Injectable Chips to Monitor Body Processes

Columbia Engineers develop the smallest single-chip system that is a complete functioning electronic circuit; implantable chips visible only in a microscope point the way to developing chips that can be injected into the body with a hypodermic needle to monitor medical conditions.

Widely used to monitor and map biological signals, to support and enhance physiological functions, and to treat diseases, implantable medical devices are transforming healthcare and improving the quality of life for millions of people. Researchers are increasingly interested in designing wireless, miniaturized implantable medical devices for in vivo and in situ physiological monitoring. These devices could be used to monitor physiological conditions, such as temperature, blood pressure, glucose, and respiration for both diagnostic and therapeutic procedures.

To date, conventional implanted electronics have been highly volume-inefficient—they generally require multiple chips, packaging, wires, and external transducers, and batteries are often needed for energy storage. A constant trend in electronics has been tighter integration of electronic components, often moving more and more functions onto the integrated circuit itself.

Researchers at Columbia Engineering report that they have built what they say is the world’s smallest single-chip system, consuming a total volume of less than 0.1 mm3. The system is as small as a dust mite and visible only under a microscope. In order to achieve this, the team used ultrasound to both power and communicate with the device wirelessly.

Chips shown in the tip of a hypodermic needle

We wanted to see how far we could push the limits on how small a functioning chip we could make,” said the study’s leader Ken Shepard, Lau Family professor of electrical engineering and professor of biomedical engineering. “This is a new idea of ‘chip as system’—this is a chip that alone, with nothing else, is a complete functioning electronic system. This should be revolutionary for developing wireless, miniaturized implantable medical devices that can sense different things, be used in clinical applications, and eventually approved for human use.”

The study was published online May 7 in Science Advances.


How to Convert Carbon Dioxide (CO2) into Fuels

If the CO2 content of the atmosphere is not to increase any further, carbon dioxide must be converted into something else. However, as CO2 is a very stable molecule, this can only be done with the help of special catalysts. The main problem with such catalysts has so far been their lack of stability: after a certain time, many materials lose their catalytic properties.

At TU Wien (Austria), research is being conducted on a special class of minerals – the perovskites, which have so far been used for solar cells, as anode materials or electronic components rather than for their catalytic properties. Now scientists at TU Wien have succeeded in producing a special perovskite that is excellently suited as a catalyst for converting CO2 into other useful substances, such as synthetic fuels. The new perovskite catalyst is very stable and also relatively cheap, so it would be suitable for industrial use.

We are interested in the so-called reverse water-gas shift reaction,” says Prof. Christoph Rameshan from the Institute of Materials Chemistry at TU Wien. “In this process, carbon dioxide and hydrogen are converted into water and carbon monoxide. You can then process the carbon monoxide further, for example into methanol, other chemical base materials or even into fuel.”

This reaction is not new, but it has not really been implemented on an industrial scale for CO2 utilisation. It takes place at high temperatures, which contributes to the fact that catalysts quickly break down. This is a particular problem when it comes to expensive materials, such as those containing rare metals.

Christoph Rameshan and his team investigated how to tailor a material from the class of perovskites specifically for this reaction, and he was successful: “We tried out a few things and finally came up with a perovskite made of cobalt, iron, calcium and neodymium that has excellent properties,” says Rameshan.

Because of its crystal structure, the perovskite allows certain atoms to migrate through it. For example, during catalysis, cobalt atoms from the inside of the material travel towards the surface and form tiny nanoparticles there, which are then particularly chemically active. At the same time, so-called oxygen vacancies form – positions in the crystal where an oxygen atom should actually sit. It is precisely at these vacant positions that CO2 molecules can dock particularly well, in order to then be dissociated into oxygen and carbon monoxide.

We were able to show that our perovskite is significantly more stable than other catalysts,” says Christoph Rameshan. “It also has the advantage that it can be regenerated: If its catalytic activity does wane after a certain time, you can simply restore it to its original state with the help of oxygen and continue to use it.

Initial assessments show that the catalyst is also economically promising. “It is more expensive than other catalysts, but only by about a factor of three, and it is much more durable,” says Rameshan. “We would now like to try to replace the neodymium with something else, which could reduce the cost even further.“Theoretically, you could use such technologies to get CO2 out of the atmosphere – but to do that you would first have to concentrate the carbon dioxide, and that requires a considerable amount of energy. It is therefore more efficient to first convert CO2 where it is produced in large quantities, such as in industrial plants. “You could simply add an additional reactor to existing plants that currently emit a lot of CO2, in which the CO2 is first converted into CO and then processed further,” says Christoph Rameshan. Instead of harming the climate, such an industrial plant would then generate additional benefits.


Highly Efficient Supercapacitors Better Than Batteries

A team working with Roland Fischer, Professor of Chemistry at the Technical University Munich (TUM) in Germany has developed a highly efficient supercapacitor. The basis of the energy storage device is a novel, powerful and also sustainable graphene hybrid material that has comparable performance data to currently utilized batteries.

Usually, energy storage is associated with batteries and accumulators that provide energy for electronic devices. However, in laptops, cameras, cellphones or vehicles, so-called supercapacitors are increasingly installed these days.

Unlike batteries they can quickly store large amounts of energy and put it out just as fast. If, for instance, a train brakes when entering the station, supercapacitors are storing the energy and provide it again when the train needs a lot of energy very quickly while starting up. However, one problem with supercapacitors to date was their lack of energy density. While lithium accumulators reach an energy density of up to 265 Kilowatt hours (KW/h), supercapacitors thus far have only been delivering a tenth thereof.

The team working with TUM chemist Roland Fischer has now developed a novel, powerful as well as sustainable graphene hybrid material for supercapacitors. It serves as the positive electrode in the energy storage device. The researchers are combining it with a proven negative electrode based on titanium and carbon. The new energy storage device does not only attain an energy density of up to 73 Wh/kg, which is roughly equivalent to the energy density of an nickel metal hydride battery, but also performs much better than most other supercapacitors at a power density of 16 kW/kg. The secret of the new supercapacitor is the combination of different materials – hence, chemists refer to the supercapacitor as “asymmetrical.”

The researchers are betting on a new strategy to overcome the performance limits of standard materials – they utilize hybrid materials. “Nature is full of highly complex, evolutionarily optimized hybrid materials – bones and teeth are examples. Their mechanical properties, such as hardness and elasticity were optimized through the combination of various materials by nature,” says Roland Fischer.

The abstract idea of combining basic materials was transferred to supercapacitors by the research team. As a basis, they used the novel positive electrode of the storage unit with chemically modified graphene and combined it with a nano-structured metal organic framework, a so-called MOF.

World’s Smallest Atom-Memory Unit Created

Faster, smaller, smarter and more energy-efficient chips for everything from consumer electronics to big data to brain-inspired computing could soon be on the way after engineers at The University of Texas at Austin created the smallest memory device yet. And in the process, they figured out the physics dynamic that unlocks dense memory storage capabilities for these tiny devices.

The research published recently in Nature Nanotechnology builds on a discovery from two years ago, when the researchers created what was then the thinnest memory storage device. In this new work, the researchers reduced the size even further, shrinking the cross section area down to just a single square nanometer. Getting a handle on the physics that pack dense memory storage capability into these devices enabled the ability to make them much smaller. Defects, or holes in the material, provide the key to unlocking the high-density memory storage capability.

When a single additional metal atom goes into that nanoscale hole and fills it, it confers some of its conductivity into the material, and this leads to a change or memory effect,” said Deji Akinwande, professor in the Department of Electrical and Computer Engineering.

Though they used molybdenum disulfide – also known as MoS2 – as the primary nanomaterial in their study, the researchers think the discovery could apply to hundreds of related atomically thin materials.

The race to make smaller chips and components is all about power and convenience. With smaller processors, you can make more compact computers and phones. But shrinking down chips also decreases their energy demands and increases capacity, which means faster, smarter devices that take less power to operate.

The results obtained in this work pave the way for developing future generation applications that are of interest to the Department of Defense, such as ultra-dense storage, neuromorphic computing systems, radio-frequency communication systems and more,” said Pani Varanasi, program manager for the U.S. Army Research Office, which funded the research.

The original device – dubbed “atomristor” by the research team – was at the time the thinnest memory storage device ever recorded, with a single atomic layer of thickness. But shrinking a memory device is not just about making it thinner but also building it with a smaller cross-sectional area. “The scientific holy grail for scaling is going down to a level where a single atom controls the memory function, and this is what we accomplished in the new study,” Akinwande said.


Beyond Moore’s Law

A team of researchers based in Manchester, the Netherlands, Singapore, Spain, Switzerland and the USA has published a new review on a field of computer device development known as spintronics, which could use graphene as a building block for next-generation electronics. Recent theoretical and experimental advances and phenomena in studies of electronic spin transport in graphene and related two-dimensional (2D) materials have emerged as a fascinating area of research and development.

Spintronics is the combination of electronics and magnetism at nanoscale and could allow electronic development at speeds exceeding Moore’s law, which observes that computer processing power roughly doubles every two years, while the price halves. Spintronic devices may offer higher energy efficiency and lower dissipation as compared to conventional electronics, which rely on charge currents. In principle, we could have phones and tablets operating with spin-based transistors and memories, greatly improving speed and storage capacity.

Since its isolation in 2004, graphene has opened the door for other 2D materials. Researchers can then use these materials to create stacks of 2D materials called heterostructures. These can be combined with graphene to create new ‘designer materials‘ to produce applications originally limited to science fiction. As published in APS Journal Review of Modern Physics, the review focuses on the new perspectives provided by heterostructures and their emergent phenomena, including proximity-enabled spin-orbit effects, coupling spin to light, electrical tunability and 2D magnetism. The average person already encounters spintronics in laptops and PCs, which are already using spintronics in the form of the magnetic sensors in the reading heads of hard disk drives. These sensors are also used in the automotive industry.

The continuous progress in graphene spintronics, and more broadly in 2D heterostructures, has resulted in the efficient creation, transport and detection of spin information using effects previously inaccessible to graphene alone” said Dr Ivan Vera Marun, Lecturer in Condensed Matter Physics at The University of Manchester.

As efforts on both the fundamental and technological aspects continue, we believe that ballistic spin transport will be realised in 2D heterostructures, even at room temperature. Such transport would enable practical use of the quantum mechanical properties of electron wave functions, bringing spins in 2D materials to the service of future quantum computation approaches.”

Controlled spin transport in graphene and other two-dimensional materials has become increasingly promising for applications in devices. Of particular interest are custom-tailored heterostructures, known as van der Waals heterostructures, that consist of stacks of two-dimensional materials in a precisely controlled order.

Billions of spintronic devices such as sensors and memories are already being produced. Every hard disk drive has a magnetic sensor that uses a flow of spins, and magnetic random access memory (MRAM) chips are becoming increasingly popular.


On Mars or Earth, biohybrid can turn CO2 into new products

If humans ever hope to colonize Mars, the settlers will need to manufacture on-planet a huge range of organic compounds, from fuels to drugs, that are too expensive to ship from Earth. University of California, Berkeley, and Lawrence Berkeley National Laboratory (Berkeley Lab) chemists have a plan for that.

For the past eight years, the researchers have been working on a hybrid system combining bacteria and nanowires that can capture the energy of sunlight to convert carbon dioxide and water into building blocks for organic molecules. Nanowires are thin silicon wires about one-hundredth the width of a human hair, used as electronic components, and also as sensors and solar cells.

A device to capture carbon dioxide from the air and convert it to useful organic products. On left is the chamber containing the nanowire/bacteria hybrid that reduces CO2 to form acetate. On the right is the chamber where oxygen is produced

On Mars, about 96% of the atmosphere is CO2. Basically, all you need is these silicon semiconductor nanowires to take in the solar energy and pass it on to these bugs to do the chemistry for you,” said project leader Peidong Yang, professor of chemistry and Energy at UC Berkeley. “For a deep space mission, you care about the payload weight, and biological systems have the advantage that they self-reproduce: You don’t need to send a lot. That’s why our biohybrid version is highly attractive.”

The only other requirement, besides sunlight, is water, which on Mars is relatively abundant in the polar ice caps and likely lies frozen underground over most of the planet, said Yang, who is a senior faculty scientist at Berkeley Lab and director of the Kavli Energy Nanoscience Institute.

The biohybrid can also pull carbon dioxide from the air on Earth to make organic compounds and simultaneously address climate change, which is caused by an excess of human-produced CO2 in the atmosphere.

In a new paper published in the journal Joule, the researchers report a milestone in packing these bacteria (Sporomusa ovata) into a “forest of nanowires” to achieve a record efficiency: 3.6% of the incoming solar energy is converted and stored in carbon bonds, in the form of a two-carbon molecule called acetate: essentially acetic acid, or vinegar.


Bacteria Becomes Resistant When Exposed To Li-Ion Nanoparticles

Over the last two decades, nanotechnology has improved many of the products we use every day from microelectronics to sunscreens. Nanoparticles (particles that are just a few hundred atoms in size) are ending up in the environment by the ton, but scientists are still unclear about the long-term effects of these super-small nanoparticles. In a first-of-its-kind study, researchers have shown that nanoparticles may have a bigger impact on the environment than previously thought.

Researchers from the National Science Foundation Center for Sustainable Nanotechnology, led by scientists at the University of Minnesota, found that a common, non-disease-causing bacteria found in the environment, called Shewanella oneidensis MR-1, developed rapid resistance when repeatedly exposed to nanoparticles used in making lithium ion batteries, the rechargeable batteries used in portable electronics and electric vehicles. Resistance is when the bacteria can survive at higher and higher quantities of the materials, which means that the fundamental biochemistry and biology of the bacteria is changing.

At many times throughout history, materials and chemicals like asbestos or DDT have not been tested thoroughly and have caused big problems in our environment,” said Erin Carlson, a University of Minnesota chemistry associate professor in the University’s College of Science and Engineering and the lead author of the study. “We don’t know that these results are that dire, but this study is a warning sign that we need to be careful with all of these new materials, and that they could dramatically change what’s happening in our environment.”

Carlson said the results of this study are unusual because typically when we talk about bacterial resistance it is because we’ve been treating the bacteria with antibiotics. The bacteria become resistant because we are trying to kill them, she said. In this case, the nanoparticles used in lithium ion batteries were never made to kill bacteria.

The research is published in Chemical Science, a peer-reviewed journal of the Royal Society of Chemistry.


Bacteria trapped — and terminated — by graphene filter

Airborne bacteria may see what looks like a comfy shag carpet on which to settle. But it’s a trapRice University scientists have transformed their laser-induced graphene (LIG) into self-sterilizing filters that grab pathogens out of the air and kill them with small pulses of electricity. The flexible filter developed by the Rice lab of chemist James Tour may be of special interest to hospitalsAccording to the Centers for Disease Control and Prevention, patients have a 1-in-31 chance of acquiring a potentially antibiotic-resistant infection during hospitalization. The device described in the American Chemical Society journal ACS Nano captures bacteria, fungi, fungi, prions, endotoxins and other biological contaminants carried by droplets, aerosols and particulate matter. The filter then prevents the microbes and other contaminants from proliferating by periodically heating up to 350 degrees Celsius (662 degrees Fahrenheit), enough to obliterate pathogens and their toxic byproducts. The filter requires little power, and heats and cools within seconds.

LIG is a conductive foam of pure, atomically thin carbon sheets synthesized through heating the surface of a common polyimide sheet with an industrial laser cutter. The process discovered by Tour’s lab in 2014 has led to a range of applications for electronics, triboelectric nanogenerators, composites, electrocatalysis and even art. Like all pure graphene, the foam conducts electricity. When electrified, Joule heating raises the filter’s temperature above 300 C, enough to not only kill trapped pathogens but also to decompose toxic byproducts that can feed new microorganisms and activate the human immune system. The researchers suggested a single, custom-fit LIG filter could be efficient enough to replace the two filter beds currently required by federal standards for hospital ventilation systems.

Seen in an electron microscope image, micron-scale sheets of graphene created at Rice University form a two-layer air filter that traps pathogens and then kills them with a modest burst of electricity

So many patients become infected by bacteria and their metabolic products, which for example can result in sepsis while in the hospital,” Tour said. “We need more methods to combat the airborne transfer of not just bacteria but also their downstream products, which can cause severe reactions among patients.

“Some of these products, like endotoxins, need to be exposed to temperatures of 300 degrees Celsius in order to deactivate them,” a purpose served by the LIG filter, he added. “This could significantly lessen the transfer of bacteria-generated molecules between patients, and thereby lower the ultimate costs of patient stays and lessen sickness and death from these pathogens.”

The lab tested LIG filters with a commercial vacuum filtration system, pulling air through at a rate of 10 liters per minute for 90 hours, and found that Joule heating successfully sanitized the filters of all pathogens and byproducts. Incubating used filters for an additional 130 hours revealed no subsequent bacterial growth on the heated units, unlike control LIG filters that had not been heated.

Bacteria culturing experiments performed on a membrane downstream from the LIG filter indicated that bacteria are unable to permeate the LIG filter,” said Rice sophomore John Li, co-lead author of the paper with postdoctoral researcher Michael Stanford. Stanford noted the sterilization feature “may reduce the frequency with which LIG filters would need to be replaced in comparison to traditional filters.” Tour suggested LIG air filters could also find their way into commercial aircraft.


Transparent and Flexible Battery for Power Generation and Storage at Once

DGIST research group in South Korea  developed single-layer graphene based multifunctional transparent devices  Various use of electronics and skin-attachable devices are expected with the development of transparent battery that can both generate and store power.The scientists in the Smart Textile Research Group developed film-type graphene based multifunctional transparent energy devices.

The team actively used ‘single-layered graphene film’ as electrodes in order to develop transparent devices. Due to its excellent electrical conductivity and light and thin characteristics, single-layered graphene  film is perfect for electronics that require batteries. By using high-molecule nano-mat that contains semisolid electrolyte, the research team succeeded in increasing transparency (maximum of 77.4%) to see landscape and letters clearly.

Furthermore, the researchers designed structure for electronic devices to be self-charging and storing by inserting energy storage panel inside the upper layer of power devices and energy conversion panel inside the lower panel. They even succeeded in manufacturing electronics with touch-sensing systems by adding a touch sensor right below the energy storage panel of the upper layer.

We decided to start this research because we were amazed by transparent smartphones appearing in movies. While there are still long ways to go for commercialization due to high production costs, we will do our best to advance this technology further as we made this success in the transparent energy storage field that has not had any visible research performances”, explains Changsoon Choi from the Smart Textile Research Group, and co-author of the paper published on the online edition of ACS Applied Materials & Interfaces.

The findings were also conducted as a joint research with various organisations such as Yonsei University, Hanyang University, and the Korea Institute of Industrial Technology (KITECH).


3D Printed Metamaterials With Super Optical Properties

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is possible using conventional optical or electronic materials. The fabrication methods developed by the researchers demonstrate the potential, both present and future, of 3D printing to expand the range of geometric designs and material composites that lead to devices with novel optical properties. In one case, the researchers drew inspiration from the compound eye of a moth to create a hemispherical device that can absorb electromagnetic signals from any direction at selected wavelengths.

The geometry of a moth’s eye provides inspiration for a 3D printed antenna that absorbs specific microwave frequencies from any direction

Metamaterials extend the capabilities of conventional materials in devices by making use of geometric features arranged in repeating patterns at scales smaller than the wavelengths of energy being detected or influenced. New developments in 3D printing technology are making it possible to create many more shapes and patterns of metamaterials, and at ever smaller scales. In the study, researchers at the Nano Lab at Tufts describe a hybrid fabrication approach using 3D printing, metal coating and etching to create metamaterials with complex geometries and novel functionalities for wavelengths in the microwave range. For example, they created an array of tiny mushroom shaped structures, each holding a small patterned metal resonator at the top of a stalk. This particular arrangement permits microwaves of specific frequencies to be absorbed, depending on the chosen geometry of the “mushrooms” and their spacing. Use of such metamaterials could be valuable in applications such as sensors in medical diagnosis and as antennas in telecommunications or detectors in imaging applications.

The research has been published in the journal Microsystems & Nanoengineering (Springer Nature).