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Articles
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"A continuum approach to
electrorheology"by Shkel YM,
Klingenberg DJ,
J. of Rheology 43: (5) 1307-1322, 1999
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An equilibrium thermodynamic approach is employed to
derive a continuum-level expression for the electric field-induced stress in
uniaxial anisotropic materials. Although this model is developed
specifically to describe electrorheological and electrostrictive behavior of
suspensions, it also applies to other uniaxial materials such as nonpolar
nematic liquid crystals, biaxially oriented polymer films, and paper. This
model introduces new electrostriction coefficients, which are material
parameters that describe the strain dependence of the dielectric tensor as
well as the field-induced stresses. An experimental technique for measuring
the electrostriction parameters is outlined. An idealized microscopic model
is presented to illustrate the relationships between microscopic parameters
and the macroscopic electrostriction coefficients. The model is used to
determine the stresses in common applications; predictions from the
continuum approach agree with direct calculations from a microscopic
approach of the normal stress and static shear modulus of electrorheological
suspensions.
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"Electrostriction Enhancement of A Solid State Capacitive
Sensor"
by
Yuri Shkel & Nicola J. Ferrier
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We present a novel design of a solid state capacitive sensor
that incorporates an elastic dielectric material between the electrodes. Variation in the dielectric constant
of the material between electrodes under deformation improves sensitivity to
displacements. This construction affords a dynamic response of the sensor based on
properties of the material (rather than properties of the electrodes). In addition, the
construction is simple to manufacture. We present experimental comparisons of our sensor
with standard air-gap capacitive sensors. The application of this sensor to tactile
sensing is discussed.
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