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SU-8 Based Flexure-FET Biosensor to Achieve Ultrasensitive Response
D. Chaurasiya, B. Srinivasan, S. Vanjari, S.G. Singh
Indian Institute of Technology, IN
Keywords: flexure-FET, biosensors, Young's modulus, stiffness
Summary:
This work presents SU-8 based Flexure-FET biosensor to achieve ultrasensitive response. Here, gate of FET is replaced with the fixed-fixed beam. Beam is biased near to pull-in instability (Vpi) and FET channel is biased in sub threshold regime (Vt). Flexure-FET is biased in sub-threshold regime below pull-in (i.e., Vt ≈ Vpi).We have chosen polySi (E = 160 GPa), gold (E = 33~54 GPa) and SU-8 (E = 2~4.4 GPa) as beam material and simulated the beam in real environment using Coventorware to compare their Vpi. Simulation results show that the SU-8 based beam exhibits the lowest Vpi. After selecting SU-8 as beam material, we optimized the dimensions of beam using Coventorware and modelled the FET whose Vt ≈ Vpi. When a biomolecule attaches with the functionalized beam of SU-8, it modulates the stiffness of the beam causing a non-linear deflection of beam. This non-linear deflection causes the change in potential of channel which results in order of change in drain current of FET. Results obtained show upto 4th order of change in drain current Id. We simulated the electromechanical coupling using COMSOL Multiphysics 4.4. To surmise now we have a platform to fabricate the Flexure-FET.
