Precise Liquid Transport on and through Thin Porous Materials.

Area of Science:

• Materials Science
• Fluid Dynamics
• Surface Science

Background:

• Porous substrates exhibit both lateral and transversal fluid transport capabilities.
• Spatial wettability patterning offers a method to control fluid transport directionality.

Purpose of the Study:

• To investigate different wettability pattern designs for achieving controlled 3D fluid transport in porous substrates.
• To analyze a specific mode of fluid transport with lateral flow on the bottom surface and a dry top surface.
• To develop and validate an analytical model for predicting droplet behavior during transport.

Main Methods:

• Implementation of various wettability patterns on a high-density paper towel.
• Dispensing and observing microvolumes of liquid as droplets.
• Developing an analytical model to describe the temporal changes in penetrating drop shape.
• Comparing model predictions with experimental measurements.

Main Results:

• Different wettability patterns enabled distinct 3D fluid transport schemes.
• Precise transport of metered liquid microvolumes was achieved on the surface and through the substrate.
• A specific mode demonstrated effective lateral transport along the bottom surface, maintaining a dry top surface.
• The analytical model accurately predicted the temporal drop shape variations, aligning with experimental data.

Conclusions:

• Spatial wettability patterning is an effective strategy for directing fluid transport in porous materials.
• The developed analytical model successfully captures the key fluid transport mechanisms.
• This research provides a foundation for designing advanced fluidic devices using patterned porous substrates.