  We experimentally investigate the splashing mechanism of a millimeter-sized
ethanol drop impinging on a structured solid surface, comprised of
micro-pillars, through side-view and top-view high speed imaging. By increasing
the impact velocity we can tune the impact outcome from a gentle deposition to
a violent splash, at which tiny droplets are emitted as the liquid sheet
spreads laterally. We measure the splashing threshold for different
micropatterns and find that the arrangement of the pillars significantly
affects the splashing outcome. In particular, directional splashing in
direction in which air flow through pattern is possible. Our top-view
observations of impact dynamics reveal that an trapped air is responsible for
the splashing. Indeed by lowering the pressure of the surrounding air we show
that we can suppress the splashing in the explored parameter regime.
