Abstract
Cellulose-based paper electronics is an attractive technology to meet the growing demands for naturally abundant, biocompatible, biodegradable, flexible, inexpensive, lightweight and highly miniaturizable sensory materials. The price reduction of industrial carbon nanotube (CNT) grades offers opportunities to manufacture electrically conductive papers whose resistivity is responsive to environmental stimuli, such as the presence of water or organic solvents. Here, a highly sensitive paper nanocomposite is developed by integrating CNTs into a hierarchical network of pulp fibers and nanofibrillated cellulose. The aqueous-phase dynamic web forming process enables the scalable production of sensory paper nanocomposites with minimal nanoparticle loss due to the tailored interfacial bonding between CNT and cellulose components. The resulting materials are applied as multifunctional liquid sensors, such as leak detection and wave monitoring. The sensitivity to liquid water spans an outstanding four orders of magnitude even after 30 cycles and 6-month natural aging, due to the hydroexpansion of the hierarchical cellulose network, which alters the intertube distance between neighboring CNTs. The re-organization of percolated CNTs modifies the electron transport in wet areas of the sheet, which can be predicted by an equivalent circuit of resistors for the rapid detection and quantification of various liquids over large surfaces.
Highlights
While a fifth of the world population lacks safe water, leaky pipes and wasteful irrigation systems are major contributors to water scarcity on the planet
Industrial grade hydroxyl-functionalized carbon nanotube (CNT) were selected over alternative fillers, such as helical CNTs (h-CNTs) and graphene nanoplatelets (GnPs), due to their relatively low cost (Table A1) and superior dispersion quality in aqueous cellulose nanofibrils (CNFs) (Fig. A2a), contributing to more uniform sheet formation and enhanced sensing perfor mance (Fig. A3)
Electron microscopy confirms the even distribution of nanoparticles in the paper without significant aggregation despite loadings as high as 15 wt% (Fig. 1b). This is attributed to the presence of CNFs playing two roles: (i) that of a dispersing agent for the hydrophobic CNTs and (ii) that of an interfacial reinforcing agent between the CNTs and the pulp fibers. The former role can be ascribed to the polarization of electrons in the sp2 CNT lattice induced by the fluctuations of counter-ions on the surface of the TEMPO-oxidized CNFs [14], which promotes the colloidal stabilization of CNT:CNF complexes in water by means of electrostatic repulsion and steric hindrance, as shown by absorption spectroscopy (Fig. A2b)
Summary
While a fifth of the world population lacks safe water, leaky pipes and wasteful irrigation systems are major contributors to water scarcity on the planet. The paper nanocomposites prepared at a CNT:CNF ratio of 2:1 yield the most uniform sheet resistance (Fig. 1f) compared to the other compositions tested (Fig. A5).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
