(151b) Filling of Initially Empty Cavities By Advancing Water Fronts
Â We have investigated the factors affecting the rate at which water fills micro-scale, cavities. Three-dimensional imaging with confocal microscopy coupled with fluorescence microscopy were used in these studies. We find that the concentration of dissolved air in the water significantly changes the rate at which cavities get filled: deaerated water filled the cavities within 15 minutes, while 2 weeks was required for aerated water. Therefore, the water available for air to dissolve into plays a very significant role in cavity filling. We also tested the effects of various surfactants in the water: surfactants (dissolved at their CMC) shortened the filling time, taking less than 15 minutes in all cases, due more to the surface tension lowering than the changing intrinsic contact angle. More generally, reducing Î³LV always speeded up the filling rates. We also observed capillary condensates forming and slowly growing on the bottom of the cavities while the cavities were still only in the partially-filled state, due to the diffusion of water through the vapor to the (hydrophilic) surfaces.