A structure of a device, such as a surface coating, is composed of one or more materials that are arranged to change one or more characteristics in response to a stimulus, such as an electrical signal, a magnetic field, application of thermal energy, and so forth. The changed characteristics may include a tactile characteristic, a visual characteristic, or other type of characteristic that is perceivable by a user of the device. A state for the adjustable structure may be determined based on user preference data that is stored on the device or input by a user through a user interface. The state for the adjustable structure may also be automatically determined based on device motion, orientation, environment factors, and so forth.