Using the transfer of a Langmuir monolayer as a probe of wetting

We observe a spontaneous transfer of a Langmuir monolayer of valinomycin to a hydrophilic substrate as soon as the edge of the substrate touches the water surface. By measuring the total monolayer area transferred, the capillary rise h can be determined. We find that the dependence of h on the spreading pressure is well accounted for by an expression due to Joanny and de Gennes but that the actual values of h are five orders of magnitude too small. "Prewetting" the substrate before the monolayer was allowed to spread did not affect the observed capillary rise.