Dynamic characterization of MEMS-SPM in liquid for biomechanical phenotyping using fiber interferometry

Micro- and nano-force sensors and actuators based on microelectromechanical systems (MEMS) are widely used across industrial and scientific domains, including the characterization of ultra-compliant materials with elastic moduli down to the MPa range. With their nano-Newton sensitivity, these sensors also offer great potential for biomechanical phenotyping of biological materials in liquid environments, enabling assessment of viscoelastic properties for early disease diagnostics. To ensure reliable application in biological research, a thorough understanding of MEMS sensor dynamics in liquid is essential. However, characterizing these sensors in aqueous media is challenging due to strong damping and the complexity of small-scale force measurements. In this manuscript fiber interferometry has been utilized to evaluate the quasi-static and dynamic performance of MEMS nano-force sensors in liquid. Owing to their high sensitivity and non-invasive nature, fiber interferometers are well-suited for in-situ characterization. A proof-of-principle experimental setup has been developed, integrating a fiber interferometer into a MEMS nano-force sensor in liquid. First results indicate that this approach enables a quantitative characterization of the dynamic parameters of silicon micro-sensors, such as resonance frequency and quality factor, and thus supports future MEMS applications in biomedical and nanotechnological research.