Thickness regimes of power law liquids dip coated onto permeable substrates

Abstract

Coating thin liquid films with complex rheological behaviour on permeable substrates is often an important requirement in several applications such as contact lenses, textiles, and paper-based electronics. Here, we extend the classical Landau-Levich problem of dip coating of Newtonian liquids on rigid substrates to liquids of power-law rheology on permeable substrates. Our results suggest distinct deviation from the classical Landau-Levich relation through exhibition of different regimes of varying dependence of coating film thickness on withdrawal speed. A process map is presented depicting these coating thickness regimes for a wide range of operating parameters such as the substrate permeability factor, power-law exponent of the liquid, and a rescaled capillary number.