Thermoresponsive Hydrogel Microcapsules with Phase Separation-Induced Mechanical Toughening and Programmable Release

This work introduces phase separation-driven thermoresponsive hydrogel microcapsules fabricated via triple-emulsion microfluidics using poly(acrylic acid) (PAAc) ionically crosslinked with calcium acetate (CaAc). Thermal phase separation within the PAAc/CaAc shell induces a reversible polymer-dense state, simultaneously achieving mechanical toughening and dynamic control of molecular permeability. The phase transition occurs at ~58 °C, leading to a 55-fold increase in compressive modulus (from ~0.15 MPa to ~8.3 MPa) and a drastic decrease in molecular cut-off from 29 nm to 1.6 nm. The system enables reversible, temperature-triggered encapsulation and release of molecules, with programmable release kinetics tunable by high-temperature incubation time. These thermoresponsive microcapsules offer a robust platform for on-demand drug release, bioreactors, and soft robotic systems.