A Liquid Metal Microdroplets Initialized Hemicellulose Composite for 3D Printing Anode Host in Zn-Ion Battery

Flexible and weavable secondary Zn-MnO2 batteries derived from cellulose of Juncus effusus

To keep pace with the fast development of portable and wearable electronics, considerable public and scientific attentions have been paid to the flexible energy storage devices with characteristics of light weight, low cost and high electrochemical performance. In this work, we demonstrate a feasible strategy to fabricate novel strand-shaped electrodes from the biomass of Juncus effusus (JE), which can be easily integrated into flexible and rechargeable Zn-MnO2 batteries with high electrochemical performance. Notably, JE has a very unique three dimensional (3D) triangular-like hollow network microstructure, which greatly favors active material loading, charge transfer and ion diffusion. The obtained aqueous battery presents an excellent specific capacity of 325 mAh g-1 at the current density of 0.3 A g-1, as well as stunning cycling stability for up to 4000 cycles with 127.53 % retention of the initial capacity. Remarkably, when assembled with a gel electrolyte, the quasi-solid-state battery can work normally under various extreme conditions, including bending, hammering, burning, soaking and puncturing. In addition, due to the high flexibility, the electrodes can be woven in parallel into a textile to form an energy supply unit and successfully power an electronic watch, demonstrating high potential of JE in the fabrication of flexible energy storage devices.

Liquid metal anode enables zinc-based flow batteries with ultrahigh areal capacity and ultralong duration

Zinc-based flow batteries (Zn-FBs) are promising candidates for large-scale energy storage because of their intrinsic safety and high energy density. Unlike that conventional flow batteries operate on the basis of liquid-liquid conversions, the Zn anode in Zn-FBs adopts a solid-liquid conversion reaction, presenting challenges such as dendrite formation, poor reversibility, and low areal capacity, limiting its long-duration energy storage (LDES) applications. Here, we developed a liquid metal (LM) electrode that evolves the deposition/dissolution reaction of Zn into an alloying/dealloying process within the LM, thereby achieving extraordinary areal capacity and dendrite-free Zn-FBs with outstanding cycling stability. Both Zn-I2 and Zn-Br2 flow batteries using LM electrodes exhibited an ultrahigh areal capacity of 640 milliampere-hours per square centimeter, corresponding to an ultralong discharge duration of ~16 hours, thus exceeding the LDES standard defined by the US Department of Energy. This study breaks the solid-liquid working mode of the Zn anode, offering an effective solution for LDES applications with Zn-FBs.

3D Printed Low-Tortuosity and Ultra-Thick Hierarchical Porous Electrodes for High-Performance Wearable Quasi-Solid-State Zn-VOH Batteries

Rechargeable aqueous Zn-ion batteries have received considerable attention in energy storage systems owing to their merits of high safety, low cost, and excellent rate performance. However, the unsatisfactory areal energy density and poor cycling performance hinder their practical applications. Herein, the V5O12·6H2O (VOH) nanosheet arrays and Zn nanoflake arrays growing on the 3D-printed reduced graphene oxide/carbon nanotubes (3DP-rGO/CNTs) microlattices employing the electrodeposition technique, and further serve as the cathode and anode for 3D-printed aqueous Zn-VOH battery, respectively. Benefiting from 3D-printed low-tortuosity and ultra-thick hierarchical porous electrodes, the battery-type VOH-based cathode enables fast Zn2+ reaction kinetics and electrodeposited Zn-based anode delivers highly reversible Zn stripping/plating. The button-type 3D-printed aqueous Zn-VOH battery exhibits excellent energy/power densities (364.5 Wh kg-1 at 700 W kg-1) and remarkable cycling performance over 6500 cycles. Impressively, a customizable 3D-printed quasi-solid-state Zn-VOH battery device is fabricated, which presents ultrahigh areal capacity (≈17.06 mAh cm-2 at 0.2 mA cm-2), long-term durability (≈85.6% capacity retention after 10 000 cycles), and excellent wearable characters. This work provides a novel strategy to gain high-performance Zn-ion batteries based on 3D-printed electrodes, which may pave a new way for the applications of various high-performance, low-cost, and portable integrated energy storage systems.

High-Resolution Stretchable Soft Liquid Metal Circuits Based on Cu-Ga Alloying and Femtosecond Laser Ablation

Flexible electronic circuits are critical in biomedical devices, human-machine interfaces, and wearable sensing systems, which further require flexible conductive materials with high conductivity, stretchability, and electrical stability. Liquid metal (LM) has attracted much attention due to its unique metallic conductivity and room-temperature fluidic properties. However, LM's high surface tension properties increase the difficulty of patterning processing. Here, we report a scalable and simple fabrication method based on femtosecond laser ablation for the facile fabrication of patterned LM and Cu composite electrodes (LM@Cu) on flexible substrates. The LM@Cu electrodes, fabricated utilizing the exceptional micro-nanoprocessing precision and three-dimensional fabrication capabilities of femtosecond lasers, exhibit high resolution (approximately 5 μm), superior electrical conductivity (4.08 × 104 S/cm), and enhanced stability. In addition to planar circuits, we successfully fabricated 3D-patterned LM@Cu electrode circuits on PDMS hemispheres. The presence of ultrathin copper foils significantly improves the wettability of LM on the substrate, and the occurrence of alloying reactions between LM and Cu circumvents the challenges posed by the high surface tension of LM in pattern fabrication. We further investigated the electromechanical properties of the patterned LM@Cu electrodes under twisting, bending, and stretching in detail. In addition, the LM@Cu electrodes serve as an interface between rigid electronic devices and flexible substrates. When suffering external damage, LM@Cu electrodes remain working after simple brush coating due to the excellent fluidity of LM. To explore this fabrication approach's potential, we demonstrate various applications in wearable electronics, including stretchable luminous wristbands, flexible wearable strain sensors, and "visible" thermotherapy panels for relieving aching joints.

Lignocellulose-Mediated Functionalization of Liquid Metals toward the Frontiers of Multifunctional Materials

Lignocellulose-mediated liquid metal (LM) composites, as emerging functional materials, show tremendous potential for a variety of applications. The abundant hydroxyl, carboxyl, and other polar groups in lignocellulose facilitate the formation of strong chemical bonds with LM surfaces, enhancing wettability and adhesion for improved interface compatibility. Beyond serving as a supportive matrix, lignocellulose can be tailored to optimize the microstructure of the composites, adapting them for diverse applications. This review comprehensively summarizes the fundamental principles and recent advancements in lignocellulose-mediated LM composites, highlighting the advantages of lignocellulose in composite fabrication, including facile synthesis, versatile interactions, and inherent functionalities. Key modulation strategies for LMs and innovative synthesis methods for functionalized lignocellulose composites are discussed. Furthermore, the roles and structure-performance relationships of these composites in electromagnetic shielding, flexible sensors, and energy storage devices are systematically summarized. Finally, the obstacles and prospective advancements pertaining to lignocellulose-mediated LM composites are thoroughly scrutinized and deliberated upon. This review is expected to provide basic guidance for researchers to boost the popularity of LMs in diverse applications and provide useful references for design strategies of state-of-the-art LMs.

Cellulose nanofibers/liquid metal hydrogels with high tensile strength, environmental adaptability and electromagnetic shielding for temperature monitoring and strain sensors

Hydrogel sensors are widely recognized in the fields of flexible electronics and human motion monitoring due to their multiple properties and potential applications. However, how to prepare hydrogels with multiple excellent properties simultaneously and how to improve the compatibility of conductive fillers with hydrogel matrices remain a major challenge. Therefore, in this work, liquid metal (LM) droplets stabilized by cellulose nanofibers (CNFs) were utilized to initiate the polymerization of acrylamide monomer (Am), which was used as a conductive filler. Meanwhile, reduced graphene oxide (rGO) was introduced to bridge the LM droplets. The hydrogels were then further crosslinked in glycerol. The constructed CNF@LM/polyacrylamide/rGO/gelatin/glycerol hydrogel possesses high tensile properties (>1317 %), high environmental adaptability (-80 to 80 °C), and adhesion properties for multifunctional sensing. What's more, it offers the high sensitivity of both a strain sensor and a temperature sensor for accurate monitoring of human movement at room temperature and even in extreme environments. In addition, this hydrogel has excellent electromagnetic shielding properties and antimicrobial properties. This research opens up a new direction for the preparation of multifunctional hydrogel sensors, expanding their applications in cutting-edge fields such as temperature monitoring, wearable smart devices, e-skin and intelligent robotics.

Multi-Group Polymer Coating on Zn Anode for High Overall Conversion Efficiency Photorechargeable Zinc-Ion Batteries

The solar-driven photorechargeable zinc-ion batteries have emerged as a promising power solution for smart electronic devices and equipment. However, the subpar cyclic stability of the Zn anode remains a significant impediment to their practical application. Herein, poly(diethynylbenzene-1,3,5-triimine-2,4,6-trione) (PDPTT) was designed as a functional polymer coating of Zn. Theoretical calculations demonstrate that the PDPTT coating not only significantly homogenizes the electric field distribution on the Zn surface, but also promotes the ion-accessible surface of Zn. With multiple N and C=O groups exhibiting strong adsorption energies, this polymer coating reduces the nucleation overpotential of Zn, alters the diffusion pathway of Zn2+ at the anode interface, and decreases the corrosion current and hydrogen evolution current. Leveraging these advantages, Zn-PDPTT//Zn-PDPTT exhibits an exceptionally long cycling time (≥4300 h, 1 mA cm-2). Zn-PDPTT//AC zinc-ion hybrid capacitors can withstand 50,000 cycles at 5 A/g. Zn-PDPTT//NVO zinc-ion battery exhibits a faster charge storage rate, higher capacity, and excellent cycling stability. Coupling Zn-PDPTT//NVO with high-performance perovskite solar cells results in a 13.12 % overall conversion efficiency for the photorechargeable zinc-ion battery, showcasing significant value in advancing the efficiency and upgrading conversion of renewable energy utilization.

Improvements and Challenges of Hydrogel Polymer Electrolytes for Advanced Zinc Anodes in Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are widely regarded as desirable energy storage devices due to their inherent safety and low cost. Hydrogel polymer electrolytes (HPEs) are cross-linked polymers filled with water and zinc salts. They are not only widely used in flexible batteries but also represent an ideal electrolyte candidate for addressing the issues associated with the Zn anode, including dendrite formation and side reactions. In HPEs, an abundance of hydrophilic groups can form strong hydrogen bonds with water molecules, reducing water activity and inhibiting water decomposition. At the same time, special Zn2+ transport channels can be constructed in HPEs to homogenize the Zn2+ flux and promote uniform Zn deposition. However, HPEs still face issues in practical applications, including poor ionic conductivity, low mechanical strength, poor interface stability, and narrow electrochemical stability windows. This Review discusses the issues associated with HPEs for advanced AZIBs, and the recent progresses are summarized. Finally, the Review outlines the opportunities and challenges for achieving high performance HPEs, facilitating the utilization of HPEs in AZIBs.

Volume-Metallization 3D-Printed Polymer Composites

3D printing polymer or metal can achieve complicated structures while lacking multifunctional performance. Combined printing of polymer and metal is desirable and challenging due to their insurmountable mismatch in melting-point temperatures. Here, a novel volume-metallization 3D-printed polymer composite (VMPC) with bicontinuous phases for enabling coupled structure and function, which are prepared by infilling low-melting-point metal (LM) to controllable porous configuration is reported. Based on vacuum-assisted low-pressure conditions, LM is guided by atmospheric pressure action and overcomes surface tension to spread along the printed polymer pore channel, enabling the complete filling saturation of porous structures for enhanced tensile strength (up to 35.41 MPa), thermal (up to 25.29 Wm-1K-1) and electrical (>106 S m-1) conductivities. The designed 3D-printed microstructure-oriented can achieve synergistic anisotropy in mechanics (1.67), thermal (27.2), and electrical (>1012) conductivities. VMPC multifunction is demonstrated, including customized 3D electronics with elevated strength, electromagnetic wave-guided transport and signal amplification, heat dissipation device for chip temperature control, and storage components for thermoelectric generator energy conversion with light-heat-electricity.

Suitable Stereoscopic Configuration of Electrolyte Additive Enabling Highly Reversible and High-Rate Zn Anodes

Electrolyte additive engineering is a crucial method for enhancing the performance of aqueous zinc-ion batteries (AZIBs). Recently, most research predominantly focuses on the role of functional groups in regulating electrolytes, often overlooking the impact of molecule stereoscopic configuration. Herein, two isomeric sugar alcohols, mannitol and sorbitol, are employed as electrolyte additives to investigate the impact of the stereoscopic configuration of additives on the ZnSO4 electrolyte. Experimental analysis and theoretical calculations reveal that the primary factor for improving Zn anode performance is the regulation of the solvation sheath by these additives. Among the isomers, mannitol exhibits stronger binding energies with Zn2+ ions and water molecules due to its more suitable stereoscopic configuration. These enhanced bindings allow mannitol to coordinate with Zn2+, contributing to solvation structure formation and reducing the active H2O molecules in the bulk electrolyte, resulting in suppressed parasitic reactions and inhibited dendritic growth. As a result, the zinc electrodes in mannitol-modified electrolyte exhibit excellent cycling stability of 1600 h at 1 mA cm-2 and 900 h at 10 mA cm-2, respectively. Hence, this study provides novel insights into the importance of suitable stereoscopic molecule configurations in the design of electrolyte additives for highly reversible and high-rate Zn anodes.

Viscoelastic Adhesive, Super-Conformable, and Semi-Flowable Liquid Metal Eutectogels for High-Fidelity Electrophysiological Monitoring

Integrating gels with human skin through wearables provides unprecedented opportunities for health monitoring technology and artificial intelligence. However, most conductive hydrogels, organogels, and ionogels lack essential environmental stability, biocompatibility, and adhesion for reliable epidermal sensing. In this study, we have developed a liquid metal eutectogel simultaneously possessing superior viscoelasticity, semiflowability, and mechanical rigidity for low interfacial skin impedance, high skin adhesion, and durability. Liquid metal particles (LMPs) are employed to generate free radicals and gallium ions to accelerate the polymerization of acrylic acid monomers in a deep eutectic solvent (DES), obtaining highly viscoelastic polymer networks via physical cross-linking. In particular, graphene oxide (GO) is utilized to encapsulate the LMPs through a sonication-assisted electrostatic assembly to stabilize the LMPs in DES, which also enhances the mechanical toughness and regulates the rheological properties of the eutectogels. Our optimized semi-flowable eutectogel exhibits viscous fluid behavior at low shear rates, facilitating a highly conformable interface with hairy skin. Simultaneously, it demonstrates viscoelastic behavior at high shear rates, allowing for easy peel-off. These distinctive attributes enable the successful applications of on-skin adhesive strain sensing and high-fidelity human electrophysiological (EP) monitoring, showcasing the versatility of these ionically conductive liquid metal eutectogels in advanced personal health monitoring.

3D printed energy devices: generation, conversion, and storage

The energy devices for generation, conversion, and storage of electricity are widely used across diverse aspects of human life and various industry. Three-dimensional (3D) printing has emerged as a promising technology for the fabrication of energy devices due to its unique capability of manufacturing complex shapes across different length scales. 3D-printed energy devices can have intricate 3D structures for significant performance enhancement, which are otherwise impossible to achieve through conventional manufacturing methods. Furthermore, recent progress has witnessed that 3D-printed energy devices with micro-lattice structures surpass their bulk counterparts in terms of mechanical properties as well as electrical performances. While existing literature focuses mostly on specific aspects of individual printed energy devices, a brief overview collectively covering the wide landscape of energy applications is lacking. This review provides a concise summary of recent advancements of 3D-printed energy devices. We classify these devices into three functional categories; generation, conversion, and storage of energy, offering insight on the recent progress within each category. Furthermore, current challenges and future prospects associated with 3D-printed energy devices are discussed, emphasizing their potential to advance sustainable energy solutions.

The status and challenging perspectives of 3D-printed micro-batteries

In the era of the Internet of Things and wearable electronics, 3D-printed micro-batteries with miniaturization, aesthetic diversity and high aspect ratio, have emerged as a recent innovation that solves the problems of limited design diversity, poor flexibility and low mass loading of materials associated with traditional power sources restricted by the slurry-casting method. Thus, a comprehensive understanding of the rational design of 3D-printed materials, inks, methods, configurations and systems is critical to optimize the electrochemical performance of customizable 3D-printed micro-batteries. In this review, we offer a key overview and systematic discussion on 3D-printed micro-batteries, emphasizing the close relationship between printable materials and printing technology, as well as the reasonable design of inks. Initially, we compare the distinct characteristics of various printing technologies, and subsequently emphatically expound the printable components of micro-batteries and general approaches to prepare printable inks. After that, we focus on the outstanding role played by 3D printing design in the device architecture, battery configuration, performance improvement, and system integration. Finally, the future challenges and perspectives concerning high-performance 3D-printed micro-batteries are adequately highlighted and discussed. This comprehensive discussion aims at providing a blueprint for the design and construction of next-generation 3D-printed micro-batteries.

Green and Low-Cost Alkali-Polyphenol Synergetic Self-Catalysis System Access to Fast Gelation of Self-Healable and Self-Adhesive Conductive Hydrogels for Self-Powered Triboelectric Nanogenerators

Biomass-based hydrogels have attracted great attention in flexible and sustainable self-powered power sources but struggled to fabricate in a green, high-efficiency, and low-cost manner. Herein, a novel and facile alkali-polyphenol synergetic self-catalysis system is originally employed for the fast gelation of self-healable and self-adhesive lignin-based conductive hydrogels, which can be regarded as hydrogel electrodes of flexible triboelectric nanogenerators (TENGs). This synergy self-catalytic system comprises aqueous alkali and polyphenol-containing lignin, in which alkali-activated ammonium persulfate (APS) significantly accelerates the generation of radicals and initiates the polymerization of monomers, while polyphenol acts as a stabilizer to avoid bursting polymerization from inherent radical scavenging ability. Furthermore, multiple hydrogen bonds between lignin biopolymers and polyacrylamide (PAM) chains impart lignin-based hydrogels with exceptional adhesiveness and self-healing properties. Intriguingly, the alkaline conditions not only contribute to the solubility of lignin but also impart superior ionic conductivity of lignin-based hydrogel that is applicable to flexible TENG in self-powered energy-saving stair light strips, which holds great promise for industrial applications of soft electronics.

Current significance and future perspective of 3D-printed bio-based polymers for applications in energy conversion and storage system

The increasing global population has led to a surge in energy demand and the production of environmentally harmful products, highlighting the urgent need for renewable and clean energy sources. In this context, sustainable and eco-friendly energy production strategies have been explored to mitigate the adverse effects of fossil fuel consumption to the environment. Additionally, efficient energy storage devices with a long lifespan are also crucial. Tailoring the components of energy conversion and storage devices can improve overall performance. Three-dimensional (3D) printing provides the flexibility to create and optimize geometrical structure in order to obtain preferable features to elevate energy conversion yield and storage capacitance. It also serves the potential for rapid and cost-efficient manufacturing. Besides that, bio-based polymers with potential mechanical and rheological properties have been exploited as material feedstocks for 3D printing. The use of these polymers promoted carbon neutrality and environmentally benign processes. In this perspective, this review provides an overview of various 3D printing techniques and processing parameters for bio-based polymers applicable for energy-relevant applications. It also explores the advances and current significance on the integration of 3D-printed bio-based polymers in several energy conversion and storage components from the recently published studies. Finally, the future perspective is elaborated for the development of bio-based polymers via 3D printing techniques as powerful tools for clean energy supplies towards the sustainable development goals (SDGs) with respect to environmental protection and green energy conversion.

Liquid Metal-Based Stable and Stretchable Zn-Ion Battery for Electronic Textiles

Electronic textiles harmoniously interact with the human body and the surrounding environment, offering tremendous interest in smart wearable electronics. However, their wide application faces challenges due to the lack of stable and stretchable power electrodes/devices with multifunctional design. Herein, an intrinsically stretchable liquid metal-based fibrous anode for a stable Zn-ion battery (ZIB) is reported. Benefiting from the liquid feature and superior deformability of the liquid metal, optimized Zn ion concentration distribution and Zn (002) deposition behavior are observed, which result in dendrite-free performance even under stretching. With a strain of 50%, the ZIB maintains a high capacity of 139.8 mAh cm-3 (corresponding to 83.0% of the initial value) after 300 cycles, outperforming bare Zn fiber-based ZIB. The fibrous ZIB seamlessly integrates with the sensor, Joule heater, and wirelessly charging device, which provides a stable power supply for human signal monitoring and personal thermal management, holding promise for the application of wearable multifunctional electronic textiles.

Three-Dimensional Printing of Multifunctional Composites: Fabrication, Applications, and Biodegradability Assessment

Additive manufacturing, with its wide range of printable materials, and ability to minimize material usage, reduce labor costs, and minimize waste, has sparked a growing enthusiasm among researchers for the production of advanced multifunctional composites. This review evaluates recent reports on polymer composites used in 3D printing, and their printing techniques, with special emphasis on composites containing different types of additives (inorganic and biomass-derived) that support the structure of the prints. Possible applications for additive 3D printing have also been identified. The biodegradation potential of polymeric biocomposites was analyzed and possible pathways for testing in different environments (aqueous, soil, and compost) were identified, including different methods for evaluating the degree of degradation of samples. Guidelines for future research to ensure environmental safety were also identified.

Direct Ink Writing 3D Printing for High-Performance Electrochemical Energy Storage Devices: A Minireview

Despite tremendous efforts that have been dedicated to high-performance electrochemical energy storage devices (EESDs), traditional electrode fabrication processes still face the daunting challenge of limited energy/power density or compromised mechanical compliance. 3D thick electrodes can maximize the utilization of z-axis space to enhance the energy density of EESDs but still suffer from limitations in terms of poor mechanical stability and sluggish electron/ion transport. Direct ink writing (DIW), an eminent branch of 3D printing technology, has gained popularity in the manufacture of 3D electrodes with intricately designed architectures and rationally regulated porosity, promoting a triple boost in areal mass loading, ion diffusion kinetics, and mechanical flexibility. This focus review highlights the fundamentals of printable inks and typical configurations of 3D-printed devices. In particular, preparation strategies for high-performance and multifunctional 3D-printed EESDs are systemically discussed and classified according to performance evaluation metrics such as high areal energy density, high power density, high volumetric energy density, and mechanical flexibility. Challenges and prospects for the fabrication of high-performance 3D-printed EESDs are outlined, aiming to provide valuable insights into this thriving field.

Patterned Liquid-Metal-Enabled Universal Soft Electronics (PLUS-E) for Deformation Sensing on 3D Curved Surfaces

Liquid metals with metallic conductivity and infinitely deformable properties have tremendous potential in the field of conformal electronics. However, most processing methods of liquid metal electronics require sophisticated apparatus or custom masks, resulting in high processing costs and intricate preparation procedures. This study proposes a simple and rapid preparation method for patterned liquid-metal-enabled universal soft electronics (PLUS-E). The utilization of selective adhesion of the liquid metals on stretchable substrates and the adaptive toner mask enables rapid fabrication (<2 s/100 cm2), excellent stretchability (800% strain), and high forming accuracy (100 μm). Benefiting from the adaptive deformation of the substrate and toner mask, PLUS-E can be conformally applied to any shape of 3D surfaces. Besides, the stability of PLUS-E on 3D surfaces is improved by low-fluidity liquid metal composites. The finite element simulation is used to accurately forecast the deformation and resistance changes of the PLUS-E, and it provides guidance for device design and manufacturing. Finally, this method was utilized to develop various sensors for detecting human motion, catheter bending, and balloon expansion. All of them have obtained stable and reliable signal measurements, demonstrating the usefulness of PLUS-E in real-world applications.

Innovative Polymer Composites with Natural Fillers Produced by Additive Manufacturing (3D Printing)-A Literature Review

In recent years, plastics recycling has become one of the leading environmental and waste management issues. Along with the main advantage of plastics, which is undoubtedly their long life, the problem of managing their waste has arisen. Recycling is recognised as the preferred option for waste management, with the aim of reusing them to create new products using 3D printing. Additive manufacturing (AM) is an emerging and evolving rapid tooling technology. With 3D printing, it is possible to achieve lightweight structures with high dimensional accuracy and reduce manufacturing costs for non-standard geometries. Currently, 3D printing research is moving towards the production of materials not only of pure polymers but also their composites. Bioplastics, especially those that are biodegradable and compostable, have emerged as an alternative for human development. This article provides a brief overview of the possibilities of using thermoplastic waste materials through the application of 3D printing, creating innovative materials from recycled and naturally derived materials, i.e., biomass (natural reinforcing fibres) in 3D printing. The materials produced from them are ecological, widely available and cost-effective. Research activities related to the production of bio-based materials have gradually increased over the last two decades, with the aim of reducing environmental problems. This article summarises the efforts made by researchers to discover new innovative materials for 3D printing.

Biomass 3D Printing: Principles, Materials, Post-Processing and Applications

Under the background of green and low-carbon era, efficiently utilization of renewable biomass materials is one of the important choices to promote ecologically sustainable development. Accordingly, 3D printing is an advanced manufacturing technology with low energy consumption, high efficiency, and easy customization. Biomass 3D printing technology has attracted more and more attentions recently in materials area. This paper mainly reviewed six common 3D printing technologies for biomass additive manufacturing, including Fused Filament Fabrication (FFF), Direct Ink Writing (DIW), Stereo Lithography Appearance (SLA), Selective Laser Sintering (SLS), Laminated Object Manufacturing (LOM) and Liquid Deposition Molding (LDM). A systematic summary and detailed discussion were conducted on the printing principles, common materials, technical progress, post-processing and related applications of typical biomass 3D printing technologies. Expanding the availability of biomass resources, enriching the printing technology and promoting its application was proposed to be the main developing directions of biomass 3D printing in the future. It is believed that the combination of abundant biomass feedstocks and advanced 3D printing technology will provide a green, low-carbon and efficient way for the sustainable development of materials manufacturing industry.