Water droplet impact on surfaces is a ubiquitous phenomenon in nature and industry, where the time
of contact between droplet and surface influences the transfer of mass, momentum and energy. To
manipulate and reduce the contact time of impacting droplets, previous publications report tailoring
of surface microstructures that influence the droplet - surface interface. Here we show that surface
elasticity also affects droplet impact, where a droplet impacting an elastic superhydrophobic surface
can lead to a two-fold reduction in contact time compared to equivalent rigid surfaces. Using high speed
imaging, we investigated the impact dynamics on elastic nanostructured superhydrophobic substrates
having membrane and cantilever designs with stiffness 0.5–7630N/m. Upon impact, the droplet excites
the substrate to oscillate, while during liquid retraction, the substrate imparts vertical momentum
back to the droplet with a springboard effect, causing early droplet lift-off with reduced contact time.
Through detailed experimental and theoretical analysis, we show that this novel springboarding
phenomenon is achieved for a specific range of Weber numbers (We >40) and droplet Froude numbers
during spreading (Fr >1). The observation of the substrate elasticity-mediated droplet springboard
effect provides new insight into droplet impact physics.
Water droplet impact on surfaces is a ubiquitous phenomenon in nature and industry, where the timeof contact between droplet and surface influences the transfer of mass, momentum and energy. Tomanipulate and reduce the contact time of impacting droplets, previous publications report tailoringof surface microstructures that influence the droplet - surface interface. Here we show that surfaceelasticity also affects droplet impact, where a droplet impacting an elastic superhydrophobic surfacecan lead to a two-fold reduction in contact time compared to equivalent rigid surfaces. Using high speedimaging, we investigated the impact dynamics on elastic nanostructured superhydrophobic substrateshaving membrane and cantilever designs with stiffness 0.5–7630N/m. Upon impact, the droplet excitesthe substrate to oscillate, while during liquid retraction, the substrate imparts vertical momentumback to the droplet with a springboard effect, causing early droplet lift-off with reduced contact time.Through detailed experimental and theoretical analysis, we show that this novel springboardingphenomenon is achieved for a specific range of Weber numbers (We >40) and droplet Froude numbersduring spreading (Fr >1). The observation of the substrate elasticity-mediated droplet springboardeffect provides new insight into droplet impact physics.
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