Evolution of 3D Printing Methods and Materials for Electrochemical Energy Storage

Recent Advances in 3D Printing Technologies for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have heretofore raised burgeoning interest due to their cost effectiveness and high theoretical energy densities. However, the inherent porous and fluffy structure of sulfur impedes the path to constructing high-loading electrodes (over 5 mg cm-2) for their practicability. Furthermore, especially in thick electrodes, challenges like the retarded redox kinetics, notorious polysulfide shuttling, and wanton electrode expansion seriously give rise to low sulfur utilization, poor rate performance, and unsatisfactory cycling stability. Constructing free-standing architectures has been demonstrated as an effective strategy to tackle the aforementioned issues for high-loading Li-S batteries. As an emerging technique, 3D printing (3DP) shows merits in rapidly fabricating precise microstructures with controllable loadings and rationally organized porosity. For the Li-S realm, 3DP offers optimized Li+/e- transmission path with well-dispersed electrocatalysts, which achieves efficient polysulfide regulation and guarantees favorable performance. This review covers the design principle and preparation of printable inks, and their practical applications to manufacture self-supported frameworks (such as cathodes, anodes, and separators) for Li-S batteries. Challenges and perspectives on the potential future development of 3DP Li-S batteries are also outlined.

Effect of Solvent Presoaking of FDM-Printed Conductive PLA Current Collectors in 3D-Printed Carbon Supercapacitors

The electrochemical response of symmetric carbon-based supercapacitor devices made using two 3D-printing techniques, Vat-P (vat polymerization) and FDM (fused deposition modeling), shows how the printing method dominates the overall cell response. Despite possessing excellent cycle life, the conductive poly(lactic acid) (PLA) FDM printed current collectors suffer from relatively high resistance and suppressed capacitance linked to current collector material resistivity. Here, we examine in situ methods to influence the interfacial conductivity of the FDM current collectors by surface modification. Both dimethylformamide (DMF) and aqueous potassium hydroxide (KOH) treatments are investigated to compare solvent decomposition and electrolyte presoaking for this purpose. Using a single-walled carbon nanotube and graphene nanoplatelet carbon composite slurry on FDM current collectors in Vat-P 3D-printed cell casings, the supercapacitor cells show that the DMF treatment method has worse capacitance but better retention over 1 million cycles compared to the untreated FDM current collector cells. Pretreatment in a solution of 6 M aqueous KOH, identical to the cell electrolyte, markedly improves the effective current collector conductivity and interface with the active material, with a five-fold improvement in capacitance at the expense of less cycling stability. This is possible because the KOH treatment provides a 10-fold reduction in the FDM current collector resistance, which correlates with the improved cyclic voltammetric response. Galvanostatic charge-discharge tests reveal a deteriorated long-term cycling stability and rate capability despite better interfacial conductivity with the active material. In-situ presoaking that allows a degree of depolymerization at the surface relieves the conductive additive within the PLA to improve electrochemical interfacial activity and identifies the trade-off between improved capacitance and long-term cycling stability for common electrolytes in PLA-based 3D printed aqueous supercapacitors.

Transdisciplinary Innovations in Athlete Health: 3D-Printable Wearable Sensors for Health Monitoring and Sports Psychology

The integration of 3D printing technology into wearable sensor systems has catalyzed a paradigm shift in sports psychology and athlete health monitoring by enabling real-time, personalized data collection on physiological and psychological states. In this study, not only is the technical potential of these advancements examined but their real-world applications in sports psychology are also critically assessed. While the existing research primarily focuses on sensor fabrication and data acquisition, a significant gap remains in the evaluation of their direct impact on decision-making processes in coaching, mental resilience, and long-term psychological adaptation in athletes. A critical analysis of the current state of 3D-printed wearable sensors is conducted, highlighting both their advantages and limitations. By combining theoretical insights with practical considerations, a comprehensive framework is established for understanding how sensor-based interventions can be effectively incorporated into sports training and psychological evaluation. Future research should prioritize longitudinal studies, athlete-centered validation, and interdisciplinary collaborations to bridge the gap between technological developments and real-world applications. Additionally, the integration of artificial intelligence and advanced biomaterials has significant potential to enhance the reliability and interpretability of sensor-driven interventions. However, without rigorous scientific validation, their effectiveness remains uncertain. This study highlights the importance of a systematic approach in implementing and evaluating 3D-printed wearable sensors in sports psychology.

Multi-Physical Lattice Metamaterials Enabled by Additive Manufacturing: Design Principles, Interaction Mechanisms, and Multifunctional Applications

Lattice metamaterials emerge as advanced architected materials with superior physical properties and significant potential for lightweight applications. Recent developments in additive manufacturing (AM) techniques facilitate the manufacturing of lattice metamaterials with intricate microarchitectures and promote their applications in multi-physical scenarios. Previous reviews on lattice metamaterials have largely focused on a specific/single physical field, with limited discussion on their multi-physical properties, interaction mechanisms, and multifunctional applications. Accordingly, this article critically reviews the design principles, structure-mechanism-property relationships, interaction mechanisms, and multifunctional applications of multi-physical lattice metamaterials enabled by AM techniques. First, lattice metamaterials are categorized into homogeneous lattices, inhomogeneous lattices, and other forms, whose design principles and AM processes are critically discussed, including the benefits and drawbacks of different AM techniques for fabricating different types of lattices. Subsequently, the structure-mechanism-property relationships and interaction mechanisms of lattice metamaterials in a range of physical fields, including mechanical, acoustic, electromagnetic/optical, and thermal disciplines, are summarized to reveal critical design principles. Moreover, the multifunctional applications of lattice metamaterials, such as sound absorbers, insulators, and manipulators, sensors, actuators, and soft robots, thermal management, invisible cloaks, and biomedical implants, are enumerated. These design principles and structure-mechanism-property relationships provide effective design guidelines for lattice metamaterials in multifunctional applications.

MXene Triggered Free Radical Polymerization in Minutes Toward All-Printed Zn-Ion Hybrid Capacitors and Beyond

Additive manufacturing of (quasi-) solid-state (QSS) electrochemical energy storage devices (EES) highlights the significance of gel polymer electrolytes (GPEs) design. Creating well-bonded electrode-GPEs interfaces in the electrode percolative network via printing leads to large-scale production of customized EES with boosted electrochemical performance but has proven to be quite challenging. Herein, we report on a versatile, universal and scalable approach to engineer a controllable, seamless electrode-GPEs interface via free radical polymerization (FRP) triggered by MXene at room temperature. Importantly, MXene reduces the dissociation enthalpy of persulfate initiators and significantly shortens the induction period accelerated by SO4 -, enabling the completion of FRP within minutes. The as-formed well-bonded electrode-GPEs interface homogenizes the electrical and concentration fields (i.e., Zn2+), therefore suppressing the dendrites formation, which translates to long-term cycling (50,000 times), high energy density (105.5 Wh kg-1) and power density (9231 W kg-1) coupled with excellent stability upon deformation in the zinc-ion hybrid capacitors (ZHCs). Moreover, the critical switch of the rheological behaviours of the polymer electrolyte (as aqueous inks in still state and become solids once triggered by MXene) perfectly ensures the direct all-printing of electrodes and GPEs with well-bonded interface in between, opening vast possibilities for all-printed QSS EES beyond ZHCs.

Effects of thermomechanical parameters on surface texture in filament materials extrusion: outlook and trends

The material extrusion process has been widely used to manufacture custom products. However, the surface texture varies due to the additive mechanism of the process, which depends on the layer height and surface orientation, resulting in varying average surface roughness values for inclined, flat and vertical surfaces. Different strand welding conditions result in non-uniform internal stresses, surface distortions, layer traces, weak bonding, non-uniform pores and material overflow. This paper comprehensively examines material extrusion process achievements in surface texture quality and studies and summarises the most influential processing parameters. Parameter effects are critically discussed for each topic; flat, inclined, and vertical surfaces. The results of this research help reduce post-processing.

Enhancing Supercapacitor Electrochemical Performance with 3D Printed Cellular PEEK/MWCNT Electrodes Coated with PEDOT: PSS

In this study, we examine the electrochemical performance of supercapacitor (SC) electrodes made from 3D-printed nanocomposites. These composites consist of multiwalled carbon nanotubes (MWCNTs) and polyether ether ketone (PEEK), coated with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The electrochemical performance of a 3D-printed PEEK/MWCNT solid electrode with a surface area density of 1.2 mm-1 is compared to two distinct periodically porous PEEK/MWCNT electrodes with surface area densities of 7.3 and 7.1 mm-1. To enhance SC performance, the 3D-printed electrodes are coated with a conductive polymer, PEDOT:PSS. The architected cellular electrodes exhibit significantly improved capacitive properties, with the cellular electrode (7.1 mm-1) displaying a capacitance nearly four times greater than that of the solid 3D-printed electrode-based SCs. Moreover, the PEDOT:PSS-coated cellular electrode (7.1 mm-1) demonstrates a high specific capacitance of 12.55 mF·cm-3 at 50 mV·s-1, contrasting to SCs based on 3D-printed cellular electrodes (4.09 mF·cm-3 at 50 mV·s-1) without the coating. The conductive PEDOT:PSS coating proves effective in reducing surface resistance, resulting in a decreased voltage drop during the SCs' charging and discharging processes. Ultimately, the 3D-printed cellular nanocomposite electrode with the conductive polymer coating achieves an energy density of 1.98 μW h·cm-3 at a current of 70 μA. This study underscores how the combined effect of the surface area density of porous electrodes enabled by 3D printing, along with the conductivity imparted by the polymer coating, synergistically improves the energy storage performance.

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.

3D Printing Manufacturing of Lithium Batteries: Prospects and Challenges toward Practical Applications

The manufacturing and assembly of components within cells have a direct impact on the sample performance. Conventional processes restrict the shapes, dimensions, and structures of the commercially available batteries. 3D printing, a novel manufacturing process for precision and practicality, is expected to revolutionize the lithium battery industry owing to its advantages of customization, mechanization, and intelligence. This technique can be used to effectively construct intricate 3D structures that enhance the designability, integrity, and electrochemical performance of both liquid- and solid-state lithium batteries. In this study, an overview of the development of 3D printing technologies is provided and their suitability for comparison with conventional printing processes is assessed. Various 3D printing technologies applicable to lithium-ion batteries have been systematically introduced, especially more practical composite printing technologies. The practicality, limitations, and optimization of 3D printing are discussed dialectically for various battery modules, including electrodes, electrolytes, and functional architectures. In addition, all-printed batteries are emphatically introduced. Finally, the prospects and challenges of 3D printing in the battery industry are evaluated.

Recent advances in 3D printing properties of natural food gels: Application of innovative food additives

Recent advances in 3D printing technology have provided a new avenue for food manufacturing. However, one challenge in 3D printing food is the limited availability of printable materials that can mimic the properties of real food. This review focused on the various 3DFP methodologies, as well as the reinforcement of natural food gel for improving printing features in 3D printed food. Also covered is the use of hydrogel-based 3D printing in the development of 3D printed food. Different 3D printing techniques can be employed to print hydrogel-based inks, each with its advantages and limitations. 3D printing of food using hydrogel-based inks has potential for customized food products development. In summary, the utilization of hydrogel-based inks in 3D printing offers a promising avenue for the development of customized food products. Although there are still challenges to overcome, such as improving the printability and mechanical properties of hydrogel-based inks, the potential benefits of this technology make it an exciting area of research.

Rheology in Product Development: An Insight into 3D Printing of Hydrogels and Aerogels

Rheological characterisation plays a crucial role in developing and optimising advanced materials in the form of hydrogels and aerogels, especially if 3D printing technologies are involved. Applications ranging from tissue engineering to environmental remediation require the fine-tuning of such properties. Nonetheless, their complex rheological behaviour presents unique challenges in additive manufacturing. This review outlines the vital rheological parameters that influence the printability of hydrogel and aerogel inks, emphasising the importance of viscosity, yield stress, and viscoelasticity. Furthermore, the article discusses the latest developments in rheological modifiers and printing techniques that enable precise control over material deposition and resolution in 3D printing. By understanding and manipulating the rheological properties of these materials, researchers can explore new possibilities for applications such as biomedicine or nanotechnology. An optimal 3D printing ink requires strong shear-thinning behaviour for smooth extrusion, forming continuous filaments. Favourable thixotropic properties aid viscosity recovery post-printing, and adequate yield stress and G' are crucial for structural integrity, preventing deformation or collapse in printed objects, and ensuring high-fidelity preservation of shapes. This insight into rheology provides tools for the future of material design and manufacturing in the rapidly evolving field of 3D printing of hydrogels and aerogels.

Direct-Ink-Writing 3D-Printed Bioelectronics

The development of wearable and implantable bioelectronics has garnered significant momentum in recent years, driven by the ever-increasing demand for personalized health monitoring, remote patient management, and real-time physiological data collection. The elevated sophistication and advancement of these devices have thus led to the use of many new and unconventional materials which cannot be fulfilled through traditional manufacturing techniques. Three-dimension (3D) printing, also known as additive manufacturing, is an emerging technology that opens new opportunities to fabricate next-generation bioelectronic devices. Some significant advantages include its capacity for material versatility and design freedom, rapid prototyping, and manufacturing efficiency with enhanced capabilities. This review provides an overview of the recent advances in 3D printing of bioelectronics, particularly direct ink writing (DIW), encompassing the methodologies, materials, and applications that have emerged in this rapidly evolving field. This review showcases the broad range of bioelectronic devices fabricated through 3D printing including wearable biophysical sensors, biochemical sensors, electrophysiological sensors, energy devices, multimodal systems, implantable devices, and soft robots. This review will also discuss the advantages, existing challenges, and outlook of applying DIW 3D printing for the development of bioelectronic devices toward healthcare applications.

A Mucin-Based Bio-Ink for 3D Printing of Objects with Anti-Biofouling Properties

With its potential to revolutionize the field of personalized medicine by producing customized medical devices and constructs for tissue engineering at low costs, 3D printing has emerged as a highly promising technology. Recent advancements have sparked increasing interest in the printing of biopolymeric hydrogels. However, owing to the limited printability of those soft materials, the lack of variability in available bio-inks remains a major challenge. In this study, a novel bio-ink is developed based on functionalized mucin-a glycoprotein that exhibits a multitude of biomedically interesting properties such as immunomodulating activity and strong anti-biofouling behavior. To achieve sufficient printability of the mucin-based ink, its rheological properties are tuned by incorporating Laponite XLG as a stabilizing agent. It is shown that cured objects generated from this novel bio-ink exhibit mechanical properties partially similar to that of soft tissue, show strong anti-biofouling properties, good biocompatibility, tunable cell adhesion, and immunomodulating behavior. The presented findings suggest that this 3D printable bio-ink has a great potential for a wide range of biomedical applications, including tissue engineering, wound healing, and soft robotics.

3D Printing-Enabled Design and Manufacturing Strategies for Batteries: A Review

Lithium-ion batteries (LIBs) have significantly impacted the daily lives, finding broad applications in various industries such as consumer electronics, electric vehicles, medical devices, aerospace, and power tools. However, they still face issues (i.e., safety due to dendrite propagation, manufacturing cost, random porosities, and basic & planar geometries) that hinder their widespread applications as the demand for LIBs rapidly increases in all sectors due to their high energy and power density values compared to other batteries. Additive manufacturing (AM) is a promising technique for creating precise and programmable structures in energy storage devices. This review first summarizes light, filament, powder, and jetting-based 3D printing methods with the status on current trends and limitations for each AM technology. The paper also delves into 3D printing-enabled electrodes (both anodes and cathodes) and solid-state electrolytes for LIBs, emphasizing the current state-of-the-art materials, manufacturing methods, and properties/performance. Additionally, the current challenges in the AM for electrochemical energy storage (EES) applications, including limited materials, low processing precision, codesign/comanufacturing concepts for complete battery printing, machine learning (ML)/artificial intelligence (AI) for processing optimization and data analysis, environmental risks, and the potential of 4D printing in advanced battery applications, are also presented.

Recent Progress and Trends in the Development of Electrospun and 3D Printed Polymeric-Based Materials to Overcome Antimicrobial Resistance (AMR)

Antimicrobial resistance (AMR) developed by microorganisms is considered one of the most critical public health issues worldwide. This problem is affecting the lives of millions of people and needs to be addressed promptly. Mainly, antibiotics are the substances that contribute to AMR in various strains of bacteria and other microorganisms, leading to infectious diseases that cannot be effectively treated. To avoid the use of antibiotics and similar drugs, several approaches have gained attention in the fields of materials science and engineering as well as pharmaceutics over the past five years. Our focus lies on the design and manufacture of polymeric-based materials capable of incorporating antimicrobial agents excluding the aforementioned substances. In this sense, two of the emerging techniques for materials fabrication, namely, electrospinning and 3D printing, have gained significant attraction. In this article, we provide a summary of the most important findings that contribute to the development of antimicrobial systems using these technologies to incorporate various types of nanomaterials, organic molecules, or natural compounds with the required property. Furthermore, we discuss and consider the challenges that lie ahead in this research field for the coming years.

3D Printed Supercapacitor Exploiting PEDOT-Based Resin and Polymer Gel Electrolyte

Renewable energy-based technologies and increasing IoT (Internet of Things) objects population necessarily require proper energy storage devices to exist. In the view of customized and portable devices, Additive Manufacturing (AM) techniques offer the possibility to fabricate 2D to 3D features for functional applications. Among the different AM techniques extensively explored to produce energy storage devices, direct ink writing is one of the most investigated, despite the poor achievable resolution. Herein, we present the development and characterization of an innovative resin which can be employed in a micrometric precision stereolithography (SL) 3D printing process for the fabrication of a supercapacitor (SC). Poly(3,4-ethylenedioxythiophene) (PEDOT), a conductive polymer, was mixed with poly(ethylene glycol) diacrylate (PEGDA), to get a printable and UV curable conductive composite material. The 3D printed electrodes were electrically and electrochemically investigated in an interdigitated device architecture. The electrical conductivity of the resin falls within the range of conductive polymers with 200 mS/cm and the 0.68 µWh/cm² printed device energy density falls within the literature range.

Science and Technology of Additive Manufacturing Progress: Processes, Materials, and Applications

As a special review article, several significant and applied results in 3D printing and additive manufacturing (AM) science and technology are reviewed and studied. Which, the reviewed research works were published in 2020. Then, we would have another review article for 2021 and 2022. The main purpose is to collect new and applied research results as a useful package for researchers. Nowadays, AM is an extremely discussed topic and subject in scientific and industrial societies, as well as a new vision of the unknown modern world. Also, the future of AM materials is toward fundamental changes. Which, AM would be an ongoing new industrial revolution in the digital world. With parallel methods and similar technologies, considerable developments have been made in 4D in recent years. AM as a tool is related to the 4th industrial revolution. So, AM and 3D printing are moving towards the fifth industrial revolution. In addition, a study on AM is vital for generating the next developments, which are beneficial for human beings and life. Thus, this article presents the brief, updated, and applied methods and results published in 2020.

Graphical Abstract

Low-Temperature Resistant Stretchable Micro-Supercapacitor Based on 3D Printed Octet-Truss Design

Recently, stretchable micro-supercapacitors (MSCs) that can be easily integrated into electronic devices have attracted research and industrial attentions. In this work, three-dimensional (3D) stretchable MSCs with an octet-truss electrode (OTE) design have been demonstrated by a rapid digital light processing (DLP) process. The 3D-printed electrode structure is beneficial for electrode-electrolyte interface formation and consequently increases the number of ions adsorbed on the electrode surface. The designed MSCs can achieve a high capacitance as ≈74.76 mF cm^-3 under 1 mA cm^-3 at room temperature even under a high mechanical deformation, and can achieve 19.53 mF cm^-3 under 0.1 mA cm^-3 at a low temperature (-30 °C). Moreover, finite element analysis (FEA) reveals the OTE structure provides 8 times more contact area per unit volume at the electrode-electrolyte interface compared to the traditional interdigital electrode (IDE). This work combines structural design and 3D printing techniques, which provides new insights into highly stretchable MSCs for next-generation electronic devices.

Antibacterial smart hydrogels: New hope for infectious wound management

Millions of people die annually due to uncured wound infections. Healthcare systems incur high costs to treat wound infections. Tt is predicted to become more challenging due to the rise of multidrug-resistant conditions. During the last decades, smart antibacterial hydrogels could attract attention as a promising solution, especially for skin wound infections. These antibacterial hydrogels are termed 'smart' due to their response to specific physical and chemical environmental stimuli. To deliver different drugs to particular sites in a controlled manner, various types of crosslinking strategies are used in the manufacturing process. Smart hydrogels are designed to provide antimicrobial agents to the infected sites or are built from polymers with inherent disinfectant properties. This paper aims to critically review recent pre-clinical and clinical advances in using smart hydrogels against skin wound infections and propose the next best thing for future trends. For this purpose, an introduction to skin wound healing and disease is presented and intelligent hydrogels responding to different stimuli are introduced. Finally, the most promising investigations are discussed in their related sections. These studies can pave the way for producing new biomaterials with clinical applications.

Digital manufacturing for accelerating organ-on-a-chip dissemination and electrochemical biosensing integration

Organ on-a-chip (OoC) is a promising technology that aims to recapitulate human body pathophysiology in a more precise way to advance in drug development and complex disease understanding. However, the presence of OoC in biological laboratories is still limited and mainly restricted to laboratories with access to cleanroom facilities. Besides, the current analytical methods employed to extract information from the organ models are endpoint and post facto assays which makes it difficult to ensure that during the biological experiment the cell microenvironment, cellular functionality and behaviour are controlled. Hence, the integration of real-time biosensors is highly needed and requested by the OoC end-user community to provide insight into organ function and responses to stimuli. In this context, electrochemical sensors stand out due to their advantageous features like miniaturization capabilities, ease of use, automatization and high sensitivity and selectivity. Electrochemical sensors have been already successfully miniaturized and employed in other fields such as wearables and point-of-care devices. We have identified that the explanation for this issue may be, to a large extent, the accessibility to microfabrication technologies. These fields employ preferably digital manufacturing (DM), which is a more accessible microfabrication approach regardless of funding and facilities. Therefore, we envision that a paradigm shift in microfabrication that adopts DM instead of the dominating soft lithography for the in-lab microfabrication of OoC devices will contribute to the dissemination of the field and integration of the promising real-time sensing.

A Bioinspired Hierarchical Fast Transport Network Boosting Electrochemical Performance of 3D Printed Electrodes

Current 3D printed electrodes suffer from insufficient multiscale transport speed, which limits the improvement of electrochemical performance of 3D printed electrodes. Herein, a bioinspired hierarchical fast transport network (HFTN) in a 3D printed reduced graphene oxide/carbon nanotube (3DP GC) electrode demonstrating superior electrochemical performance is constructed. Theoretical calculations reveal that the HFTN of the 3DP GC electrode increases the ion transport rate by more than 50 times and 36 times compared with those of the bulk GC electrode and traditional 3DP GC (T-3DP GC) electrode, respectively. Compared with carbon paper, carbon cloth, bulk GC electrode, and T-3DP GC electrode, the HFTN in 3DP GC electrode endows obvious advantages: i) efficient utilization of surface area for uniform catalysts dispersion during electrochemical deposition; ii) efficient utilization of catalysts enables the high mass activity of catalysts and low overpotential of electrode in electrocatalytic reaction. The cell of 3DP GC/Ni-NiO||3DP GC/NiS₂ demonstrates a low voltage of only 1.42 V to reach 10 mA cm^-2 and good stability up to 20 h for water splitting in alkaline conditions, which is superior to commercialized Pt/C||RuO₂ . This work demonstrates great potential in developing high-performance 3D printed electrodes for electrochemical energy conversion and storage.

In-Situ Assembly of MoS2 Nanostructures on EHD-Printed Microscale PVDF Fibrous Films for Potential Energy Storage Applications

Three-dimensional (3D) printing has been widely utilized to fabricate free-standing electrodes in energy-related fields. In terms of fabrication, the two most challenging limitations of 3D printed electrodes are the poor printing resolution and simple structural dimension. Here we proposed a novel process to fabricate molybdenum disulfide-polyvinylidene fluoride (MoS₂-PVDF) hierarchical electrodes for energy storage applications. The 20-layer microscale PVDF films with a stable fiber width of 8.3 ± 1.2 μm were fabricated by using electrohydrodynamic (EHD) printing. MoS₂ nanostructures were synthesized and assembled on the microscale PVDF fibers by using hydrothermal crystal growth. The structural and material investigations were conducted to demonstrate the geometrical morphology and materials component of the composite structure. The electrochemical measurements indicated that the MoS₂-PVDF electrodes exhibited the typical charge-discharge performance with a mass specific capacitance of 60.2 ± 4.5 F/g. The proposed method offers a facile and scalable approach for the fabrication of high-resolution electrodes, which might be further developed with enhanced specific capacitance in energy storage fields.

Recent Advances on High-Performance Polyaryletherketone Materials for Additive Manufacturing

Polyaryletherketone (PAEK) is emerging as an important high-performance polymer material in additive manufacturing (AM) benefiting from its excellent mechanical properties, good biocompatibility, and high-temperature stability. The distinct advantages of AM facilitate the rapid development of PAEK products with complex customized structures and functionalities, thereby enhancing their applications in various fields. Herein, the recent advances on AM of high-performance PAEKs are comprehensively reviewed, concerning the materials properties, AM processes, mechanical properties, and potential applications of additively manufactured PAEKs. To begin, an introduction to fundamentals of AM and PAEKs, as well as the advantages of AM of PAEKs is provided. Discussions are then presented on the material properties, AM processes, processing-matter coupling mechanism, thermal conductivity, crystallization characteristics, and microstructures of AM-processed PAEKs. Thereafter, the mechanical properties and anisotropy of additively manufactured PAEKs are discussed in depth. Their representative applications in biomedical, aerospace, electronics, and other fields are systematically presented. Finally, current challenges and possible solutions are discussed for the future development of high-performance AM polymers.

An Overview of Various Additive Manufacturing Technologies and Materials for Electrochemical Energy Conversion Applications

Additive manufacturing (AM) technologies have many advantages, such as design flexibility, minimal waste, manufacturing of very complex structures, cheaper production, and rapid prototyping. This technology is widely used in many fields, including health, energy, art, design, aircraft, and automotive sectors. In the manufacturing process of 3D printed products, it is possible to produce different objects with distinctive filament and powder materials using various production technologies. AM covers several 3D printing techniques such as fused deposition modeling (FDM), inkjet printing, selective laser melting (SLM), and stereolithography (SLA). The present review provides an extensive overview of the recent progress in 3D printing methods for electrochemical fields. A detailed review of polymeric and metallic 3D printing materials and their corresponding printing methods for electrodes is also presented. Finally, this paper comprehensively discusses the main benefits and the drawbacks of electrode production from AM methods for energy conversion systems.

Additive manufacturing of LiNi1/3Mn1/3Co1/3O2 battery electrode material via vat photopolymerization precursor approach

Additive manufacturing, also called 3D printing, has the potential to enable the development of flexible, wearable and customizable batteries of any shape, maximizing energy storage while also reducing dead-weight and volume. In this work, for the first time, three-dimensional complex electrode structures of high-energy density LiNi1/3Mn1/3Co1/3O2 (NMC 111) material are developed by means of a vat photopolymerization (VPP) process combined with an innovative precursor approach. This innovative approach involves the solubilization of metal precursor salts into a UV-photopolymerizable resin, so that detrimental light scattering and increased viscosity are minimized, followed by the in-situ synthesis of NMC 111 during thermal post-processing of the printed item. The absence of solid particles within the initial resin allows the production of smaller printed features that are crucial for 3D battery design. The formulation of the UV-photopolymerizable composite resin and 3D printing of complex structures, followed by an optimization of the thermal post-processing yielding NMC 111 is thoroughly described in this study. Based on these results, this work addresses one of the key aspects for 3D printed batteries via a precursor approach: the need for a compromise between electrochemical and mechanical performance in order to obtain fully functional 3D printed electrodes. In addition, it discusses the gaps that limit the multi-material 3D printing of batteries via the VPP process.

Water activated disposable paper battery

We developed a disposable paper battery aiming to reduce the environmental impact of single-use electronics for applications such as point of care diagnosis, smart packaging and environmental sensing. The battery uses Zinc as a biodegradable metal anode, graphite as a nontoxic cathode material and paper as a biodegradable substrate. To facilitate additive manufacturing, we developed electrodes and current collector inks that can be stencil printed on paper to create water-activated batteries of arbitrary shape and size. The battery remains inactive until water is provided and absorbed by the paper substrate, taking advantage of its natural wicking behavior. Once activated, a single cell provides an open circuit potential of 1.2 V and a peak power density of 150 µW/cm² at 0.5 mA. As a proof of concept, we fabricated a two cell battery and used it to power an alarm clock and its liquid crystal display.

3D printed interdigitated supercapacitor using reduced graphene oxide-MnO x /Mn3O4 based electrodes

In this study hybrid nanocomposites (HNCs) based on manganese oxides (MnO_x/Mn₃O₄) and reduced graphene oxide (rGO) are synthesized as active electrodes for energy storage devices. Comprehensive structural characterizations demonstrate that the active material is composed of MnO_x/Mn₃O₄ nanorods and nanoparticles embedded in rGO nanosheets. The development of such novel structures is facilitated by the extreme synthesis conditions (high temperatures and pressures) of the liquid-confined plasma plume present in the Laser Ablation Synthesis in Solution (LASiS) technique. Specifically, functional characterizations demonstrate that the performance of the active layer is highly correlated with the MnO_x/Mn₃O₄ to rGO ratio and the morphology of MnO_x/Mn₃O₄ nanostructures in HNCs. To that end, active layer inks comprising HNC samples prepared under optimal laser ablation time windows, when interfaced with a percolated conductive network of electronic grade graphene and carbon nanofibers (CNFs) mixture, indicate superior supercapacitance for functional electrodes fabricated via sequential inkjet printing of the substrate, current collector layer, active material layer, and gel polymer electrolyte layer. Electrochemical characterizations unequivocally reveal that the electrode with the LASiS synthesized MnO_x/Mn₃O₄–rGO composite exhibits significantly higher specific capacitance compared to the ones produced with commercially available Mn₃O₄–graphene NCs. Moreover, the galvanostatic charge–discharge (GCD) experiments with the LASiS synthesized HNCs show a significantly larger charge storage capacity (325 F g⁻¹) in comparison to NCs synthesized with commercially available Mn₃O₄–graphene (189 F g⁻¹). Overall, this study has paved the way for use of LASiS-based synthesized functional material in combination with additive manufacturing techniques for all-printed electronics with superior performance.

LASiS-based HNCs of nanostructured MnO_x/Mn₃O₄.

SLM-processed MoS2/Mo2S3 nanocomposite for energy conversion/storage applications

MoS₂-based nanocomposites have been widely processed by a variety of conventional and 3D printing techniques. In this study, selective laser melting (SLM) has for the first time successfully been employed to tune the crystallographic structure of bulk MoS₂ to a 2H/1T phase and to distribute Mo₂S₃ nanoparticles in-situ in MoS₂/Mo₂S₃ nanocomposites used in electrochemical energy conversion/storage systems (EECSS). The remarkable results promote further research on and elucidate the applicability of laser-based powder bed processing of 2D nanomaterials for a wide range of functional structures within, e.g., EECSS, aerospace, and possibly high-temperature solid-state EECSS even in space.

Bioinspired Materials for Energy Storage

Nature offers a variety of interesting structures and intriguing functions for researchers to be learnt for advanced materials innovations. Recently, bioinspired materials have received intensive attention in energy storage applications. Inspired by various natural species, many new configurations and components of energy storage devices, such as rechargeable batteries and supercapacitors, have been designed and innovated. The bioinspired designs on energy devices, such as electrodes and electrolytes, have brought about excellent physical, chemical, and mechanical properties compared to the counterparts at their conventional forms. In this review, the design principles for bioinspired materials ranging from structures, synthesis, and functionalization to multi-scale ordering and device integration are first discussed, and then a brief summary is given on the recent progress on bioinspired materials for energy storage systems, particularly the widely studied rechargeable batteries and supercapacitors. Finally, a critical review on the current challenges and brief perspective on the future research focuses are proposed. It is expected that this review can offer some insights into the smart energy storage system design by learning from nature.

Polymer Encapsulation Strategy toward 3D Printable, Sustainable, and Reliable Form-Stable Phase Change Materials for Advanced Thermal Energy Storage

Form-stable phase change materials (PCMs) have garnered tremendous attention in thermal energy storage (TES) owing to their remarkable latent heat. However, the integration of intelligent manufacturing, recycling, and optimized multifunction is considered not feasible for form-stable PCMs due to the restriction of encapsulation technology. Here, an excellent polymer encapsulation strategy is proposed to prepare 3D printable, sustainable, and reliable form-stable PCMs (Si_PCM-x), which are universal for petroleum-based and biobased long alkyl compounds. Si_PCM-x have top-class latent heat, and the phase-change temperatures are tunable from body temperature to high temperature. The in situ formative bottlebrush phase-change polysiloxane networks are used as supporting materials, and the encapsulation mechanism is clarified. Si_rbw-250 can be degraded and re-encapsulated to achieve recycling. Besides, Si_rbw-250 is fabricated as the customer-designed objects with shape-changing behavior via 3D printing. By introducing the metal foams and nano-coatings, the resulting phase-change composites simultaneously exhibit excellent superhydrophobicity, mechanical properties, thermal conductivity, electromagnetic interference shielding behavior, and solar-, electric-, and magnetic-to-thermal energy conversion ability. Besides, S-Ni-Si_PCM-250 can be applied in the wearable functional devices and movable solar-thermal charging. This strategy will lead to huge renovation in the TES field and provide an efficient guideline for designing advanced form-stable PCMs.

3D Printing for Solid-State Energy Storage

Ever-growing demand to develop satisfactory electrochemical devices has driven cutting-edge research in designing and manufacturing reliable solid-state electrochemical energy storage devices (EESDs). 3D printing, a precise and programmable layer-by-layer manufacturing technology, has drawn substantial attention to build advanced solid-state EESDs and unveil intrinsic charge storage mechanisms. It provides brand-new opportunities as well as some challenges in the field of solid-state energy storage. This review focuses on the topic of 3D printing for solid-state energy storage, which bridges the gap between advanced manufacturing and future EESDs. It starts from a brief introduction followed by an emphasis on 3D printing principles, where basic features of 3D printing and key issues for solid-state energy storage are both reviewed. Recent advances in 3D printed solid-state EESDs including solid-state batteries and solid-state supercapacitors are then summarized. Conclusions and perspectives are also provided regarding the further development of 3D printed solid-state EESDs. It can be expected that advanced 3D printing will significantly promote future evolution of solid-state EESDs.

Bringing Electrochemical Three-Dimensional Printing to the Nanoscale

Nanoscale 3D printing is attracting attention as an alternative manufacturing technique for a variety of applications from electronics and nanooptics to sensing, nanorobotics, and energy storage. The constantly shrinking critical dimension in state-of-the-art technologies requires fabrication of complex conductive structures with nanometer resolution. Electrochemical techniques are capable of producing impurity-free metallic conductors with superb electrical and mechanical properties, however, true nanoscale resolution (<100 nm) remained unattainable. Here, we set new a benchmark in electrochemical 3D printing. By employing nozzles with dimensions as small as 1 nm, we demonstrate layer-by-layer manufacturing of 25 nm diameter voxels. Full control of the printing process allows adjustment of the feature size on-the-fly, printing tilted, and overhanging structures. On the basis of experimental evidence, we estimate the limits of electrochemical 3D printing and discuss the origins of this new resolution frontier.

Recent Advances on 2D Materials towards 3D Printing

In recent years, 2D materials have been implemented in several applications due to their unique and unprecedented properties. Several examples can be named, from the very first, graphene, to transition-metal dichalcogenides (TMDs, e.g., MoS2), two-dimensional inorganic compounds (MXenes), hexagonal boron nitride (h-BN), or black phosphorus (BP). On the other hand, the accessible and low-cost 3D printers and design software converted the 3D printing methods into affordable fabrication tools worldwide. The implementation of this technique for the preparation of new composites based on 2D materials provides an excellent platform for next-generation technologies. This review focuses on the recent advances of 3D printing of the 2D materials family and its applications; the newly created printed materials demonstrated significant advances in sensors, biomedical, and electrical applications.

State-of-the-art of 3D printing technology of alginate-based hydrogels-An emerging technique for industrial applications

Recently, three-dimensional (3D) printing (also known as additive manufacturing) has received unprecedented consideration in various fields owing to many advantages compared to conventional manufacturing equipment such as reduced fabrication time, one-step production, and the ability for rapid prototyping. This promising technology, as the next manufacturing revolution and universal industrial method, allows the user to fabricate desired 3D objects using a layer-by-layer deposition of material and a 3D printer. Alginate, a versatile polysaccharide derived from seaweed, is popularly used for this advanced bio-fabrication technique due to its printability, biodegradability, biocompatibility, excellent availability, low degree of toxicity, being a relatively inexpensive, rapid gelation in the presence of Ca²⁺ divalent, and having fascinating chemical structure. In recent years, 3D printed alginate-based hydrogels have been prepared and used in various fields including tissue engineering, water treatment, food, electronics, and so forth. Due to the prominent role of 3D printed alginate-based materials in diverse fields. So, this review will focus and highlight the latest and most up-to-date achievements in the field of 3D printed alginate-based materials in biomedical, food, water treatment, and electronics.

Efficient 3D printing via photooxidation of ketocoumarin based photopolymerization

Photopolymerization-based three-dimensional (3D) printing can enable customized manufacturing that is difficult to achieve through other traditional means. Nevertheless, it remains challenging to achieve efficient 3D printing due to the compromise between print speed and resolution. Herein, we report an efficient 3D printing approach based on the photooxidation of ketocoumarin that functions as the photosensitizer during photopolymerization, which can simultaneously deliver high print speed (5.1 cm h-1) and high print resolution (23 μm) on a common 3D printer. Mechanistically, the initiating radical and deethylated ketocoumarin are both generated upon visible light exposure, with the former giving rise to rapid photopolymerization and high print speed while the latter ensuring high print resolution by confining the light penetration. By comparison, the printed feature is hard to identify when the ketocoumarin encounters photoreduction due to the increased lateral photopolymerization. The proposed approach here provides a viable solution towards efficient additive manufacturing by controlling the photoreaction of photosensitizers during photopolymerization.

Effects of 3D Printing-Line Directions for Stretchable Sensor Performances

Health monitoring sensors that are attached to clothing are a new trend of the times, especially stretchable sensors for human motion measurements or biological markers. However, price, durability, and performance always are major problems to be addressed and three-dimensional (3D) printing combined with conductive flexible materials (thermoplastic polyurethane) can be an optimal solution. Herein, we evaluate the effects of 3D printing-line directions (45°, 90°, 180°) on the sensor performances. Using fused filament fabrication (FDM) technology, the sensors are created with different print styles for specific purposes. We also discuss some main issues of the stretch sensors from Carbon Nanotube/Thermoplastic Polyurethane (CNT/TPU) and FDM. Our sensor achieves outstanding stability (10,000 cycles) and reliability, which are verified through repeated measurements. Its capability is demonstrated in a real application when detecting finger motion by a sensor-integrated into gloves. This paper is expected to bring contribution to the development of flexible conductive materials-based on 3D printing.

Local electrochemical activity of transition metal dichalcogenides and their heterojunctions on 3D-printed nanocarbon surfaces

Transition metal dichalcogenides (TMDs) have shown to be promising catalysts for the electrochemical hydrogen evolution reaction (HER) and 3D-printing enables fast prototyping and manufacturing of water splitting devices. However, the merging of TMDs with complex 3D-printed surfaces and nanostructures as well as their localized characterization remains challenging. In this work, electrodeposition of MoS2 and WS2 and their heterojunctions are used to modify thermally activated 3D-printed nanocarbon structures. Their electrochemical performance for the HER is investigated macroscopically by linear sweep voltammetry and microscopically by scanning electrochemical microscopy. This study demonstrates different local HER active sites of MoS2 and WS2 within the 3D-printed nanocarbon structure that are not solely located at the outer surface, but also in the interior up to ∼150 μm for MoS2 and ∼300 μm for WS2.

Ready-to-use 3D-printed electrochemical cell for in situ voltammetry of immobilized microparticles and Raman spectroscopy

We report in this communication a ready-to-use fused deposition modeling (FDM) based 3D-printed spectroelectrochemical cell to perform for the first time voltammetry of immobilized microparticles (VIMP) and Raman spectroscopy in situ using acrylonitrile butadiene styrene (ABS) as the filament material for printing. The 3D-printed cell was applied to evaluate solid state electrochemical behavior of tadalafil as a proof-of-concept. Several advantages were achieved in the use of the developed device, such as less manipulation of the working electrode, monitoring the same region of the solid microparticles before and after electrochemical measurements, better control of the laser incidence, low-cost and low-time production. Furthermore, the device was printed in a single-step, without handling to assembly and it has an estimated material cost of approximately 2 $. The use of 3D-printing technology was significantly important to integrate Raman spectroscopic method with VIMP measurements and to support mechanism elucidation and characterization of the compounds with less manipulation of the working electrode, avoiding loss of solid products formed from electrochemical reactions.

Tailoring capacitance of 3D-printed graphene electrodes by carbonisation temperature

3D-printing is an emerging technology that can be used for the fast prototyping and decentralised production of objects with complex geometries. Concretely, carbon-based 3D-printed electrodes have emerged as promising components for electrochemical capacitors. However, such electrodes usually require some post-treatments to be electrically active. Herein, 3D-printed nanocomposite electrodes made from a polylactic acid/nanocarbon filament have been characterised through different carbonisation temperatures in order to improve the conductivity of the electrodes via insulating polymer removal. Importantly, the carbonisation temperature has demonstrated to be a key parameter to tailor the capacitive behaviour of the resulting electrodes. Accordingly, this work opens new insights in advanced 3D-printed carbon-based electrodes employing thermal activation.