Doped nafion-layered double hydroxide nanoparticles as a modified ionic polymer metal composite sheet for a high-responsive humidity sensor

In this paper, a novel Ionic Polymer Metal Composite (IPMC) has been fabricated by chemical electroless plating integrated with doping Layered Double Hydroxide (LDH) nanoparticles in the nafion polymeric matrix. Platinum, as a noble metal, was used for electrode deposition of the prepared doped nafion and successfully act as a high-quality electrode to transfer electrical signal. This IPMC, in fact, is a smart material suggesting to acts as a high responsive mechanical humidity sensor in biomedical devices since it produced a remarkably higher voltage with higher sensitivity and responsivity in comparison to the previous IPMC humidity sensors in literature. LDH nanoparticles own a layered ionic structure, which makes them highly hydrophilic. This property increases the water uptake of the IPMC. By increasing the penetration of water molecules in the nafion channels, the separation of positive and negative charges becomes easier and leads to higher and faster humidity sensing application. The humidity sensing applications of undoped and LDH-doped IPMC fabricated by facile chemical plating method were measured and compared at different bending angles. It was found that 1% doped nafion sheet had the highest water uptake of 30%, and consequently better humidity sensing compared to the undoped, 0.5%, 1.5%, 2% and 3% doped nafion. This means that doping concentration and modification has an optimized value.