AUTHOR=Falco Aniello , Marín-Sánchez Antonio , Loghin Florin C. , Castillo Encarnación , Salinas-Castillo Alfonso , Salmerón José F. , Rivadeneyra Almudena 

TITLE=Paper and Salt: Biodegradable NaCl-Based Humidity Sensors for Sustainable Electronics

JOURNAL=Frontiers in Electronics

VOLUME=Volume 3 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/electronics/articles/10.3389/felec.2022.838472

DOI=10.3389/felec.2022.838472

ISSN=2673-5857

ABSTRACT=Flexible and thin-film humidity sensors are currently attracting the attention of the scientific community due to their portability and reduced size, really useful for several application in Internet o Things (IoT) industry. Furthermore, in order to perform an efficient and profitable mass production, it is necessary to develop cost-effective and reproducible fabrication process and materials. Green fabrication methods and biodegradable materials would also allow to minimize the environmental impact and to create a sustainable IoT development. In this paper, a humidity flexible sensors based on a common salt (NaCl) sensing layer are  reported. Our sensors and the fabrication techniques employed such as dip and spray coating provide a biodegradable, low cost and highly reproducible device. One of the sensors reported presents a typical resistive behaviour from 40% RH up to 85% RH with a sensitivity of -0.21 (Z/%RH). The performance of the sensors obtained with several fabrication techniques is studied and reported at multiple frequencies from 100 Hz to 10 MHz, showcasing its versatility and robustness.