Contact angle measurement on micropatterned surface using sessile drop shape fit profile detection

Abstract

Micro-nano patterned surfaces have significant applications in various fields as they behave differently under the effect of catalysts, magnetic energy, electronic emission/absorption, optics and biological cells. Engineering these topologies demands a better understanding of the contact angle. The current contact angle measurement techniques assume the drop to be a perfect sphere, neglect gravitational and molecular dispersion effects; thereby leading to inaccuracies. This is because the micro-machined surfaces exhibit sub-micrometre scale porosity and pattern dimensions are comparable to the droplet size, resulting in composite interfaces at micro-nano scale. In this paper, the authors assessed the adaptability of conventional measurement techniques for textured surfaces and developed an algorithm that is based on curve fitting over sessile drop after edge detection. The algorithm performs edge detection, contact point identification and curve fitting and corrects uneven surfaces and was tested on micro-patterned surfaces fabricated over three different materials: polydimethylsiloxane, polystyrene and acrylic using laser.