Transverse solute dispersion in microfluidic paper-based analytical devices (μPADs)

Area of Science:

• Analytical Chemistry
• Microfluidics
• Materials Science

Background:

• Microfluidic paper-based analytical devices (μPADs) are crucial for point-of-care diagnostics.
• Efficient molecular and particle transport between flow streams is vital for μPAD operations like mixing and dilution.
• Understanding transverse dispersion is key to optimizing μPAD performance.

Purpose of the Study:

• To quantitatively evaluate transverse analyte dispersion in μPADs using theoretical and experimental approaches.
• To determine the factors influencing dispersion width, including fluid velocity, analyte properties, and paper microstructure.
• To provide insights for rationalizing and improving the design of μPAD components.

Main Methods:

• Theoretical modeling of transverse dispersion.
• Experimental measurement of Brownian diffusion and mechanical dispersion coefficients.
• Capillary-driven flow experiments on μPADs.
• Analysis of dispersion width in relation to flow parameters and analyte characteristics.

Main Results:

• Dispersion width is independent of fluid velocity and analyte properties.
• Transverse dispersion is primarily determined by the dispersivity coefficient, a property of the paper microstructure.
• Paper-based mixers and concentration gradient generators can outperform conventional microchannels.

Conclusions:

• The paper microstructure dictates transverse dispersion in μPADs, offering a new design paradigm.
• Optimized designs for mixers and gradient generators are possible, enhancing efficiency.
• Separation devices like H-filters require careful engineering on paper due to mechanical dispersion effects.