Design, analysis, and control of a MEMS micro-gripper

Microelectromechanical systems (MEMS) are a key element contributing to significant developments in modern science and technologies. They offer low-cost solutions to miniaturize numerous devices. An increasing number of MEMS applications in biological research and micro industrial applications lead to noticeable demands for reliable micromanipulating tools. In this thesis, the design of such manipulators is explored via a novel MEMS micro-gripper integrated with electrothermal sensor and a novel SOI MEMS rotary micro-gripper. The presented MEMS based micro-grippers are fabricated and designed using a Silicon-On-Insulator (SOI) MEMS process to perform micromanipulation tasks in free air and in solution. A novel aspect of the first micro-gripper design presented in this thesis is the integration of innovative electrothermal displacement sensor, with a small footprint into the micro-gripper. The integrated electrothermal sensor demonstrates a linear characteristic between the measured position and the sensor output voltage, a wide sensing range (dynamic range), and a sufficient sensing bandwidth. The novelty and significance of the second micro-gripper design are due to its rotary actuation design and the implementation of a null-displacement feedback control force sensing technique where this sensing technique eliminates the dependence of the force sensor on the mechanical deformation of suspension system. Furthermore, the force calibration technique reported in this thesis is based on experimental calibration using voltage as an intermediate parameter to directly measure capacitance and angular displacement. As a result, no external device is needed for force sensor calibration. Finally, the thesis is concluded by demonstrating the feasibility of the devices and the implemented control methods through a set of practical applications such as force controlled pick-and-place operations on soft cells (Lilium pollen) and micro glass beads.