Biofabrication with microbial cellulose: from bioadaptive designs to living materials.

Nanocellulose is not only a renewable material but also brings functions that are opening new technological opportunities. Here we discuss a special subset of this material, in its fibrillated form, which is produced by aerobic microorganisms, namely, bacterial nanocellulose (BNC). BNC offers distinct advantages over plant-derived counterparts, including high purity and high degree of polymerization as well as crystallinity, strength, and water-holding capacity, among others. More remarkably, beyond classical fermentative protocols, it is possible to grow BNC on non-planar interfaces, opening new possibilities in the assembly of advanced bottom-up structures. In this review, we discuss the recent advances in the area of BNC-based biofabrication of three-dimensional (3D) designs by following solid- and soft-material templating. These methods are shown as suitable platforms to achieve bioadaptive constructs comprising highly interlocked biofilms that can be tailored with precise control over nanoscale morphological features. BNC-based biofabrication opens applications that are not possible by using traditional manufacturing routes, including direct ink writing of hydrogels. This review emphasizes the critical contributions of microbiology, colloid and surface science, as well as additive manufacturing in achieving bioadaptive designs from living matter. The future impact of BNC biofabrication is expected to take advantage of material and energy integration, residue utilization, circularity and social latitudes. Leveraging existing infrastructure, the scaleup of biofabrication routes will contribute to a new generation of advanced materials rooted in exciting synergies that combine biology, chemistry, engineering and material sciences.

Nanochitin: Chemistry, Structure, Assembly, and Applications.

Chitin, a fascinating biopolymer found in living organisms, fulfills current demands of availability, sustainability, biocompatibility, biodegradability, functionality, and renewability. A feature of chitin is its ability to structure into hierarchical assemblies, spanning the nano- and macroscales, imparting toughness and resistance (chemical, biological, among others) to multicomponent materials as well as adding adaptability, tunability, and versatility. Retaining the inherent structural characteristics of chitin and its colloidal features in dispersed media has been central to its use, considering it as a building block for the construction of emerging materials. Top-down chitin designs have been reported and differentiate from the traditional molecular-level, bottom-up synthesis and assembly for material development. Such topics are the focus of this Review, which also covers the origins and biological characteristics of chitin and their influence on the morphological and physical-chemical properties. We discuss recent achievements in the isolation, deconstruction, and fractionation of chitin nanostructures of varying axial aspects (nanofibrils and nanorods) along with methods for their modification and assembly into functional materials. We highlight the role of nanochitin in its native architecture and as a component of materials subjected to multiscale interactions, leading to highly dynamic and functional structures. We introduce the most recent advances in the applications of nanochitin-derived materials and industrialization efforts, following green manufacturing principles. Finally, we offer a critical perspective about the adoption of nanochitin in the context of advanced, sustainable materials.

Three-Dimensional Printed Cell Culture Model Based on Spherical Colloidal Lignin Particles and Cellulose Nanofibril-Alginate Hydrogel.

Three-dimensional (3D) printing has been an emerging technique to fabricate precise scaffolds for biomedical applications. Cellulose nanofibril (CNF) hydrogels have attracted considerable attention as a material for 3D printing because of their shear-thinning properties. Combining cellulose nanofibril hydrogels with alginate is an effective method to enable cross-linking of the printed scaffolds in the presence of Ca2+ ions. In this work, spherical colloidal lignin particles (CLPs, also known as spherical lignin nanoparticles) were used to prepare CNF-alginate-CLP nanocomposite scaffolds. High-resolution images obtained by atomic force microscopy (AFM) showed that CLPs were homogeneously mixed with the CNF hydrogel. CLPs brought antioxidant properties to the CNF-alginate-CLP scaffolds in a concentration-dependent manner and increased the viscosity of the hydrogels at a low shear rate, which correspondingly provide better shape fidelity and printing resolution to the scaffolds. Interestingly, the CLPs did not affect the viscosity at high shear rates, showing that the shear thinning behavior typical for CNF hydrogels was retained, enabling easy printing. The CNF-alginate-CLP scaffolds demonstrated shape stability after printing, cross-linking, and storage in Dulbecco's phosphate buffer solution (DPBS +) containing Ca2+ and Mg2+ ions, up to 7 days. The 3D-printed scaffolds showed relative rehydration ratio values above 80% after freeze-drying, demonstrating a high water-retaining capability. Cell viability tests using hepatocellular carcinoma cell line HepG2 showed no negative effect of CLPs on cell proliferation. Fluorescence microscopy indicated that HepG2 cells grew not only on the surfaces but also inside the porous scaffolds. Overall, our results demonstrate that nanocomposite CNF-alginate-CLP scaffolds have high potential in soft-tissue engineering and regenerative-medicine applications.

Adsorption and Assembly of Cellulosic and Lignin Colloids at Oil/Water Interfaces.

The surface chemistry and adsorption behavior of submicrometer cellulosic and lignin particles have drawn wide-ranging interest in the scientific community. Here, we introduce their assembly at fluid/fluid interfaces in Pickering systems and discuss their role in reducing the oil/water interfacial tension, limiting flocculation and coalescence, and endowing given functional properties. We discuss the stabilization of multiphase systems by cellulosic and lignin colloids and the opportunities for their adoption. They can be used alone, as dual components, or in combination with amphiphilic molecules for the design of multiphase systems relevant to household products, paints, coatings, pharmaceutical, foodstuff, and cosmetic formulations. This invited feature article summarizes some of our work and that of colleagues to introduce the readers to this fascinating and topical area.

Low Solids Emulsion Gels Based on Nanocellulose for 3D-Printing.

Multiphase (emulsion) gels with internal phase fractions between 0.1 and 0.5 were formulated at low loadings of cellulose nanofibrils (CNF), alginate, and polylactide (PLA). Their properties (rheology and morphology) fitted those of inks used for direct ink writing (DIW). The effect of formulation and composition variables were elucidated after printing cubic scaffolds and other solid designs. The distinctive microstructures that were developed allowed high printing fidelity and displayed limited shrinkage after room temperature and freeze-drying (0 and 5% shrinkage in the out-of-plane and in-plane directions upon freeze-drying, respectively). The CNF added in the continuous phase was shown to be critical to achieve rheology control as an effective interfacial stabilizer and to ensure the printability of the ink toward high structural reliability. We found that the extent of shape retention of the dried scaffolds resulted from the tightly locked internal structure. The PLA that was initially added in the nonpolar or organic phase (0 to 12%) was randomly embedded in the entire scaffold, providing a strong resistance to shrinkage during the slow water evaporation at ambient temperature. No surface collapse or lateral deformation of the dried scaffolds occurred, indicating that the incorporation of PLA limited drying-induced shape failure. It also reduced compression strain by providing better CNF skeletal support, improving the mechanical strength. Upon rewetting, the combination of the hydrophilicity imparted by CNF and alginate together with the highly porous structure of the 3D material and the internal microchannels contributed to high water absorption via capillary and other phenomena (swelling % between ∼400 and 900%). However, no shape changes occurred compared to the initial 3D-printed shape. The swelling of the scaffolds correlated inversely with the PLA content in the precursor emulsion gel, providing a means to regulate the interaction with water given its low surface energy. Overall, the results demonstrate that by compatibilization of the CNF-based hydrophilic and the PLA-based hydrophobic components, it is possible to achieve shape control and retention upon 3D printing, opening the possibility of adopting low-solids inks for DIW into dry objects. The dryable CNF-based 3D structural materials absorb water while being able to support load (high elastic modulus) and maintain the shape upon hydration.

Acetylated Nanocellulose for Single-Component Bioinks and Cell Proliferation on 3D-Printed Scaffolds.

Nanocellulose has been demonstrated as a suitable material for cell culturing, given its similarity to extracellular matrices. Taking advantage of the shear thinning behavior, nanocellulose suits three-dimensional (3D) printing into scaffolds that support cell attachment and proliferation. Here, we propose aqueous suspensions of acetylated nanocellulose of a low degree of substitution for direct ink writing (DIW). This benefits from the heterogeneous acetylation of precursor cellulosic fibers, which eases their deconstruction and confers the characteristics required for extrusion in DIW. Accordingly, the morphology of related 3D-printed architectures and their performance during drying and rewetting as well as interactions with living cells are compared with those produced from typical unmodified and TEMPO-oxidized nanocelluloses. We find that a significantly lower concentration of acetylated nanofibrils is needed to obtain bioinks of similar performance, affording more porous structures. Together with their high surface charge and axial aspect, acetylated nanocellulose produces dimensionally stable monolithic scaffolds that support drying and rewetting, required for packaging and sterilization. Considering their potential uses in cardiac devices, we discuss the interactions of the scaffolds with cardiac myoblast cells. Attachment, proliferation, and viability for 21 days are demonstrated. Overall, the performance of acetylated nanocellulose bioinks opens the possibility for reliable and scale-up fabrication of scaffolds appropriate for studies on cellular processes and for tissue engineering.

Formulation and Stabilization of Concentrated Edible Oil-in-Water Emulsions Based on Electrostatic Complexes of a Food-Grade Cationic Surfactant (Ethyl Lauroyl Arginate) and Cellulose Nanocrystals.

We report on high-internal-phase, oil-in-water Pickering emulsions that are stable against coalescence during storage. Viscous, edible oil (sunflower) was emulsified by combining naturally derived cellulose nanocrystals (CNCs) and a food-grade, biobased cationic surfactant obtained from lauric acid and L-arginine (ethyl lauroyl arginate, LAE). The interactions between CNC and LAE were elucidated by isothermal titration calorimetry (ITC) and supplementary techniques. LAE adsorption on CNC surfaces and its effect on nanoparticle electrostatic stabilization, aggregation state, and emulsifying ability was studied and related to the properties of resultant oil-in-water emulsions. Pickering systems with tunable droplet diameter and stability against oil coalescence during long-term storage were controllably achieved depending on LAE loading. The underlying stabilization mechanism was found to depend on the type of complex formed, the LAE structures adsorbed on the cellulose nanoparticles (as unimer or as adsorbed admicelles), the presence of free LAE in the aqueous phase, and the equivalent alkane number of the oil phase (sunflower and dodecane oils were compared). The results extend the potential of CNC in the formulation of high-quality and edible Pickering emulsions. The functional properties imparted by LAE, a highly effective molecule against food pathogens and spoilage organisms, open new opportunities in food, cosmetics, and pharmaceutical applications, where the presence of CNC plays a critical role in achieving synergistic effects with LAE.

Electrospun Poly(lactic acid)-Based Fibrous Nanocomposite Reinforced by Cellulose Nanocrystals: Impact of Fiber Uniaxial Alignment on Microstructure and Mechanical Properties.

Uniform poly(lactic acid)/cellulose nanocrystal (PLA/CNC) fibrous mats composed of either random or aligned fibers reinforced with up to 20 wt % CNCs were successfully produced by two different electrospinning processes. Various concentrations of CNCs could be stably dispersed in PLA solution prior to fiber manufacture. The microstructure of produced fibrous mats, regardless of random or aligned orientation, was transformed from smooth to nanoporous surface by changing CNC loading levels. Aligning process through secondary stretching during high-speed collection can also affect the porous structure of fibers. With the same CNC loading, fibrous mats produced with aligned fibers had higher degree of crystallinity than that of fibers with random structure. The thermal properties and mechanical performances of PLA/CNC fibrous mats can be enhanced, showing better enhancement effect of aligned fibrous structure. This results from a synergistic effect of the increased crystallinity of fibers, the efficient stress transfer from PLA to CNCs, and the ordered arrangement of electrospun fibers in the mats. This research paves a way for developing an electrospinning system that can manufacture high-performance CNC-enhanced PLA fibrous nanocomposites.

Formulation and Composition Effects in Phase Transitions of Emulsions Costabilized by Cellulose Nanofibrils and an Ionic Surfactant.

Cellulose nanofibrils (CNF) offer great prospects as a natural stabilizer of colloidal dispersions and complex fluids for application in food, pharma, and cosmetics. In this study, an ionic surfactant (sodium dodecyl sulfate, SDS) was used as emulsifier of oil-in-water and water-in-oil emulsions that were further costabilized by addition of CNF. The adsorption properties of SDS in both, CNF dispersions and emulsions, as well as the influence of composition (CNF and SDS concentration) and formulation (ionic strength, oil, and CNF types) on the phase behavior were elucidated and described in the framework of Windsor systems. At low salinity, the phase transition of emulsions containing CNF and SDS at low concentrations was controlled by molecular transfer in the oil-in-water system. Irregular droplets and "bi-continuous" morphologies were observed at medium and high salinity for systems containing high CNF and SDS concentrations. Water-in-oil emulsions were only possible at high salinity and SDS concentrations in the presence of small amounts of CNF. The results revealed some subtle differences in CNF interfacial activity, depending on the method used for their isolation via fiber deconstruction, either from microfluidization or aqueous counter collision. Overall, we propose that the control of emulsion morphology and stability by addition of CNF opens the possibility of developing environmentally friendly complex systems that display high stability and respond to ionic strength following the expectations of classical emulsion systems.

Assembly of porous filaments by interfacial complexation of nanochitin-based Pickering emulsion and seaweed alginate.

Interfacial polyelectrolyte complexation spinning is an all-water, easy-to-operate method for production of composite filaments. Herein, this concept is extended to interfacial polyelectrolyte-emulsion complexation (IPEC) that better encodes structural and functional attributes of biomass substances into the filaments. This allows for formation of composite filaments by drawing contacting oppositely-charged chitin nanofiber-stabilized Pickering emulsion and seaweed alginate solution. The parameters affecting spinnability of the system including water-to-oil ratio, alginate concentration, and pH are comprehensively elucidated to support the design and application of IPEC. The composite filaments exhibit varied diameters and diverse porous structures that are adjustable by properties of Pickering droplets. The droplet diameter of precursor emulsion and pore size in the filaments are well correlated, revealing controllability of the IPEC spinning. The filaments are mechanically robust in dry condition and show stable performance even in wet condition. The release rate of filaments that is pre-loaded with hydrophilic drug is regulated by the internal pore size, showing capability on sustained release. This study offers a new perspective toward dry spinning via interfacial complexation of complicated nanochitin-based structural building blocks, aiming at developing high-performance fiber materials for advanced applications.

Processable Pickering emulsion for composite cryogel with cellulose nanofibrils and nanochitin.

Cryogels that are constructed with cellulose nanofibrils (CNF) are important as green materials for a wide range of applications. However, their utilization is limited by inherent hydrophilicity and insufficient mechanical properties. Herein, a processable CNF/nanochitin (NCh)-stabilized Pickering emulsion that contains polylactide (PLA) in the oil phase is developed to directly produce ternary composite cryogels via freeze-drying. The complexation of CNF with NCh promotes CNF adsorption at the surface of PLA droplets, resulting in formation of uniform Pickering PLA droplets. The CNF/NCh complex-stabilized PLA droplets are easy to be translated to the internal structure of the cryogels, exhibiting lightweight nature and possessing highly porous structure. The interconnected network and lamellar structure formed by the CNF/NCh complexes, associating with inclusion of PLA particles, improve the cryogel structure integrity upon post-processing and endow hydrophilic cryogel with water resistance. This study offers a straightforward and eco-friendly Pickering emulsion template on fabrication of the CNF-based composite cryogel with controllable microstructure and mechanical performance, broadening construction of nanocellulose-based composites.

Direct-ink-writable nanocellulose ternary hydrogels via one-pot gelation with alginate and calcium montmorillonite.

Nanocellulose hydrogels are promising to replace synthetic ones for direct ink writing (DIW)-based 3D printing biobased applications. However, less gelation strength and low solid content of the hydrogels limit the printability and subsequent fidelity of the dried object. Herein, a biobased, ternary DIW hydrogel ink is developed by one-pot gelation of cellulose nanofibrils (CNF), sodium alginate (SA), and Ca-montmorillonite (Ca-MMT) via in situ ionic crosslinking. The addition of Ca-MMT into CNF/SA formulation simultaneously increases the solid content and gelation strength of the hydrogel. The resultant hydrogels exhibit shape recovery after compression. The optimal CNF concentration in the hydrogel is 1.2 wt%, enabling the highest compressive mechanical performance of the scaffolds. A series of complex, customized shapes with different curvatures and three-dimensional structures (e.g., high-curvature letters, pyramids, human ears, etc.) can be printed with high fidelity before and after drying. This study opens an avenue on preparing nanocellulose-based DIW hydrogel inks using one-pot gelation of the components, which offers a solution to combine DIW-based 3D printing with biobased hydrogel inks, towards diverse biobased applications.

Layer-by-Layer Deposition of Low-Solid Nanochitin Emulgels Creates Porous Structures for High Cell Attachment and Proliferation.

Direct ink writing (DIW) is a customizable platform to engineer complex constructs from biobased colloids. However, the latter usually display strong interactions with water and lack interparticle connectivity, limiting one-step processing into hierarchically porous structures. We overcome such challenges by using low-solid emulgel inks stabilized by chitin nanofibrils (nanochitin, NCh). By using complementary characterization platforms, we reveal NCh structuring into spatially controlled three-dimensional (3D) materials that generate multiscale porosities defined by emulsion droplet size, ice templating, and DIW infill density. The extrusion variables, key in the development of surface and mechanical features of printed architectures, are comprehensively analyzed by using molecular dynamics and other simulation approaches. The obtained scaffolds are shown for their hierarchical porous structures, high areal density, and surface stiffness, which lead to excellent modulation of cell adhesion, proliferation, and differentiation, as tested with mouse dermal fibroblast expressing green fluorescent proteins.

Heteroaggregation effects on Pickering stabilization using oppositely charged cellulose nanocrystal and nanochitin.

Pickering emulsions are stabilized using complexes of cellulose nanocrystals (CNC) and nanochitin (NCh). The colloidal behavior and heteroaggregation in aqueous media are studied in relation to complex formation and net charge. The complexes are remarkably effective in stabilizing oil-in-water Pickering emulsions under conditions of slightly net positive or negative charges, as determined by the CNC/NCh mass ratio. Close to charge neutrality (CNC/NCh ~5), large heteroaggregates form, resulting in unstable emulsions. By contrast, under net cationic conditions, interfacial arrest of the complexes leads to non-deformable emulsion droplets with high stability (no creaming for 9 months). At given CNC/NCh concentrations, emulsions with up to 50% oil fraction are produced. This study shows how to control emulsion properties beyond consideration of the typical formulation variables, for instance, through adjusting CNC/NCh ratio or charge stoichiometry. We highlight the possibilities that are available for emulsion stabilization by using a combination of polysaccharide nanoparticles.

Recent Innovations in Emulsion Science and Technology for Food Applications.

Emulsion technology has been used for decades in the food industry to create a diverse range of products, including homogenized milk, creams, dips, dressings, sauces, desserts, and toppings. Recently, however, there have been important advances in emulsion science that are leading to new approaches to improving food quality and functionality. This article provides an overview of a number of these advanced emulsion technologies, including Pickering emulsions, high internal phase emulsions (HIPEs), nanoemulsions, and multiple emulsions. Pickering emulsions are stabilized by particle-based emulsifiers, which may be synthetic or natural, rather than conventional molecular emulsifiers. HIPEs are emulsions where the concentration of the disperse phase exceeds the close packing limit (usually >74%), which leads to novel textural properties and high resistance to gravitational separation. Nanoemulsions contain very small droplets (typically d < 200 nm), which leads to useful functional attributes, such as high optical clarity, resistance to gravitational separation and aggregation, rapid digestion, and high bioavailability. Multiple emulsions contain droplets that have smaller immiscible droplets inside them, which can be used for reduced-calorie, encapsulation, and delivery purposes. This new generation of advanced emulsions may lead to food and beverage products with improved quality, health, and sustainability.

Transparent films by ionic liquid welding of cellulose nanofibers and polylactide: Enhanced biodegradability in marine environments.

We introduce a green and facile method to compatibilize hydrophobic polylactide (PLA) with hydrophilic cellulose nanofibers (CNF) by using ionic liquid ([DBNH][OAc]) welding with a cosolvent system (gamma-valerolactone). Such welding affords strong (230 MPa tensile strength), flexible (13% elongation at break), transparent (>90%) and defect-free CNF/PLA films. The films are biodegradable in marine environments (70% degradation in 7 weeks), facilitating the otherwise slow PLA decomposition. Physical, chemical and structural features of the films before and after welding are compared and factored in the trends observed for degradation in seawater. The results point to the possibility of PLA-based films forming a co-continuous system with nanocellulose to achieve an improved performance. The role of film morphology, hydrophobicity, and crystallinity is discussed to add to the prospects for packaging materials that simultaneously display accelerated degradability in marine environments.

Pickering Emulsions via Interfacial Nanoparticle Complexation of Oppositely Charged Nanopolysaccharides.

We consider the variables relevant to adsorption of renewable nanoparticles and stabilization of multiphase systems, including the particle's hydrophilicity, electrostatic charge, axial aspect, and entanglement. Exploiting the complexation of two oppositely charged nanopolysaccharides, cellulose nanofibrils (CNFs) and nanochitin (NCh), we prepared CNF/NCh aqueous suspensions and identified the conditions for charge balance (turbidity and electrophoretic mobility titration). By adjusting the composition of CNF/NCh complexes, below and above net neutrality conditions, we produced sunflower oil-in-water Pickering emulsions with adjustable droplet diameters and stability against creaming and oiling-off. The adsorption of CNF/NCh complexes at the oil/water interface occurred with simultaneous partitioning (accumulation) of the CNF on the surface of the droplets in net negative or positive systems (below and above stochiometric charge balance relative to NCh). We further show that the morphology of the droplets and size distribution were preserved during storage for at least 6 months under ambient conditions. This long-term stability was held with a remarkable tolerance to changes in pH (e.g., 3-11) and ionic strength (e.g., 100-500 mM). The mechanism explaining these observations relates to the adsorption of the CNF in the complexes, counteracting the charge losses resulting from the deprotonation of NCh or charge screening. Overall, CNF/NCh complexes and the respective interfacial nanoparticle exchange greatly extend the conditions, favoring highly stable, green Pickering emulsions that offer potential in applications relevant to foodstuff, pharmaceutical, and cosmetic formulations.

Recent Advances in Food Emulsions and Engineering Foodstuffs Using Plant-Based Nanocelluloses.

In this article, the application of nanocelluloses, especially cellulose nanofibrils and cellulose nanocrystals, as functional ingredients in foods is reviewed. These ingredients offer a sustainable and economic source of natural plant-based nanoparticles. Nanocelluloses are particularly suitable for altering the physicochemical, sensory, and nutritional properties of foods because of their ability to create novel structures. For instance, they can adsorb to air-water or oil-water interfaces and stabilize foams or emulsions, self-assemble in aqueous solutions to form gel networks, and act as fillers or fat replacers. The functionality of nanocelluloses can be extended by chemical functionalization of their surfaces or by using them in combination with other natural food ingredients, such as biosurfactants or biopolymers. As a result, it is possible to create stimuli-responsive, tailorable, and/or active functional biomaterials suitable for a range of foodapplications. In this article, we describe the chemistry, structure, and physicochemical properties of cellulose as well as their relevance for the application of nanocelluloses as functional ingredients in foods. Special emphasis is given to their use as particle stabilizers in Pickering emulsions, but we also discuss their potential application for creating innovative biomaterials with novel functional attributes, such as edible films and packaging. Finally, some of the challenges associated with using nanocelluloses in foods are critically evaluated, including their potential safety and consumer acceptance.

High Internal Phase Oil-in-Water Pickering Emulsions Stabilized by Chitin Nanofibrils: 3D Structuring and Solid Foam .

Chitin nanofibrils (NCh, ∼10 nm lateral size) were produced under conditions that were less severe compared to those for other biomass-derived nanomaterials and used to formulate high internal phase Pickering emulsions (HIPPEs). Pre-emulsification followed by continuous oil feeding facilitated a "scaffold" with high elasticity, which arrested droplet mobility and coarsening, achieving edible oil-in-water emulsions with internal phase volume fraction as high as 88%. The high stabilization ability of rodlike NCh originated from the restricted coarsening, droplet breakage and coalescence upon emulsion formation. This was the result of (a) irreversible adsorption at the interface (wettability measurements by the captive bubble method) and (b) structuring in highly interconnected fibrillar networks in the continuous phase (rheology, cryo-SEM, and fluorescent microscopies). Because the surface energy of NCh can be tailored by pH (protonation of surface amino groups), emulsion formation was found to be pH-dependent. Emulsions produced at pH from 3 to 5 were most stable (at least for 3 weeks). Although at a higher pH NCh was dispersible and the three-phase contact angle indicated better interfacial wettability to the oil phase, the lower interdroplet repulsion caused coarsening at high oil loading. We further show the existence of a trade-off between NCh axial aspect and minimum NCh concentration to stabilize 88% oil-in-water HIPPEs: only 0.038 wt % (based on emulsion mass) NCh of high axial aspect was required compared to 0.064 wt % for the shorter one. The as-produced HIPPEs were easily textured by taking advantage of their elastic behavior and resilience to compositional changes. Hence, chitin-based HIPPEs were demonstrated as emulgel inks suitable for 3D printing (millimeter definition) via direct ink writing, e.g., for edible functional foods and ultralight solid foams displaying highly interconnected pores and for potential cell culturing applications.

All-Aqueous Liquid Crystal Nanocellulose Emulsions with Permeable Interfacial Assembly.

We report on the formation of water-in-water liquid crystal emulsions with permeable colloidal assemblies. Rodlike cellulose nanocrystals (CNC) spontaneously self-assemble into a helical arrangement with the coexistence of nonionic, hydrophilic polyethylene glycol (PEG) and dextran, whereas the two polymer solutions are thermodynamically incompatible. Stable water-in-water emulsions are easily prepared by mixing the respective CNC/polymer solutions, showing micrometric CNC/PEG dispersed droplets and a continuous CNC/dextran phase. With time, the resulting emulsion demixes into an upper, droplet-lean isotropic phase and a bottom, droplet-rich cholesteric phase. Owing to the osmotic pressure gradient between PEG and dextran phases, target transfer of cellulose nanoparticles occurs across the water/water interface to reassemble into a liquid crystal-in-liquid crystal emulsion with global cholesteric organization. The observed structural, optical, and temporal evolution confirm that the colloidal particles in the two immiscible phases experience short-range interactions and form long-range assemblies across the interface.