Electrokinetic micromixing of charged and non-charged samples near nano-microchannel junction

A nano-microchannel flow mixer comprising a polydimethylsiloxane (PDMS) microchannel and a Nafion nanoporous membrane is fabricated. It is shown that when an electric field is applied across the device, an ion enrichment/ion depletion effect occurs near the nano-microchannel junction. The mixing performance of the proposed device is examined for three different samples, namely fluorescein (negatively charged), Rhodamine 6G (positively charged), and Rhodamine B (electroneutral). It is shown that a mixing effect is obtained only for the Rhodamine B solution. Thus, it is inferred that nano-microchannel devices such as that presented in this study and those presented in the literature are unsuitable for biomolecule detection applications since such molecules are generally charged.