Optofluidic microbial sensors based on whispering gallery mode resonators

Overview

This solution offers a label-free optical detection platform for microbial contamination in aqueous solutions, based on Whispering Gallery Mode (WGM) resonator technology. WGM resonators are microscale optical structures that trap light along their curved surfaces; when microbial cells bind to the sensing surface, the effective refractive index changes, producing measurable shifts in the resonance signal. These shifts reveal the presence, concentration, and potentially the viability of contaminating microorganisms without the need for fluorescent or chemical labels.

The platform addresses critical needs in pharmaceutical manufacturing, clinical diagnostics, dialysis safety, and environmental water monitoring, where rapid and reliable detection of microbial contamination is essential. Two product versions are envisioned: a professional unit for manufacturing sites and hospitals, and a portable unit for patient home use.

Technical specifications

• Sensing mechanism: Whispering Gallery Mode resonators detect refractive index changes caused by microbial binding events on the sensor surface.
• Optofluidic design: Analyte solution flows through the core of the WGM sensor, enabling direct contact between the sample and the sensing surface.
• Self-referenced detection: Nanoparticle binding splits a WGM into two spectrally shifted resonance modes through light scattering, providing a built-in reference for improved measurement accuracy.
• Surface functionalization: Sensor surfaces will be coated with target-specific agents to capture bacterial cells selectively.
• Benchmarking: qPCR assays will be used to validate and quantify the relationship between organism concentration and detected optical signals.
• Target organisms: Initial validation will focus on Escherichia coli, Pseudomonas aeruginosa, and Ralstonia spp. in Millipore water, with subsequent testing in saline and dialysis solutions.
• Sensor geometry optimization: Numerical simulation will be used to tailor sensor geometries for bacterial cell detection and counting.

Technology readiness level

The technology is currently at an early-to-mid stage of development. Proof-of-concept has been established through nanoparticle detection and through experimental detection of Bovine serum albumin molecules in phosphate-buffered saline, where binding events produced measurable redshifts in WGM resonances. Future validation efforts include developing a WGM sensor specifically tailored for bacterial cell detection, benchmarking performance in saline and dialysis solutions, and building two prototype versions for professional and portable use cases. The research team is actively advancing toward prototype development and eventual commercialization.