Cellulose Nanofibrils Enhanced, Strong, Stretchable, Freezing‐Tolerant Ionic Conductive Organohydrogel for Multi‐Functional Sensors

Cellulose based ZnO nanocomposite (RCZ) films were prepared from cellulose carbamate–NaOH/ZnO solutions through one-step coagulation in Na2SO4 aqueous solutions. The structure and properties of RCZ films were characterized using XRD, FTIR, XPS, SEM, TEM, TG, tensile testing, and antibacterial activity tests. The content of ZnO in RCZ films was obtained in the range of 2.7–15.1 wt %. ZnO nanoparticles with a hexagonal wurtzite structure agglomerated into large particles, which firmly embedded in the cellulose matrix. RCZ films displayed good mechanical properties and high thermal stability. Moreover, the films exhibited excellent UV-blocking properties and antibacterial activities against Staphylococcus aureus and Escherichia coli. A dramatic reduction in viable bacteria was observed within 3 h of exposure, while all of the bacteria were killed within 6 h. This work provided a novel and simple pathway for the preparation of regenerated cellulose films with ZnO nanoparticles for application as functional bi...

Construction of Cellulose Based ZnO Nanocomposite Films with Antibacterial Properties through One-Step Coagulation

High-strength petroleum-based materials like plastics have been widely used in various fields, but their nonbiodegradability has caused serious pollution problems. Cellulose, as the most abundant sustainable polymer, has a great chance to act as the ideal substitute for plastics due to its low cost, wide availability, biodegradability, etc. Herein, the recent achievements for developing cellulose "green" solvents and regenerated cellulose materials with high strength via the "bottom-up" route are presented. Cellulose can be regenerated to produce films/membranes, hydrogels/aerogels, filaments/fibers, microspheres/beads, bioplastics, etc., which show potential applications in textiles, biomedicine, energy storage, packaging, etc. Importantly, these cellulose-based materials can be biodegraded in soil and oceans, reducing environmental pollution. The cellulose solvents, dissolving mechanism, and strategies for constructing the regenerated cellulose functional materials with high strength and performances, together with the current achievements and urgent challenges are summarized, and some perspectives are also proposed. The near future will be an exciting era for high-strength biodegradable and renewable materials. The hope is that many environmentally friendly materials with good properties and low cost will be produced for commercial use, which will be beneficial for sustainable development in the world.

Recent Progress in High-Strength and Robust Regenerated Cellulose Materials

Breath analysis is an attractive strategy that holds tremendous potential to achieve non-implantable physical health management enabled by flexible humidity sensors for breathing behaviors (e.g., continuity, frequency) related to disease monitoring and chemiresistive gas sensors related early disease diagnosis. Compared to other techniques for breath component detection, non-invasive breathing diagnostics based on chemical sensors can offer several advantages like miniaturization, low power consumption, simple structure and cost-saving, which is helpful to enhance the portability of practical tests. Although extensive research has been carried out over the past two decades to improve sensing performances of breath gas sensors, many problems need to be further addressed when it comes to clinical disease diagnosis. Developing integrated gas sensor arrays have become one of the efficient solutions to improve detection accuracy. To get rid of external power supply, various novel sensors combining with self-powered technology are designed to exhibit a desirable development prospect in breath analysis. Thus, this review aims to summarize the latest research advances on wearable humidity-enabled breathing behaviors monitoring and typical biomarker gases-based disease screening, and also provides the prospects of future development from individual sensors to integrated devices and self-powered health monitoring systems.

Evolution of breath analysis based on humidity and gas sensors: Potential and challenges

Waste from non-degradable plastics is becoming an increasingly serious problem. Therefore, more and more research focuses on the development of materials with biodegradable properties. Bio-polymers are excellent raw materials for the production of such materials. Bio-based biopolymer films reinforced with nanostructures have become an interesting area of research. Nanocomposite films are a group of materials that mainly consist of bio-based natural (e.g., chitosan, starch) and synthetic (e.g., poly(lactic acid)) polymers and nanofillers (clay, organic, inorganic, or carbon nanostructures), with different properties. The interaction between environmentally friendly biopolymers and nanofillers leads to the improved functionality of nanocomposite materials. Depending on the properties of nanofillers, new or improved properties of nanocomposites can be obtained such as: barrier properties, improved mechanical strength, antimicrobial, and antioxidant properties or thermal stability. This review compiles information about biopolymers used as the matrix for the films with nanofillers as the active agents. Particular emphasis has been placed on the influence of nanofillers on functional properties of biopolymer films and their possible use within the food industry and food packaging systems. The possible applications of those nanocomposite films within other industries (medicine, drug and chemical industry, tissue engineering) is also briefly summarized.

The Effect of Nanofillers on the Functional Properties of Biopolymer-based Films: A Review.

A highly stretchable, transparent ionic conductive cellulose/PVA hydrogel (CPH) was fabricated by a facile and environment-friendly strategy with zero wastage CPH based sensors exhibited fast and stable sensitivity to temperature, compressive pressure and tensile strain A CPH based triboelectric nanogenerator for energy harvesting exhibited resistance to temperature change, stretching, long time storage or even a large number of operation cycles

Highly stretchable, transparent cellulose/PVA composite hydrogel for multiple sensing and triboelectric nanogenerators

Cellulose was dissolved in benzyltrimethyl ammonium hydroxide (BzMe3NOH) aqueous solution, and ionic conductive cellulose hydrogels (CCHs) with antifreezing property were directly fabricated by chemical cross-linking, without further treatment. The concentrated BzMe3NOH solution in the CCH matrix endowed the hydrogel with transparency, ionic conductivity, and freeze tolerance. CCH maintained transparency over 90% and stable mechanical properties in the temperatures from -27.8 to 62.1 °C. Furthermore, the CCH-based sensors exhibited stable sensitivity to tensile strain, compressive pressure, and temperature, in a wide temperature range including the subzero temperature, with a fast responding time and no obvious hysteresis. The present work is expected to provide a simple and sustainable pathway to prepare an antifreezing soft conductor with multifunctions based on cellulose, which enables a broad range of potential applications.

Transparent, Antifreezing, Ionic Conductive Cellulose Hydrogel with Stable Sensitivity at Subzero Temperature.

A transparent and flexible cellulose/KOH composite ionic film (CKF) is fabricated as a humidity sensor. CKF exhibits high optical transmittance (87.14% at 550 nm), which has rarely been reported among humidity sensors as a result of the small pore size of the cellulose matrix caused by water-evaporation-induced dense packing and uniform distribution of amorphous KOH via simply soaking–drying. CKF also possesses flexibility and robust mechanical property. The conductive CKF shows fast and reversible real-time response to relative humidity (RH) in the 11.3–97.3% RH range with conductance varying over 200 times, response/recovery times of 6.0/10.8 s, which are shorter than the majority of the reported values, as well as a hysteresis error of 0.57%, which is significantly less than that reported in the literature. Furthermore, CKF is insensitive to both the temperature (10–70 °C) and pressure (0–120 kPa), indicating high selectivity as humidity sensors. In both the non-contact fingertip moisture detection and...

Flexible and Transparent Cellulose-Based Ionic Film as a Humidity Sensor.

Because of the serious pollution caused by nondegradable plastic waste, environmentally benign materials from sustainable polymers have attracted tremendous research interest. Especially, functiona...

Cellulose/Chitosan Composite Multifilament Fibers with Two-Switch Shape Memory Performance

Cellulose carbamates (CCs) were successfully prepared from cellulose/urea (CU) mixtures based on an easy scale-up method and minimum urea. Urea content and the reaction conditions on the nitrogen content of the reacted CU (RCU) mixtures and CCs were systematically investigated. RCU mixtures and CCs were characterized with elemental analysis, Fourier transform infrared spectroscopy, X-ray diffraction, NMR spectrometry and solubility testing. The result indicated that almost all of urea was involved in the derivatization reaction and cellulose was converted into CC with absence of byproducts. The nitrogen content of CCs increased with an increase of the urea content and the reaction temperature, as well as the reaction time. CCs retained the cellulose I crystalline, and the degree of polymerization hardly changed with the reaction conditions. CCs prepared from CU mixtures with the urea content of 3.4–4.6 wt % displayed good solubility in NaOH/ZnO aqueous solutions. Especially, RCU mixtures without washing c...

Yang Wang

Papers

Highly stretchable, transparent cellulose/PVA composite hydrogel for multiple sensing and triboelectric nanogenerators

Transparent, Antifreezing, Ionic Conductive Cellulose Hydrogel with Stable Sensitivity at Subzero Temperature.

Flexible and Transparent Cellulose-Based Ionic Film as a Humidity Sensor.

Cellulose/Chitosan Composite Multifilament Fibers with Two-Switch Shape Memory Performance

Improved Synthesis of Cellulose Carbamates with Minimum Urea Based on an Easy Scale-up Method