The ability to manipulate biological cells and micrometer-scale particles plays an important role in many biological and colloidal science applications. However, conventional manipulation techniques, such as optical tweezers, electrokinetic forces (electrophoresis, dielectrophoresis (DEP), and traveling-wave dielectrophoresis), magnetic tweezers, acoustic traps, and hydrodynamic flows, cannot achieve high resolution and high throughput at the same time. Optical tweezers offers high resolution for trapping single particles, but has a limited manipulation area due to tight focusing requirements, while electrokinetic forces and other mechanisms provide high throughput, but lack the flexibility or the spatial resolution necessary for controlling individual particles.
In the dissertation, I present a novel concept called optoelectronic tweezers (OET).
Using light-driven electrokinetic mechanisms (dielectrophoresis, ac electroosmosis), OET permits high-resolution patterning of electric fields on a photoconductive surface for manipulating single cells, micro- and nano-particles with light intensity of 10 nW/cm^2, which is 100,000 times less than with optical tweezers. It opens up the possibility of optical manipulation using an incoherent light source such as light emitting diode (LED) or a halogen lamp. Integrating with a digital micromirror or a liquid crystal spatial light modulator, we have demonstrated parallel manipulation of 31,000 particle traps on a 1.3×1.0 mm^2 area. Using OET technique, we have demonstrated optical manipulation on various polystyrene particles with size range from 45 μm to 500 nm, bacteria (E. Coli), cancer cells (HeLa), and human white blood and red blood cells. With direct optical imaging control, multiple manipulation functions can be combined to achieve complex, multi-step manipulation protocols.
December 31, 2005
Chiou, P. (2005). Massively Parallel Optical Manipulation of Single Cells, Micro- and Nano-particles on Optoelectronic Devices. United States: University of California, Berkeley.