Computational Modeling of Mass Transfer in Paper-Based Analytical Devices

Using computational fluid dynamics, the concentration distribution of fluid samples flowing through porous media is investigated in order to support research on simple, automated microfluidic paper-based analytical devices. Finite microliter volume liquid samples are driven through the porous device material by capillary forces. The flow process is modeled using the Richard's equation for fluid movement through an unsaturated medium. The fluid flow solution is coupled with the convection-diffusion equation to monitor the transport of diluted species through the paper membranes. This is important to visualize the concentration distribution profiles through the test devices as a function of time, in order to determine the relevant time scales for analytical applications.