Laser-Induced Mixing in Microfluidic Channels
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- 作者：Amy N. Hellman ; Kaustubh R. Rau ; Helen H. Yoon ; Stephanie Bae ; James F. Palmer ; K. Scott Phillips ; Nancy L. Allbritton ; Vasan Venugopalan
- 刊名：Analytical Chemistry
- 出版年：2007
- 出版时间：June 15, 2007
- 年：2007
- 卷：79
- 期：12
- 页码：4484 - 4492
- 全文大小：894K
- 年卷期：v.79,no.12(June 15, 2007)
- ISSN：1520-6882
文摘
We demonstrate a novel strategy for mixing solutions andinitiating chemical reactions in microfluidic systems. Thismethod utilizes highly focused nanosecond laser pulsesfrom a Q-switched Nd:YAG laser at 
= 532 nm togenerate cavitation bubbles within 100- and 200-
m-widemicrofluidic channels containing the parallel laminar flowof two fluids. The bubble expansion and subsequentcollapse within the channel disrupts the laminar flow ofthe parallel fluid streams and produces a localized regionof mixed fluid. We use time-resolved imaging and fluorescence detection methods to visualize the mixing process and to estimate both the volume of mixed fluid andthe time scale for the re-establishment of laminar flow.The results show that mixing is initiated by liquid jets thatform upon cavitation bubble collapse and occurs ~20 sfollowing the delivery of the laser pulse. The images alsoreveal that mixing occurs on the millisecond time scaleand that laminar flow is re-established on a 50-ms timescale. This process results in a locally mixed fluid volumein the range of 0.5-1.5 nL that is convected downstreamwith the main flow in the microchannel. We demonstratethe use of this mixing technique by initiating the horseradish peroxidase-catalyzed reaction between hydrogenperoxide and nonfluorescent N-acetyl-3,7-dihydroxyphenoxazine (Amplex Red) to yield fluorescent resorufin. Thisapproach to generate the mixing of adjacent fluids mayprove advantageous in many microfluidic applications asit requires neither tailored channel geometries nor thefabrication of specialized on-chip instrumentation.
= 532 nm togenerate cavitation bubbles within 100- and 200-m-widemicrofluidic channels containing the parallel laminar flowof two fluids. The bubble expansion and subsequentcollapse within the channel disrupts the laminar flow ofthe parallel fluid streams and produces a localized regionof mixed fluid. We use time-resolved imaging and fluorescence detection methods to visualize the mixing process and to estimate both the volume of mixed fluid andthe time scale for the re-establishment of laminar flow.The results show that mixing is initiated by liquid jets thatform upon cavitation bubble collapse and occurs ~20 sfollowing the delivery of the laser pulse. The images alsoreveal that mixing occurs on the millisecond time scaleand that laminar flow is re-established on a 50-ms timescale. This process results in a locally mixed fluid volumein the range of 0.5-1.5 nL that is convected downstreamwith the main flow in the microchannel. We demonstratethe use of this mixing technique by initiating the horseradish peroxidase-catalyzed reaction between hydrogenperoxide and nonfluorescent N-acetyl-3,7-dihydroxyphenoxazine (Amplex Red) to yield fluorescent resorufin. Thisapproach to generate the mixing of adjacent fluids mayprove advantageous in many microfluidic applications asit requires neither tailored channel geometries nor thefabrication of specialized on-chip instrumentation.