SYNTHESIS, DESIGN, AND FABRICATION OF LIGHT-EMITTING SOFT COMPOSITES AND STIMULI-RESPONSIVE SOFT MATERIALS FOR ROBOTIC APPLICATIONS

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Intrinsically soft materials and material composites possess several distinctive characteristics, such as self-assembly, mechanical compliance, and controllable deformability with large number of degree-of-freedom, which make them promising candidates for building soft machines and robots toward better human-machine interfaces. Some key challenges for creating these soft systems that can deliver desired behaviors are the development of soft materials with designed properties (e.g., mechanical, electrical, chemical, optical, etc.), as well as the systematic integration of these materials that incorporate diverse functionalities (e.g., actuation, sensing, displays, and control) based on rapid design tools and low-cost fabrication recipes. In this dissertation, I discuss three examples that actively combine practical chemical synthesis with bio-inspired design and advanced manufacturing methods (e.g., soft lithography and 3D printing) that lead to the convergence of task-specific devices and material properties. First, I present a stretchable light-emitting display and touch interface that is inspired by the adaptive visual camouflage and sensing of cephalopods. By embedding electroluminescent ZnS phosphors in silicone elastomer as light-emitting dielectrics and exploiting conductive LiCl hydrogel as electrodes, I pattern the pixels heterogeneously using photolithography and transfer printing. The fabricated device demonstrates high resolution dynamic coloration with capacitive touch sensing. Second, I present a protocol that synthesizes and aligns a photomechanical elastomer that exhibits artificial muscle-like actuations. Light-responsive azobenzene moieties are covalently attached to a polyurethane backbone via a two-part step-growth polymerization which yields a soft robotic gripper with tunable bending and autonomous self-healing. Last, I introduce an additive manufacturing method, digital light processing to automatically shear align and crosslink thermomechanical liquid crystal elastomers for stronger artificial muscles. The programmable shape morphing and higher energy density enable faster-acting soft actuators that can perform reversible grasping, untethered maneuvering, and weight lifting. Thermally induced optical transition in this material also reveals a self-sensing mechanism for potential feedback in robotic systems.

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129 pages
Supplemental file(s) description: Video 4.4, Video 4.5 (speed 4x), Video 4.3, Video 4.2 (speed 4x), Video 4.1.
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2020-08
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Shepherd, Robert F.
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Wiesner, Uli B.
Estroff, Lara A.
Degree Discipline
Materials Science and Engineering
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Ph. D., Materials Science and Engineering
Degree Level
Doctor of Philosophy
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dissertation or thesis
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