  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 $\lesssim 100$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.
