Measuring and modeling electrostatic adhesion in micromachines

We measure deformations of electrostatically actuated cantilever beams adhered to a substrate and compare results to numerical simulations. Beams are peroxide treated and either supercritically dried or coated with octadecyltrichlorosilane (ODTS). In air with relative humidity (RH) of about 50%, measured deformations are consistent with numerical results when an effective insulator thickness of 14 nm is assumed. This value is a measure of the roughness of the substrate. Deformations are generally reversible for voltages up to 2 V. With RH of 75%, deformations of supercritically dried beams are dominated by capillary rather than electrostatic forces. The ODTS-coated beams exhibit less effect from the capillary forces, as expected for a hydrophobic coating.