Adapting Taylor Dispersion to Measure the Dispersion Coefficient of Electrolyte Solutions via an Accessible...

The field of microfluidics has become increasingly prominent as it allows for rapid and precise control of fluids and particles, making it easier to synthesize compounds and separate mixtures. We perfected an accessible, repeatable microscale adaptation of the Taylor Dispersion experiment using microchannels fabricated in-house with a desktop craft cutter. The starter cost of this fast and accessible microfluidics xurography technique is approximately 300 USD, orders of magnitude lower than typical photolithography methods. Pressure-driven laminar flow from a programmable syringe pump transports an injected tracer solution downstream in the microchannel, where a digital single-lens reflex (D-SLR) camera with a macro lens captures the tracer concentration evolution over time at a fixed location. Using this experimental platform, we can compute the diffusion coefficients for single-species passive tracers under varying experimental conditions. We then extended the protocol to electrolyte mixtures, observing preliminary evidence of diffusivity changes arising from nontrivial ion-ion coupling effects. This accessible experimental method provides a practical tool for probing multispecies transport and offers insights into the complex interactions governing ionic mobility.