Creation of Topological Ultraslippery Surfaces for Droplet Motion Control.

Abstract

Droplet motion control on slippery liquid-infused porous surfaces (SLIPS) that mimics the peristome surface of <i>Nepenthes alata</i> has promising applications in the fields of energy, lab-on-a-chip device, <i>etc.</i>, yet is limited due to the difficulty in regulating its wettability. In this work, topologies with specific functions from natural creatures, for example, grooved structures of rice leaf and wedge-shaped structures of shore bird beak with droplet transporting capability were integrated with the SLIPS. Three-dimensional topological SLIPS was fabricated on metal substrates using laser milling followed by alkaline oxidation. Fabricated rice leaflike grooved nanotextured SLIPS can properly shape the droplet footprint to achieve a sliding resistance anisotropy of 109.8 μN, which is 27 times larger than that of a natural rice leaf and can therefore be used to efficiently and precisely transport droplets; wedge-shaped nanotextured SLIPS can confine the droplet footprint and squeeze droplet to produce a <i>Laplace</i> pressure gradient for continuous self-driven droplet transport. The created surfaces can manipulate droplets of acid, alkali, and salt solutions. The proposed concept is believed to have potential applications for condensing heat transfer and droplet-based lab-on-a-chip devices.