Brian R. Solomon

Drag reduction using lubricant-impregnated surfaces in viscous laminar flow.

Lubricant-impregnated surfaces (LIS), where micro/nanotextured surfaces are impregnated with lubricating liquids, have received significant attention for their robust, superslippery properties. In this study, we systematically demonstrate the potential for LIS to reduce drag in laminar flows. We present a scaling model that incorporates the viscosity of the lubricant and elucidates the dependence of drag reduction on the ratio of the viscosity of the working fluid to that of the lubricant. We experimentally validate this dependence in a cone and plate rheometer and demonstrate a drag reduction of 16% and slip length of 18 μm in the case where the ratio of working fluid viscosity to lubricant viscosity is 260.

Separating Oil-Water Nanoemulsions using Flux-Enhanced Hierarchical Membranes

Membranes that separate oil-water mixtures based on contrasting wetting properties have recently received significant attention. Separation of nanoemulsions, i.e. oil-water mixtures containing sub-micron droplets, still remains a key challenge. Tradeoffs between geometric constraints, high breakthrough pressure for selectivity, high flux, and mechanical durability make it challenging to design effective membranes. In this paper, we fabricate a hierarchical membrane by the phase inversion process that consists of a nanoporous separation skin layer supported by an integrated microporous layer. We demonstrate the separation of water-in-oil emulsions well below 1 μm in size. In addition, we tune the parameters of the hierarchical membrane fabrication to control the skin layer thickness and increase the total flux by a factor of four. These simple yet robust hierarchical membranes with engineered wetting characteristics show promise for large-scale, efficient separation systems.

CHAPTER 10: Lubricant-Impregnated Surfaces

Lubricant-impregnated surfaces comprising a porous or textured solid and a liquid lubricant give rise to many novel properties. In this chapter, we review how to achieve a stable lubricant-impregnated surface and discuss its basic features including the wetting ridge and lubricant cloak that are relevant to most implementations. Next, applications of lubricant-impregnated surfaces are detailed including condensation, anti-icing, anti-fouling, fluid mobility, optics, and active surfaces. In each application, the design of a lubricant-impregnated surface has particularly relevant criteria, and both the achievements and current shortcomings of this technology are discussed.