The recently developed microgripper driven by a flexible, electrostatic comb drive has been shown to seize micron-sized objects. However, the comb drive utilized by this microgripper is highly inefficient in developing gripping force and is designed with elementary, straight teeth. Because of the local tooth rotation as a result of flexure of the gripper beams during operation, the use of straight comb teeth limits the gripping range and gripping force of the microgripper.
A flexible comb drive with curved teeth and tooth length and pitch that vary as a function of position along the gripper has been designed for the electrostatic microgripper. The design was based on 2-D electrostatic and mechanical models and were evaluated on the criteria of maximum gripper tip motion range and maximum object gripping force. Constraints on the comb teeth width, comb drive gap size, microgripper beam lengths, and comb teeth lengths were imposed to isolate the design variables to the teeth curvatures, lengths, and pitch. Designs were also restricted to actuation through flexible single comb drives as part of the cantilevered gripper arms.
The proposed 2 pm gap size microgripper design has an estimated motion range of 8 pm and an estimated maximum gripping force of over 47 nanoNewtons for a driving potential of 20 V. This is an improvement over existing designs of 83% in range and 88% in force.