UC San Diego

Soft responsive materials can undergo significant changes in their properties in response to external stimuli such as temperature, mechanical force, light, pH, magnetic, electric fields, and chemical agents. The efforts of this dissertation are mainly focused on understanding and exploiting the chemistry, physics, mechanics, and dynamics of soft responsive materials to develop new pathways of programmable properties including shape morphing and optical signal. This dissertation encompasses the engineering techniques of soft responsive materials across the spectrum from non-living (i.e., synthetic) to living systems. In non-living systems, we used synthetic stimuli-responsive soft materials, such as hydrogels and elastomers, to explore how material characteristics can be integrated into novel structural designs through additive manufacturing. We also modeled these material systems using computational methods to further understand and predict their behaviors. Extrusion-based 3D printing (i.e., direct ink writing), one of the techniques of additive manufacturing, was employed to create complex structures with precise control over material compositions and local architectures. We discuss the rationale of the structure design, from microscopic to macroscopic, to enable the desired functionality by leveraging the structure-property relationships. In living systems, we have integrated our synthetic adhesive hydrogel with plants to introduce new functionalities such as programmable shape morphing, on-demand plant control, and precise cargo delivery. We examine the engineering requirements for synthetic polymers to interface with living systems like plants, focusing on mechanical, chemical, and biocompatible characteristics. We present a method for achieving strong, yet reversible, adhesion to various plant surfaces, utilizing the Schiff's base reaction to establish dynamic imine bonds. This strategy paves the way for advanced nutrient delivery systems for plants, wearable sensors for early disease detection, and novel human-plant interaction modalities.