Bean-Pod-Inspired 3D-Printed Phase Change Microlattices for Solar-Thermal Energy Harvesting and Storage

Green, recyclable and high latent heat form-stable phase change composites supported by cellulose nanofibers for thermal energy management

Efficiently addressing the challenge of leakage is crucial in the advancement of solid-liquid phase change thermal storage composite materials; however, numerous existing preparation methods often entail complexity and high energy consumption. Herein, a straightforward blending approach was adopted to fabricate stable phase change nanocomposites capitalizing on the interaction between TEMPO-oxidized cellulose nanofibers (TOCNF) and polyethylene glycol (PEG) molecules. By adjusting the ratio of TOCNF to PEG and the molecular weights of PEG, TOCNF/PEG phase change composites (TPCC) with customizable phase transition temperature (40.3-59.1 °C) and high phase transition latent heat (126.3-172.1 J/g) were obtained. The TPCC of high-loaded PEG (80-95 wt%) ensured a leakage rate of less than 1.7 wt% after 100 heating-cooling cycles. Moreover, TPCC exhibits excellent optical properties with a transmittance of over 90 % at room temperature and up to 96 % after heating. The thermal response analysis of TPCC demonstrates exceptional thermal-induced flexibility and good thermal stability, as well as recyclability and reshaping ability. This study may inspire others to design bio-based phase change composites with potential applications in thermal energy storage and management of smart-energy buildings, photothermal response devices, and waste heat-generating electronics.

Recent Progress and Perspectives of Direct Ink Writing Applications for Mass Transfer Enhancement in Gas-Phase Adsorption and Catalysis

Conventional adsorbents and catalysts shaped by granulation or extrusion have high pressure drop and poor flexibility for chemical, energy, and environmental processes. Direct ink writing (DIW), a kind of 3D printing, has evolved into a crucial technique for manufacturing scalable configurations of adsorbents and catalysts with satisfactory programmable automation, highly optional materials, and reliable construction. Particularly, DIW can generate specific morphologies required for excellent mass transfer kinetics, which is essential in gas-phase adsorption and catalysis. Here, DIW methodologies for mass transfer enhancement in gas-phase adsorption and catalysis, covering the raw materials, fabrication process, auxiliary optimization methods, and practical applications are comprehensively summarized. The prospects and challenges of DIW methodology in realizing good mass transfer kinetics are discussed. Ideal components with a gradient porosity, multi-material structure, and hierarchical morphology are proposed for future investigations.

Phase Change Thermal Storage Materials for Interdisciplinary Applications

Functional phase change materials (PCMs) capable of reversibly storing and releasing tremendous thermal energy during the isothermal phase change process have recently received tremendous attention in interdisciplinary applications. The smart integration of PCMs with functional supporting materials enables multiple cutting-edge interdisciplinary applications, including optical, electrical, magnetic, acoustic, medical, mechanical, and catalytic disciplines etc. Herein, we systematically discuss thermal storage mechanism, thermal transfer mechanism, and energy conversion mechanism, and summarize the state-of-the-art advances in interdisciplinary applications of PCMs. In particular, the applications of PCMs in acoustic, mechanical, and catalytic disciplines are still in their infancy. Simultaneously, in-depth insights into the correlations between microscopic structures and thermophysical properties of composite PCMs are revealed. Finally, current challenges and future prospects are also highlighted according to the up-to-date interdisciplinary applications of PCMs. This review aims to arouse broad research interest in the interdisciplinary community and provide constructive references for exploring next generation advanced multifunctional PCMs for interdisciplinary applications, thereby facilitating their major breakthroughs in both fundamental researches and commercial applications.

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.

Use of biochar co-mediated chitosan mesopores to encapsulate alkane and improve thermal properties

Phase-change materials (PCMs) plays a significant role in energy conservation and thermal management systems. However, excessive seepage and insufficient thermal conductivity of pristine PCMs are restricting its real-world applications. Herein, "anisotropic-like" biochar with favorable pore characteristics is designed by combining it with chitosan for dodecane encapsulation. The use of biochar could overcome high manufacturing costs and associated environmental issues of PCM supporting materials. Biochar co-mediated chitosan enrich the mesopore proportion (96.5%) and provide interactive synergistic architecture. The prepared composite PCM exhibited outstanding latent heat retention of 95.9% after repeated cycling, high loading ratio, enhanced thermal conductivity (0.373 W/(m·K)), leakage-free, and repeatable utilization properties above the melting point of pristine dodecane. A figure of merit of 33.94 × 10⁶ W² S/(m^4oC) was achieved, far surpassing that measure among reported biochar-based composite PCMs. This study provides insights into next-generation sustainable energy storage development for a key global sustainability goal.

D-Mannitol/Graphene Phase-Change Composites with Structured Conformation and Thermal Pathways Allow Durable Solar-Thermal-Electric Conversion and Electricity Output

Durable electricity generation from a phase-change material (PCM)-assisted solar thermoelectric generator (STEG) through photo-thermal-electric conversion is a promising way to take advantage of the clean solar energy. However, due to the deficient and mismatched thermal charging and discharging rates in the PCMs, the previous PCM-supported STEGs usually exhibit inefficient solar-thermal-electric conversion (<1%) and limited electricity output. In this work, we report a structured D-mannitol/graphene phase-change composite fabricated by a radial ice-template assembly and infiltration strategy, in which radially aligned graphene nanoplates are bridged by graphitized polyimide that offers multidirectional and interlaced thermal highways for rapid thermal charging, while the sample conformation is further regulated by the ice-template mold, promising the optimal charging and discharging balance in the PCM. After being integrated with a solar concentrator and a thermoelectric device, this powerful STEG outputs tremendous power density, with the solar-thermal-electric conversion approaching 2.40%. The plenteous electricity supply is demonstrated to reliably charge a mobile phone under normal sunlight. This elaborate STEG design opens up opportunities for providing sufficient power guarantees for the self-powering of electronic devices in the wild.

3D-Printed Flexible Phase-Change Nonwoven Fabrics toward Multifunctional Clothing

Functional phase-change fabrics hold great promise as wearable clothing. However, how to enable a phase-change fabric with the combined features of excellent structural flexibility and robustness, integrated multifunctionality, superior stability, and durability, as well as facile and scalable manufacturing, still remains a significant challenge. Herein, we demonstrated a scalable and controllable three-dimensional (3D) printing strategy for manufacturing flexible, thin, and robust phase-change nonwoven fabric (PCNF), with abundant and regular breathable pores as well as uniform and tight embedment of highly interconnected single-walled carbon nanotubes (SWNTs) into hydrophobic filaments built by intertwining solid-solid phase-change polymer chains together. The remarkable architectural features enabled an integral whole of the fabric, ready air exchange, superior water impermeability, highly efficient heat harvesting and storage, and effective absorption and reflection of electromagnetic waves, thereby delivering an exceptional combined function of breathability, waterproofness, thermal regulation, and radiation resistance, and meanwhile featuring superior thermal stability and outstanding resistance to stretching/folding fatigue even at cycles up to 2000. This work sheds light on effective strategies for manufacturing wearable phase-change fabrics with multifunctionality and high stability in a scalable manner toward future uses.

Electrospun Shape-Stabilized Phase Change Materials Based on Photo-Crosslinked Polyethylene Oxide

Phase change materials (PCMs) in the form of fibers or fibrous mats with exceptional thermal energy storage ability and tunable working temperature are of high interest to produce smart thermoregulating textiles, useful for increasing human thermal comfort while avoiding energy waste. Common organic PCMs suffer from instability in their molten state, which limits their applicability as highly performing fibrous systems. In this work, electrospun fibrous mats made of polyethylene oxide (PEO), a PCM with excellent thermal properties and biocompatibility, were fabricated and their shape instability in the molten state was improved through UV photo-crosslinking. The characterization aimed to assess the performance of these shape-stable electrospun mats as nanofibrous PCMs for thermal management applications. In addition to an enhanced resistance to water-based solvents, UV-cured electrospun PEO mats demonstrated a remarkable latent heat (≈112 J/g), maintained over 80 heating/cooling cycles across the phase change temperature. Moreover, their morphological stability above their melting point was demonstrated both macroscopically and microscopically, with the retention of the initial nanofibrous morphology. Tensile mechanical tests demonstrated that the UV crosslinking considerably enhanced the ultimate properties of the fibrous mat, with a five-fold increase in both the tensile strength (from 0.15 MPa to 0.74 MPa) and the strain at break (from 2.5% to 12.2%) compared to the uncrosslinked mat. In conclusion, the photo-crosslinked electrospun PEO material exhibited high thermal properties and good shape stability without displaying leakage; accordingly, in the proposed PCM system, the necessity for encapsulation or use of a supporting layer has been eliminated. Photo-crosslinking thus proved itself as an effective, fast, and environmentally friendly method to dramatically improve the shape-stability of nanofibrous PEO electrospun mats for smart thermoregulating textiles.