Investigation of slippery behaviour of lubricating fluid coated smooth hydrophilic surfaces

TL;DR

This paper presents a simple method to create stable, slippery, silicone oil coated hydrophilic surfaces that become hydrophobic after annealing, demonstrating excellent water repellency and low hysteresis, with some limitations in oil stability.

Contribution

The study introduces a novel fabrication process for stable slippery surfaces by annealing silicone oil coated hydrophilic silicon, enhancing water repellency and slipperiness.

Findings

Annealed silicone oil coated surfaces exhibit hydrophobicity and low contact angle hysteresis.

The surfaces show excellent water repellency and slippery behavior.

Oil stability is limited against drops flow due to cloaking effects.

Abstract

In the recent years many research groups have studied slippery properties on lubricating fluid infused rough surfaces using hydrophobic substrates. These surfaces show excellent slippery behaviour for water and other liquids. Here we demonstrate a simple method to fabricate stable slippery surfaces based on silicone oil coated hydrophilic samples. At room temperature, as prepared samples exhibit non-slippery behaviour due to sinking of water drops inside silicone oil layer because of inherently hydrophilic silicon substrate. Subsequent annealing at higher temperatures provides covalent bonding of silicone molecules at silicon surface making the surface hydrophobic which was confirmed by lubricant wash tests. So the silicone oil coated annealed samples show excellent water repellency, very low contact angle hysteresis and very good slippery behavior. But these surfaces show poor oil stability against drops flow due to cloaking of the oil around water drops which can be prevented by using drops of larger volume or continuous flow of water.