Water Drop Evaporation on Slippery Liquid-Infused Porous Surfaces (SLIPS): Effect of Lubricant Thickness, Viscosity,...

Area of Science:

• Surface science and nanotechnology
• Fluid dynamics and heat transfer

Background:

• Sessile drop evaporation on slippery liquid-infused porous surfaces (SLIPS) is critical for applications but complex to model.
• The infused lubricant creates a wetting ridge, reducing the evaporable surface area and evaporation rate.
• Previous models did not fully explore the impact of initial lubricant height, viscosity, and surface pattern.

Purpose of the Study:

• To investigate the effects of initial lubricant heights, viscosity, and solid pattern type on water drop evaporation from SLIPS.
• To develop and validate a novel diffusion-limited evaporation model for SLIPS.
• To determine optimal lubricant parameters for efficient SLIPS performance.

Main Methods:

• Water drops were evaporated from SLIPS fabricated with silicone oils (20 and 350 cSt) on micropatterned Si wafers.
• Experiments were conducted under controlled relative humidity and temperature.
• A new diffusion-limited evaporation equation was derived based on the available liquid-air interfacial area (A_LV).

Main Results:

• Increased initial lubricant height (h_oil)i led to a near-linear increase in ridge height (h_r)i and slower evaporation rates.
• The derived diffusion constant (D) for water vapor in air was accurately calculated up to h_oil = 8 μm.
• Deviations in D were observed for h_oil > 8 μm, attributed to oil cloaking layers; increased oil viscosity and pillar patterns had minor effects on evaporation.

Conclusions:

• Initial lubricant height is a key factor influencing evaporation rate on SLIPS.
• The novel evaporation model accurately predicts diffusion constants within a specific lubricant height range.
• Findings provide guidance for optimizing lubricant thickness and viscosity in SLIPS for cost-effective applications.