Light and Temperature Dual-Responsive Liquid Marbles Stabilized with Azobenzene-Modified Poly(N-Isopropyl Acrylamide).

Abstract

Liquid marbles have garnered significant attention as versatile platforms for microreactor technologies, owing to their ease of handling and programmable fluidic operations, particularly through stimuli-triggered coalescence behavior that enables spatiotemporally controlled reagent mixing. However, current systems often rely on operationally complex methods. Meanwhile, the capability for multi-stimulus responsiveness can expand the application range of liquid marbles and enhance their adaptability to complex environments. This study presents a light- and temperature-responsive liquid marble by encapsulating a water droplet with azobenzene-modified poly(N-isopropyl acrylamide) (Azo-PNIPAM). The addition of hydrophobic groups enables the precise regulation of the lower critical solution temperature (LCST) of Azo-PNIPAM, thereby developing a strategy for accurately controlling the stability of liquid marbles and addressing the gap in stability modulation of liquid marbles using two classic stimulus-responsive components, PNIPAM and azobenzene. The liquid marbles can disintegrate under UV light irradiation or at low temperature due to the increased hydrophilicity of Azo-PNIPAM. Moreover, by adjusting the duration of UV light exposure, arrested coalescence between liquid marbles is achieved, which provides possibilities for smart droplet-based microreactors and various liquid manipulations.