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Rectennas in Baratunde A. Cola's NEST (NanoEngineered Systems and Transport) lab

Rectennas in Baratunde A. Cola’s NEST (NanoEngineered Systems and Transport) lab

Using nanometer-scale components, researchers have demonstrated the first optical rectenna, a device that combines the functions of an antenna and a rectifier diode to convert light directly into DC current.

Based on multiwall carbon nanotubes and tiny rectifiers fabricated onto them, the optical rectennas could provide a new technology for photodetectors that would operate without the need for cooling, energy harvesters that would convert waste heat to electricity–and ultimately for a new way to efficiently capture solar energy.

In the new devices, developed by engineers at the Georgia Institute of Technology, the carbon nanotubes act as antennas to capture light from the sun or other sources. As the waves of light hit the nanotube antennas, they create an oscillating charge that moves through rectifier devices attached to them. The rectifiers switch on and off at record high petahertz speeds, creating a small direct current.

Billions of rectennas in an array can produce significant current, though the efficiency of the devices demonstrated so far remains below one percent. The researchers hope to boost that output through optimization techniques, and believe that a rectenna with commercial potential may be available within a year.

“We could ultimately make solar cells that are twice as efficient at a cost that is ten times lower, and that is to me an opportunity to change the world in a very big way” said Baratunde Cola, an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. “As a robust, high-temperature detector, these rectennas could be a completely disruptive technology if we can get to one percent efficiency. If we can get to higher efficiencies, we could apply it to energy conversion technologies and solar energy capture.”

The research, supported by the Defense Advanced Research Projects Agency (DARPA), the Space and Naval Warfare (SPAWAR) Systems Center and the Army Research Office (ARO), is reported September 28 in the journal Nature Nanotechnology.

Developed in the 1960s and 1970s, rectennas have operated at wavelengths as short as ten microns, but for more than 40 years researchers have been attempting to make devices at optical wavelengths. There were many challenges: making the antennas small enough to couple optical wavelengths, and fabricating a matching rectifier diode small enough and able to operate fast enough to capture the electromagnetic wave oscillations. But the potential of high efficiency and low cost kept scientists working on the technology.

“The physics and the scientific concepts have been out there,” said Cola. “Now was the perfect time to try some new things and make a device work, thanks to advances in fabrication technology.”

Using metallic multiwall carbon nanotubes and nanoscale fabrication techniques, Cola and collaborators Asha Sharma, Virendra Singh and Thomas Bougher constructed devices that utilize the wave nature of light rather than its particle nature. They also used a long series of tests–and more than a thousand devices–to verify measurements of both current and voltage to confirm the existence of rectenna functions that had been predicted theoretically. The devices operated at a range of temperatures from 5 to 77 degrees Celsius.

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Fabricating the rectennas begins with growing forests of vertically-aligned carbon nanotubes on a conductive substrate. Using atomic layer chemical vapor deposition, the nanotubes are coated with an aluminum oxide material to insulate them. Finally, physical vapor deposition is used to deposit optically-transparent thin layers of calcium then aluminum metals atop the nanotube forest. The difference of work functions between the nanotubes and the calcium provides a potential of about two electron volts, enough to drive electrons out of the carbon nanotube antennas when they are excited by light.

In operation, oscillating waves of light pass through the transparent calcium-aluminum electrode and interact with the nanotubes. The metal-insulator-metal junctions at the nanotube tips serve as rectifiers switching on and off at femtosecond intervals, allowing electrons generated by the antenna to flow one way into the top electrode. Ultra-low capacitance, on the order of a few attofarads, enables the 10-nanometer diameter diode to operate at these exceptional frequencies.

“A rectenna is basically an antenna coupled to a diode, but when you move into the optical spectrum, that usually means a nanoscale antenna coupled to a metal-insulator-metal diode,” Cola explained. “The closer you can get the antenna to the diode, the more efficient it is. So the ideal structure uses the antenna as one of the metals in the diode–which is the structure we made.”

The rectennas fabricated by Cola’s group are grown on rigid substrates, but the goal is to grow them on a foil or other material that would produce flexible solar cells or photodetectors.

Cola sees the rectennas built so far as simple proof of principle. He has ideas for how to improve the efficiency by changing the materials, opening the carbon nanotubes to allow multiple conduction channels, and reducing resistance in the structures.

“We think we can reduce the resistance by several orders of magnitude just by improving the fabrication of our device structures,” he said. “Based on what others have done and what the theory is showing us, I believe that these devices could get to greater than 40 percent efficiency.”

Notes:

This work was supported by the Defense Advanced Research Projects Agency (DARPA), the Space and Naval Warfare (SPAWAR) Systems Center, Pacific under YFA grant N66001-09-1-2091, and by the Army Research Office (ARO), through the Young Investigator Program (YIP), under agreement W911NF-13-1-0491. The statements in this release are those of the authors and do not necessarily reflect the official views of DARPA, SPAWAR or ARO. Georgia Tech has filed international patent applications related to this work under PCT/US2013/065918 in the United States (U.S.S.N. 14/434,118), Europe (No. 13847632.0), Japan (No. 2015-538110) and China (No. 201380060639.2)

CITATION: Asha Sharma, Virendra Singh, Thomas L. Bougher and Baratunde A. Cola, “A carbon nanotube optical rectenna,” (Nature Nanotechnology, 2015). http://dx.doi.org/10.1038/nnano.2015.220

ULVAC, Inc. announced that it has recently developed and started selling the ECO-SHOCK ES4A, a power saving accessory for dry vacuum pumps that can reduce power consumption substantially by attaching to the dry vacuum pump exhaust line.

Dry vacuum pumps consume particularly large amounts of electricity in production lines. Therefore, it is important to reduce their power consumption. ULVAC has already released the ECO-SHOCK ES10, which reduces power consumption when attached to a dry vacuum pump exhaust line. However, it has been difficult to reduce power consumption of dry vacuum pumps that are used for frequent pumping down of loading/unloading chambers of vacuum systems and use large amounts of sealing gas. To resolve this difficulty, ULVAC has launched the ECO-SHOCK ES4A.

Features:

  • The ECO-SHOCK ES4A makes possible a substantial reduction in power consumption of dry vacuum pumps used for the following purposes: Dry vacuum pumps that are used for frequent pumping down of loading/unloading chambers; dry vacuum pumps that use large amounts of sealed gas.
  • There is no degradation of pumping speed because any control such as rotation speed adjustment is required when attaching it to dry vacuum pump. Also, even if the ES4A was broken down, there is no decrease in performance of dry vacuum pump.

The ECO-SHOCK ES4A can be attached to dry pump exhaust lines that have already been installed. It can be used to pump down air, nitrogen, argon and other stable and safe gases. However, it cannot be used in applications such as flammable, burn ability and toxic gas exhausts, or for solid/fluid suction. It can also be used for a dry vacuum pump, which does not affect performance when making exhaust port under vacuum.

X-FAB Silicon Foundries, a More-than-Moore foundry, today announced new transistors that have drastically reduced flicker noise on its mixed-signal 0.35µm and 0.18µm CMOS process platforms. Flicker noise in CMOS MOSFETs has been reduced in both the n-channel device in the XH035 0.35µm process and the p-channel device in the XH018 0.18µm process by a factor of five, thereby setting the industry benchmark.

The new XH035 3.3V n-channel MOSFET has a lower flicker noise comparable to that of its companion XH035 3.3V p-channel MOSFET, when referenced to its input, and maintains the standard n-channel MOSFET’s threshold voltage and current drive capability. Using both types of low-noise transistors it is possible to design improved, lower-noise amplifier variants with a significantly higher signal-to-noise ratio (SNR), and to make circuits that are more compact with better performance and are more cost-effective. Similarly, the new 0.18µm process XH018 3.3V p-channel MOSFET exhibits a much lower flicker noise level than the standard p-channel device. The new low-noise XH018 3.3V p-channel device behavior now is similar to that of the low-noise XH035 3.3V p-channel MOSFET device.

Dr. Jens Kosch, Chief Technical Officer at X-FAB, explained the significance and cost-effectiveness of the new low-noise CMOS transistors: “For years X-FAB has set the benchmark for low-noise transistors with our p-channel MOSFET transistor in our 0.35µm technology. When our customers asked for additional low-noise transistors, we developed our XH035 low-noise n-channel MOS transistor (NMOS) and our XH018 p-channel MOS transistor. The combination of the complementary XH035 n- and p-channel transistors offers designers more freedom in their circuit designs. No longer are they limited to only a low-noise p-channel device, and they benefit from having no additional mask layer expense. In addition, the new XH018 p-channel device makes it possible to develop noise-critical designs for 0.18µm processes.”

The new 0.35µm lower-noise n-channel transistor and its low-noise p-channel counterpart, integrated within the XH035 process design kit (PDK), are available immediately for new designs. Noise parameters are included within the device models to facilitate an accurate simulation of the noise behavior of a circuit prior to its actual use. For the 0.18µm XH018 process, the new lower-noise 3.3V p-channel MOSFET will become available for new designs in November 2015.

United Microelectronics Corporation (UMC), a global semiconductor foundry, today announced that it has entered high volume production for touch IC applications manufactured on UMC’s 0.11um eFlash process. The specialized technology, first introduced by UMC in late 2012 as the foundry industry’s first, true 12-volt aluminum back-end-of-line (BEoL) process, is developed for next generation touch controller IC and IoT applications. Compared to 0.18um, 0.11um provides smaller and faster logic devices for higher performance, while enabling the integration of higher density embedded Flash and SRAM for use in microcontrollers for touch-screen products of all sizes.

Kurt Huang, senior director of corporate marketing at UMC, said, “Touch panels have become the predominant interface used for today’s electronics. A key advantage of UMC’s touch platform solution is that we provide the 0.11um eFlash with proprietary flash macro design services to IC designers. We also offer the best cost vs. performance by incorporating an aluminum BEoL process to serve the highly competitive touch IC market. In addition, just like our 0.18um eFlash, support for true 12-volt power meets the high signal-to-noise ratio (SNR) requirements needed for today’s larger touch screens and ‘hovering’ applications used during web navigation on touch surfaces.”

UMC’s 0.11um touch IC platform delivers more than three times the SNR improvement over today’s widely used 3.3V solution, allowing IC designers to create a new generation of enhanced touch interface products. The foundry has extensive experience manufacturing touch controller ICs, with more than 30 touch customers in production at the foundry and over 40 million touch ICs shipped per month. The 0.11um process is developed on 8-inch manufacturing using the most aggressive aluminum BEoL technology, allowing touch IC designers to enjoy lower NRE and related costs to increase market competitiveness. UMC also provides in-house flash IP to speed time-to-market and facilitate customization to address evolving market trends. An ultra-low leakage (uLL) process is currently being developed to further reduce core current on devices and SRAM by up to four times.

Alcatel-Lucent has announced the acquisition of Mformation, a leading provider of mobile and “Internet of Things” security and device management solutions for mobile operators, service providers and enterprises. Terms of the deal were not disclosed.

Mformation, headquartered in Woodbridge, NJ, will be incorporated into Alcatel-Lucent’s IP Platforms organization, providing service providers and enterprises with a secure, scalable, application-independent IoT security and control platform for use across multiple industries including automotive, healthcare, utilities, manufacturing and the digital home.

Additionally, Mformation’s software products will extend and enhance the capabilities of Alcatel-Lucent’s Motive Customer Experience Management (CEM) solution to provide service providers with an end-to-end, integrated and cost-efficient device management solution across home, mobile and enterprise networks. These end-to-end capabilities can address the increasing importance of the effective management and security for the 70 billion devices expected to connect to the Internet by 2020, and will simplify the management of converged networks expected to grow exponentially with the implementation of 5G.

Security concerns are on the rise as networks become increasingly virtualized, wireless devices become mainstay components of complex machines pervasive in every aspect of life, and unmanned connected devices begin to outnumber the world’s population ten fold. In the past six months alone more than 50 million IoT devices have been hacked or recalled. The combination of Alcatel-Lucent’s Motive portfolio and Mformation together will allow network operators to manage any endpoint (or gateway), establishing an end-to-end IoT “chain of trust” built on industry best practices for authentication and data and network security.

STMicroelectronics, a global semiconductor company, and a manufacturer and supplier of MEMS for consumer and mobile applications, has introduced a six-axis motion-sensing device fully supporting image stabilization in smartphones, tablets, and digital still cameras. The latest addition to ST’s iNEMO (TM) range of inertial motion sensors, the LSM6DS3H combines a 3-axis gyroscope, a 3-axis accelerometer, and an ultra-low-power processing circuit in a System-in-Package solution that offers the industry’s lowest power consumption and smallest package size.

Electronic Image Stabilization (EIS) and Optical Image Stabilization (OIS) techniques help minimize image blurring caused by camera motion while the snapshot is being captured. Initially developed for professional cameras, these techniques are being increasingly deployed in smartphones and tablets, where blurring is most likely to occur when the user takes a photograph with an outstretched arm.

Key technical features of the LSM6DS3H include:

  • Ultra-low power consumption of the motion sensors (0.85mA in normal mode, 0.4mA in low power mode), allowing the gyroscope to be “always on”;
  • Accelerometer power consumption in low-power mode down to 10 uA, 60% less compared with the previous-generation 6-axis module (LSM6DS3);
  • Supports both EIS and OIS applications with a choice of I2C or SPI for the primary interface and a dedicated auxiliary SPI interface to the camera module;
  • Compact package measuring 2.5mm X 3mm X 0.83mm;
  • Accelerometer ODR (Output Data Rate) up to 6.66 kHz, Gyroscope ODR up to 3.33kHz;
  • Smart FIFO for dynamic data batching and smarter power management: 4kbyte FIFO + 4kbyte flexible (FIFO or programmable);
  • Full-scale acceleration range +/- 2 / +/- 4 / +/- 8 / +/- 16g;
  • Full-scale angular rate range +/- 125 / +/- 245 / +/- 500 / +/- 1000 / +/- 2000 dps;
  • Supply voltage from 1.71 to 3.6V, independent IOs supply down to 1.62V;
  • SPI/I2C serial interface data synchronization feature;
  • Embedded temperature sensor.

“Very often people use the phone camera with outstretched arms, which can degrade the image quality,” said Andrea Onetti, General Manager, Volume MEMS and Analog Division, STMicroelectronics. “Our new multi-function motion sensor sets to minimize blurring in any photo situation while extending battery life because of the ultra-low power consumption.”

In what may be a first for the MEMS industry, CEA-Leti has manufactured micro-accelerometers on 300mm wafers, a development that could lead to significantly lower MEMS manufacturing costs.

“With more than 200 people involved on micro-systems R&D, Leti is one of the world’s leading research institutes on MEMS, and this demonstration that our 200mm MEMS platform is now compatible with 300mm wafer fabrication shows a significant opportunity to cut MEMS production costs,” said Leti CEO Marie Semeria. “This will be especially important with the worldwide expansion of the Internet of Things and continued growing demand for MEMS in mobile devices.”

Leti is a pioneer and leader in MEMS research and development for sensors and actuators. Building on more than 30 years of MEMS R&D, Leti continues to focus on innovative sensor technologies.

The most advanced is its M&NEMS technology platform based on detection by piezo-resistive silicon nanowires, which reduce sensor size and improve performances of multi-axis sensors. Leti’s inertial-sensor manufacturing concept enables the design and fabrication of combo sensors, such as three-axis accelerometers, three-axis gyroscopes and three-axis magnetometers on the same chip.  This is a key component for Internet of Things (IoT) applications.

Leti’s M&NEMS concept, developed with 200mm technology, is currently being transferred to an industrial partner. Demonstration of this technology on 300mm wafers has shown very promising results.

In addition to lowering costs, manufacturing MEMS with 300mm technology enables 3D integration using MEMS CMOS processes in more advanced nodes than on 200mm, and the use of 3D through-silicon-vias (TSV), which is already available in 300mm technology.

Jean-René Lèquepeys, head of Leti’s Silicon Components Division, will present the latest results in Leti’s MEMS technology R&D at the European MEMS Summit 2015, Sept. 17-18 in Milan, Italy.

Energy storage players are eyeing emerging opportunities in bioelectronics as wearable, implantable and other medical devices create energy demands and design requirements beyond conventional batteries, according to Lux Research.

Existing battery solutions barely satisfy the demands for increased functionality and power in existing medical devices and may have slowed the shift toward personalized health care in many areas of medicine.

“Developers of energy storage must understand the required application-specific optimization of batteries, based on performance and safety, and desired form factors,” said Milos Todorovic, Lux Research Analyst and lead author of the report titled, “Powerful Medicine: Opportunities for Pairing New Bioelectronics with Innovative Energy Storage.”

“Winning in this race will require a thorough understanding of key technical requirements as well as the knowledge of regulatory and safety implications of bringing new energy storage to the fore,” he added.

Lux Research analysts identified key demands arising from the novel medical technologies, and evaluated energy storage companies on the proprietary Lux Innovation Grid. Among their findings:

  • Li-ion batteries will make rapid strides. Newer lithium-ion batteries will advance both safety and performance, besides extending life span. Compared with today’s best batteries, those that will become available in 2025 will double energy density to over 1,200 Wh/L, more than double specific energy to over 400 Wh/kg, quintuple life span to over 25 years and raise safety standards to “excellent,” from “mediocre to satisfactory.”
  • EaglePitcher, WiTricity, FlexEI are standout companies. On the Lux Innovation Grid, three companies offering diverse technologies stood out as “dominant” in the upper right quadrant. EaglePitcher’s batteries are entrenched in energy storage niches, including military, medical and aerospace; WiTricity leads with its wireless charging technology, a potential life-saving feature; and FlexEI offers contract engineering for custom batteries, with form factors including thin-film and cylindrical cells.
  • Current Li-ion developers lag. On the Lux Innovation Grid, Li-ion developers are clustered mostly in the lower-right “undistinguished” corner, with mediocre technology and business execution, highlighting the need to push beyond today’s incumbent technologies. To succeed, Li-ion battery companies would need to develop flexible form factors without sacrificing energy stored, sharply raise energy density with a push towards next-generation designs like ceramic or polymer solid-state electrolytes, and also enhance safety.

The report titled, “Powerful Medicine: Opportunities for Pairing New Bioelectronics with Innovative Energy Storage,” is part of the Lux Research BioElectronics Intelligence and the Lux Research Energy Storage Intelligence services.

BeSpoon SAS today launched BeSpoon Sport Edition, an ultra-precise position-tracking system that allows teams to measure and analyze player movement in three dimensions and provide immediate feedback to improve performance.

Designed for professional and other high-level competitive teams, BeSpoon Sport Edition generates key metrics such as distance run faster than 7km/h, average acceleration and jump height in real time. These next-generation statistics immediately give coaches, players and fans new insight into the action on the field.

BeSpoon’s impulse radio ultra-wideband (IR-UWB) technology, which can track individuals’ or objects’ positions and movements to within a few inches, measures the time of flight of an UWB signal, and is impervious to interference by nearby people or objects. The technology is ideal for tracking movement both in terms of accuracy and robustness.

BeSpoon Sport Edition, which combines BeSpoon’s technology and SportTracking Fusion software, is being used by Chambery Savoie Handball, a professional team in France. BeSpoon recently uploaded a YouTube video showing its tracking engine at work to improve player performance.

Installed in Le Phare, the team’s 4,500-seat indoor arena, the system instantaneously computes the position of players, who are wearing tiny chips, in three dimensions and feeds the SportTracking Fusion engine. Using portable computers near the team’s bench, coaches and players are able to optimize training and step up their game. The system also generates player statistics during games for fans to view.

“It was amazing to see how quickly the tracking system was implemented by our team,” said Laurent Munier, general manager of Chambery Savoie Handball. “After a few minutes, our athletes and coaches figured out how they could take advantage of the immediate feedback and engaged with the tool to improve their performance.”

“BeSpoon Sport Edition is a new, practical and affordable way to apply the benefits of innovative microelectronics in everyday activities,” said BeSpoon CEO Jean-Marie André. “The systems’ next-generation data can dramatically improve athletes’ performance and enhance sport-fans’ experience with real-time statistics.

“In addition, sports is just one example of the many domains where inch-level tracking technology can bring disruptive changes. In logistics, our customers are now able to automate challenging and expensive operations, as well as improve security in the warehouse. Retail stores are implementing location-based operation, a radical improvement in the way stores are managed daily. Defense organizations are using the technology for location tracking, which drastically enhances soldier safety. These are just a few areas where precise-location has already started to change the game. Industry, health care and museums are next on the list.”

BeSpoon, a fabless semiconductor company that also offers system-level products and support, solved the problem of indoor position tracking with a proprietary chip that can track items or individuals to within a few centimeters. Developed in cooperation with CEA-Leti in Grenoble, France, the location process measures the time of flight of an ultra wide band (UWB) radio signal with a precision of 125 picoseconds, opening a vast range of opportunities for asset monitoring, precise indoor location in professional and consumer environments.

Engineers at the University of California, San Diego, have developed a mouth guard that can monitor health markers, such as lactate, cortisol and uric acid, in saliva and transmit the information wirelessly to a smart phone, laptop or tablet.

mems mouth guard

The mouth guard sensor offers an easy and reliable way to monitor uric acid levels in human saliva. Credit: Jacobs School of Engineering, UC San Diego

The technology, which is at a proof-of-concept stage, could be used to monitor patients continuously without invasive procedures, as well as to monitor athletes’ performance or stress levels in soldiers and pilots. In this study, engineers focused on uric acid, which is a marker related to diabetes and to gout. Currently, the only way to monitor the levels of uric acid in a patient is to draw blood.

The team, led by nanoengineering professor Joseph Wang and electrical engineering professor Patrick Mercier, both from the University of California, San Diego, describes the mouth guard’s design and performance this month in the journal Biosensors and Bioelectronics.

“The ability to monitor continuously and non-invasively saliva biomarkers holds considerable promise for many biomedical and fitness applications,” said Wang.

Testing the sensors

In this study, researchers showed that the mouth guard sensor could offer an easy and reliable way to monitor uric acid levels. The mouth guard has been tested with human saliva but hasn’t been tested in a person’s mouth.

Researchers collected saliva samples from healthy volunteers and spread them on the sensor, which produced readings in a normal range. Next, they collected saliva from a patient who suffers from hyperuricemia, a condition characterized by an excess of uric acid in the blood. The sensor detected more than four times as much uric acid in the patient’s saliva than in the healthy volunteers.

The patient also took Allopurinol, which had been prescribed by a physician to treat their condition. Researchers were able to document a drop in the levels of uric acid over four or five days as the medication took effect. In the past, the patient would have needed blood draws to monitor levels and relied instead on symptoms to start and stop his medication.

Fabrication and design

Wang’s team created a screen-printed sensor using silver, Prussian blue ink and uricase, an enzyme that reacts with uric acid. Because saliva is extremely complex and contains many different biomarkers, researchers needed to make sure that the sensors only reacted with the uric acid. Nanoengineers set up the chemical equivalent of a two-step authentication system. The first step is a series of chemical keyholes, which ensures that only the smallest biochemicals get inside the sensor. The second step is a layer of uricase trapped in polymers, which reacts selectively with uric acid. The reaction between acid and enzyme generates hydrogen peroxide, which is detected by the Prussian blue ink. That information is then transmitted to an electronic board as electrical signals via metallic strips that are part of the sensor.

The electronic board, developed by Mercier’s team, uses small chips that sense the output of the sensors, digitizes this output and then wirelessly transmits data to a smart phone, tablet or laptop. The entire electronic board occupies an area slightly larger than a U.S. penny.

Next steps 

The next step is to embed all the electronics inside the mouth guard so that it can actually be worn. Researchers also will have to test the materials used for the sensors and electronics to make sure that they are indeed completely biocompatible. The next iteration of the mouth guard is about a year out, Mercier estimates.

“All the components are there,” he said. “It’s just a matter of refining the device and working on its stability.”

Wang and Mercier lead the Center for Wearable Sensors at UC San Diego, which has made a series of breakthroughs in the field, including temporary tattoos that monitor glucose, ultra-miniaturized energy-processing chips and pens filled with high-tech inks for Do It Yourself chemical sensors.

“UC San Diego has become a leader in the field of wearable sensors,” said Mercier.