PREDICTIVE MODELING OF LIQUIDS SPREADING ON SOLID-SURFACES

A liquid spreading model is developed in which surface and gravitational driving energies are balanced against the energy lost through bulk viscous dissipation. Behaviour is described in terms only of independently measurable quantities, with no adjustable parameters. Additionally, the model can be used to predict liquid viscosity as a function of spreading behaviour. Two different liquid velocity fields are considered, one appropriate for bulk droplet spreading, and the other for thin liquid (e.g. small contact angle) spreading. A time constant indicating the time scale of bulk limited spreading processes is derived. Application to a lead silicate liquid on a gold substrate demonstrates close agreement of the bulk spreading model and predicted time constant with experiment; and literature data of the spreading of polydimethylsiloxane liquids on modified Si/SiO2 surfaces demonstrate reasonable agreement with predictions of the thin liquid model.