An Ultrasensitive MOEMS Platform Relied on an Adjustable Defect Width for Label-Free Bioparticle Detection

This article presents a novel optomechanical surface stress-based biosensor. The proposed device employs a functionalized microelectromechanical systems (MEMS) transducer to capture the target bioparticles in the sample. The interaction of the bioreceptors immobilized on the transducer surface with the target bioparticles modifies the transducer’s surface stress, which results in its deformation. The accurate measurement of the transducer deformation allows for label-free detection of the target bioparticles and their concentration. In order to measure the transducer deformation, an optical system consisting of a defective 1-D photonic crystal with adjustable defect width is utilized, which significantly enhances the sensor sensitivity. This BioMEMS platform exhibits improved functional characteristics, including a bandwidth (BW) of 5 kHz, full-width at half-maximum (FWHM) of 0.8 nm, quality factor of 1822.5, mechanical sensitivity of $13.5~\mu $ m/Nm ${}^{-{1}}$ , optical sensitivity of 1.02, and total sensitivity of $13.775~\mu $ m/Nm ${}^{-{1}}$ . These functional characteristics demonstrate the capability of the proposed sensor to detect various diseases in their early stages or progression, which is highly desirable in point-of-care testing (POCT) applications.