UC Irvine

In nature, living systems operate far from equilibrium by consuming and dissipating energy to perform vital processes. Chapter 1 will introduce the background, history, and field of nonequilibrium systems. Biological systems use chemically derived energy to power out-of-equilibrium processes to generate complex macroscopic motion by dissipating energy at the molecular scale. In contrast, it remains a major challenge to create synthetic out-of-equilibrium systems that operate on the macroscopic scale.

In Chapter 2 we report a chemically fueled out-of-equilibrium system that can perform macroscopic actuation and do work by lifting objects. We achieve this by driving a lower critical solution temperature (LCST) transition of poly(N-isopropylacrylamide) (pNIPAAm) hydrogels with heat generated by a copper-catalyzed azide-alkyne cycloaddition (CuAAc) reaction. Upon completion of reaction, heat dissipates to the environment, and the system returns to equilibrium completing one cycle of out-of-equilibrium behavior, which can be repeated multiple cycles by adding new chemical fuels.

In Chapter 3 the groundwork from Chapter 2 is employed in efforts to achieve a self-regulating device. We set out to attach a copper catalyst in and LCST hydrogel in order to modulate reaction rate using the change in diffusion of the chemical fuels to the active catalytic sites. Efforts to achieve self-regulation of an exothermic reaction in a 3-dimensional material via autonomously oscillating catalytic hydrogels is described.

In Chapter 4, we report the design, synthesis and characterization of self-healing magnetic nanocomposites prepared from readily available commodity monomers. These multi-functional materials demonstrate robust mechanical properties, with a Young's modulus of 70 MPa and over 500% extensibility. The magnetic nanocomposites also show self-healing ability, achieving 46% recovery of extensibility in 5 hours in ambient conditions while retaining high magnetic actuation with a commodity magnet.