Fbg-based optical chlorine sensor using cellulose acetate coating

Overview

This solution offers an optical sensing approach for detecting chlorine concentration in water using Fiber Bragg Gratings (FBG) coated with cellulose acetate (CA) polymer. When chlorine interacts with the CA coating, it induces mechanical stress and strain changes along the grating, which directly shifts the reflected optical wavelength. This wavelength shift encodes chlorine concentration into a measurable optical signal, enabling reliable detection without electronic interference.

The technology leverages the inherent sensitivity of FBGs to picostrain-level axial changes, combined with the chemical reactivity of cellulose acetate to chlorine. Potential applications include water quality monitoring for municipal water treatment, industrial process control, swimming pool management, environmental monitoring, and any setting requiring accurate chlorine detection. Unlike conventional electrochemical chlorine sensors, this optical approach provides total immunity to radio frequency interference, ground loops, and electrostatic discharge.

Technical specifications

Core technology components:

• Fiber Bragg Grating (FBG): An optical fiber component that reflects specific wavelengths of light determined by the periodicity of its index of refraction modulation. Small mechanical strain along the grating shifts the resonant peak wavelength.
• Cellulose acetate (CA) coating: A polymer layer applied over the FBG that reacts mechanically with chlorine, converting chemical concentration into physical strain on the grating.
• Optical wavelength shift detection: The chlorine-induced strain produces a measurable shift in reflected spectrum, directly correlating to chlorine concentration.

Key features and capabilities:

• Immunity to electromagnetic interference, radio frequency, ground loops, and electrostatic discharge
• High sensitivity to small axial strain levels (picostrain range)
• Real-time optical encoding of chemical concentration into wavelength shifts
• Builds on demonstrated FBG expertise in temperature measurement, particle displacement/velocity/acceleration, and aqueous ion chemical concentration sensing

Relevant prior expertise:

• Development of FBG distributed measurement systems for temperature, mechanical parameters, and aqueous ion chemical concentrations
• Characterization of optical materials including Lithium Niobate (LiNbO3)
• Processing of cellulose from lignocellulosic biomass and conversion into chemical derivatives

Technology readiness level

This technology is at an early research and development stage. The team has not yet conducted a specific preliminary study for detecting chlorine concentration using FBG-CA sensors, but possesses extensive relevant expertise in FBG sensing, optical materials characterization, and cellulose chemistry.

Planned validation activities:

• Characterize the interaction between cellulose acetate polymers and chlorine
• Implement the CA-based polymer as a fiber mechanical buffer coating over the FBG
• Measure sensitivity and reproducibility of the device as a function of chlorine concentration in water
• Design a laboratory prototype sensor and measure its chlorine detection capability

Validation will be conducted using state-of-the-art nanotechnology clean room facilities at the University of Houston. The technology is currently at a concept-to-proof-of-principle stage and would benefit from collaboration with partners interested in water quality sensing, optical sensor development, or chemical detection applications.