Biological Applications of Programmable Optoelectrofluidic Manipulation
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1173-U08-01
Biological Applications of Programmable Optoelectrofluidic Manipulation Je-Kyun Park NanoBiotech Laboratory, Department of Bio and Brain Engineering, KAIST, Daejeon 305-701, Republic of Korea
ABSTRACT This paper presents a new programmable particle manipulation using a lab-on-a-display platform, which is a kind of optoelectrofluidic platform applying a liquid crystal display (LCD) as a display device for generating virtual electrodes in optoelectronic tweezers. The reconfigurable virtual electrodes in the lab-on-a-display are more advantageous than other devices which apply the micro-patterned electrodes, because we can freely control the size and position of electrodes as well as the voltage conditions, which affect the particle movements such as concentration and separation of particles. Due to its simple structures, cheap manufacturing costs, and high performances, this new LCD-based optoelectrofluidic platform can be applied to the interactive manipulation of polystyrene microspheres and blood cells. In addition, a method to discriminate normal oocytes for in vitro fertilization is demonstrated by combining the gravity effect with the optically induced positive dielectrophoresis (DEP). The discrimination performance can be enhanced due to the reduction of friction forces acting on the oocytes which are relatively large and heavy cells being affected by the gravity field. With the same device, we also demonstrate the size-dependent microparticle separation as well as the local concentration and assembly of microparticles originated from the image-driven AC electrokinetics such as DEP and AC electroosmosis. The particle movements result from the frequency-dependent behavior according to the particle diameter. This novel technique can be applied to rapidly concentrate, separate and pattern micro-/nanoparticles and biomolecules in many biological and chemical applications.
INTRODUCTION Optoelectrofluidics deals with the electrokinetic motions of particles or molecules and their interactions with optically induced electric field and surrounding fluid. This concept has been demonstrated for the first time through an electrophoretic patterning of colloidal particles using an ultraviolet (UV) pattern projected onto an indium tin oxide (ITO) electrode [1]. When a light micropattern was projected onto the photoconductive layer in an optoelectrofluidic device, the number of electron-hole pairs at the partially illuminated area was significantly increased. As a consequence, a nonuniform electric field was formed in the sample solution, resulting in the optically induced electrokinetic flows and electrostatic interactions around the light pattern. This technology has attracted much attention in several research fields because its elegant manipulation scheme depends on a light-driven virtual electrode that is reconfigurable and programmable for massively parallel processes [2−4]. As a photoconductive material, hydrogenated amorphous silicon deposited on a metal plate electrode was used to induce a nonuniform el
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