The spreading of small liquid drops over thin and thick porous layers (dry or saturated with
the same liquid) has been investigated in the case of both complete wetting (silicone oils of
different viscosities) and partial wetting (aqueous SDS solutions of different concentrations).
Consideration has been carried out from both experimental and theoretical points of view.
Nitrocellulose membranes of different porosity and averaged pore size were used as a model of
thin porous layers, glass and metal filters were used as a model of thick porous substrates.
It has been shown, that the spreading process follows the power law in time in the case of
spreading of silicon oil drops over porous substrate saturated with the same oil. The liquid flow
in the spreading drop has been matched with the flow in the porous substrate. Both the exponent
and the pre-exponential factor of the power law have been predicted and compared with our
experimental data, which shows the good agreement. An effective lubrication coefficient has
been introduced, which accounts for an effective slippage of liquids over porous substrates. This
coefficient has been both theoretically predicted and experimentally verified. [Continues.]
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy at Loughborough University.