon emissions and having a global impact.”

Cool roofs: beating the midday sun with a slap of white paint
Read more

Schertel said the high concentration of pigment in the paint and the relatively thick layers used raised questions of cost: “Pigment is the main cost in paint.” Ruan said his team hoped to optimise the paint so it can be used in thinner layers, perhaps by using new materials, so it will be easier to apply and lower cost.

Andrew Parnell, who works on sustainable coatings at the University of Sheffield, UK, said: “The principle is very exciting and the science [in the new study] is good. But I think there might be logistical problems that are not trivial. How many million tonnes [of barium sulphate] would you need?”

Parnell said a comparison of the carbon dioxide emitted by the mining of barium sulphate with the emissions saved from lower air conditioning use would be needed to fully assess the new paint. He also said green roofs, on which plants grow, could be more sustainable where practical.

Project Drawdown, a charity that assesses climate solutions, estimates that white roofs and green roofs could avoid between 600m and 1.1bn tonnes of carbon dioxide by 2050, roughly equivalent to two to three years of the UK’s total annual emissions.


one in eight patients die within four months of discharge Coronavirus – latest updates

Almost third of UK Covid hospital patients readmitted within four months

BMJ analysis of 48,000 records also finds one in eight patients die within four months of discharge

Sars-CoV-2 virus image
Sars-CoV-2, the virus that causes Covid-19, isolated from a patient. The long-term impact of the disease has caused doctors to push for testing to detect early signs of organ damage. Photograph: National Institute of Allergy an/AFP/Getty Images
 Science editor



Nearly a third of people who have been in hospital suffering from Covid-19 are readmitted for further treatment within four months of being discharged, and one in eight of patients dies in the same period, doctors have found.

The striking long-term impact of the disease has prompted doctors to call for ongoing tests and monitoring of former coronavirus patients to detect early signs of organ damage and other complications caused by the virus.


While Covid is widely known to cause serious respiratory problems, the virus can also infect and damage other organs such as the heart, liver and kidneys.

Researchers at University College London, the Office for National Statistics, and the University of Leicester, compared medical records of nearly 48,000 people who had had hospital treatment for Covid and had been discharged by 31 August 2020, with records from a matched control group of people in the general population.


The records were used to track rates of readmission, of deaths, and of diagnoses for a range of respiratory, heart, kidney, liver and metabolic diseases, such as diabetes.

After an average follow-up time of 140 days, nearly a third of the Covid patients who had been discharged from hospital had been readmitted and about one in eight had died, rates considerably higher than seen in the control group.

“This is a concern and we need to take it seriously,” said Dr Amitava Banerjee, at the Institute of Health Informatics at University College London. “We show conclusively here that this is very far from a benign illness. We need to monitor post-Covid patients so we can pick up organ impairment early on.”

Unexplained symptoms that persist for more than four months are often described as “long Covid” or “post-Covid syndrome”, but doctors are still working out patterns of long-term organ damage that can be caused by the infection.

New diagnoses of respiratory and heart disease and diabetes were all raised in the former Covid patients compared with the control group, as were problems with the function of multiple organs. The rate of multi-organ dysfunction after discharge was greater among patients under the age of 70 compared with those over 70, they found, and the rate was higher in ethnic minorities than in the white population.

The authors write in the BMJ: “The increase in risk was not confined to the elderly and was not uniform across ethnicities. The diagnosis, treatment, and prevention of post-Covid syndrome requires integrated rather than organ or disease specific approaches, and urgent research is needed to establish the risk factors. Our findings suggest that the long-term burden of Covid-19 related morbidity on hospitals and broader healthcare systems might be substantial.”

The study revealed that while existing conditions such as heart disease, diabetes and respiratory illnesses put people at greater risk of severe Covid disease, the infection itself could cause such medical problems.

“Until now we tended to think of heart disease, kidney disease and diabetes as risk factors for Covid patients, but these are also complications of Covid as well,” said Banarjee.

Katalin Karikó, the pioneering scientists behind COVID-19 vaccines Awarded

Rosenstiel Award given to pioneering scientists behind COVID-19 vaccines

This year’s prize for distinguished work in basic medical research was awarded to Katalin Karikó and Drew Weissman for work on messenger RNA.

Katalin Karikó and Drew WeissmanCourtesy Karikó/University of Pennsylvania

Katalin Karikó and Drew Weissman

Brandeis University and the Rosenstiel Foundation are pleased to award the 50th annual Lewis S. Rosenstiel Award for Distinguished Work in Basic Medical Research to Katalin Karikó and Drew Weissman ’81, MA ’81, P’15, for their groundbreaking work in the modification of nucleic acids to develop RNA therapeutics and vaccines.

Karikó, senior vice president at BioNTech RNA Pharmaceuticals, and Weissman, a professor of medicine at the Perelman School of Medicine at the University of Pennsylvania, pioneered much of the science underlying two of the COVID-19 vaccines now being given to tens of millions of people across the globe. 

Rosenstiel Medal

The Rosenstiel Award

By engineering a modified version of the messenger RNA (mRNA) inside human cells and then developing a system to deliver it to its target, the two researchers laid the groundwork for the vaccines brought to fruition by Pfizer/BioNTech and Moderna

“This award celebrates how basic research in molecular biology can be the foundation for applications that can affect the lives of us all,” said James Haber, the Abraham and Etta Goodman Professor of Biology and director of the Rosenstiel Basic Medical Sciences Research Center.

“Through their painstaking research into mRNA – and persistence despite setbacks – Weissman and Karikó laid the groundwork for vaccines that will save countless lives.”

Peter Gruber Endowed Chair in Neuroscience and 2017 winner of the Nobel Prize in Physiology or Medicine Michael Rosbash said: 

“Among the few positive consequences of the current pandemic are the successful efforts made worldwide to generate effective vaccines. The most creative of these rely on the new messenger RNA technology pioneered by Kariko and Weissman. This is a great story where individual initiative in basic science has ended up having a remarkable real-world impact.”

The Rosenstiel Award has had a distinguished record of identifying and honoring scientists who subsequently have been honored with the Lasker and Nobel Prizes. Thirty-six of 93 Rosenstiel Award winners have subsequently been awarded the Nobel Prize in Medicine or Physiology or in Chemistry. 

A full list of awardees can be found on the award’s website.

The award will be presented on February 8 at 12 p.m. via webinar. Register for the event here.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, and Derrick Rossi, co-founder of Moderna, will present congratulatory remarks. 

Karikó and Weissman began working together over 20 years ago when both were at U Penn. 

At the time, many scientists didn’t believe mRNA, which transport instructions from DNA to the ribosomes for the production of proteins, could be the basis for a vaccine. In experiments, injecting mRNA into mice caused deadly inflammation.

But Karikó and Weissman pressed on, discovering a method of altering mRNA that enabled it to enter cells without triggering the body’s immune system. They did this by tweaking one of the four nucleosides that are the building blocks of mRNA. 

Several years later, Karikó and Weissman devised a method of packaging mRNA inside a lipid nanoparticle — a small bubble of oil — so that the molecule didn’t fall apart as it traveled through the body. 

“We basically tested every possible delivery system and found this was the best,” Weissman recently told BrandeisNOW.

The COVID-19 mRNA vaccines work by spurring human cells to produce the spike-shaped protein found on SARS-CoV-2, the virus that causes the illness, and triggering the immune system to produce protective antibodies.

In general, mRNA vaccines have the advantage of being cheaper to produce than traditional vaccines for chickenpox, polio, flu or rabies. It’s also hoped they can be adapted to treat other infectious diseases such as genital herpes (which is caused by the herpes simplex virus), influenza, Zika and HIV.

“The COVID-19 vaccine breakthrough is a great example of how basic science innovations, such as the RNA technology pioneered by Weissman and Karikó, can have an enormous impact on advances in the biomedical sciences,” said biochemist Carol Fierke, the university’s new provost and executive vice president.

In addition to her post at BioNTech, Karikó is an adjunct associate professor at the Perelman School of Medicine at the University of Pennsylvania. Weissman is also director of vaccine research at the Perelman school’s division of infectious diseases.

Categories: AlumniScience and Technology

Mindless US Academic Career System Almost Killed off the Virus Vaccine

How Our Brutal Science System Almost Cost Us A Pioneer Of mRNA Vaccines

Pfizer and BioNTech's COVID-19 vaccine. (Matthew Horwood/Getty Images)
Pfizer and BioNTech’s COVID-19 vaccine. (Matthew Horwood/Getty Images)

Lately, my social media feeds have been filled with “vaxxies” — selfies of health care friends getting COVID-19 vaccines and gushing about how the shots brought them hope or relief. Many express gratitude for the science that yielded the vaccines.

When I got my own shot — after working the chaotic first surge at an understaffed hospital in March and April — I felt an added emotion: awe.

When can I get a vaccine? Is it safe? What are the side effects? Get this info & more in your inbox each week. Sign up now.

You see, I witnessed some of the early scientific heartbreaks that came before the historic vaccine victories. And I found myself simply awestruck by the scientists I knew who persevered in spite of our system of scientific research.

The system helped lead to progress, but it also demoralized a junior researcher to the point that anyone of less grit and determination would have just given up long before the groundwork for today’s vaccines was laid.

An Existential Career Threat

Here’s my story: 20 years ago, I worked part-time in a tumble-down laboratory in a dusty corner of an old medical school building at the University of Pennsylvania, where I was an undergrad. For three years, I studied HIV replication in T-cells under researchers Drew Weissman and Katalin Karikó.

These days, they are coronavirus vaccine heroes, but back then, their very early work on mRNA vaccines aimed to fight HIV. After spending my first four months in the lab on an experiment that never worked, I learned that good science is really, really hard.

I didn’t know it at the time, but I also absorbed what I later could describe as the sociology of science — how the sausage is made — and it wasn’t always pretty.

From the photo album of author David Scales (second from right), the 2001 lab team that included Katalin Karikó (third from left.)
From the photo album of author David Scales (second from right), the 2001 lab team that included Katalin Karikó (third from left.)

While Weissman was an expert at designing experiments, I remember him most for his generosity. He made sure all contributors in the lab shared the credit, from the lab tech and lowly undergrad all the way to fellow researcher Karikó.

Still, Karikó was struggling. Her science was fantastic, but she was less adept at the competitive game of science. She tried again and again to win grants, and each time, her applications were rejected.

Eventually, in the mid-1990s, she suffered the academic indignity of demotion, meaning she was taken off the academic ladder that leads to becoming a professor. We never discussed it personally because by the time I joined the lab, Karikó’s history was still only discussed in hushed tones as a cautionary tale for young scientists.

I learned that while universities pay the salaries of many of their professors in English or anthropology, they expect faculty in the medical schools to pay their own way with either clinical work or external research funding. This puts tremendous financial pressure on eager young medical researchers, sometimes leading them not to the projects that are most needed or that they are most passionate about, but to the projects that will get them funding.

Karikó lived that nightmare, but stuck to her passions. She was too committed to the promise of mRNA to switch to other, perhaps more easily fundable projects. Eventually, the university stopped supporting her.

It’s hard to describe what this moment means to people who have never worked in science at a university, but it is more than the frustration of an experiment not working or laudable work going unrecognized. It is an existential career threat. Everything you have worked for your entire life is suddenly in jeopardy. It is a forced career change on the assumption that if you can’t get the grants, you’re not a good enough scientist.

Clearly, this was a false assumption in Karikó’s case. She was a dynamo, with a passion for science that rubbed off on those around her. I remember one lab meeting where she arrived with a copy of Science or Nature magazine, absorbed in a new study that showed some cool biological feature of how cells reacted under stress. It wasn’t her area of research, yet she was still in awe of the beauty and intricacy our cells are imbued with, and her enthusiasm was infectious.

A Scientist To Her Core

She also shared jaw-dropping anecdotes about working as a scientist in the Eastern Bloc, from the cutthroat competition in school to the practice of smoking cigarettes in the lab (except when someone opened a container of very flammable ether).

For Karikó, who had persevered under those extraordinarily difficult circumstances in communist Hungary, demotion was particularly bitter. Most people in such circumstances end up leaving the university, but she pressed on.

I think she had to. Mark Doty, a poet, visited and gave a talk my senior year at Penn. Afterwards, a student and aspiring poet asked when and how Doty knew he was willing to endure the sacrifices it took to be a poet, with all the rejections, the financial struggle and the economic instability.

Doty said that he couldn’t not be a poet. He tried other things and just wasn’t happy. For him, it wasn’t a choice. Seeing Karikó get so excited about scientific findings that weren’t even related to her research, I got a similar sense about her too: she couldn’t not be a scientist. It was baked into her bones. Luckily for us, now.

It’s the secret you don’t learn in school. We know doing good science is hard. But it isn’t only difficult because divining nature’s secrets is a unique challenge. It is unbelievably, brutally difficult for all of the other non-science skills that are needed but not explicitly taught: writing grants (“grantsmanship”), getting invited to speak at conferences, building collaborative research relationships, having the political awareness to attract allies and mentors within a department or university who can help find support for you.

It’s the sociology of doing science at a university that makes science even harder than it already is. Usually, stories like Karikó’s end in obscurity and disappointment. Add in being a woman and an immigrant, and it makes her perseverance even more inspiring.

You Were Right, Kati

For me, seeing such an impressive mentor struggle so hard acted as a powerful push away from doing science. I spent a year abroad studying history and philosophy of science, learning the social processes by which scientific facts become solidified, then studied medicine and sociology.

But lately, I have found myself drawn back to science, as empirical facts are dismissed with a tweet. If anything, the problems Karikó faced have gotten worse over the past 20 years. It is high time for scientists to save science. But, at its best, science can produce beauty, wonder and, occasionally, through the hard work of very dedicated individuals, it can produce technologies that save millions of lives.

The coronavirus vaccine has demonstrated that we need good science – and good scientists – now more than ever. And we need to make sure that they stay in science, one way or another.

Academic science failed Karikó. But when she contacted me in 2015, I saw she had moved to the private sector, a common path for researchers when a university stops offering support. I was glad to see she had landed on her feet. And now, I watch in awe, like the rest of the world, as the technology she helped developed leads to one of the most spectacular victories in the history of science – a vaccine for a deadly pandemic developed in less than one year.

So, my vaccination day was an emotional one. As the lipid-encapsulated mRNA molecules went into my arm, I reminisced about Kati and Drew, and the lab circa 2000. And I thought: You were right, Kati. You were right.

The recent "vaxxie" of author David Scales (courtesy David Scales).
The recent “vaxxie” of author David Scales (courtesy David Scales).

Dr. David Scales is a physician and assistant professor of medicine at Weill Cornell Medical College. He can be found on Twitter @davidascales. The views and opinions expressed in this piece are those of the author and do not necessarily reflect the official policy or position of Weill Cornell Medical College.