Graphene Sensors Gaining Steam

Article By : Liam Critchley

Graphene lends itself to being an effective sensing platform.

Graphene gathers a lot of interest for both high-tech and lower-tech applications but has typically taken a lot longer to be adopted in the more advanced technology sectors. One notable exception is graphene-based sensors, which have slowly and steadily been coming to the market across different industry sectors and from a range of companies around the world, including Cardea Bio, Emberion, Grolltex, Integrated Graphene, and Paragraf.

Graphene lends itself to being an effective sensing platform, and this has manifested in a range of ways—from more niche interesting applications to the heavy investment in a single subsector (biosensors). And if 2022 is anything to go by, then the trend is set to continue in the coming years.

Great interest in sensing applications

The properties of graphene are well-documented, and many people now understand that you can do a lot with graphene and that its properties are beneficial for a range of applications. While some of these aspects get hyped up, the fundamental properties of graphene have made it an excellent material of choice as the active sensing surface in a range of different sensing applications.

Graphene’s inherent thinness not only allows sensing devices to be much smaller and more flexible than when bulkier materials are used but also contributes to a very high and active surface area.

For sensing applications, the high surface area can be utilized to interact with a range of molecules—be it water, different gases, biomolecules, or some other molecular stimuli. Because graphene has an active surface, it also means that a number of different molecules and molecular receptors can be attached to a graphene sheet to tailor the sensor toward detecting specific molecular species of interest.

But this is only one aspect. The other reason is due to graphene’s high electrical conductivity, charge carrier mobility, and charge transfer properties. These properties mean that graphene sensors generally have a very high sensitivity, as any small interaction with the environment invokes a detectable response. So because the electronic properties of graphene are so good, each small interaction changes the resistivity across the graphene sheet. This means that very small amounts of environmental stimuli can be detected.

“Graphene has a wide application for the sensors market,” said Adrian Nixon, founder of the Nixene Journal. “Its electric conductivity can be tuned with exquisite precision to make very sensitive detectors.”

When coupled with their thinness, most graphene-based sensors are small but highly sensitive sensing devices that can be chemically tailored to detect a range of environmental stimuli. This is why there has been a lot of commercial interest in developing different graphene-based sensors for different applications and commercial markets.

Paragraf, Emberion innovating

While sensor applications in general tend to follow similar lines—strain sensors and humidity sensors, for example—some companies have developed commercial graphene sensors that are used in interesting applications.

An example is the Hall-effect sensor from Paragraf.

Hall-effect sensors measure changes in a magnetic field using the Hall effect, so it has opened some interesting application areas that other graphene sensors have not ventured into.

Paragraf teamed up in the past with CERN to map magnetic fields within the Large Hadron Collider, and it has been working with several other companies on sensors used in cryogenic environments and quantum computing.

Over the last year, Paragraf demonstrated that the graphene-based Hall-effect sensors are sensitive enough to measure currents in electric-vehicle batteries and monitor battery status.

“The breakthrough that Paragraf has made with graphene-based sensors is being able to deposit a single layer of contamination-free graphene directly on a wafer in a repeatable manner using standard semiconductor processes,” said Paragraf CEO Simon Thomas. “This has made many volume applications now possible—not only for magnetic and current sensors using the Hall effect but also fast and sensitive biosensors to detect biomarkers in liquid samples.”

Simon Thomas, Paragraf CEO (Source: Paragraf)

Another interesting application to manifest this year is from Emberion.

Emberion is an infrared camera manufacturer that partnered with the Graphene Flagship to integrate graphene into short-wave infrared detector imaging systems. While this is still in the prototype stage, a lot of funding has been approved with machine vision, automotive, and surveillance applications in mind.

Adapting biosensors for Covid

While there has been a range of markets targeted for graphene biosensors, a lot of commercial developments have come in the biosensor space—and there are many more being researched at an academic level. This is something that started to manifest before the Covid-19 pandemic, but the emergence of the coronavirus also prompted some graphene sensor manufacturers to adapt their existing sensing technologies for detecting SARS-CoV-2 viral strains.

One example of this is Grolltex.

Jeff Draa, CEO of San Diego, California–based Grolltex, said local research partners who were discussing using his firm’s graphene-based sensing platform in a cancer-based sensing project decided to put it on pause and “focus instead on Covid, which was in early days at the time.”

The molecular-based sensing platform that resulted is capable of many sensing modalities, “depending, for example, on what type of probes it is armed with at any given time,” he said. “So far, the sensor does not need sample enhancement techniques, such as PCR, to detect Covid, providing instant electronic detection of the presence of, in this case, SARS viral DNA.”

Commercialization discussions with several large diagnostics companies are ongoing, Draa said.

Jeff Draa, Grolltex CEO (Source: Grolltex)

Other graphene-tech manufacturers, such as Grapheal, also developed graphene-based sensing platforms for the pandemic.

Better known for some of its other healing-based, medical-device platforms, Grapheal developed a battery-free digital antigen test, known as the TestNpass, that is available to the public and can detect Covid-19 in a few minutes and transmit the result to a smartphone.

Grapheal CEO Vincent Bouchiat said the “TestNpass revisits the classic antigen strip by putting forward a digital tool that increases the potential of a field screening test. Because the biosensor is directly coupled to the smartphone, it increases the security and efficiency of the test, especially because we leverage the power of the smart card and NFC technology already offered by the electronic banking industry.”

Biosensors at the commercial forefront

Alongside Covid-specific biosensors, the general graphene biosensor market has continued to grow steadily over the last few years with many new products coming to market, and 2022 has been no different.

Integrated Graphene developed a 3D-graphene, foam-sensing platform known as the Gii Sens.

Integrated Graphene CEO Claus Marquordt describes the Gii Sens as “pure-graphene, on-demand—no inks, no binders, no additives, no transfer, no supply chain—sensor that outperforms gold sensors at the cost of printed carbon.”

Claus Marquordt, Integrated Graphene CEO (Source: Integrated Graphene)

This year, the Gii Sens has been integrated into a range of sensing platforms in conjunction with a number of collaborators for different health-monitoring applications, including detecting SARS-CoV-2, for the detection for biomarkers that signal complications during a liver transplant and, most recently, for the detection of glucose levels in diabetic patients’ blood.

Cardea Bio inks deal with Siemens center

Cardea Bio this year developed a biosignal processing unit (BPU) that uses graphene as the active sensing surface (in the form of a graphene FET).

The BPU has already been adapted for a range of biosensing applications, and the scope continues to grow. First designed to detect if a patient had cancer, the BPU is now set to be used to detect multiple disease biomarkers (including SARS-CoV-2)—thanks to a joint venture between Cardea and Siemens Healthineers Center for Innovation in Diagnostics, which the pair announced this year.

Most recently, Cardea said the BPU is going to be developed into an “electronic nose” for detecting diseases in a person’s breath. The platform, which may be used in developing countries, has attracted a $1.1 million grant from the Bill & Melinda Gates Foundation.

“At present, the successful commercial activity is focused more on the biosensor market,” the Nixene Journal’s Nixon said, giving as an example Cardea Bio’s scaling up the production. The firm has made more than 500,000 sensors, and its leaders believe they have the capacity to make more than 1 million by 2023, he added.

 

This article was originally published on EE Times.

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