Microfluidics and Nanofluidics

, Volume 9, Issue 2–3, pp 313–318 | Cite as

Tunable optofluidic microlens through active pressure control of an air–liquid interface

  • Jinjie Shi
  • Zak Stratton
  • Sz-Chin Steven Lin
  • Hua Huang
  • Tony Jun HuangEmail author
Research Paper


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.


Optofluidic 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.


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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Jinjie Shi
    • 1
  • Zak Stratton
    • 1
  • Sz-Chin Steven Lin
    • 1
  • Hua Huang
    • 1
  • Tony Jun Huang
    • 1
    Email author
  1. 1.Department of Engineering Science and MechanicsThe Pennsylvania State UniversityUniversity ParkUSA

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