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, including optical tweezers, electrokinetic forces, magnetic tweezers, acoustic traps, and hydrodynamic flows, cannot achieve high resolution and high throughput at the same time. We present an optical image-driven dielectrophoresis technique that permits high-resolution patterning of electric fields on a photoconductive surface for manipulating single cells. It requires 100,000 times less optical intensity than optical tweezers. Using an incoherent light source (a light emitting diode (LED) 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 mm2 area. With direct optical imaging control, multiple manipulation functions are combined to achieve complex, multi-step manipulation protocols.

Optoelectronic tweezers enables optical manipulation with optical power 5 orders of magnitude lower than that of optical tweezers. Such a low power requirement promises the opportunity of optical patterning of virtual electrode using direct image of incoherent light source and large optical manipulation area using a low N.A objective lens with a large field of view. We have demonstrated a direct image patterned virtual channels, valves for passive guiding microscopic particles. We have also demonstrated a dynamic, interactive virtual cage array for assembling microparticle arrays. However, the trap particles are moved manually. This process is time consuming and requires human intervention. An automatic optical manipulator by integrating the OET with a microvision system is proposed here to decrease the process time. The microvision system performs image analysis and pattern recognition, optical pattern generation, and particle path calculation. It enables parallel particle trapping, transporting, and assembling with feedback control. Continuous particel and cell sorting based on image features including fluorescent signals, sizes, surface textures, and shape can also be acheived.

This project demonstrated a two-dimensional droplet manipulation platform allowing fully optical manipulation of droplets on a photosensitive surface. Optically controlled droplet injection, transport, separation, and multiple droplet manipulation have been achieved on manipulating nano-liter size droplets. These functions are realized by sandwiching the droplets between two optoelectrowetting (OEW) surfaces. Optical illumination on OEW surfaces locally changes the surface wettability through electrowetting mechanism. Optical illumination turns the initially Teflon coated surface from hydrophobic to hydrophilic. This optically controlled process is real-time reconfigurable and reversible.  We have demonstrated a maximum transport speed of 78 mm/s on a 100 nano-liters droplet using a scanning laser beam. We have also demonstrated a fully decoupled two-dimensional multi-droplet manipulation on the OEW surfaces. This has promised OEW mechanism to process a large number of liquid droplets for high throughput purposes through projected optical images.

Continuous Opto-Electrowetting (COEW) is effective in manipulating the liquid droplet in pico liter regime. The wetting property of the surface is continuously modified optically with a spatial resolution of a few micrometers through the opto-electrowetting effect. Injection and transport of ultra-small water droplets with 10 pico-liter volumes have been successfully demonstrated. The structure of the device is very simple. The surface only consists of featureless multi-layer thin films deposited on a glass substrate without any mask patterns.