Graphene sensors: introduction and market status - Page 38

Researchers at the Daegu Gyeongbuk Institute of Science and Technology (DGIST) in South Korea and the University of Basel in Switzerland have developed a new graphene-based photodetector, that is regarded as the world's first graphene-based microwave photodetector. The sensor can reportedly detect 100,000 times less light energy than any existing graphene photodetector and may be useful in applications like wearable devices and flexible displays.

The teams studied the microwave absorption capabilities of bilayer graphene arranged into p-n junctions. Previous attempts to study the microwave range in photodetection met a considerable obstacle - the microwave on the detector itself had much smaller energy than the surface potential difference caused by the surrounding environment. This included residues on the surface of graphene that were left behind during its fabrication.

Researchers at the University of Cambridge in the UK and Jiangnan University in China have designed a low-cost, sustainable and environmentally-friendly method for making conductive cotton textiles using graphene-based ink. These fabrics could lead to smart textiles and interactive clothes that will find applications in healthcare, wearables, Internet of Things and more.

The team created inks of chemically modified graphene flakes that are more adhesive to cotton fibers than unmodified graphene. Heat treatment after depositing the ink on the fabric improves the conductivity of the modified graphene. The adhesion of the modified graphene to the cotton fiber is similar to the way cotton holds colored dyes and allows the fabric to remain conductive after several washes.

A couple of weeks ago we visited Haydale's headquarters and production floor in Ammanford, Wales, UK. Here are our impressions following this visit, the meeting with Haydale's management and a visit to the production floor and processing rooms.

First of all, let's clear up a common misunderstanding: Haydale is not a graphene producer. It buys graphene materials (from several sources) and uses its proprietary plasma process to improve the materials, make them more uniform in quality and tailor them to specific requirements. Haydale then uses these materials to create intermediate materials - inks, coatings, composite materials (and masterbatches) and 3D filaments. Haydale is working with customers to take these materials and use them in various graphene-enhanced products.

Researchers from Fujitsu present a new novel graphene-enhanced gas sensor device. The graphene has been employed as gate electrode for an n-channel silicon transistor. The researchers report that the sensor exhibits sensitivities that are more than one order of magnitde better than conventional resistivity-based graphene gas sensors - easily detecting 7 ppb of No₂.

When the graphene gate is exposed and gas molecules adsorb on the graphene surface, the work function of graphene changes depending on the gas species and concentrations, thus changing the threshold of the silicon transistor. The work function of the graphene-gate can be controlled by intentionally depositing proper doping materials on graphene, changing the threshold by up to 620 mV without degrading the sub threshold properties.

Researchers at University of California, Irvine (UCI), along with collaborators at Harvard University and the University of Pennsylvania, have created a graphene-based electronic method of monitoring changes in the cell's mitochondria that could indicate the start of the cell's self-annihilation process that may open the door to new ways of treating and destroying cancer cells.

The mitochondria, known as the cells' power plants, metabolize energy from carbohydrates and fats to create energy that the cells can use and store it as voltage across their surfaces. Their secondary role, however, is regulating a cell's life-death pathway. The researchers attached about 10,000 purified mitochondria, separated from their cells, to a graphene sensor via antibodies capable of recognizing a protein in their outer membranes. The graphene's qualities allowed it to function as a dual-mode sensor; its electrical sensitivity let researchers gauge fluctuations in the acidity levels surrounding the mitochondria, while its optical transparency enabled the use of fluorescent dyes for the staining and visualization of voltage across the inner mitochondrial membranes.

Graphenea, the Spain-based graphene producer, has teamed up with scientists from the Delft University of Technology in the Netherlands to design graphene-based "mechanical pixels" that could, among other applications, be someday used as colored pixels in e-readers and other low-powered screens.

In these "graphene balloons", a double layer of graphene (two atoms thick) is deposited on top of circular indents cut into silicon. The graphene membranes enclose air inside the cavities, and the position of the membranes can be changed by applying a pressure difference between the inside and the outside. When the membranes are closer to the silicon they appear blue; when the membranes are pushed away they appear red.

Researchers from India's VIT University demonstrated the successful modification of thermoplastics with graphene nano-platelets (GNPs). The researchers present a study on the voltage and current phase uniformity as a function of temperature.

The researchers say that the investigation shows that the resulting reinforced thermoplastic material is promising for the development of thermal sensor for aerospace, automobile and health applications.

Graphene 3D Lab, a leader in the development, manufacturing and marketing of proprietary composites and coatings based on graphene and other advanced materials, recently announced the release of a new product. The Company will now offer a filament for 3D printing that is both highly electrically conductive and flexible.

G3L reports that the enhanced properties of this product make it ideal for applications involving flexible sensors, electromagnetic/radiofrequency shielding, flexible conductive traces and electrodes to be used in wearable electronics. This new material will be available for purchase in 1.75mm diameter 100 gram spools at the Company's on-line store, www.blackmagic3D.com, under the trade name of "Conductive Flexible TPU Filament".

Scientists from Seoul National University have developed a graphene-enhanced bio-electric tongue that can successfully identify two taste sensations, sweet and savory. The tongue is reportedly 10-thousand times more effective in sensing "sweet" flavors compared to the human tongue, which means it can potentially be used to develop new food products.

To make the tongue, the researchers first extracted DNA information from protein-based taste-receptors that specifically sense sweet and savory flavors. This DNA information is inserted to a separate cell, which is put on top of a surface of graphene. The graphene detects changes in the current, and produces an electric signal which shows that a taste has been received.

Saint Jean Carbon, a carbon science company engaged in the exploration of natural graphite properties and related carbon products, has teamed up with the University of Western Ontario to create graphene that has a magnetic field (Magnetoresistance).

One of the involved researchers explained that: "Magnetoresistance (MR) refers to the significant change of electrical resistance of materials under a magnetic field. Magnetoresistance effects have been applied in magnetic sensors, spintronic devices and data storage. Magnetic sensors are extremely useful for today's industry for measurement and control purposes... This happens by detecting changes in electrical resistance brought on by the presence of a magnetic field. This is also known as magnetoresistance (MR). The market size of the magnetic sensor is increasing with annual growth rate at 10% because of new nanomaterials..."