Tag Archives: letter-mems-tech

NUST MISIS scientists jointly with an international group of scientists have managed to develop a composite material that has the best piezoelectric properties today. The research results were published in Scientific Reports journal.

Topography (a), PFM images of a pristine state (b) and after poling by +/?60V (c). Credit: ©NUST MISIS

Topography (a), PFM images of a pristine state (b) and after poling by +/?60V (c). Credit: ©NUST MISIS

Piezoelectrics are one of the world`s most amazing materials. It is possible to literally squeeze electricity from them. That is, an electric charge appears at the time of the material`s compression (or stretching). This is called the piezoelectric effect. Piezoelectric materials can be applied in many fields – from pressure sensors and sensitive elements of a microphone to the controller ink pressing in ink-jet printers and quartz resonators.

Lead zirconate titanate is one of the most popular piezoelectric materials. However, it has several disadvantages: it is heavy and inflexible. Additionally, lead production often causes great harm to the environment. That is why scientists are constantly looking for new materials with low lead content as well as with less weight and greater flexibility. In particular, the creation of flexible piezoelectric materials (while maintaining the key properties) would greatly expand piezoelectric materials` possibilities both as acoustic membrane and as pressure sensors.

An international team of scientists from the University of Duisburg-Essen (Germany), NUST MISIS, National Research Tomsk State University and the National Research University of Electronic Technology, working with the financial support of the Russian Science Foundation (grant 16-19-10112), has managed to create such a material and analyze its properties. For this, the nanoparticles consisting of titanate-zicronate barium-lead were placed in a complex polymer consisting of vinylidene disluoride and trifluoroethylene. By diversifying the composition of the components, scientists were able to get the most ideal composite.

The Russian-German group of scientists, including Dmitri Kiselev, a Senior Researcher at the NUST MISIS R&D Center for Materials Science & Metallurgy, has managed to create a composite material based on ceramics and organic polymer whose properties exceed today`s best piezoelectric materials. The research’s experimental part was carried out with an atomic-force microscope in the University of Duisburg-Essen (Germany). Thanks to this scientific collaboration, Dmitri Kiselev has gained skills from the world`s best scanning probe microscope, which he can later apply at NUST MISIS», said Alevtina Chernikova, Rector of NUST MISIS.

According to Dmitri Kiselev, the developed material has a very distinct field of application due to its polymer component: «Composite materials based on polymer and classic ferroelectrics, which have piezo- and pyroelectric properties, have a number of advantages compared to pure ceramics: low density, the ability to manufacture parts of any size and shape, mechanical elasticity, stability of electrophysical properties, and the simplicity and relatively low cost of production. Additionally, the synthesized composite has proved to be excellent at high pressures which makes it an excellent base for pressure sensors».

According to Kiselev, to study the composite they had to modify the standard technique which allowed them to correctly visualize the nanoparticles of ceramics in the volume of the polymer matrix: «In order to capture the electrical signal more clearly, we heated our sample in a certain way from room temperature to 60 degrees Celsius. It allowed us to measure the material’s characteristics very qualitatively and reproducibly. Our method will greatly simplify the work of our colleagues in the study of composites, so I hope that it will be in demand among our colleagues microscopists».

«It is now easier for Russian scientists to carry out world-class measurements as the MFP 3D Stand ?lone (Asylum Research) microscope is now available at the NUST MISIS Center for Collaborative Use, hence why we are now actively collaborating with several institutes from the Russian Academy of Sciences as well as other Moscow universities», Kiselev concluded.

 

Leti Chief Scientist Barbara De Salvo will help kick off ISSCC 2018 with an opening-day presentation calling for radically new, digital-communication architecture for the Internet of Things in which “a great deal of analytics processing occurs at the edge and at the end devices instead of in the Cloud.”

Delivering a keynote talk during the Feb. 12 plenary session that formally opens the conference, De Salvo will note that the architecture will include human-brain inspired hardware coupled to new computing paradigms and algorithms that “will allow for distributed intelligence over the whole IoT network, all-the-way down to ultralow-power end-devices.”

“We are entering a new era where artificial-intelligence systems are … shaping the future world,” says De Salvo, who also is Leti’s scientific director. “With the end of Moore’s Law in sight, transformative approaches are needed to address the enduring power-efficiency issues of traditional computing architectures.”

Leti paper and demo present technology for ‘extracting energy from shocks’

In addition, Leti scientists will present a paper on and a demonstration of real-life applications of piezoelectric energy harvesting, which converts mechanical energy, such as vibration and shocks, into electrical energy. The demo at Demonstration Session 1, 8.8, from 5-7 p.m., Feb. 12, in Golden Gate Hall of the San Francisco Marriott Marquis Hotel, will show a new technology for extracting energy from shocks. The demo shows an energy-autonomous temperature sensor node powered by the proposed harvesting circuit in an automotive environment. The system is able to harvest enough energy to sense temperature and transmit it wirelessly with a few mechanical pulses.

 

The demonstration is based on the paper, “A 30nA Quiescent 80nW-to-14mW Power-Range Shock-Optimized SECE-Based Piezoelectric Harvesting Interface with 420% Harvested-Energy Improvement”. The paper will be presented at 11:15 a.m., Feb. 13, during Session 8 on Wireless Power and Harvesting. The authors propose an efficient electrical interface to maximize the energy extraction from a piezoelectric energy harvester. The novelty of the approach is to adapt the strategy to sporadic mechanical shocks, usually found in real-environments, instead of periodic vibrations. The circuit allows a self-starting operation and energy-aware sequencing with nanowatt power consumption. Compared to a well-established interface, the proposed approach presents 4x energy harvesting capability.

MACOM Technology Solutions Holdings, Inc. (NASDAQ: MTSI) (“MACOM”), a supplier of high-performance RF, microwave, millimeterwave and lightwave semiconductor products, and STMicroelectronics (NYSE: STM) today announced an agreement to develop GaN (Gallium Nitride) on Silicon wafers to be manufactured by ST for MACOM’s use across an array of RF applications. While expanding MACOM’s source of supply, the agreement also grants to ST the right to manufacture and sell its own GaN on Silicon products in RF markets outside of mobile phone, wireless basestation and related commercial telecom infrastructure applications.

Through this agreement, MACOM expects to access increased Silicon wafer manufacturing capacity and improved cost structure that could displace incumbent Silicon LDMOS and accelerate the adoption of GaN on Silicon in mainstream markets. ST and MACOM have been working together for several years to bring GaN on Silicon production up in ST’s CMOS wafer fab. As currently scheduled, sample production from ST is expected to begin in 2018.

“This agreement punctuates our long journey of leading the RF industry’s conversion to GaN on Silicon technology. To date, MACOM has refined and proven the merits of GaN on Silicon using rather modest compound semiconductor factories, replicating and even exceeding the RF performance and reliability of expensive GaN on SiC alternative technology,” said John Croteau, President and CEO, MACOM. “We expect this collaboration with ST to bring those GaN innovations to bear in a Silicon supply chain that can ultimately service the most demanding customers and applications.”

“ST’s scale and operational excellence in Silicon wafer manufacturing aims to unlock the potential to drive new RF power applications for MACOM and ST as it delivers the economic breakthroughs necessary to expand the market for GaN on Silicon,” said Marco Monti, President of the Automotive and Discrete Product Group, STMicroelectronics. “While expanding the opportunities for existing RF applications is appealing, we’re even more excited about using GaN on Silicon in new RF Energy applications, especially in automotive applications, such as plasma ignition for more efficient combustion in conventional engines, and in RF lighting applications, for more efficient and longer-lasting lighting systems.”

“Once the $0.04/watt barrier for high power RF semiconductor devices is crossed, significant opportunities for the RF energy market may open up,” said Eric Higham, Director Advanced Semiconductor Applications Service at Strategy Analytics. Higham continued, “Potential RF energy device shipments could be in the hundreds of millions for applications including commercial microwave cooking, automotive lighting and ignition, and plasma lighting, with sales reaching into the billions of dollars.”

Texas Instruments (TI) (NASDAQ: TXN) today introduced the industry’s smallest operational amplifier (op amp) and low-power comparators at 0.64 mm2. As the first amplifiers in the compact X2SON package, the TLV9061 op amp and TLV7011 family of comparators enable engineers to reduce their system size and cost, while maintaining high performance in a variety of Internet of Things (IoT), personal electronics and industrial applications, including mobile phones, wearables, optical modules, motor drives, smart grid and battery-powered systems.

With a high gain bandwidth (GBW) of 10 MHz, fast slew rate at 6.5 V/µs and low-noise spectral density of 10 nV/√Hz, the TLV9061 op amp is designed for use in wide-bandwidth, high-performance systems. The TLV7011 family of nanopower comparators delivers a faster response time with propagation delays down to 260 ns, while consuming 50 percent less power than competitive comparators. Additionally, both devices support rail-to-rail inputs with low-voltage operation down to 1.8 V, enabling ease-of-use in battery-powered applications.

Achieve high performance in tiny spaces with the TLV9061 operational amplifier

  • Reduces system size and cost: In addition to its tiny size, the TLV9061 op amp also features integrated EMI filtering inputs. This helps provide resilient performance for systems prone to RF noise, while significantly reducing the need for external discrete circuitry.
  • Greater DC accuracy: Two times lower offset drift and typical input bias across a full temperature range, -40 to 125 degrees Celsius, creates a more precise signal chain solution compared to other small devices.

Lower power, faster response with the tiny TLV7011 family of comparators

  • Smaller footprint, extra features: No phase reversal and integrated internal hysteresis for overdriven inputs increase design flexibility and reduce the need for external components.
  • Fifty percent less power consumption: With power as low as 335 nA and fast propagation delay down to 260 ns, the TLV7011 family of nanopower comparators enable low-power systems to monitor signals and respond quickly.

These new devices join TI’s small-size amplifier portfolio which enables engineers to design smaller systems, while maintaining high performance, with industry-leading package options and many of the world’s smallest op amps and comparators.

Tools and support to speed design
Designers can download the TINA-TI™ SPICE model to simulate their designs and predict circuit behavior when using the TLV9061 op amp and TLV7011 family of comparators. Engineers can jump-start their small brushed DC servo drive designs using the TLV9061 op amp with the 10.8-V/15-W, >90% Efficiency, 2.4-cm2, Power Stage Reference Design. Also, they can quickly and easily evaluate the TLV7011 comparators with the DIP adapter evaluation module, available today for US$5.00 from the TI store and authorized distributors.

Package, availability and pricing
Preproduction samples of the TLV9061 op amp and volume quantities of the TLV7011 family of comparators are now available through the TI store and authorized distributors in a 5-pin extra small outline no-lead (X2SON) package, measuring 0.8 mm x 0.8 mm x 0.4 mm. Pricing starts at US$0.19 and US$0.25 in 1,000-unit quantities, respectively. Learn more about the family of comparators in the table below.

Product

Supply
voltage (Vcc)

DC input
offset (Vios)

Propagation
delay (tpd)

Supply
current (Icc)

TLV7011

1.6 – 5.5 V

0.5 mV

260 ns

5 µA

TLV7021

1.6 – 5.5 V

0.5 mV

260 ns

5 µA

TLV7031

1.6 – 6.5 V

0.1 mV

3 µs

335 nA

TLV7041

1.6 – 6.5 V

0.1 mV

3 µs

335 nA

When it comes to processing power, the human brain just can’t be beat.

Packed within the squishy, football-sized organ are somewhere around 100 billion neurons. At any given moment, a single neuron can relay instructions to thousands of other neurons via synapses — the spaces between neurons, across which neurotransmitters are exchanged. There are more than 100 trillion synapses that mediate neuron signaling in the brain, strengthening some connections while pruning others, in a process that enables the brain to recognize patterns, remember facts, and carry out other learning tasks, at lightning speeds.

Researchers in the emerging field of “neuromorphic computing” have attempted to design computer chips that work like the human brain. Instead of carrying out computations based on binary, on/off signaling, like digital chips do today, the elements of a “brain on a chip” would work in an analog fashion, exchanging a gradient of signals, or “weights,” much like neurons that activate in various ways depending on the type and number of ions that flow across a synapse.

In this way, small neuromorphic chips could, like the brain, efficiently process millions of streams of parallel computations that are currently only possible with large banks of supercomputers. But one significant hangup on the way to such portable artificial intelligence has been the neural synapse, which has been particularly tricky to reproduce in hardware.

Now engineers at MIT have designed an artificial synapse in such a way that they can precisely control the strength of an electric current flowing across it, similar to the way ions flow between neurons. The team has built a small chip with artificial synapses, made from silicon germanium. In simulations, the researchers found that the chip and its synapses could be used to recognize samples of handwriting, with 95 percent accuracy.

The design, published today in the journal Nature Materials, is a major step toward building portable, low-power neuromorphic chips for use in pattern recognition and other learning tasks.

The research was led by Jeehwan Kim, the Class of 1947 Career Development Assistant Professor in the departments of Mechanical Engineering and Materials Science and Engineering, and a principal investigator in MIT’s Research Laboratory of Electronics and Microsystems Technology Laboratories. His co-authors are Shinhyun Choi (first author), Scott Tan (co-first author), Zefan Li, Yunjo Kim, Chanyeol Choi, and Hanwool Yeon of MIT, along with Pai-Yu Chen and Shimeng Yu of Arizona State University.

Too many paths

Most neuromorphic chip designs attempt to emulate the synaptic connection between neurons using two conductive layers separated by a “switching medium,” or synapse-like space. When a voltage is applied, ions should move in the switching medium to create conductive filaments, similarly to how the “weight” of a synapse changes.

But it’s been difficult to control the flow of ions in existing designs. Kim says that’s because most switching mediums, made of amorphous materials, have unlimited possible paths through which ions can travel — a bit like Pachinko, a mechanical arcade game that funnels small steel balls down through a series of pins and levers, which act to either divert or direct the balls out of the machine.

Like Pachinko, existing switching mediums contain multiple paths that make it difficult to predict where ions will make it through. Kim says that can create unwanted nonuniformity in a synapse’s performance.

“Once you apply some voltage to represent some data with your artificial neuron, you have to erase and be able to write it again in the exact same way,” Kim says. “But in an amorphous solid, when you write again, the ions go in different directions because there are lots of defects. This stream is changing, and it’s hard to control. That’s the biggest problem — nonuniformity of the artificial synapse.”

A perfect mismatch

Instead of using amorphous materials as an artificial synapse, Kim and his colleagues looked to single-crystalline silicon, a defect-free conducting material made from atoms arranged in a continuously ordered alignment. The team sought to create a precise, one-dimensional line defect, or dislocation, through the silicon, through which ions could predictably flow.

To do so, the researchers started with a wafer of silicon, resembling, at microscopic resolution, a chicken-wire pattern. They then grew a similar pattern of silicon germanium — a material also used commonly in transistors — on top of the silicon wafer. Silicon germanium’s lattice is slightly larger than that of silicon, and Kim found that together, the two perfectly mismatched materials can form a funnel-like dislocation, creating a single path through which ions can flow.

The researchers fabricated a neuromorphic chip consisting of artificial synapses made from silicon germanium, each synapse measuring about 25 nanometers across. They applied voltage to each synapse and found that all synapses exhibited more or less the same current, or flow of ions, with about a 4 percent variation between synapses — a much more uniform performance compared with synapses made from amorphous material.

They also tested a single synapse over multiple trials, applying the same voltage over 700 cycles, and found the synapse exhibited the same current, with just 1 percent variation from cycle to cycle.

“This is the most uniform device we could achieve, which is the key to demonstrating artificial neural networks,” Kim says.

Writing, recognized

As a final test, Kim’s team explored how its device would perform if it were to carry out actual learning tasks — specifically, recognizing samples of handwriting, which researchers consider to be a first practical test for neuromorphic chips. Such chips would consist of “input/hidden/output neurons,” each connected to other “neurons” via filament-based artificial synapses.

Scientists believe such stacks of neural nets can be made to “learn.” For instance, when fed an input that is a handwritten ‘1,’ with an output that labels it as ‘1,’ certain output neurons will be activated by input neurons and weights from an artificial synapse. When more examples of handwritten ‘1s’ are fed into the same chip, the same output neurons may be activated when they sense similar features between different samples of the same letter, thus “learning” in a fashion similar to what the brain does.

Kim and his colleagues ran a computer simulation of an artificial neural network consisting of three sheets of neural layers connected via two layers of artificial synapses, the properties of which they based on measurements from their actual neuromorphic chip. They fed into their simulation tens of thousands of samples from a handwritten recognition dataset commonly used by neuromorphic designers, and found that their neural network hardware recognized handwritten samples 95 percent of the time, compared to the 97 percent accuracy of existing software algorithms.

The team is in the process of fabricating a working neuromorphic chip that can carry out handwriting-recognition tasks, not in simulation but in reality. Looking beyond handwriting, Kim says the team’s artificial synapse design will enable much smaller, portable neural network devices that can perform complex computations that currently are only possible with large supercomputers.

“Ultimately we want a chip as big as a fingernail to replace one big supercomputer,” Kim says. “This opens a stepping stone to produce real artificial hardware.”

This research was supported in part by the National Science Foundation.

Silicon chips from STMicroelectronics (NYSE: STM) have enabled new zForce AIR(TM) touch-sensing modules from Neonode (NASDAQ: NEON), the optical sensor technology company.

Neonode’s compact, low-power, and easy-to-use modules add touch interaction to any USB- or I2C-connected object and work with any type of display or surface, including steel, wood, plastic, glass, skin, or even nothing, able to detect touch interactions in mid-air. The innovative approach uses laser-generated infrared light to track touch or gesture control, combining millimeter precision with ultra-fast response. The non-visible-spectrum light doesn’t impact display quality, add glare, or shift colors.

The new Neonode family of touch-sensors uses a programmable mixed-signal custom System-on-Chip (SoC) and an STM32 Arm® Cortex® microcontroller from ST for scanning laser diodes and IR beams to determine the exact position and movements of fingers, hands, or other reflective objects in the light path. Multiple objects can be tracked simultaneously and interpreted as touches or gestures with extreme accuracy: the coordinates are relayed up to 500 times per second with virtually zero delay.

“ST’s leading-edge chip-design capabilities and manufacturing processes have enabled us to build an innovative, high-performance optical-sensor system that is highly complex yet cost-competitive,” said Andreas Bunge, CEO of Neonode. “The advanced mixed-signal SoC and STM32 microcontroller at the heart of our new zForce AIR modules deliver the right combination of touch-control precision in real-time, low power consumption, and configurability.”

“This innovative sensing technology can make any object, surface, or space touch- interactive, bringing complete freedom of design,” said Iain Currie, Vice President North Europe Sales, STMicroelectronics. “Neonode’s decision to use ST technologies confirms our enabling role in the development of advanced applications that break new ground in man-machine interaction.”

Now available for immediate shipment worldwide through Digi-Key Electronics, the zForce AIR(TM) Touch Sensor modules will be displayed on ST’s stand at Embedded World 2018 (February 27 – March 1, Nuremberg).

Leti, a research institute at CEA Tech, has invented a lens-free microscope technology that provides point-of-care diagnosis for spinal meningitis. Outlined in a paper presented at Photonics West, the new technology provides immediate results and eliminates errors in counting white blood cells (leukocytes) in cerebrospinal fluid, which is required to diagnose the infection.

Spinal meningitis is an acute inflammation of the membranes covering the brain and spinal cord, which can be fatal within 24 hours. Until now, early diagnosis of the infection required an operator using an optical microscope to manually count white blood cells in cerebrospinal fluid.

“Until now, this process has been operator dependent, which limits where it can be used and increases the likelihood of errors in counting blood cells,” said Sophie NhuAn Morel, a co-author of the paper. “In our study, manual counts produced different results among five doctors.”

The bulky equipment and intensive human involvement, which can take 5-20 minutes to make a proper cell counting, make the traditional procedure unsuited for point-of-care diagnosis. As a result, meningitis cannot be diagnosed in emergencies or operating rooms, or during routine medical care in developing countries.

Reported in a paper titled “Lens-free Microscopy of Cerebrospinal Fluid for the Laboratory Diagnosis of Meningitis”, Leti’s lens-free, operator-free technology requires fewer than 10 microliters of cerebrospinal fluid to differentiate between white blood cells (leukocytes) and red blood cells (erythrocytes) in a point-of-care environment, using very small equipment.

“Leti’s lens-free technology can count leukocytes and erythrocytes almost in real-time and can be used in many different environments outside the lab,” Morel said.

The lens-free microscope was tested on 200 patients at Marseille Timone Hospital in France to detect or confirm spinal meningitis. A blind lens-free microscopic analysis of 116 cerebrospinal fluid specimens, including six cases of microbiologicallyconfirmed infectious meningitis, yielded a 100 percent sensitivity and a 79 percent specificity. Adapted lens-free microscopy is thus emerging as an operator-independent technique for rapidly counting leukocytes and erythrocytes in cerebrospinal fluid. In particular, this technique is well suited to the rapid diagnosis of meningitis at point-of-care labs.

In the near future, the reconstruction of both the magnitude and phase images from the raw diffraction pattern will allow the classification and numeration of all the blood cells in less than two minutes.

Leti, a technology research institute at CEA Tech, is a global leader in miniaturization technologies enabling smart, energy-efficient and secure solutions for industry.

The research team that announced the first optical rectenna in 2015 is now reporting a two-fold efficiency improvement in the devices — and a switch to air-stable diode materials. The improvements could allow the rectennas – which convert electromagnetic fields at optical frequencies directly to electrical current – to operate low-power devices such as temperature sensors.

Ultimately, the researchers believe their device design – a combination of a carbon nanotube antenna and diode rectifier – could compete with conventional photovoltaic technologies for producing electricity from sunlight and other sources. The same technology used in the rectennas could also directly convert thermal energy to electricity.

Georgia Tech researchers have developed a new higher efficiency rectenna design. Here, the device’s ability to convert blue light to electricity is tested. (Credit: Christopher Moore, Georgia Tech)

Georgia Tech researchers have developed a new higher efficiency rectenna design. Here, the device’s ability to convert blue light to electricity is tested. (Credit: Christopher Moore, Georgia Tech)

“This work takes a significant leap forward in both fundamental understanding and practical efficiency for the optical rectenna device,” said Baratunde Cola, an associate professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “It opens up this technology to many more researchers who can join forces with us to advance the optical rectenna technology to help power a range of applications, including space flight.”

The research was reported January 26 in the journal Advanced Electronic Materials. The work has been supported by the U.S. Army Research Office under the Young Investigator Program, and by the National Science Foundation.

Optical rectennas operate by coupling the light’s electromagnetic field to an antenna, in this case an array of multiwall carbon nanotubes whose ends have been opened. The electromagnetic field creates an oscillation in the antenna, producing an alternating flow of electrons. When the electron flow reaches a peak at one end of the antenna, the diode closes, trapping the electrons, then re-opens to capture the next oscillation, creating a current flow.

The switching must occur at terahertz frequencies to match the light. The junction between the antenna and diode must provide minimal resistance to electrons flowing through it while open, yet prevent leakage while closed.

“The name of the game is maximizing the number of electrons that get excited in the carbon nanotube, and then having a switch that is fast enough to capture them at their peak,” Cola explained. “The faster you switch, the more electrons you can catch on one side of the oscillation.”

To provide a low work function – ease of electron flow – the researchers initially used calcium as the metal in their oxide insulator – metal diode junction. But calcium breaks down rapidly in air, meaning the device had to be encapsulated during operation – and fabricated in a glovebox. That made the optical rectenna both impractical for most applications and difficult to fabricate.

So Cola, NSF Graduate Research Fellow Erik Anderson and Research Engineer Thomas Bougher replaced the calcium with aluminum and tried a variety of oxide materials on the carbon nanotubes before settling on a bilayer material composed of alumina (Al2O3) and hafnium dioxide (HfO2). The combination coating for the carbon nanotube junction, created through an atomic deposition process, provides the quantum mechanical electron tunneling properties required by engineering the oxide electronic properties instead of the metals, which allows air stable metals with higher work functions than calcium to be used.

Rectennas fabricated with the new combination have remained functional for as long as a year. Other metal oxides could also be used, Cola said.

The researchers also engineered the slope of the hill down which the electrons fall in the tunneling process. That also helped increase the efficiency, and allows the use of a variety of oxide materials. The new design also increased the asymmetry of the diodes, which boosted efficiency.

“By working with the oxide electron affinity, we were able to increase the asymmetry by more than ten-fold, making this diode design more attractive,” said Cola. “That’s really where we got the efficiency gain in this new version of the device.”

Optical rectennas could theoretically compete with photovoltaic materials for converting sunlight into electricity. PV materials operate using a different principle, in which photons knock electrons from the atoms of certain materials. The electrons are collected into electrical current.

In September 2015 in the journal Nature Nanotechnology, Cola and Bougher reported the first optical rectenna – a device that had been proposed theoretically for more than 40 years, but never demonstrated.

The early version reported in the journal produced power at microvolt levels. The rectenna now produces power in the millivolt range and conversion efficiency has gone from 10-5 to 10-3 – still very low, but a significant gain.

“Though there still is room for significant improvement, this puts the voltage in the range where you could see optical rectennas operating low-power sensors,” Cola said. “There are a lot of device geometry steps you could take to do something useful with the optical rectenna today in voltage-driven devices that don’t require significant current.”

Cola believes the rectennas could be useful for powering internet of things devices, especially if they can be used to produce electricity from scavenged thermal energy. For converting heat to electricity, the principle is the same as for light – capturing oscillations in a field with the broadband carbon nanotube antenna.

“People have been excited about thermoelectric generators, but there are many limitations on getting a system that works effectively,” he said. “We believe that the rectenna technology will be the best approach for harvesting heat economically.”

In future work, the research team hopes to optimize the antenna operation, and improve their theoretical understanding of how the rectenna works, allowing further optimization. One day, Cola hopes the devices will help accelerate space travel, producing power for electric thrusters that will boost spacecraft.

“Our end game is to see carbon nanotube optical rectennas working on Mars and in the spacecraft that takes us to Mars,” he said.

This work was supported by the Army Research Office under the Young Investigator Program agreement W911NF-13-1-0491 and the National Science Foundation Graduate Research Fellowship program under grant DGE-1650044. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsoring organizations.

Accurately measuring electric fields is important in a variety of applications, such as weather forecasting, process control on industrial machinery, or ensuring the safety of people working on high-voltage power lines. Yet from a technological perspective, this is no easy task.

In a break from the design principle that has been followed by all other measuring devices to date, a research team at TU Wien has now developed a silicon-based sensor as a microelectromechanical system (MEMS). Devised in conjunction with the Department for Integrated Sensor Systems at Danube University Krems, this sensor has the major advantage that it does not distort the very electric field it is currently measuring. An introduction to the new sensor has also been published in the electronics journal “Nature Electronics”.

Tiny new sensor -- compared to a one-cent-coin. Credit: TU Wien

Tiny new sensor — compared to a one-cent-coin. Credit: TU Wien

Distorting measuring devices

“The equipment currently used to measure electric field strength has some significant downsides,” explains Andreas Kainz from the Institute of Sensor and Actuator Systems (Faculty of Electrical Engineering, TU Wien). “These devices contain parts that become electrically charged. Conductive metallic components can significantly alter the field being measured; an effect that becomes even more pronounced if the device also has to be grounded to provide a reference point for the measurement.” Such equipment also tends to be relatively impractical and difficult to transport.

The sensor developed by the team at TU Wien is made from silicon and is based on a very simple concept: small, grid-shaped silicon structures measuring just a few micrometres in size are fixed onto a small spring. When the silicon is exposed to an electric field, a force is exerted on the silicon crystals, causing the spring to slightly compress or extend.

These tiny movements now need to be made visible, for which an optical solution has been designed: an additional grid located above the movable silicon grid is lined up so precisely that the grid openings on one grid are concealed by the other. When an electric field is present, the movable structure moves slightly out of perfect alignment with the fixed grid, allowing light to pass through the openings. This light is measured, from which the strength of the electric field can be calculated by an appropriately calibrated device.

Prototype achieves impressive levels of precision

The new silicon sensor does not measure the direction of the electric field, but its strength. It can be used for fields of a relatively low frequency of up to one kilohertz. “Using our prototype, we have been able to reliably measure weak fields of less than 200 volts per metre,” says Andreas Kainz. “This means our system is already performing at roughly the same level as existing products, even though it is significantly smaller and much simpler.” And there is still a great deal of potential for improvement, too: “Other methods of measurement are already mature approaches – we are just starting out. In future it will certainly be possible to achieve even significantly better results with our microelectromechanical sensor,” adds Andreas Kainz confidently.

Imec today announced that it will demonstrate its very first shortwave infrared (SWIR) range hyperspectral imaging camera at next week’s SPIE Photonics West in San Francisco. The SWIR range provides discriminatory information on all kinds of materials, paving the way to hyperspectral imaging applications in food sorting, waste management, machine vision, precision agriculture and medical diagnostics. Imec’s SWIR camera integrates CMOS-based spectral filters together with InGaAs-based imagers, thus combining the compact and low-cost capabilities of CMOS technology with the spectral range of InGaAs.

Semiconductor CMOS-based hyperspectral imaging filters, as designed and manufactured by imec for the past five years, have been utilized in a manner where they are integrated monolithically onto silicon-based CMOS image sensors, which has a sensitivity range from 400 – 1000 nm visible and near-IR (VNIR) range. However, it is expected that more than half of commercial multi and hyperspectral imaging applications need discriminative spectral data in the 1000 – 1700 nm SWIR range.

“SWIR range is key for hyperspectral imaging as it provides extremely valuable quantitative information about water, fatness, lipid and protein content of organic and inorganic matters like food, plants, human tissues, pharmaceutical powders, as well as key discriminatory characteristics about plastics, paper, wood and many other material properties,” commented Andy Lambrechts, program manager for integrated imaging activities at imec. “It was a natural evolution for imec to extend its offering into the SWIR range while leveraging its core capabilities in optical filter design and manufacturing, as well as its growing expertise in designing compact, low-cost and robust hyperspectral imaging system solutions to ensure this complex technology delivers on its promises.”

Imec’s initial SWIR range hyperspectral imaging cameras feature both linescan ‘stepped filter’ designs with 32 to 100 or more spectral bands, as well as snapshot mosaic solutions enabling the capture of 4 to 16 bands in real-time at video-rate speeds. Cameras with both USB3.0 and GIGE interface are currently in the field undergoing qualification with strategic partners.

“The InGaAs imager industry is at a turning point,” explained Jerome Baron, business development manager of integrated imaging and vision systems at imec. “As the market recognizes the numerous applications of SWIR range hyperspectral imaging cameras beyond its traditional military, remote sensing and scientific niche fields, the time is right for organizations such as imec to enable compact, robust and low-cost hyperspectral imaging cameras in the SWIR range too. Imec’s objectives will be to advance this offering among the most price sensitive volume markets for this technology which include food sorting, waste management and recycling, industrial machine vision, precision agriculture and medical diagnostics.”

The first SWIR range hyperspectral imaging cameras will be demonstrated through Feb. 1 at SPIE Photonics West, booth #4321 in the North Hall of Moscone center in San Francisco.