Electronics - Page 26

Researchers at MIT, NIST, University of Maryland, Imperial College London, and the National Institute for Materials Science (NIMS) in Japan have created a "whispering gallery" effect for electrons in a sheet of graphene, making it possible to precisely control a region that reflects electrons within the material. This accomplishment could help in heralding new kinds of electronic lenses, as well as quantum-based devices that combine electronics and optics.

The process uses a probe (the same as in STM - Scanning Tunneling Miscroscopy) that allows control of both the location and the size of the reflecting region within graphene. When the sharp tip is positioned over a sheet of graphene, it produces a circular barrier on the sheet that "acts as a perfect curved mirror" for electrons, according to the scientists, reflecting them back toward the center of the circle. This controllable reflectivity is similar to so-called "whispering gallery" confinement modes that have been used in optical and acoustic systems - but these have not been tunable or adjustable.

Researchers at Northwestern University developed a solution-based graphene ink that can be 3D-printed under ambient conditions via simple extrusion into arbitrarily shaped, electrically conductive, mechanically resilient and biocompatible scaffolds with filaments ranging in diameter from 100 to 1000 µm. The resulting material is very flexible, can be easily printed into small or large scale (multiple centimeters) objects, and may hold the potential for printing electronics as well as body parts.

The printed objects contain a high level of graphene while maintaining structural integrity, which is enabled by the particular biocompatible elastomer binder PLG that was chosen in combination with the solvent system. This could be a revolutionary method for producing biomaterials for nervous tissue regeneration, and also biomaterials that are scalable and not very expensive to produce since these novel 3D printable graphene inks are relatively easy to produce, can be rapidly fabricated into an infinite variety of forms (including patient specific implants), and are also surgically friendly (can be adjusted to size and sutured to surrounding tissue).

Researchers at the University of Guangzhou, China, managed to improve the capacitance of supercapacitors by nearly 1000-fold compared with that of the laminated or wrinkled CVD graphene-film-based supercapacitors. To achieve this, the researchers integrated transparency into freestanding, flexible graphene paper (FFT-GP). These supercapacitors's capacitance is also about ten times better than previously reported values for transparent and flexible supercapacitors based on pure carbon materials. However, some carbon-based nontransparent supercapacitors still perform better than the FFT-GP-based transparent supercapacitor. 

The improved performance is mainly based on the prism-like graphene building blocks that the FFT-GP is made of. The hollow structures of the graphene that give the material its transparency also provide additional space for chemical reactions to occur compared to other materials. Also, the aligned and interconnected prism-like structures provide a wide open path for ions and electrons to travel along and the good charge transport leads to an overall better performance.

Researchers at the UC San Diego invented a graphene-based way of fabricating nanostructures that contain well-defined, atomic-sized gaps. Such structures could be used to detect single molecules associated with certain diseases and may lay the foundation for miniature microprocessors.

The ability to create these nanogaps is highly desirable in fabricating nanoscale structures, which are typically used as components in optic and electronic devices. By decreasing the spacing between electronic circuits on a microchip, for example, one can fit more circuits on the same chip to produce a device with enhanced computing power. The scientists managed to create nanogaps between two nanostructures, that are much smaller than previously ones by using a graphene spacer, which can be etched away to create the gap.  

UK-based Thomas Swan is a privately held global chemical manufacturing company that currently has a 1kg per day pilot line as well as a vision of being the most trusted supplier of high quality graphene on the market. 

The company's plans for 2015 include expanding its graphene production capacity to 10 tonnes per year (supported by Horizon 2020 funding) and establishing collaborations to develop applications in printed electronics, touch panels and energy storage devices (supported by Innovate UK funding).

Researchers at the University of Illinois designed a single-step method of creating textures in graphene ("crumpling") to allow for larger surface areas, thus tapping into graphene's benefits for electronics. The scientists believe that "crumpled" graphene may also be used as high surface area electrodes for batteries and supercapacitors. As a coating layer, the 3D graphene could allow omniphobic/anti-bacterial surfaces for advanced coating applications.

The "crumpling" process is based on a known shape-memory polymer substrate (a material capable of returning to its original shape after being distorted, mostly by thermal means). The thermoplastic nature of the substrate also allows for the crumpled graphene morphology to be arbitrarily re-flattened at the same elevated temperature for the crumpling process. 

UK-based FlexEnable has recently joined the Graphene Flagship and announced its plans for this year, which will mainly focus on developing new use cases for graphene in flexible electronics including highly conductive interconnect lines and barrier films.

Starting April 2016, the Graphene Flagship is scheduled to move into its core project phase, where FlexEnable’s expertise in industrializing flexible electronics will be utilized to harness the potential of graphene and other 2d materials. FlexEnable’s Cambridge fab will play an important role in showcasing graphene’s performance over surfaces of all sizes, including large areas as well as in the development of advanced product concepts.

Researchers at The Institute of Advanced Composite Materials at Korea Institute of Science and Technology (KIST) and The Seoul National University announced that they have successfully developed a manufacturing process for high molecular composite material with even distribution of graphene without using solvent.

Researchers developed this composite material after applying heat to a mixture of cyclic butylene terephthalate (CBT) with graphene particles. With statistical calculations using a cross sectional image of graphene, the researchers evaluated the distribution of graphene with average inter-particle distance and standard deviation.

A team of physicists led by Philippe Lambin from the Université de Namur in Belgium has found that a graphene plane can provide an effective absorbent shield against microwaves. The scientists demonstrated that the conductivity of several graphene layers grows when thin polymer spacers separate them. Maximum microwave absorption in the Ka communications band between 26.5 and 40 GHz is achieved with six graphene planes separated by layers of poly-methyl methacrylate (PMMA), a transparent plastic also known as acrylic glass.

A single layer of graphene can absorb up to 25% of incident microwave radiation. With a multilayer graphene/PMMA arrangement, the absorption rises to 50%. This can be explained by analysing the transmission and reflection of a plane wave at the interface between two dielectric media, when the interface contains a thin conducting layer. In this way, the researchers were able to optimise their graphene-PMMA structures for maximum absorption, with the results confirmed by electromagnetic testing.

Back in 2013, Rice scientists developed a simple method to reduce coal into graphene quantum dots (GQDs). Now, these Rice researchers have found a way to engineer these GQDs for specific semiconducting properties in two separate processes.

The researchers' work demonstrates precise control over the graphene oxide dots' band gap, the very property that makes them semiconductors. By sorting the QDs through ultrafiltration, it was found possible to produce quantum dots with specific semiconducting properties. The second process involved direct control of the reaction temperature in the oxidation process that reduced coal to quantum dots. The researchers found hotter temperatures produced smaller dots that had different semiconducting properties. The dots in these experiments came from treatment of anthracite, a kind of coal. The processes produce batches in specific sizes between 4.5 and 70 nanometers in diameter.