| dc.description.abstract | The pressure between two parallel planar surfaces at equal electric potentials is derived
using the modified Poisson-Boltzmann (MPB) equation to account for finite ion size.
The effects of finite ion size are presented for a z:z symmetric electrolyte and compared
with the pressure derived by the classical Poisson-Boltzmann (PB) equation. The
pressures predicted by the two models differ more as the bulk ion concentration, surface
potential, and ion size increase. The ratio of the pressures predicted by the two models is
presented by varying the ion concentration, surface potential, ion size and distance of
separation. The ratio of pressures is relatively independent of the distance of separation
between the two surfaces.
An elastic beam suspended horizontally over a substrate in liquid electrolyte is
subjected to electric, osmotic, and van der Waals forces. The continuous beam structure,
not a discrete spring, which is governed by four nondimensional parameters, is solved
using the finite element method. The effects of ion concentration and electric potentials
to the pull-in instability are especially focused by parametric studies with a carbon nanotube cantilever beam. The pull-in voltage of a double-wall carbon nanotube
suspended over a graphite substrate in liquid can be less than or greater than the pull-in
voltage in air, depending on the bulk ion concentration. The critical separation between
the double-walled carbon nanotube (DWCNT) and the substrate increases with the bulk
ion concentration. However, for a given bulk ion concentration, the critical separation is
independent of the electric potentials. Furthermore, the critical separation is
approximately equal in liquid and air.
Stiction, the most common failure mode of the cantilever-based devices, is
studied in a liquid environment, including elastic energy, electrochemical work done,
van der Waals work done and surface adhesion energy. We extend the classical energy
method of the beam peeling for micro-electro-mechanical systems (MEMS) in the air to
an energy method for nano-electro-mechanical systems (NEMS) in liquid electrolyte.
We demonstrate a useful numerical processing method to find the parameters to free the
stiction of the beams and to obtain the detachment length of the beams. | en |
