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Brown University engineers have devised a new method of measuring the stickiness of micro-scale surfaces. The technique, described in Proceedings of the Royal Society A, could be useful in designing and building micro-electro-mechanical systems (MEMS), devices with microscopic moving parts.

With slight modifications, an atomic force microscope could be used to measure adheasion in micro-materials. Credit: Kesari Lab/Brown University. Credit: Kesari Lab/Brown University

With slight modifications, an atomic force microscope could be used to measure adheasion in micro-materials. Credit: Kesari Lab/Brown University. Credit: Kesari Lab/Brown University

At the scale of bridges or buildings, the most important force that engineered structures need to deal with is gravity. But at the scale of MEMS — devices like the tiny accelerometers used in smartphones and Fitbits — the relative importance of gravity decreases, and adhesive forces become more important.

“The main thing that matters at the microscale is what sticks to what,” said Haneesh Kesari, an assistant professor in Brown’s School of Engineering and coauthor of the new research. “If you have parts of your device sticking together that shouldn’t be, it’s not going to work. So in order to design MEMS devices, it helps to have a good way of measuring adhesion in the materials we use.”

That’s what Kesari and two Brown graduate students, Wenqiang Fang and Joyce Mok, looked to accomplish with this new research. Specifically, they wanted to measure a quantity known as “work of adhesion,” which roughly translates into the amount of energy required to separate a unit area of two adhered surfaces.

The key theoretical insight developed in the new study is that thermal vibrations of a microbeam can be used to calculate work of adhesion. That insight suggests a method in which a slightly modified atomic force microscopy (AFM) system can be used to probe adhesive properties.

Standard AFM works a bit like a record player. A cantilever with a sharp needle moves across a target material. A laser shown on the cantilever measures the tiny undulations it makes as it moves along the material’s contours. Those undulations can then be used to map out the material’s surface properties.

Adapting the method to measure adhesion would require simply removing the metal tip from the cantilever, leaving a flat microbeam. That beam can then be lowered onto a target material, where it will adhere. When the cantilever is raised slightly, some portion of the beam will become unstuck, while the rest remains stuck. The unstuck portion of the beam will vibrate ever so slightly. The authors found a way to use the extent of that vibration, which can be measured by an AFM laser, to calculate the length of the unstuck portion, which can in turn be used to calculate the target material’s work of adhesion.

With slight modifications, an atomic force microscope could be used to measure adheasion in micro-materials. Credit: Kesari Lab/Brown University Fang says the technique could be useful in assessing new material coatings or surface textures aimed at alleviating the failure of MEMS devices through sticking.

“Once you have a robust technique for measuring the material’s work of adhesion, then you have a systematic way of evaluating these methods to get the level of adhesion needed for a particular application,” Fang said. “The main advantage to this method is that you don’t need to change a standard AFM setup very much in order to do this.”

The approach is also much simpler than other techniques, according to Mok.

“Previous methods based on interferometry are labor intensive and may require many data points to be taken,” she said. “Our theoretical framework would give a value for the work of adhesion from a single measurement.”

Having demonstrated the technique numerically, Kesari says the next step is to build the system and start collecting some experimental data. He’s hopeful that such a system will aid in pushing the MEMS field forward.

“We have MEMS accelerometers and gyroscopes, but I don’t think the field has quite lived up to its promise yet,” Kesari said. “Part of the reason for that is that people haven’t completely understood adhesion at the small scale. We think that a more robust way of measuring adhesion is the first step towards gaining such an understanding.”

2D materials, which consist of a few layers of atoms, may well be the future of nanotechnology. They offer potential new applications and could be used in small, higher-performance and more energy-efficient devices. 2D materials were first discovered almost 15 years ago, but only a few dozen of them have been synthesized so far. Now, thanks to an approach developed by researchers from EPFL’s Theory and Simulation of Materials Laboratory (THEOS) and from NCCR-MARVEL for Computational Design and Discovey of Novel Materials, many more promising 2D materials may now be identified. Their work was recently published in the journal Nature Nanotechnology, and even got a mention on the cover page.

The first 2D material to be isolated was graphene, in 2004, earning the researchers who discovered it a Nobel Prize in 2010. This marked the start of a whole new era in electronics, as graphene is light, transparent and resilient and, above all, a good conductor of electricity. It paved the way to new applications in numerous fields such as photovoltaics and optoelectronics.

“To find other materials with similar properties, we focused on the feasibility of exfoliation,” explains Nicolas Mounet, a researcher in the THEOS lab and lead author of the study. “But instead of placing adhesive strips on graphite to see if the layers peeled off, like the Nobel Prize winners did, we used a digital method.”

More than 100,000 materials analyzed

The researchers developed an algorithm to review and carefully analyze the structure of more than 100,000 3D materials recorded in external databases. From this, they created a database of around 5,600 potential 2D materials, including more than 1,000 with particularly promising properties. In other words, they’ve created a treasure trove for nanotechnology experts.

To build their database, the researchers used a step-by-step process of elimination. First, they identified all of the materials that are made up of separate layers. “We then studied the chemistry of these materials in greater detail and calculated the energy that would be needed to separate the layers, focusing primarily on materials where interactions between atoms of different layers are weak, something known as Van der Waals bonding,” says Marco Gibertini, a researcher at THEOS and the second author of the study.

A plethora of 2D candidates

Of the 5,600 materials initially identified, the researchers singled out 1,800 structures that could potentially be exfoliated, including 1,036 that looked especially easy to exfoliate. This represents a considerable increase in the number of possible 2D materials known today. They then selected the 258 most promising materials, categorizing them according to their magnetic, electronic, mechanical, thermal and topological properties.

“Our study demonstrates that digital techniques can really boost discoveries of new materials,” says Nicola Marzari, the director of NCCR-MARVEL and a professor at THEOS. “In the past, chemists had to start from scratch and just keep trying different things, which required hours of lab work and a certain amount of luck. With our approach, we can avoid this long, frustrating process because we have a tool that can single out the materials that are worth studying further, allowing us to conduct more focused research.”

It is also possible to reproduce the researchers’ calculations thanks to their software AiiDA, which describes the calculation process for each material discovered in the form of workflows and stores the full provenance of each stage of the calculation. “Without AiiDA, it would have been very difficult to combine and process different types of data,” explains Giovanni Pizzi, a senior researcher at THEOS and co-author of the study. “Our workflows are available to the public, so anyone in the world can reproduce our calculations and apply them to any material to find out if it can be exfoliated.”

Researchers have, for the first time, integrated two technologies widely used in applications such as optical communications, bio-imaging and Light Detection and Ranging (LIDAR) systems that scan the surroundings of self-driving cars and trucks.

In the collaborative effort between the U.S. Department of Energy’s (DOE) Argonne National Laboratory and Harvard University, researchers successfully crafted a metasurface-based lens atop a Micro-Electro-Mechanical System (MEMS) platform. The result is a new infrared light-focusing system that combines the best features of both technologies while reducing the size of the optical system.

This image gives a close-up view of a metasurface-based flat lens (square piece) integrated onto a MEMS scanner. Integration of MEMS devices with metalenses will help manipulate light in sensors by combining the strengths of high-speed dynamic control and precise spatial manipulation of wave fronts.This image was taken with an optical microscope at Argonne's Center for Nanoscale Materials. Credit: Argonne National Laboratory

This image gives a close-up view of a metasurface-based flat lens (square piece) integrated onto a MEMS scanner. Integration of MEMS devices with metalenses will help manipulate light in sensors by combining the strengths of high-speed dynamic control and precise spatial manipulation of wave fronts.This image was taken with an optical microscope at Argonne’s Center for Nanoscale Materials. Credit: Argonne National Laboratory

Metasurfaces can be structured at the nanoscale to work like lenses. These metalenses were pioneered by Federico Capasso, Harvard’s Robert L. Wallace Professor of Applied Physics, and his group at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS). The lenses are rapidly finding applications because they are much thinner and less bulky than existing lenses, and can be made with the same technology used to fabricate computer chips. The MEMSs, meanwhile, are small mechanical devices that consist of tiny, movable mirrors.

“These devices are key today for many technologies. They have become technologically pervasive and have been adopted for everything from activating automobile air bags to the global positioning systems of smart phones,” said Daniel Lopez, Nanofabrication and Devices Group Leader at Argonne’s Center for Nanoscale Materials, a DOE Office of Science User Facility.

Lopez, Capasso and four co-authors describe how they fabricated and tested their new device in an article in APL Photonics, titled “Dynamic metasurface lens based on MEMS technology.” The device measures 900 microns in diameter and 10 microns in thickness (a human hair is approximately 50 microns thick).

The collaboration’s ongoing work to further develop novel applications for the two technologies is conducted at Argonne’s Center for Nanoscale Materials, SEAS and the Harvard Center for Nanoscale Systems, which is part of the National Nanotechnology Coordinated Infrastructure.

In the technologically merged optical system, MEMS mirrors reflect scanned light, which the metalens then focuses without the need for an additional optical component such as a focusing lens. The challenge that the Argonne/Harvard team overcame was to integrate the two technologies without hurting their performance.

The eventual goal would be to fabricate all components of an optical system — the MEMS, the light source and the metasurface-based optics — with the same technology used to manufacture electronics today.

“Then, in principle, optical systems could be made as thin as credit cards,” Lopez said.

These lens-on-MEMS devices could advance the LIDAR systems used to guide self-driving cars. Current LIDAR systems, which scan for obstacles in their immediate proximity, are, by contrast, several feet in diameter.

“You need specific, big, bulky lenses, and you need mechanical objects to move them around, which is slow and expensive,” said Lopez.

“This first successful integration of metalenses and MEMS, made possible by their highly compatible technologies, will bring high speed and agility to optical systems, as well unprecedented functionalities,” said Capasso.

Microsemi Corporation (Nasdaq: MSCC), a provider of semiconductor solutions differentiated by power, security, reliability and performance, today announced the ZL70123, a new radio frequency (RF) base station module for implantable devices utilizing the Medical Implant Communication Service (MICS) RF band. The new module was developed specifically for external controllers and monitors of implantable medical devices.

Microsemi’s ZL70123 base station module, when combined with the company’s existing ZL70323 implant module, provides a complete solution for achieving the highest performance in next-generation medical networks (Med-Net). Both modules are based on the latest generation of Microsemi’s ultralow power (ULP), MICS-band, radio transceiver chip, which has been deployed in more than three million implantable devices over the last 10 years.

Radio frequency technology is increasingly being used in a wide variety of medical implantable applications, including cardiac care, physiological monitoring (e.g., insulin monitoring), pain management and obesity treatments. According to a recent report from P&S Research, the market for active implantable devices, which includes pacemakers, defibrillators and neurostimulators, is expected to grow at an eight percent compound annual growth rate (CAGR) over the next five years, reaching nearly $29 billion by 2023. Microsemi’s new ZL70123 base station module is ideally suited for the unique needs of this growing market.

“RF engineering is a highly specialized discipline, and leveraging Microsemi’s deep expertise in this area allows our customers to reduce design times and minimize project risk,” said Martin McHugh, Microsemi’s product line manager for implant modules. “With Microsemi’s two-module radio link, companies can now focus research dollars and development efforts on new therapies that enable a better quality of life.”

Creating the perfect wearable device to monitor muscle movement, heart rate and other tiny bio-signals without breaking the bank has inspired scientists to look for a simpler and more affordable tool.

Now, a team of researchers at UBC’s Okanagan campus have developed a practical way to monitor and interpret human motion, in what may be the missing piece of the puzzle when it comes to wearable technology.

What started as research to create an ultra-stretchable sensor transformed into a sophisticated inter-disciplinary project resulting in a smart wearable device that is capable of sensing and understanding complex human motion, explains School of Engineering Professor Homayoun Najjaran.

The sensor is made by infusing graphene nano-flakes (GNF) into a rubber-like adhesive pad. Najjaran says they then tested the durability of the tiny sensor by stretching it to see if it can maintain accuracy under strains of up to 350 per cent of its original state. The device went through more than 10,000 cycles of stretching and relaxing while maintaining its electrical stability.

“We tested this sensor vigorously,” says Najjaran. “Not only did it maintain its form but more importantly it retained its sensory functionality. We have further demonstrated the efficacy of GNF-Pad as a haptic technology in real-time applications by precisely replicating the human finger gestures using a three-joint robotic finger.”

The goal was to make something that could stretch, be flexible and a reasonable size, and have the required sensitivity, performance, production cost, and robustness. Unlike an inertial measurement unit–an electronic unit that measures force and movement and is used in most step-based wearable technologies–Najjaran says the sensors need to be sensitive enough to respond to different and complex body motions. That includes infinitesimal movements like a heartbeat or a twitch of a finger, to large muscle movements from walking and running.

School of Engineering Professor and study co-author Mina Hoorfar says their results may help manufacturers create the next level of health monitoring and biomedical devices.

“We have introduced an easy and highly repeatable fabrication method to create a highly sensitive sensor with outstanding mechanical and electrical properties at a very low cost,” says Hoorfar.

To demonstrate its practicality, researchers built three wearable devices including a knee band, a wristband and a glove. The wristband monitored heartbeats by sensing the pulse of the artery. In an entirely different range of motion, the finger and knee bands monitored finger gestures and larger scale muscle movements during walking, running, sitting down and standing up. The results, says Hoorfar, indicate an inexpensive device that has a high-level of sensitivity, selectivity and durability.

Nanoscale light sources and nanoantennas already found a wide range of applications in several areas, such as ultra compact pixels, optical detection or telecommunications. However, the fabrication of nanostructure-based devices is rather complicated since the materials typically used have a limited luminescence efficiency. What is more, single quantum dots or molecules usually emit light non-directionally and weakly. An even more challenging task is placing a nanoscale light source precisely near a nanoantenna.

A research group from ITMO University managed to combine a nanoantenna and a light source in a single nanoparticle. It can generate, enhance and route emission via excited resonant modes coupled with excitons. “We used hybrid perovskite as a material for such nanoantennas,” says Ekaterina Tiguntseva, first author of the publication. “Unique features of perovskite enabled us to make nanoantennas from this material. We basically synthesized perovskite films, and then transferred material particles from the film surface to another substrate by means of pulsed laser ablation technique. Compared to alternatives, our method is relatively simple and cost-effective.”

While studying the obtained perovskite nanoparticles, the scientists discovered that their emission can be enhanced if its spectra match with the Mie-resonant mode. “Currently, scientists are particularly interested in Mie-resonances related to dielectric and semiconductor nanoparticles,” explains George Zograf, Engineer at the Laboratory of Hybrid Nanophotonics and Optoelectronics at ITMO University. “Perovskites used in our work are semiconductors with luminescence efficiency much higher than that of many other materials. Our study shows that combination of excitons with Mie resonance in perovskite nanoparticles makes them efficient light sources at room temperature.”

In addition, the radiation spectrum of the nanoparticles can be changed by varying the anions in the material. “The structure of the material remains the same, we simply use another component in the synthesis of perovskite films. Therefore, it is not necessary to adjust the method each time. It remains the same, yet the emission color of our nanoparticles changes,” says Ekaterina.

The scientists will continue research on light-emitting perovskite nanoantennas using various components for their synthesis. In addition, they are developing new designs of perovskite nanostructures which may improve ultra compact optical devices.

Computer algorithms might be performing brain-like functions, such as facial recognition and language translation, but the computers themselves have yet to operate like brains.

“Computers have separate processing and memory storage units, whereas the brain uses neurons to perform both functions,” said Northwestern University’s Mark C. Hersam. “Neural networks can achieve complicated computation with significantly lower energy consumption compared to a digital computer.”

This is the memtransistor symbol overlaid on an artistic rendering of a hypothetical circuit layout in the shape of a brain. Credit: Hersam Research Group

This is the memtransistor symbol overlaid on an artistic rendering of a hypothetical circuit layout in the shape of a brain. Credit: Hersam Research Group

In recent years, researchers have searched for ways to make computers more neuromorphic, or brain-like, in order to perform increasingly complicated tasks with high efficiency. Now Hersam, a Walter P. Murphy Professor of Materials Science and Engineering in Northwestern’s McCormick School of Engineering, and his team are bringing the world closer to realizing this goal.

The research team has developed a novel device called a “memtransistor,” which operates much like a neuron by performing both memory and information processing. With combined characteristics of a memristor and transistor, the memtransistor also encompasses multiple terminals that operate more similarly to a neural network.

Supported by the National Institute of Standards and Technology and the National Science Foundation, the research was published online today, February 22, in Nature. Vinod K. Sangwan and Hong-Sub Lee, postdoctoral fellows advised by Hersam, served as the paper’s co-first authors.

The memtransistor builds upon work published in 2015, in which Hersam, Sangwan, and their collaborators used single-layer molybdenum disulfide (MoS2) to create a three-terminal, gate-tunable memristor for fast, reliable digital memory storage. Memristor, which is short for “memory resistors,” are resistors in a current that “remember” the voltage previously applied to them. Typical memristors are two-terminal electronic devices, which can only control one voltage channel. By transforming it into a three-terminal device, Hersam paved the way for memristors to be used in more complex electronic circuits and systems, such as neuromorphic computing.

To develop the memtransistor, Hersam’s team again used atomically thin MoS2 with well-defined grain boundaries, which influence the flow of current. Similar to the way fibers are arranged in wood, atoms are arranged into ordered domains – called “grains” – within a material. When a large voltage is applied, the grain boundaries facilitate atomic motion, causing a change in resistance.

“Because molybdenum disulfide is atomically thin, it is easily influenced by applied electric fields,” Hersam explained. “This property allows us to make a transistor. The memristor characteristics come from the fact that the defects in the material are relatively mobile, especially in the presence of grain boundaries.”

But unlike his previous memristor, which used individual, small flakes of MoS2, Hersam’s memtransistor makes use of a continuous film of polycrystalline MoS2 that comprises a large number of smaller flakes. This enabled the research team to scale up the device from one flake to many devices across an entire wafer.

“When length of the device is larger than the individual grain size, you are guaranteed to have grain boundaries in every device across the wafer,” Hersam said. “Thus, we see reproducible, gate-tunable memristive responses across large arrays of devices.”

After fabricating memtransistors uniformly across an entire wafer, Hersam’s team added additional electrical contacts. Typical transistors and Hersam’s previously developed memristor each have three terminals. In their new paper, however, the team realized a seven-terminal device, in which one terminal controls the current among the other six terminals.

“This is even more similar to neurons in the brain,” Hersam said, “because in the brain, we don’t usually have one neuron connected to only one other neuron. Instead, one neuron is connected to multiple other neurons to form a network. Our device structure allows multiple contacts, which is similar to the multiple synapses in neurons.”

Next, Hersam and his team are working to make the memtransistor faster and smaller. Hersam also plans to continue scaling up the device for manufacturing purposes.

“We believe that the memtransistor can be a foundational circuit element for new forms of neuromorphic computing,” he said. “However, making dozens of devices, as we have done in our paper, is different than making a billion, which is done with conventional transistor technology today. Thus far, we do not see any fundamental barriers that will prevent further scale up of our approach.”

A silicon-based quantum computing device could be closer than ever due to a new experimental device that demonstrates the potential to use light as a messenger to connect quantum bits of information — known as qubits — that are not immediately adjacent to each other. The feat is a step toward making quantum computing devices from silicon, the same material used in today’s smartphones and computers.

In a step forward for quantum computing in silicon -- the same material used in today's computers -- researchers successfully coupled a single electron's spin, represented by the dot on the left, to light, represented as a wave passing over the electron, which is trapped in a double-welled silicon chamber known as a quantum dot. The goal is to use light to carry quantum information to other locations on a futuristic quantum computing chip. Credit: Image courtesy of Emily Edwards, University of Maryland.

In a step forward for quantum computing in silicon — the same material used in today’s computers — researchers successfully coupled a single electron’s spin, represented by the dot on the left, to light, represented as a wave passing over the electron, which is trapped in a double-welled silicon chamber known as a quantum dot. The goal is to use light to carry quantum information to other locations on a futuristic quantum computing chip. Credit: Image courtesy of Emily Edwards, University of Maryland.

The research, published in the journal Nature, was led by researchers at Princeton University in collaboration with colleagues at the University of Konstanz in Germany and the Joint Quantum Institute, which is a partnership of the University of Maryland and the National Institute of Standards and Technology.

The team created qubits from single electrons trapped in silicon chambers known as double quantum dots. By applying a magnetic field, they showed they could transfer quantum information, encoded in the electron property known as spin, to a particle of light, or photon, opening the possibility of transmitting the quantum information.

“This is a breakout year for silicon spin qubits,” said Jason Petta, professor of physics at Princeton. “This work expands our efforts in a whole new direction, because it takes you out of living in a two-dimensional landscape, where you can only do nearest-neighbor coupling, and into a world of all-to-all connectivity,” he said. “That creates flexibility in how we make our devices.”

Quantum devices offer computational possibilities that are not possible with today’s computers, such as factoring large numbers and simulating chemical reactions. Unlike conventional computers, the devices operate according to the quantum mechanical laws that govern very small structures such as single atoms and sub-atomic particles. Major technology firms are already building quantum computers based on superconducting qubits and other approaches.

“This result provides a path to scaling up to more complex systems following the recipe of the semiconductor industry,” said Guido Burkard, professor of physics at the University of Konstanz, who provided guidance on theoretical aspects in collaboration with Monica Benito, a postdoctoral researcher. “That is the vision, and this is a very important step.”

Jacob Taylor, a member of the team and a fellow at the Joint Quantum Institute, likened the light to a wire that can connect spin qubits. “If you want to make a quantum computing device using these trapped electrons, how do you send information around on the chip? You need the quantum computing equivalent of a wire.”

Silicon spin qubits are more resilient than competing qubit technologies to outside disturbances such as heat and vibrations, which disrupt inherently fragile quantum states. The simple act of reading out the results of a quantum calculation can destroy the quantum state, a phenomenon known as “quantum demolition.”

The researchers theorize that the current approach may avoid this problem because it uses light to probe the state of the quantum system. Light is already used as a messenger to bring cable and internet signals into homes via fiber optic cables, and it is also being used to connect superconducting qubit systems, but this is one of the first applications in silicon spin qubits.

In these qubits, information is represented by the electron’s spin, which can point up or down. For example, a spin pointing up could represent a 0 and a spin pointing down could represent a 1. Conventional computers, in contrast, use the electron’s charge to encode information.

Connecting silicon-based qubits so that they can talk to each other without destroying their information has been a challenge for the field. Although the Princeton-led team successfully coupled two neighboring electron spins separated by only 100 nanometers (100 billionths of a meter), as published in Science in December 2017, coupling spin to light, which would enable long-distance spin-spin coupling, has remained a challenge until now.

In the current study, the team solved the problem of long-distance communication by coupling the qubit’s information — that is, whether the spin points up or down — to a particle of light, or photon, which is trapped above the qubit in the chamber. The photon’s wave-like nature allows it to oscillate above the qubit like an undulating cloud.

Graduate student Xiao Mi and colleagues figured out how to link the information about the spin’s direction to the photon, so that the light can pick up a message, such as “spin points up,” from the qubit. “The strong coupling of a single spin to a single photon is an extraordinarily difficult task akin to a perfectly choreographed dance,” Mi said. “The interaction between the participants — spin, charge and photon — needs to be precisely engineered and protected from environmental noise, which has not been possible until now.” The team at Princeton included postdoctoral fellow Stefan Putz and graduate student David Zajac.

The advance was made possible by tapping into light’s electromagnetic wave properties. Light consists of oscillating electric and magnetic fields, and the researchers succeeded in coupling the light’s electric field to the electron’s spin state.

The researchers did so by building on team’s finding published in December 2016 in the journal Science that demonstrated coupling between a single electron charge and a single particle of light.

To coax the qubit to transmit its spin state to the photon, the researchers place the electron spin in a large magnetic field gradient such that the electron spin has a different orientation depending on which side of the quantum dot it occupies. The magnetic field gradient, combined with the charge coupling demonstrated by the group in 2016, couples the qubit’s spin direction to the photon’s electric field.

Ideally, the photon will then deliver the message to another qubit located within the chamber. Another possibility is that the photon’s message could be carried through wires to a device that reads out the message. The researchers are working on these next steps in the process.

Several steps are still needed before making a silicon-based quantum computer, Petta said. Everyday computers process billions of bits, and although qubits are more computationally powerful, most experts agree that 50 or more qubits are needed to achieve quantum supremacy, where quantum computers would start to outshine their classical counterparts.

Daniel Loss, a professor of physics at the University of Basel in Switzerland who is familiar with the work but not directly involved, said: “The work by Professor Petta and collaborators is one of the most exciting breakthroughs in the field of spin qubits in recent years. I have been following Jason’s work for many years and I’m deeply impressed by the standards he has set for the field, and once again so with this latest experiment to appear in Nature. It is a big milestone in the quest of building a truly powerful quantum computer as it opens up a pathway for cramming hundreds of millions of qubits on a square-inch chip. These are very exciting developments for the field ¬– and beyond.”

Engineers at Rutgers University-New Brunswick and Oregon State University are developing a new method of processing nanomaterials that could lead to faster and cheaper manufacturing of flexible thin film devices – from touch screens to window coatings, according to a new study.

The “intense pulsed light sintering” method uses high-energy light over an area nearly 7,000 times larger than a laser to fuse nanomaterials in seconds. Nanomaterials are materials characterized by their tiny size, measured in nanometers. A nanometer is one millionth of a millimeter, or about 100,000 times smaller than the diameter of a human hair.

The existing method of pulsed light fusion uses temperatures of around 250 degrees Celsius (482 degrees Fahrenheit) to fuse silver nanospheres into structures that conduct electricity. But the new study, published in RSC Advances and led by Rutgers School of Engineering doctoral student Michael Dexter, showed that fusion at 150 degrees Celsius (302 degrees Fahrenheit) works well while retaining the conductivity of the fused silver nanomaterials.

The engineers’ achievement started with silver nanomaterials of different shapes: long, thin rods called nanowires in addition to nanospheres. The sharp reduction in temperature needed for fusion makes it possible to use low-cost, temperature-sensitive plastic substrates like polyethylene terephthalate (PET) and polycarbonate in flexible devices, without damaging them.

“Pulsed light sintering of nanomaterials enables really fast manufacturing of flexible devices for economies of scale,” said Rajiv Malhotra, the study’s senior author and assistant professor in the Department of Mechanical and Aerospace Engineering at Rutgers-New Brunswick. “Our innovation extends this capability by allowing cheaper temperature-sensitive substrates to be used.”

Fused silver nanomaterials are used to conduct electricity in devices such as radio-frequency identification (RFID) tags, display devices and solar cells. Flexible forms of these products rely on fusion of conductive nanomaterials on flexible substrates, or platforms, such as plastics and other polymers.

“The next step is to see whether other nanomaterial shapes, including flat flakes and triangles, will drive fusion temperatures even lower,” Malhotra said.

In another study, published in Scientific Reports, the Rutgers and Oregon State engineers demonstrated pulsed light sintering of copper sulfide nanoparticles, a semiconductor, to make films less than 100 nanometers thick.

“We were able to perform this fusion in two to seven seconds compared with the minutes to hours it normally takes now,” said Malhotra, the study’s senior author. “We also showed how to use the pulsed light fusion process to control the electrical and optical properties of the film.”

Their discovery could speed up the manufacturing of copper sulfide thin films used in window coatings that control solar infrared light, transistors and switches, according to the study. This work was funded by the National Science Foundation and The Walmart Manufacturing Innovation Foundation.

Imec has designed and fabricated a 16,384-electrode, 1,024-channel micro-electrode array (MEA) for high-throughput multi-modal cell interfacing. The chip offers intracellular and extracellular recording, voltage- and current-controlled stimulation, impedance monitoring and spectroscopy functionalities thereby packing the most cell-interfacing modalities on a single chip, and being the only one to enable multi-well assays. With this new chip, imec has created a platform that enables high quality data acquisition at increased throughput in cell-based cell studies. Imec’s micro-electrode array chip will be presented at ISSCC in San Francisco, Feb. 11-15.

These results will be presented at ISSCC2018 on Feb 14, 2018 in session 29: Advanced Biomedical Systems at 2.30 pm: 29.3 – A 16384-Electrode 1024-Channel Multimodal CMOS MEA for High-Throughput Intracellular Action Potential Measurements and Impedance Spectroscopy in Drug-Screening Applications, C. Mora Lopez et al. (imec).

These results will be presented at ISSCC2018 on Feb 14, 2018 in session 29: Advanced Biomedical Systems at 2.30 pm: 29.3 – A 16384-Electrode 1024-Channel Multimodal CMOS MEA for High-Throughput Intracellular Action Potential Measurements and Impedance Spectroscopy in Drug-Screening Applications, C. Mora Lopez et al. (imec).

MEAs have since long been used for in vitro cell-interaction experiments. However, most of today’s MEAs do not support high throughput measurements, making current cell-assays time-consuming. They are typically passive devices, without built-in circuitry, therefore requiring complex external equipment for data acquisition. Additionally, most MEAs are not able to accommodate the extra sensing modalities to fully characterize complex cell behavior and interactions.

Imec’s high-throughput multi-modal CMOS-MEA packs 16,384 active electrodes with signal processing, filtering and analog-to-digital conversion on-chip, resulting in a very complete and compact system with easy interfacing. To improve the signal quality, each electrode has a miniature pre-amplifier. The electrodes are grouped in 16 clusters, each of which can be addressed individually, making it possible to run 16 experiments independently and simultaneously. This CMOS-MEA also includes 1,024 low-noise readout channels that can be connected to any of the 16,384 electrodes. The custom reconfigurable on-chip circuits support 6 cell-interfacing modalities: both extra- and intracellular electrical activity recording, constant voltage and constant current stimulation for cell excitation or localized electroporation, fast impedance monitoring and, finally, impedance spectroscopy. While fast impedance monitoring can detect impedance changes over time and cell presence for optimal electrode selection, single-cell impedance spectroscopy gives detailed information of the electrode impedance, seal resistance and cell-membrane impedance which can be used for cell differentiation. Imec’s high input impedance, low noise and low power reconfigurable circuits make it possible to integrate 1,024 parallel readout channels and 64 reconfigurable stimulation units on a small chip area.

“Not only are we reporting the highest number of modalities so far on a single chip with a very high channel count, we are able to achieve this without any performance penalty. Moreover, by offering six modalities on such large scale, the imec CMOS-MEA will greatly improve the throughput and versatility of cell-based assays,” commented Nick Van Helleputte, manager biomedical circuits at imec. “With the introduction of CMOS chip technology into the MEA-technology, we have realized a breakthrough in cell interfacing.”