Massively parallel manipulation of single cells and microparticles using optical images

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(1-6), electrokinetic forces (electrophoresis(7,8), dielectrophoresis(9), travelling-wave dielectrophoresis(10,11)), magnetic tweezers(12,13), acoustic traps(14) and hydrodynamic flows(15-17) - 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 x 1.0 mm(2) area. With direct optical imaging control, multiple manipulation functions are combined to achieve complex, multi-step manipulation protocols.