Pressure driven transport in nanofluidic channels

The nanoscale represents a fundamentally new regime for lab-on-a-chip type fluidic systems, because it is the typical length scale across which electrostatic forces are mediated. To understand how ionic liquids and charged objects can be manipulated in nanofluidic devices, a fundamental understanding about the structure of the electrostatic double layer and the mechanisms that govern the effective surface charge is needed. These topics were experimentally investigated using the method of streaming currents through individual well-defined nanochannels. The first part of this Ph. D. work contains measurements of the effective surface charge under various ionic conditions including multivalent ions, for which the effective surface charge was found to change sign. The second part discusses the efficiency of electrical power generation by means of streaming currents, both theoretically and experimentally. From these measurements we also obtained quantitative information on the so-called Stern layer conductance. Finally, we studied the effect of confinement on the pressure driven transport of DNA polymers. Our results suggest new possibilities for DNA separation in nanofluidic devices.Applied Science