Highly-sensitive label-free protein sensor using MEMS Fabry-Perot interferometer

We report a MEMS-based label-free protein sensor which utilizes nonlinear optical transmittance change by a Fabry-Perot interference to enhance the sensitivity of surface-stress. The MEMS protein sensor is composed by a silicon photodiode and a free-standing thin film with a nano cavity. A deflection of the thin film caused by an antigen-antibody reaction is detected by a photocurrent change. Theoretical minimum detectable surface stress of the proposed sensor is predicted -1μN/m which is two orders of magnitude smaller than piezoresistive type. An Ag half mirror is deployed on the Fabry-Perot interferometer for high wavelength selectivity. The Ag mirror provides high transmittance and sharp spectrum of 35-nm-FWHM. The sensitivity of the Fabry-Perot interferometric protein sensor could be improved to 1.5 times by simple metal deposition process.