A mechanical stress activated interface and system comprising piezo-optical elements is described. The piezo-optical elements are fabricated from waveguides each having a core surrounded by a cladding material. The waveguides are supported on a substrate, thereby forming a thin sheet. The interface may take advantage of ambient light for illumination. Activation of the cores, such as by a user pressing the interface, may result in changes to their indices of refraction. More ambient light will be conducted along the lengths of the cores under stressed conditions than under non-stressed conditions. The output at the ends of the piezo-optical elements may be detected by light receiving elements. The output of the light receiving elements may be used by electronics coupled to a computer to determine which waveguides have been stressed, thereby determining the location of the touch on the interface. Methods for fabricating and using the interface are also described.