Infrared imaging with visible light in microfluidic devices: the water absorption barrier

Area of Science:

• Biomedical optics
• Spectroscopic imaging
• Microfluidics

Background:

• Mid-infrared absorption by water complicates chemical mapping of biological samples.
• Microfluidic chips are used in infrared spectro-microscopy to control water layer thickness.
• The impact of water layer thickness on instrument performance requires experimental validation.

Purpose of the Study:

• To experimentally quantify water absorption effects in infrared spectro-microscopy.
• To evaluate the performance of different infrared imaging techniques with varying water layer thicknesses.
• To compare standard FTIR microscopy with quantum infrared microscopy for biological sample analysis.

Main Methods:

• Fabrication of microfluidic devices with controlled water layer thicknesses (up to 30 μm).
• Measurement using a standard Fourier-transform infrared (FTIR) microscope.
• Measurement using a quantum infrared (Q-IR) microscopy technique.

Main Results:

• Both FTIR and Q-IR microscopy successfully measured mid-IR absorption spectra with up to 30 μm water layers.
• The Q-IR technique demonstrated practical advantages including lower complexity, cost, and easier operation compared to synchrotron-based FTIR.
• Experimental data validates the feasibility of analyzing biological samples with significant water content using these techniques.

Conclusions:

• Infrared spectro-microscopy is viable for analyzing biological samples with substantial water layers.
• Quantum infrared microscopy presents a more accessible and cost-effective alternative to synchrotron-based FTIR for such applications.
• This study provides experimental evidence for overcoming water absorption challenges in mid-IR bio-imaging.