Heating/ethanol-response of poly methyl methacrylate (PMMA) with gradient pre-deformation and potential temperature sensor and anti-counterfeit applications

In this paper, the heating/ethanol-response of a commercial poly methyl methacrylate (PMMA) is investigated. All PMMA samples are pre-deformed by means of impression (surface compression with a mold) to introduce a gradient pre-strain/stress field. Two types of molds are applied in impression. One is a Singaporean coin and the other is a particularly designed mold with a variable protrusive feature on top. Two potential applications - temperature sensors to monitor overheating temperatures and anti-counterfeit labels with a water-mark that appears only upon heating to a particular temperature - are demonstrated. Since the heating-responsive shape memory effect (SME) is an intrinsic feature of almost all polymers, other conventional polymers may be used in such applications as well.