Graphene-PEDOT: PSS Humidity Sensors for High Sensitive, Low-Cost, Highly-Reliable, Flexible, and Printed Electronics

Abstract

A comparison of the structure and sensitivity of humidity sensors prepared from graphene (G)-PEDOT: PSS (poly (3,4-ethylenedioxythiophene)) composite material on flexible and solid substrates is performed. Upon an increase in humidity, the G: PEDOT: PSS composite films ensure a response (a linear increase in resistance versus humidity) up to 220% without restrictions typical of sensors fabricated from PEDOT: PSS. It was found that the response of the examined sensors depends not only on the composition of the layer and on its thickness but, also, on the substrate used. The capability of flexible substrates to absorb the liquid component of the ink used to print the sensors markedly alters the structure of the film, making it more porous; as a result, the response to moisture increases. However, in the case of using paper, a hysteresis of resistance occurs during an increase or decrease of humidity; that hysteresis is associated with the capability of such substrates to absorb moisture and transfer it to the sensing layer of the sensor. A study of the properties of G: PEDOT: PSS films and test device structures under deformation showed that when the G: PEDOT: PSS films or structures are bent to a bending radius of 3 mm (1.5% strain), the properties of those films and structures remain unchanged. This result makes the composite humidity sensors based on G: PEDOT: PSS films promising devices for use in flexible and printed electronics.

A Review on Printed Electronics: Fabrication Methods, Inks, Substrates, Applications and Environmental Impacts

“…Various printed sensors are reported in the literature, e.g., carbon nanotube (CNT) based gas sensors [13], graphene-poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) humidity sensors [48], PEDOT:PSS based temperature sensors [49,50] and active matrix sensor arrays printed on flexible substrate comprising organic TFTs, organic photodiodes [13]. Recent developments on organic inks and lignocellulosic substrates have demonstrated the printability of biocompatible and/or recyclable sensing devices.…”

Capacitance and Resistivity Measurements of Polythiophene /Metallic Nanoparticles-based Humidity Sensors

“…The response time can be defined as the time required for a sensor output to adjust to 90% of its final settled value from its previous state. The sensor's recovery time is defined as the time required for the sensor output to decrease to 10% of the final settled value [18]. The values of response and recovery time for each sensor are illustrated in Table-1.…”

Progress in wearable electronics/photonics—Moving toward the era of artificial intelligence and internet of things

“…To address the power consumption and system integration issues in the chemical/gas sensors, the combination of self‐powered ability and flexibility in the sensor has attracted increasing research interests recently. For example, to accurately evaluate the wellbeing conditions of a person, a smart and multifunctional textile based on a simple dip‐coating method is illustrated in Figure 2D 104,105 . It is shown that a maximum output power density of 2 Wm −2 can be realized with a polymer‐coated textile, which also possesses good CO 2 sensing response.…”