Semester

Spring

Date of Graduation

2022

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Edward M. Sabolsky

Committee Co-Chair

Konstantinos A. Sierros

Committee Member

Konstantinos A. Sierros

Committee Member

Charter D. Stinespring

Committee Member

Bruce S. Kang

Committee Member

Ji Su

Abstract

Electroactive polymers (EAPs) continue to gain attention for their potential to offer unique and versatile solutions in the soft robotic and flexible electronic industries. Ionic Polymer-Metal Composites (IPMCs) are a class of ionic-type EAPs which can be configured as capacitor actuators with very low voltage requirements (≤ 5 V AC or DC). Their compact, portable, and lightweight properties, coupled with a biomimetic bending actuation response make them ideal for human-machine integrated technologies such as medical implants, active skins, and artificial muscles. The Nafion-based IPMC can be described as a layered composite capacitor containing an ionic polymer core, sandwiched between chemically plated electrodes comprising of a conductive medium. Although there are reported achievements utilizing IPMCs in actuator configurations, their hydration-related sensitivity inhibits practical application in industry and makes experimental research difficult. This research sought to overcome these challenges by applying a wide range of experimental analyses, combined with theoretical modeling comparisons, to quantitatively characterize practical and standout factors impacting the actuator’s feasibility. The specific objectives investigated in this work include: (1) modifications of experimental test arrangements for practical insight; (2) investigation of IPMC degree of saturation and exposure correlations in both liquid and vapor conditions, coupled with electrical monitoring; (3) consideration of electrical field bias intensity and application arrangements on actuation behavior; and, finally, (4) practical inspection of IPMC design features and investigation of coating and geometric modification solutions for biomimetic and biocompatible applications.

Investigations resulted in the development and validation of two testing configurations (contact-based and hydration-controlled) which provided reliable and repeatable testing. These systems included electrical and hydration control and monitoring which led to the identification of electrical tracking as a means to estimate IPMC performance. Additionally, optimized operation conditions were identified with special focus on the IPMC actuator’s performance variability. This work uncovered that the material’s inconsistency is a large factor inhibiting this technology from practical application. Electrical and actuation response analyses focused on the influence of the environment and voltage intensity on IPMC behavior changes with special emphasis on voltages surrounding reported electrolysis ranges unique to IPMCs. Lastly, a decision-making procedure was developed to optimize IPMC fabrication for soft-robotic biomimetic biocompatible solutions. This included emphasis on electrode deposition and patterns with quality analysis; IPMC hydrophobic coating solutions to inhibit solvent exchange; and modification of the geometric properties. All of this has culminated in a more pragmatic perspective on the potential of this technology and an identified course of action which could lead to the production of viable real-world application configurations which capitalize on the capabilities of these material arrangements.

Embargo Reason

Publication Pending

Comments

Submitted 4-27-2022 by 4 pm.

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