(498i) Effect of Additives to the Droplet Impact Dynamics

Droplet impact on surfaces is ubiquitous in many industrial applications, ranging from pesticide spraying, to spray coating, to additive manufacturing. Rich phenomenon and impact outcomes including bouncing, merging, and splashing have been observed due to the intrinsic complexity stemming from the interplay of surface tension, viscous effect and inertial effect. The dynamics of the impact process for pure liquids has been studied extensively. However, in industrial applications, complex fluids are more widely involved. The addition of colloidal particles, polymers and surfactant adds another layer of complexity to the impact dynamics. Here, we present experimental results of the effect of the type and concentration of additives on the impact dynamics in terms of a regime map in the nondimensional parameter space and provide physical mechanism for the transition boundaries between bouncing, merging and splashing. Richer phenomenon compared to that with pure liquids have been observed and discussed. The experimental measurements and the physical understanding provide design rules for the optimal operating conditions and selection of materials in various applications.