Eur. Phys. J. E (2022) 45: 56
https://doi.org/10.1140/epje/s10189-022-00211-4

Regular Article - Flowing Matter

Analysis of a microfluidic device for diffusion coefficient determination of high molecular weight solutes detectable in the visible spectrum

¹ Grupo de Medios Porosos, Facultad de Ingeniería, Universidad de Buenos Aires, Av. Paseo Colón 850, 1063, Buenos Aires, Argentina
² Instituto de Ciencias, Universidad Nacional de General Sarmiento, Juan M. Gutiérrez 1150, B1613GSX, Los Polvorines, Provincia de Buenos Aires, Argentina
³ Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, C1425FQB, Buenos Aires, Argentina

^c adonofrio@conicet.gov.ar

Received: 29 January 2022
Accepted: 9 June 2022
Published online: 25 June 2022

Abstract

We developed a procedure to measure diffusion coefficients using microfluidic devices that contributes to the transport analysis of high molecular weight solutes with low diffusion coefficient. This procedure allows a quick determination of diffusion coefficients and a precise evaluation of measurement errors. Making use of color variation of a pH indicator, we determined its diffusion coefficient in its own solvent (water). The value obtained was compared with previously published ones and was found to be similar to those cited. The microfluidic device has a serpentine-shaped channel that allows monitoring the solution evolution in different regions of the path in a single visual field without the need to move the camera or the microchip. This kind of device also allows the spatial and temporal tracking of the diffusion process. The solution color intensity is used to determine solute concentration; therefore, this method presents an advantage compared to those based on fluorescence detection. A complete analysis of the diffusive behavior along the channel path was performed in order to test the accuracy of these kinds of methodologies. This analysis can be used with similar devices, and the techniques employed for diffusion analysis can be applied to a µTAS-type microfluidic platform, allowing obtain variations of the diffusion coefficient as a function of time due to variations in external factors, e.g., temperature, etc.