Advanced Manufacturing of Microengineered Ionic Polymer Metal Composites for Enhanced Sensing Capabilities

Abstract

Ionic Polymer Metal Composites (IPMCs) are ionic electroactive polymers thatexhibit active and passive actuation, sensing, and energy harvesting capabilities. The composite is comprised of an ionic exchange membrane that is sandwiched between two noble metal electrodes and infused with a polar solvent. IPMCs have been primarily studied for their potential as artificial muscles and biomimetic soft robotic actuators, while IPMC sensors have been relatively less examined. In sensing applications, applied mechanical deformation initiates a redistribution of charge within the material, which produces measurable electrical output. In this thesis, two advanced additive manufacturing-based approaches for the fabrication of engineered Ionic Polymer Metal Composite (eIPMC) sensors are investigated. The development of an engineered polymer-metal electrode interface with 3D inkjet-printed and stencil-printed microfeatures is examined for the creation of eIPMC compression sensors with enhanced sensing capabilities.The first chapter provides a thorough review of the background of IPMC sensortechnology and the connection between the material’s structure, fabrication, and sensing performance. IPMC compression sensing is discussed by examining two common theories used to describe the materials underlying compression sensing mechanism. Next, the conventional and advanced manufacturing methods are reviewed to illuminate the motivation of this current work. It is proposed that advancements in manufacturing techniques can ultimately address the current limitations of IPMC sensor application and guide future modeling and research endeavors. IPMC sensor applications and challenges are also thoroughly explored.The second chapter presents two novel approaches for the creation of eIPMCsensors via two additive manufacturing methods: (1) inkjet-printing and (2) stencil-printing. In this work, we tailor the morphology of the polymer-electrode interface with additively manufactured polymer microfeatures to produce inhomogeneous strain upon application of external compression. The goal is to improve the material’s multiphysics sensing properties and produce engineered IPMC (eIPMC) strain sensors with superior sensing performance. Experiments were conducted to compare the sensing behavior between standard (control) IPMC sensors fabricated from commercially available Nafion polymer sheet stock and eIPMC compression sensors. It was found that eIPMC sensors generally outperformed standard IPMC sensors.