A Proposal for an Ultrasensitive Label-Free Optical BioMEMS Platform Based on a DBR-Michelson Interferometer for Cancer Detection and Therapeutic Applications.

Early detection of cancer remains challenging due to the extremely low concentration of biomarkers present during initial disease stages. Dysregulation of key signaling pathways, including cyclin-dependent kinase (CDK) networks, drives uncontrolled cell proliferation and tumor progression, underscoring the need for highly sensitive, label-free biosensing technologies. Conventional analytical methods such as ELISA and PCR offer reliable detection but require complex sample preparation, fluorescent labeling, and long processing times, limiting their suitability for rapid diagnostics. This work introduces a novel label-free Biological Micro-Opto-Electro-Mechanical System (BioMEMS) platform based on an unbalanced Michelson interferometer with DBR mirrors to interrogate the minute spectral shifts induced by biomolecular interactions. A microcantilever is suspended above a silicon-on-insulator (SOI) waveguide, where the specific binding of biomarkers generates compressive surface stress, causing a downward deflection that reduces the cantilever-to-waveguide gap. This displacement modulates the effective refractive index of the sensing arm through enhanced evanescent-field coupling. The resulting phase variation is further detected through the high-sensitivity Michelson interferometric architecture, enabling ultrasensitive spectral interrogation. Numerical simulations using COMSOL Multiphysics demonstrate a narrow full width at half maximum (FWHM) of 27.6 nm, a quality factor (Q) of 53.34, and an overall sensitivity of 75.74 µm/(N/m). These results highlight the potential of the proposed platform for early cancer detection and precise monitoring of dysregulated signaling pathways.