Light-actuated contactless macro motors exploiting Bénard-Marangoni convection.

Near-infrared light is commonly used to move small objects floating on water by exploiting the Bénard-Marangoni convection. This is because infrared light is absorbed well by water and the induced thermal gradients are responsible for the objects' motion. However, visible light was recently used to move macroscopic objects on the free liquid surfaces. In this work, we show the use of visible light to rotate symmetric millimeter-sized objects. Those objects represent light-driven macro motors that are able to work in a continuous or step-by-step mode. We studied light intensity's effects on our system's angular velocity and estimated the entire process's conversion efficiency.