Understanding the electrokinetic interaction between dynamically tunable nanofluidic channels connected in series.

The passage of an electric current through a permselective medium results a phenomenon termed concentration polarization (CP). This phenomenon has been the focus of intensive research, particularly regarding its relationship with microfluidic applications, e.g. on-chip desalination and enhanced biosensing sensitivity. These applications have been limited by a fixed geometry and properties of the permselective medium (i.e. nanochannel) which defines the location, intensity and length of the CP layer. The ability to dynamically tune the geometry of the permselective medium allows us to optimize existing processes and opens up new application possibilities. This is realized using pneumatically controlled microvalves where the formed gap between the elastically deformed membrane, which is controlled by external pressure chamber, and the microchannel, forms the ion permselective nanochannel. In contrast to previous studies of such a system, here we extend this approach to several individually addressable microvalves that are connected in series within the same microchannel. Such interaction between two or more dynamically formed nanochannels yields interesting results of both the transient and steady-state behavior of the CP layers and related electrical response.