Living algae detection with a PDMS-liquid chlorophyll fluorescence microfluidic chip filter and a smartphone

Area of Science:

• Biophotonics
• Microfluidics
• Optical Engineering

Background:

• Integrating optical filtration into microfluidic devices simplifies detection systems.
• Smartphone-based detection offers portable and accessible analytical capabilities.
• Accurate detection of living algae is crucial for environmental monitoring and research.

Purpose of the Study:

• To develop a polydimethylsiloxane (PDMS) microfluidic chip filter for transmitting chlorophyll fluorescence and blocking visible light.
• To enable smartphone-based detection of living algae using the integrated optical filter.
• To optimize dye concentrations and material thicknesses for effective optical filtering.

Main Methods:

• Fabrication of a PDMS microfluidic chip by sealing crystal violet solution within a PDMS layer atop a Sudan II-doped PDMS slab.
• Spectrum measurements to determine optimal dye concentrations and thicknesses for crystal violet and Sudan II-doped PDMS.
• Development of a smartphone-based imaging platform incorporating the microfluidic chip for algae detection.

Main Results:

• The developed microfluidic chip filter exhibits a cut-on wavelength of approximately 625 nm.
• High transmittance (up to 95%) was achieved in the chlorophyll fluorescence range (650-710 nm).
• Optimal performance was achieved with 25 mg L⁻¹ Sudan II-doped PDMS (3 mm thickness) and 2 mg L⁻¹ crystal violet solution (0.3 mm thickness).

Conclusions:

• The integrated PDMS microfluidic chip effectively filters optical wavelengths, enabling sensitive chlorophyll fluorescence detection.
• Smartphone-based living algae detection using this device yielded results comparable to commercial filters.
• This technology offers a simplified and portable solution for algae detection in various applications.