Transfer of a microfluid to a stochastic fibre network

The transfer of a microscopic fluid droplet from a flat surface to a deformable stochastic fibre network is investigated. Fibre networks are generated with different levels of surface roughness, and a two-dimensional, two-phase fluid–structure model is used to simulate the fluid transfer. In simulations, the Navier–Stokes equations and the Cahn–Hilliard phase-field equations are coupled to explicitly include contact line dynamics and free surface dynamics. The compressing fibre network is modelled as moving immersed boundaries. The simulations show that the amount of transferred fluid is approximately proportional to the contact area between the fluid and the fibre network. However, areas where the fluid bridges and never actually makes contact with the substrate must be subtracted.

► Fluid transfer to a fibre network in microscale is numerically modelled.
► Free surface and contact line dynamics are explicitly included.
► Contact surfaces are treated as immersed boundaries.
► Fluid transfer is shown to be approximately proportional to the fluid-fibre network contact area.
► However, areas which are bridged by the fluid must be subtracted from the contact area.