Wetting on a geometrically structured substrate

Abstract

We have measured the growth of liquid films of Ar and Kr adsorbed on a geometrically structured substrate obtained by machining on a lathe a thin Al disk with a sharp cutting tool. Near liquid-vapor bulk coexistence, the film mass is found to diverge as a power law of the chemical potential difference from saturation with an exponent x=-1.93 +/-0.10, in very good agreement with recent scaling analysis results

Complete wetting of curved microscopic channels

“…16 Although the marginal case of a channel profile with ␥ =1/2 has not been studied explicitly, the exponent measured near saturation is in very good agreement with the value of −1 calculated by applying the same scaling formula 16 used for the linear wedges. 17 Similar results have been obtained with two different polymer pieces hot embossed by the same silicon masters but having different thicknesses and more irregular edges. 23 For a quantitative analysis of this crossover, we have extended the analysis developed for a linear wedge 18 to the case of nonlinear cusps 23 with ␥ =1/2.…”

“…For a more complete overview, we have also plotted an isotherm acquired with a flat disk of Zeonex and older data taken on silicon crystals patterned with microscopic linear wedges. 17 The four isotherms have been vertically shifted for ease of comparison. For the same reason, the horizontal error bars related to the finite resolution in the measurement of the vapor pressure have been omitted.…”

Complete Wetting on a Linear Wedge

“…2. The results of this study indicate that the Si surface has an rms roughness 15 A. The second substrate is a thin stainless steel (s.s.) disk, diameter 2 cm and thickness 300 m, whose faces have VOLUME 89, NUMBER 16…”

“…The relative increase I=I 0 is caused by the mass of the adsorbed film and by the hydrodynamic contribution due to the mass of the dynamically displaced fluid. For the two substrate geometries used in this study, the frequency decrease due to this viscous coupling V is expected to be a simple function of the vapor density and viscosity; that is, V V p [14,15]. We have evaluated the validity of this correction and determined the geometrical factors appearing in V by taking extensive vapor pressure adsorption isotherms of He, Ne, and Ar at room temperature, where the only contribution to the frequency is due to the viscous coupling to the vapor.…”

“…The microbalance is mounted inside a double wall copper cell to reduce thermal gradients [15] and is housed in the vacuum space of a homemade bath cryostat. To eliminate the pressure variations due to the daily oscillations in the temperature of the lab, we have placed the capacitance pressure gauge right before the cryostat.…”