Susumu Kitagawa of Kyoto University developed a micro machine that moves autonomously on the water surface while emitting a chemical substance that repels water in alliance with Hiroshi Matsui of New York City University. Made of special crystals, it is about 5 mm square. They constructed the micro machine with porous metallic complexes where cubes of 0.7 nanometers square each stand in neat rows. They put diphenylalanine that has hydrophobic property inside the machine.
In the experiment, they put it in a solution mixed with a substance that melts down the cubic. They confirmed that the hydrophobic substance seeps gradually and the micro machine moves autonomously on the water surface for more than 20 minutes. Please click here to read further detailed information in the Nature Materials.