Simulation and experimental investigation of a novel electrostatic microgripper system

Microgrippers are amongst the preferred tools for microassembly applications and have drawn extensive attention of the researches on their mechanism and actuation principles. One of key parameters is efficiency of microgripping systems in handling more than one part at a time. Multi-part-gripping mechanism is one of the least investigated subjects in the published literature. In this paper, an electrostatic microgripping system using comb drive mechanism is designed with the capability of gripping two micro components simultaneously. S-type springs are utilized to amplify the displacement range of microgripper arms. The objects gripped with this microgripping system are diverse from biomedical (e.g. arrow shaped microshuttles); MEMS and microelectronic field with the dimensions from 145 to 100 mu m for the operating voltage of 20-80 V. A mathematical model with derived formulas is developed showing displacement of the tool versus applied voltage. Estimation of the performance of comb-drive is done through considering five capacitors all around a comb finger. The designed model predicts the displacement of the rotor more accurately compared to dominant method of calculating the equivalent capacity of only two lateral capacitors. Furthermore a multi-field simulation of the electrostatic comb finger of the comb drive is performed using finite element method. The FEA results show good agreement with the prediction obtained from analytical model. Microgripper function is enhanced through introducing a suspension system with optimum stiffness values. It helps the microgripper work under lower levels of actuating voltage. Finally, to verify analytical results, the microgripper is fabricated and the displacements are measured that compare well with analytical results and numerical simulation. (C) 2012 Elsevier B.V. All rights reserved.