Biopolymer nanofibrils exhibit exceptional mechanical properties with a unique combination of strength and toughness, while also presenting biological functions that interact with the surrounding environment. These features of biopolymer nanofibrils profit from their hierarchical structures that spun angstrom to hundreds of nanometer scales. To maintain these unique structural features and to directly utilize these natural supramolecular assemblies, a variety of new methods have been developed to produce biopolymer nanofibrils. In particular, cellulose nanofibrils (CNFs), chitin nanofibrils (ChNFs), silk nanofibrils (SNFs) and collagen nanofibrils (CoNFs), as the four most abundant biopolymer nanofibrils on earth, have been the focus of research in recent years due to their renewable features, wide availability, low-cost, biocompatibility, and biodegradability. A series of top-down and bottom-up strategies have been accessed to exfoliate and regenerate these nanofibrils for versatile advanced applications. In this review, we first summarize the structures of biopolymer nanofibrils in nature and outline their related computational models with the aim of disclosing fundamental structure-property relationships in biological materials. Then, we discuss the underlying methods used for the preparation of CNFs, ChNFs, SNF and CoNFs, and discuss emerging applications for these biopolymer nanofibrils.

Recent improvements in flexible electronics have increased the need to develop flexible and lightweight power sources. However, current flexible electrodes are limited by low capacitance, poor mechanical properties, and lack of cycling stability. In this article, we describe an ionic liquid-processed supramolecular assembly of cellulose and 3,4-ethylenedioxythiophene for the formation of a flexible and conductive cellulose/poly(3,4-ethylenedioxythiophene) PEDOT:poly(styrene sulfonate) (PSS) composite matrix. On this base, multiwalled carbon nanotubes (MWCNTs) were incorporated into the matrix to fabricate an MWCNT-reinforced cellulose/PEDOT:PSS film (MCPP), which exhibited favorable flexibility and conductivity. The MCPP-based electrode displayed comprehensively excellent electrochemical properties, such as a low resistance of 0.45 Ω, a high specific capacitance of 485 F g at 1 A g, and good cycling stability, with a capacity retention of 95% after 2000 cycles at 2 A g. An MCPP-based symmetric solid-state supercapacitor with Ni foam as the current collector and PVA/KOH gel as the electrolyte exhibited a specific capacitance of 380 F g at 0.25 A g and achieved a maximum energy density of 13.2 Wh kg (0.25 A g) with a power density of 0.126 kW kg or an energy density of 4.86 Wh kg at 10 A g, corresponding to a high power density of 4.99 kW kg. Another kind of MCPP-based solid-state supercapacitor without the Ni foam showed excellent flexibility and a high volumetric capacitance of 50.4 F cm at 0.05 A cm. Both the electrodes and the supercapacitors were environmentally stable and could be operated under remarkable deformation or high temperature without damage to their structural integrity or a significant decrease in capacitive performance. Overall, this work provides a strategy for the fabrication of flexible and conductive energy-storage films with ionic liquid-processed cellulose as a medium.

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Dehumidification is significant for environmental sustainability and human health. Traditional dehumidification methods involve significant energy consumption and have negative impact on the environment. The core challenge is to expose hygroscopic surfaces to the air, and appropriately store the captured water and avoid surface inactivation. Here, a nanostructured moisture‐absorbing gel (N‐MAG) for passive dehumidification, which consists of a hydrophilic nanocellulose network functionalized by hygroscopic lithium chloride, is reported. The interconnected nanocellulose can transfer the captured water to the internal space of the bulky N‐MAG, eliminating water accumulation near the surfaces and hence enabling high‐rate moisture absorption. The N‐MAG can reduce the relative humidity from 96.7% to 28.7% in 6 h, even if the space is over 2 × 104 times of its own volume. The condensed water can be completely confined in the N‐MAG, overcoming the problem of environmental pollution. This research brings a new perspective for sustainable humidity management without energy consumption and with positive environmental footprint.

Bioinspired actuators with stimuli-responsive and deformable properties are being pursued in fields such as artificial tissues, medical devices and diagnostics, and intelligent biosensors. These applications require that actuator systems have biocompatibility, controlled deformability, biodegradability, mechanical durability, and stable reversibility. Herein, we report a bionic actuator system consisting of stimuli-responsive genetically engineered silk–elastin-like protein (SELP) hydrogels and wood-derived cellulose nanofibers (CNFs), which respond to temperature and ionic strength underwater by ecofriendly methods. Programmed site-selective actuation can be predicted and folded into three-dimensional (3D) origami-like shapes. The reversible deformation performance of the SELP/CNF actuators was quantified, and complex spatial transformations of multilayer actuators were demonstrated, including a biomimetic flower design with selective petal movements. Such actuators consisting entirely of biocompatible and biodegradable materials will offer an option toward constructing stimuli-responsive systems for in vivo biomedicine soft robotics and bionic research.

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contaminants owing to their chemical affi nity with these contaminants, large surface area, porous structure, and other remarkable physical properties. [ 1 ] Due to their superior hydrophobic and oleophilic characteristics, carbon aerogels can effectively absorb a variety of oils and organic solvents without water penetration. However, most of these carbon aerogels are synthesized from carbonaceous precursors, such as carbon-containing polymers, [ 2 ] carbon-containing fi bers, [ 3 ] carbon nanofi bers, [ 4 ] carbon nanotubes, [ 5 ] and graphene. [ 6 ] Problems of these expensive precursors and complex and energyconsuming process in the production of carbon aerogels restrict the practical use of carbon aerogels on a large-scale. In this regard, the utilization of renewable biomass as precursors, together with simple and low-energy treatment to fabricate sustainable carbon aerogels is strongly desired. [ 7 ] In this study, we employ nanofi brillated cellulose (NFC) as a sustainable and scalable precursor for producing carbon aerogels. The reason to choose NFC as the precursor is based on its unique structures and properties. First, cellulose is a good carbon source. Cellulose-containing woods have been used as the precursor of activated coals for many years. Second, comparing with traditional cellulosic pulps in the micrometer-scale, NFC produced by disintegration of pulps has much smaller diameters in nanometer-scale (typically <10 nm) as well as advantageous mechanical strength due to the extended chain crystals of cellulose and large specifi c surface areas. [ 8 ] Further, NFC is able to form porous aerogels with a microscopic network and a large specifi c surface area. Although the NFC aerogels are expected to use for absorbing or separating of oils and organic solvents from water, the separation effi ciency is low because of the strong hydrophilicity of cellulose. [ 9 ] To improve the absorbent performance, the surface of NFC aerogels was chemically modifi ed to be hydrophobic and oleophilic with TiO 2 coating [ 10 ] or vapor phase silanization. [ 11 ] However, these modifi ed NFC aerogels still showed a weak absorbent performance (<45 times of their own weight). Jiang and Hsieh synthesized a functionalized NFC aerogel by chemical vapor deposition of (triethoxyl(octyl) silane) which was able to absorb 139-356 times organic solvents or oils by weight. [ 12 ] Unfortunately, their NFC aerogel also absorbed water when it was immersed into water, Sustainable carbon aerogels with low density (≈7.8 mg cm −3 ), high porosity, high resiliency, excellent hydrophobicity, and oleophilic characteristics are synthesized by employing nanofi brillated cellulose as the precursor. The as-prepared carbon aerogels show a remarkable capacity for the absorption of a variety of oils and organic solvents with weight gains ranging from 7422 to 22356. Under extreme conditions (e.g., at severe temperatures and in corrosive liquids), these carbon aerogels still demonstrate a superior absorption performance. Furthermore, a device ...

Cellulose nanocrystal has been widely used as a reinforcement filler in waterborne coatings, but the application of cellulose nanofiber (CNF) as a filler is difficult because of inhomogeneous dispersion. Herein, a facile and effective strategy to improve the dispersion of CNFs in the polymer matrix by mixing with γ-aminopropyltriethoxysilane (APS) is presented. The APS dosages 0.08−0.48 wt % to 0.3 wt % CNFs were investigated, and the dosage 0.16% was found to achieve a superior stability of CNFs in the aqueous solution. The APS(0.16%)-modified CNFs were then incorporated and demonstrated distributing uniformly in the waterborne acrylic coating. The as-prepared coatings retain high light transmittance around 90%, and display improved mechanical properties. The composite coatings show a maximum 500% improvement in Young's modulus, two-level improvement in hardness, and 35% reduction in abrasion loss as compared with those of neat coating. These results reveal that APS modification induces the homogeneous dispersion of CNFs in aqueous solution, and turns the CNF into an ideal reinforced filler for waterborne coatings.