(262ab) Remote Read-out System for Thermal Barcode Based on Phase Change Materials

Covert thermal barcode consists of a series of phase change materials (PCMs) that have high heats of fusion and different melting temperatures. This type of barcode is a promising tool for the protection of identities and item recognition. Paper-based covert thermal barcodes composed of the four types of PCMs: stearic acid, palmitic acid, lauric acid, and icosane were developed with particular sequences. Traditionally, a differential scanning calorimetry (DSC)-based decoding system is used to decode the barcode but is time-consuming and has low-throughput¹. A remote read-out system using an infrared thermal camera was developed for a fast and easy alternative. The infrared thermal camera is non-contact, high resolution, high-throughput, and repeatable compared with DSC. The camera recorded the temperature variation during the melting and cooling processes of the four types of PCMs. The melting and freezing points were determined through the analysis of temperature variation curves produced. After mathematical smoothing and differencing, rates of temperature variation were obtained and the peaks generated from the sudden change in temperature rate pinpointed the exact melting temperatures. Thus, the PCMs were distinguished by their melting temperatures and three thermal barcodes were successfully decoded. This paper demonstrated that the infrared thermal camera system is a promising method to decode thermal barcodes and simultaneously analyze other thermal properties of materials.