On chip optical tweezers for large scale trapping of microparticles

We present a cost-effective and power efficient approach for on-chip large-scale trapping and sorting of particles in microchamber. Based on the Talbot self-imaging effect in Fresnel region, we make use of a 2D chessboard structure to create a 3D interconnected optical lattice near the emergent surface of the element without adopting an external optical projection configuration. The chessboard structure is, designed to be a binary phase grating and fabricated with electron-beam lithography. As no focusing lens projections system is employed, the presented system enables a larger working area without sacrificing the advantage of high resolution. Theoretically the created optical lattice allows exponential size selectivity for particles sorting. We have experimentally demonstrated simultaneous trapping of hundreds of microparticles in a large regular array. Furthermore, in microfluidic chamber we proved the all-optical continuous separation of microparticles with different sizes.