Ultimate Stable Underwater Superhydrophobic State

Abstract

Underwater metastability hinders the durable application of superhydrophobic surfaces. In this work, through thermodynamic analysis, we theoretically demonstrate the existence of an ultimate stable state on underwater superhydrophobic surfaces. Such a state is achieved by the synergy of mechanical balance and chemical diffusion equilibrium across the entrapped liquid-air interfaces. By using confocal microscopy, we in situ examine the ultimate stable states on structured hydrophobic surfaces patterned with cylindrical micropores in different pressure and flow conditions. The equilibrium morphology of the meniscus is tuned by the dissolved gas saturation degree within a critical range at a given liquid pressure. Moreover, with fresh lotus leaves, we prove that the ultimate stable state can also be realized on randomly rough superhydrophobic surfaces. The finding here paves the way for applying superhydrophobic surfaces in environments with different liquid pressure and flow conditions.

A variational level set methodology without reinitialization for the prediction of equilibrium interfaces over arbitrary solid surfaces

“…The paper is organized as follows: the level set formulation, terminology and notation, in both the traditional and variational sense, is presented in §2. A general framework for the Gibbs free energy equation, based on Xiang et al (2017), written in the variational LS framework is introduced in §3; it allows for prescribing an external pressure and dissolved gas saturation levels. The algorithm and numerical implementation is presented in §4.…”

Evaporation of ethanol/water mixture droplets on micro-patterned PDMS surfaces

“…Surfaces with microstructures such as micro-pillars and micropores have some applications in fabrication of superhydrophobic or superhydrophilic surfaces and oil/water inside the rocks [23][24][25][26][27][28][29]. Yuan et al [24,[30][31] elegantly studied the wettability of patterned surfaces.…”

Wetting and recovery of nano-patterned surfaces beyond the classical picture

“…1. This geometry has been extensively investigated in previous theoretical 28,38,61,62 and computational 27,30,48 studies because despite its simplicity it embodies all the ingredients governing the wetting/recovery transition. 61 The fluid and solid particles interact via the modified LJ potential…”

“…Thus, intense experimental and theoretical research has been devoted to the investigation of the wetting and recovery mechanisms. 20,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] In their seminal work, Lafuma and Quéré 22 have investigated the variation of the contact angle hysteresis as a function of the pressure of a liquid droplet deposited between two textured hydrophobic surfaces. A large and sudden increase of the contact angle hysteresis is a measure of the transition from the Cassie-Baxter to the Wenzel state.…”