Near-infrared light-driven Janus capsule motors: Fabrication, propulsion, and simulation

We report a fuel-free, near-infrared (NIR)-driven Janus microcapsule motor. The Janus microcapsule motors were fabricated by template-assisted polyelectrolyte layer-by-layer assembly, followed by spraying of a gold layer on one side. The NIR-powered Janus motors achieved high propulsion with a maximum speed of 42 μm·s^-1 in water. The propulsion mechanism of the Janus motor was attributed to the self-thermophoresis effect: The asymmetric distribution of the gold layer generated a local thermal gradient, which in turn generated thermophoretic force to propel the Janus motor. Such NIR-propelled Janus capsule motors can move efficiently in cell culture medium and have no obvious effects on the cell at the power of the NIR laser, indicating considerable promise for future biomedical applications.