Optically trapped and driven paddle-wheel

We demonstrate the control and rotation of an optically trapped object, an optical paddle-wheel, with the rotation direction normal to the beam axis. This is in contrast to the usual situation where the rotation is about the beam axis. The paddle-wheel can be optically driven and moved to any position in the field of view of the microscope, which can be of interest for various biological applications where controlled application of a fluid flow is needed in a particular location and in a specific direction. This is of particular interest in signal transduction studies in cells, especially when a cell is flat and spread out on a surface.