Ionic-Polymer-Metal Composites (IPMCs) are a subset of Electroactive Polymers (EAPs), which are an actively-researched class of electromechanical actuators. IPMCs are similar in function to piezoelectric actuators, however require substantially lower input voltage, requiring as little as 1V to actuate, and with a very high maximum no-load strain of over 300%. IPMCs can be built from biocompatible materials, and do not require the use of any permanent magnets, making them suitable for medical applications, or for use in environments subject to strong or fluctuating magnetic fields. IPMCs are additionally soft and flexible, and are suitable for wet environments, further improving their biocompatibility. This, along with their other properties, makes IPMCs ideal for small robotic applications and for biomimetics. However, IPMCs typically exert, maximally, a small fraction of the total force which can be provided by piezoelectric actuators or other types of EAPs. This study expands on previous efforts to improve IPMC performance by proposing a method for optimizing desired aspects of IPMC performance with respect to any number of input parameters by applying the method of Gradient Descent utilizing the Backtracking Line Search. This method is outlined generally and demonstrated here, showing the process used through most of one iteration to optimize for IPMC blocking force with respect to changes in the amount of platinum used during the primary and secondary plating procedures. The incomplete backtracking line search did not lead to improved performance over the initial results (2.22 [mN] vs 2.37 [mN]), with an IPMC made during the initial gradient estimation exhibiting the greatest blocking force with 25% improvement (2.96 [mN]) over this initial guess, indicating that subsequent iterations of the backtracking line search could lead to further improvements in IPMC blocking force. It was additionally found that the sanding process in particular, as a process excluded wholesale from the gradient descent search used, had a relatively large impact on the IPMC blocking force, and thus should be controlled more carefully when continuing or extending the method carried out here.
Library of Congress Subject Headings
Polymers--Electric properties; Actuators--Testing; Electromechanical devices
Mechanical Engineering (MS)
Department, Program, or Center
Mechanical Engineering (KGCOE)
Varma, Vaughn, "A Technique for the Optimization of Actuation Characteristics of Ionic Polymer-Metal Composites" (2018). Thesis. Rochester Institute of Technology. Accessed from
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