Functionalized paper with intelligent response to humidity

Abstract The functionalized soft materials are widely used in the field of flexible electronics devices, but there are still some challenges in preparing functionalized paper with sensitive reaction. In this paper, the functionalized paper with asymmetric wettability was developed by introducing nitrocellulose (NC) and multi-walled carbon nanotubes (MWCNTs) into the paper surface. This asymmetric wettability gives the paper sensitivity to relative humidity. When functionalized paper is placed in humid environment, CNTs can be folded and unfolded correspondingly in normal and reverse bending, which leads to the change of resistance on the paper surface. Therefore, the functionalized paper shows the induction to humidity factor through such bending deformation and resistance change. Interestingly, this paper can be further applied to flexible sensors for monitoring the relative humidity and breathing steam of various soils. In addition, the modifier and matrix are non-toxic, harmless and environmentally friendly, the preparation method of the coating is simple, and the functional paper can be reused for many times, which makes it possible for the functional paper to be applied in practice.