A Novel Photonic Crystal BioNEMS Sensing Platform Based on Fano resonances

A novel optical BioNEMS (Bio Nano-Electro-Mechanical-Systems) sensor based on a tunable 2D photonic crystal (PhC) cavity is proposed in this paper. The present device includes a functionalized BioNEMS cantilever and a tunable PhC structure. This optical detection system is a rod-type silicon photonic crystal cavity in which a designed defect allows the transmission of highly confined wave modes. While the immobilized capture probes are exposed to a solution containing the target biomarkers (i.e., DNA, mRNA or proteins), binding events cause a stress on the surface of the nanocantilever because of biological interactions. Therefore, the NEMS movable part is displaced as a result of an induced differential surface stress. This changes the position of the defect nanorods in the PhC cavity which leads to the transmitted wavelength variations. Finally, the concentration of biological quantities is measured by detecting the optical spectrum changes of the proposed biosensor. Furthermore, the presented BioNEMS sensor is analyzed by numerical and analytical approaches to obtain its functional characteristics as follows: optical sensitivity of 5140 nm/RIU, FOM of 10280 RIU-1, Q-factor of 3078, mechanical sensitivity of 1.05 µm/Nm-1 and resonant frequency of 23.45 kHz. Based on the obtained results, the proposed structure relied on Fano resonances provides a high-precision biosensor which has a great potential for highly sensitive detection of biomarkers in early diseases diagnosis as well as drug delivery test.