A nanochannel-based concentrator utilizing the concentration polarization effect

This study develops a microfluidic device comprising two microchannels connected by a nanochannel in which the sample is concentrated via an ionic depletion effect. Using Rhodamine 6G dye for visualization purposes, it is shown that through an appropriate manipulation of the external potentials applied to the reservoirs of the device, an ionic depletion region with an electrical conductivity around 50 times lower than that of the buffer solution can be induced on the anodic side of the nanochannel. Furthermore, via an appropriate time-based switching of the external electrical potentials, the sample species can be concentrated close to the conductivity ratio within an interval of 1 min. Finally, it is shown that by varying the configuration of the electrical potentials applied to the device reservoirs, the concentrated sample can be delivered either to a single outlet reservoir or to multiple reservoirs.