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Easy-to-make, ultra-low power electronics could charge out of thin air

Posted By Terrance Barkan, Wednesday, October 14, 2020
Researchers have developed a new approach to printed electronics which allows ultra-low power electronic devices that could recharge from ambient light or radiofrequency noise. The approach paves the way for low-cost printed electronics that could be seamlessly embedded in everyday objects and environments.

Electronics that consume tiny amounts of power are key for the development of the Internet of Things, in which everyday objects are connected to the internet. Many emerging technologies, from wearables to healthcare devices to smart homes and smart cities, need cost-effective transistors and electronic circuits that can function with minimal energy use.

Printed electronics are a simple and inexpensive way to manufacture electronics that could pave the way for low-cost electronic devices on unconventional substrates – such as clothes, plastic wrap or paper – and provide everyday objects with ‘intelligence’.

However, these devices need to operate with low energy and power consumption to be useful for real-world applications. Although printing techniques have advanced considerably, power consumption has remained a challenge – the different solutions available were too complex for commercial production.

Now, researchers from the University of Cambridge, working with collaborators from China and Saudi Arabia, have developed an approach for printed electronics that could be used to make low-cost devices that recharge out of thin air. Even the ambient radio signals that surround us would be enough to power them. Their results are published in the journal ACS Nano.

Since the commercial batteries which power many devices have limited lifetimes and negative environmental impacts, researchers are developing electronics that can operate autonomously with ultra-low levels of energy.

The technology developed by the researchers delivers high-performance electronic circuits based on thin-film transistors which are ‘ambipolar’ as they use only one semiconducting material to transport both negative and positive electric charges in their channels, in a region of operation called ‘deep subthreshold’ – a phrase that essentially means that the transistors are operated in a region that is conventionally regarded as their ‘off’ state. The team coined the phrase ‘deep-subthreshold ambipolar’ to refer to unprecedented ultra-low operating voltages and power consumption levels.

If electronic circuits made of these devices were to be powered by a standard AA battery, the researchers say it would be possible that they could run for millions of years uninterrupted.

The team, which included researchers from Soochow University, the Chinese Academy of Sciences, ShanghaiTech University, and King Abdullah University of Science and Technology (KAUST), used printed carbon nanotubes – ultra-thin cylinders of carbon – as an ambipolar semiconductor to achieve the result.

“Thanks to deep-subthreshold ambipolar approach, we created printed electronics that meet the power and voltage requirements of real-world applications, and opened up opportunities for remote sensing and ‘place-and-forget’ devices that can operate without batteries for their entire lifetime,” said co-lead author Luigi Occhipinti from Cambridge’s Department of Engineering. “Crucially, our ultra-low-power printed electronics are simple and cost-effective to manufacture and overcome long-standing hurdles in the field.”

“Our approach to printed electronics could be scaled up to make inexpensive battery-less devices that could harvest energy from the environment, such as sunlight or omnipresent ambient electromagnetic waves, like those created by our mobile phones and wifi stations,” said co-lead author Professor Vincenzo Pecunia from Soochow University. Pecunia is a former PhD student and postdoctoral researcher at Cambridge’s Cavendish Laboratory.

The work paves the way for a new generation of self-powered electronics for biomedical applications, smart homes, infrastructure monitoring, and the exponentially-growing Internet of Things device ecosystem.The research was funded in part by the Engineering and Physical Sciences Research Council (EPSRC).

Tags:  carbon nanotubes  Chinese Academy of Sciences  Energy  Engineering and Physical Sciences Research Council  Graphene  King Abdullah University of Science and Technology  Luigi Occhipinti  Medical  ShanghaiTech University  Soochow University  transistor  University of Cambridge  Vincenzo Pecunia 

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The perfect angle for e-skin energy storage

Posted By Terrance Barkan, Wednesday, October 14, 2020
Researchers at DGIST have found an inexpensive way to fabricate tiny energy storage devices that can effectively power flexible and wearable skin sensors along with other electronic devices, paving the way towards remote medical monitoring & diagnoses and wearable devices.

Their findings were published in the journal Nano Energy (Nano Energy, "Extremely flexible and mechanically durable planar supercapacitors: High energy density and low-cost power source for E-skin electronics").

Materials scientists Sungwon Lee and Koteeswara Reddy Nandanapalli at the Daegu Gyeongbuk Institute of Science & Technology (DGIST) developed the fabrication process with colleagues in Korea. A key for success is spraying a specific amount of graphene ink onto flexible substrates at a specific angle and temperature.

Lee says “Demand for remote diagnosis and wearable devices is rapidly increasing and thus, many scientists are focusing their research efforts on developing various electronic skin devices, which requires extremely tiny and flexible energy devices as a power source.”

When micro-supercapacitors are charged, positive and negative electrical charges accumulate on their electrodes and stored as energy. These devices have short charging and discharging times compared to batteries, but they can’t store as much energy.

Graphene is a promising material for improving their energy storage, as graphene electrodes are highly porous and so provide a larger surface area for the necessary electrostatic reactions to occur.

Another way to improve micro-supercapacitor performance is by fabricating electrodes with interlocking teeth, like those of two combs, increasing the amount of energy that can be stored. But this process is expensive and doesn’t work on flexible, temperature-sensitive substrates.

The obvious solution would be to spraying of graphene onto a flexible substrate, but vertical spraying leads to electrodes that aren’t very porous and that have compact layers, giving them poor performance.

Lee, Nandanapalli, and their colleagues sprayed graphene ink onto thin, flexible substrates, fabricating a paper-thin micro-supercapacitor with interlocking electrodes and excellent performance.

The trick, they explored, was to spray ten millilitres of graphene ink at a 45° angle and 80°C temperature onto a flexible substrate. This led to the formation of porous, multi-layered electrodes. The team’s micro-supercapacitor is 23 micrometres thin, ten times thinner than paper, and retains its mechanical stability after 10,000 bends. It can store around 8.4 microfarads of charge per square centimeter (2 times higher than that of the value reported today) and has a power density of about 1.13 kilowatts per kilogram (4 times higher than that of the Li-ion batteries). The team demonstrated it could be used in wearable devices that adhere to the skin.

“Our work shows that it’s possible to reduce the thickness of micro-supercapacitors for use in flexible devices, without degrading their performance,” says Lee. The team next aims to improve the micro-supercapacitors’ storage capacity and energy consumption to make it feasible for use in real-world electronic skin devices.

Tags:  Daegu Gyeongbuk Institute of Science & Technology  Energy Storage  Graphene  Healthcare  Koteeswara Reddy Nandanapalli  Medical  Sensors  Sungwon Lee  supercapacitor  wearable 

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Caltech Researcher Unveils Sensor that Rapidly Detects COVID-19 Infection Status, Severity, and Immunity

Posted By Terrance Barkan, Monday, October 5, 2020
One feature of the COVID-19 virus that makes it so difficult to contain is that it can be easily spread to others by a person who has yet to show any signs of infection. The carrier of the virus might feel perfectly well and go about their daily business—taking the virus with them to work, to the home of a family member, or to public gatherings.

A crucial part of the global effort to stem the spread of the pandemic, therefore, is the development of tests that can rapidly identify infections in people who are not yet symptomatic.

Now, Caltech researchers have developed a new type of multiplexed test (a test that combines multiple kinds of data) with a low-cost sensor that may enable the at-home diagnosis of a COVID infection through rapid analysis of small volumes of saliva or blood, without the involvement of a medical professional, in less than 10 minutes.

The research was conducted in the lab of Wei Gao, assistant professor in the Andrew and Peggy Cherng department of medical engineering. Previously, Gao and his team have developed wireless sensors that can monitor conditions such as gout, as well as stress levels, through the detection of extremely low levels of specific compounds in blood, saliva, or sweat.

Gao's sensors are made of graphene, a sheet-like form of carbon. A plastic sheet etched with a laser generates a 3D graphene structure with tiny pores. Those pores create a large amount of surface area on the sensor, which makes it sensitive enough to detect, with high accuracy, compounds that are only present in very small amounts. In this sensor, the graphene structures are coupled with antibodies, immune system molecules that are sensitive to specific proteins, like those on the surface of a COVID virus, for example.

Previous versions of the sensor were impregnated with antibodies for the hormone cortisol, which is associated with stress, and uric acid, which at high concentrations causes gout. The new version of the sensor, which Gao has named SARS-CoV-2 RapidPlex, contains antibodies and proteins that allow it to detect the presence of the virus itself; antibodies created by the body to fight the virus; and chemical markers of inflammation, which indicate the severity of the COVID-19 infection.

"This is the only telemedicine platform I've seen that can give information about the infection in three types of data with a single sensor," Gao says. "In as little as a few minutes, we can simultaneously check these levels, so we get a full picture about the infection, including early infection, immunity, and severity."

Established COVID-testing technologies usually take hours or even days to produce results. Those technologies also require expensive, complicated equipment, whereas Gao's system is simple and compact.

So far, the device has been tested only in the lab with a small number of blood and saliva samples obtained for medical research purposes from individuals who have tested positive or negative for COVID-19. Though preliminary results indicate that the sensor is highly accurate, a larger-scale test with real-world patients rather than laboratory samples must be performed, Gao cautions, to definitively determine its accuracy.

With the pilot study now completed, Gao next plans to test how long the sensors last with regular use, and to begin testing them with hospitalized COVID-19 patients. Following in-hospital testing, he would like to study the suitability of the tests for in-home use. Following testing, the device will need to receive regulatory approval before it is available for widespread use at home.

"Our ultimate aim really is home use," he says. "In the following year, we plan to mail them to high-risk individuals for at-home testing. And in the future, this platform could be modified for other types of infectious disease testing at home."

The paper describing the research, titled, "SARS-CoV-2 RapidPlex: A Graphene-based Multiplexed Telemedicine Platform for Rapid and Low-Cost COVID-19 Diagnosis and Monitoring," has been published online and will appear in the December issue of the journal Matter. Co-authors are former postdoctoral scholar in medical engineering Rebeca M. Torrente-Rodríguez, medical engineering graduate students Heather Lukas, Jiaobing Tu (MS '20), Jihong Min (MS '19), Yiran Yang (MS '18), and Changhao Xu (MS '20); and Harry B. Rossiter of the Harbor-UCLA Medical Center.

Funding for the research was provided by the National Institutes of Health; the Tobacco-Related Disease Research Program, a California state agency focused on reducing tobacco use; the Merkin Institute for Translational Research; and the Translational Research Institute for Space Health.

Tags:  Caltech  COVID-19  Graphene  Healthcare  Medical  Sensors  Wei Gao 

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New rapid COVID-19 test taking off at EIA

Posted By Graphene Council, Friday, September 25, 2020
Edmonton International Airport has been chosen as the exclusive location to trial a new COVID-19 test that can produce results in seconds.

In partnership with GLC Medical (GLCM) Inc., a subsidiary of Graphene Leaders Canada (GLC) Inc., an Edmonton-based company, EIA will host clinical trials of this new technology that has the potential to have global implications for COVID-19 testing. This test is conducted with a handheld unit that takes a saliva sample from a person and is expected to tell if someone has COVID-19 in under 1-minute, compared to other tests with longer laboratory-based waiting periods for results. 

This test promises many advantages from its ease of use to the elimination of the nasal swab to direct virus detection. This kind of test will help address the need for a 14-day quarantine period in Canada and potentially other international quarantine restrictions. By removing or reducing this barrier, it can help travellers feel safer in returning to travel.

GLC Medical (GLCM) Inc. is headquartered in the Edmonton Research Park and has garnered international attention for the development of this test, which is still undergoing clinical testing as part of the regulatory approval process with health authorities. As an airport, EIA understands working with governments and within a regulated structure. With secure and safe facilities and a consistent flow of passengers, it’s one reason an airport is an ideal place to start testing the trial phase of this new COVID-19 rapid test.

“We all want travel to get back to normal and a rapid COVID-19 test will accelerate this return while enhancing passenger confidence in the safety of our industry. While we have seen some growth in recent months, our passenger numbers during COVID-19 continue to remain low and a test like this is crucial to our future. All airlines, airports and the whole travel and hospitality sector are looking for this solution. If EIA can play a role in bringing new technology and science forward by partnering with experts like GLC that’s exactly what we’re going to do. This is an exciting opportunity for all of us.”

-Tom Ruth, CEO and President, Edmonton International Airport

“We are very excited to offer the world a graphene-enhanced rapid solution in COVID-19 virus detection. The opportunity to collaborate with EIA, a world-respected airport authority, to enable travel and to bring families back together is very rewarding for us. This graphene-enhanced rapid test demonstrates the power of graphene innovation to overcome the challenges of COVID-19. GLC is proud to be a part of EIA’s initiative in setting the global standard in safety and reliability for their travellers.”

-Donna Mandau, President & CEO, Graphene Leaders Canada (GLC) Inc. / GLC Medical (GLCM) Inc.

How the test works:

• The person being tested provides a saliva sample into the testing unit;
• The graphene surface inside the testing unit is designed to bond to the spike protein in the virus;
• This binding event changes the electronic characteristics of the graphene, and this measurable change is what is used to determine if a person is infected or not;
• The device will show a red or green light in under 1-minute to indicate if a person is virus free or not;
• The test is not required to be administered by a medical professional and with training can be
administered by anyone, similar to how basic first aid training is done.

The next step is to bring this test and GLC to EIA and establish a safe and secure test site. Details about the testing and the process will be shared in the coming weeks. A start date has not been determined, but once it begins, the clinical trial will last several weeks over this fall. This trial phase will help GLC Medical secure regulatory approval and certification for its test from Health Canada and other regulatory bodies, including in the United States and other areas of the world.

As a not-for-profit corporation, EIA works to attract investment and jobs to the Edmonton Metro Region and support local innovation. Airports connect global communities and create opportunities for people and business. The partnership with GLC Medical has tremendous opportunities to impact many industries beyond just the travel industry. EIA is focused on safety and security as its number one core value and creating a safe passenger experience at the airport is a priority. 

The EIA Ready program focuses not only on enhanced cleaning but also seeking out and adopting new innovations and technologies to help passengers feel comfortable in the airport and with travel overall. The recent announcement of EIA being accredited by Airports Council International (ACI) with the airport health certification is yet another example of how EIA is putting safety and security as a top priority in creating a safe airport.

Tags:  COVID-19  Donna Mandau  Edmonton International  GLC Medical  Graphene  Graphene Leaders Canada  Healthcare  Medical  Tom Ruth 

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UV-resistant elastic for N95 masks receives NSF RAPID grant

Posted By Graphene Council, Wednesday, May 20, 2020
Northwestern University’s Mark Hersam has received funding to develop a new elastic material that could enable N95 medical face masks to be disinfected and reused dozens of times.

Last week, the project received a $200,000 rapid response research (RAPID) grant from the National Science Foundation, which has called for immediate proposals that have potential to address the spread of the novel coronavirus (COVID-19).

“The ongoing COVID-19 pandemic has led to a shortage of critical medical equipment, including N95 medical masks. To conserve resources, medical workers have been reusing masks,” said Hersam, a Walter P. Murphy Professor of Materials Science and Engineering in Northwestern’s McCormick School of Engineering. “The problem is that sterilization using ultraviolet light breaks down the elastic in the nose foam and head straps, preventing the masks from fitting properly.”

To disinfect equipment, including N95 masks, medical professionals use ultraviolet germicidal irradiation (UVGI). While the widely used technique is highly effective in killing or inactivating pathogens, such as viruses and bacteria, UVGI also rapidly ages plastics and rubber.

The outcomes of this research not only address the current COVID-19 crisis, but are applicable for general medical use, including in future pandemics.” Mark Hersam, materials scientist.

Hersam’s team is developing a new type of elastic composite based on hydrated graphene oxide (hGO), a material that shows resistance to ultraviolet radiation and has proven intrinsic antimicrobial properties. By incorporating this material into N95 masks, the elastic components could better withstand UVGI and continue to maintain a snug fit even after being reused dozens of time.

A world-renowned graphene expert, Hersam will lead proof-of-concept experiments in his laboratory throughout the summer. He believes that better materials for medical equipment will be important well into the future.

“The outcomes of this research not only address the current COVID-19 crisis,” he said, “but are applicable for general medical use, including in future pandemics.”

The project, “Hydrated graphene oxide elastomeric composites for sterilizable and reusable N95 masks,” is funded by NSF award number 2029058.

Tags:  Graphene  Healthcare  Mark Hersam  Medical  Northwestern University 

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Instantaneous reduction of graphene oxide using electric spark for wearable sensors

Posted By Graphene Council, Monday, May 4, 2020
Wearable electronic devices, worn on clothes or the skin to record body parameters such as heartbeat and pulse rate, are currently in great demand. 2D nanomaterials such as graphene, with their exceptional electrical and mechanical properties, play a key role in fabricating these devices. Graphene oxide (GO) is a scalable and low-cost alternative to pristine graphene. However, GO is an insulator and needs to be reduced to an electrically conducting form called reduced Graphene Oxide (rGO) to make it useful for sensors. 

A group of IISc researchers has now devised a novel method to instantaneously reduce graphene oxide using an electric spark.

This method, outlined in a paper published in ACS Applied Materials and Interfaces, is efficient and cost-effective, which would allow easy industrial scale-up. It is also more environment-friendly compared to existing methods as it does not generate chemical residues. Sensors developed using this method can have applications in gesture control, in biomedical rehabilitation to detect the degree and intensity of body movements, and in the field of robotics. 

Graphene and its derivatives are versatile in their electrical and structural properties, and are therefore the preferred materials used to build flexible sensors. The chemical structure of GO allows it to form ‘printable inks’ with various solvents, and bind to the substrate better. Various reduction techniques, including thermal, UV, laser, and microwave-based methods, are used to modify the chemical structure and form rGO. However, these methods are expensive and time-consuming, often produce toxic by-products, and can also damage the substrate.

To reduce graphene oxide efficiently and quickly, the IISc team used an electrical discharge under ambient conditions, popularly known as an electric spark. Sparking on GO deposited over a porous substrate enables its instantaneous reduction, along with a large drop in electrical resistance.

By varying certain parameters in the spark stream, the team was able to tweak the degree of reduction of graphene oxide, and also make predefined conducting patterns, which offers more flexibility in sensor fabrication. The heat present in the spark is highly localised and does not cause any substrate damage; this was verified using a Scanning Electron Microscope.

When mechanical stress is applied to the rGO-coated fabric, it causes a proportional change in the electrical resistance of the rGO film. This property is essential for it to function efficiently as a flex sensor. The change in electrical resistance was found to be consistent over repeated tests and under different bending angles, says Rajanna Konandur, Honorary Professor at the Department of Instrumentation and Applied Physics, and corresponding author of the paper.

He and his team integrated flex sensors containing these spark-reduced rGO films on commercially available gloves, and tested them using bending and other finger movements. Further research can pave the way for inexpensive, large-scale production of flexible, wearable electronics that use these films.

Tags:  2D materials  Graphene  Graphene Oxide  Indian Institute of Science Bengaluru  Medical  nanomaterials  Rajanna Konandur  Sensors 

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Synergistic Antiviral Activity of Graphene Oxide and Common Antiviral Agents

Posted By Graphene Council, Wednesday, March 4, 2020
Not only does loading antiviral agents on graphene oxide produce a synergistic antiviral effect, but it also enhances the biocompatibility and reduces the cytotoxicity of the drugs. Researchers have found that the antivirus nanomedicines designed based on GO which have been tested against a specific virus can also exert the same antiviral effect against a wider range of viruses from the Herpesviruses to the novel Coronavirus.

Due to their two-dimensional structure, sharp edges, and negatively charged surfaces, graphene oxide (GO) nanosheets are capable of interacting with microorganisms such as bacteria and viruses and destroying them by disrupting their plasma membrane or by generating reactive oxygen species to induce oxidative stress. Nevertheless, GO also interacts with living cells depending on its concentration; as the wise saying goes: “The only real difference between medicine and poison is the dose....and intent.”

On the other hand, there are a large number of substances whose antimicrobial properties have been proven over the years, among which are hypericin and curcumin; studies have shown that hypericin and its derivatives, which are extracted from Hypericum perforatum, have antiviral activity against a broad spectrum of viruses including the herpes simplex virus types 1 & 2, influenza virus, Sendai virus, chronic hepatitis C virus, etc.

Hence, now it is time to integrate what researchers have learned during all those years of research and experiment; GO’s high drug-loading capacity and low cytotoxicity make it the standout choice as a drug carrier; according to a recent study conducted by the researcher of Sichuan Agricultural University, loading an optimized dosage of hypericin on GO reduced its cytotoxicity while improving its antiviral activity both in vitro and in vivo. The resulting antiviral combination was tested against novel duck reovirus (NDRV) and reported to inhibit its replication by preventing the transcription of its target gene and suppressing the expression of its target protein in the early stage of the treatment. Moreover, in vivo tests indicated that hypericin-loaded GO could reduce pathological lesions of the ducklings infected with NDRV, thus increasing their chance of survival.

Similar antiviral and antibacterial effects have also been seen in curcumin, which is the most biologically active substance in Curcuma longa – also known as turmeric. In 2017, a group made up of American and Chinese researchers reported in their article – published in the Nanoscale journal – that loading curcumin on GO not only did improve the biocompatibility of GO but also reduced the cytotoxicity of both GO and curcumin. Their studies revealed that curcumin-loaded GO had synergistic antiviral activity against the respiratory syncytial virus, and inhibited its binding to host cells. This virus is recognized as the major viral pathogen of the lower respiratory tract in infants.

Apart from the curcumin itself, carbon quantum dots derived from curcumin have been proven effective against enterovirus 71 (EV71). In a new study carried out in Taiwan, core-shell quantum dots were synthesized from curcumin using a one‐step dry heating method, resulting in their surfaces preserving many of the moieties of polymeric curcumin, as if curcumin were loaded on the quantum dots. Figure 1 schematically illustrates the synthesis process and antiviral activity of these nanomaterials; accordingly, the mechanism behind their antiviral activity is inhibiting the EV71 virus from both attaching to the host cells, replicating, and exiting from the infected cells.

What is remarkable about all three of these studies is that loading antiviral agents on GO enhances its biocompatibility while reducing the cytotoxicity of both GO and the antiviral agents (e.g., curcumin and hypericin), in addition to the fact that the two substances combine synergistically to form a more effective therapeutic agent than each of those substances alone. Furthermore, researchers have found that the antivirus nanomedicines designed based on GO which have been tested against a specific virus can also exert the same antiviral effect against a wider range of viruses from the herpes virus to the novel Coronavirus.

Tags:  Graphene  Graphene Oxide  Healthcare  Medical  nanomaterials 

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CRIL wins EUR140,000 EU Graphene Flagship funding

Posted By Graphene Council, Wednesday, February 19, 2020
Frontier IP, a specialist in commercialising university intellectual property, today announces that portfolio company Cambridge Raman Imaging Limited  has been awarded €140,000 by the European Union's Graphene Flagship to accelerate development of its innovative graphene-enabled scanning Raman microscope.

The Company, a spin out from the University of Cambridge and the Politecnico di Milano in Italy, was incorporated in March 2018 to develop and commercialise the joint work of both universities to create graphene-based ultra-fast lasers. Frontier IP owns 33.3 per cent of the Company.

Cambridge Raman Imaging is initially developing a Raman-imaging scanning microscope to diagnose and track tumors, and for other detection applications.

The technology uses graphene to modulate ultra-short pulses of light that can be synchronised in time and are much lower cost than conventional systems.

The Company's scanning microscope will target real-time digital images of fresh tissue samples to detect and show the extent of tumours, their response to drug treatments and to allow surgeons to see if a cancer has been completely removed.

Existing histopathology technologies mean samples taken from a patient must be stained and sent to a laboratory for analysis, including during operations. Cambridge Raman Imaging's lasers will be compact enough to use in an operating theatre, speeding up progress. The global market size for tumour analysis and tracking has been estimated to be £9 billion a year, according to Grandview Research.

Potential future applications include endoscopic examination, scanning body fluids for pathogens or tumour cells, and imaging semiconductors or proteins.

The Graphene Flagship is one of the largest research initiatives ever funded by the EU, tasked with bringing together academic and industrial researchers to take graphene from academia and into society.

Paul Mantle, Cambridge Raman Imaging director, said: "This technology has the potential to revolutionise patient care by giving the clinician accurate information on tumour type and response to treatment."

Neil Crabb, chief executive officer of Frontier IP Group, said: "Cambridge Raman Imaging is our first spin out to develop a graphene-based technology. Although the first applications are in healthcare, we believe there could be broader applications in other industries. We're delighted the EU Graphene Flagship recognises the potential of the technology with the grant award to accelerate its development "

Tags:  CRIL  Frontier IP  Graphene  Graphene Flagship  Healthcare  Medical  Neil Crabb  Paul Mantle 

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A 3D camera for safer autonomy and advanced biomedical imaging

Posted By Graphene Council, The Graphene Council, Thursday, February 6, 2020
Researchers at the University of Michigan have proven the viability of a 3D camera that can provide high quality three-dimensional imaging while determining how far away objects are from the lens. This information is critical for 3D biological imaging, robotics, and autonomous driving.

Instead of using opaque photodetectors traditionally used in cameras, the proposed camera uses a stack of transparent photodetectors made from graphene to simultaneously capture and focus in on objects that are different distances from the camera lens.

The system works because of the unique traits of graphene, which is only one atomic layer thick and absorbs only about 2.3% of the light. A pair of graphene layers can be used to construct a photodetector that can efficiently detect light, even though less than 5% of the light is absorbed. When placed on a transparent substrate, instead of a silicon chip for example, the detectors can be stacked, with each one in a different focal plane.

As described by Prof. Ted Norris: “When you have a camera, you have to have a focusing adjustment on your lens so that when you’re focusing on a particular object like a person’s face, the rays of light that are coming from that person’s face are focused onto that single plane on your detector chip. Items in front or behind the object are out of focus.

But if it were possible to stack different detector arrays each in different focal planes, then they could each image accurately a different place in the object space simultaneously. What’s more, if you can detect multiple focal planes of data all at the same time, you can use algorithms to reconstruct the object in three dimensions. That is called a light field image. We have demonstrated how to use transparent focal stacks to do light field image and image reconstruction.”

In addition to basic object identification, the current paper shows how their device can detect how far away something is – making it suitable for applications in autonomous driving and robotics. It is also ideal for biological imaging in cases where it is important to image three-dimensional volume.

For its ultimate success, the project required complementary expertise in three areas. Prof. Zhaohui Zhong’s team developed the graphene devices; Norris’ group worked on the design features of the optical instrument and demonstrated the devices in the lab; and Prof. Jeff Fessler’s group, which developed the image reconstruction algorithm.

Fessler echoed the other faculty in stating the group of nine researchers consisting of faculty, postdocs and students “coalesced as a great team, all learning from each other and contributing different aspects of the final paper.”

Inspiration for the camera came from previous research of Zhong and Norris on highly sensitive graphene photo detectors, published in Nature Nanotechnology in 2014.

The current transparent graphene sensors fabricated so far are too low-resolution to depict images, but the initial experiments showed that the lens focused light from a different distance on each of the two sensors. Work is continuing on the project.

Tags:  biological imaging  Graphene  Medical  Robotics  Sensors  Ted Norris  University of Michigan 

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New graphene amplifier has been able to unlock hidden frequencies in the electromagnetic spectrum

Posted By Graphene Council, The Graphene Council, Thursday, February 6, 2020
Researchers have created a unique device which will unlock the elusive terahertz wavelengths and make revolutionary new technologies possible.

Terahertz waves (THz) sit between microwaves and infrared in the light frequency spectrum, but due to their low-energy scientists have been unable to harness their potential. The conundrum is known in scientific circles as the terahertz gap.

Being able to detect and amplify THz waves (T-rays) would open up a new era of medical, communications, satellite, cosmological and other technologies.

One of the biggest applications would be as a safe, non-destructive alternative to X-rays. However, until now, the wavelengths – which range between 3mm and 30μm – have proved impossible to utilise due to relatively weak signals from all existing sources.

A team of physicists has created a new type of optical transistor – a working THz amplifier – using graphene and a high-temperature superconductor.

The physics behind the simple amplifier replies on the properties of graphene, which is transparent and is not sensitive to light and whose electrons have no mass. It is made up of two layers of graphene and a superconductor, which trap the graphene massless electrons between them, like a sandwich.

The device is then connected to a power source. When the THz radiation hits the graphene outer layer, the trapped particles inside attach themselves to the outgoing waves giving them more power and energy than they arrived with – amplifying them.

Professor Fedor Kusmartsev, of Loughborough’s Department of Physics, said: “The device has a very simple structure, consisting of two layers of graphene and superconductor, forming a sandwich. “As the THz light falls on the sandwich it is reflected, like a mirror. “The main point is that there will be more light reflected than fell on the device.

“It works because external energy is supplied by a battery or by light that hits the surface from other higher frequencies in the electromagnetic spectrum.

“The THz photons are transformed by the graphene into massless electrons, which, in turn, are transformed back into reflected, energised, THz photons.

“Due to such a transformation the THz photons take energy from the graphene – or from the battery – and the weak THz signals are amplified.”

The breakthrough – made by researchers from Loughborough University, in the UK; the Center for Theoretical Physics of Complex Systems, in Korea; the Micro/Nano Fabrication Laboratory Microsystem and THz Research Center, in China and the AV Rzhanov Institute of Semiconductor Physics, in Russia – has been published in Physical Review Letters, in the journal, American Physical Society (APS).

The team is continuing to develop the device and hopes to have prototypes ready for testing soon. Prof Kusmartsev said they hope to have a working amplifier ready for commercialisation in about a year. He added that such a device would vastly improve current technology and allow scientists to reveal more about the human brain.

“The Universe is full of terahertz radiation and signals, in fact, all biological organisms both absorb and emit it. “I expect, that with such an amplifier available we will be able to discover many mysteries of nature, for example, how chemical reactions and biological processes are going on or how our brain operates and how we think.

“The terahertz range is the last frequency of radiation to be adopted by humankind. “Microwaves, infrared, visible, X-rays and other bandwidths are vital for countless scientific and technological advancements.

“It has properties which would greatly improve vast areas of science such as imaging, spectroscopy, tomography, medical diagnosis, health monitoring, environmental control and chemical and biological identification.

“The device we have developed will allow scientists and engineers to harness the illusive bandwidth and create the next generation of medical equipment, detection hardware and wireless communication technology.”

Tags:  amplifier  Fedor Kusmartsev  Graphene  Healthcare  Loughborough University  Medical 

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