Preparation and properties of cellulose nanofibers/α‐zirconium phosphate nanosheets composite polyvinyl alcohol ion‐conductive organohydrogel and its application in strain sensors

Abstract

The poor mechanical and electrical properties and single function of conventional conductive hydrogels severely limit their application in flexible sensors. Here, a multifunctional nanomaterial composite high-strength hydrogel strain sensor was prepared by incorporating α-zirconium phosphate (α-ZrP) nanosheets with hydroxyl functional groups on the surface and cellulose nanofibers (CNFs) into a poly(vinyl alcohol) (PVA)matrix simultaneously, using a binary glycerol/water solution as the dispersion medium and a strategy of cyclic freeze-thawing followed by sodium chloride immersion. The experiments showed that CNFs and α-ZrP nanosheets can form hydrogen bonding interactions with PVA chains, which can synergistically improve the mechanical and electrical properties of the gels with little effect on its transparency, and the tensile strength and elongation at break of the gels can reach 2.42 MPa and 541%, respectively, and the ionic conductivity exceeds 7.65 mS/cm, while possessing a transmission rate of 87% at 600 nm visible light wavelength. In addition, the introduction of glycerol imparts the gel with remodeling, anti-freezing, and long-term stability. As a strain sensor, it has a linear sensing range of 0%-350% and high sensitivity (GF = 2.46), and the sensing gloves prepared based on it can accurately and stably recognize letters written by hand.

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“…Poly (vinyl alcohol) PVA, is a water-soluble polymer with unique characteristics, including high tensile strength and biocompatibility and also PVA-borax hydrogel has been widely recognized for its excellent properties in terms of mechanical strength, stretchability, and biocompatibility using borax as a crosslinking. However, it is well known that PVA borax hydrogels have poor elasticity and tensile strength and no current transfer (7,9). To solve this challenge, many studies on the use of other materials, such as graphene, cellulose nanofibers (CNFs), cellulose nanocrystals (CNCs), and MXene (Ti 3 C 2 ), have been included in PVA-based hydrogels (23).…”

A ZnO/PVA/CHI Composite Electrode for Rechargeable Zinc-air Battery

“…As illustrated inFig.1 (a), the FTIR spectra of ZnO/PVA/CHI composite were recorded from 4000 to 400 cm -1 .The absorption peak around 3415 cm -1 in the spectrum belongs to the stretching vibrations of surface O-H bonds from PVA and N-H bonds from CHI [21][22] .The bands located at 2926,1421, and 1116cm -1 are respectively put down to the aliphatic C-H stretching vibration, the CH-OH stretching vibration, and the -CH 2 stretching vibration in the PVA [22][23] .The stretching vibration absorption peak appeared at 1635 cm -1 in the spectra can be attributed to the O-H bond in the CHI. Among the peak assigned to ZnO, the peak located at 437 cm -1 is attributed to the O-Zn stretching vibrations on Zn atoms [24] .…”

A Transparent Poly(vinyl alcohol) Ion‐Conducting Organohydrogel for Skin‐Based Strain‐Sensing Applications

“…[6] Liu et al demonstrated that a similar PVA-glycerol-NaCl hydrogel maintained 86% transparency even with the addition of zirconium phosphate nanosheets and cellulose nanofibers (CNFs). [10] Another PVA-glycerol-sodium alginate (SA)-CaCl 2 system developed by X. Liu et al achieved 96% transparency. [17] Though incorporation of polyols is beneficial for transparency, their effects on the sensing performance of ion-conductive PVA systems have not been sufficiently studied, highlighting the need for further research in this area.…”

“…Flexible moieties or dynamic bonds are commonly employed for softness, while hierarchical morphologies, crosslinked double networks, or structural nanomaterials such as CNFs are often used to maintain mechanical strength. [10,11,14,16] X. Liu et al's PVA-glycerol-SA-CaCl 2 network consists of dynamic hydrogen and ion-ligand bonds capable of dissipating energy. [17] Y. Liu et al reported a soft-hard network gel that uses PVA and poly(vinyl pyrrolidone) as the soft, flexible portions while cellulose nanocrystal (CNC)-Fe 3+ complexes serve as the hard, tough crosslinkers.…”

“…Liu et al [10] PVA/CNF/ Zirconium phosphate nanosheets/ glycerol/NaCl 87% 2420 5 541 0.00765 2.46 350+…”