Micro particle sorting using non-periodic structure of optical pattern

Non-periodic structure of optical pattern can assign distinctive potential landscape to multiple micro particles according to their sizes, and enables optical sorting using only optical gradient force. We have theoretically and experimentally investigated the dependence of success rate of sorting as a function of time on beam power in non fluidic flow system. In the experiment, polystyrene spheres suspended in water were used as samples, and the radii were 0.49 μm, 1.03 μm, and 1.61 μm, respectively. We used multiple optical lines in the experiment, and placed it non-periodically with increasing peak intensities. The experimental result qualitatively agreed with the theoretical one, and the success rate of sorting was more than 90 % with sufficient beam power. We demonstrated our method in the system with flow by placing optical pattern such that optical gradient force acted on particles orthogonal to the flow. In the experiment with flow, triangle optical pattern was used to lift up micro particles onto the top surface where image of optical pattern was formed and to carry the particles to starting position for sorting. Our sorting system can in principle work in broad range of particle velocity with sufficient beam power.