COALESCENCE AND MIXING OF DROPLETS WITH IDENTICAL AND DISTINCT SURFACE TENSIONS ON A WETTABILITY GRADIENT SURFACE

This study investigates the influence of identical and distinct surface tensions on droplet coalescence and mixing processes after a head-on collision between a moving droplet and a stationary droplet on a wettability gradient surface (made from the self-assembly monolayer, SAM technique) by micro-PIV (particle image velocimetry) measurement and micro-LIF (laser induced fluorescence) technique. The results demonstrate that coalescence of the droplets with distinct surface tensions achieves superior mixing quality to that of the droplet with identical surface tension. This study would significantly contribute to the issue of droplet mixing and reaction in a microfluidic open system.