‘Spray-On’ Memory for Paper, Fabric, Plastic

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 clothingDuke 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. 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.

PrintingMemory

Duke University researchers have developed a new “spray-on” digital memory (upper left) that could be used to build programmable electronics on flexible materials like paper, plastic or fabric. They used LEDS to demonstrate a simple application.

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 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.

Source: https://today.duke.edu/

Nano Printing Heralds NanoComputers Era

A new technique using liquid metals to create integrated circuits that are just atoms thick could lead to the next big advance for electronics. The process opens the way for the production of large wafers around 1.5 nanometres in depth (a sheet of paper, by comparison, is 100,000nm thick). Other techniques have proven unreliable in terms of quality, difficult to scale up and function only at very high temperatures – 550 degrees or more.

Professor Kourosh Kalantar-zadeh, from RMIT’s School of Engineering in Australia , led the project with  colleagues from RMIT and researchers from CSIRO, Monash University, North Carolina State University and the the University of California, He observed that the electronics industry had “hit a barrier.

nano printing

The fundamental technology of car engines has not progressed since 1920 and now the same is happening to electronics. Mobile phones and computers are no more powerful than five years ago. That is why this new 2D printing technique is so important – creating many layers of incredibly thin electronic chips on the same surface dramatically increases processing power and reduces costsIt will allow for the next revolution in electronics.

Benjamin Carey, a researcher with RMIT and the CSIRO, said creating electronic wafers just atoms thick could overcome the limitations of current chip production. It could also produce materials that were extremely bendable, paving the way for flexible electronics. “However, none of the current technologies are able to create homogenous surfaces of atomically thin semiconductors on large surface areas that are useful for the industrial scale fabrication of chips.  Our solution is to use the metals gallium and indium, which have a low melting point.  These metals produce an atomically thin layer of oxide on their surface that naturally protects them. It is this thin oxide which we use in our fabrication method,”  explains Carey.

By rolling the liquid metal, the oxide layer can be transferred on to an electronic wafer, which is then sulphurised. The surface of the wafer can be pre-treated to form individual transistors.  We have used this novel method to create transistors and photo-detectors of very high gain and very high fabrication reliability in large scale,” he adds.

The paper outlining the new technique has been published in the journal Nature Communications.

Source: http://www.rmit.edu.au/

Scalable Production of Conductive Graphene Inks

Conductive inks based on graphene and layered materials are key for low-cost manufacturing of flexible electronics, novel energy solutions, composites and coatings. A new method for liquid-phase exfoliation of graphite paves the way for scalable production.

Conductive inks are useful for a range of applications, including printed and flexible electronics such as radio frequency identification (RFID) antennas, transistors or photovoltaic cells. The advent of the internet of things is predicted to lead to new connectivity within everyday objects, including in food packaging. Thus, there is a clear need for cheap and efficient production of electronic devices, using stable, conductive and non-toxic components. These inks can also be used to create novel composites, coatings and energy storage devices.

A new method for producing high quality conductive graphene inks with high concentrations has been developed by researchers working at the Cambridge Graphene Centre at the University of Cambridge, UK. The novel method uses ultrahigh shear forces in a microfluidisation process to exfoliate graphene flakes from graphite. The process converts 100% of the starting graphite material into usable flakes for conductive inks, avoiding the need for centrifugation and reducing the time taken to produce a usable ink. The research, published in ACS Nano, also describes optimisation of the inks for different printing applications, as well as giving detailed insights into the fluid dynamics of graphite exfoliation.

graphene scalable production

“This important conceptual advance will significantly help innovation and industrialization. The fact that the process is already licensed and commercialized indicates how it is feasible to cut the time from lab to market” , said Prof. Andrea Ferrari, Director of the Cambridge Graphene Centre.

Source: http://www.graphene.cam.ac.uk/

Smart Threads For Clothing And Robots

Fabrics containing flexible electronics are appearing in many novel products, such as clothes with in-built screens and solar panels. More impressively, these fabrics can act as electronic skins that can sense their surroundings and could have applications in robotics and prosthetic medicine. King Abdullah University of Science and Technology (KAUST – Saudi Arabia) researchers have now developed smart threads that detect the strength and location of pressures exerted on them1. Most flexible sensors function by detecting changes in the electrical properties of materials in response to pressure, temperature, humidity or the presence of gases. Electronic skins are built up as arrays of several individual sensors. These arrays currently need complex wiring and data analysis, which makes them too heavy, large or expensive for large-scale production.

Yanlong Tai and Gilles Lubineau from the University’s Division of Physical Science and Engineering have found a different approach. They built their smart threads from cotton threads coated with layers of one of the miracle materials of nanotechnology: single-walled carbon nanotubes (SWCNTs).

smart threadsThe twisted smart threads developed by KAUST researchers can be woven into pressure-sensitive electronic skin fabrics for use in novel clothing, robots or medical prosthetics

Cotton threads are a classic material for fabrics, so they seemed a logical choice,” said Lubineau. “Networks of nanotubes are also known to have piezoresistive properties, meaning their electrical resistance depends on the applied pressure.”

The researchers showed their threads had decreased resistance when subjected to stronger mechanical strains, and crucially the amplitude of the resistance change also depended on the thickness of the SWCNT coating.

These findings led the researchers to their biggest breakthrough: they developed threads of graded thickness with a thick SWCNT layer at one end tapering to a thin layer at the other end. Then, by combining threads in pairs—one with graded thickness and one of uniform thickness—the researchers could not only detect the strength of an applied pressure load, but also the position of the load along the threads.

Our system is not the first technology to sense both the strength and position of applied pressures, but our graded structure avoids the need for complicated electrode wirings, heavy data recording and analysis,” said Tai.

The researchers have used their smart threads to build two- and three-dimensional arrays that accurately detect pressures similar to those that real people and robots might be exposed to.
We hope that electronic skins made from our smart threads could benefit any robot or medical prosthetic in which pressure sensing is important, such as artificial hands,” said Lubineau.

https://discovery.kaust.edu.sa/

‘Self-Healing’ Gel Repairs Electronic Circuit

Researchers in the Cockrell School of Engineering at The University of Texas at Austin have developed a first-of-its-kind self-healing gel that repairs and connects electronic circuits, creating opportunities to advance the development of flexible electronics, biosensors and batteries as energy storage devices. Although technology is moving toward lighter, flexible, foldable and rollable electronics, the existing circuits that power them are not built to flex freely and repeatedly self-repair cracks or breaks that can happen from normal wear and tear.

Until now, self-healing materials have relied on application of external stimuli such as light or heat to activate repair. The UT Austinsupergel” material has high conductivity (the degree to which a material conducts electricity) and strong mechanical and electrical self-healing properties.

self-healed gelSelf-repaired supergel supports its own weight after being sliced in half

In the last decade, the self-healing concept has been popularized by people working on different applications, but this is the first time it has been done without external stimuli,” said mechanical engineering assistant professor Guihua Yu, who developed the gel. “There’s no need for heat or light to fix the crack or break in a circuit or battery, which is often required by previously developed self-healing materials.

Source: http://news.utexas.edu/

How To Integrate Graphene To Produce Solar Cells

Binghamton University researchers have demonstrated an eco-friendly process that enables unprecedented spatial control over the electrical properties of graphene oxide. This two-dimensional nanomaterial has the potential to revolutionize flexible electronics, solar cells and biomedical instruments.

By using the probe of an atomic force microscope to trigger a local chemical reaction, Jeffrey Mativetsky, assistant professor of physics at Binghamton University, and PhD student Austin Faucett showed that electrically conductive features as small as four nanometers can be patterned into individual graphene oxide sheets. One nanometer is about one hundred thousand times smaller than the width of a human hair.

graphene solar cells
Our approach makes it possible to draw nanoscale electrically-conductive features in atomically-thin insulating sheets with the highest spatial control reported so far,” said Mativetsky. “Unlike standard methods for manipulating the properties of graphene oxide, our process can be implemented under ambient conditions and is environmentally-benign, making it a promising step towards the practical integration of graphene oxide into future technologies.

 

The 2010 Nobel Prize in Physics was awarded for the discovery of graphene, an atomically-thin, two-dimensional carbon lattice with extraordinary electrical, thermal and mechanical properties. Graphene oxide is a closely-related two-dimensional material with certain advantages over graphene, including simple production and processing, and highly tunable properties. For example, by removing some of the oxygen from graphene oxide, the electrically insulating material can be rendered conductive, opening up prospects for use in flexible electronics, sensors, solar cells and biomedical devices.

Source: http://www.sciencedirect.com/
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http://www.eurekalert.org/

Electron Super Highway

TV screens that roll up. Roofing tiles that double as solar panels. Sun-powered cell phone chargers woven into the fabric of backpacks. A new generation of organic semiconductors may allow these kinds of flexible electronics to be manufactured at low cost, says University of Vermont physicist and materials scientist Madalina Furis. But the basic science of how to get electrons to move quickly and easily in these organic materials remains murky. To help, Furis and a team of UVM materials scientists have invented a new way to create what they are calling “an electron superhighway” in one of these materials — a low-cost blue dye called phthalocyanine — that promises to allow electrons to flow faster and farther in organic semiconductors.

Their discovery, reported Sept. 14 in the journal Nature Communications, will aid in the hunt for alternatives to traditional silicon-based electronics.

electron

Many of these types of flexible electronic devices will rely on thin films of organic materials that catch sunlight and convert the light into electric current using excited states in the material called “excitons.” Roughly speaking, an exciton is a displaced electron bound together with the hole it left behind. Increasing the distance these excitons can diffuse — before they reach a juncture where they’re broken apart to produce electrical current — is essential to improving the efficiency of organic semiconductors.

Using a new imaging technique, the UVM team was able to observe nanoscale defects and boundaries in the crystal grains in the thin films of phthalocyanine roadblocks in the electron highway.We have discovered that we have hills that electrons have to go over and potholes that they need to avoid,” Furis explains.

To find these defects, the UVM team — with support from the National Science Foundation — built a scanning laser microscope, “as big as a table” Furis says.

Marrying these two techniques together is new; it’s never been reported anywhere,” says Lane Manning ’08 a doctoral student in Furis’ lab and co-author on the new study. The scientists have now a deeper understanding of how the arrangement of molecules and the boundaries in the crystals influence the movement of excitons. It’s these boundaries that form a “barrier for exciton diffusion,” the team writes.

Source: http://www.uvm.edu/

Super Bendable Screen

From smartphones and tablets to computer monitors and interactive TV screens, electronic displays are everywhere. As the demand for instant, constant communication grows, so too does the urgency for more convenient portable devices — especially devices, like computer displays, that can be easily rolled up and put away, rather than requiring a flat surface for storage and transportation. A new Tel Aviv University (TAU) study, published recently in Nature Nanotechnology, suggests that a novel DNA-peptide structure can be used to produce thin, transparent, and flexible screens. The research, conducted by Prof. Ehud Gazit and doctoral student Or Berger of the Department of Molecular Microbiology at TAU‘s Faculty of Life Sciences, harnesses bionanotechnology to emit a full range of colors in one pliable pixel layer — as opposed to the several rigid layers that constitute today’s screens.
flexiblescreens
Researchers tested different combinations of peptides: short protein fragments, embedded with DNA elements which facilitate the self-assembly of a unique molecular architecture. Peptides and DNA are two of the most basic building blocks of life. Each cell of every life form is composed of such building blocks. In the field of bionanotechnology, scientists utilize these building blocks to develop novel technologies with properties not available for inorganic materials such as plastic and metal.

Our material is light, organic, and environmentally friendly,” said Prof. Gazit. “It is flexible, and a single layer emits the same range of light that requires several layers today. By using only one layer, you can minimize production costs dramatically, which will lead to lower prices for consumers as well.”
Once we discovered the DNA-like organization, we tested the ability of the structures to bind to DNA-specific fluorescent dyes,” said Berger. “To our surprise, the control sample, with no added dye, emitted the same fluorescence as the variable. This proved that the organic structure is itself naturally fluorescent.“.
Source: https://www.aftau.org/

Liquid-Metal Alloys For “Soft Robots”

New research shows how inkjet-printing technology can be used to mass-produce electronic circuits made of liquid-metal alloys for “soft robots” and flexible electronics. Elastic technologies could make possible a new class of pliable robots and stretchable garments that people might wear to interact with computers or for therapeutic purposes. However, new manufacturing techniques must be developed before soft machines become commercially feasible, said Rebecca Kramer, an assistant professor of mechanical engineering at Purdue University.
liquid robot
“We want to create stretchable electronics that might be compatible with soft machines, such as robots that need to squeeze through small spaces, or wearable technologies that aren’t restrictive of motion,” she said. “Conductors made from liquid metal can stretch and deform without breaking.

A new potential manufacturing approach focuses on harnessing inkjet printing to create devices made of liquid alloys.

inkjet pritingThis artistic rendering depicts electronic devices created using a new inkjet-printing technology to produce circuits made of liquid-metal alloys for “soft robots” and flexible electronics. Elastic technologies could make possible a new class of pliable robots and stretchable garments that people might wear to interact with computers or for therapeutic purposes.

This process now allows us to print flexible and stretchable conductors onto anything, including elastic materials and fabrics,” Kramer said.

Liquid metal in its native form is not inkjet-able,” he underscores. “So what we do is create liquid metal nanoparticles that are small enough to pass through an inkjet nozzle“.

After printing, the nanoparticles must be rejoined by applying light pressure, which renders the material conductive.
A research paper about the method will appear on April 18 in the journal Advanced Materials.
Source: http://www.purdue.edu/

Smart Bandage

Engineers at UC Berkeley are developing a new type of bandage that does far more than stanch the bleeding from a paper cut or scraped knee.

Associate professor Michel Maharbiz explains how the smart bandage works to detect bedsores. (UC Berkeley video by Roxanne Makasdjian and Phil Ebiner)
Thanks to advances in flexible electronics, the researchers, in collaboration with colleagues at UC San Francisco, have created a new “smart bandage” that uses electrical currents to detect early tissue damage from pressure ulcers, or bedsores, before they can be seen by human eyes – and while recovery is still possible.
The researchers exploited the electrical changes that occur when a healthy cell starts dying. They tested the thin, non-invasive bandage on the skin of rats and found that the device was able to detect varying degrees of tissue damage consistently across multiple animals.

smartbandage The smart bandage is fabricated by printing gold electrodes onto a thin piece of plastic. This flexible sensor uses impedance spectroscopy to detect bedsores that are invisible to the naked eye
We set out to create a type of bandage that could detect bedsores as they are forming, before the damage reaches the surface of the skin,” said Michel Maharbiz, a UC Berkeley associate professor of electrical engineering and computer sciences and head of the smart-bandage project. “We can imagine this being carried by a nurse for spot-checking target areas on a patient, or it could be incorporated into a wound dressing to regularly monitor how it’s healing.
The findings, published in the journal Nature Communications, could provide a major boost to efforts to stem a health problem that affects an estimated 2.5 million U.S. residents at an annual cost of $11 billion.

Source: http://newscenter.berkeley.edu/

How To process Graphene To Produce Solar Cells

A new technique invented at the California Institute of Technology (Caltech) to produce graphene — a material made up of an atom-thick layer of carbon, at room temperature, could help pave the way for commercially feasible graphene-based solar cells and light-emitting diodes, large-panel displays, and flexible electronics.

With this new technique, we can grow large sheets of electronic-grade graphene in much less time and at much lower temperatures,” says Caltech staff scientist David Boyd, who developed the method. Boyd is the first author of a new study, published in the journal Nature Communications, detailing the new manufacturing process and the novel properties of the graphene it produces.

graphene2014
Graphene revolutionizes a variety of engineering and scientific fields due to its unique properties, which include a tensile strength 200 times stronger than steel and an electrical mobility that is two to three orders of magnitude better than silicon. The electrical mobility of a material is a measure of how easily electrons can travel across its surface. However, achieving these properties on an industrially relevant scale has proven to be complicated. Existing techniques require temperatures that are much too hot — 1,800 degrees Fahrenheit, or 1,000 degrees Celsius — for incorporating graphene fabrication with current electronic manufacturing. Additionally, high-temperature growth of graphene tends to induce large, uncontrollably distributed strain—deformation—in the material, which severely compromises its intrinsic properties.

Previously, people were only able to grow a few square millimeters of high-mobility graphene at a time, and it required very high temperatures, long periods of time, and many steps,” says Caltech physics professor Nai-Chang Yeh, the Fletcher Jones Foundation Co-Director of the Kavli Nanoscience Institute and the corresponding author of the new study. “Our new method can consistently produce high-mobility and nearly strain-free graphene in a single step in just a few minutes without high temperature. We have created sample sizes of a few square centimeters, and since we think that our method is scalable, we believe that we can grow sheets that are up to several square inches or larger, paving the way to realistic large-scale applications.”

Source: http://www.caltech.edu/

Flexible E-readers In Your Pocket

Engineers would love to create flexible electronic devices, such as e-readers that could be folded to fit into a pocket. One approach involves designing circuits based on electronic fibers known as carbon nanotubes (CNTs) instead of rigid silicon chips.

But reliability is essential. Most silicon chips are based on a type of circuit design that allows them to function flawlessly even when the device experiences power fluctuations. However, it is much more challenging to do so with CNT circuits.

But now a team at Stanford has developed a process to create flexible chips that can tolerate power fluctuations in much the same way as silicon circuitry.

This is the first time anyone has designed flexible CNT circuits that have both high immunity to electrical noise and low power consumption, ” said Zhenan Bao, a professor of chemical engineering at Stanford.

In principle, CNTs should be ideal for making flexible electronic circuitry. These ultra-thin carbon filaments have the physical strength to take the wear and tear of bending and the electrical conductivity to perform any electronic task.

But until this recent work from the Stanford team, flexible CNT circuits didn’t have the reliability and power-efficiency of rigid silicon chips.

Huiliang (Evan) Wang, a graduate student in Bao’s lab, and Peng Wei, a previous postdoctoral scholar in Bao’s lab, were the lead authors of the paper. Bao’s team also included Yi Cui, an associate professor of materials science at Stanford, and Hye Ryoung Lee, a graduate student in his lab.
The Bao Lab reported its findings in the Proceedings of the National Academy of Sciences.

Source: http://engineering.stanford.edu/