Integrated refractive index optical ring resonator detector for capillary electrophoresis

Area of Science:

• Photonics and Microfluidics
• Optical Sensing Technology
• Analytical Chemistry

Background:

• Capillary electrophoresis (CE) requires sensitive detection methods for analyzing small sample volumes.
• Existing detectors often lack integration with microfluidic channels, limiting real-time monitoring.
• Label-free detection is desirable for simplifying sample preparation and analysis.

Purpose of the Study:

• To develop a miniaturized, multiplexed, on-capillary refractive index (RI) detector for CE applications.
• To integrate sensing capabilities directly into the capillary fluidic channel.
• To demonstrate label-free measurement, fluid transport, and flow analysis using the novel detector.

Main Methods:

• Utilized liquid core optical ring resonators (LCORRs) integrated into a glass capillary (approx. 100 µm diameter).
• Employed whispering gallery modes (WGMs) within the capillary to detect RI changes via evanescent field interaction.
• Demonstrated fluid transport and flow analysis using electro-osmotic flow and glycerol as a model system.

Main Results:

• Achieved label-free, real-time analyte concentration deduction with a sensitivity of 20 nm/RIU.
• Demonstrated a refractive index detection limit of 10⁻⁶ RIU.
• Validated the LCORR's capability for fluid transport and flow speed measurement.

Conclusions:

• The LCORR detector successfully integrates photonic technology with microfluidics for on-capillary analysis.
• This technology enables rapid sample analysis and flow profile monitoring, paving the way for high-throughput CE and lab-on-a-chip sensors.