Experiments indicate that the electrodes affect the charge dynamics, and therefore actuation of ionic polymermetal
composite (IPMC) via three different types of currents - electric potential induced ionic current, leakage
current, and electrochemical current if approximately higher than 2 V voltage is applied to a typical 200 μm
thick IPMC. The ionic current via charge accumulation near the electrodes is the direct cause of the osmotic
and electrostatic stresses in the polymer and therefore carries the major role in the actuation of IPMC. However,
the leakage and the electrochemical - electrolysis in case of water based IPMCs - currents do not affect the
actuation dynamics as directly but cause potential gradients on the electrodes. These in turn affect the ionic
current. A physics based finite element (FE) model was developed to incorporate the effect of the electrodes and
three different types of currents in the actuation calculations. The Poisson-Nernst-Planck system of equations is
used in the model to describe the ionic current and the Butler-Volmer relation is used to describe the electrolysis
current for different applied voltages and IPMC thicknesses. To validate the model, calculated tip deflection,
applied net current, and potential drop in case of various IPMC thicknesses and applied voltages are compared
to experimental data.
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