Triple-Pillar Wetting Regulates Capillary Wicking in High-Aspect-Ratio Micropillar Arrays

Area of Science:

• Fluid dynamics
• Porous media physics
• Surface science

Background:

• Capillary wicking is crucial for liquid transport in microfluidic devices and porous materials.
• The wetting topology of the meniscus significantly impacts capillary flow dynamics in structured media.

Purpose of the Study:

• To investigate the influence of wetting topology on capillary imbibition in high-aspect-ratio micropillar arrays.
• To explore the effects of surface wettability and fluid composition on meniscus behavior and flow velocity.

Main Methods:

• High-speed visualization of capillary imbibition.
• Development and application of a geometry-informed capillary-pressure model.
• Systematic variation of surface wettability and working-fluid composition.

Main Results:

• Triple-pillar wetting (TPW) enhances capillary driving forces compared to double-pillar wetting (DPW) due to increased wetted perimeter.
• The fraction of TPW positively correlates with front velocity and decreases with decreasing interfacial driving parameter (σ cos θ).
• Equilateral-triangular arrays promote TPW and show better performance than square arrays under favorable wetting conditions, but are prone to pinning at higher contact angles.

Conclusions:

• Pore-scale meniscus topology is a key determinant of liquid-gas interfacial propagation in structured porous media.
• Understanding wetting topology dynamics is essential for optimizing capillary imbibition and liquid transport in microdevices.
• Array geometry and fluid-surface interactions critically influence the dominant wetting mode and overall pumping performance.