UC San Diego

Actuating devices traditionally rely on rigid components such as links and gears, posing challenges in handling delicate objects and operating in unstructured environments. Advancements in smart materials, particularly stimuli-responsive polymers, offer promising alternatives due to their compliance and controlled mechanical responses to external stimuli.Researchers have made significant progress in exploring stimuli-responsive polymers for actuating devices. These polymers can deform and generate various motions, enabling dynamic functionalities across diverse application areas including robotics, responsive systems, and health care. However, existing materials often present limitations such as high voltage requirements, specific working environments, or slow actuation speeds.

In this dissertation, we first proposed magnetic-responsive vitrimers for soft robotics. These vitrimers incorporate magnetic particles into polymer matrices, enabling controlled deformations and movements in response to magnetic fields. The exchange reaction activity of the dynamic covalent bonds within the vitrimers allows for drastic reconfiguration and self-healing property. Detailed investigations and experimentation were conducted to demonstrate the feasibility and effectiveness of these vitrimers for soft robotic applications. Secondly, we developed a liquid crystal elastomers-based thermal modulator. The thermal modulators can efficiently alternate between "low thermal resistance" and "high thermal resistance" states in reaction to changes in environmental temperature. The reversible transition induced by the nematic-isotropic phase transition of LCEs enables dynamic adaptation of thermal properties, offering potential applications in energy-efficient building materials and wearable technology necessitating active temperature regulation. Lastly, we studied the application of LCEs for both static and dynamic compression therapy. For static compression stocking, we developed a polydomain LCE with incorporated PEGDA, exhibiting stress plateau and negligible hysteresis. The LCE-based static stocking accommodates stocking application errors, various limb sizes, and reduces pressure drop due to leg deswelling. Monodomain LCE was introduced for dynamic compression stocking due to its reversible thermal actuation. The LCE-based dynamic stocking demonstrates intermittent pressure cycles from 20 to 60 mmHg with pressure profile programmability. We further fabricated an untethered and wearable compression device with a Power, Control, Sensing module and batteries, supporting continuous use up to four hours on a single battery charge.

In summary, this dissertation explores the design, fabrication, and characterization of actuating devices using magnetic-responsive vitrimers and thermal-responsive LCEs. Through comprehensive experimentation and analysis, we demonstrate the versatility and effectiveness of these materials for a range of applications, including soft robotics, thermal management, and compression therapy. We hope the our material-based design concept of actuating devices can contribute to various fields, from healthcare to wearable technology.