Effect of laser process parameters on contact angle for linear and square grid micro-textured surfaces

Abstract

Bio-mimicking of self-cleaning surfaces is presently being regarded as a promising area of research, especially in bio-implants. Self-cleaning properties of surfaces are mostly evaluated on the basis of contact angle attained by fluids with the contact surfaces. Micro/nano-textured patterns on the surfaces govern the surface tension of liquid thereby contact angle. Accordingly, the hydrophobic and/or hydrophilic nature of surfaces is anticipated according to the application requirements. This work presents comparative evaluation of self-cleaning performance of linear and square grid micro-textured surfaces. The micro-textures were fabricated on biocompatible Ti-6Al-4V alloy substrate using nanosecond pulsed laser. The effect of laser power, scan speed and frequency on contact angle has been investigated. Laser power of 7–14 watts, scan speed of 300–375 mm/s and frequency of 50–80 kHz were laser process parameters for study. Taguchi approach of experimentation followed by ANOVA was adopted for experimentation and analysis. A very precise and accurate contact angle goniometer setup was developed, tested and calibrated inhouse using image analysis software for contact angle measurements. Laser power and frequency were the significant factors deciding hydrophobicity. Surface morphology has also been studied to resemble and realize the extent of lotus leaf effect achieved. Square grid micro-textures exhibited better contact angle compared to linear micro-textures.