Graphene sensors: introduction and market status - Page 41

Researchers at MIT and Harvard University fabricated nanoscrolls made from graphene oxide flakes for water purification applications, at a much lower cost than that of graphene membranes. The team was able to control the dimensions of each nanoscroll, using both low- and high-frequency ultrasonic techniques.

The researchers say that these nanoscrolls could also be used as ultralight chemical sensors, drug delivery vehicles, and hydrogen storage platforms, in addition to water filters. Also, the ability to tune the dimensions of these architectures may open a window to industry, in combination with the more affordable production costs.

A group of scientists from NPL, Chalmers University of Technology and the US Naval Research Laboratory have used a novel technique to examine the effects of ambient air on graphene in a controlled environment, in order to characterize its response. As graphene is sensitive to a wide variety of chemicals, it is vital for graphene-based sensors to differentiate between the changes that are caused by the target gas and those caused by the natural environment.

The researchers investigated the effects of nitrogen, oxygen, water vapor and nitrogen dioxide (in concentrations typically present in ambient air) on epitaxial graphene inside a controlled environmental chamber. All measurements were taken at NPL by applying Kelvin probe force microscopy whilst simultaneously performing transport (resistance) measurements. This novel combination gave researchers the unique ability to connect the local and global electronic properties together, a task that has proven to be difficult in the past.

Researchers at the Korean Institute for Basic Science (IBS) have developed a wearable graphene-based biomedical device capable of sweat-based glucose monitoring and controlling. The diabetes patch comprises of an electronic chemical sensor that measures glucose levels using human sweat and microneedles that automatically inject medication, posing a real breakthrough for the treatment of diabetes, and possibly other chronic diseases as it will be able to remove the pain and inconvenience that traditional methods inflict.

The researchers improved the device’s detecting capabilities by integrating electrochemically active and soft functional materials on the hybrid of gold-doped graphene and a serpentine-shape gold mesh. The device’s pH and temperature monitoring functions enable systematic corrections of sweat glucose measurements as the enzyme-based glucose sensor is affected by pH (blood acidity levels) and temperature. The connection of the device to a portable power supply and data transmission unit enables the point-of-care treatment of diabetes. The drug (metformin) system consists of microneedles, a temperature sensor and a heater.

Researchers at the University of Cambridge, in collaboration with Cambridge-based technology company Novalia, developed a method that allows graphene and other electrically conducting materials to be added to conventional water-based inks and printed using typical commercial equipment.

The method works by suspending tiny particles of graphene in a ‘carrier’ solvent mixture, which is added to conductive water-based ink formulations. The ratio of the ingredients can be adjusted to control the liquid’s properties, allowing the carrier solvent to be easily mixed into a conventional conductive water-based ink to significantly reduce the resistance. The same method works for materials other than graphene, including metallic, semiconducting and insulating nanoparticles.

The Graphene Pavilion at the 2016 MWC included the ICFO's (Institute of Photonic Sciences in Barcelona, Spain) exciting stand, that showcased and demonstrated graphene-based technologies like a flexible and transparent light sensor and a fitness wearable.

Prof. Frank Koppens, Group Leader at the ICFO, stated that: "The sensors and wearables are working very well but we don’t have yet a plan to make a large number. Once a company decides to invest, this can rapidly change. So anything between 2 and 5 years is foreseeable."

The graphene keynote speech in the MWC 2016 included Nokia's Head of Business Line, Tapani Ryhanen's talk on graphene activity in Nokia.

It was a fascinating segment that shed light on the company's graphene-related activities, some of which (as can be seen in the image above) are energy storage applications, sensors, various electronic devices, photonics, optoelectronics and even graphene manufacturing - which shows that the company is really aiming at completing a full circle of graphene use.

Project GRASS aims to achieve on-the-field design, development, testing and validating of an innovative prototype of Graphene-Related Node for a Wireless Sensors Network, to be used as autonomous systems for Environmental Monitoring in different areas. The sensor is based on graphene that makes it very energy efficient, which is a major advantage in such components that need to be numerous and work continuously.

The project, along with all of its partners, are members of the Graphene Flagship, and at MWC 2016 we visited their stand and saw their graphene-based NO₂ sensor, that as opposed to conventional sensors (that require continuous heating), needs no heating but does require UV light.

The University of Michigan is currently developing a camera able to record 3D images and video, in a $1.2 million project funded the W.M. Keck Foundation. The camera will have graphene-based light detectors, and should be smaller than other existing models - as well as achieve higher resolutions.

Light that hits camera detectors can come from different directions, which translates into spatial information that can be used to reconstruct 3D images; Normally, that information is lost because the detector only measures intensity, which is also the reason that 3D images made with traditional recording methods must be constructed from multiple shots. Existing one-shot 3D cameras rely on a micro-lens array to divert the light after it has been focused by the main lens. This array of smaller lenses recovers the directional information from the rays of light, and then the camera's software reconstructs the image along with the depth information.

Researchers at Plymouth University, Cambridge and Tohoku (Japan) Universities and Nokia Technologies have found that electrical signals transmitted at high frequencies through graphene do not lose energy. In fact, the study showed that graphene out-performs any other known material, including superconductors, when carrying high-frequency electrical signals compared to direct current.

This finding may result in wide-ranging technology developments like next generation high-speed transistors, amplifiers, mobile phones, satellite communications and ultra-sensitive biological sensors.

Last week Barcelona hosted the Mobile World Congress trade show, and it was a very large and impressive conference - with over 100,000 visitors and thousands of exhibiting companies. This year the MWC included a graphene pavilion, organized by the ICFO and the Graphene Flagship, Europe's $1 billion research project initiative.

The Graphene Pavilion was very impressive, with several companies showcasing real graphene products and prototype devices, and also several research groups from leading Universities. The Pavilion consisted of 11 companies and 9 research centers - and you could see graphene materials, graphene supercapacitors (From Zap&Go, soon to hit the market), large graphene EMI shielding films (from GNext), graphene sensors and graphene-based RFID tags and antennas. In the photo below you can see an air quality prototype sensor made from graphene developed by Libre SRL (PiAndBi).