Embodiments include a data input device and a portable electronic device including such a data input device. The data input device may include a key sensing mechanism and a solid material layer provided above the key sensing mechanism. The solid material layer may include a least one cavity that may go through the whole of the solid material layer. The cavity may include an electroactive polymer and two electrodes for providing a key that may be changed in shape based on an applied voltage. One embodiment may also allows the registering of inputs in the key sensing mechanism based on a user pressing down the electroactive polymer on the key sensing mechanism.