Submillisecond mixing in a continuous-flow, microfluidic mixer utilizing mid-infrared hyperspectral imaging detection

Area of Science:

• Chemical Engineering
• Spectroscopy
• Microfluidics

Background:

• Microfluidic devices enable precise control over small fluid volumes.
• Real-time monitoring of rapid mixing processes is crucial for chemical kinetics.
• Mid-infrared (IR) spectroscopy offers label-free detection based on intrinsic molecular vibrations.

Purpose of the Study:

• To develop and characterize a continuous-flow microfluidic mixer with submillisecond mixing capabilities.
• To integrate mid-infrared hyperspectral imaging for real-time detection within the microfluidic mixer.
• To demonstrate the mixer's utility for studying rapid chemical changes, such as protonation.

Main Methods:

• A microfluidic mixer was fabricated by sandwiching a polymer spacer with microchannels between IR transparent windows.
• Hydrodynamic focusing was employed to create a thin sample jet for efficient mixing.
• Mid-infrared hyperspectral imaging was used to capture absorbance spectra over time, enabling kinetic analysis.

Main Results:

• An experimentally determined mixing time of 269 μs was achieved for a pD jump in adenosine monophosphate (AMP) solution.
• Experimental results showed good agreement with simulations of fluid mixing.
• The system successfully monitored the protonation state of AMP using its intrinsic IR absorbance.

Conclusions:

• The developed IR microfluidic mixer provides a robust platform for submillisecond mixing and real-time chemical analysis.
• This label-free approach avoids interference from bulky dyes, preserving molecular integrity.
• The technology is suitable for investigating fast chemical reactions and molecular interactions in various scientific fields.