Electro-thermo-dynamic performance of a microgripping system

Microgripping systems incorporate miniature end grasping tools to manipulate micro-sized objects such as tiny mechanical parts, electrical components, biological cells, and bacterium. A thorough understanding of the system´s dynamic behaviour, including the gripper force and tip displacement, is essential for successfully handling these micro-objects. In this paper, the electro-thermo-dynamic performance characteristics of a proposed microgripper are described. The system has a monolithic design which consists of a combination of an in-plane electro-thermally driven microactuator and a compliant mechanism. The kinematics of the microgripper is introduced and several prototypes are fabricated from 25μm thick nickel foil. The dynamic and electro-thermal characteristics of the system are analyzed with respect to step responses, actuation/tweezing displacements, applied current/power, actual resistance and overall average temperature. Experiments demonstrate that the fabricated microgripper prototype with design parameters of α₀ = 30°, β₀ = 40°, h₀ = 0μm, and ℓ = 1.2 mm achieves tweezing displacement of 11.84μm (tweezing gap of 23.68μm) for an applied voltage and current of 1.41V and 0.15A, respectively. This experimental observation agrees with the predicted displacements from the kinematic model of 11.66 μm. These preliminary results lay a foundation for developing micro grasping end-effectors for microrobotic and microassembly applications.