  Flow transport in confined spaces is ubiquitous in technological processes,
ranging from separation and purification of pharmaceutical ingredients by
microporous membranes and drug delivery in biomedical treatment to chemical and
biomass conversion in catalyst-packed reactors and carbon dioxide
sequestration. In this work, we suggest a distinct pathway for enhanced liquid
transport in a confined space via self-propelling microdroplets. These
microdroplets can form spontaneously from localized liquid-liquid phase
separation as a ternary mixture is diluted by a diffusing poor solvent. High
speed images reveal how the microdroplets grow, break up and propel rapidly
along the solid surface, with a maximal velocity up to ~160 um/s, in response
to a sharp concentration gradient resulting from phase separation. The
microdroplet self-propulsion induces a replenishing flow between the walls of
the confined space towards the location of phase separation, which in turn
drives the mixture out of equilibrium and leads to a repeating cascade of
events. Our findings on the complex and rich phenomena of self-propelling
droplets suggest an effective approach to enhanced flow motion of
multicomponent liquid mixtures within confined spaces for time effective
separation and smart transport processes.
