A microfluidic device enabling surface-enhanced Raman spectroscopy at chip-integrated multifunctional nanoporous...

Area of Science:

• Microfluidics
• Spectroscopy
• Analytical Chemistry

Background:

• Developing integrated microfluidic devices for simultaneous sample manipulation and detection is crucial for efficient analysis.
• Existing methods often require multiple steps for sample preparation and analyte detection, limiting speed and sensitivity.
• Nanoporous membranes offer potential for selective transport and enhanced detection substrates.

Purpose of the Study:

• To develop a novel three-dimensional (3D) microfluidic chip combining sample enrichment and Surface-Enhanced Raman Spectroscopy (SERS) detection.
• To utilize a nanoporous polycarbonate track-etched (PCTE) membrane for both electrokinetic sample enrichment and SERS detection.
• To demonstrate the chip's capability for rapid and sensitive analysis of analytes in complex matrices.

Main Methods:

• Fabrication of a 3D microfluidic chip integrating a PCTE membrane between microfluidic channels.
• Utilizing electrokinetic transport across the PCTE membrane for selective analyte enrichment.
• Employing the silver nanoparticle-coated backside of the PCTE membrane as a SERS substrate for analyte detection.
• Investigating Rhodamine B (RhB) for system validation using Raman microscopy and fluorescence video microscopy.
• Performing on-chip sample drying using an additional gas flow to enhance SERS signals.
• Analyzing melamine in whole milk as a proof-of-concept application.

Main Results:

• The integrated PCTE membrane successfully enabled both electrokinetic sample enrichment and SERS detection.
• The device demonstrated efficient analyte extraction and removal of interfering compounds from a complex food sample (whole milk).
• A limit of detection for 1 ppm melamine in milk was achieved using the developed SERS substrate and microfluidic system.
• On-target sample drying significantly enhanced the SERS signal intensity.

Conclusions:

• The developed 3D microfluidic chip provides a rapid (within 15 min) and integrated platform for sample clean-up and sensitive SERS detection.
• The device's ability to combine electrokinetic transport with a nanoporous SERS substrate offers a versatile approach for analyzing chemical and biological analytes.
• This technology holds promise for sensitive and selective on-chip analysis of complex samples.