Abstract: A valve for controlling flow of a primary fluid in a primary flow channel is defined in a valve region by a deformable membrane. The primary flow channel includes a core in the valve region, and a housing which defines a void outside the primary flow channel in the valve region thereof. The valve includes a device for driving a displacement fluid into or out of the void or both, to vary the pressure difference across the deformable membrane between the primary flow channel and the void, and so as to vary the space that is available between the deformable membrane of the primary flow channel and the core for the primary fluid to flow along the primary flow channel. A pump can include a valve as described above as a driver valve, together with an inlet valve and an outlet valve.

Abstract: A valve for controlling flow of a primary fluid in a primary flow channel comprises a valve fluid channel, and a membrane of a porous dielectric material located in the channel so as to divide the channel into an inlet part and an outlet part and so that valve fluid flowing between the inlet and outlet parts flows through the said membrane. First and second electrodes are located for electrical communication with valve fluid in the inlet and outlet parts respectively of the valve fluid channel for application of an electric potential across the membrane in order to promote electro-osmotic flow of valve fluid through the membrane.