Applying an electric field to a device via a field-shaping electrical interface region

A device 1 comprises a conducting volume 2 such as a channel in a micro-fluidic chip and an electric field applying assembly 4 such as an array of spaced electrodes adapted to generate an electric field having a discrete electric field profile. The device 1 further provides an electrical interface region 3 comprising at least an ionically conductive material arranged adjacent to and in contact with the conducting volume 2. The interface region 3 is provided between the conducting volume 2 and the electric field applying assembly 4 such that the discrete electric field is applied to the material by the electric field applying assembly 4 at a location spaced from the conducting volume 2. The discrete electric field applied by the electric field applying assembly 4 is smoothed by the electrical interface region 3 so that the electric field profile established within the conducting volume 2 is substantially continuous. The device 1 may be an electrophoresis device for sorting and sequencing ...