(217bg) Manipulating the Motion of Droplets On Stimuli-Responsive, Fiber-Filled Gels

Using dissipative particle dynamics (DPD), we design dual-responsive nanocomposites films, which encompass gels and fibers that are both stimuli-responsive. In response to variations in light or temperature, the gel can shrink and the embedded posts become exposed to the surrounding solution. The exposed posts can thereby be used to dynamically and controllably manipulate the motion of fluid-driven droplets on the surface of the film. The gel is constructed by crosslinking polymer chains in a coarse-grained manner. We probe the volume phase transition and swelling kinetics of the gels in explicit solvents. Our model is validated through qualitative comparisons with Flory-Huggins theory. In the simulations, a liquid droplet is introduced on top of the nanocomposite film and we determine how the coupling among hydrodynamic interactions, the elastic properties of the fibers and gel, and the external stimuli affect the motion of the drop along the surface. We exploit the distinctly different responses of the gel and the fibers to the external stimuli to further regulate the dynamic behavior of the system. With the introduction of light, we can remotely and non-invasively program the properties of this fiber-filled gel. Our findings provide fundamental insights into the dynamics of gel-based composites, as well as guidelines for designing re-programmable, multi-functional materials.