Devices for fatigue testing of electroplated nickel (MEMS)

In-situ fatigue test devices with integrated electrostatic actuator were fabricated in electroplated nanocrystalline nickel (nano-nickel). The devices feature in-plane approximately pure bending with fixed displacement of the test specimen of the dimensions: widths from 2/spl mu/m to 3.7/spl mu/m, a height of 7/spl mu/m and an effective length from 4/spl mu/m to 27/spl mu/m. Maximum stresses of the test beam were calculated to be 500MPa to 2100MPa by use of FEM tools. The test results indicate very promising fatigue properties of nano-nickel, as none of the test devices have shown fatigue failure or even initiation of cracks after 10/sup 8/ cycles. The combination of high strength and toughness, which is known for nanocrystalline materials, together with very small test specimens and low surface roughness could be the explanation for the good fatigue properties.