An Ultra-Sensitive 1D Photonic Crystal BioNEMS Platform for Label Free Detection of Biomolecules

Abstract

In this paper, we present a novel optical BioNEMS (Biological-Nano-Electro-Mechanical Systems) sensor based on a 1D photonic crystal (PhC) structure in order to develop a label free biosensing platform. The proposed biosensor consists of a BioNEMS cantilever as the tunable defect of the PhC detection part. This optical sensing system is a finite air hole photonic crystal with a nano air gap in the center of the structure so that the NEMS movable part can be freely displaced. Biomolecular interactions induce a surface stress on the functionalized surface of the movable structure. As a consequence, a nanomechanical bending occurs in the NEMS cantilever because of the released energy of binding events. This can change the defect of the proposed PhC which causes shifts in the transmitted wavelength for various concentrations of biomarkers. By analyzing the proposed device using numerical and analytical approaches, the functional characteristics of the present BioNEMS sensor are obtained as follows: optical sensitivity of 13452 nm/RIU, FOM of 7912 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> , mechanical sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.6~\mu \text{m}$ </tex-math></inline-formula> /Nm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and resonant frequency of 33.3 kHz. According to the results, this ultra-high sensitive sensor can be a promising choice to realize efficient label-free biosensors for early diagnoses of diseases in Point-of-Care Testing (POCT).