Both surface chemical and topographical properties are important parameters in many different applications and processes, where wetting and adhesion behavior needs to be optimized. Wettability can be studied by measuring contact angle of the substrate with given liquid. The well-known Young equation describes the balance at the three phase contact of solid-liquid and gas.
γsv = γsl + γlvcosθe
The interfacial tensions, γsv, γsl and γlv, form the equilibrium contact angle θe of wetting. The Young equation assumes that the surface is chemically homogenous and topographically smooth. This is however not true in the case of real surfaces, which instead of having one equilibrium contact angle value exhibit range of contact angles between advancing and receiving values. To define the equilibrium value, surface roughness should be taken into account. Relationship between surface roughness and wettability was defined already in 1936 by Wenzel who stated that adding surface roughness will enhance the chemical wettability of the surface. For example, if the surface is chemically hydrophobic, it will become even more hydrophobic when surface roughness is added.
Until now, it has not been possible to directly combine the surface roughness and contact angle measurements. In this abstract we describe the equipment where these two measurements can be done in conjugation to each other. In addition, with example measurements it will be demonstrated the importance of both surface chemistry and roughness on wetting and adhesion behavior.
oskari.aro@biolinscientific.com
