Development of flexible sensors using knit fabrics with conductive polyaniline coating and graphite electrodes

Abstract

The aim of this study was to develop flexible sensors with cotton and polyester knit fabrics as substrates coated with polyaniline (PAni) doped with hydrochloric acid or phosphoric acid. The deposition of PAni onto the knit, polymerization synthesis, and doping of the aniline monomer were performed via an in situ reaction. Graphite dispersion was used to obtain the electrodes of the sensors, which were prepared differently for each substrate. The main evaluation of the sensors was carried out in a humidity chamber under nitrogen (N2) with the application of drying and wetting cycles. Significant differences were observed in the responses of the sensory devices to humidity, according to the dopant and substrate types. In all tests, the sensor response to variations in the ambient conditions was very good, with a rapid response to changes in the relative humidity, a good sensitivity (up to 34%), and a high reversibility (ca. 70–100%). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44785.

Flexible Sensors—From Materials to Applications

“…PANI can become more conductive after proton doping or can decrease its charge carrier if gas molecules are absorbed. Its ability to change the conductivity is of interest for the fabrication of chemical and biological sensors [127][128][129][130][131]. PANI's base conductivity for an undoped sample was reported to be 5 × 10 -4 S/cm, and the highest conductivity observed was 109.04 S/cm for a sample doped with HNO 4 [132].…”

“…PANI's base conductivity for an undoped sample was reported to be 5 × 10 -4 S/cm, and the highest conductivity observed was 109.04 S/cm for a sample doped with HNO 4 [132]. PANI's conductivity can also be increased with the use of carbon materials such as graphene [125,129], rGO [130], graphite [126,128,129], graphene nano platelets (GNP) [129], or MWCNTs [133]. Despite its good electrical properties, PANI is used in composites due to its lack of stiffness (modulus = 1.3 GPa) [134].…”

“…This material also possesses a high infusibility, poor solubility and melting processability, and good adhesion, making PANI a material highly used as a coating on flexible surfaces [126]. The main methods for the preparation of composites are impregnation by wetting [118,123,127], spraying [133], electrodeposition [126,128,129,131], electronic polymerisation [125], and oxidative polymerisation [135]. Park et al [136] reported the fabrication of PANI nanofibres by potentiodynamic growth (Figure 4a) with a sheet resistance of 420 Ω/ .…”

“…Park et al [136] reported the fabrication of PANI nanofibres by potentiodynamic growth (Figure 4a) with a sheet resistance of 420 Ω/ . Materials such as sponges [127,130], cotton and polypropylene woven fabrics [133], cotton and polyester knit fabrics [128], or nano cellulose fibrils with high tensile modulus have been impregnated with PANI to sense humidity and gases [118]. This material can be either doped with hydrochloric acid (HCl) and phosphoric acid (H 3 PO 4 ) to improve the protonation [128], or functionalised with MWCNTs to obtain a resistance of 2280 kΩ and a bendability up to 240° [133].…”

“…Materials such as sponges [127,130], cotton and polypropylene woven fabrics [133], cotton and polyester knit fabrics [128], or nano cellulose fibrils with high tensile modulus have been impregnated with PANI to sense humidity and gases [118]. This material can be either doped with hydrochloric acid (HCl) and phosphoric acid (H 3 PO 4 ) to improve the protonation [128], or functionalised with MWCNTs to obtain a resistance of 2280 kΩ and a bendability up to 240° [133]. Impregnation of cellulose nanofibrils with PANI reported an improvement on their properties (conductivity 1.9 × 10 -2 S/cm and high thermal stability at 500 • C with a modulus of 5.4 GPa) [118].…”