Encapsulation of polyvinyl alcohol based flexible temperature sensor through spatial atmospheric atomic layer deposition system to enhance its lifetime

Printed organic sensors are of significant importance owing to their simplicity, low cost, easy fabrication and solution processability. However, organic sensors often suffer from the drawback of performance degradation when exposed to ambient environment. In this study, polyvinyl alcohol (PVA) is used as the functional layer of a temperature sensor and is encapsulated by aluminum oxide (Al2O3) deposited through spatial atmospheric atomic layer deposition system (SAALD). The encapsulating layer of Al2O3 was pure, atomically thin and highly reliable. Fabricated organic temperature sensor is based on a conductive and uniform interdigitated pattern deposited on a flexible polyethylene naphthalate substrate through advanced printing technology of reverse offset. Thin film of PVA is used as the temperature sensitive functional layer deposited through electrohydrodynamic atomization followed by Al2O3 encapsulation. The developed sensors were tested in the temperature range of 25 degrees C to 90 degrees C with relative humidity reaching up to 75% relative humidity. The obtained results exhibited that Al2O3 encapsulation deposited through SAALD significantly enhanced the linearity, repeatability, endurance (50 cycles), retention (2 months) and lifetime of PVA based temperature sensor as compared with the non-encapsulated sensor hence, protecting the organic device from performance degradation.