An array of flow units for controlling a flow of a fluid is disclosed. The flow units are arranged to have a lateral extension in a common lateral plane. A downstream side of a first flow unit is in fluid communication with an upstream side of a second flow unit to allow a flow of fluid to pass through the flow units. The flow units comprise first and second electrodes which are connectable to a voltage source. At least a portion of the first electrode has a maximum height in a direction parallel to the direction of the flow and a maximum gauge in a direction orthogonal to the direction of the flow, wherein the maximum height is larger than the maximum gauge to improve the pumping efficiency of the device. A method for controlling a fluid flow using the array is also disclosed.