Ayusman Sen's laboratory team in 2008.

Credit: Penn State

Platinum/gold nanorods immersed in distilled water migrate en masse, from lower right to upper left, toward a source of hydrogen peroxide that has been introduced into this region of the distilled water. As the hydrogen peroxide seeps into the distilled water, it creates a chemical gradient along which the nanorods swim. The metallic 1,500-by-400-nanometer rods propel themselves toward the highest concentration of hydrogen peroxide by catalyzing the oxidation of hydrogen peroxide to oxygen at their platinum heads and to water at their gold tails.

Credit: Ayusman Sen Laboratory, Penn State

Ayusman Sen, professor and head of the Department of Chemistry at Penn State University.

Credit: Penn State