Fabrication and Characterization of Humidity Sensors Based on Graphene Oxide–PEDOT:PSS Composites on a Flexible Substrate Romero Maldonado, Francisco Javier Rivadeneyra Torres, Almudena Becherer, Markus Morales Santos, Diego Pedro Rodríguez Santiago, Noel Flexible Electronics Graphene oxide Humidity PEDOT:PSS Screen-printing Sensor Supplementary Materials The following are available online at https://www.mdpi.com/2072-666X/11/2/148/s1, Figure S1: Actual view of one of the flexible RH sensors presented in this work, Figure S2: Absolute value of the impedance as a function of the relative humidity measured at different frequencies for both layout 1 (10 kHz (a) and 100 kHz (c)) and layout 2 (10 kHz (b) and 100 kHz (d)) using GO and the hybrid GO/PEDOT:PSS composites as sensitive layers, Figure S3: Equivalent parallel resistance and capacitance for layout 1 (W = 115 µm, i = 225 µm) at different frequencies using GO and the hybrid GO/PEDOT:PSS composites as sensitive layers, Figure S4: Sensitivity as a function of the frequency for the two layouts considered in this work as well as the three different sensitive layer. In this paper, we present a simple, fast, and cost-effective method for the large-scale fabrication of high-sensitivity humidity sensors on flexible substrates. These sensors consist of a micro screen-printed capacitive structure upon which a sensitive layer is deposited. We studied two different structures and three different sensing materials by modifying the concentration of poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) in a graphene oxide (GO) solution. The results show that the aggregation of the PEDOT:PSS to the GO can modify its electrical properties, boosting the performance of the capacitive sensors in terms of both resistive losses and sensitivity to relative humidity (RH) changes. Thus, in an area less than 30 mm2, the GO/PEDOT:PSS-based sensors can achieve a sensitivity much higher (1.22 nF/%RH at 1 kHz) than other similar sensors presented in the literature which, together with their good thermal stability, time response, and performance over bending, demonstrates that the manufacturing approach described in this work paves the way for the mass production of flexible humidity sensors in an inexpensive way. 2020-04-15T10:03:11Z 2020-04-15T10:03:11Z 2020-01-29 journal article Romero, F.J.; Rivadeneyra, A.; Becherer, M.; Morales, D.P.; Rodríguez, N. Fabrication and Characterization of Humidity Sensors Based on Graphene Oxide–PEDOT:PSS Composites on a Flexible Substrate. Micromachines 2020, 11, 148. [doi:10.3390/mi11020148] http://hdl.handle.net/10481/61225 10.3390/mi11020148 eng EC/H2020/794885-SELFSENS http://creativecommons.org/licenses/by/3.0/es/ open access Atribución 3.0 España MDPI