Graphene sensors: introduction and market status - Page 46

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.

Graphenea recently introduced large area monolayer graphene suspended over microcavities as a standard catalog product, that can be used for NEMS (Nanoelectromechanical systems) due to its reliance on small vibrating membranes, which are sensitive to tiny forces.

Image courtesy of Stefan Wagner / Max Lemme, University of Siegen

NEMS are entering mainstream technology through sensors and actuators in platforms as common as inkjet printers, accelerometers, displays, and optical switches. The membranes used in NEMS need to be lightweight and stiff, with a high Young's modulus. As such, graphene is a very promising candidate for applications that require ultrathin membranes with excellent mechanical properties.

Researchers from Trinity College in Ireland, Montreal McGill University in Canada and the Université Grenoble Alpes in France have designed a graphene-based biosensor that can detect cholera toxins. It provides a reading in minutes, as opposed to current detection methods that may take hours.

The researchers explain that this biosensor could be modified to detect various other toxins like malaria and TB. They used graphene layers that cling tightly to the sensor's surface, but also hold the biological indicator that can read the presence of the cholera toxin. The graphene also delivered an unexpected effect - it boosted the sensor signal to give a two-fold increase on the response which made it much easier to get a reading. Graphene’s ability to boost sensors' signals also means that a smaller sample is required from the patient for detection, for example a pin-prick drop of blood, compared to a vial.

Nokia recently issued a patent for a graphene oxide-based sensor for protection of mobile devices against water damages. The sensor will use a graphene oxide sensing film senses moisture content or change in relative humidity and triggers an ultra-fast disconnection of the mobile device from its power source (battery).

The sensor will include a sensor capable of sensing water in liquid or vapor form based on the measurement of large time derivative values. The sensor will comprise of a graphene oxide thin film and two or more electrodes in contact with the thin film. An electronic switch will be connected to the sensor and to a power source that powers the circuitry in the electronic device. The GO can be easily integrated into the sensor as a thin film by printing it on the power source's surface.The film should be less than 100 nanometers thick and could also be spray-coated or spin-coated onto the surface.

Researchers at the German RWTH University and AMO GmbH Aachen fabricated highly sensitive Hall Effect sensors using single layer graphene. Graphene's very high carrier mobility at room temperature and very low carrier densities make it a material that can outperform all currently existing Hall sensor technologies.

The researchers protected the graphene from ambient contamination by encapsulating it with hexagonal boron nitride layers. The consequently fabricated devices showed a voltage and current normalized sensitivity of up to 3 V/VT and 5700 V/AT, respectively. These values are more than one order of magnitude above the values achieved in Silicon-based devices and a factor of two above the values achieved with the best III/V semiconductors Hall sensors in ambient conditions. In addition, these results are far better than the earlier reported graphene Hall sensors on Silicon oxide and Silicon carbide substrates.

The Canadian Graphene Sensors Inc. and India-based Meditel Technologies will form a new Joint Venture called Single Member LLC. Meditel will invest $36 million in Single Member and will hold 70% of the new company.

Single Member will likely commercialize Graphene Sensors' graphene-based sensor technology, and indeed it will be granted a leasing license for the GS7 biosensor technology (used for the early detection of potentially cancerous cells).

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 Lawrence Livermore National Laboratory created graphene aerogel microlattices with an engineered architecture using a 3D printing technique known as direct ink writing. These lightweight aerogels have high surface area, excellent electrical conductivity, mechanical stiffness and exhibit supercompressibility (up to 90% compressive strain). In addition, the researchers claim that these 3D printed graphene aerogel microlattices show great improvement over bulk graphene materials and much better mass transport.

A common problem in creating bulk graphene aerogels is the occurrence of a largely random pore structure, thus excluding the ability to tailor transport and additional mechanical properties of the material for specific applications such as batteries and sensors. Making graphene aerogels with engineered architectures is greatly assisted by 3D printing, which allows to design the pore structure of the aerogel, permitting control over many properties. This development, as per the scientists, could open up the design space for using aerogels in novel and creative applications.

The Ulsan National Institute of Science and Technology has developed a transparent hybrid electronic device production technique for the manufacturing of wireless smart sensors. The is based on a combination of graphene and metal nanowires and the team says it maintains its electrical characteristics even when folded or pulled.

The smart sensor that is based on the device can be attached to various surfaces, even the human skin, for real-time monitoring of changes in biomaterials (like various proteins). The sensor wirelessly transmits the changes in biomaterials using its built-in antenna and maintains excellent flexibility even after long exposure to air and heat. The power required for the transmission and reception is supplied by its transmission antenna, and thus no battery is required.

Researchers from the ICFO, ICREA, MIT and UC Riverside, have now showed that a graphene-based photodetector converts absorbed light into an electrical voltage at an extremely high speed. The efficient conversion of light into electricity is crucial to various technologies, from cameras to solar cells. It can also play a part in data communication applications, since it allows information to be carried by light and converted into electrical information that can be processed in electrical circuits.

Graphene is known to be an excellent material for conversion of light to electrical signals, but it was unknown exactly how fast graphene responds to ultrashort flashes of light. The researchers developed a device capable of converting light into electricity in less than 50 femtoseconds (a twentieth of a millionth of a millionth of a second). Facilitated by graphene's nonlinear photo-thermoelectric response, the observation of femtosecond photodetection response times was enabled.