It's Harder to Splash on Soft Solids.
Droplets splash when they impact dry, flat substrates above a critical velocity that depends on parameters such as droplet size, viscosity, and air pressure. By imaging ethanol drops impacting silicone gels of different stiffnesses, we show that substrate stiffness also affects the splashing threshold. Splashing is reduced or even eliminated: droplets on the softest substrates need over 70% more kinetic energy to splash than they do on rigid substrates. We show that this is due to energy losses caused by deformations of soft substrates during the first few microseconds of impact. We find that solids with Young's moduli ≲100  kPa reduce splashing, in agreement with simple scaling arguments. Thus, materials like soft gels and elastomers can be used as simple coatings for effective splash prevention. Soft substrates also serve as a useful system for testing splash-formation theories and sheet-ejection mechanisms, as they allow the characteristics of ejection sheets to be controlled independently of the bulk impact dynamics of droplets.
Trinity College, University of Oxford, Oxford OX1 3BH, United Kingdom.
Christopher J
CJ
Howland
Institut Jean Le Rond d'Alembert, UMR 7190 CNRS/UPMC, Sorbonne Universités, F-75005 Paris, France.|Surface du Verre et Interfaces, UMR 125 CNRS/Saint-Gobain, F-93303 Aubervilliers, France.
Arnaud
A
Antkowiak
School of Engineering and Materials Science, Queen Mary, University of London, London E1 4NS, United Kingdom.
J Rafael
JR
Castrejón-Pita
Mathematical Institute, University of Oxford, Oxford OX2 6GG, United Kingdom.
Sam D
SD
Howison
Mathematical Institute, University of Oxford, Oxford OX2 6GG, United Kingdom.
James M
JM
Oliver
Mathematical Institute, University of Oxford, Oxford OX2 6GG, United Kingdom.|Department of Materials, ETH Zürich, Zürich 8093, Switzerland.
Robert W
RW
Style
Department of Engineering Science, University of Oxford, Oxford OX1 3PS, United Kingdom.
Alfonso A
AA
Castrejón-Pita