Transient response of undulated microchannel-nanochannel interface device*

In this work we present a microchannel–nanochannel interface device with sinusoidal undulation of the interface. In the under-limiting region the response of a microchannel-nanochannel interface device is similar to an ion-selective membrane device with straight interface and exhibits a monotonic chronopotentiometric and chronoamperometric responses. Beyond the limiting current the ionic perm-selectivity of the nanochannel and electroconvection affect the transient response and result in a non-monotonic response. Specifically, in the chronoamperometric response for example, the non-ideal perm-selective nanochannel results in concentration-polarization within the nanochannel which contributes to a non-monotonic response (maximum), followed by another non-monotonic response (minimum) when electroconvection becomes strong enough to affect the depletion layer. The response strongly depends on the undulation of the interface, e.g. amplitude and wavelength, and the selectivity of the nanochannel.