Flexible Thin-Film Temperature Sensors on Upcycled Polyethylene Terephthalate (PET) Substrates for the Circularity of Economy.

The use of plastics for daily life applications keeps rising rapidly making these polymers a material of choice in many fields, including electronics. Nevertheless, the pollution generated from the fabrication, usage and disposal of plastics has become an environmental problem that is impacting most of the ecosystems in our planet. Efforts are being made to reduce the impact plastics have in nature, with recycling and upcycling as promising approaches that not only reduce the harm plastics to the biosphere, but also help in developing a circular model for the usage of these organic polymers. In this work, polyethylene terephthalate (PET) was recycled from commercial beverage bottles to create a sustainable substrate for the fabrication of thin-film electronics. As an application for the substrate, temperature sensors were developed and their response was analyzed over a temperature range from 5 degrees C to 65 degrees C with a temperature coefficient resistance (alpha) = 0.002 degrees C-1, used to measure the temperature of commercial bottle beverages. The development of these substrates provides a second life to the PET from bottles, paving the way for the sustainable and circular usage of plastic as substrates for thin-film electronic devices and a reduction of the negative effects their presence and footprint have in nature.