Dual-Stimulus-Responsive Liquid Marbles with Programmable Motion on Liquid and Hydrogel Surfaces

Liquid marbles have attracted a significant amount of attention because of their dynamic programmable nature. In the present study, we propose the conceptualization and implementation of a novel dual-stimulus-responsive liquid marble (LM) platform actuated by near-infrared (NIR) light and magnetic fields and capable of exhibiting controllable locomotion behavior in response to changes in interfacial tension. The integration of external stimuli within a single liquid marble system has been achieved by means of two different micro- and nanoscale functional coating particles and a magnetically responsive core liquid. The liquid marble shell formed through the utilization of hydrophobic polypyrrole particles (SPP), which exhibit high photothermal energy in conjunction with hydrophobic magnetic nanoparticles (F-MNP), which provide magnetic responsiveness. In addition, ferrofluid (FF) has the capacity to respond to an applied magnetic field and is utilized as a core material. The resulting liquid marbles exhibited controllable locomotion under NIR irradiation, magnetic actuation, and combined stimuli through the utilization of near-infrared light-induced Marangoni flows and magnetic field-driven forces. In the presence of external stimuli, these systems generate asymmetric interfacial stress gradients at the liquid-air interface, resulting in the observed controllable locomotion. A systematic investigation was conducted to explore the impact of the particle type, magnetic field, and NIR exposure on the movement behavior of liquid marbles on water and polyacrylamide (PAM) hydrogel surfaces. This work demonstrates the potential of dual-stimulus-responsive liquid marbles as a programmable smart actuation system.