Graphene sensors: introduction and market status - Page 43

Scientists from UCLA’s California NanoSystems Institute have designed an effective way to use graphene in order to place molecules specific patterns within tiny nanoelectronic devices, which could be useful in creating sensors that are even small enough to record brain signals.

This is done by using a sheet of graphene with minuscule holes in it that is then placed on a gold substrate. The holes allow molecules to attach to the gold exactly where the scientists want them, creating patterns that control the physical shape and electronic properties of devices that are 10,000 times smaller than the width of a human hair.

Researchers at the University of Manchester have demonstrated how graphene's conductivity and flexibility will prove crucial to wearable electronic applications, opening the door to battery-free healthcare and fitness monitoring, phones, internet-ready devices and chargers to be incorporated into clothing and ‘smart skin’ applications (printed graphene-based sensors integrated with other 2D materials and put onto a patient’s skin to monitor temperature, strain and moisture levels).

The researchers printed graphene to create transmission lines and antennae and experimented with these in communication devices. They used a mannequin to which they attached graphene-enabled antennae on each arm, and found that the devices were able to communicate with each other, effectively creating an on-body communications system. These results show that such graphene-based components have the required quality and functionality for wireless wearable devices.

Scientists at the Moscow Institute of Physics and Technology (MIPT) are working on creating graphene-based hypersensitive sensors for precise analyses and pre-clinical drug research. While using bio-sensor chips to gather information on the effectiveness and toxicity of future medicine is not a new concept, the researchers in this study have managed to significantly improve the technology.

The researchers substituted the connecting layers in existing chips with a thin film made of graphene plates, which helps increase the precision of the analysis of biochemical reactions almost threefold. It is expected that in some cases the improvement might be 10 or even 100-fold. Substances react to graphene even in minimal concentration, while with hydrogel and sulfur-containing molecules no reaction would be expected. Scientists say that using this method will reduce the time needed for conducting analyses from days to minutes.

Researchers at the University of Illinois at Urbana-Champain are developing a portable graphene-based sensor that can rapidly and inexpensively determine whether an eye injury is mild or severe. The device is named OcuCheck and could aid in determining the extent of eye injuries at accident sites, in rural areas lacking ophthalmology specialists or on the battlefield. 

The sensor is designed to measure levels of ascorbic acid (vitamin C) in the fluids that coat or leak from the eye, which are found in low levels in the ocular tear film and in higher levels in the interior of the eye. The concept is that if severe damage occurs, the vitamin C leaks out in higher concentrations and can be detected. 

Researchers from Massachusetts Institute of Technology, Harvard, University of California Riveriside and US Army Research Laboratory have integrated graphene with silicon microelectromechanical systems (MEMS) to make a flexible, transparent, and low-cost device for the mid-infrared range. 

Tests showed it could be used to detect a person’s heat signature at room temperature (300 K or 27 degrees C/80 degrees F) without cryogenic cooling, which is normally required  to filter out background radiation, or noise, to create a reliable image (which complicates the design and adds to the cost and the unit’s bulkiness and rigidity).

An international team of researchers from six countries have designed a highly sensitive gas sensor made from boron-doped graphene, able to detect noxious gas molecules at extremely low concentrations, parts per billion in the case of nitrogen oxides and parts per million for ammonia. These sensors can be used for labs and industries that use ammonia, a highly corrosive health hazard, or to detect nitrogen oxides, a dangerous atmospheric pollutant emitted from automobile tailpipes. In addition to detecting toxic or flammable gases, theoretical work indicates that boron-doped graphene could lead to improved lithium-ion batteries and field-effect transistors. 

The sensor reaches a 27 times greater sensitivity to nitrogen oxides and 10,000 times greater sensitivity to ammonia compared to pristine graphene. The researchers believe these results will open a path to high-performance sensors that can detect trace amounts of many other molecules.

A team of researchers from the Indian Institute of Science (IISc) has developed a graphene oxides-based sensor that can detect nitrogen dioxide (NO2) in the atmosphere. The sensor can detect as little as a single NO2 molecule among millions of other molecules and it works even at room temperatures, unlike other common nitrogen sensors that are known to be high temperature devices.

For the development of this sensor, the team used fibre bragg grating, an optical fibre similar to the ones used for communication purposes. However, it can reflect one particular wavelength of light and transmit others. The IISc team covered the fibre bragg grating with an ultra thin layer of reduced graphene oxide and developed the sensor. by modifying the optical fibre, the scientists were able to use it in different applications like gas sensing and bio-sensing.

Researchers from the National University of Singapore (NUS) have developed a hybrid magnetic sensor that is reportedly more sensitive than most commercially available sensors. This could encourage the development of smaller and cheaper sensors for areas like consumer electronics, information and communication technology and automotive, as well as applications like thermal switches, hard drives and magnetic field sensors.

The sensor is made of graphene and boron nitride, and includes layers of carrier-moving channels, each of which can be controlled by the magnetic field. The researchers characterized the sensor by testing it at various temperatures, angles of magnetic field, and with a different pairing material. Graphene-based magnetoresistance sensors hold immense promise over existing sensors due to their stable performance over temperature variation and eliminating the necessity for expensive wafers or temperature correction circuitry. Production cost for graphene is also much lower than silicon and indium antimonide.

Haydale recently announced that its proprietary HDPlas technology has been used to create functionalized Graphene Nanoplatelets (GNPs) that have been incorporated into a functional graphene ink, which has been developed for screen printing. The ink has been created with area printing applications in mind.

A recent report details how a screen-printable functional graphene based ink, supplied by Goodfellow, performs better than many normal carbon-based ink, opening the door to innovative applications that require enhanced electrical conductivity, excellent adhesion on a range of substrates and high print resolution. Such applications are found in sensors, displays, printed electronics and electrodes.

An international team of scientists from Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the University of Maryland and more, have developed a graphene-based optical detector which reacts very rapidly to incident light of all different wavelengths and works at room temperature. It is reportedly the first time that a single detector has been able to monitor the spectral range from visible light to infrared radiation and right through to terahertz radiation.

The graphene detector is made of graphene on silicon carbide, along with a unique antenna. It is regarded as a comparatively simple and inexpensive construct that can cover the huge spectral range from visible light all the way to terahertz radiation, as graphene can pick up light with a very large range of photon energies and convert it into electric signals (unlike semiconductors like silicon or gallium arsenide). The broadband antenna and the right substrate were enough to supplement graphene and create the ideal conditions for this unique detector, that can be used for the exact synchronization of laser systems.