Measurement of forces and spring constants of microinstruments

Micromachines, including micro scanning tunneling microscope and high force (≈0.1 mN and higher) actuators, are examples of a new class of silicon-based microinstruments for atomic scale surface imaging and modification, as well as submicrometer scale material investigations. A large class of such microinstruments and sensors consist of actuators, such as interdigitated comb drives, that generate force, F, in the form F=βV2, where β is a constant and V is the applied voltage. Such actuators often move a large distance during actuation so that the restoring force, R, of the springs varies nonlinearly with x, i.e., the springs behave as hard springs, and R=K1x+K3x3+… (restoring force is similar for +ve and −ve x due to symmetry). β and Ki, i=1,3,…, of the micro-actuators usually differ from their design values due to processing nonuniformities. Hence, evaluation of these constants becomes necessary for each actuator, and is essential for the instruments that are employed to study materials’ behavior on a sm...

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