Development of a novel SEM microgripper

Although there are a number of different microgrippers that have been produced for use in SEM, most of these are made using expensive and time consuming microfabrication techniques such as lithography. In this work a novel type of microgripper has been developed that avoids lithography. Instead, the end-effecters of the gripper are made from a single piece of tungsten wire which is electrochemically thinned and then cut in two with a focused ion beam. Alignment of the two end-effecters is not an issue since they both come from the same wire, so the whole gripper is straightforward and quick to produce and it is possible to shape the end-effecters as desired. Independent electrical connections to each of the end-effecters allow them to be grounded to prevent charging in the SEM beam and give the option of applying a voltage across an object that is picked up. Furthermore, unlike lithographically produced grippers, if the end-effecters become too dirty or damaged it is possible to mount a new piece of tungsten wire and form new end-effecters without having to throw away the whole system. Actuation of the gripper is accomplished using a trimorph bender actuator giving very good resolution (typically ∼170nm/V) and a maximum possible span range of over 20μm. The gripper has been successfully demonstrated in picking up and placing copper microspheres in-situ in the SEM.