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Dynamic Flow Control and Self-Assembly on Bioinspired Slippery Surfaces

Final Report Summary - DYNASLIPS (Dynamic Flow Control and Self-Assembly on Bioinspired Slippery Surfaces)

Slippery Liquid-Infused Porous Surfaces (SLIPS) are surfaces with exceptional liquid-repellent, anti-icing and antibiofouling properties. Inspired by pitcher plants (Nepenthes), they are based on micro/nanoporous and/or texturized solids that are infused with lubricating liquids (Nature 477, 443-447, 2011). They are solid-liquid hybrid surfaces, wherein the porous solid withholds the lubricating liquid by means of physical and chemical forces. In this Marie Curie project, we investigate different dynamic processes on SLIPS (hence the acronym “DynaSLIPS”). The objectives include realization of flow control of droplets, understanding of dissipative processes on moving droplets, and self-assembly of droplets and colloidal objects on SLIPS.

We have developed new research equipment that allow us to simultaneously probe friction (with a cantilever sensor) and stability of the lubricant layer (with optical imaging and interference effect) on SLIPS. We have applied these tools to a wide range of SLIPS types where we have systematically altered the type of the nano/microstructure (e.g. size, shape, spacing of the nano/microscopic features), lubricant chemistry, and composition of the sliding droplets. As a main result, we have revealed how the lubricant layer stability affects dissipation on SLIPS (Nature Physics 13, 1020-1025, 2017). We have also investigated self-assembly of both microscopic and macroscopic objects on SLIPS. Results show that self-assembly of both colloidal matter and droplets on SLIPS can be controlled with physical forces.

As a result from this project, we have a good understanding of friction and dissipation mechanisms on SLIPS and how those can be minimized, with potential socio-economic impact. The new insights to dissipation will enable rational design of SLIPS for real-world applications related to preventing wetting and contamination of surfaces. We have also developed better tools for controlling droplet flow on SLIPS with magnetic fields. These tools may find use in modern digital microfluidics and droplet-based analysis techniques. We also have improved understanding of behavior of colloidal matter and living micro-organisms on SLIPS. These results will have direct implications on utilization of SLIPS as slippery and antibiofouling coatings that are crucially needed in many fields of engineering ranging from biomedical devices to transport industries.