# IITB Researchers Develop An Accurate Mathematical Model For High-Sensitivity Gallium Nitride Biosensors

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Researchers developed a biosensor model that captures the effect of the fluid-sensor interface charge.

Electrochemical biosensors are the biosensors that convert biological information, such as chemical concentrations, into a useful electrical signal. These sensors directly detect the concentration of the analyte from the measured electrical response proportional to the analyte (substance whose constituents are being identified) concentration obtained from the electrode. They can be used to detect cancers or other diseases early, measure pollution, or detect food contamination.

Gallium Nitride (GaN) is one of the preferred materials for the construction of such biosensors as the electrical properties of these devices allow them to sense small changes in charge. However, the manufacturing process involved in the production of GaN devices is expensive and complex. Accurate mathematical models are required to minimize the trial and error in the device design for making these sophisticated biosensors. Researchers from the Indian Institute of Technology Bombay have developed an accurate model for the GaN biosensor. The researchers claim that their model accounts for the surface charge at the interface of the transistor and the solution that contains the analyte which the earlier model did not consider.

A GaN based biosensor is a three terminal nanodevice known as bio- high electron mobility transistor or bioHEMT. The two terminals of this device, source and drain, form a current carrying channel and the current is regulated by the gate terminal of the device. The gate is coated with a layer of biorecognition element and is exposed to the analyte solution. The interaction between the analyte and the biorecognition element results in an electric charge that changes the gate voltage, thus changing the current through the transistor. This change in current is proportional to the concentration of the analyte and can therefore be used to measure it.

The mathematical model developed by the IITB researchers can determine the current through the device based on the electrical and physical properties of the biosensor, the biomarker concentration and the voltage applied at the gate. While developing the model, they even considered the surface charge at the interface of the transistor. The researchers successfully demonstrated their model by modeling the performance of a device to detect a molecule called prostate-specific antigen, the concentration of which increases in the case of prostate cancer.

The researchers validated their model against the values of the current calculated by a computational model that considers the effect of the charge layer at the interface. By doing so, they found that the values calculated by the analytical model proposed by the designers are seen to be in good agreement with the values calculated by the computational method.

The researchers say that the model could be extended to accurately estimate sensitivity for biosensors that can detect other types of cancer and various diseases characterized by early warning biomarkers.

Published Work: https://ieeexplore.ieee.org/document/9376098.