A review of liquid droplet impacting onto solid spherical particles: A physical pathway to encapsulation mechanisms

Encapsulation has received a surge of interest in the biotechnological, chemical and pharmaceutical fields and other industrial processes, owing to numerous applications such as in fluidized catalytic cracking, antenna and wire fabrication, catalytic reactions, and process industries. For example, encapsulation is a technique used to entrap active agents within a carrier material and can be achieved through impact of droplets of encapsulating material on the solid particles of active agents. Considering the importance of dynamics of drop-particle collision, which directly affects the quality of film deposition during encapsulation, the current review is presented to investigate various aspects of drop impact on dry solid spherical surfaces, which is still lacking in the existing literature and aims at encouraging more researchers to study this topic. Also, this review covers frequent examples of droplet impingement onto curved surfaces, with a focus on the latest scientific findings in droplet impacting solid spherical surfaces.