Active Release of Microobjects Using a MEMS Microgripper to Overcome Adhesion Forces

Due to force scaling laws, large adhesion forces at the microscale make rapid accurate release of microobjects a long-standing challenge in pick-place micromanipulation. This paper presents a new microelectromechanical systems (MEMS) microgripper integrated with a plunging mechanism to impact the microobject for it to gain sufficient momentum to overcome adhesion forces. The performance was experimentally quantified through the manipulation of 7.5-10.9-mu m borosilicate glass spheres in an ambient environment under an optical microscope. Experimental results demonstrate that this microgripper, for the first time, achieves a 100% successful release rate (based on 200 trials) and a release accuracy of 0.70 +/- 0.46 mu m. Experiments with conductive and nonconductive substrates also confirmed that the release process is not substrate dependent. Theoretical analyses were conducted to understand the release principle. Based on this paper, further scaling down the end structure of this microgripper will possibly provide an effective solution to the manipulation of submicrometer-sized objects. [2008-0304]