Highly Sensitive and Stable Humidity Sensor Based on the Bi-Layered PVA/Graphene Flower Composite Film

Abstract

Two-dimensional (2D) materials and their composites have gained significant importance as the functional layer of various environmental sensors and nanoelectronics owing to their unique properties. This work reports for the first time a highly sensitive, fast, and stable humidity sensor based on the bi-layered active sensing area composed of graphene flower (GF) and poly (vinyl alcohol) PVA thin films for multifunctional applications. The GF/PVA humidity sensor exhibited stable impedance response over 15 days, for a relative humidity (RH) range of (40–90% RH) under ambient operating conditions. The proposed bi-layered humidity sensor also exhibited an ultra-high capacitive sensitivity response of the 29 nF/%RH at 10 kHz and fast transient response of 2 s and 3.5 s, respectively. Furthermore, the reported sensor also showed a good response towards multi-functional applications such as non-contact skin humidity and mouth breathing detection.

Self-Powered TENG with High Humidity Sensitivity from PVA Film Modified by LiCl and MXene

“…Moreover, as humidity rises, more hydrogen bonding occurs between water vapor and the −OH groups in PVA, leading to an increase in H ions that can hop between water vapor molecules through the Grotthuss mechanism. 35 To visually analyze the relationship between current density, RH, and the PVA/LiCl mass ratio, a threedimensional curved surface fitting was applied to the discrete point data of short-circuit current measured by TENGs (Figure 4c). According to the results, TENG-generated current density experiences a significant increase in high-humidity environments with a low PVA/LiCl mass ratio.…”

“…This is because the hydrophilic PVA film adsorbs or desorbs water-absorbing molecules in the humid atmosphere, changing the dielectric constant, which causes a change in the electrical response (i.e., impedance). Moreover, as humidity rises, more hydrogen bonding occurs between water vapor and the −OH groups in PVA, leading to an increase in H ions that can hop between water vapor molecules through the Grotthuss mechanism . To visually analyze the relationship between current density, RH, and the PVA/LiCl mass ratio, a three-dimensional curved surface fitting was applied to the discrete point data of short-circuit current measured by TENGs (Figure c).…”

Humidity-Responsive Antimicrobial Membranes Based on Cross-Linked Copolymers Functionalized with Ionic Liquid Moieties

“…For instance, noncontact switches have been investigated thoroughly as smart human–machine interfaces . Significant progress has been made recently in the development of humidity actuators/sensors using various materials such as natural polymers, − synthetic polymers, − and carbon-based materials. − The selection of polymeric materials to be used for the fabrication of a humidity sensor is determined by the degree of their affinity to water and their hydrophobic properties. A fine balance is necessary to achieve the desired sensing performance, i.e., high sensitivity, rapid response, rapid recovery, and low hysteresis.…”

A Flexible Strain Sensor with High Electrical Conductivity, Rapid Electrothermal Response, and High Strain Sensitivity for Real‐Time Monitoring of Human Joint Movement

“…[31] Notably, cellulose is one of the most abundant natural polymers and possesses high strength, large specific surface area, and high amphiphilicity, [32] and polyvinyl alcohol (PVA) is widely used in biosensors because of its favorable mechanical properties, biocompatibility, and degradability. [33,34] In particular, the hydroxyl groups from PVA interact with the hydroxyl groups from natural fibers to generate strong hydrogen bonds, allowing for the fabrication of "green" nanocomposite for industrial applications. [35] In addition, based on natural, degradable, flexible polymer substrates, currently multifunctional sensors with high strain sensitivity and rapid electrothermal response have not received as widely studied.…”