The present invention relates to a data storage device comprising: a polymer layer for storing data in the form of topographic features; a substrate comprising a conductor, a first surface of the polymer layer being provided on the substrate; and at least one probe which, when the device is in use, interacts with a second surface of the polymer layer, wherein, when in use, the data storage device is operable to apply a first electrical potential to the at least one probe relative to the substrate, thereby to cause a protrusion to be formed on the second surface of the polymer layer.