Transient Solubility Gradients Mediate Oversaturation during Solvent Exchange

Solvent exchange facilitates high-density nucleation of sessile nanodroplets or nanobubbles by successively wetting a surface with two solvents contrasting solubility respect to target species. Yet the key physical mechanisms underlying its efficacy have yet be theoretically explained. We develop minimal model for solvent exchange, prototypical example water and ethanol as nitrogen Our calculations show that is mediated transient gradients dominate over intrinsic concentration gradient in incipient moments after exchange. Solubility advect toward substrate during ethanol-water but away from it water-ethanol consistent directionality observed experiments.