Optical Manipulation of Inorganic and Organic Objects in Soft Microfluidic Devices
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Optical Manipulation of Inorganic and Organic Objects in Soft Microfluidic Devices Cengiz S. Ozkan*, Erhan Ata, Mihrimah Ozkan and Sadik C. Esener *Applied Micro Circuits Corporation, San Diego, CA 92121 Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, CA 92093
ABSTRACT We describe a technique for trapping and manipulation of inorganic and organic objects in microfluidic channels, based on photonic momentum transfer using an optical tweezers arrangement. Microfluidic devices have been fabricated by polydimethylsiloxane (PDMS) elastomer molding of patterns lithographically defined on a thick negative photoresist. Polystyrene microspheres dispersed in water were transferred into the fluidic channels using a syringe pump. Microspheres and live biological cells are trapped and redirected by optical manipulation within the fluidic channels. Optical trapping and patterning will have applications in creation of active cellular arrays for cell biology research, tissue engineering, cell sorting and drug discovery. INTRODUCTION The current trend in the field of MEMS is to create new technologies at the interface of multiple diverse fields of research such as physics, engineering, biology and chemistry [1,2]. Such interdisciplinary work has found applications in a wide range of areas including microfabricated drug delivery systems, penetrating neural probes, use of DNA for nanoscale self assembly, pHsensitive hydrogel valves for microfluidic devices, etc. Microfluidic devices [1] have been attracting scientific and industrial attention since they significantly enhance the speed of medical research and discovery by performing analyses at much higher rates compared to traditional biological laboratories. In addition, the use of such devices require minimal operator intervention and they utilize very small volume of biological samples, on the order of a few nanoliters. Devices have been demonstrated for applications ranging from cell sorting, drug discovery and automated DNA analysis to clinical chemistry panels involving tumor markers, specific protein reactions and infectious diseases. The handling of organic objects (cells, protein and DNA molecules) in some of these devices is based on electrophoretic or electrokinetic movement where an electric field is applied to trap or manipulate the objects. The applied electric field could be large depending on the type of cells or molecules and the fluidic drag force due to fluidic channel geometrical constraints. Certain cellular functions and the organic objects themselves could be highly sensitive and adversely affected or even damaged due to the application of high electric fields. In such cases, applications of photonic momentum transfer could be the non-destructive or the less invasive process. In this paper, we demonstrate that photonic momentum transfer through the use of optical tweezers [3-5] can be utilized for trapping and manipulating organic and inorganic objects within fluidic channels. MATERIALS AND EXPERIMENTAL METHOD
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