Micromachined Fused Silica Liquid Core Waveguide Capillary Flow Cell

Area of Science:

• Analytical Chemistry
• Optical Engineering
• Materials Science

Background:

• High-Performance Liquid Chromatography (HPLC) requires sensitive detection methods.
• Traditional flow cells can have limitations in path length and sensitivity.
• Microfabrication offers potential for miniaturized and integrated optical detection systems.

Purpose of the Study:

• To develop and characterize a planar, chip-based flow cell for UV-Vis absorbance detection in HPLC.
• To investigate the performance of microfabricated liquid core waveguides (LCWs) for long path length detection.
• To analyze the impact of waveguide geometry on linearity and calibration slope.

Main Methods:

• Microfabrication of free-standing liquid core waveguide (LCW) capillary detection tubes.
• Utilization of total internal reflection for light propagation within the LCW.
• 3D ray tracing simulations to model waveguide behavior.
• Experimental evaluation of linearity, calibration slope, and surface quality effects.

Main Results:

• Lithographically produced LCWs with varying geometries were fabricated and tested.
• 3D ray tracing was crucial for understanding complex waveguide geometries and multipath behavior.
• Nonlinearity was observed but found to be manageable in specific, easily producible geometries.
• Experimental performance correlated with LCW surface quality and light coupling efficiency.

Conclusions:

• The developed planar, chip-based flow cell with LCW technology is a viable option for UV-Vis absorbance detection in HPLC.
• Careful selection of LCW geometry can mitigate nonlinearity issues.
• Surface quality and efficient light coupling are critical for optimal experimental performance.