New hybrid colloidal gels are reported formed by amyloid fibrils and CaCO3 nanoparticles (CaNPs), with Ca2+ as charge screening ions and CaNPs as physical crosslinking agents to establish and ...stabilize the network. The gel is characterized by rheological measurements and diffusing wave spectroscopy, complemented by microscopic observations using transmission and scanning electron microscopy. The hybrid colloidal gels show a two orders of magnitude improved gel strength at significantly shorter gelation times compared to previous calcium ion‐induced amyloid fibril gels. Supercritical CO2‐dried colloidal aerogels allow demonstrating that amyloid fibrils, combined with smaller (higher specific surface area) CaNPs, constitute a denser fibrils network, resulting in stronger gels. By varying the amyloid fibril concentration and the CaNPs size and concentration, the complete phase diagram is mapped out. This enables identifying the sol–gel phase transition and a window for gel formation, which widens with increasing CaNPs size. Finally pH responsiveness and self‐healing properties of this hybrid colloidal gel are also demonstrated, making these systems a suitable candidate for biological applications.
This study describes a new strategy to form hydrogels and aerogels based on beta‐lactoglobulin fibrils and calcium carbonate nanoparticles (CaNPs). By dispersing and dissolving CaNPs in beta‐lactoglobulin fibril solutions, calcium ions and CaNPs act as charge screeners and crosslinkers, respectively, leading to stable gel networks. The resulting gels show high mechanical strengths and pH‐sensitive self‐healing properties, opening novel opportunities for biological and pharmaceutical applications.
Nanocellulose fibrils are ubiquitous in nature and nanotechnologies but their mesoscopic structural assembly is not yet fully understood. Here we study the structural features of rod-like cellulose ...nanoparticles on a single particle level, by applying statistical polymer physics concepts on electron and atomic force microscopy images, and we assess their physical properties via quantitative nanomechanical mapping. We show evidence of right-handed chirality, observed on both bundles and on single fibrils. Statistical analysis of contours from microscopy images shows a non-Gaussian kink angle distribution. This is inconsistent with a structure consisting of alternating amorphous and crystalline domains along the contour and supports process-induced kink formation. The intrinsic mechanical properties of nanocellulose are extracted from nanoindentation and persistence length method for transversal and longitudinal directions, respectively. The structural analysis is pushed to the level of single cellulose polymer chains, and their smallest associated unit with a proposed 2 × 2 chain-packing arrangement.
In modern society, there is a constant need for developing reliable, sustainable, and cost-effective antibacterial materials. Here, we investigate the preparation of cellulose nanocrystal ...(CNC)–lysozyme composite films via the well-established method of evaporation-induced self-assembly. We consider the effects of lysozyme concentration and aggregation state (native lysozyme, lysozyme amyloid fibers, and sonicated lysozyme amyloid fibers) on suspension aggregation and film-forming ability. Although at higher lysozyme loading levels (ca. 10 wt %), composite films lost their characteristic chiral nematic structuring, these films demonstrated improved mechanical properties and antibacterial activity with respect to CNC-only films, regardless of lysozyme aggregation state. We anticipate that the results presented herein could also contribute to the preparation of other CNC–protein-based materials, including films, hydrogels, and aerogels, with improved mechanical performance and antibacterial activity.
Structural organization is ubiquitous throughout nature and contributes to the outstanding mechanical/adhesive performance of organisms including geckoes, barnacles, and crustaceans. Typically, these ...types of structures are composed of polysaccharide and protein-based building blocks, and therefore, there is significant research interest in using similar building blocks in the fabrication of high-performance synthetic materials. Via evaporation-induced self-assembly, the organization of cellulose nanocrystals (CNCs) into a chiral nematic regime results in the formation of structured CNC films with prominent mechanical, optical, and photonic properties. However, there remains an important knowledge gap in relating equilibrium suspension behavior to dry film structuring and other functional properties of CNC-based composite materials. Herein, we systematically investigate the phase behavior of composite suspensions of rigid CNCs and flexible bovine serum albumin (BSA) amyloids in relation to their self-assembly into ordered films and structural adhesives. Increasing the concentration of BSA amyloids in the CNC suspensions results in a clear decrease in the anisotropic fraction volume percent via the preferential accumulation of BSA amyloids in the isotropic regime (as a result of depletion interactions). This translates to a blue shift or compression of the chiral nematic pitch in dried films. Finally, we also demonstrate the synergistic adhesive potential of CNC–BSA amyloid composites, with ultimate lap shear strengths in excess of 500 N/mg. We anticipate that understanding the systematic relationships between material interactions and self-assembly in suspension such as those investigated here will pave the way for a new generation of structured composite materials with a variety of enhanced functionalities.
•Shape morphing and self-actuating nanocellulose hydrogels prepared by 3D printing.•3D printing enables alignment of cellulose reinforcements.•AMPs modification gives anti-bacterial properties to the ...cellulose-based structures.•Hydrogels functionalized with AMPs can potentially be used in biomedical fields.
We report on a procedure for the preparation, printing and curing of antibacterial poly(N-isopropylacrylamide) nanocellulose-reinforced hydrogels. These composites present a highly anisotropic microstructure which allows to control and modulate the resulting mechanical properties. The incorporation of such nanoparticles enables us to modify both the strength and the humidity-dependent swelling direction of printed parts, offering a fourth-dimensional property to the resulting composite. Antibacterial properties of the hydrogels were obtained by incorporating the functionalized peptide ε-polylysine, modified with the addition of a methacrylate group to ensure UV-immobilization. We highlight the relevance of well-adapted viscoelastic properties of our material for 3D printing by direct ink writing of self-supporting complex structures reaching inclination angles of 45°. The addition of cellulose nanoparticles, the overall ink composition and the printing parameters strongly determine the resulting degree of orientation. The achieved control over the anisotropic swelling properties paves the way to complex three-dimensional structures with programmable actuation.
It is demonstrated that it is possible to coat the individual fibers of wood-based nanocellulose with polypyrrole using in situ chemical polymerization to obtain an electrically conducting continuous ...high-surface-area composite. The experimental results indicate that the high surface area of the water dispersed material, to a large extent, is maintained upon normal drying without the use of any solvent exchange. Thus, the employed chemical polymerization of polypyrrole on the microfibrillated cellulose (MFC) nanofibers in the hydrogel gives rise to a composite, the structure of whichunlike that of uncoated MFC paperdoes not collapse upon drying. The dry composite has a surface area of ∼90 m2/g and a conductivity of ∼1.5 S/cm, is electrochemically active, and exhibits an ion-exchange capacity for chloride ions of 289 C/g corresponding to a specific capacity of 80 mAh/g. The straightforwardness of the fabrication of the present nanocellulose composites should significantly facilitate industrial manufacturing of highly porous, electroactive conductive paper materials for applications including ion-exchange and paper-based energy storage devices.
In order to limit the excessive use of nonrenewable plastics as materials for food packaging, research into the development of more environmentally friendly packaging materials and practices has ...grown rapidly over the past few decades. Although cellulose nanofibers (CNF) have emerged as a promising material for such purposes, typically commercial producers utilize already valorized lignocellulosic sources such as wood pulp for CNF production. This can have significant cost implications, and therefore the use of alternative lignocellulosic sources, such as wastes from agricultural processing, is of high interest. Herein, we investigate the use of carrot pomace from both fresh and stale carrots, sourced as agricultural waste (unsellable for retail) from a local Swiss vegetable producer to produce CNF. The use of a one-pot bleaching pretreatment and the energy required for homogenization of the carrot pomace along with the resulting CNF fiber morphology and quality (surface area, degree of polymerization, carbohydrate content) are analyzed. In addition, model films are prepared via vacuum filtration and hot-pressing, whereby film quality, as related to morphological, optical, mechanical, and barrier properties, is assessed. Finally, carrot CNF suspensions are sprayed onto the surface of bananas, demonstrating a substantial delay in enzymatic browning for up to 1 week. The results presented herein represent a significant advancement in the development of sustainable materials for food packaging.
Abstract
We developed a disposable paper battery aiming to reduce the environmental impact of single-use electronics for applications such as point of care diagnosis, smart packaging and ...environmental sensing. The battery uses Zinc as a biodegradable metal anode, graphite as a nontoxic cathode material and paper as a biodegradable substrate. To facilitate additive manufacturing, we developed electrodes and current collector inks that can be stencil printed on paper to create water-activated batteries of arbitrary shape and size. The battery remains inactive until water is provided and absorbed by the paper substrate, taking advantage of its natural wicking behavior. Once activated, a single cell provides an open circuit potential of 1.2 V and a peak power density of 150 µW/cm
2
at 0.5 mA. As a proof of concept, we fabricated a two cell battery and used it to power an alarm clock and its liquid crystal display.
Designing lightweight nanostructured aerogels for high‐performance electromagnetic interference (EMI) shielding is crucial yet challenging. Ultrathin cellulose nanofibrils (CNFs) are employed for ...assisting in building ultralow‐density, robust, and highly flexible transition metal carbides and nitrides (MXenes) aerogels with oriented biomimetic cell walls. A significant influence of the angles between oriented cell walls and the incident EM wave electric field direction on the EMI shielding performance is revealed, providing an intriguing microstructure design strategy. MXene “bricks” bonded by CNF “mortars” of the nacre‐like cell walls induce high mechanical strength, electrical conductivity, and interfacial polarization, yielding the resultant MXene/CNF aerogels an ultrahigh EMI shielding performance. The EMI shielding effectiveness (SE) of the aerogels reaches 74.6 or 35.5 dB at a density of merely 8.0 or 1.5 mg cm–3, respectively. The normalized surface specific SE is up to 189 400 dB cm2 g–1, significantly exceeding that of other EMI shielding materials reported so far.
Oriented biomimetic hybrid cell walls of nanocellulose‐MXene aerogels for tunable electromagnetic interference shielding and mechanism are represented by a yin‐yang symbol. Herein, the blue and red regions in the symbol correspond to angles with a smaller and larger transmission of the incident EM waves, respectively.
Brewery spent grain (BSG), the main waste of the brewery industry, is often disposed of or sold as an animal feed at low prices, neglecting the potential for further valorization. In this work, BSG ...was used for the first time to produce cellulose nanofiber aerogels for green thermal insulating applications. Cellulose nanofibers (CNFs) were extracted from BSG through microfluidization with and without TEMPO-oxidation pretreatment to obtain bio-based building blocks for aerogels. The TEMPO-treated CNFs exhibited a finer diameter (5.4 nm) with a more homogeneous size distribution (2–10 nm) than that of nonoxidized samples. All of the produced aerogels demonstrated low densities (0.009–0.031 g/cm3), low thermal conductivities (32.3–37.7 mW/mK), and a compressive Young’s modulus in the range of 4–311 kPa. Unidirectional freezing and TEMPO-oxidation showed a distinct improvement in the thermal conductivity and mechanical properties of the aerogels compared to the random frozen samples. Specifically, the unidirectional frozen aerogel with the highest investigated CNF concentration of 3 wt % exhibited the lowest thermal conductivity (32.4 mW/mK), highest Young’s modulus (311 kPa), and good thermal stability. These results show that the BSG-derived nanocellulose is a valuable resource for producing eco-friendly, biodegradable, and thermally insulating aerogels.
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