  This paper presents results about fabrication and operation of electrostatic
actuators in liquids with various permittivities. In the static mode, we
provide experimental and theoretical demonstration that the pull-in effect can
be shifted beyond one third of the initial gap and even be eliminated when
electrostatic actuators are operated in liquids. This should benefit to
applications in microfluidics requiring either binary state actuation (e.g.
pumps, valves) or continuous displacements over the whole gap (e.g.
microtweezers). In dynamic mode, actuators like micro-cantilevers present a
great interest for Atomic Force Microscopy (AFM) in liquids. As this
application requires a good understanding of the cantilever resonance frequency
and Q-factor, an analytical modeling in liquid environment has been
established. The theoretically derived curves are validated by experimental
results using a nitride encapsulated cantilever with integrated electrostatic
actuation. Electrode potential screening and undesirable electrochemistry in
dielectric liquids are counteracted using AC-voltages. Both experimental and
theoretical results should prove useful in micro-cantilever design for AFM in
liquids.
