Electronics - Page 25

Researchers from the University of Illinois at Urbana-Champaign have developed a new approach for forming 3D shapes from flat sheets of graphene. This technique may open the door to future integrated systems of graphene-MEMS hybrid devices and flexible electronics.

The study demonstrated graphene integration to a variety of different microstructured geometries, including pyramids, pillars, domes, inverted pyramids, and the 3D integration of gold nanoparticles (AuNPs)/graphene hybrid structures. The flexibility and 3D nature of the structures could enable biosensing devices which can be made in various shapes and carry many biological functions. The scientists also expect that the new 3D integration approach will facilitate advanced classes of hybrid devices between microelectromechanical systems (MEMS) and 2D materials for sensing and actuation.

An international research team, led by scientists at the National Institute of Standards and Technology's (NIST) Center for Nanoscale Science and Technology, has developed a technique for measuring crystal vibrations in graphene. 

Tunneling electrons from a scanning tunneling microscope tip excites phonons in graphene. The image shows the graphene lattice with blue arrows indicating the motion direction of that carbon atoms for one of the low energy phonon modes in graphene. (Image

In graphene, like in other crystals, when enough heat or other energy is applied, the forces that bond the atoms together cause the atoms to vibrate and spread the energy throughout the material. These vibrations, which have frequencies in the terahertz-range, are called phonons. Understanding phonon interactions can help gain knowledge on how to manipulate energy in a material, and can be crucial since learning effective ways to remove heat energy is vital to the continued miniaturization of electronics.

Carbon Sciences announced its plans to develop graphene-based devices for cloud computing. Graphene-based fiber optics components, such as photodetectors, fiber lasers and optical switches, are expected to unclog the existing bottlenecks and enable ultrafast communication in data centers for Cloud computing.

The company states that it is shifting its focus to high value, large market opportunities to apply the knowledge gained from years of exploring methods to produce low cost graphene. Carbon Sciences estimates that contrary to many other applications that are years away from finding commercial success, cloud computing can soon create one of the most significant market opportunities in the world. By exploiting the excellent optical and electrical properties of graphene, the company plans to develop next generation fiber optics components that are ultrafast, low power and low cost.

Researchers from the University of Maryland found that intercalating (embedding) sodium ions in a reduced graphene oxide (rGO) network, printed with graphene oxide (GO) ink, can significantly improve its performance as a transparent conductor in displays, solar cells and electronic devices.

The scientists used cost-effective materials and production techniques to receive a highly scalable printed electronics system that produces relatively inexpensive and stable conductors. The team theorizes the increased stability is due to the natural oxidation of sodium along the edges of the printed networks which forms a barrier that prevents ion loss. Networks printed with the ink exhibit up to 79 percent optical transmittance and 311 Ohms per square of sheet resistance.

An international team of researchers from Surrey’s Advanced Technology Institute (ATI), National Physical Laboratory (NPL) and the Institute of Electronic Materials Technology in Poland designed an innovative method for separating a layer (or "carpet", as they put it) of graphene from its supporting substance.

While traditional methods require separating graphene from a substrate (which leads to degradation of the mobility of the electrons), this research presents an breakthrough in that it enables the graphene layer to be ‘lifted’ from the substrate by forcing hydrogen molecules between the two layers. The researchers showed that the insertion of hydrogen molecules between epitaxial graphene and SiC promotes a dramatic change in the electronic properties of the material, leading to the change of the carrier type and significant increase in carrier mobility.

Scientists from the Department of Energy’s SLAC National Accelerator Laboratory and the Stanford Institute for Materials and Energy Sciences (SIMES) collaborated to study the effects of spiraling pulses of laser light on graphene. They discovered that such spiraling laser pulses can theoretically change the electronic properties of graphene, switching it back and forth from a metallic state (where electrons flow freely), to an insulating state.

Such ability could mean that it is possible to use light to encode information in a computer memory, for instance. The study, while theoretical, attempted to work in as close-to-real experimental conditions as possible, right down to the shape of the laser pulses. The team found that the laser's interaction with graphene yielded surprising results, producing a band gap and also inducing a quantum state in which the graphene has a so-called Chern number of either one or zero, which results from a phenomenon known as Berry curvature and offers another on/off state that scientists might be able to exploit.

Researchers at Northwestern University designed a method to print 3D structures using graphene nanoflakes, by developing a graphene-based ink that can be used to print large, robust 3D structures. This fast and efficient method may open up new opportunities for using graphene printed scaffolds and various other electronic or medical applications.

The relatively high volume of graphene flakes in the ink (60-70%), combined with the use of bio-compatible elastomer and evaporating solvents, grants the material electrical conductivity and mechanical strength, without making the printed objects brittle. Once the ink is extruded, one of the solvents in the system evaporates right away, causing the structure to solidify almost immediately. The presence of the other solvents and the interaction with the specific polymer binder chosen also has a significant contribution to its resulting flexibility and properties. Since it holds its shape, it is possible to build larger, well-defined objects.

Scientists at Rice University designed a boric acid-infused graphene microsupercapacitor with quadrupled ability to store an electrical charge, while greatly boosting its energy density. This design may see potential applications in wearable electronics, as well as many other flexible electronics uses.

The scientists used commercial lasers to create thin, flexible supercapacitors by burning patterns into common polymers. The laser burns away everything except for the carbon, to a depth of 20 microns on the top layer, which becomes a foam-like matrix of interconnected graphene flakes. They found that first infusing the polymer with boric acid, resulted in major performance advantages.

Researchers at the University of Manchester, along with UK graphene manufacturer BGT Materials, printed a radio frequency antenna using compressed graphene ink. The antenna worked well enough to make it practical for use in radio-frequency identification (RFID) tags and wireless sensors, according to the researchers. Furthermore, the antenna is flexible, environmentally friendly and could even be cheaply mass-produced. 

The research team found a binder-free way to increase the conductivity of graphene ink. They accomplished this by first printing and drying the ink, and then compressing it with a roller. Compressing the ink increased its conductivity by more than 50 times, and the resulting "graphene laminate" was almost two times more conductive than previous graphene ink made with a binder.

An international team of scientists, including ones from the University of Exeter, the Institute for Systems Engineering and Computers, Microsystems and Nanotechnology (INESC-MN) in Lisbon, the Universities of Lisbon and Aveiro in Portugal and the Belgian Textile Research Centre (CenTexBel) designed a new technique for embedding transparent and flexible graphene electrodes into fibers commonly used in the textile industry.

This could lead the way to creating wearable electronic devices such as clothing containing computers, phones and MP3 players, which are lightweight and durable. The scientists state that the possibilities for its use are endless, including textile GPS systems, biomedical monitoring, personal security or even communication tools for the sensory impaired.