Sensitivity of Pressure Sensors Enhanced by Doping Silver Nanowires

Abstract

We have developed a highly sensitive flexible pressure sensor based on a piezopolymer and silver nanowires (AgNWs) composite. The composite nanofiber webs are made by electrospinning mixed solutions of poly(inylidene fluoride) (PVDF) and Ag NWs in a cosolvent mixture of dimethyl formamide and acetone. The diameter of the fibers ranges from 200 nm to 500 nm, as demonstrated by SEM images. FTIR and XRD results reveal that doping Ag NWs into PVDF greatly enhances the content of β phase in PVDF. This β phase increase can be attributed to interactions between the Ag NWs and the PVDF matrix, which forces the polymer chains to be embedded into the β phase crystalline. The sensitivity of the pressure sensors agrees well with the FTIR and XRD characteristics. In our experiments, the measured sensitivity reached up to 30 pC/N for the nanofiber webs containing 1.5 wt% Ag NWs, which is close to that of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE), (77/23)]. This study may provide a new method of fabricating high performance flexible sensors at relatively low cost compared with sensors based on [P(VDF-TrFE), (77/23)].

Physico-Mechanical, Dielectric, and Piezoelectric Properties of PVDF Electrospun Mats Containing Silver Nanoparticles

“…However, the conformation of the β-phase is similar to that of the γ-phase, which causes some confusion because most of the β-phase bands are very close to those of the γ-phase. Previously, published work showed that the silver content to produce the highest β-phase content was 1.5% [18] and 10% [26]. Figure 3 shows the presence of β-and α-phases in the composites, and a clear reduction in the α-phase is observed with an increase in AgNPs content up to 0.4%, after which it again decreased.…”

“…Electrons -rich AgNPs interact with fluorine atoms in the PVDF forcing its chains to be in the β-conformation, thus increasing the β-phase content. Such interactions were confirmed by using X-ray photoelectron spectroscopy (XPS) [12], and UV and FTIR spectroscopy [18].…”

“…The work reported in this paper is aimed at complementing work done by three other groups [12,17,18] in addition to investigating the piezoelectric response of the PVDF/AgNPs electrospun mats. The first group [17] used 5 nm prepared AgNPs to enhance the antifouling properties of PVDF membranes and reported that the produced nanocomposite fibers became smoother and finer with addition of silver.…”

“…The diameter of the neat PVDF fibers was found to be about 250 nm, but with the silver particles, it increased to about 600 nm, and the thermal stability was enhanced after the addition of AgNPs. The third group [18] used AgNWs to enhance the sensitivity of pressure sensors. They reported that the fibers became rough with increasing the silver content, and the maximum β-phase content was observed for the 1.5% of AgNWs content.…”

“…Methods include solution casting of silver nanowires (AgNWs) [18] or Ag@TiO2 core@shell nanoparticles [19], surface immobilization in presence of poly(acrylic acid) [20], and exothermic decomposition of silver trifluoroacetate at 240 °C in molten PVDF [21]. Electrons -rich AgNPs interact with fluorine atoms in the PVDF forcing its chains to be in the β-conformation, thus increasing the β-phase content.…”