The swelling and shrinking of spherical thermo-responsive hydrogels

Thermo-responsive hydrogels are a promising material for creating controllable actuators use in micro-scale devices, since they expand and contract significantly (absorbing or expelling fluid) response to relatively small temperature changes. Understanding such systems can be difficult because of the spatially- temporally-varying properties gel, complex relationships between fluid dynamics, elastic deformation gel chemical interaction polymer fluid. We address this using poro-elastic model, considering dynamics thermo-responsive spherical hydrogel after sudden change that should result substantial swelling shrinking. focus on two model examples, with equilibrium parameters extracted from data literature. find range qualitatively different behaviours when shrinking, including cases where shrinking happen smoothly edge, other situations which formation an inwards-travelling front separates core shell markedly degrees swelling. then characterise each these scenarios is expected occur. An approximate analytical form developed, levels constant porosity, well-approximates numerical solutions. This system evolved forward time, simpler solve than full numerics, allowing more efficient predictions made, as deciding dosing strategies drug-laden hydrogels.