Gelatin-Coated High-Sensitivity Microwave Sensor for Humidity-Sensing Applications.

Area of Science:

• Materials Science
• Electrical Engineering
• Sensor Technology

Background:

• Poly(vinyl alcohol) (PVA) is a widely used hydrophilic polymer for humidity sensors.
• Gelatin, a natural protein-based polymer, offers an alternative material for sensing applications.
• Microwave sensors based on defected ground structure with modified interdigital capacitors (DGS-MIDC) are suitable for humidity detection.

Purpose of the Study:

• To compare the humidity-sensing characteristics of gelatin and PVA.
• To evaluate the performance of DGS-MIDC microwave sensors coated with gelatin and PVA.
• To investigate the sensitivity and relative permittivity changes of the sensors under varying relative humidity.

Main Methods:

• Fabrication of two DGS-MIDC microwave sensors (0.02 mm thickness), one coated with gelatin and the other with PVA.
• Testing sensor response to relative humidity (RH) from 50% to 80% at 25 °C.
• Analysis of percent relative frequency shift (PRFS) and percent relative magnitude shift (PRMS) to determine humidity sensitivity.

Main Results:

• The gelatin-coated sensor exhibited higher capacitive humidity sensitivity (PRFS and PRMS) than the PVA-coated sensor.
• Gelatin showed significantly greater sensitivity at lower RH (50%–60%) compared to PVA.
• The change in extracted relative permittivity was more pronounced for the gelatin-coated sensor with varying RH.

Conclusions:

• Gelatin presents superior humidity-sensing capabilities compared to PVA for L-band microwave applications.
• Gelatin's enhanced sensitivity at low RH makes it a promising material for precise humidity monitoring.
• The study validates gelatin as a viable alternative for developing high-performance capacitive humidity sensors.