Extended-area optically induced organization of microparticles on a surface

To extend beyond the limited field of view associated with optical tweezers, we implement a new geometry for lensless optical trapping ("LOT"). A Ronchi ruling is imaged at a sample interface beyond the critical angle for total internal reflection imposing local structure upon the optical fields. Due to the resulting transverse optical gradients, more than one thousand microparticles spanning 1 mm 2 were organized into microchannels that are entirely optical in origin. A generalized approach is presented, allowing for either guiding or stable trapping, as a function of the relative intensity of the counterpropagating surface waves.