Flexible - Page 5

Researchers at Rice University used computer models to demonstrate that twisting graphene alters its electrical properties, and produce what is known as a flexoelectric effect in which a material exhibits a spontaneous electrical polarization brought on by a strain.

When in flat sheet form, graphene's atoms have a balanced electrical charge. Putting a curve in the graphene plane, however, makes the electron clouds of the bonds on the concave side compress while on the convex side they stretch. This changes the electric dipole moment, which is a measure of the overall polarity and determines how polarized atoms interact with external electric fields. 

Researchers from the University of Exeter have designed a new method to produce graphene significantly cheaper and easier than previously production methods. The researchers claim that this high-quality, low cost graphene could pave the way for the development of the first truly flexible 'electronic skin', that could be used in robots.

The new method grows graphene in an industrial cold wall CVD system, a state-of-the-art piece of equipment recently developed by UK graphene company Moorfield. This nanoCVD system is based on a concept already used for other manufacturing purposes in the semiconductor industry. This new technique is said to grow graphene 100 times faster than conventional methods, reduce costs by 99% and have enhanced electronic quality. The research team used this new technique to create the first transparent and flexible touch-sensor that could enable the development of artificial skin for use in robot manufacturing as well as flexible electronics. 

A research team at the University of Michigan utilized Japanese paper cutting techniques, called kirigami, to create a new type of flexible conductor. The team believes that this technique may open up big possibilities for implantable medical devices, which have to flex and bend within the human body to work. Another option is gadgets that won't break when bending or flexing.

The first prototype of the kirigami stretchable conductor consisted of tracing paper covered in carbon nanotubes. The layout was quite simple, with cuts like rows of dashes. Later concepts were more intricate. for example, conductor sheets made out of graphene oxide, with etching cuts into the surface just a tenth of a millimeter long using laser beams and a plasma of oxygen ions and electrons.

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.

A team of scientists from the Electronics and Telecommunications Research Institute (ETRI) in Korea announced the successful development of a technology to make a washable, flexible and highly-sensitive textile-type gas sensor.

This technology is based on coating graphene using molecular adhesives to textile like nylon, cotton, or polyester so that textile can check whether or not gas exists in the air. When graphene oxides meet the NO2 found in methane gases at room temperatures, their resistivity changes based on the gas density. Consequently, when putting out a fire or entering an area in which air conditions are hard to determine, it will be possible for firefighters to check the condition of the air through a connected device by wearing work clothes with gas sensors made from textiles.

A team of scientists from Columbia, Seoul National University (SNU), and Korea Research Institute of Standards and Science (KRISS) reported the creation of an on-chip visible light source using graphene as a filament. Creating light in small structures on the surface of a chip is crucial for developing fully integrated 'photonic' circuits that do with light what is now done with electric currents in semiconductor integrated circuits.

The scientists attached small strips of graphene to metal electrodes, suspended the strips above the substrate, and passed a current through the filaments to cause them to heat up. The team refers to this design as 'the world's thinnest light bulb', a type of 'broadband' light emitter that can be integrated into chips and may pave the way towards the realization of atomically thin, flexible, and transparent displays, and graphene-based on-chip optical communications.

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.

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).