Graphene sheets are more than 200,000 times thinner than human hair and 200 times stronger than steel

Researchers at Imperial College London have improved an electronic sensor that can be used to quickly detect infectious diseases such as COVID-19.

This sensor, called an ion-sensitive field effect transistor (ISFET), can be integrated with electronic equipment to create an infectious disease test whose reliability may be comparable to PCR testing. They may perform as fast as a lateral flow test and provide a 30-minute infectious disease health test.

The current gold standard PCR test for COVID-19 testing must be sent to the laboratory for processing. A fast alternative, the lateral flow test, provides fast results, but with lower accuracy.

ISFET works by detecting changes in the pH (acidity) of the liquid and can be integrated into the "lab on a chip" technology to process the results on the chip very quickly. However, the liquid they come into contact with will change their sensing surface, which can lead to "drift"-uncontrollable, continuous and slow changes in the output signal without changing the acidity of the liquid.

Now, researchers at Imperial College London have added a layer of graphene sheet to the sensor-a single layer of carbon atoms, more than 200,000 times thinner than a human hair, but 200 times stronger than steel-and found that it can drift it. Reduce by 50%. Their new method is at its origin-the sensing surface-to combat the chemical instability of the sensor. This, combined with further enhancements, may be the key to solving ISFET drift, thereby providing a new generation of improved surface sensors for laboratory-on-a-chip applications such as disease testing.

The first author of the corresponding paper, Dr. Christoforos Panteli of the Department of Electrical and Electronic Engineering of Imperial College London, said: “The demand for reliable and fast laboratory-on-a-chip systems is very high. Our innovation means that surface-modified ISFETs may be a kind of The new one may be a better method for high-performance laboratory-on-a-chip chemical sensing systems to fight infectious diseases."

ISFET can be used to detect changes in pH of body fluids caused by viral RNA (such as SARS? CoV? 2 and Zika virus), and to monitor blood glucose levels in diabetic patients to detect infectious diseases.

During the manufacturing process, the process used to produce ISFET electronic chips deposits a material that is sensitive to the pH of the liquid being tested. The sensing top layer changes when it comes into contact with the liquid, causing real-time chemical drift to be found on the sensor.

The researchers proved that modifying the surface is an effective way to improve sensor performance without additional circuitry.

Although graphene improves performance by 50%, the researchers say that their improved method can be further developed to solve all the shortcomings of the sensor. The next step will be to improve the quality of the process of transferring graphene to the sensor surface. This will include discussions with industry about deposition methods that can maintain large-scale low-cost, and development of these methods in the laboratory.

Panteli et al. published "Using Graphene Sheets to Reduce the Drift of CMOS ISFET pH Sensors" published on IEEE Sensors 2021.

Article picture: Panteli et al.

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Imperial College London.

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Tel: 44 (0)20 7594 3415 Email: caroline.brogan@imperial.ac.uk Show all stories of the author

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