Amazing Science

Micro-sized cameras have great potential to spot problems in the human body and enable sensing for super-small robots, but past approaches captured fuzzy, distorted images with limited fields of view.

Now, researchers at Princeton University and the University of Washington have overcome these obstacles with an ultracompact camera the size of a coarse grain of salt. The new system can produce crisp, full-color images on par with a conventional compound camera lens 500,000 times larger in volume, the researchers reported in a paper published Nov. 29 in Nature Communications.

Enabled by a joint design of the camera's hardware and computational processing, the system could enable minimally invasive endoscopy with medical robots to diagnose and treat diseases, and improve imaging for other robots with size and weight constraints. Arrays of thousands of such cameras could be used for full-scene sensing, turning surfaces into cameras.

While a traditional camera uses a series of curved glass or plastic lenses to bend light rays into focus, the new optical system relies on a technology called a metasurface, which can be produced much like a computer chip. Just half a millimeter wide, the metasurface is studded with 1.6 million cylindrical posts, each roughly the size of the human immunodeficiency virus (HIV).

Each post has a unique geometry, and functions like an optical antenna. Varying the design of each post is necessary to correctly shape the entire optical wavefront. With the help of machine learning-based algorithms, the posts' interactions with light combine to produce the highest-quality images and widest field of view for a full-color metasurface camera developed to date.

A key innovation in the camera's creation was the integrated design of the optical surface and the signal processing algorithms that produce the image. This boosted the camera's performance in natural light conditions, in contrast to previous metasurface cameras that required the pure laser light of a laboratory or other ideal conditions to produce high-quality images, said Felix Heide, the study's senior author and an assistant professor of computer science at Princeton.

Researchers reporting in ACS’ Nano Letters have transformed copper nanowires into metal foams that could be used in facemasks and air filtration systems. The foams filter efficiently, decontaminate easily for reuse and are recyclable.

The ongoing COVID-19 pandemic highlights the severe health risks posed by deep submicrometer-sized airborne viruses and particulates in the spread of infectious diseases. There is an urgent need for the development of efficient, durable, and reusable filters for this size range. Scientists now report the realization of efficient particulate filters using nanowire-based low-density metal foams which combine extremely large surface areas with excellent mechanical properties. The metal foams exhibit outstanding filtration efficiencies (>96.6%) in the PM0.3 regime, with the potential for further improvement. Their mechanical stability, light weight, chemical and radiation resistance, ease of cleaning and reuse, and recyclability further make such metal foams promising filters for combating COVID-19 and other types of airborne particulates.

While digital technology is extremely good at solving certain problems, it often struggles with tasks that the human brain excels at. In a new study, scientists have leveraged brain-inspired connectivity between artificial neurons to solve a real-world problem of identifying mutations of a new viral species.

In the September issue of the journal Nature, scientists from Texas A&M University, Hewlett Packard Labs and Stanford University have described a new nanodevice that acts almost identically to a brain cell. Furthermore, they have shown that these synthetic brain cells can be joined together to form intricate networks that can then solve problems in a brain-like manner.

"This is the first study where we have been able to emulate a neuron with just a single nanoscale device, which would otherwise need hundreds of transistors," said Dr. R. Stanley Williams, senior author on the study and professor in the Department of Electrical and Computer Engineering. "We have also been able to successfully use networks of our artificial neurons to solve toy versions of a real-world problem that is computationally intense even for the most sophisticated digital technologies."

In particular, the researchers have demonstrated proof of concept that their brain-inspired system can identify possible mutations in a virus, which is highly relevant for ensuring the efficacy of vaccines and medications for strains exhibiting genetic diversity.

Over the past decades, digital technologies have become smaller and faster largely because of the advancements in transistor technology. However, these critical circuit components are fast approaching their limit of how small they can be built, initiating a global effort to find a new type of technology that can supplement, if not replace, transistors.

In addition to this "scaling-down" problem, transistor-based digital technologies have other well-known challenges. For example, they struggle at finding optimal solutions when presented with large sets of data. "Let's take a familiar example of finding the shortest route from your office to your home. If you have to make a single stop, it's a fairly easy problem to solve. But if for some reason you need to make 15 stops in between, you have 43 billion routes to choose from," said Dr. Suhas Kumar, lead author on the study and researcher at Hewlett Packard Labs. "This is now an optimization problem, and current computers are rather inept at solving it."

Kumar added that another arduous task for digital machines is pattern recognition, such as identifying a face as the same regardless of viewpoint or recognizing a familiar voice buried within a din of sounds. But tasks that can send digital machines into a computational tizzy are ones at which the brain excels. In fact, brains are not just quick at recognition and optimization problems, but they also consume far less energy than digital systems. Hence, by mimicking how the brain solves these types of tasks, Williams said brain-inspired or neuromorphic systems could potentially overcome some of the computational hurdles faced by current digital technologies.

To build the fundamental building block of the brain or a neuron, the researchers assembled a synthetic nanoscale device consisting of layers of different inorganic materials, each with a unique function. However, they said the real magic happens in the thin layer made of the compound niobium dioxide.

When a small voltage is applied to this region, its temperature begins to increase. But when the temperature reaches a critical value, niobium dioxide undergoes a quick change in personality, turning from an insulator to a conductor. But as it begins to conduct electric currents, its temperature drops and niobium dioxide switches back to being an insulator.

These back-and-forth transitions enable the synthetic devices to generate a pulse of electrical current that closely resembles the profile of electrical spikes, or action potentials, produced by biological neurons. Further, by changing the voltage across their synthetic neurons, the researchers reproduced a rich range of neuronal behaviors observed in the brain, such as sustained, burst and chaotic firing of electrical spikes. "Capturing the dynamical behavior of neurons is a key goal for brain-inspired computers," said Kumar. "Altogether, we were able to recreate around 15 types of neuronal firing profiles, all using a single electrical component and at much lower energies compared to transistor-based circuits."

Researchers at Columbia University and University of California, San Diego, have introduced a novel "multi-messenger" approach to quantum physics that signifies a technological leap in how scientists can explore quantum materials.

The findings appear in a recent article published in Nature Materials, led by A. S. McLeod, postdoctoral researcher, Columbia Nano Initiative, with co-authors Dmitri Basov and A. J. Millis at Columbia and R.A. Averitt at UC San Diego. "We have brought a technique from the inter-galactic scale down to the realm of the ultra-small," said Basov, Higgins Professor of Physics and Director of the Energy Frontier Research Center at Columbia. Equipped with multi-modal nanoscience tools we can now routinely go places no one thought would be possible as recently as five years ago."

The work was inspired by "multi-messenger" astrophysics, which emerged during the last decade as a revolutionary technique for the study of distant phenomena like black hole mergers. Simultaneous measurements from instruments, including infrared, optical, X-ray and gravitational-wave telescopes can, taken together, deliver a physical picture greater than the sum of their individual parts.

The search is now on for new materials that can supplement the current reliance on electronic semiconductors. Control over material properties using light can offer improved functionality, speed, flexibility and energy efficiency for next-generation computing platforms.

Experimental papers on quantum materials have typically reported results obtained by using only one type of spectroscopy. The researchers have shown the power of using a combination of measurement techniques to simultaneously examine electrical and optical properties.

The researchers performed their experiment by focusing laser light onto the sharp tip of a needle probe coated with magnetic material. When thin films of metal oxide are subject to a unique strain, ultra-fast light pulses can trigger the material to switch into an unexplored phase of nanometer-scale domains, and the change is reversible.

By scanning the probe over the surface of their thin film sample, the researchers were able to trigger the change locally and simultaneously manipulate and record the electrical, magnetic and optical properties of these light-triggered domains with nanometer-scale precision.

The study reveals how unanticipated properties can emerge in long-studied quantum materials at ultra-small scales when scientists tune them by strain. "It is relatively common to study these nano-phase materials with scanning probes. But this is the first time an optical nano-probe has been combined with simultaneous magnetic nano-imaging, and all at the very low temperatures where quantum materials show their merits," McLeod said. "Now, investigation of quantum materials by multi-modal nanoscience offers a means to close the loop on programs to engineer them."

In another indication of the frightening pace at which nano and biotechnology is now moving, scientists have developed a technique that gives mice a near infra-red spectrum of vision, allowing them to see in the dark. Night goggles use infrared light and researchers have found a similar effect can be achieved by injecting specially designed ‘nanoparticles’ directly into the eyes of mice. And humans could follow.

After injection, the nanoparticles that gave the mice ‘super sight’ sit at the back of their retinas. From that position, they convert near infrared light that is normally invisible to the eye into a form of visible light. Effectively meaning the mice could see in the dark in a way similar to how they would if fitted with a set of high-tech night goggles like those used in the military. Over several weeks, the body gradually removes the nanoparticles without any visible ill effects on the mice.

Further research is still required before the technique can be judged to genuinely have no side effects but the initial findings are highly promising. If that does prove to be the case, there is no obvious reason why the biotech technique couldn’t then be applied to humans. That could potentially mean professionals that today need to use often bulky night vision equipment, such as special forces, would instead be given a ‘night vision jab’.

The researchers behind the study, from the University of Massachusetts, this week presented their findings at the autumn meeting of the American Chemical Society. The mice were first trained to swim through a water maze, following triangular signs and ignoring circular ‘red herrings’. The signs were illuminated by normal, everyday visible light. After they had been injected with the nanoparticles, the signs were instead lit with infrared light that would not ordinarily have been visible to the mice. But they were able to see and follow them.

As a chameleon shifts its color from turquoise to pink to orange to green, nature's design principles are at play. Complex nano-mechanics are quietly and effortlessly working to camouflage the lizard's skin to match its environment.

Inspired by nature, a Northwestern University team has developed a novel nanolaser that changes colors using the same mechanism as chameleons. The work could open the door for advances in flexible optical displays in smartphones and televisions, wearable photonic devices and ultra-sensitive sensors that measure strain.

"Chameleons can easily change their colors by controlling the spacing among the nanocrystals on their skin, which determines the color we observe," said Teri W. Odom, Charles E. and Emma H. Morrison Professor of Chemistry in Northwestern's Weinberg College of Arts and Sciences. "This coloring based on surface structure is chemically stable and robust."

The research is published in the journal Nano Letters. The same way a chameleon controls the spacing of nanocrystals on its skin, the Northwestern team's laser exploits periodic arrays of metal nanoparticles on a stretchable, polymer matrix. As the matrix either stretches to pull the nanoparticles farther apart or contracts to push them closer together, the wavelength emitted from the laser changes wavelength, which also changes its color. "Hence, by stretching and releasing the elastomer substrate, we could select the emission color at will," Odom said.

The resulting laser is robust, tunable, reversible and has a high sensitivity to strain. These properties are critical for applications in responsive optical displays, on-chip photonic circuits and multiplexed optical communication.

Magnetic materials are the backbone of modern digital information technologies, such as hard-disk storage. A University of Washington-led team has now taken this one step further by encoding information using magnets that are just a few layers of atoms in thickness. This breakthrough may revolutionize both cloud computing technologies and consumer electronics by enabling data storage at a greater density and improved energy efficiency.

In a study published online May 3 in the journal Science, the researchers report that they used stacks of ultrathin materials to exert unprecedented control over the flow of electrons based on the direction of their spins — where the electron “spins” are analogous to tiny, subatomic magnets. The materials that they used include sheets of chromium tri-iodide (CrI3), a material described in 2017 as the first ever 2-D magnetic insulator. Four sheets — each only atoms thick — created the thinnest system yet that can block electrons based on their spins while exerting more than 10 times stronger control than other methods.

“Our work reveals the possibility to push information storage based on magnetic technologies to the atomically thin limit,” said co-lead author Tiancheng Song, a UW doctoral student in physics.

A group of Korean researchers has used a new means of doing that detecting sooner rather than later — the new detector is called a bioelectronic nose. Led by Dr. Kyung Mi Lee, from Myongji University in the Republic of Korea, the scientists compared the ability to detect indicators of spoilage or contamination of the 'nose' with the ability of trained human testers and with classical detection techniques such as gas chromatography-mass spectroscopy (GC-MS). The comparisons are shown in the figure below.

The bioelectronic nose consists of engineered human odor receptor proteins linked to carbon nanotubes (CNT—the transducers) (full description is given here). This particular nose was designed to detect the compound trimethylamine (TMA) specifically. TMA is produced by bacteria that can contaminate oysters. For comparative purposes, the GC-MS system was used to detect another bacterial product called dimethyl sulfide (DMS), which, when present in sufficient amounts, imparts a fishy, ammonia-like odor that can be detected by the human nose*. And the trained sensory panelists evaluated the oysters on a range of characteristics such as appearance, odor, taste, texture and acceptability (dislike to swallow).

Oysters were obtained from a commercial vendor and stored at 4oC (39oF — refrigerator temperature) or at 36oC (97oF) in closed glass vials. Samples of the air space in the vials was used for the detection of TMA and DMS at serial time points up to 12 days. It wasn't until the 6th day of storage that the panelists indicated a strong 'dislike to swallow' for the oysters, and their tasting of 'fish and pungent' flavor, an indication of the presence of DMS increased daily, as did their detection of a fish and pungent aroma.

When the oysters were stored at 4oC, the GC-MS system detected DMS by day 4; when storage was at 36oC, DMS was detected at day 1. However, the electronic nose was able to detect TMA by day 2 of 4o storage, and on day 1 of 36o storage. In other assays the investigators determined that several bacterial genera were present in the oysters used in these comparisons — including Pseudomonas, Shwanella, and Vibrio. Some of the bacteria found are capable of producing harmful toxins.

Researchers have shown how to write any magnetic pattern desired onto nanowires, which could help computers mimic how the brain processes information. Much current computer hardware, such as hard drives, use magnetic memory devices. These rely on magnetic states -- the direction microscopic magnets are pointing -- to encode and read information.

Exotic magnetic states -- such as a point where three south poles meet -- represent complex systems. These may act in a similar way to many complex systems found in nature, such as the way our brains process information. Computing systems that are designed to process information in similar ways to our brains are known as 'neural networks'. There are already powerful software-based neural networks -- for example one recently beat the human champion at the game 'Go' -- but their efficiency is limited as they run on conventional computer hardware.

Now, researchers from Imperial College London have devised a method for writing magnetic information in any pattern desired, using a very small magnetic probe called a magnetic force microscope. With this new writing method, arrays of magnetic nanowires may be able to function as hardware neural networks -- potentially more powerful and efficient than software-based approaches. The team, from the Departments of Physics and Materials at Imperial, demonstrated their system by writing patterns that have never been seen before. They published their results today in Nature Nanotechnology.

Dr Jack Gartside, first author from the Department of Physics, said: "With this new writing method, we open up research into 'training' these magnetic nanowires to solve useful problems. If successful, this will bring hardware neural networks a step closer to reality." As well as applications in computing, the method could be used to study fundamental aspects of complex systems, by creating magnetic states that are far from optimal (such as three south poles together) and seeing how the system responds.

MIT researchers have designed nanosensors that can profile tumors and may yield insight into how they will respond to certain therapies.

Once adapted for humans, this type of sensor could be used to determine how aggressive a tumor is and help doctors choose the best treatment, says Sangeeta Bhatia, the John and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science and a member of MIT's Koch Institute for Integrative Cancer Research.

"This approach is exciting because people are developing therapies that are protease-activated," Bhatia says. "Ideally you'd like to be able to stratify patients based on their protease activity and identify which ones would be good candidates for these therapies."

Once injected into the tumor site, the nanosensors are activated by a magnetic field that is harmless to healthy tissue. After interacting with and being modified by the target tumor proteins, the sensors are secreted in the urine, where they can be easily detected in less than an hour.

Bhatia and Polina Anikeeva, the Class of 1942 Associate Professor of Materials Science and Engineering, are the senior authors of the paper, which appears in the journal Nano Letters. The paper's lead authors are Koch Institute postdoc Simone Schurle and graduate student Jaideep Dudani.

Tumors, especially aggressive ones, often have elevated protease levels. These enzymes help tumors spread by cleaving proteins that compose the extracellular matrix, which normally surrounds cells and holds them in place.

In 2014, Bhatia and colleagues reported using nanoparticles that interact with a type of protease known as matrix metalloproteinases (MMPs) to diagnose cancer. In that study, the researchers delivered nanoparticles carrying peptides, or short protein fragments, designed to be cleaved by the MMPs. If MMPs were present, hundreds of cleaved peptides would be excreted in the urine, where they could be detected with a simple paper test similar to a pregnancy test.

In the new study, the researchers wanted to adapt the sensors so that they could report on the traits of tumors in a known location. To do that, they needed to ensure that the sensors were only producing a signal from the target organ, unaffected by background signals that might be produced in the bloodstream. They first designed sensors that could be activated with light once they reached their target. That required the use of ultraviolet light, however, which doesn't penetrate very far into tissue.

MIT engineers designed a tiny “brain-on-a-chip” from tens of thousands of artificial brain synapses known as memristors — silicon-based components that mimic the information-transmitting synapses in the human brain.

The researchers borrowed from principles of metallurgy to fabricate each memristor from alloys of silver and copper, along with silicon. When they ran the chip through several visual tasks, the chip was able to “remember” stored images and reproduce them many times over, in versions that were crisper and cleaner compared with existing memristor designs made with unalloyed elements.

Their results, published today in the journal Nature Nanotechnology, demonstrate a promising new memristor design for neuromorphic devices — electronics that are based on a new type of circuit that processes information in a way that mimics the brain’s neural architecture. Such brain-inspired circuits could be built into small, portable devices, and would carry out complex computational tasks that only today’s supercomputers can handle.

“So far, artificial synapse networks exist as software. We’re trying to build real neural network hardware for portable artificial intelligence systems,” says Jeehwan Kim, associate professor of mechanical engineering at MIT. “Imagine connecting a neuromorphic device to a camera on your car, and having it recognize lights and objects and make a decision immediately, without having to connect to the internet. We hope to use energy-efficient memristors to do those tasks on-site, in real-time.”

Researchers at the Dutch Advanced Research Center for Nanolithography (ARCNL) and Vrije Universiteit Amsterdam (VU), developed an advanced microscope capable of super-resolution microscopy through an ultra-thin fiber. 

Up until now, it was generally the case that the higher the resolution of a microscope, the larger the device needed to be, making it virtually impossible to look inside the human body in real-time. Although some methods that enable researchers to look inside living animals already exist, their resolution is very limited, and it takes a long time to generate an acceptable image. 

With the use of smart signal processing, the researchers are able to beat the theoretical limits of resolution and speed. With this newly developed compact setup, scientists are finally able to, for example, look inside the brain in real-time and high resolution, using an ultra-thin fiber. Because the method does not require any unique fluorescent labeling, it is promising for both medical uses and characterization of 3D structures in nano-lithography! 

Mechanoluminescence (ML) is a type of luminescence induced by any mechanical action on a solid, leading to a range of applications in materials research, photonics and optics. For instance, the mechanical action can release energy previously stored in the crystal lattice of phosphor via trapped charge carriers. However, the method has limits when recording ML emissions during a pressure-induced event. In a new study, Robin R. Petit and a research team at the LumiLab, Department of Solid State Sciences at the Ghent University—Belgium devised a new technique to add a memory function to pressure-sensitive phosphors. Using the method, the scientists obtained an optical readout of the location and intensity of a pressure event three days (72 hours) after the event.

The team noted the outcome using Europium-doped barium silicon oxynitride (BaSiO2N2:Eu2+) phosphor, which contained a broad trap depth distribution or depth of defect distribution—essential for the unique memory function.

The excited electrons of phosphor filled the 'traps' (or defects) in the crystal lattice, which could be emptied by applying weight to emit light. The research team merged optically stimulated luminescence (OSL), thermoluminescence (TL) and ML measurements to carefully analyze the influence of light, heat and pressure on trap depth distribution. Based on the memory effect, the materials remembered the location at which pressure had occurred, helping researchers to develop new pressure sensing applications and study charge carrier transitions within energy storage phosphors. The work is now published on Light: Science & Applications.

When specific materials are subjected to mechanical action, light emission can be observed as mechanoluminescence (ML). The process can be induced through different types of mechanical stress including friction, fracture, bending, impact of a weight and even ultrasound, crystallization and wind.

The phenomenon can be used to identify stress distribution, microcrack propagation and structural damages in solids, while allowing a variety of applications in displays, to visualize ultrasound and even map personalized handwriting. However, the technique is limited by the range of emission colors, restriction of real-time measurements and restricted signal visibility.

CSAIL wireless system suggests future where doctors could implant sensors to track tumors or even dispense drugs.

Investigating inside the human body often requires cutting open a patient or swallowing long tubes with built-in cameras. But what if physicians could get a better glimpse in a less expensive, invasive, and time-consuming manner?

A team from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) led by Professor Dina Katabi is working on doing exactly that with an “in-body GPS" system dubbed ReMix. The new method can pinpoint the location of ingestible implants inside the body using low-power wireless signals. These implants could be used as tiny tracking devices on shifting tumors to help monitor their slight movements.

In animal tests, the team demonstrated that they can track the implants with centimeter-level accuracy. The team says that, one day, similar implants could be used to deliver drugs to specific regions in the body.

ReMix was developed in collaboration with researchers from Massachusetts General Hospital (MGH). The team describes the system in a paper that's being presented at this week's Association for Computing Machinery's Special Interest Group on Data Communications (SIGCOMM) conference in Budapest, Hungary.

A new way of using a laser cavity to study the emergence of topological defects has been unveiled by researchers in Israel.

Topological defects emerge when a system makes a rapid transition from a disordered to an ordered phase – a process called quenching because it often involves rapid cooling. In the case of magnetic order, quenched magnetic moments form small domains in which the moments point in the same direction. Moments in neighboring domains can point in different directions and the interfaces between domains are called topological defects. These defects can occur in a wide range of systems, from atomic gases to the rapidly cooling early universe. Understanding how to eliminate topological defects could even be exploited to solve hard computational problems.

Multiple lasers

How topological defects emerge can be very tricky to study in the laboratory because controlling the rapidly changing temperature throughout a sample can be very difficult. In this latest study, Vishwa Pal, Nir Davidson and colleagues at the Weizmann Institute in Israel have used a set of up to 30 coupled laser beams to create a system with topological defects that can be studied more easily.

Their system comprises a laser cavity containing a mask with a number of holes arranged in a circular pattern. Each hole produces its own laser beam, which overlaps a bit with its two neighbours – leading to an interaction between beams.

The laser cavity is pumped by an external light pulse and the interaction causes the laser beams to undergo rapid phase oscillations before settling into a steady state that is then measured by the team. The laser cavity contains about 1000 modes and this provides the system with a large number of initial phase relationships between the laser beams. In most cases the beams synchronize, but occasionally the system gets locked into a state in which there are phase differences between the beams. These states can be described as topological defects, and the team found that their number increased as the number of holes is increased from 10 to 30 – and also when the intensity of the pump pulse is increased.

Motion is a common phenomenon in biological processes. Major advances have been made in designing various self-propelled micromachines that harvest different types of energies into mechanical movement to achieve biomedicine and biological applications. Inspired by fascinating self-organization motion of natural creatures, the swarming or assembly of synthetic micro/nanomachines (often referred to micro/nanoswimmers, micro/nanorobots, micro/nanomachines, or micro/nanomotors), are able to mimic these amazing natural systems to help humanity accomplishing complex biological tasks. This review described the fuel induced methods (enzyme, hydrogen peroxide, hydrazine, et al.) and fuel-free induced approaches (electric, ultrasound, light, and magnetic) that led to control the assembly and swarming of synthetic micro/nanomachines. Such behavior is of fundamental importance in improving our understanding of self-assembly processes that are occurring on molecular to macroscopic length scales.

"The NIST synapse has lower energy needs than the human synapse, and we don't know of any other artificial synapse that uses less energy," NIST physicist Mike Schneider said.

The new synapse would be used in neuromorphic computers made of superconducting components, which can transmit electricity without resistance, and therefore, would be more efficient than other designs based on semiconductors or software. Data would be transmitted, processed and stored in units of magnetic flux. Superconducting devices mimicking brain cells and transmission lines have been developed, but until now, efficient synapses—a crucial piece—have been missing.

The use of quantum dots (QDs) in practical applications relies on the ability to precisely pattern QDs on substrates with desired optical properties. Typical direct-write printing techniques such as inkjet and gravure printing are limited in resolution (micron-scale), structural complexity, and require significant post-processing time.In new work, researchers at the University of Texas at Austin use laser-induced bubble printing to pattern CdSe/CdS QDs on plasmonic substrates with submicron resolution (<700nm line width), high throughput (∼10E4 µm/s) and strong QD-substrate adhesion.Not only is the bubble-mediated immobilization at the submicron scale stable, but the submicron-sized bubble's stability can be maintained over a large area.

This technique is also compatible with flexible substrates and can be further integrated with smartphone to realize haptic integration. Finally, the emission characteristics of the QDs in terms of the emission wavelength and lifetime can be modified in real-time to achieve site-sensitive emission.The team, led by Yuebing Zheng, Assistant Professor of Mechanical Engineering and Materials Science & Engineering has been published in ACS Applied Materials & Interfaces ("High-Resolution Bubble Printing of Quantum Dots").

Less than a micrometer thin, bendable and giving all the colors that a regular LED display does, it still needs ten times less energy than a Kindle tablet. Researchers at Chalmers University of Technology have developed the basis for a new electronic "paper." Their results were recently published in the journal Advanced Materials.

When Chalmers researcher Andreas Dahlin and his PhD student Kunli Xiong were working on placing conductive polymers on nanostructures, they discovered that the combination would be perfectly suited to creating electronic displays as thin as paper. A year later the results were ready for publication. A material that is less than a micrometer thin, flexible and giving all the colors that a standard LED display does.

"The 'paper' is similar to the Kindle tablet," says Andreas Dahlin. "It isn't lit up like a standard display, but rather reflects the external light which illuminates it. Therefore it works very well where there is bright light, such as out in the sun, in contrast to standard LED displays that work best in darkness. At the same time it needs only a tenth of the energy that a Kindle tablet uses, which itself uses much less energy than a tablet LED display."

It all depends on the polymers' ability to control how light is absorbed and reflected. The polymers that cover the whole surface lead the electric signals throughout the full display and create images in high resolution. The material is not yet ready for application, but the basis is there. The team has tested and built a few pixels. These use the same red, green and blue (RGB) colors that together can create all the colors in standard LED displays. The results so far have been positive, what remains now is to build pixels that cover an area as large as a display. "We are working at a fundamental level but even so, the step to manufacturing a product out of it shouldn't be too far away. What we need now are engineers."

Researchers from the National Institute of Standards and Technology (NIST) and collaborators have proposed a design for the first DNA sequencer based on an electronic nanosensor that can detect tiny motions as small as a single atom.

The proposed device—a type of capacitor, which stores electric charge—is a tiny ribbon of molybdenum disulfide suspended over a metal electrode and immersed in water. The ribbon is 15.5 nm long and 4.5 nm wide. Single-stranded DNA, containing a chain of bases (bits of genetic code), is threaded through a hole 2.5 nm wide in the thin ribbon. The ribbon flexes only when a DNA base pairs up with and then separates from a complementary base affixed to the hole. The membrane motion is detected as an electrical signal.

As described in a new paper, the NIST team made numerical simulations and theoretical estimates to show the membrane would be 79 to 86 percent accurate in identifying DNA bases in a single measurement at speeds up to about 70 million bases per second. Integrated circuits would detect and measure electrical signals and identify bases. The results suggest such a device could be a fast, accurate and cost-effective DNA sequencer, according to the paper.

Conventional sequencing, developed in the 1970s, involves separating, copying, labeling and reassembling pieces of DNA to read the genetic information. Newer methods include automated sequencing of many DNA fragments at once—still costly—and novel "nanopore sequencing" concepts. For example, the same NIST group recently demonstrated the idea of sequencing DNA by passing it through a graphene nanopore, and measuring how graphene's electronic properties respond to strain.

The latest NIST proposal relies on a thin film of molybdenum disulfide—a stable, layered material that conducts electricity and is often used as a lubricant. Among other advantages, this material does not stick to DNA, which can be a problem with graphene. The NIST team suggests the method might even work without a nanopore—a simpler design—by passing DNA across the edge of the membrane.

"This approach potentially solves the issue with DNA sticking to graphene if inserted improperly, because this approach does not use graphene, period," NIST theorist and lead author Alex Smolyanitsky said. "Another major difference is that instead of relying on the properties of graphene or any particular material used, we read motions electrically in an easier way by forming a capacitor. This makes any electrically conductive membrane suitable for the application."