Flow-through real-time optical sensor for acrylamide detection in drinking water

Overview

This solution addresses the need for continuous, real-time detection of acrylamide in drinking water at concentrations below WHO safety limits. Acrylamide is a probable human carcinogen that can form during industrial water treatment processes, making reliable low-level monitoring important for public health and regulatory compliance.

The sensor pairs Surface Enhanced Raman Scattering (SERS) nanoparticle substrates with a photonic grating to form an optical resonant cavity. This configuration concentrates Raman excitation light into a submicron gap, producing an intense plasmonic field within a flow-through sampling chamber. Because analyte molecules pass through the enhanced field rather than having to bind to the sensor surface, the device supports repeated, continuous use without single-use limitations typical of conventional SERS sensors.

The sensor is designed for in-situ deployment, requiring only an optical fiber connection for laser delivery and spectral readout, with no need for a separate onboard power source.

Technical specifications

Core approach:

• Couples a SERS nanoparticle substrate with a photonic grating to create a nanophotonic resonant cavity
• Concentrates and distributes Raman excitation laser energy uniformly onto the SERS active surface
• Generates the most intense plasmonic field in the submicron gap between the photonic grating and the SERS substrate
• Eliminates the requirement for acrylamide to physically associate with the SERS surface
• Creates a flow-through microcavity sampling chamber for continuous, real-time detection
• Operates with only an optical fiber connection for laser input and Raman spectral data output

Design validation completed:

• Computational modeling using COMSOL identified optimal photonic grating dimensions
• Quantitative evaluation confirmed the grating's ability to control and concentrate light energy
• SERS detection capability demonstrated at 0.1 nM acrylamide sensitivity based on published literature

Technology readiness level

The technology is at an early-to-mid stage of development. Computational modeling and design optimization have been completed, validating the photonic grating geometry and light-concentrating performance.

A six-month research plan is underway to advance the technology to a bench-top prototype, including fabrication and testing of the photonic grating with silver nanoparticle SERS substrates, assembly and testing of the flow-through cavity, construction of a standard curve to determine lower detection limits below 0.5 ppb, and optimization of the grating, substrate composition, or microfluidic structure as needed.