Miniaturized planar waveguide interferometric sensor for real-time water chlorine detection

Overview

This solution is a miniaturized, low-cost planar waveguide-based interferometric sensor developed for detecting chlorine and other chemicals in water. The technology addresses the need for rapid, direct measurement of water quality parameters without the use of consumable reagents. By coupling a chemically selective film to the waveguide surface, the sensor enables selective detection of target analytes such as free chlorine, total chlorine, chloramines, proteins, and whole organisms. The platform is designed for flexible deployment, supporting both mobile, in-container analysis with instant results and continuous in-situ monitoring with automatic data logging and remote communication.

Technical specifications

• Sensing principle: Planar waveguide interferometry that measures changes in the evanescent field caused by refractive index variations near the waveguide surface.
• Chemical selectivity: A tailored sensing film applied to the waveguide surface selectively responds to target chemicals, enabling direct and reversible detection.
• Sensitivity: Detection sensitivity on the order of 0.01 radians, corresponding to refractive index changes below 10⁻⁶ and analyte detection levels in the ppb to ppt range.
• Speed and reversibility: Fast response time with reversible measurements, allowing real-time monitoring without sample preparation.
• Reagent-free operation: Direct measurement eliminates the need for additional steps or consumable reagents.
• Component cost: Built largely from inexpensive, off-the-shelf components including a laser diode light source and CCD camera.
• Deployment flexibility: Configurable for portable point-of-use analysis or fixed-location in-situ monitoring with automated data logging and communication to a base site.
• Film versatility: Sensing films can be tailored to respond to a wide variety of chemicals beyond chlorine.

Technology readiness level

The sensor has been experimentally demonstrated for the detection of multiple chemicals, including free chlorine and chloramines, as well as biological targets such as proteins and whole organisms. Current and planned validation work focuses on three areas: (1) sensing film design and testing, including modification of existing chlorine-selective chemistry to enable total chlorine detection and characterization of sensitivity; (2) system re-engineering to meet customer requirements for size, power consumption, and usability; and (3) extensive laboratory testing to assess overall technology readiness. The platform is advancing toward deployment-ready configurations suitable for field and commercial use.