Mixing Dynamics of Coalescing Droplets on a Heated Surface

Fundamental understanding of the internal and external dynamics of coalescing droplets is essential for various emerging microfluidic technologies. In applications such as Reactive Inkjet Printing chemical reactions can be instigated in droplets on a heated substrate. However, the impact of surface heating on the mixing dynamics has not been independently investigated. This study presents an analysis of droplet impact and coalescence on a heated surface to understand how temperature influences mixing mechanisms.

Results demonstrate that temperature differences between droplets and the substrate can generate internal flows, significantly accelerating mixing compared to unheated conditions. We further explore the challenges in modelling these dynamics, providing theoretical insights into how heat transfer affects internal and external flows. By combining experimental observations and numerical simulations, we highlight how thermal effects can reduce mixing timescales, with implications for applications in novel manufacturing and other industrial processes where efficient droplet mixing is essential.