Optoelectronic tweezers with a non-uniform background field

Abstract

An optoelectronic tweezers (OETs) system employing a non-uniform background electric field is presented. In addition to optically induced electrodes, physical electrodes are incorporated into the design. The geometries of the physical electrodes are selected to create a background field with gradients along a specific axis. Due to the resulting background force, the proposed scheme traps particles along an axis around the rim of the optical spot. This is a resolution improvement over conventional OETs where particle trapping occurs uniformly around the spot. Numerical simulations of the device including conductivity, electric fields, and force profiles are presented. The trapping and manipulation of micro-particles using the device are experimentally demonstrated. The experiment verifies that trapping occurs along a specific axis of the optical beam.