Multilevel Frequency-Specific Information Storage Using Engineered Electromechanical Resonances in Piezoelectric Wafer Arrays

Multilevel information storage methods have the potential for increasing storage density and improving information security through obfuscation. Taking inspiration from the color quick response codes, we have developed a method for encoding layers of information in an array of thin piezoelectric wafers. Information storage is accomplished by altering the size of the circular polarization domain of individual wafers to engineer the response of the electromechanical resonances. By using this approach, we can store one layer of information per electromechanical resonance. In this study, we experimentally demonstrate this approach on a 20-element piezoelectric wafer array with up to two layers of information storage using binary encoding. We first discuss the relevant theory behind the proposed approach and the method for designing the polarization profiles for these wafer arrays to enable multilevel information storage. The effect of the size of the polarization domain on the strength of the electromechanical resonances and optimal size to enhance/suppress these resonances is discussed. Last, we describe how the proposed approach could be used to encode four or more layers of frequency-specific information. The proposed technology finds application in embedded barcodes, product tags, tamper-evident seals, and other secure applications such as shipping sensitive materials/containers.