This paper presents the use of a monolithic, force-feedback MEMS (microelectomechanical systems) microgripper for characterizing both elastic and viscoelastic properties of highly deformable hydrogel microcapsules (15–25µm) at wet state during micromanipulation. The single-chip microgripper integrates an electrothermal microactuator and two capacitive force sensors, one for contact detection (force resolution: 38.5nN) and the other for gripping force measurements (force resolution: 19.9nN). Through nanoNewton force measurements, closed-loop force control, and visual tracking, the system quantified Young's modulus values and viscoelastic parameters of alginate microcapsules, demonstrating an easy-to-operate, accurate compression testing technique for characterizing soft, micrometer-sized biomaterials.

This paper presents the first demonstration of force-controlled micrograsping at the microNewton force level. The system manipulates highly deformable biomaterials (hydrogel microcapsules and biological cells) in an aqueous environment using a MEMS-based microgripper with integrated force feedback along two axes. The microgripper integrates an electrothermal V-beam microactuator and two capacitive force sensors, one for contact detection (force resolution: 38.5 nN) and the other for gripping force measurements (force resolution: 19.9 nN). The MEMS-based microgripper and the force control system experimentally demonstrate the capability of rapid contact detection and reliable force-controlled micrograsping to accommodate variations in sizes and mechanical properties of objects with a high reproducibility. Cell viability testing validated that the temperature at gripping arm tips does not exceed 50degC.

This paper presents a new design of a two-axis MEMS (microelectromechanical systems) capacitive force sensor with strict linearity and a new sensor calibration method for micro-sensors. Precise calibration of multi-axis micro force sensors is difficult for several reasons, including the need to apply many known force vectors at precise orientations at the micro force scale, and the risk of damaging the small, fragile MEMS device. In this paper the shape from motion method is introduced for micro force sensors resulting in a rapid and effective calibration technique. Structural-electrostatic coupled field simulations are conducted in order to optimize the sensor design, which is calibrated with the shape from motion method as well as the least squares method for comparison purposes. Calibration results demonstrate that the shape from motion method is an effective, practical, and accurate method for calibrating multiaxis micro force sensors