Extrusion 3D-Printing of Integrated Soft Materials for Ionotronic Applications

Abstract

Stretchable electronics is an emerging field responding to the demands of soft robotics and biological applications. Whereas the materials of traditional electronics are hard and rigid – like silicon and metals – stretchable materials are soft and compliant like rubber. Conventional stretchable electronics integrate the hard within the soft. Hydrogel-based ionic devices represent an alternative approach to stretchable electronics. Metallic conductors can be replaced with soft ionic conductors that are both highly stretchable and transparent. However, these devices require the integration of dissimilar materials, hydrophobic elastomers and hydrogels, into a single system—a process thus far achieved primarily via the combination of several different manufacturing techniques. The concurrent rise of additive manufacturing presents an opportunity to develop a new fabrication platform for hydrogel-based devices. This dissertation will delve into recent progress made in the 3D extrusion printing of these dissimilar soft materials for a range of engineering applications, the challenges that one encounters, and those that remain on the horizon. Chapter 1 reports a study of high ionic strength hydrogel materials for their unusual thermal, mechanical, and electrical properties. Chapter 2 presents an extrusion 3D-printing platform for the simultaneous fabrication of hydrogel and hydrophobic elastomer. Chapter 3 further characterizes the initial platform developed in a study of the adhesion characteristics of the hydrogel-elastomer interface over time. Chapter 4 adapts a new silane-based chemistry in order to fully integrate hydrogel and elastomer for extrusion 3D-printing.