“Water droplets rolling on paper remind Kenya Hara of Japanese pinball, or pachinko. A vision of numerous spherical water droplets navigating finely patterned white paper evokes new excitement for the senses. He straightly made it a reality. ”
From the Haptic Exhibition : http://www.ndc.co.jp/hara/works/en/2004/06/haptic.html
I think the material he used was something that has a structure like the leaf of the lotus(or maybe a raincoat) that makes the water remains the shape of the beads, so that the water can “pearls” down along the board.