title: Hydrodynamically tunable optofluidic cylindrical microlens.
abstract: In this work, we report the design, fabrication, and characterization of a tunable optofluidic microlens that focuses light within a microfluidic device. The microlens is generated by the interface of two co-injected miscible fluids of different refractive indices, a 5 M CaCl(2) solution (n(D) = 1.445) and deionized (DI) water (n(D) = 1.335). When the liquids flow through a 90-degree curve in a microchannel, a centrifugal effect causes the fluidic interface to be distorted and the CaCl(2) solution bows outwards into the DI water portion. The bowed fluidic interface, coupled with the refractive index contrast between the two fluids, yields a reliable cylindrical microlens. The optical characteristics of the microlens are governed by the shape of the fluidic interface, which can be altered by simply changing the flow rate. Higher flow rates generate a microlens with larger curvature and hence shorter focal length. The changing of microlens profile is studied using both computational fluid dynamics (CFD) and confocal microscopy. The focusing effect is experimentally characterized through intensity measurements and image analysis of the focused light beam, and the experimental data are further confirmed by the results from a ray-tracing optical simulation. Our investigation reveals a simple, robust, and effective mechanism for integrating optofluidic tunable microlenses in lab-on-a-chip systems.
authors: Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802, USA.
authors: Xiaole
authors: X
authors: Mao
authors: John Robert
authors: JR
authors: Waldeisen
authors: Bala Krishna
authors: BK
authors: Juluri
authors: Tony Jun
authors: TJ
authors: Huang
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007909:Lenses; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D008962:Models, Theoretical; D012031:Refractometry / Q000295:instrumentation* / Q000379:methods