Microfluidic discharge-based optical sources for detection of biochemicals

Area of Science:

• Biophotonics
• Analytical Chemistry
• Microfluidics

Background:

• Microfluidic systems offer advantages for biochemical analysis.
• Optical excitation is crucial for fluorescence-based detection.
• Developing compact and tunable light sources for microfluidics is an ongoing challenge.

Purpose of the Study:

• To report a novel discharge-based optical source for biochemical fluorescence detection in microfluidic systems.
• To demonstrate the efficacy of this source for exciting fluorescence in l-tryptophan and DNA samples.
• To present a microchip integrating the optical source, sample reservoir, and filters.

Main Methods:

• A microfluidic wavelength-tunable optical source was integrated onto a stacked microchip.
• The optical source utilizes a discharge struck in ambient air between a metal anode and a liquid-cathode cavity.
• The liquid cathode was doped with metal salts (e.g., barium chloride, lead(II) nitrate) to achieve specific emission wavelengths for excitation.

Main Results:

• The system successfully excited fluorescence in l-tryptophan and DNA samples (labeled with SYBR green dye).
• Specific emission lines (e.g., 454/493 nm for DNA, 280 nm for tryptophan) were generated using doped liquid cathodes.
• The fluorescence signals from the samples were compared to reference data, showing efficacy.

Conclusions:

• The developed discharge-based optical source is effective for exciting biochemical fluorescence in microfluidic systems.
• This technique allows for wavelength tunability by selecting appropriate metal salts in the liquid cathode.
• The system holds potential for analyzing other fluorophores by customizing the cathode composition.