Abstract

We demonstrate a novel strategy for mixing solutions and initiating chemical reactions in microfluidic systems. This method utilizes highly focused nanosecond laser pulses from a Q-switched Nd:YAG laser at lambda = 532 nm to generate cavitation bubbles within 100- and 200-microm-wide microfluidic channels containing the parallel laminar flow of two fluids. The bubble expansion and subsequent collapse within the channel disrupts the laminar flow of the parallel fluid streams and produces a localized region of 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 and the time scale for the re-establishment of laminar flow. The results show that mixing is initiated by liquid jets that form upon cavitation bubble collapse and occurs approximately 20 micros following the delivery of the laser pulse. The images also reveal that mixing occurs on the millisecond time scale and that laminar flow is re-established on a 50-ms time scale. This process results in a locally mixed fluid volume in the range of 0.5-1.5 nL that is convected downstream with the main flow in the microchannel. We demonstrate the use of this mixing technique by initiating the horseradish peroxidase-catalyzed reaction between hydrogen peroxide and nonfluorescent N-acetyl-3,7-dihydroxyphenoxazine (Amplex Red) to yield fluorescent resorufin. This approach to generate the mixing of adjacent fluids may prove advantageous in many microfluidic applications as it requires neither tailored channel geometries nor the fabrication of specialized on-chip instrumentation.

Highlights

  • The results show that mixing is initiated by liquid jets that form upon cavitation bubble collapse and occurs ∼20 μs following the delivery of the laser pulse

  • The images reveal that mixing occurs on the millisecond time scale and that laminar flow is re-established on a 50-ms time scale

  • Delivery of nanosecond Nd:YAG laser pulses focused within the microfluidic channel induced plasma formation in the fluid whose expansion resulted in shock wave emission and cavitation bubble formation

Read more

Summary

Introduction

We demonstrate a novel strategy for mixing solutions and initiating chemical reactions in microfluidic systems This method utilizes highly focused nanosecond laser pulses from a Q-switched Nd:YAG laser at λ ) 532 nm to generate cavitation bubbles within 100- and 200-μm-wide microfluidic channels containing the parallel laminar flow of two fluids. We demonstrate the use of this mixing technique by initiating the horseradish peroxidase-catalyzed reaction between hydrogen peroxide and nonfluorescent N-acetyl-3,7-dihydroxyphenoxazine (Amplex Red) to yield fluorescent resorufin This approach to generate the mixing of adjacent fluids may prove advantageous in many microfluidic applications as it requires neither tailored channel geometries nor the fabrication of specialized on-chip instrumentation. The limitations posed by diffusion-based transport have spurred researchers to develop various strategies to rapidly mix small volumes in microfluidic devices These strategies either employ changes in channel geometry (static mixers) or introduce external energy sources (active mixers) to enhance fluid contact or destabilize the laminar flow..

Methods
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call