An Experimental Study on Complete Droplet Rebound from Soft Surfaces: Critical Weber Numbers, Maximum Spreading, and Contact Time

Droplet impact on soft surfaces (PDMS)
was experimentally studied
with particular interest in the complete rebound of droplets. This
study focuses on the effect of liquid viscosity and the elastic modulus
of the substrate on the critical rebound Weber number, maximum spreading,
and contact time. Specifically, the lower and upper critical Weber
numbers increase with an increasing droplet viscosity. With decreasing
PDMS elastic modulus, the upper critical Weber number increases, while
the lower critical Weber number decreases. The PDMS elastic modulus
does not significantly affect the maximum spreading time and contact
time. An interesting phenomenon of discontinuous contact time was
experimentally observed and was theoretically interpreted.