Mechanical and Civil Engineering Seminar

*Connection details for this online presentation will be posted when available.

Soft active materials, such as polymers, elastomers, and gels, are responsive to multiple stimuli, adaptable to and compatible with various environments, and form ideal candidates for human-machine interfaces. The multi-scale, multi-physics nonlinear interaction associated with these materials opens up not only new possibilities in application and development of emerging soft machines, but also interesting fundamental questions. In this talk, I will present a pathway from soft active materials towards soft machines through recent work on characterization, design, and functionalization of these materials, focusing on mechanics in a multi-disciplinary context. I will start with fatigue of hydrogels, i.e., failure in hydrogels under prolonged cyclic or static mechanical loads. Hydrogel fatigue lies at the interface of bonding chemistry, network topology, and dissipation mechanics, and forms a new lens to probe the molecular process and fracture under complex rheology. A design of flaw-insensitive hydrogel is then proposed to avoid fatigue crack growth through crack deflection. I will then utilize a synergy of chemistry, topology, and mechanics, and demonstrate the method to integrate hydrogels with other materials through strong adhesion at their interface. The design principle is capable of bonding various wet materials, in environments covering the full range of pH, without requiring special functional groups from the adherends. Finally, I will introduce a theoretical framework to study photomechanical coupling in actuation of liquid crystal elastomers under both light illumination and mechanical load. Two generalized actuation modes will be discussed, accompanied by formation of microscopic stripe domains and photomechanical phase transition