The spreading dynamics of a liquid drop on a viscoelastic solid

The liquid-fluid tension at the edge of a liquid drop may provoke a wetting ridge on a sufficiently soft solid substrate. Many soft solids such as polymers, and in particular elastomers, are viscoelastic and display hysteretic characteristics in a strain cycle. Such a strain cycle can be present near the advancing wetting ridge of a spreading drop. By considering that the excess capillary free energy is consumed during spreading by both viscous dissipation in the liquid and by mechanical, viscoelastic hysteresis in the solid, it is shown how spreading properties may be modified. An important degree of wetting hysteresis may result. In addition absolute spreading rates are reduced.