Self-lubricated bouncing of hot droplets

Droplet bouncing holds significant potential for various applications, including self-cleaning, anti-icing, anti-fogging, enhanced heat transfer, droplet manipulation, and energy harvesting. While substantial progress has been made in understanding room-temperature droplet impact dynamics, the bouncing behavior of high-temperature droplets remains underexplored. Given the prevalence of hot and burning droplets in scenarios such as fireworks, fuel sprays, and fire safety, it is critical to understand droplet bouncing dynamics under these conditions. This study reveals a previously unexamined enhancement in the bouncing of high-temperature droplets, both burning and non-burning, on various solid surfaces, including smooth and rough substrates, with different contact angles. Through experimental investigations and numerical simulations, this work demonstrates the significant influence of the Marangoni effect, which arises from the uneven cooling of high-temperature droplets, leading to an increase in gas-film thickness that enhances the rebound. This enhanced bouncing behavior opens up possibilities for further applications, such as improving the combustion efficiency of fuel-spray droplets and inspiring the design of fire-retardant coatings that leverage the strategy of repelling burning droplets. © 2025 The Author(s)