Performance analysis of ISFET biosensor with different structures

Abstract

Ion-sensitive field-effect transistor (ISFET) biosensor has gained popularity in clinical research field for biomolecules detection due to its high detection sensitivity, mass-production capability, and low manufacturing cost. Proteins are needed by all living cells for structural and functional purposes. However, some proteins such as Bovine Serum Albumin (BSA) can cause allergic reactions in human body. Besides, instability of Liposome may result in medication leaks that could harm cells. The first objective of this project is to study the effect of different proteins on the performance of different structures of ISFET biosensor. There are several limitations of ISFET biosensor such as lack of good solid-state electrodes, parasitic sensitivity to temperature and light and time dependent instability of sensor parameters. Enhancement on ISFET structures could be a good approach to improve the ISFET performance. The second objective of this research is to compare the performance of ISFET biosensors of different nanoelectronics structure in terms of settling time, sensitivity, and selectivity. In this project, an open-source software, nanohub BioSensorLab was used to simulate the settling time, sensitivity, and selectivity of the biosensors. The target proteins are Liposome and Bovine serum albumin (BSA) while the bioreceptor is collagen. Different structures of ISFET biosensor were simulated and analysed, which are planar ISFET, cylindrical nanowire, nanosphere and double-gate FET biosensors. In this research, the impact of proteins’ diffusion coefficient, structures of biosensor and analyte concentration towards the settling time was analysed. Next, the sensitivity relied on the structures of biosensor. Therefore, the analysis carried out independently for different structures of biosensor. Selectivity is determined by the size of receptor molecules and parasitic molecules, concentration of target molecules and parasitic molecules. From the simulation results, the settling time decreased when analyte concentration and protein diffusion coefficient increased. In addition, the settling time increased from planar and double-gate, cylindrical nanowire to nanosphere biosensor. To obtain high sensitivity in planar ISFET biosensor, the width and the electrolyte concentration are increased while the oxide thickness and the length are decreased. For cylindrical nanowire biosensor, increasing the radius, oxide thickness and reducing the buffer ion concentration can improve the sensitivity. To obtain high sensitivity in double-gate FET, the width, back oxide thickness, and silicon body thickness need to increase while the length and top oxide thickness need to decrease. The selectivity is the same regardless of the ISFET structures. High selectivity can be obtained by increasing the size of receptor and parasitic molecules, concentration of target molecules, and decreasing the concentration of parasitic molecules. Diffusion coefficient of proteins have no impact towards the sensitivity and selectivity of ISFET biosensors.