The Measurement of Diffusion Coefficient Using Nanofluidic Channels

The behavior of molecules confined within nanochannels may provide new insight into important chemical and biological mechanisms. As such, the ability to measure the diffusion coefficient of molecules accurately and rapidly is critical. Toward this end, we demonstrate a new method for measuring the diffusion coefficient of analytes in nanoscale environments. Based on nanoscale electrokinetic transport theory, a numerical simulation was developed to determine the spatial concentration of analyte within a nanofluidic T-shaped channel for a given Peclet number. The resulting concentration profiles were compared to experimental data to determine the Peclet number that gives the minimum least-square error. Using this approach, the diffusion coefficient of sodium fluorescein was measured and found to be within the error of previously published values. This method is envisioned to be a novel analytical tool to rapidly and accurately measure diffusion coefficients of small analytes, and to measure the effective diffusion coefficients of more complex species such as DNA and peptides when confined within a nanochannel.