MEMS device for bending test: measurements of fatigue and creep of electroplated nickel

In situ bending test devices with integrated electrostatic actuator were fabricated in electroplated nanocrystalline nickel. The device features approximately pure in-plane bending of the test beam. The excitation of the test beam has fixed displacement amplitude as the actuation electrodes are operated to pull-in. The device was fabricated with different lengths of the test beam ranging from 7 to 30 mum. Maximum stresses in the test beams were calculated to be ranging from 470 to 2100 MPa using finite element methods (FEM). Life tests were performed, where the development of the pull-in voltages was monitored. The test results indicate good fatigue properties of nanocrystalline nickel. The results also indicate considerable creep activity at room temperature. A combination of high strength and toughness, which is known for nanocrystalline materials, could be the explanation for the good fatigue properties. (C) 2003 Elsevier Science B.V. All rights reserved.