The transport processes in the three phase contact region depend on various parameters, for example, the solid-liquid system, the temperature, and the interface shape, which is a measure of the intermolecular force (pressure) field. The intermolecular pressure field is a strong function of the solid surface morphology. The non-smooth nature of the solid surfaces is encountered in various technologies like micro-heat pipes, lab-on-a-chip processes, ink-jet rapid prototyping etc. The performance of such devices is affected by the structured shape of the solid surface which manipulates the efficient distribution of liquid and vapor. The topography of the solid surface can be tailored to improve the fluid distribution which in turn increases the efficiency of such devices. However, there is a lack of relevant theories as well as relevant data concerning effect of the length scales of the surface roughness on contact line dynamics at a microscopic level and further understanding is required on this subject.

In this work, we will compare the characteristics of a sidewall meniscus on two kinds of surfaces that were produced by means of simple plasma based micro-fabrication techniques. AFM based analysis of these two surfaces was performed to obtain their surface features. Plasma etched and plasma deposited surfaces exhibit vastly different roughness length scales because the surface morphology has sharp peaks and mounted shape respectively. A reflectivity/interferometry technique was used to obtain the thickness profile, slope angle profile and the liquid pressure profile of an octane meniscus under isothermal and non isothermal conditions on our model surfaces. Our experimental results show that the presence of surface roughness increases wetting in the adsorbed film and the transition region (< ~ 400 nm) under isothermal conditions. Under non isothermal conditions roughness increases wetting even in the bulk meniscus region. As a result, the slope angle of a heated meniscus is reduced on a rough surface. A correlation between the surface characteristics obtained from the AFM scan and the meniscus characteristics shows that liquid wetting increases with higher RMS roughness and the long wavelength ratio (RMW roughness/ correlation length). We also found that the peak curvature in the transition region increases monotonically with the correlation length. Lateral and horizontal roughness can not be controlled independently when a single fabrication technique is used to generate roughness. Therefore, two different techniques were utilized to prepare surface with entirely different morphology. The results from the two model surfaces will be utilized to obtain an independent assessment of the effect of horizontal and lateral surface roughness on meniscus characteristics.