Silicon microsurgery-force sensor based on diffractive optical MEMS encoders

This paper presents a micrograting-based force sensor integrated with a surface micromachined silicon-nitride probe suitable for characterizing microsurgery force on a single cell or embryo. The probe is supported by springs of a known spring constant, and the surgical penetration force is determined from displacement measurements. The opticalencoder force sensor exhibits conŽgurable sensitivity and dynamic range, allowing monitoring over a wide range of forces. The periodicity of the encoder response can be used for calibration of the injector displacement and to obtain information about the localized elastic properties of the target. We used a force sensor with a measured spring constant of 1.85 N/m for penetration force measurements on Drosophila embryos, and found a penetration force of 52.5 mN (± 13.2 percent) and a membrane displacement of 58 mm (± 5.2 percent).