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Paragraf and NPL Demonstrate that Paragraf’s Graphene Hall Effect Sensors are ready for High-radiation Applications in Space and Beyond

Posted By Graphene Council, 20 hours ago
Paragraf, the leader in graphene-based transformative electronic sensors and devices, has demonstrated the ability of its graphene Hall Effect sensors to withstand high levels of radiation. The discovery, based on testing from the National Physical Laboratory (NPL), proves that ‘unpackaged’ Hall Effect sensors can be used in high-radiation environments such as space. The project was funded by Innovate UK, the UK’s innovation agency.

Used to measure the magnitude of magnetic fields, Hall Effect sensors are a critical electronic component in a variety of applications, from proximity sensing and speed detection through to current sensing. However, historically, their deployment in high-radiation environments such as satellites and nuclear power plants has faced significant challenges. This is because conventional sensors made from silicon and other semiconductor materials react adversely to neutron radiation, unless they are encapsulated in radiation-hardened packaging. This entails a more complex, lengthy, and costly manufacturing process and may require the sensor to be replaced over time if, for example, the packaging is damaged.

By contrast, tests conducted by NPL have shown that following exposure to a neutron dose of 241 mSv/hour – which is about 30,000 times the expected typical neutron dose rate in the International Space Station – Paragraf graphene Hall Effect sensors are not affected by this level of radiation. This is the first time that a commercially available, graphene-based electronic device has proved impervious to neutron irradiation.

In situations where power and weight savings are as critical as radiation tolerance, for example on satellites and other space vehicles, Paragraf Hall Effect sensors really come into their own – requiring only pW’s of power and weighing only fractions of a gram.

Ivor Guiney, co-founder of Paragraf, commented: “NPL’s findings have the potential to be a game changer when it comes to high-performance satellites and other critical high-radiation applications such as nuclear decommissioning. Owing to the exceptional mechanical strength and high transparency of graphene, our Hall Effect sensor can be used reliably in high-radiation applications without requiring packaging. This is key to improving reliability and durability while reducing manufacturing costs and time to market.”

The ability of graphene Hall Effect sensors to perform under high-radiation conditions will pave the way for the deployment of a broader range of electronics in harsh environments. Thanks to Paragraf’s scalable manufacturing process for large-area graphene deposition, it may soon be possible to produce other radiation-resistant graphene-based electronic devices. This will help ensure that all critical electronics, beyond sensors, are reliable and durable even in harsh environments.

Héctor Corte-Leon at NPL added: “Our first set of findings is very promising, and we are now expecting more positive outcomes over the next few months. Testing graphene-based electronics is key to demonstrating whether they can be used in harsh environments where, traditionally, their deployment has been limited.”

Graphene Hall Effect sensors from Paragraf are now set to undergo further radiation testing (alpha, beta and gamma radiation) as well as high-frequency testing. This is expected to open-up new opportunities across critical applications such as current sensing. The project, funded by Innovate UK, the UK’s innovation agency, started in October 2019, and is due to run until the end of 2020.

Tags:  Electronics  Graphene  Héctor Corte-Leon  Innovate UK  Ivor Guiney  National Physical Laboratory  Paragraf  Sensors 

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Soil check: How much water does your soil contain?

Posted By Graphene Council, 21 hours ago
Researchers use ultra-small graphene particles to develop a new soil moisture sensor. Anyone who has tried their hand at growing plants, be it an amateur gardener or a seasoned farmer, would be familiar with the perils of under- or over-watering a sapling. Plants require the right amount of water for their healthy growth, and to figure out when and how much to water one has to know the existing moisture levels in the soil. When it comes to keeping track of the watering schedule for a large number of plants, such as for a field of crops, there is a need for an affordable, easy-to-use soil moisture sensor that can accurately measure the water content in the soil. 

A recent study, published in the journal Carbon, demonstrates the workings of a soil moisture sensor made from graphene quantum dots, which are nanometer-sized fragments of graphene. The study was conducted by a team of researchers from the Indian Institute of Technology, Bombay (IIT Bombay), Gauhati University, and Dhirubhai Ambani Institute of Information and Communication Technology, Gandhinagar. It was funded by the Department of Science and Technology, the University Grants Commission and the Assam Science Technology and Environmental Council.

Graphene is made up of a sheet of carbon atoms arranged in a honeycomb-like pattern. Over the years, studies have explored the use of graphene quantum dots — disc-shaped materials made of a few layers of graphene, measuring mere nanometers — for a variety of sensing applications. While extensive research is being carried out on the synthesis of graphene quantum dots, the challenge remains in designing a method that results in a good yield of uniformly-sized particles. Additionally, the process must be scalable and easily adaptable for its  commercialisation.

“Our motivations behind this study was to devise a simple, inexpensive and scalable approach for synthesising graphene quantum dots, and to develop an affordable soil moisture sensor that is suitable for large scale use,” says Prof Hemen Kalita, who is the lead author of this study. He is an Assistant Professor at the Gauhati University and previously was a doctoral student with Prof M Aslam at IIT Bombay. 

The researchers have proposed a method to produce graphene quantum dots as small as 3–5 nanometre from easily available and low-cost graphene oxide. They coated a thin film of graphene oxide onto a carbon electrode and placed it inside an electrolyte solution. When an electric current is applied to the setup, the carbon bonds in the graphene oxide get cleaved, and molecules of the electrolyte occupy those gaps in the graphene oxide layer. Eventually, they form quantum dots of graphene having oxygen-containing chemical groups. 

“At a laboratory scale, we were successful in synthesising graphene quantum dots through our novel approach, and we have filed a patent for the synthesis method,” says Prof Kalita. 

Using the graphene quantum dots, the researchers fabricated a soil moisture sensor which is smaller in size than a lentil seed. The moisture content value displayed by the sensor depends on the resistance measured across it, and with an increasing percentage of water content, there is a fall in resistance. When the sensor is inserted into moist soil, the oxygen atoms present in the graphene quantum dots interact with the hydrogen atoms of the water and form a layer of water molecules on the surface of the sensor. When an external voltage is applied to the sensor via a source meter, the loosely held water molecules in the upper layers get ionised and conduct electrical charge. This leads to a decrease in resistance of the sensor.  

The researchers tested the soil moisture sensors on samples of black and red soil. They found that the moisture content measured by the sensor closely matched the known water content of the soil samples. The sensor gives the final reading within 3 minutes and can be used again after 20 seconds.  

Further, the researchers tested the stability of the sensor by continuously using it over five months to measure the water content in soil samples. They found that the sensor gives a consistent reading throughout this time and works well for a range of soil water levels.  

“With extensive field testing and improved packaging, our sensors will be suitable for commercialisation. A few companies have approached us and initiated discussions with our team to take this project to the industry front,” says Prof Kalita. “We are aiming to develop stable and affordable sensors for the middle-class farmer community,” he signs off. 

Tags:  Gauhati University  Graphene  graphene oxide  Hemen Kalita  Sensors 

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Graphene enables the smallest, most sensitive sensors

Posted By Graphene Council, Saturday, September 19, 2020
We interview Peter Steeneken, from Graphene Flagship partner TU Delft, and Leader of the Graphene Flagship Sensors Work Package, on the advantages of graphene and related materials in the development of sensing devices – particularly NEMS. NEMS stands for nanoelectromechanical systems: a class of miniaturised devices that detect stimuli like air pressure, sound, light, acceleration or the presence of gases and chemical compounds.

NEMS production methods resemble those of the manufacture of classic transistors, so they can achieve similar production costs and widespread commercialisation. The Graphene Flagship is integrating graphene and related materials in NEMS. Keep reading to discover the future of miniaturised sensing!

"Graphene allows for ultimate force sensitivities in high-performance pressure sensors, microphones and accelerometers."- Peter Steeneken, Graphene Flagship 'Sensors' Leader

What exactly are NEMS sensors?

The NEMS acronym, meaning nanoelectromechanical systems, comprises a family of electric and electronic devices with nanometric dimensions that are mechanically movable. In the Graphene Flagship Sensors Work Package, we are mostly interested in NEMS sensors, which can measure air pressure, sound, light intensity, acceleration, or the presence of gases. To measure such forces you need motion, so movable parts are essential for NEMS.

Currently, MEMS (NEMS' micrometric 'big' cousins) have similar functionalities and are already produced in high volumes – up to billions of MEMS sensors per year – for devices like smartphones. Since they are produced using similar methods as CMOS electronics, they can be made small and with low production costs, which has accelerated their widespread commercialization.

NEMS are nanoscale devices – much smaller devices than classic MEMS. Their smaller size has several advantages: NEMS have higher sensitivity, and many of them can be placed on the same area that would be taken up by a single MEMS sensor. Moreover, NEMS are potentially cheaper, because they need less material to make, so more sensors can be produced from a single silicon wafer. The nanometric size of NEMS also enables new sensing functionalities. For instance, NEMS can even detect individual molecules and count them.

What innovative features does graphene bring to the NEMS field?

Since graphene is only one atom thick, it is the thinnest NEMS device-layer one can imagine. In terms of mechanical properties, graphene is stiff yet very flexible – suspended graphene can be deflected out-of-plane, allowing for ultimate force sensitivities in high-performance pressure sensors, microphones and accelerometers.

At the same time, graphene membranes are very robust. By tensioning graphene like a guitar string, its spring constant can be tuned and engineered to the desired value. The high electrical conductivity of graphene is also advantageous in electrical actuation, needed to provide the readout of sensors.

Although graphene is impermeable to gases in its pristine form – something that can be essential for pressure sensors – we can also tailor it with small pores and make it permeable or semi-permeable for gases and liquids, enabling completely new sensing functions. Compared to other types of thicker membranes, fluids can permeate at higher rates through graphene, which enables faster and lower power operation of sensing and separation devices. During the last years, the feasibility and potential of graphene for realizing novel and improved graphene NEMS sensors has become more apparent, as we describe in a recent review.1

"Graphene sensors could also increase our safety, [...] warn us in case of poor ventilation or remind us to wear a mask." - Peter Steeneken, Graphene Flagship 'Sensors' Leader

Graphene is one material in a huge family – can other layered materials be applied to NEMS devices as well?

Certainly. MEMS devices already use combinations of materials in the suspended layers: electrical conductors, semiconductors, insulators, optical and magnetic active layers, as well as piezoresistive and electric layers for sensing and actuation. We envisage that similar suspended heterostructures might be realised in NEMS by combining different types of layered materials.

We have already shown NEMS that use layered materials with high piezoresistive constants and others that showcase resistances that make them very sensitive to changes in gas compositions. Another approach for NEMS sensors would be to cover graphene with thin functionalisation layers, enabling new types of gas and biosensors as outlined in a recent focus issue edited by Arben Merkoci, from Graphene Flagship partner ICN2, Spain, and member of the Sensors Work Package.2

What are the applications of graphene-based NEMS sensors?

There is a wide range of applications that can be targeted. We could replace sensors in our mobile phones by smaller, more sensitive devices. These will allow better indoor navigation, thanks to acceleration and pressure sensors and directional low-noise microphones.

Graphene sensors could also increase our safety: our phone could warn us in case of poor ventilation, detecting increased CO2 levels in the environment – or remind us to wear a mask, if it senses that air pollution reaches dangerous thresholds. Beyond, high-end laboratory instruments, such as scanning probe microscopes, might also benefit from the flexibility of graphene.2

"With graphene, we could replace sensors in our smartphones by smaller, more sensitive devices." -  Peter Steeneken, Graphene Flagship 'Sensors' Leader

For you, which is the most exciting application of graphene for sensing?

I am excited about creating sensor platforms by combining multiple graphene sensors together. By making new combinations, sensors can become more selective and undesired crosstalk can be eliminated. Moreover, by combining the output of multiple sensors, we can extract more information about our environment.

For gas sensors, the combination of outputs provides a "fingerprint" of gas composition. Similarly, by combining outputs of accelerometers, pressure sensors, magnetometers, and microphones, we can deduce if someone is walking, biking, climbing stairs or driving a car.

I believe that some of the most exciting and impactful new applications of these graphene sensors will be in the medical domain: by developing graphene sensor platforms that can help us better detect and diagnose diseases. In fact, one of the latest Graphene Flagship spin-offs, INBRAIN Neuroelectronics, will design graphene-based sensors and implants to optimise the treatment of brain disorders, such as Parkinson's and epilepsy. Moreover recently, the production of graphene biosensors has advanced, and Graphene Flagship partner VTT, in Finland, already sells CMOS integrated multiplexed biosensor matrices for testing and development purposes.

Are graphene-enabled NEMS ready to jump onto the market?

During the last few years, we showed that graphene NEMS sensors can outperform current commercial MEMS sensors in several aspects. To get to the market, we need to show that graphene sensors can outperform current products in all aspects – including high-volume reliable production at a competitive cost.

To achieve this, more development is needed. The push of the Graphene Flagship towards industrialisation and large-scale manufacturing, will accelerate the NEMS sensors entry into the market. 

Just like MEMS, graphene NEMS have benefited from established CMOS fabrication methods, which facilitate high-volume low-cost production. Introducing a new material into a CMOS factory often takes between five and ten years of development.

These advances are achieved through international and multidisciplinary collaboration. In fact, the Graphene Flagship Sensors Work Package comprises a collaborative endeavour between industry and academia: Chalmers University of Technology (Sweden), ICN2, ICFO, Graphenea (Spain), RWTH Aachen, Bundeswehr University of Munich, Infineon Technologies (Germany), University of Tartu (Estonia), VTT (Finland) and TU Delft (Netherlands) - all Graphene Flagship partners.

With the support of the European Commission, the Graphene Flagship will soon start setting up set up an experimental pilot line to integrate graphene and related layered materials in a semiconductor platform. This will not only accelerate graphene device fabrication, but also accelerate the development of new graphene-enabled devices, providing an identical repeatable device fabrication flow.

Tags:  Arben Merkoci  Graphene  Graphene Flagship  ICN2  INBRAIN Neuroelectronics  Peter Steeneken  Sensors  TU Delft 

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New low-cost method upscales & produces twisted multilayer highly conducting graphene

Posted By Graphene Council, Thursday, September 17, 2020
Graphene, the one-atom-thick sheet of carbon atoms, which is a boon for energy storage, coatings, sensors as well as superconductivity, is difficult to produce while retaining its single layered properties.

A new low-cost method of upscaling production of graphene while preserving its single layered properties, developed by Indian scientists, may reduce the cost of producing this thinnest, strongest and most conductive material in the world.

Researchers from Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) an autonomous institute under the Department of Science & Technology, Government of India through their recent research work have upscaled graphene production while retaining its thin layered properties. This was made possible by a simple, affordable method wherein naphthalene coated nickel foil was heated for a few minutes in an ordinary vacuum by joule heating and was cooled to get twisted layers of graphene. Careful study using electronic diffraction and Raman scattering showed that the 2D single-crystal nature of the atomic lattice of the graphene is retained even in the multilayer stack. The twisted multilayer graphene that results is also highly conducting.

In the research by Nikita Gupta (Ph.D. student, JNCASR) and Prof. G.U. Kulkarni (corresponding author ) published in the ‘Journal of Physical Chemistry Letters’, the scientists have also defined a formula to quantify how much single layer like behaviour exists in such a system. The twisted system has multiple layers, each behaving like a single layer, allows variation in the experimental data within one sample, thus making quantification possible to achieve. The derived formula provides an insight into any twisted hexagonal multilayer system and may be used to tune superconductivity.

The researchers used a combination of two techniques to understand and quantify how much single layer like behaviour exists in the graphene system. Raman spectroscopy---a technique to understand whether a graphene species has single layer like behaviour arising because of no interlayer interaction and electron diffraction--a technique to study the morphology of the given twisted system.

Observing fascinating properties of twisted multilayer graphene such as visible absorption band, efficient corrosion resistance, temperature-dependent transport, influencing the crystalline orientation of source material, helped the JNCASR team to understand the landscape of the given twisted multilayer graphene system.

Recent publication in the journal ‘Nature’ by James M. Tour, an eminent peer on this research discovery (https://doi.org/10.1038/s41586-020-1938-0), confirms the upper limit of relative Raman intensity predicted by this work, experimentally. The present understanding of twisted multilayer graphene will help in understanding any twisted hexagonal system. It gives an upper limit of relative Raman intensity which can exist in a particular multilayer graphene system.

Tags:  energy storage  G.U. Kulkarni  Graphene  Jawaharlal Nehru Centre for Advanced Scientific Re  Sensors 

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Understanding electron transport in graphene nanoribbons

Posted By Graphene Council, Tuesday, September 15, 2020
Graphene is a modern wonder material possessing unique properties of strength, flexibility and conductivity whilst being abundant and remarkably cheap to produce, lending it to a multitude of useful applications -- especially true when these 2D atom-thick sheets of carbon are split into narrow strips known as Graphene Nanoribbons (GNRs).

New research published in EPJ Plus, authored by Kristians Cernevics, Michele Pizzochero, and Oleg V. Yazyev, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland, aims to better understand the electron transport properties of GNRs and how they are affected by bonding with aromatics. This is a key step in designing technology such chemosensors.

"Graphene nanoribbons -- strips of graphene just few nanometres wide -- are a new and exciting class of nanostructures that have emerged as potential building blocks for a wide variety of technological applications," Cernevics says.

The team performed their investigation with the two forms of GNR, armchair and zigzag, which are categorised by the shape of the edges of the material. These properties are predominantly created by the process used to synthesise them. In addition to this, the EPFL team experimented p-polyphenyl and polyacene groups of increasing length.

"We have employed advanced computer simulations to find out how electrical conductivity of graphene nanoribbons is affected by chemical functionalisation with guest organic molecules that consist of chains composed of an increasing number of aromatic rings," says Cernevics.

The team discovered that the conductance at energies matching the energy levels of the corresponding isolated molecule was reduced by one quantum, or left unaffected based on whether the number of aromatic rings possessed by the bound molecule was odd or even. The study shows this 'even-odd effect' originates from a subtle interplay between the electronic states of the guest molecule spatially localised on the binding sites and those of the host nanoribbon.

"Our findings demonstrate that the interaction of the guest organic molecules with the host graphene nanoribbon can be exploited to detect the 'fingerprint' of the guest aromatic molecule, and additionally offer a firm theoretical ground to understand this effect," Cernevics concludes: "Overall, our work promotes the validity of graphene nanoribbons as promising candidates for next-generation chemosensing devices."

These potentially wearable or implantable sensors will rely heavily on GRBs due to their electrical properties and could spearhead a personalised health revolution by tracking specific biomarkers in patients.

Tags:  Biosensor  EPFL  Graphene  Graphene Nanoribbons  Healthcare  Kristians Cernevics  Michele Pizzochero  Oleg V. Yazyev  Sensors 

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A multivalued optical memory composed of 2D materials

Posted By Graphene Council, Friday, September 11, 2020
The National Institute for Materials Science (NIMS) has developed a memory device capable of storing multiple values using both optical and voltage input values. This device composed of layered two-dimensional materials is able to optically control the amount of charge stored in these layers. This technology may be used to significantly increase the capacity of memory devices and applied to the development of various optoelectronic devices. The research was published in Advanced Functional Materials ("Laser-assisted multilevel non-volatile memory device based on 2D van-der-Waals fewlayer-ReS2/h-BN/Graphene Heterostructures").

Memory devices used to store information (e.g., flash memory) play an indispensable role in today’s information society. The recording density of these devices has substantially increased in the past 20 years. In anticipation of widespread adoption of IoT technologies in the near future, it is desirable to accelerate the development of higher speed, larger capacity memory devices.

However, the current approach to increasing memory capacity and energy efficiency through silicon microfabrication is about to reach its limits. Development of memory devices with different working principles therefore has been awaited.

To meet expected technology needs, this research group has developed a transistor memory device composed of layered two-dimensional materials, including rhenium disulfide (ReS2) – a semiconductor – serving as a channel transistor, hexagonal boron nitride (h-BN) used as an insulating tunnel layer and graphene functioning as a floating gate.

This device records data by storing charge carriers in the floating gate in a manner similar to conventional flash memory. Hole-electron pairs in the ReS2 layer are prone to excitation when irradiated with light. The number of these pairs can be regulated by changing the intensity of the light.

The group succeeded in creating a mechanism that allows the amount of charge in the graphene layer to gradually decrease as the exited electrons once again couple with the holes in this layer. This success enabled the device to operate as a multivalued memory capable of efficiently controlling the amount of stored charge in stages through the combined use of light and voltage.

Moreover, this device can operate energy efficiently by minimizing electric current leakage—an achievement made possible by layering two-dimensional materials, thereby smoothening the interfaces between them at an atomic level.

This technology may be used to significantly increase the capacity and energy efficiency of memory devices. It also may be applied to the development of various optoelectronic devices, including optical logic circuits and highly sensitive photosensors capable of controlling the amount of charge stored in them through combined use of light and voltage.

This project was carried out by a research group consisting of Yutaka Wakayama (Leader of the Quantum Device Engineering Group (QDEG), International Center for Materials Nanoarchitectonics (MANA), NIMS), Bablu Mukherjee (Postdoctoral Researcher, QDEG, MANA, NIMS) and Shu Nakaharai (Principal Researcher, QDEG, MANA, NIMS).

This study was conducted in conjunction with another project entitled “Development of a ultra-sensitive photosensor using two-dimensional atomic film layers” funded by the Grant-in-Aid for JSPS Fellows.

Tags:  2D materials  Bablu Mukherjee  Graphene  International Center for Materials Nanoarchitecton  optoelectronics  Semiconductor  Sensors  Shu Nakaharai  The National Institute for Materials Science  Yutaka Wakayama 

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First 2D neural network

Posted By Graphene Council, Tuesday, September 8, 2020
Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) in collaboration with Samsung Advanced Institute of Technology have developed the first neural network for artificial intelligence made using two-dimensional materials. Two-dimensional materials are substances with a thickness of a few nanometers or less, often consisting of a single sheet of atoms. This machine vision processor made from these materials can capture, store and recognize more than 1,000 images. 

“This work highlights an unprecedented advance in the functional complexity of 2D electronics,” said Donhee Ham, the Gordon McKay Professor of Electrical Engineering and Applied Physics at SEAS and senior author of the paper. “We have performed both front-end optical image sensing and back-end image recognition in one, 2D, material platform.”

This work highlights an unprecedented advance in the functional complexity of 2D electronics. DONHEE HAM, GORDON MCKAY PROFESSOR OF ELECTRICAL ENGINEERING AND APPLIED PHYSICS.

Since the discovery of graphene in 2004, researchers have been working to harness the unique electronic and optoelectronic properties of atomically thin, two-dimensional semiconductors for the basic building blocks of a range of applications. 

Transistors made from two-dimensional materials have been used for simple digital logic circuits and photodetectors but large-scale integration for complex computing, such as artificial intelligence, has remained out of reach. So far, researchers have only been able to integrate about 100 transistors made from two-dimensional materials onto a single chip.  To put that in perspective, standard silicon integrated circuits, such as those in your smartphone, contain billions of transistors. 

Now, Ham and his team have developed an integrated circuit with more than 1,000 two-dimensional material-based transistors.  

“Two-dimensional material-based devices exhibit various exciting properties, but low integration level has restricted their functional complexity,” said Houk Jang, a research associate at SEAS and first author of the paper. “With 1,000 devices integrated on a single chip, our atomically thin network can perform vision recognition tasks, which is a remarkably advanced functionality of two-dimensional material-based electronics.”

The research team used a two-dimensional material called molybdenum disulfide (MoS2), the three-atom thick semiconductor, which interacts well with light. They arranged these photosensitive transistors into what’s known as a crossbar array, which is inspired by neuronal connections in the human brain. This relatively simple set-up allows the device to act as both an eye that can see an image and a brain that can store and recognize an image. 

On the front end, the crossbar array acts like an image sensor, capturing an image just like an eye. The photosensitivity of the materials means that the image can be stored and converted into electrical data. On the back end, the same crossbar array can perform networked computing on that electrical data to recognize and identify the image.

To demonstrate the process, the researchers showed the device 1,000 images of handwritten digits. The processor was able to identify the images with 94 percent accuracy.

“Through capturing of optical images into electrical data like the eye and optic nerve, and subsequent recognition of this data like the brain via in-memory computing, our optoelectronic processor emulates the two core functions of human vision,” said Henry Hinton, a graduate student at SEAS and coauthor of the paper. 

“This is the first demonstration of a neural network with two-dimensional materials that can interact with light,” said Jang. “Because it computes in memory, you don’t need separate memory and the calculation can be done with very low energy.” 

Next, the team aims to scale up the device even further for two-dimensional material-based, high resolution imaging system.

Tags:  2D materials  Donhee Ham  Graphene  Harvard John A. Paulson School of Engineering  Samsung Advanced Institute of Technology  Sensors  transistors 

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An improved wearable, stretchable gas sensor using nanocomposites

Posted By Graphene Council, Friday, August 28, 2020
A stretchable, wearable gas sensor for environmental sensing has been developed and tested by researchers at Penn State, Northeastern University and five universities in China.

The sensor combines a newly developed laser-induced graphene foam material with a unique form of molybdenum disulfide and reduced-graphene oxide nanocomposites. The researchers were interested in seeing how different morphologies, or shapes, of the gas-sensitive nanocomposites affect the sensitivity of the material to detecting nitrogen dioxide molecules at very low concentration. To change the morphology, they packed a container with very finely ground salt crystals.

Nitrogen dioxide is a noxious gas emitted by vehicles that can irritate the lungs at low concentrations and lead to disease and death at high concentrations.

When the researchers added molybdenum disulfide and reduced graphene oxide precursors to the canister, the nanocomposites formed structures in the small spaces between the salt crystals. They tried this with a variety of different salt sizes and tested the sensitivity on conventional interdigitated electrodes, as well as the newly developed laser-induced graphene platform. When the salt was removed by dissolving in water, the researchers determined that the smallest salt crystals enabled the most sensitive sensor.

“We have done the testing to 1 part per million and lower concentrations, which could be 10 times better than conventional design,” says Huanyu Larry Cheng, assistant professor of engineering science and mechanics and materials science and engineering. “This is a rather modest complexity compared to the best conventional technology which requires high-resolution lithography in a cleanroom.”

Ning Yi and Han Li, doctoral students at Penn State and co-authors on the paper in Materials Today Physics, added, “The paper investigated the sensing performance of the reduced graphene oxide/moly disulfide composite. More importantly, we find a way to enhance the sensitivity and signal-to-noise ratio of the gas sensor by controlling the morphology of the composite material and the configuration of the sensor-testing platform. We think the stretchable nitrogen dioxide gas sensor may find applications in real-time environmental monitoring or the healthcare industry.”

Other Penn State authors on the paper, titled “Stretchable, Ultrasensitive, and Low-Temperature NO2 Sensors Based on MoS2@rGO Nanocomposites,” are Li Yang, Jia Zhu, Xiaoqi Zheng and Zhendong Liu.

Tags:  composite  Graphene  graphene oxide  Healthcare  Huanyu Larry Cheng  nanocomposites  Northeastern University  Penn State  Sensors 

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New Device Can Measure Toxic Lead Within Minutes

Posted By Graphene Council, Wednesday, August 26, 2020
Rutgers researchers have created a miniature device for measuring trace levels of toxic lead in sediments at the bottom of harbors, rivers and other waterways within minutes – far faster than currently available laboratory-based tests, which take days.

The affordable lab-on-a-chip device could also allow municipalities, water companies, universities, K-12 schools, daycares and homeowners to easily and swiftly test their water supplies. The research is published in the IEEE Sensors Journal.

“In addition to detecting lead contamination in environmental samples or water in pipes in homes or elementary schools, with a tool like this, someday you could go to a sushi bar and check whether the fish you ordered has lead or mercury in it,” said senior author Mehdi Javanmard, an associate professor in the Department of Electrical and Computer Engineering in the School of Engineering at Rutgers University–New Brunswick.

“Detecting toxic metals like lead, mercury and copper normally requires collecting samples and sending them to a lab for costly analysis, with results returned in days,” Javanmard said. “Our goal was to bypass this process and build a sensitive, inexpensive device that can easily be carried around and analyze samples on-site within minutes to rapidly identify hot spots of contamination.”

The research focused on analyzing lead in sediment samples.  Many river sediments in New Jersey and nationwide are contaminated by industrial and other waste dumped decades ago. Proper management of contaminated dredged materials from navigational channels is important to limit potential impacts on wildlife, agriculture, plants and food supplies. Quick identification of contaminated areas could enable timely and cost-effective programs to manage dredged materials.

The new device extracts lead from a sediment sample and purifies it, with a thin film of graphene oxide as a lead detector. Graphene is an atom thick layer of graphite, the writing material in pencils.

More research is needed to further validate the device’s performance and increase its durability so it can become a viable commercial product, possibly in two to four years.

This project was done in collaboration with the Department of Electrical and Computer Engineering and Rutgers’ Center for Advanced Infrastructure and Transportation (CAIT). It was funded by CAIT, the USDOT-University Transportation Research Center–Region II.

Tags:  Graphene  graphene oxide  Mehdi Javanmard  Rutgers University  Sensors  water purification 

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Using brainwaves to command and control autonomous vehicles

Posted By Graphene Council, Wednesday, August 26, 2020
Researchers at the University of Technology Sydney (UTS) are using smart sensors and advanced brain signal decoders to improve communication between human brains and robots.

A team led by Distinguished Professor CT Lin and Professor Francesca Iacopi will embark on a two-year project with the Department of Defence to examine how cutting-edge technologies could use brainwaves to command and control autonomous vehicles.

Distinguished Professor CT Lin, Director of The UTS Computational Intelligence and Brain Computer Interface Centre, is a leading researcher in brain computer interfaces (BCI). 

An expert in wearable and wireless devices, Professor Lin combines human physiological information with artificial intelligence (AI) to develop advanced monitoring and feedback systems.

“I want to improve the flow of information from humans to robots, so humans can make better informed decisions,” said Professor Lin.

An internationally-recognised expert in nanotechnology, Professor Francesca Iacopi will design and produce the graphene-based smart sensors required for the wearable device.  

Professor Iacopi has developed a novel method to embed graphene-based microdevices on silicon wafers. The process can be adapted for large-scale manufacturing. 

Professor Iacopi said most graphene synthesis methods are not compatible with semiconductor technologies, precluding miniaturised applications. 

“The new synthesis I developed will help obtain graphene from sources that make it more accessible and affordable.”

The project has received $1.2 million in funding from the Defence Innovation Hub.

The innovative technology has potential applications across multiple sectors including MedTech and biotechnology.

Tags:  artificial intelligence  Chin Teng Lin  Francesca Iacopi  Graphene  Sensors  University of Technology Sydney 

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