Naked-Eye Coulometric Sensor Using a Longitudinally Oriented Ag Band Electrode in a Microfluidic Channel

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Microfluidics

Background:

• Traditional analytical methods often require complex instrumentation.
• Developing simple, visual detection platforms is crucial for point-of-care diagnostics.
• Coulometric sensing offers high sensitivity but typically lacks direct visual output.

Purpose of the Study:

• To develop a microfluidic coulometric sensing platform with an integrated visual readout.
• To demonstrate the correlation between analyte concentration and visual changes on a silver electrode.
• To validate the platform's performance with different analytes and concentrations.

Main Methods:

• Fabrication of a microchannel device with gold working and silver band counter electrodes.
• Utilizing the electro-oxidation of silver as a visual indicator complementary to the analyte reduction reaction.
• Correlating the visual decrement of the silver electrode with analyte concentration and flow rate.

Main Results:

• The silver electrode visually decreased in proportion to analyte concentration (0.1-2.5 mM p-benzoquinone).
• Linear correlation observed between silver electrode depletion and analyte feeding rate (1.0-75.0 μL min(-1)).
• Successful detection of horseradish peroxidase (HRP)-avidin in the range of 0.1-3.0 μg mL(-1).

Conclusions:

• The developed platform provides a simple, visual readout for coulometric sensing.
• The visual detection mechanism is reliable and correlates linearly with analyte concentration and flow rate.
• This technology holds potential for developing portable and user-friendly analytical devices.