Lightweight, strong, and form-stable cellulose nanofibrils phase change aerogel with high latent heat

Biomass confined gradient porous Janus bacterial cellulose film integrating enhanced radiative cooling with perspiration-wicking for efficient thermal management

Sophisticated structure design and multi-step manufacturing processes for balancing spectra-selective optical property and the necessary applicable performance for human thermal-wet regulation, is the major limitation in wide application of radiative cooling materials. Herein, we proposed a biomass confinement strategy to a gradient porous Janus cellulose film for enhanced optical performance without compromising thermal-wet comfortable. The bacterial cellulose confined grow in the micro-nano pores between PP nonwoven fabric and SiO2 achieving the cross-scale gradient porous Janus structure. This structure enables the inorganic scatterers even distribution forming multi-reflecting optical mechanism, thereby, gradient porous Janus film demonstrates a reflectivity of 93.1 % and emissivity of 88.1 %, attains a sub-ambient cooling temperature difference of 2.8 °C(daytime) and 8.5 °C(night). Film enables bare skin to avoid overheating by 7.7 °C compared to cotton fabric. It reaches a 17.2 °C building cooling temperature under 1 sun radiance. Moreover, biomass confined micro-nano gradient porous structure integrating with Janus wet gradient guarantees the driven force for directional water transportation, which satisfies the thermal-wet comfortable demands for human cooling application without any further complicated process. Overall, bacterial cellulose based biomass confining strategy provides a prospective method to obtain outdoor-service performance in cooling materials.

Enhancing cellulose-stabilized multiphase/Pickering emulsions systems: A molecular dynamics perspective

Cellulose stabilized multiphase systems (CSMS) have garnered significant attention due to their ultra-stabilization mechanism and vast potential across different fields. CSMS have found valuable applications in scientific disciplines, including Food Science, Pharmaceutical Science, Material Science, and related fields, owing to their beneficial attributes such as sustainability, safety, renewability, and non-toxicity. Furthermore, MPS exhibit novel characteristics that enable multiple mechanisms to produce HIPEs, aerogels, and oleogels revealing undiscovered information. Therefore, to explore the undiscovered phenomena of MPS, molecular level insights using advanced simulation/computational approaches are essential. The molecular dynamics simulation (MDS), play a valuable role in analyzing the interactions of ternary interphase. The MDS have successfully quantified the interactions of MPS by generating, visualizing, and analyzing trajectories. Through MDS, researchers have explored CSMS at the molecular level and advanced their applications in 3D printing, packaging, preparation, drug delivery, encapsulation, biosensors, electronic devices, biomaterials, and energy conservation. This review highlights the remarkable advancements in CSMS over the past five years, along with contributions of MDS in evaluating the relationships that dictate the functionality and properties of CSMS. By integrating experimental and computational methods, we underscore the potential to innovate and optimize these multiphase systems for groundbreaking applications.

A review of high internal phase Pickering emulsions: Stabilization, rheology, and 3D printing application

High internal phase Pickering emulsion (HIPPE) is renowned for its exceptionally high-volume fraction of internal phase, leading to flocculated yet deformed emulsion droplets and unique rheological behaviors such as shear-thinning property, viscoelasticity, and thixotropic recovery. Alongside the inherent features of regular emulsion systems, such as large interfacial area and well-mixture of two immiscible liquids, the HIPPEs have been emerging as building blocks to construct three-dimensional (3D) scaffolds with customized structures and programmable functions using an extrusion-based 3D printing technique, making 3D-printed HIPPE-based scaffolds attract widespread interest from various fields such as food science, biotechnology, environmental science, and energy transfer. Herein, the recent advances in preparing suitable HIPPEs as 3D printing inks for various applied fields are reviewed. This work begins with the stabilization mechanism of HIPPEs, followed by introducing the origin of their distinctive rheological behaviors and strategies to adjust the rheological behaviors to prepare more eligible HIPPEs as printing inks. Then, the compatibility between extrusion-based 3D printing and HIPPEs as building blocks was discussed, followed by a summary of the potential applications using 3D-printed HIPPE-based scaffolds. Finally, limitations and future perspectives on preparing HIPPE-based materials using extrusion-based 3D printing were presented.

Superelastic Cellulose Sub-Micron Fibers/Carbon Black Aerogel for Highly Sensitive Pressure Sensing

Superelastic aerogels with rapid response and recovery times, as well as exceptional shape recovery performance even from large deformation, are in high demand for wearable sensor applications. In this study, a novel conductive and superelastic cellulose-based aerogel is successfully developed. The aerogel incorporates networks of cellulose sub-micron fibers and carbon black (SMF/CB) nanoparticles, achieved through a combination of dual ice templating assembly and electrostatic assembly methods. The incorporation of assembled cellulose sub-micron fibers imparts remarkable superelasticity to the aerogel, enabling it to retain 94.6% of its original height even after undergoing 10 000 compression/recovery cycles. Furthermore, the electrostatically assembled CB nanoparticles contribute to exceptional electrical conductivity in the cellulose-based aerogel. This combination of electrical conductivity and superelasticity results in an impressive response time of 7.7 ms and a recovery time of 12.8 ms for the SMF/CB aerogel, surpassing many of the aerogel sensors reported in previous studies. As a proof of concept, the SMF/CB aerogel is utilized to construct a pressure sensor and a sensing array, which exhibit exceptional responsiveness to both minor and substantial human motions, indicating its significant potential for applications in human health monitoring and human-machine interaction.

Cellulose Nanofibril Stabilized Pickering Emulsion Templated Aerogel with High Oil Absorption Capacity

Nanocellulose-based aerogels, featuring a three-dimensional porous structure, are considered as a desirable green absorbent because of their exceptional absorption performance as well as the abundance and renewability of the raw material. However, these aerogels often require hydrophobic modification or carbonization, which is often environmentally harmful and energy-intensive. In this study, we introduce a Pickering-emulsion-templating approach to fabricate a cellulose nanofibril (CNF) aerogel with a hierarchical pore structure, allowing for high oil absorption capacity. n-Hexane-CNF oil-in-water Pickering emulsions are prepared as an emulsion template, which is further lyophilized to create a hollow microcapsule-based CNF (HM-CNF) aerogel with a density ranging from 1.3 to 6.1 mg/cm3 and a porosity of ≥99.6%. Scanning electron microscopy and Brunauer-Emmett-Teller analyses reveal the HM-CNF aerogel's hierarchical pore structure, originating from the CNF Pickering emulsion template, and also confirm the aerogel's very high surface area of 216.6 m2/g with an average pore diameter of 8.6 nm. Furthermore, the aerogel exhibits a maximum absorption capacity of 354 g/g and 166 g/g for chloroform and n-hexadecane, respectively, without requiring any surface modification or chemical treatment. These combined findings highlight the potential of the Pickering-emulsion-templated CNF aerogel as an environmentally sustainable and high-performance oil absorbent.

Ti3C2Tx MXene and cellulose-based aerogel phase change composite decorated laminated fabric with excellent electro/solar-thermal conversion and high latent heat

Wearable heaters have attracted growing attention for maintaining a relatively constant temperature of the human body in cold environments with near zero energy consumption. Herein, we developed a multifunctional laminated fabric with fascinating electro/solar-thermal conversion, thermal energy storage and thermal insulation properties. With cotton fabric as the substrate, MXene/polydimethylsiloxane (PDMS) conductive network was decorated on the upper layer, and carbon nanotube (CNT)/cellulose nanofiber (CNF)/paraffin (PA) aerogel phase change composites were assembled on the bottom layer. Attributed to the strong conductivity and light absorption of MXene and the light/thermal response of CNT and PA components, this wearable laminated fabric broke the limitation of intermittent solar photothermal heating, and integrated multiple heating modes to precisely heat the human body. Meanwhile, the low thermal conductivity of aerogel retarded heat loss. The laminated fabric can help people better adapt to a variety of complex and changeable environments such as cold winter, rainy days and nights. This study provides a promising and energy-efficient avenue for the development of all-day personal thermal management fabrics.

Tuning interfacial microstructure of alginate-based amphiphile by dynamic bonding for stabilizing Pickering emulsion

Polysaccharide-based soft colloidal particles mediated by the dynamic bonding-engineered interfacial self-assembly can regulate the properties of oil-water interfacial films, availing the stability of emulsions under a wide pH range. The amphiphilic phenylboronic alginate soft colloidal particles (Alg-PBA) were designed to stabilize pH-responsive Pickering emulsions (PEs). Combining stability analysis with quartz crystal microbalance and dissipation monitoring (QCM-D), the microstructure and viscoelasticity of Alg-PBA at the oil-water interface were determined. The results showed that PEs stabilized by Alg-PBA due to a thicker and stronger viscoelastic interface film induced by BO bonds and hydrogen bonds. The structure-function relationship of the Alg-PBA emulsifier driven by dynamic bonds was further elaborated at multiple scales by laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Meanwhile, the microstructure of aerogels templated by emulsion could be tuned by adjusting dynamic bonds, which provides a new idea for polysaccharide soft material engineering.

Encapsulation of Paraffin Phase-Change Materials within Monolithic MTMS-Based Silica Aerogels

To address the leakage issue of paraffin phase-change materials in thermal management, a monolithic MTMS-based silica aerogel (MSA) is employed to encapsulate paraffin through a facile impregnation process. We find that the paraffin and MSA form a physical combination, with little interaction occurring between them. The prepared no-leakage paraffin/MSA composites have a density of 0.70 g/cm3 and exhibit good mechanical properties and nice hydrophobicity, with a contact angle of 122°. Furthermore, the average latent heat of the paraffin/MSA composites is found to reach up to 209.3 J/g, about 85% of the pure paraffin's latent heat, which is significantly larger than other paraffin/silica aerogel phase-change composite materials. The thermal conductivity of the paraffin/MSA remains almost the same as that of the pure paraffin (~250 mW/m/K), without any heat transfer interference from the MSA skeletons. All these results indicate that MSA can effectively serve as a carrier material for encapsulating paraffin, which is beneficial for expanding the applications of MSAs in thermal management and energy storage.

Cellulose-based, flexible polyurethane polyHIPEs with quasi-closed-cell structures and high stability for thermal insulation

Cellulose-based, closed-cell porous materials templated from emulsions are promising for thermal insulation, but their low stability imposed by physical interaction hinders the materials from real applications. Herein, we report the fabrication of cellulose-based, flexible polyurethane polyHIPEs with quasi-closed-cell structures, high stability and flexibility for thermal insulation. The polyHIPEs were prepared from cellulose-stabilized Pickering high internal phase emulsions through interfacial crosslinking using isocyanate. The resulting polyurethane polyHIPEs showed controllable external shapes, quasi-closed-cell structures, high flexibility, low density, and robust compression (without fracture even after compression to 30 % original height). The crosslinking enabled the polyHIPEs to show hydrophobicity, good stability (without breakage and dissolution observed after immersing in NaOH solution at pH 12, HCl solution at pH 1 and hot water at 100 °C, for 24 h) and decreased moisture uptake (below 1 %). The low density and quasi-closed-cell structures endowed the polyHIPEs with high thermal insulation, with thermal conductivity as low as 33.1 mW/(m K). These features make the cellulose-based, closed-cell polyHIPEs as an excellent candidate for thermal insulting.

Microencapsulated phase change material via Pickering emulsion based on xylan nanocrystal for thermoregulating application

Phase change materials (PCM) are promising for thermal regulation and energy storage, but suffer from the deformation and leakage of capsules. Herein, inspired by cellulose nanocrystal (CNC), xylan nanocrystal (XNC) with a dimension of 25-60 nm was successfully prepared through oxalic acid hydrolysis of high-crystalline xylan as raw materials via a top-down approach. With the introduction of hydrophobic groups, compared to XNC, succinylated XNC showed more remarkable emulsifying property over 7 days of storage at room temperature. Microencapsulated PCM composite consisting of sodium alginate (SA) as "matrix" and succinylated xylan nanocrystal (XNC) stabilized paraffin-based Pickering capsule (PCM beads) as "core" was facilely fabricated. PCM composite with the latent heat of 105.59 J·g^-1 showed excellent thermoregulating performance. Our work suggests a new pathway toward sustainability of hemicelluloses in the application of food emulsion and thermal energy management.

Wet spinning of strong cellulosic fibres with incorporation of phase change material capsules stabilized by cellulose nanocrystals

Incorporating a phase change material (PCM) into fibres allows the fabrication of smart textiles with thermo-regulating properties. Previously, such fibres have been made from thermoplastic polymers, usually petroleum-based and non-biodegradable, or from regenerated cellulose, such as viscose. Herein, strong fibres are developed from aqueous dispersions of nano-cellulose and dispersed microspheres with phase changing characteristics using a wet spinning technique employing a pH shift approach. Good distribution of the microspheres and proper compatibility with the cellulosic matrix was demonstrated by formulating the wax as a Pickering emulsion using cellulose nanocrystals (CNC) as stabilizing particles. The wax was subsequently incorporated into a dispersion of cellulose nanofibrils, the latter being responsible for the mechanical strength of the spun fibres. It was possible to produce fibres highly loaded with the microspheres (40 wt%) with a tenacity of 13 cN tex^-1 (135 MPa). The fibres possessed good thermo-regulating features by absorbing and releasing heat without undergoing structural changes, while maintaining the PCM domain sizes intact. Finally, good washing fastness and PCM leak resistance were demonstrated, making the fibres suitable for thermo-regulative applications. Continuous fabrication of bio-based fibres with entrapped PCMs may find applications as reinforcements in composites or hybrid filaments.

An all-cellulose sponge with a nanofiller-assisted hierarchical cellular structure for fruit maintaining freshness

Cellulose sponges with compressibility and resilience are an ideal packaging material for fruits with fragile skin. Here, a soft and elastic all-cellulose sponge (CS) with a hierarchical cellular structure was fabricated, where the long molecular chain cellulose constructed major pores, the cellulose at nanoscale acted as an elastic nanofiller to fill the gaps of long molecular chain cellulose fibers and constructed minor pores. With these two kinds of pores, this structure can absorb strain hierarchically. The sponge can protect fruits from mechanical damage when dropped or repeated vibration. Furthermore, the CS modified with chlorogenic acid (C-CGAS) had excellent antibacterial and antifungal abilities. Therefore, C-CGAS could extend the storage time of strawberries to 18 days without any microbial invasion, which is the longest storage time reported thus far. This study provides a new idea for the preparation of polymer sponges and a new design for the development of antimicrobial packaging materials.

Lipophilic Modified Hierarchical Multiporous rGO Aerogel-Based Organic Phase Change Materials for Effective Thermal Energy Storage

In the field of thermal energy storage, organic phase change materials (PCMs) are widely used as functional materials to boost thermal applications. However, there is often a tradeoff between constructing shape-stable composite PCMs with high enthalpy value and those with low leakage rates. Here, we proposed a promising scheme to address this issue. A novel hydrogel consisting of reduced graphene oxide (rGO) and covalent organic framework (COF) was prepared via hydrothermal methods, and the rGO-COF ultralight aerogel with a hierarchical porous structure was formed after freeze-drying. The rGO-COF aerogel shows excellent absorption ability and affinity for organic solvents. It can sufficiently adsorb the molten organic PCMs, such as polyethylene glycol (PEG), and synthesize shape-stable composite PCMs with excellent leak resistance. The COF grown on the surface of rGO has a superior affinity for PEG, so rGO-COF aerogel shows an outstanding PEG loading rate of up to 96.1 wt %, which is 1.7 wt % higher than that of rGO aerogel. In addition, the COF effectively reduces the subcooling of PEG/rGO-COF with 20.3%, compared to PEG/rGO. Meanwhile, the prepared PEG/rGO-COF exhibits extremely high enthalpy and relative enthalpy efficiency (164.6 J/g, 97.4%). This demonstrates that a promising direction was highlighte for the preparation of high-enthalpy shape-stable composite organic PCMs in this work.

Novel 3D Printing Phase Change Aggregate Concrete: Mechanical and Thermal Properties Analysis

The use of phase change materials (PCMs) in concrete is a double-edged sword that improves the thermal inertia but degrades the mechanical properties of concrete. It has been an essential but unsolved issue to enhance the thermal capacity of PCMs while non-decreasing their mechanical strength. To this end, this work designs a novel 3D printing phase change aggregate to prepare concrete with prominent thermal capacity and ductility. The work investigated the effects of 3D printing phase change aggregate on the compressive strength and splitting tensile strength of concrete. The compressive strength of phase change aggregate concrete is 21.18 MPa, but the ductility of concrete improves. The splitting tensile strength was 1.45 MPa. The peak strain is 11.69 × 10^-3, nearly 13 times that of basalt aggregate concrete. Moreover, using 3D printing phase change aggregate reduced concrete's early peak hydration temperature by 7.1%. The thermal insulation capacity of the experiment cube model with phase change concrete has been improved. The results show that the novel 3D printing change aggregate concrete has good mechanical properties and latent heat storage, providing a guideline for applying PCMs in building materials.

Mechanically Robust and Flexible GO/PI Hybrid Aerogels as Highly Efficient Oil Absorbents

Herein, mechanically robust and flexible graphene oxide/polyimide (GO/PI) hybrid aerogels (GIAs) were fabricated by a facile method, in which the mixed suspensions of the water-soluble polyimide precursor and graphene oxide (GO) sheets were freeze-dried, which was followed by a routine thermal imidation process. The porous GIAs obtained not only exhibit excellent elasticity and extremely low density values (from 33.3 to 38.9 mg.cm^-3), but they also possess a superior compressive strength (121.7 KPa). The GIAs could support a weight of up to 31,250 times of its own weight, and such a weight-carrying capacity is much higher than that of other typical carbon-based aerogels. Having such a porous structure, and high strength and toughness properties make GIAs ideal candidates for oil spill cleanup materials. The oil/organic solvents' absorption capacity ranges from 14.6 to 85, which is higher than that of most other aerogels (sponges). With their broad temperature tolerance and acidic stability, the unique multifunctional GIAs are expected to further extend their application range into extreme environments.

Aerogels Meet Phase Change Materials: Fundamentals, Advances, and Beyond

Benefiting from the inherent properties of ultralight weight, ultrahigh porosity, ultrahigh specific surface area, adjustable thermal/electrical conductivities, and mechanical flexibility, aerogels are considered ideal supporting alternatives to efficiently encapsulate phase change materials (PCMs) and rationalize phase transformation behaviors. The marriage of versatile aerogels and PCMs is a milestone in pioneering advanced multifunctional composite PCMs. Emerging aerogel-based composite PCMs with high energy storage density are accepted as a cutting-edge thermal energy storage (TES) concept, enabling advanced functionality of PCMs. Considering the lack of a timely and comprehensive review on aerogel-based composite PCMs, herein, we systematically retrospect the state-of-the-art advances of versatile aerogels for high-performance and multifunctional composite PCMs, with particular emphasis on advanced multiple functions, such as acoustic-thermal and solar-thermal-electricity energy conversion strategies, mechanical flexibility, flame retardancy, shape memory, intelligent grippers, and thermal infrared stealth. Emphasis is also given to the versatile roles of different aerogels in composite PCMs and the relationships between their architectures and thermophysical properties. This review also showcases the discovery of an interdisciplinary research field combining aerogels and 3D printing technology, which will contribute to pioneering cutting-edge PCMs. This review aims to arouse wider research interests among interdisciplinary fields and provide insightful guidance for the rational design of advanced multifunctional aerogel-based composite PCMs, thus facilitating the significant breakthroughs in both fundamental research and commercial applications.