title: Tunable Liquid Gradient Refractive Index (L-GRIN) lens with two degrees of freedom.
abstract: We report a tunable optofluidic microlens configuration named the Liquid Gradient Refractive Index (L-GRIN) lens for focusing light within a microfluidic device. The focusing of light was achieved through the gradient refractive index (GRIN) within the liquid medium, rather than via curved refractive lens surfaces. The diffusion of solute (CaCl(2)) between side-by-side co-injected microfluidic laminar flows was utilized to establish a hyperbolic secant (HS) refractive index profile to focus light. Tailoring the refractive index profile by adjusting the flow conditions enables not only tuning of the focal distance (translation mode), but also shifting of the output light direction (swing mode), a second degree of freedom that to our knowledge has yet to be accomplished for in-plane tunable microlenses. Advantages of the L-GRIN lens also include a low fluid consumption rate, competitive focusing performance, and high compatibility with existing microfluidic devices. This work provides a new strategy for developing integrative tunable microlenses for a variety of lab-on-a-chip applications.
authors: Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802, USA. junhuang@psu.edu.
authors: Xiaole
authors: X
authors: Mao
authors: Sz-Chin Steven
authors: SC
authors: Lin
authors: Michael Ian
authors: MI
authors: Lapsley
authors: Jinjie
authors: J
authors: Shi
authors: Bala Krishna
authors: BK
authors: Juluri
authors: Tony Jun
authors: TJ
authors: Huang
mesh_terms: D004058:Diffusion; D007909:Lenses; D008027:Light; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D009038:Motion