Biopolymer Optical Fibers for High-Sensitivity Quantitative Humidity Monitoring

Area of Science:

• Materials Science
• Biotechnology
• Sensor Technology

Background:

• Biopolymers offer tunable optical properties for sustainable optical fiber fabrication.
• Existing research has explored biopolymer optical fibers for limited applications, but quantitative environmental sensing remains underdeveloped.
• Quantitative sensing of environmental parameters using biopolymer optical fibers has not been previously reported.

Purpose of the Study:

• To report the first quantitative determination of relative humidity (RH) using fully biopolymer optical fibers.
• To investigate the humidity sensing capabilities of methylcellulose and methylcellulose-alginate composite optical fibers across the visible and near-infrared spectrum.
• To explore the tunability of sensor performance through fiber composition and fabrication methods.

Main Methods:

• Fabrication of methylcellulose and methylcellulose-alginate composite optical fibers.
• Quantitative measurement of relative humidity (RH) using the fabricated optical fibers.
• Characterization of sensor sensitivity, response time, and dynamic range by varying fiber composition and coagulation methods (e.g., ethanol vs. ionic coagulation).
• Dynamic Vapor Sorption analysis to understand sorption-desorption kinetics.

Main Results:

• Biopolymer optical fibers demonstrated quantitative relative humidity (RH) sensing up to 0.33 dB/%RH.
• The sensitivity of these biopolymer optical fibers is comparable to or exceeds existing optical sensors and surpasses capacitance-based humidity sensors.
• Ethanol coagulated composite fibers showed a 6-fold increase in sensitivity compared to ionically coagulated fibers.
• Humidity sensing performance was found to be insensitive to temperature variations.
• Fiber composition and coagulation methods significantly influence sensitivity, response time, and dynamic range.

Conclusions:

• Fully biopolymer optical fibers enable quantitative sensing of relative humidity (RH).
• These sustainable optical fibers offer tunable and high-performance humidity sensing capabilities.
• The developed biopolymer optical fibers present a promising new platform for sustainable environmental monitoring sensors.