Flexure-FET biosensor to break the fundamental sensitivity limits of nanobiosensors using nonlinear electromechanical coupling

Ankit Jain
Pradeep Nair, Purdue University
Muhammad A. Alam, Purdue University

Date of this Version



Proceedings of the National Academy of Sciences of the United States of America: vol. 109 no. 24 , Ankit Jain, 9304–9308


The final publication is available at http://dx.doi.org/10.1073/pnas.1203749109


In this article, we propose a Flexure-FET (flexure sensitive field effect transistor) ultrasensitive biosensor that utilizes the nonlinear electromechanical coupling to overcome the fundamental sensitivity limits of classical electrical or mechanical nanoscale biosensors. The stiffness of the suspended gate of Flexure-FET changes with the capture of the target biomolecules, and the corresponding change in the gate shape or deflection is reflected in the drain current of FET. The Flexure-FET is configured to operate such that the gate is biased near pull-in instability, and the FET-channel is biased in the subthreshold regime. In this coupled nonlinear operating mode, the sensitivity of Flexure-FET with respect to the captured molecule density is shown to be exponentially higher than that of any other electrical or mechanical biosensor. In addition, the proposed sensor can detect both charged and charge-neutral biomolecules, without requiring a reference electrode or any sophisticated instrumentation, making it a potential candidate for various low-cost, point-of-care applications.


Electrical and Computer Engineering