Designing Polymer Hydrogels for Extrusion-Based Additive Manufacturing

Abstract

Additive manufacturing (AM) technologies are expanding the boundaries of materials science and providing an exciting forum for interdisciplinary research. The ability to fabricate arbitrarily complex objects has made AM technologies indispensable in personalized healthcare, soft electronics, and renewable energy. At the intersection of AM technologies and materials chemistry are stimuli-responsive polymers, which change their chemical and physical properties in response to specific environmental cues. Stimuli-responsive polymer hydrogels, in particular, are seeing significant interest in extrusion-based AM for the fabrication of bespoke medical implants and tissue engineering. The responsiveness of these “smart” hydrogels makes them suitable for AM and provides functionality to the additively manufactured objects. The type of stimulus response, mechanical properties, and functionality of these hydrogels can be regulated through chemical transformations or incorporation of additives. This dissertation describes two fundamentally different approaches to formulating polymer hydrogels for extrusion-based AM. Chapter 1 provides a thorough introduction to AM and stimuli-responsive hydrogels, with emphasis on hydrogels that respond to changes in temperature and shear pressure. Chapter 2 and Chapter 3 describe chemical transformations to the end groups of synthetic block copolymers to afford changes in hydrogel temperature response, mechanical characteristics, and morphology. By contrast, Chapter 4 reports the collaborative development of a 3D-printable bioink based on cardiac decellularized extracellular matrix (cdECM). While Chapter 2 and Chapter 3 deal with molecular-level changes to wholly synthetic polymer systems, Chapter 4 deals with biopolymers derived from porcine cardiac cells that are combined with synthetic additives. The two approaches offer contrasting strategies for the design of polymer hydrogels for AM.