AIMsight™ Infrared Microscope & AIRsight™ Infrared/Raman Microscope

Significance of the Topic

Infrared microscopy is a powerful analytical technique for characterizing tiny sample regions in materials science, pharmaceuticals, forensics and quality control. Eliminating the need for liquid nitrogen simplifies workflows and lowers operating costs while maintaining high spectral sensitivity.

Objectives and Study Overview

This application note introduces a Peltier-cooled mercury cadmium telluride (TEC MCT) detector option for the AIMsight and AIRsight infrared microscopes. The goal is to enable infrared microspectroscopy of samples down to 25 × 25 µm without liquid nitrogen, comparing performance against the standard liquid-nitrogen-cooled T2SL detector and a room-temperature DLATGS detector.

Methodology and Instrumentation

Infrared spectra were acquired in transmission, reflection and attenuated total reflection (ATR) modes using:

• AIMsight Infrared Microscope
• AIRsight Infrared/Raman Microscope
• IRXross Fourier Transform Infrared Spectrophotometer
• Detectors: T2SL (liquid-nitrogen-cooled), optional TEC MCT (Peltier-cooled) and DLATGS (room-temperature)

Measurements used apertures sized from 25 × 25 µm to 200 × 200 µm, with scan numbers adjusted for sensitivity and signal-to-noise.

Key Results and Discussion

• Transmission mode on polypropylene-based resin: TEC MCT delivered clear mid-IR spectra for 25 × 25 µm apertures without liquid nitrogen, with noise levels comparable to T2SL at extended scan times. DLATGS required a larger 100 × 100 µm aperture due to lower sensitivity but covered down to 400 cm⁻¹.
• Reflection mode on circuit board adhesions: At 30 × 40 µm, TEC MCT achieved a signal-to-noise ratio similar to T2SL when increasing scans, demonstrating viability for sub-50 µm areas without cryogenics.
• ATR mode on silicone rubber: Both T2SL and TEC MCT provided consistent ATR spectra using a 200 × 200 µm aperture. ATR measurements benefit from large apertures to maximize sensitivity, and TEC MCT matched T2SL performance.

Benefits and Practical Applications

The TEC MCT detector offers:

• Liquid-nitrogen-free operation, reducing maintenance and hazards.
• High sensitivity for microscopic areas down to 25 µm.
• Flexible selection among three detectors based on sample size, wavenumber coverage and sensitivity.

Future Trends and Opportunities

Emerging directions include:

• Development of room-temperature detectors with broader spectral ranges and enhanced sensitivity.
• Integration of automated, AI-driven spectral interpretation for high-throughput analysis.
• Portable IR microscopy platforms for in-field or point-of-care material identification.

Conclusion

The Peltier-cooled MCT detector significantly enhances infrared microscopy by combining near-T2SL sensitivity with the convenience of LN2-free operation, making it a versatile solution for research and industrial laboratories.