2-D evanescent trapping of colloids in the vicinity of a micrometer waveguide

Abstract

We report on the trapping of micrometer colloids using the evanescent wave from a multimode cylindrical optical waveguide. We show that the particle trapping is a two-step process. With a low-power visible laser injected in the device, particles are first captured at a radial distance twice greater than the diameter of the waveguide and then drawn near to it. In a second time particles turn around the waveguide and get trapped in a direction corresponding to the TM polarization of the laser. Such a device could be easily implemented in microfluidic systems in order to coat surfaces or to control particles deposition and assembly. Conversely, it could find applications in the filtration process to aggregate and remove colloidal pollutants.