Tag Archives: graphene

Researchers Develop Transparent Flexible Terahertz Sensors With Graphene

The researchers of the Swedish Chalmers University of Technology have developed a new design of terahertz sensor using Graphene. This flexible sensor can be integrated into wearable materials. Most importantly, it can be manufactured very cheaply and also it is practically transparent. This new type of sensor could be a major breakthrough by opening doors of many new applications.

Flexible Graphene sensor by Chalmers University
Flexible Graphene sensor by Chalmers University

The terahertz frequency band ranges from 100 to 10,000 GHz. Terahertz radiation is able to penetrate materials that block visible and mid-infrared light. This technology opened up a range of potential applications in medical diagnostics, process control, and even intelligent vehicles. Jan Stake, the head of the Terahertz and Millimetre Wave Laboratory at Chalmers, said,

Terahertz graphene-based FET detectors have been demonstrated on rigid substrates such as SiO2/Silicon, and flexible devices such as graphene and other concepts have been demonstrated at RF/microwave frequencies.

This band is also used by the so-called “nude-scanners” used at airport check-in desks to look for illegal items carried by passengers. THz waves penetrate normal clothing hence it can detect weapons made of plastic. As Non-metallic weapons cannot be detected by ordinary metal detectors used at the entry gates and by hand-held scanners. Thus these new inexpensive sensors can enhance security for everyone.

Terahertz transmissions have enormous bandwidth available. THz signals can be used as carriers for high-speed information links over short distances allowing data speeds up to 100 Gb/s. On the other hand, THz waves allow uninterrupted visibility in fog or rain for motorized vehicles.

There are many medical applications of the technology using sensors that are cheap to produce and are physically small. One important example is in the field of dermatology. Skin regions affected by cancer have a different reflective index to THz waves which makes the sensor a useful diagnostic tool.

Although being under development for a long time, conventional THz sensors were always large and expensive. With this new design, the Swedish research team has enabled the tech world with mass production of the sensors. New sensors will be small, flexible and cost-effective. Development of the sensors was funded by the European Union under the Graphene Flagship Initiative.

What the Chalmers team has done to combine flexibility and terahertz detection could also make it possible to build an Internet of Things connected via high-bandwidth 5G technologies.

Pressure Sensor of the Future, Today

Flexible and transparent pressure sensor

Pressure sensors are used today in many fields, such as automotive industry, touch screen devices, aviation and biomedical instrumentation, many of these applications require precise and accurate measures. Many times, this can not be achieved because of the limitations of the sensors such as the inability to measure on round surfaces (if they are twisted or wrinkled). To solve this problem a transparent and bendable nanofiber sensor was developed.

The sensor contains organic transistors and electronic switches which are made from carbon and oxygen based materials, this makes the sensor capable of bending over a radius of 80 millimeters, measuring in 144 locations simultaneously. It is only around 8 micrometers thick, and it’s not sensitive to distortion.

Additionally, the pressure sensor is transparent and small, so it can be incorporated in wearables and implants. Wearables have been developed to shorten hospitals visits, to keep track of chronic diseases and for older citizens who do not want to live in assisted living facilities. Wearable technologies are capable of sensing different parameters of various diseases and transfer the data to a health center or directly to the patient, so they can take actions regarding their health. This technology improves the life quality of many patients, and can stay on for really long periods of time. Also, the main objective of wearables is to go unnoticed by both the patient and other people which is why the developed pressure sensor needs to be capable of bending, and adapting to a person´s constant moves.

Many applications have arisen from this project. For example, this device could allow breast tumor detection avoiding uncomfortable mammographs, and invasive biopsies. Also, it can be used to detect pressure and speed of blood allowing easy and superficial examination and diagnosis. Woman could now be cancer tested from home, and people who suffer from cardiac or blood pressure diseases could now be monitored away from the hospital.

The flexible nanofiber was created by combining carbon nanotubes, graphene and elastic polymers which makes the sensor really accurate even when stretched and deformed. Many companies are developing sensors with the same capabilities, but this is the first one which is not sensitive to distortion. Even though the researchers are only looking toward improving biomedical industry, the applications for this pressure sensor could be expanded to many industries. There is still a long way to go to achieve this objective, but this sensor is the first step, and health industry its a great place to start.

[Source]

A New Material For Unbreakable Smart Devices

Most of smartphones parts are made of silicons and other compounds, which are expensive and easily-breakable. This problem is making all of smart devices manufacturers looking for stronger and cheaper solutions.

By combining a set of materials, a group of researchers have successfully discovered a new material which could finally finish the disaster of cracked smartphone and tablet screens. The research group is led by a Queen’s University’s School of Mathematics and Physics researchers, with scientists from Stanford University, University of California, California State University and the National Institute for Materials Science in Japan.

Alongside conducting electricity at novel speeds, the new material is light, durable, and can be easily produced in large conventional semiconductor plants. It is a combination of  C60 fullerenes with layered materials such as graphene and h-BN (boron nitride), which presents a unique material with special properties that will be particularly relevant for use in smart device manufacturing.

This material composition has properties that are not naturally found in other materials. The hBN provides stability, electronic compatibility and isolation charge to graphene, while C60 can transform sunlight into electricity. The combining process is known as “der Waals solids” that allows compounds to be brought together and assembled in a pre-defined way.

The material also could mean that devices use less energy than before because of the device architecture so could have improved battery life and less electric shocks. This cutting-edge research is timely and a hot-topic involving key players in the field, which opens a clear international pathway to put Queen’s on the road-map of further outstanding investigations.
~ Dr Elton Santos, leader of the research group

The research shows that the material has the same properties as silicon, but higher chemical stability, lower weight and greater flexibility. These features would make the screens made of this material more difficult to break.

There is still one problem needs a solution. The graphene and the new material architecture is lacking a ‘band gap’, which is an important property to make active semiconductor devices. The team is planning to solve this using transition metal dichalcogenides (TMDs) which are chemically highly stable and have bandgaps like silicon.

According to the research group, this findings will pave the way for further exploration of new materials in the future. You can find more details about this by reviewing the research paper, which was published in the scientific journal ACS Nano, and by reading the official announcement.

Supercapacitors Surpassing Conventional Batteries

Researchers at the University of Central Florida have been looking for alternatives for lithium rechargeable batteries which are largely used in every device.

Using two-dimensional (2D) transition-metal dichalcogenides (TMDs) capacitive materials, they are building a new supercapacitor that overcomes the performance of conventional lithium battery and replaces its efficiently.

Transition metal dichalcogenide monolayers (TMDs) are atomically thin semiconductors of the type MX₂, with M a transition metal atom and X a chalcogen atom. One layer of M atoms is sandwiched between two layers of X atoms.

TMDs are considered as promising capacitive materials for supercapacitor devices since they provide a suitable current conduction path and a robust large surface to increase the structure’s high energy and power density.

Researchers have developed “high-performance core/shell nanowire supercapacitors based on an array of one-dimensional (1D) nanowires seamlessly integrated with conformal 2D TMD layers. The 1D and 2D supercapacitor components possess “one-body” geometry with atomically sharp and structurally robust core/shell interfaces, as they were spontaneously converted from identical metal current collectors via sequential oxidation/sulfurization” according to the research paper.

The new prototype is said to be charged 30,000 times without any draining, 20 times the lifetime of an ordinary battery.

“You could charge your mobile phone in a few seconds and you wouldn’t need to charge it again for over a week,” says UCF postdoctoral associate Nitin Choudhary.

This research was published in the NANO science journal, you can check the scientific paper here.

A Laser Treatment To Improve Paper Electronics

NanoEngineers” research group at Iowa University have been devoting efforts to use graphene and its amazing properties in their sensors and other technologies. Graphene has many extraordinary properties. It is about 100 times stronger than the strongest steel. It conducts heat and electricity efficiently and is nearly transparent.

Inspired by some recent projects about using inkjet printers to print multi-layer graphene circuits and electrodes, “NanoEngineers” have been working to move this research further by using the technology for a larger scale flexible, wearable and low-cost electronics. But there was some hurdles in improving the graphene conductivity after being printed and this process may damage the printing surface, such as papers, because of the high temperature or the use of chemicals.

Eventually, these engineers have led development of a laser-treatment process that allows them to use and improve printed graphene for electronic circuits and electrodes, even on paper and other fragile surfaces. The technology is said to show tremendous promise for a wide variety of fields including wearable sensors and thin film transistors with the ability of large-scale manufacturing.

It’s a three step process:

  • Graphene ink formulation: single layer graphene (SLG) powders were mixed with solvents and binders, bath sonicated, probe sonicated, and syringe filtered in order to produce a jettable graphene ink.
  • Inkjet Printing: The resultant graphene ink was syringed into the printer cartridge of a Dimatix Materials Printer and ejected via a piezoelectric nozzle in the subsequent printing process.
  • Laser Annealing:  A pulsed-laser processing of the electrodes using a Nd:Yag laser.
 Formulation, Printing, and Treatment, Source: <a href="http://pubs.rsc.org/en/Content/ArticleLanding/2016/NR/C6NR04310K#!divAbstract">Original Paper</a>
Formulation, Printing, and Treatment, Source: Original Paper

The engineers were able to remove ink binders and reduce graphene oxide by developing a computer-controlled laser technology that selectively irradiates inkjet-printed graphene oxide, Transforming the inkjet-printed graphene into a conductive material capable of being used in new applications is a huge breakthrough in nanotechnology.

More details are available at this paper on NanoScale journal.

Via:  ScienceDaily

Berkeley Lab makes graphene-MoS2 transistor

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U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has developed a way to assemble transistors based on the 2D materials graphene and molybdenum disulfide. By Peter Clarke @ edn-europe.com

The method etches narrow channels in conducting graphene laid down on a silicon-dioxide substrate. These channels are then filled with a transition-metal dichalcogenide, or TMDC, or more specifically MoS2. Both of these materials have a 2D structure that is just one atomic layer thick. The synthesis method was able to cover an area a few centimeters long by a few a millimeters wide opening up the possibility of commercial-scale production in a wafer fab on a silicon wafer.

Graphene Patterned at Room Temp

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by R. Colin Johnson @ eetimes.com

LAKE WALES Fla.—Graphene is easily grown with chemical vapor deposition (CVD) on copper foil, but a simple way of etching out the necessary circuit patterns and transferring them to a non-metallic substrate has eluded engineers. Now researchers at the University of Illinois (Urbana-Champaign) claim to have a one-step room temperature process for quickly patterning and transferring graphene circuits to flexible substrates using a simple shadow mask.

Graphene Patterned at Room Temp – [Link]

Supercapacitors to replace batteries?

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by Martin Cooke @ elektormagazine.com:

It was reported last year that researchers at Rice University in the US, led by chemist James Tour had developed a method of producing a form of graphene on commercial polyimide plastic sheet by zapping it with a laser. The process is called LIG (Laser Induced Graphene). The resulting graphene layer is not a conventional flat sheet made up of hexagonally-organized atoms but instead a spongy array of graphene flakes attached to the polyamide, giving a greatly increased surface area. This property can be exploited to build supercapacitors.

Supercapacitors to replace batteries? – [Link]