Evanescent-Wave-Driven Microrotors Produced by Two-Photon Microfabrication

In this study, we have developed evanescent-wave-driven microrotors by two-photon microfabrication. The evanescent-wave-driven microrotors are located on the surface of a high-refractive-index substrate attached to a prism. By illuminating a laser beam at an angle greater than the critical angle, evanescent waves are generated under the microrotors. When the laser beam is scattered by the blades of the microrotors, the microrotors are affected by radiation pressure. As a result, the microrotors can be rotated by evanescent waves. We designed an efficient microrotor with grating-like blades by electromagnetic field simulation. In our simulation, the optical torque exerted on the microrotor with grating-like blades is more than 5 times as large as that of a microrotor with rectangular blades. In our experiments, it was also demonstrated that the microrotor with grating-like blades could be rotated faster than the microrotor with rectangular blades. The evanescent-wave-driven microrotors will be applied to optically driven lab-on-a-chip devices. (C) 2011 The Japan Society of Applied Physics