Tunable optofluidic microlens through active pressure control of an air–liquid interface
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We demonstrate a tunable in-plane optofluidic microlens with a 9× light intensity enhancement at the focal point. The microlens is formed by a combination of a tunable divergent air–liquid interface and a static polydimethylsiloxane lens, and is fabricated using standard soft lithography procedures. When liquid flows through a straight channel with a side opening (air reservoir) on the sidewall, the sealed air in the side opening bends into the liquid, forming an air–liquid interface. The curvature of this air–liquid interface can be conveniently and predictably controlled by adjusting the flow rate of the liquid stream in the straight channel. This change in the interface curvature generates a tunable divergence in the incident light beam, in turn tuning the overall focal length of the microlens. The tunability and performance of the lens are experimentally examined, and the experimental data match well with the results from a ray-tracing simulation. Our method features simple fabrication, easy operation, continuous and rapid tuning, and a large tunable range, making it an attractive option for use in lab-on-a-chip devices, particularly in microscopic imaging, cell sorting, and optical trapping/manipulating of microparticles.
KeywordsOptofluidic Tunable lens Microfluidics Air–liquid interface
We thank Xiaole Mao and Aitan Lawit for helpful discussion. This research was supported by National Science Foundation (ECCS-0824183, ECCS-0801922, and ECCS-0609128) and the Penn State Center for Nanoscale Science (MRSEC). Components of this work were conducted at the Penn State node of the NSF-funded National Nanotechnology Infrastructure Network.
- Godin J, Lien V, Lo YH (2006) Demonstration of two-dimensional fluidic lens for integration into microfluidic flow cytometers. Appl Phys Lett 89:061106Google Scholar
- Hecht E (2001) Optics, Pearson Education, pp 159–161Google Scholar
- Lee SW, Lee SS (2007) Focal tunable liquid lens integrated with an electromagnetic actuator. Appl Phys Lett 90:121129Google Scholar
- Seow YC, Liu AQ, Chin LK, Li XC, Huang HJ, Cheng TH, Zhou XQ (2008) Different curvature of tunable liquid microlens via the control of laminar flow rate. Appl Phys Lett 93:084101Google Scholar
- Shi J, Hsiao VKS, Huang TJ (2007) Nanoporous polymeric transmission gratings for high-speed humidity sensing. Nanotechnology 18:465501Google Scholar
- Shi J, Huang H, Stratton Z, Lawit A, Huang Y, Huang TJ (2009b) Continuous particle separation in a microfluidic channel via standing surface acoustic waves (SSAW). Lab Chip 9:3354–3359Google Scholar
- Shopova SI, Zhou H, Fan X, Zhang P (2007) Optofluidic ring resonator based dye laser. Appl Phys Lett 90:221101Google Scholar