Decoupling skin from bulk demixing in polymer membranes via droplet-mediated interfacial transport

Membrane distillation is hindered by a persistent trade-off between vapor permeability and long-term wetting resistance, rooted in the tight coupling of surface skin consolidation with bulk demixing during conventional phase inversion. This work demonstrates that controlled deposition of low-inertia microdroplets onto the polymer dope surface prior to immersion establishes localized surface-tension gradients that drive Marangoni convection, effectively decoupling skin formation from bulk demixing through a kinetically programmable pathway. In LiCl-doped membranes, this intervention optimizes additive leaching and anti-scaling resilience, with the optimized membrane achieving 17.86 kg m −2 h −1 flux and 99.97% salt rejection. Remarkably, the same intervention applied to a pristine, additive-free system generates a fully interconnected, macrovoid-free architecture delivering 19.93 kg m −2 h −1 and 99.62% salt rejection, a ~ 1410% (1.32 kg m −2 h −1 to 19.93 kg m −2 h −1 ) flux enhancement over the control. These results establish droplet-mediated interfacial transport as a self-sufficient design principle, shifting fabrication from chemical modification to kinetically controlled decoupling of skin from bulk demixing.