Title page for ETD etd-01292008-183718

Type of Document

Dissertation

Author

He, Xingxi

Author's Email Address

xingxi@vt.edu

URN

etd-01292008-183718

Title

Monte Carlo simulation of ion transport of high strain ionomeric polymer transducers

Degree

PhD

Department

Mechanical Engineering

Advisory Committee

Advisor Name	Title
Leo, Donald	Committee Chair
Goulbourne, Nakhiah C.	Committee Member
Inman, Daniel J.	Committee Member
Paul, Mark R.	Committee Member
Vlachos, Pavlos P.	Committee Member
Weiland, Lisa	Committee Member

Keywords

ionic polymer transducer
morphology
Monte Carlo simulation
ion hopping model
Multiscale modeling

Date of Defense

2008-01-15

Availability

unrestricted

Abstract

Ionomeric polymer transducers exhibit electromechanical coupling capabilities. The transport of charge due to electric stimulus is the primary mechanism of actuation for a class of
polymeric active materials known as ionomeric polymer transducers (IPTs). The research
presented in this dissertation focuses on modeling the cation transport and cation steady
state distribution due to the actuation of an IPT.

Ion transport in the IPT depends on the morphology of the hydrated Nafion mem-
brane and the morphology of the metal electrodes. Recent experimental findings show that adding conducting powders at the polymer-conductor interface increases the displacement
output. However, it is difficult for a traditional continuum model based on transport theory to include morphology in the model. In this dissertation, a two-dimensional Monte Carlo
simulation of ion hopping has been developed to describe ion transport in materials that
have fixed and mobile charge similar to the structure of the ionic polymer transducer. In
the simulation, cations can hop around in a square lattice. A step voltage is applied be-
tween the electrodes of the IPT, causing the thermally-activated hopping between multiwell
energy structures. By sampling the ion transition time interval as a random variable, the system evolution is obtained.

Conducting powder spheres have been incorporated into the Monte Carlo simulation. Simulation results demonstrate that conducting powders increase the ion conductivity.
Successful implementation of parallel computation makes it possible for the simulation to include more powder spheres to find out the saturation percentage of conducting powders
for the ion conductivity. To compare simulation results with experimental data, a multiscale model has been developed to increase the scale of Monte Carlo simulation. Both transient responses and steady state responses show good agreement with experimental
measurements.

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