Cellulose nanofibers as substrate for flexible and biodegradable moisture sensors

Flexible and biodegradable electronics is attracting the interest of the Internet of Things industry. The necessity of sustainable development and environmental friendly electronic devices forces manufactures to reduce electronic wastes and toxic residues. Cellulose nanofibers are biodegradable and flexible materials suitable to build self supported film electronics and are seeing first employment in sensor fabrication. In this work, cellulose nanofibers based moisture sensors are reported, which are characterized at different working frequencies showing a good dependence with relative humidity (RH). A transparent and fully biodegradable moisture sensor was fabricated based on a PEDOT:PSS electrode showing a wide operation range from 20% to 85%RH, where CNF film acts as the sensing layer without any additional processing. In order to manufacture the sensor, a one-step fabrication method based on screen-printing was applied, which offers a more reproducible and cost-effective solution than others techniques. In addition, this method offers the possibility to easily redesign the sensor saving time and money. Thus, our work presents a versatile, transparent, self-supported film moisture sensor with a promising adaptability to the green-electronics industry.H2020-MSCA-IF-2017-794885-SELFSENSMAT2015-71117-RID2019-107022RJ-I00IJCI-2015-2388