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Imec, a research and innovation hub in nanoelectronics and digital technology, announced today at the 2017 Symposia on VLSI Technology and Circuits the world’s first demonstration of a vertically stacked ferroelectric Al doped HfO2 device for NAND applications. Using a new material and a novel architecture, imec has created a non-volatile memory concept with attractive characteristics for power consumption, switching speed, scalability and retention. The achievement shows that ferro-electric memory is a highly promising technology at various points in the memory hierarchy, and as a new technology for storage class memory. Imec will further develop the concept in collaboration with the world’s leading producers of memory ICs.

Ferro-electric materials consist of crystals that exhibit spontaneous polarization; they can be in one of two states, which can be reversed with a suitable electric field. This non-volatile characteristic resembles ferromagnetism, after which they have been named. Discovered more than five decades ago, ferro-electric memory has always been considered ideal, due to its very low power needs, non-volatile character and high switching speed. However, issues with the complex materials, the breakdown of the interfacial layer and bad retention characteristics have presented significant challenges. The recent discovery of a ferro-electric phase in HfO2, a well-known and less complex material, has triggered a renewed interest in this memory concept.

“With HfO2, there is now a material with which we can process ferro-electric memories that are fully CMOS compatible. This allows us to make a ferro-electric FET (FeFET) in both planar and vertical varieties,” noted Jan Van Houdt, imec’s chief scientist for memory technology. “We are working to overcome some of the remaining issues, such as retention, precise doping techniques and interface properties, in order to stabilize the ferro-electric phase. We are now confident that our FeFET concept has all the required characteristics. It is, in fact, suitable for both stand-alone and embedded memories at various points in the memory hierarchy, going all the way from non-volatile DRAM to Flash-like memories. It has particularly interesting characteristics for future storage-class memory, which will help overcome the current bottleneck caused by the differences in speed between fast processors and slower mass memory.”

Imec recently presented the first, extremely positive results to its partners. The research center is now offering further development and industrialization of the vertical FeFET as a program to all its memory partners, which include the world’s major companies producing memory ICs.

“FeFETs can be used as a technology to build memory very similar to Flash-memory, but with additional advantages for further scaling, simplified processing, and power consumption,” added Van Houdt. “With our longstanding R&D and processing experience on advanced Flash, we are uniquely positioned to offer our partners a head start in this exciting opportunity. They can then decide how best to fit ferro-electric memories in their products and chips.”

Imec’s research into advanced memory is performed in cooperation with imec’s key partners in its core CMOS programs including GlobalFoundries, Intel, Micron, Qualcomm, Samsung, SK Hynix, Sony Semiconductor Solutions, Toshiba, Sandisk and TSMC.

imec ferroelectric

Currently, most parts of a smart phone are made of silicon and other compounds, which are expensive and break easily, but with almost 1.5 billion smart phones purchased worldwide last year, manufacturers are on the lookout for something more durable and less costly.

Dr. Elton Santos from Queen's University Belfast Credit: Queen's University Belfast

Dr. Elton Santos from Queen’s University Belfast
Credit: Queen’s University Belfast

Dr. Elton Santos from Queen’s University’s School of Mathematics and Physics, has been working with a team of top-notch scientists from Stanford University, University of California, California State University and the National Institute for Materials Science in Japan, to create new dynamic hybrid devices that are able to conduct electricity at unprecedented speeds and are light, durable and easy to manufacture in large scale semiconductor plants.

The team found that by combining semiconducting molecules C60 with layered materials, such as graphene and hBN, they could produce a unique material technology, which could revolutionise the concept of smart devices.

The winning combination works because hBN provides stability, electronic compatibility and isolation charge to graphene while C60 can transform sunlight into electricity. Any smart device made from this combination would benefit from the mix of unique features, which do not exist in materials naturally. This process, which is called van der Waals solids, allows compounds to be brought together and assembled in a pre-defined way.

Dr. Elton Santos explains: “Our findings show that this new ‘miracle material’ has similar physical properties to Silicon but it has improved chemical stability, lightness and flexibility, which could potentially be used in smart devices and would be much less likely to break.

“The material also could mean that devices use less energy than before because of the device architecture so could have improved battery life and less electric shocks.”

He added: “By bringing together scientists from across the globe with expertise in chemistry, physics and materials science we were able to work together and use simulations to predict how all of the materials could function when combined – and ultimately how these could work to help solve every day problems.

“This cutting-edge research is timely and a hot-topic involving key players in the field, which opens a clear international pathway to put Queen’s on the road-map of further outstanding investigations.”

The project initially started from the simulation side, where Dr. Santos predicted that such assembly of hBN, graphene and C60 could result in a solid with remarkable new physical and chemical properties. Then, he talked with his collaborators Professor Alex Zettl and Dr. Claudia Ojeda-Aristizabal at the University of California, and California St University in Long Beach (CA) about the findings. There was a strong synergy between theory and experiments throughout the project.

Dr. Santos said: “It is a sort of a ‘dream project’ for a theoretician since the accuracy achieved in the experiments remarkably matched what I predicted and this is not normally easy to find. The model made several assumptions that have proven to be completely right.”

The findings, which have been published in one of the most prestigious journals in the world ACS Nano, open the doors for further exploration of new materials. One issue that still needs to be solved with the team’s current research is that graphene and the new material architecture is lacking a ‘band gap’, which is the key to the on-off switching operations performed by electronic devices.

However, Dr. Santos’ team is already looking at a potential solution – transition metal dichalcogenides (TMDs). These are a hot topic at the moment as they are very chemically stable, have large sources for production and band gaps that rival Silicon.

He explains: “By using these findings, we have now produced a template but in future we hope to add an additional feature with TMDs. These are semiconductors, which by-pass the problem of the band gap, so we now have a real transistor on the horizon.”

Scientists have greatly expanded the range of functional temperatures for ferroelectrics, a key material used in a variety of everyday applications, by creating the first-ever polarization gradient in a thin film.

The achievement, reported May 10 in Nature Communications by researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), paves the way for developing devices capable of supporting wireless communications in extreme environments, from inside nuclear reactors to Earth’s polar regions.

Ferroelectric materials are prized for having a spontaneous polarization that is reversible by an applied electric field and for the ability to produce electric charges in response to physical pressure. They can function as capacitors, transducers, and oscillators, and they can be found in applications such as transit cards, ultrasound imaging, and push-button ignition systems.

Berkeley Lab scientists created a strain and chemical gradient in a 150-nanometer-thin film of barium strontium titanate, a widely used ferroelectric material. The researchers were able to directly measure the tiny atomic displacements in the material using cutting-edge advanced microscopy at Berkeley Lab, finding gradients in the polarization. The polarization varied from 0 to 35 microcoulombs per centimeter squared across the thickness of the thin-film material.

On the left is a low-resolution scanning transmission electron microscopy (STEM) image of a ferroelectric material that is continuously graded from barium strontium titanate (BSTO, top) to barium titanate (BTO, bottom). The material is grown on a gadolinium scandate (GSO) substrate buffered by a strontium ruthenate (SRO) bottom electrode. To the right are local nanobeam diffraction-based 2D maps of a-axis and c-axis lattice parameters that confirm large strain gradients in the ferroelectric material. The material is promising as electrically-tunable capacitors with extreme temperature stability. Credit: Anoop Damodaran/Berkeley Lab

On the left is a low-resolution scanning transmission electron microscopy (STEM) image of a ferroelectric material that is continuously graded from barium strontium titanate (BSTO, top) to barium titanate (BTO, bottom). The material is grown on a gadolinium scandate (GSO) substrate buffered by a strontium ruthenate (SRO) bottom electrode. To the right are local nanobeam diffraction-based 2D maps of a-axis and c-axis lattice parameters that confirm large strain gradients in the ferroelectric material. The material is promising as electrically-tunable capacitors with extreme temperature stability. Credit: Anoop Damodaran/Berkeley Lab

Tossing out textbook predictions

“Traditional physics and engineering textbooks wouldn’t have predicted this observation,” said study principal investigator Lane Martin, faculty scientist at Berkeley Lab’s Materials Sciences Division and UC Berkeley associate professor of materials and engineering. “Creating gradients in materials costs a lot of energy–Mother Nature doesn’t like them–and the material works to level out such imbalances in whatever way possible. In order for a large gradient like the one we have here to occur, we needed something else in the material to compensate for this unfavorable structure. In this case, the key is the material’s naturally occurring defects, such as charges and vacancies of atoms, that accommodate the imbalance and stabilize the gradient in polarization.”

Creating a polarization gradient had the beneficial effect of expanding the temperature range for optimal performance by the ferroelectric material. Barium titanate’s function is strongly temperature-dependent with relatively small effects near room temperature and a large, sharp peak in response at around 120 degrees Celsius. This makes it hard to achieve well-controlled, reliable function as the temperature varies beyond a rather narrow window. To adapt the material to work for applications at and around room temperature, engineers tune the chemistry of the material, but the range of temperatures where the materials are useful remains relatively narrow.

“The new polarization profile we have created gives rise to a nearly temperature-insensitive dielectric response, which is not common in ferroelectric materials,” said Martin. “By making a gradient in the polarization, the ferroelectric simultaneously operates like a range or continuum of materials, giving us high-performance results across a 500-degree Celsius window. In comparison, standard, off-the-shelf materials today would give the same responses across a much smaller 50-degree Celsius window.”

Beyond the obvious expansions to hotter and colder environments, the researchers noted that this wider temperature range could shrink the number of components needed in electronic devices and potentially reduce the power draw of wireless phones.

“The smartphone I’m holding in my hand right now has dielectric resonators, phase shifters, oscillators–more than 200 elements altogether–based on similar materials to what we studied in this paper,” said Martin. “About 45 of those elements are needed to filter the signals coming to and from your cell phone to make sure you have a clear signal. That’s a huge amount of real estate to dedicate to one function.”

Because changes in temperature alter the resonance of the ferroelectric materials, there are constant adjustments being made to match the materials to the wavelength of the signals sent from cell towers. Power is needed to tune the signal, and the more out of tune it is, the more power the phone needs to use to get a clear signal for the caller. A material with a polarization gradient capable operating over large temperatures regimes could reduce the power needed to tune the signal.

Faster detectors enable new imaging techniques

Understanding the polarization gradient entailed the use of epitaxial strain, a strategy in which a crystalline overlayer is grown on a substrate, but with a mismatch in the lattice structure. This strain engineering technique, commonly employed in semiconductor manufacturing, helps control the structure and enhance performance in materials.

Recent advances in electron microscopy have allowed researchers to obtain atomic-scale structural data of the strained barium strontium titanate, and to directly measure the strain and polarization gradient.

“We have established a way to use nanobeam scanning diffraction to record diffraction patterns from each point, and afterwards analyze the datasets for strain and polarization data,” said study co-author Andrew Minor, director of the National Center for Electron Microscopy at Berkeley Lab’s Molecular Foundry, a DOE Office of Science User Facility. “This type of mapping, pioneered at Berkeley Lab, is both new and very powerful.”

Another key factor was the speed of the detector, Minor added. For this paper, data was obtained at a rate of 400 frames per second, an order of magnitude faster than the 30-frame-per-second rate from just a few years ago. This technique is now available for users at the Foundry.

“We’re seeing a revolution in microscopy related to the use of direct electron detectors that is changing many fields of research,” said Minor, who also holds an appointment as a UC Berkeley professor of materials science and engineering. “We’re able to both see and measure things at a scale that was hard to imagine until recently.”

Researchers at the University of Melbourne are the first in the world to image how electrons move in two-dimensional graphene, a boost to the development of next-generation electronics.

Capable of imaging the behaviour of moving electrons in structures only one atom in thickness, the new technique overcomes significant limitations with existing methods for understanding electric currents in devices based on ultra-thin materials.

“Next-generation electronic devices based on ultra-thin materials, including quantum computers, will be especially vulnerable to contain minute cracks and defects that disrupt current flow,” said Professor Lloyd Hollenberg, Deputy Director of the Centre for Quantum Computation and Communication Technology (CQC2T) and Thomas Baker Chair at the University of Melbourne.

A team led by Hollenberg used a special quantum probe based on an atomic-sized ‘colour centre’ found only in diamonds to image the flow of electric currents in graphene. The technique could be used to understand electron behaviour in a variety of new technologies.

“The ability to see how electric currents are affected by these imperfections will allow researchers to improve the reliability and performance of existing and emerging technologies. We are very excited by this result, which enables us to reveal the microscopic behaviour of current in quantum computing devices, graphene and other 2D materials,” he said.

“Researchers at CQC2T have made great progress in atomic-scale fabrication of nanoelectronics in silicon for quantum computers. Like graphene sheets, these nanoelectronic structures are essentially one atom thick. The success of our new sensing technique means we have the potential to observe how electrons move in such structures and aid our future understanding of how quantum computers will operate.”

In addition to understanding nanoelectronics that control quantum computers, the technique could be used with 2D materials to develop next generation electronics, energy storage (batteries), flexible displays and bio-chemical sensors.

“Our technique is powerful yet relatively simple to implement, which means it could be adopted by researchers and engineers from a wide range of disciplines,” said lead author Dr Jean-Philippe Tetienne from CQC2T at the University of Melbourne.

“Using the magnetic field of moving electrons is an old idea in physics, but this is a novel implementation at the microscale with 21st Century applications.”

The work was a collaboration between diamond-based quantum sensing and graphene researchers. Their complementary expertise was crucial to overcoming technical issues with combining diamond and graphene.

“No one has been able to see what is happening with electric currents in graphene before,” said Nikolai Dontschuk, a graphene researcher at the University of Melbourne School of Physics.

“Building a device that combined graphene with the extremely sensitive nitrogen vacancy colour centre in diamond was challenging, but an important advantage of our approach is that it’s non-invasive and robust – we don’t disrupt the current by sensing it in this way,” he said.

Tetienne explained how the team was able to use diamond to successfully image the current.

“Our method is to shine a green laser on the diamond, and see red light arising from the colour centre’s response to an electron’s magnetic field,” he said.

“By analysing the intensity of the red light, we determine the magnetic field created by the electric current and are able to image it, and literally see the effect of material imperfections.”

Analog Devices, Inc. (ADI) today announced two high frequency, low noise MEMS accelerometers designed specifically for industrial condition monitoring applications. The ADXL1001 and ADXL1002 MEMS accelerometers deliver the high resolution vibration measurements necessary for early detection of bearing faults and other common causes of machine failure. Historically, inadequate noise performance of available high frequency MEMS accelerometers compared with legacy technology held back adoption, failing to take advantage of MEMS reliability, quality and repeatability. Today, the ADXL1001 and ADXL1002 noise performance over high frequencies is on par with available PZT technology, and make ADI MEMS accelerometers a compelling option for new condition monitoring products. The ADXL1001 and ADXL1002 are the latest examples of high performance precision sensing technology from Analog Devices, providing high quality and accurate data for Smart Factory Internet of Things applications, and enabling intelligent sensing from the edge of the network.

The ADXL1001 and ADXL1002 MEMS accelerometers deliver ultra-low noise density over an extended bandwidth with high-g range. The accelerometers are available in two models with full-scale ranges of ±100g (ADXL1001) and ±50g(ADXL1002). Typical noise density for the ADXL1002 is 25 μg/√Hz, with a sensitivity of 40mV/g, and 30 μg/√Hz for ADXL1001 with sensitivity 20mV/g. Both accelerometers operate on single voltage supply from 3.0V to 5.25V, and offer useful features such as complete, electrostatic self-test and over range indicator. The ADXL1001 and ADXL1002 are rated for operation over a -40°C to +125°C temperature range.

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ADXL1001 Analog ±100 g Now $29.61

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A technique that revolutionised scientists’ ability to manipulate and study materials at the nano-scale may have dramatic unintended consequences, new Oxford University research reveals.

Felix Hofmann and Edmund Tarleton, both authors of the paper, at the FIB instrument at the Department of Materials, University of Oxford, UK. Credit: Oxford University

Felix Hofmann and Edmund Tarleton, both authors of the paper, at the FIB instrument at the Department of Materials, University of Oxford, UK. Credit: Oxford University

Focused Ion Beam Milling (FIB) uses a tiny beam of highly energetic particles to cut and analyse materials smaller than one thousandth of a stand of human hair.

This remarkable capability transformed scientific fields ranging from materials science and engineering to biology and earth sciences. FIB is now an essential tool for a number of applications including; researching high performance alloys for aerospace engineering, nuclear and automotive applications and for prototyping in micro-electronics and micro-fluidics.

FIB was previously understood to cause structural damage within a thin surface layer (tens of atoms thick) of the material being cut. Until now it was assumed that the effects of FIB would not extend beyond this thin damaged layer. Ground-breaking new results from the University of Oxford demonstrate that this is not the case, and that FIB can in fact dramatically alter the material’s structural identity. This work was carried out in collaboration with colleagues from Argonne National Laboratory, USA, LaTrobe University, Australia, and the Culham Centre for Fusion Energy, UK.

In research newly published in the journal Scientific Reports, the team studied the damage caused by FIB using a technique called coherent synchrotron X-ray diffraction. This relies on ultra-bright high energy X-rays, available only at central facilities such as the Advanced Photon Source at Argonne National Lab, USA. These X-rays can probe the 3D structure of materials at the nano-scale. The results show that even very low FIB doses, previously thought negligible, have a dramatic effect.

Felix Hofmann, Associate Professor in Oxford’s Department of Engineering Science and lead author on the study, said, “Our research shows that FIB beams have much further-reaching consequences than first thought, and that the structural damage caused is considerable. It affects the entire sample, fundamentally changing the material. Given the role FIB has come to play in science and technology, there is an urgent need to develop new strategies to properly understand the effects of FIB damage and how it might be controlled.”

Prior to the development of FIB, sample preparation techniques were limited, only allowing sections to be prepared from the material bulk, but not from specific features. FIB transformed this field by making it possible to cut out tiny coupons from specific sites in a material. This progression enabled scientists to examine specific material feature using high-resolution electron microscopes. Furthermore it has made mechanical testing of tiny material specimens possible, a necessity for the study of dangerous or extremely precious materials.

Although keen for his peers to heed the serious consequence of FIB, Professor Hofmann said, “The scientific community has been aware of this issue for a while now, but no one (myself included) realised the scale of the problem. There is no way we could have known that FIB had such invasive side effects. The technique is integral to our work and has transformed our approach to prototyping and microscopy, completely changing the way we do science. It has become a central part of modern life.”

Moving forward, the team is keen to develop awareness of FIB damage. Furthermore, they will build on their current work to gain a better understanding of the damage formed and how it might be removed. Professor Hofmann said, “We’re learning how to get better. We have gone from using the technique blindly, to working out how we can actually see the distortions caused by FIB. Next we can consider approaches to mitigate FIB damage. Importantly the new X-ray techniques that we have developed will allow us to assess how effective these approaches are. From this information we can then start to formulate strategies for actively managing FIB damage.”

A team of Columbia Engineering researchers, led by Applied Physics Assistant Professor Nanfang Yu, has invented a method to control light propagating in confined pathways, or waveguides, with high efficiency by using nano-antennas. To demonstrate this technique, they built photonic integrated devices that not only had record-small footprints but were also able to maintain optimal performance over an unprecedented broad wavelength range.

Artistic illustration of a photonic integrated device that in one arm an incident fundamental waveguide mode (with one lobe in the waveguide cross-section) is converted into the second-order mode (with two lobes in the waveguide cross-section), and in the other arm the incident fundamental waveguide mode is converted into strong surface waves, which could be used for on-chip chemical and biological sensing. Credit: Nanfang Yu/Columbia Engineering

Artistic illustration of a photonic integrated device that in one arm an incident fundamental waveguide mode (with one lobe in the waveguide cross-section) is converted into the second-order mode (with two lobes in the waveguide cross-section), and in the other arm the incident fundamental waveguide mode is converted into strong surface waves, which could be used for on-chip chemical and biological sensing. Credit: Nanfang Yu/Columbia Engineering

Photonic integrated circuits (ICs) are based on light propagating in optical waveguides, and controlling such light propagation is a central issue in building these chips, which use light instead of electrons to transport data. Yu’s method could lead to faster, more powerful, and more efficient optical chips, which in turn could transform optical communications and optical signal processing. The study is published online in Nature Nanotechnology April 17.

“We have built integrated nanophotonic devices with the smallest footprint and largest operating bandwidth ever,” Yu says. “The degree to which we can now reduce the size of photonic integrated devices with the help of nano-antennas is similar to what happened in the 1950s when large vacuum tubes were replaced by much smaller semiconductor transistors. This work provides a revolutionary solution to a fundamental scientific problem: How to control light propagating in waveguides in the most efficient way?”

The optical power of light waves propagating along waveguides is confined within the core of the waveguide: researchers can only access the guided waves via the small evanescent “tails” that exist near the waveguide surface. These elusive guided waves are particularly hard to manipulate and so photonic integrated devices are often large in size, taking up space and thus limiting the device integration density of a chip. Shrinking photonic integrated devices represents a primary challenge researchers aim to overcome, mirroring the historical progression of electronics that follows Moore’s law, that the number of transistors in electronic ICs doubles approximately every two years.

Yu’s team found that the most efficient way to control light in waveguides is to “decorate” the waveguides with optical nano-antennas: these miniature antennas pull light from inside the waveguide core, modify the light’s properties, and release light back into the waveguides. The accumulative effect of a densely packed array of nano-antennas is so strong that they could achieve functions such as waveguide mode conversion within a propagation distance no more than twice the wavelength.

“This is a breakthrough considering that conventional approaches to realize waveguide mode conversion require devices with a length that is tens of hundreds of times the wavelength,” Yu says. “We’ve been able to reduce the size of the device by a factor of 10 to 100.”

Yu’s teams created waveguide mode converters that can convert a certain waveguide mode to another waveguide mode; these are key enablers of a technology called “mode-division multiplexing” (MDM). An optical waveguide can support a fundamental waveguide mode and a set of higher-order modes, the same way a guitar string can support one fundamental tone and its harmonics. MDM is a strategy to substantially augment an optical chip’s information processing power: one could use the same color of light but several different waveguide modes to transport several independent channels of information simultaneously, all through the same waveguide. “This effect is like, for example, the George Washington Bridge magically having the capability to handle a few times more traffic volume,” Yu explains. “Our waveguide mode converters could enable the creation of much more capacitive information pathways.”

He plans next to incorporate actively tunable optical materials into the photonic integrated devices to enable active control of light propagating in waveguides. Such active devices will be the basic building blocks of augmented reality (AR) glasses–goggles that first determine the eye aberrations of the wearer and then project aberration-corrected images into the eyes–that he and his Columbia Engineering colleagues, Professors Michal Lipson, Alex Gaeta, Demetri Basov, Jim Hone, and Harish Krishnaswamy are working on now. Yu is also exploring converting waves propagating in waveguides into strong surface waves, which could eventually be used for on-chip chemical and biological sensing.

A recent study, affiliated with UNIST has created a three-dimensional, tactile sensor that could detect wide pressure ranges from human body weight to a finger touch. This new sensor with transparent features is capable of generating an electrical signal based on the sensed touch actions, also, consumes far less electricity than conventional pressure sensors.

The breakthrough comes from a research, conducted by Professor Jang-Ung Park of Materials Science and Engineering and his research team at UNIST. In the study, the research team presented a novel method of fabricating a transistor-type active-matrix pressure sensor using foldable substrates and air-dielectric layers.

This image shows the transistor-type active-matrix 3-D pressure sensors with air-dielectric layers. Credit: UNIST

This image shows the transistor-type active-matrix 3-D pressure sensors with air-dielectric layers. Credit: UNIST

Today, most transistors are created with silicon channel and silicon oxide-based dielectrics. However, these transistors have been found to be either lacking transparency or inflexible, which may hinder their utility in fabricating highly-integrated pressure sensor arrays and transparent pressure sensors.

In this regard, Professor Park’s team decided to use highly-conductive and transparent graphene transistors with air-dielectric layers. The sensor can detect different types of touch-including swiping and tapping..

“Using air as the dielectric layer in graphene field-effect transistors (FETs) can significantly improve transistor performance due to the clean interface between graphene channel and air,” says Professor Park. “The thickness of the air-dielectric layers is determined by the applied pressure. With that technology, it would be possible to detect pressure changes far more effectively.”

A convantional touch panel, which may be included in a display device, reacts to the static electrical when pressure is applied to the monitor screen. With this method, the position on screen contacted by a finger, stylus, or other object can be easily detected using changes in pressure, but can not provide the intensity of pressure.

The research team placed graphene channel, metal nanowire electrodes, as well as an elastic body capable of trapping air on one side of the foldable substrate. Then they covered the other side of the substrate, like a lid and kept the air. In this transistor, the force pressing the elastic body is transferred to the air-dielectric layer and alters its thickness. Such changes in the thickness of the air-dielectric layer is converted into an electrical signal and transmitted via metal nanowires and the graphene channel, expressing both the position and the intensity of the pressure.

This is regarded as a promising technology as it enables the successful implementation of active-matrix pressure sensors. Moreover, when compared with the passive-matrix type, it consumes less power and has a faster response time.

It is possible to send and receive signals only by flowing electricity to the place where pressure is generated. The change in the thickness of the air dielectric layer is converted into an electrical signal to represent the position and intensity of the pressure. In addition, since all the substrates, channels, and electrode materials used in this process are all transparent, they can also be manufactured with invisible pressure sensors.

“This sensor is capable of simultaneously measuring anything from lower pressure (less than 10 kPa), such as gentle tapping to high pressure (above 2 MPa), such as human body weight,” says Sangyoon Ji (Combined M.S./Ph.D. student of Materials Science and Engineering), the first co-author of the study. “It can be also applied to 3D touchscreen panels or smart running shoes that can analyze life patterns of people by measuring their weight distribution.”

“This study not only solves the limitations of conventional pressure sensors, but also suggests the possibility to apply them to various fields by combining pressure sensor with other electronic devices such as display.” says Professor Park.

USB flash drives are already common accessories in offices and college campuses. But thanks to the rise in printable electronics, digital storage devices like these may soon be everywhere — including on our groceries, pill bottles and even clothing.

Duke University researchers have brought us closer to a future of low-cost, flexible electronics by creating a new “spray-on” digital memory device using only an aerosol jet printer and nanoparticle inks.

Duke University researchers have developed a new 'spray-on' digital memory (upper left) that could be used to build programmable electronic devices on flexible materials like paper, plastic or fabric. To demonstrate a simple application of their device, they used their memory to program different patterns of four LED lights in a simple circuit. Credit: Matthew Catenacci

Duke University researchers have developed a new ‘spray-on’ digital memory (upper left) that could be used to build programmable electronic devices on flexible materials like paper, plastic or fabric. To demonstrate a simple application of their device, they used their memory to program different patterns of four LED lights in a simple circuit. Credit: Matthew Catenacci

The device, which is analogous to a 4-bit flash drive, is the first fully-printed digital memory that would be suitable for practical use in simple electronics such as environmental sensors or RFID tags. And because it is jet-printed at relatively low temperatures, it could be used to build programmable electronic devices on bendable materials like paper, plastic or fabric.

“We have all of the parameters that would allow this to be used for a practical application, and we’ve even done our own little demonstration using LEDs,” said Duke graduate student Matthew Catenacci, who describes the device in a paper published online March 27 in the Journal of Electronic Materials.

At the core of the new device, which is about the size of a postage stamp, is a new copper-nanowire-based printable material that is capable of storing digital information.

“Memory is kind of an abstract thing, but essentially it is a series of ones and zeros which you can use to encode information,” said Benjamin Wiley, an associate professor of chemistry at Duke and an author on the paper.

Most flash drives encode information in series of silicon transistors, which can exist in a charged state, corresponding to a “one,” and an uncharged state, corresponding to a “zero,” Wiley said.

The new material, made of silica-coated copper nanowires encased in a polymer matrix, encodes information not in states of charge but instead in states of resistance. By applying a small voltage, it can be switched between a state of high resistance, which stops electric current, and a state of low resistance, which allows current to flow.

And, unlike silicon, the nanowires and the polymer can be dissolved in methanol, creating a liquid that can be sprayed through the nozzle of a printer.

“We have developed a way to make the entire device printable from solution, which is what you would want if you wanted to apply it to fabrics, RFID tags, curved and flexible substrates, or substrates that can’t sustain high heat,” Wiley said.

To create the device, Catenacci first used commercially-available gold nanoparticle ink to print a series of gold electrodes onto a glass slide. He then printed the copper-nanowire memory material over the gold electrodes, and finally printed a second series of electrodes, this time in copper.

To demonstrate a simple application, Catenacci connected the device to a circuit containing four LED lights. “Since we have four bits, we could program sixteen different states,” Catenacci said, where each “state” corresponds to a specific pattern of lights. In a real-world application, each of these states could be programmed to correspond to a number, letter, or other display symbol.

Though other research groups have fabricated similar printable memory devices in recent years, this is the first to combine key properties that are necessary for practical use. The write speed, or time it takes to switch back and forth between states, is around three microseconds, rivaling the speed of flash drives. Their tests indicate that written information may be retained for up to ten years, and the material can be re-written many times without degrading.

While these devices won’t be storing digital photos or music any time soon — their memory capacity is much too small for that — they may be useful in applications where low cost and flexibility are key, the researchers say.

“For example, right now RFID tags just encode a particular produce number, and they are typically used for recording inventory,” Wiley said. “But increasingly people also want to record what environment that product felt — such as, was this medicine always kept at the right temperature? One way these could be used would be to make a smarter RFID tags that could sense their environments and record the state over time.”

Brigham Young University researchers have developed new glass technology that could add a new level of flexibility to the microscopic world of medical devices.

A graduate student at BYU holds up a disc of microchips that have flexible glass membranes. Credit: Jaren Wilkey/BYU Photo

A graduate student at BYU holds up a disc of microchips that have flexible glass membranes. Credit: Jaren Wilkey/BYU Photo

Led by electrical engineering professor Aaron Hawkins, the researchers have found a way to make the normally brittle material of glass bend and flex. The research opens up the ability to create a new family of lab-on-a-chip devices based on flexing glass.

“If you keep the movements to the nanoscale, glass can still snap back into shape,” Hawkins said. “We’ve created glass membranes that can move up and down and bend. They are the first building blocks of a whole new plumbing system that could move very small volumes of liquid around.”

While current lab-on-a-chip membrane devices effectively function on the microscale, Hawkins’ research, recently published in Applied Physics Letters, will allow equally effective work at the nanoscale. Chemists and biologists could use the nanoscale devices to move, trap and analyze very small biological particles like proteins, viruses and DNA.

So why work with glass? According to lead study author and BYU Ph.D. student John Stout, glass has some great perks: it’s stiff and solid and not a material upon which things react, it’s easy to clean, and it isn’t toxic.

“Glass is clean for sensitive types of samples, like blood samples,” Stout said. “Working with this glass device will allow us to look at particles of any size and at any given range. It will also allow us to analyze the particles in the sample without modifying them.”

The researchers believe their device could also mean performing successful tests using much smaller quantities of a substance. Instead of needing several ounces to run a blood test, the glass membrane device created by Hawkins, Stout and coauthor Taylor Welker would only require a drop or two of blood.

Hawkins said the device should also allow for faster analysis of blood samples: “Instead of shipping a vial of blood to a lab and have it run through all those machines and steps, we are creating devices that can give you an answer on the spot.”

There is an increased demand for portable on-site rapid testing in the healthcare industry. Much of this is being realized through these microfluidic systems and devices, and the BYU device could take that testing to the next level of detail.

“This has the promise of being a rapid delivery of disease diagnosis, cholesterol level testing and virus testing,” Hawkins said. “In addition, it would help in the process of healthcare knowing the correct treatment method for the patient.”