An Integrated Optofluidic System for Two-Dimensional Focus Point Control

K.-S. Chao, M.-S. Lin, R.-J. Yang
National Cheng Kung University, TW

Keywords: microfluidics, optofluidics, refractive index, hydrodynamic focusing


Recently, optical methods have been widely used for biological and chemical detection in microfluidic or lab-on-a-chip systems. Precise adjustment of the optical path among multiple integrated components, such as flow cytometers, optical tweezers, and molecule detectors, is important. However, traditional optical elements have a fixed refractive index and geometrical shape, and cannot change continuously with variation of the focal length and deviation angle. In this study, we demonstrated an integrated optofluidic system consisting a liquid lens and liquid prism, which can perform both light focusing and deviation. The lens was formed in an expanded chamber with three streams of fluids. A higher refractive index stream was sandwiched between two streams having a lower refractive index. This lens may vary its curvature by controlling flow rates, and therefore change the focal distance. In addition, the use of different flow rate ratios resulted in the formation of a different apex angle for the prism. The light path changed with the different refractive indices of the liquids and the apex angles. In this experimental setup, the focal position can be controlled on a two-dimensional plane. By using different apex angles, the optimum deviation angle is found to range from −6° to 22°.