1. Department of Electrical Engineering and Computer Sciences, and Berkeley Sensor and Actuator Centre (BSAC), University of California at Berkeley, California 94720, USA

Correspondence to: Ming C. Wu¹ Correspondence and requests for materials should be addressed to M.C.W. (Email: wu@eecs.berkeley.edu).

Abstract

The ability to manipulate biological cells and micrometre-scale particles plays an important role in many biological and colloidal science applications. However, conventional manipulation techniques—including optical tweezers^{1, 2, 3, 4, 5, 6}, electrokinetic forces (electrophoresis^{7, 8}, dielectrophoresis⁹, travelling-wave dielectrophoresis^{10, 11}), magnetic tweezers^{12, 13}, acoustic traps¹⁴ and hydrodynamic flows^{15, 16, 17}—cannot achieve high resolution and high throughput at the same time. Optical tweezers offer high resolution for trapping single particles, but have a limited manipulation area owing to tight focusing requirements; on the other hand, electrokinetic forces and other mechanisms provide high throughput, but lack the flexibility or the spatial resolution necessary for controlling individual cells. Here we present an optical image-driven dielectrophoresis technique that permits high-resolution patterning of electric fields on a photoconductive surface for manipulating single particles. It requires 100,000 times less optical intensity than optical tweezers. Using an incoherent light source (a light-emitting diode or a halogen lamp) and a digital micromirror spatial light modulator, we have demonstrated parallel manipulation of 15,000 particle traps on a 1.3 1.0 mm² area. With direct optical imaging control, multiple manipulation functions are combined to achieve complex, multi-step manipulation protocols.

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