Terahertz Humidity Sensing Based on Surface-Modified Polymer Mesh Membranes with Photografting PEGMA Brush

Area of Science:

• Terahertz (THz) technology
• Materials science
• Sensor technology

Background:

• Relative humidity (RH) monitoring is crucial in many fields.
• Existing RH sensors may have limitations in sensitivity, cost, or working range.

Purpose of the Study:

• To demonstrate a simple and compact THz-based RH sensing platform.
• To investigate the performance of a modified polymer membrane for RH sensing.

Main Methods:

• Fabrication of a sensing membrane via UV-induced graft-polymerization of copolymer brushes onto a porous polymer substrate.
• Utilizing an intensity interrogation scheme with a 0.4 THz wave to measure power reduction.
• Correlating power reduction with RH levels and grafting density, verified by water contact angle measurements.

Main Results:

• The THz wave power reduction was found to be proportional to RH levels.
• The best sensitivity achieved was 0.0423 mV/% RH at a grafting density of 1.57 mg/mm³.
• The sensor demonstrated a detection limit of approximately 1% RH and a wide working range (25-99% RH).

Conclusions:

• The developed THz RH sensor is low-cost, flexible, and offers high sensitivity and resolution.
• It exhibits advantages such as low loss and a wide RH working range.
• The sensor is a promising candidate for wearable electronics and industrial/bio-sensing applications.