Extract a directionally-dependent effective capillary radius in porous membranes for wicking prediction in lateral flow assays

This study introduces a computational framework for determining a directionally-dependent effective pore radius in porous membranes, enabling precise predictions of capillary-driven wicking behavior, particularly in lateral flow assays (LFAs), a type of medical rapid test widely used for point-of-care testing. By utilizing digital twins generated from 3D high-resolution imaging techniques like confocal laser scanning microscopy and computed tomography, the structural properties of porous polymeric membranes are examined at the pore scale. The primary focus of this work is the determination of the effective pore radius, a critical parameter for accurately modeling capillary-driven wicking behavior. To achieve this, a phase-field approach is employed to simulate two-phase imbibition processes, allowing for the precise derivation of the effective pore radius while explicitly accounting for directional anisotropy. These parameters are then incorporated into a macroscopic Darcy-based wicking model to forecast wicking behavior at the application scale. Experimental validation demonstrates that this methodology provides accurate predictions of wicking behavior across various membrane samples, while also accounting for directionally-dependent wicking effects. This targeted approach enables a deeper understanding of the relationship between pore-scale structure and macroscopic fluid flow. Additionally, the method demonstrates its versatility by allowing the extraction of wetting properties, such as surface energy and contact angle. This computational approach serves as a cost-effective alternative to experimental analyses and offers valuable insights for optimizing porous membrane designs for LFAs and other applications that require precise control of liquid flow.