Non-Destructive Permittivity and Moisture Analysis in Wooden Heritage Conservation Using Split Ring Resonators and...

Area of Science:

• Materials Science
• Electrical Engineering
• Cultural Heritage Conservation

Background:

• Non-invasive monitoring is crucial for assessing the condition of cultural heritage materials.
• Dielectric permittivity is sensitive to material composition and moisture content.
• Existing methods for material assessment can be invasive or costly.

Purpose of the Study:

• To develop and validate a wireless, non-invasive sensing system for monitoring dielectric permittivity.
• To assess the system's applicability for detecting moisture content in cultural heritage materials, specifically wood.
• To provide a tool for preventive conservation by enabling early detection of water-induced degradation.

Main Methods:

• Utilized a passive split-ring resonator tag coupled to an antipodal Vivaldi antenna operating in the reactive near-field.
• Performed numerical simulations and experimental measurements to correlate resonance frequency shifts with dielectric permittivity.
• Calibrated the system using reference materials and validated it on various wood species at different humidity levels.
• Confirmed findings with a portable, low-cost coaxial sensor and a miniaturized Vector Network Analyzer.

Main Results:

• Demonstrated a correlation between antenna reflection coefficient resonance frequency and dielectric permittivity.
• Established a calibration curve using reference materials (PVC, PTFE, PMMA, PC).
• Revealed a sigmoidal relationship between moisture content and permittivity in wood samples (fir, poplar, beech, oak).
• Validated the system's performance with a portable, localized measurement setup.

Conclusions:

• The developed sensing platform is portable, contactless, and scalable for real-world monitoring of cultural heritage.
• The system enables minimally invasive assessment of material integrity and early detection of moisture-induced damage in wood.
• This technology supports preventive conservation strategies by identifying critical moisture thresholds that can lead to degradation.