Computational Inverse Method to Determine Wetting Parameters of Paper-Based Microfluidic Substrates

Abstract

Flow in unsaturated porous media can be described with the Richards equation, in which the microscopic interactions between the fluid and solid matrix are considered at a macroscopic level and expressed as nonlinear functions. Widely used porous media models provide expressions for these functions, with parameters that may be fit to the results of certain measurements. These models are usually already implemented in numerical tools—including our own software Fronts (https://github.com/gerlero/Fronts.jl). As a general equation for porous media, the Richards equation can also predict capillary flow on substrates used for microfluidic paper-based analytical devices, such as Whatman