Visualization of Gas Mass Transfer by Interferometric Microsphere Microscopy

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• In situ observation of gas mass transfer is vital for advanced sensing and catalytic materials.
• Visualizing gas distribution at micro/nano interfaces is difficult due to weak optical signals and resolution-FOV trade-offs.

Purpose of the Study:

• To develop a label-free microscopy technique for high-resolution, large-field-of-view gas dynamics imaging.
• To establish the structure-performance relationship in colorimetric gas sensors by analyzing gas flow dynamics.

Main Methods:

• Developed label-free interferometric microsphere microscopy (IMM) with 50 nm resolution and 100 μm² FOV.
• Utilized a 45 μm microsphere for large-scale imaging.
• Employed multiwavelength gas imaging with frequency shift technology and algorithmic fusion to enhance resolution.

Main Results:

• Identified a critical Knudsen number (Kn = 0.01) for the transition from laminar to vortical gas flow.
• Observed laminar flow at Kn = 0.008 (6.3 μm micropores) and vortex flow at Kn = 0.01 (4.5 μm micropores).
• Demonstrated a 70% improvement in sensor response due to optimized vortex gas diffusion.

Conclusions:

• IMM is a powerful tool for real-time gas dynamics detection at the micro/nano scale.
• Quantitative structure-performance relationships for functional materials can be determined using IMM.
• Optimizing micropore size is critical for enhancing gas sensor performance through controlled gas diffusion regimes.