Micro-opto-fluidic platform for solvents identification based on absorption properties in the NIR region

Area of Science:

• Optics and Photonics
• Analytical Chemistry
• Materials Science

Background:

• Spectral analysis of light transmission offers a robust method for fluid composition evaluation.
• Distinguishing between water and various alcohol solutions is crucial in many scientific and industrial applications.

Purpose of the Study:

• To develop and validate an optical method for differentiating water and alcohol samples within a micro-capillary.
• To utilize near-infrared (NIR) spectral transmittance and fluid absorption properties for sample identification.

Main Methods:

• An optical setup was designed using a rectangular glass micro-capillary laid flat on an aluminum mirror.
• Broadband radiation was directed at a 14° incidence angle, reflecting off the mirror and passing through the sample twice.
• Spectral transmittance was measured in the 1.15-1.65 μm NIR range and compared to theoretical models.

Main Results:

• Experimental spectral transmittance ratios showed agreement with theoretical calculations for distilled water, isopropanol, ethylene glycol, and 95% ethanol.
• The method successfully distinguished between different fluid samples based on their unique spectral absorption characteristics.
• The wavelength-dependent attenuation due to fluid absorption was accurately modeled.

Conclusions:

• The proposed optical method effectively distinguishes water and alcohol samples in micro-capillaries using NIR spectral transmittance.
• This technique provides a sensitive and accurate approach for fluid analysis based on absorption spectroscopy.
• The findings validate the use of spectral properties for identifying unknown fluid compositions in microfluidic systems.