Direct Ink Writing of Polymer Composite Electrolytes with Enhanced Thermal Conductivities

The Role of 3D Printing Technologies in Soft Grippers

Soft grippers are essential for precise and gentle handling of delicate, fragile, and easy-to-break objects, such as glassware, electronic components, food items, and biological samples, without causing any damage or deformation. This is especially important in industries such as healthcare, manufacturing, agriculture, food handling, and biomedical, where accuracy, safety, and preservation of the objects being handled are critical. This article reviews the use of 3D printing technologies in soft grippers, including those made of functional materials, nonfunctional materials, and those with sensors. 3D printing processes that can be used to fabricate each class of soft grippers are discussed. Available 3D printing technologies that are often used in soft grippers are primarily extrusion-based printing (fused deposition modeling and direct ink writing), jet-based printing (polymer jet), and immersion printing (stereolithography and digital light processing). The materials selected for fabricating soft grippers include thermoplastic polymers, UV-curable polymers, polymer gels, soft conductive composites, and hydrogels. It is conclude that 3D printing technologies revolutionize the way soft grippers are being fabricated, expanding their application domains and reducing the difficulties in customization, fabrication, and production.

Oriented Structures for High Safety, Rate Capability, and Energy Density Lithium Metal Batteries

Lithium metal batteries (LMBs) have emerged in recent years as highly promising candidates for high-density energy storage systems. Despite their immense potential, mutual constraints arise when optimizing energy density, rate capability, and operational safety, which greatly hinder the commercialization of LMBs. The utilization of oriented structures in LMBs appears as a promising strategy to address three key performance barriers: 1) low efficiency of active material utilization at high surface loading, 2) easy formation of Li dendrites and damage to interfaces under high-rate cycling, and 3) low ionic conductivity of solid-state electrolytes in high safety LMBs. This review aims to holistically introduce the concept of oriented structures, provide criteria for quantifying the degree of orientation, and elucidate their systematic effects on the properties of materials and devices. Furthermore, a detailed categorization of oriented structures is proposed to offer more precise guidance for the design of LMBs. This review also provides a comprehensive summary of preparation techniques for oriented structures and delves into the mechanisms by which these can enhance the energy density, rate capability, and safety of LMBs. Finally, potential applications of oriented structures in LMBs and the crucial challenges that need to be addressed in this field are explored.

Ink-based additive manufacturing for electrochemical applications

Additive manufacturing (AM), commonly known as three-dimensional (3D) printing, has drawn substantial attention in recent decades due to its efficiency and precise control in part fabrication. The limitations of conventional fabrication processes, especially regarding geometry complexity, supply chain, and environmental impact, have prompted the exploration of diverse AM technologies in electrochemistry. Especially, three ink-based AM techniques, binder jet printing (BJP), direct ink writing (DIW), and Inkjet Printing (IJP), have been extensively applied by numerous research teams to produce electrodes, catalyst scaffolds, supercapacitors, batteries, etc. BJP's versatility in utilizing a wide range of materials as powder feedstock promotes its potential for various electrode and battery applications. DIW and IJP stand out for their ability to handle multi-material manufacturing tasks and deliver high printing resolution. To capture recent advancements in this field, we present a comprehensive review of the applications of BJP, DIW, and IJP techniques in fabricating electrochemical devices and components. This review intends to provide an overview of the process-structure-property relationship in electrochemical materials and components across diverse applications manufactured using AM techniques. We delve into how the significantly improved design freedom over the structure offered by these ink-based AM techniques highlights the performance of electrochemical products. Moreover, we highlight their advantages in terms of material compatibility, geometry control, and cost-effectiveness. In specific cases, we also compare the performance of electrochemical components fabricated using AM and conventional manufacturing methods. Finally, we conclude this review article by offering some insights into the future development in this research field.

Ceria Quantum Dot Filler-Modified Polymer Electrolytes for Three-Dimensional-Printed Sodium Solid-State Batteries

Solid polymer electrolytes have been considered as promising candidates for solid-state batteries (SSBs), owing to their excellent interfacial compatibility and high mechanical toughness; however, they suffer from intrinsic low ionic conductivity (lower than 10-6 S/cm) and large thickness (usually surpassed over 100 μm or even 500 μm), which has a negative influence on the interface resistance and ionic migration. In this work, ceria quantum dot (CQD)-modified composite polymer electrolyte (CPE) membranes with a thickness of 20 μm were successfully manufactured via 3D printing technology. The CQD fillers can reduce the crystallinity of the polymer, and the oxygen vacancies on CQDs can facilitate the dissociation of ion pairs in the NaTFSI salt to release more free Na+, improving the ionic conductivity. Meanwhile, tailoring the thickness of the CPE-CQDs membrane via 3D printing can further promote the migration and transport of Na+. Furthermore, the printed NNM//CPE-CQDs//Na SSB exhibited outstanding rate capability and cycling stability. The combination of CQD modification and thickness tailoring through 3D printing paves a new avenue for achieving high performance solid electrolyte membranes for practical application in Na SSBs.

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.

Electroactive Polymers for On-Demand Drug Release

Conductive materials have played a significant role in advancing society into the digital era. Such materials are able to harness the power of electricity and are used to control many aspects of daily life. Conductive polymers (CPs) are an emerging group of polymers that possess metal-like conductivity yet retain desirable polymeric features, such as processability, mechanical properties, and biodegradability. Upon receiving an electrical stimulus, CPs can be tailored to achieve a number of responses, such as harvesting energy and stimulating tissue growth. The recent FDA approval of a CP-based material for a medical device has invigorated their research in healthcare. In drug delivery, CPs can act as electrical switches, drug release is achieved at a flick of a switch, thereby providing unprecedented control over drug release. In this review, recent developments in CP as electroactive polymers for voltage-stimuli responsive drug delivery systems are evaluated. The review demonstrates the distinct drug release profiles achieved by electroactive formulations, and both the precision and ease of stimuli response. This level of dynamism promises to yield "smart medicines" and warrants further research. The review concludes by providing an outlook on electroactive formulations in drug delivery and highlighting their integral roles in healthcare IoT.

Direct Ink Writing of Carbon-Doped Polymeric Composite Ink: A Review on Its Requirements and Applications

Direct Ink Writing (DIW) opens new possibilities in three-dimensional (3D) printing of carbon-based polymeric ink. This is due to its ability in design flexibility, structural complexity, and environmental sustainability. This area requires exhaustive study because of its wide application in different manufacturing sectors. The present article is related to the variant emerging 3D printing techniques and DIW of carbonaceous materials. Carbon-based materials, extensively used for various applications in 3D printing, possess impressive chemical stability, strength, and flexible nanostructure. Fine printable inks consist predominantly of uniform solutions of carbon materials, such as graphene, graphene oxide (GO), carbon fibers (CFs), carbon nanotubes (CNTs), and solvents. It also contains compatible polymers and suitable additives. This review article elaborately discusses the fundamental requirements of DIW in structuring carbon-doped polymeric inks viz. ink formulation, required ink rheology, extrusion parameters, print fidelity prediction, layer bonding examination, substrate selection, and curing method to achieve fine functional composites. A detailed description of its application in the fields of electronics, medical, and mechanical segments have also been focused in this study.

High-performance fiber-shaped Li-ion battery enabled by a surface-reinforced self-supporting electrode

Herein, we develop a surface-reinforced self-supporting fiber electrode via the simple-yet-reliable ink-extrusion technology to introduce a thin polymer layer at the electrode surface, which endows the fiber architecture with sufficient rigidity for the subsequent fiber cell assembly. Such fiber LiFePO₄//Li₄Ti₅O₁₂ full cells exhibit high linear capacity output (0.144 mA h cm^-1) and energy density (0.267 mW h cm^-1).

Immobilization of photocatalytic materials for (waste)water treatment using 3D printing technology - advances and challenges

Photocatalysis has been considered a promising technology for the elimination of a wide range of pollutants in water. Various types of photocatalysts (i.e., homojunction, heterojunction, dual Z-scheme photocatalyst) have been developed in recent years to address the drawbacks of conventional photocatalysts, such as the large energy band gap and rapid recombination rate of photogenerated electrons and holes. However, there are still challenges in the design of photocatalytic reactors that limit their wider application for real (waste)water treatment, such as difficulties in their recovery and reuse from treated (waste)waters. 3D printing technologies have been introduced very recently for the immobilization of materials in novel photocatalytic reactor designs. The present review aims to summarize and discuss the advances and challenges in the application of various 3D printing technologies (i.e., stereolithography, inkjet printing, and direct ink writing) for the fabrication of stable photocatalytic materials for (waste)water treatment purposes. Furthermore, the limitations in the implementation of these technologies to design future generations of photocatalytic reactors have been critically discussed, and recommendations for future studies have been presented.

Recent Advances in Multi-Material 3D Printing of Functional Ceramic Devices

In recent years, functional ceramic devices have become smaller, thinner, more refined, and highly integrated, which makes it difficult to realize their rapid prototyping and low-cost manufacturing using traditional processing. As an emerging technology, multi-material 3D printing offers increased complexity and greater freedom in the design of functional ceramic devices because of its unique ability to directly construct arbitrary 3D parts that incorporate multiple material constituents without an intricate process or expensive tools. Here, the latest advances in multi-material 3D printing methods are reviewed, providing a comprehensive study on 3D-printable functional ceramic materials and processes for various functional ceramic devices, including capacitors, multilayer substrates, and microstrip antennas. Furthermore, the key challenges and prospects of multi-material 3D-printed functional ceramic devices are identified, and future directions are discussed.

Progress of Polymer-Based Thermally Conductive Materials by Fused Filament Fabrication: A Comprehensive Review

With the miniaturization and integration of electronic products, the heat dissipation efficiency of electronic equipment needs to be further improved. Notably, polymer materials are a choice for electronic equipment matrices because of their advantages of low cost and wide application availability. However, the thermal conductivity of polymers is insufficient to meet heat dissipation requirements, and their improvements remain challenging. For decades, as an efficient manufacturing technology, additive manufacturing has gradually attracted public attention, and researchers have also used this technology to produce new thermally conductive polymer materials. Here, we review the recent research progress of different 3D printing technologies in heat conduction and the thermal conduction mechanism of polymer matrix composites. Based on the classification of fillers, the research progress of thermally conductive materials prepared by fused filament fabrication (FFF) is discussed. It analyzes the internal relationship between FFF process parameters and the thermal conductivity of polymer matrix composites. Finally, this study summarizes the application and future development direction of thermally conductive composites by FFF.

Additive Manufacturing Polyurethane Acrylate via Stereolithography for 3D Structure Polymer Electrolyte Application

Additive manufacturing (AM), also known as 3D-printing technology, is currently integrated in many fields as it possesses an attractive fabrication process. In this work, we deployed the 3D-print stereolithography (SLA) method to print polyurethane acrylate (PUA)-based gel polymer electrolyte (GPE). The printed PUA GPE was then characterized through several techniques, such as Fourier transform infrared (FTIR), electrochemical impedance spectroscopy (EIS), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscope (SEM). The printed GPE exhibited high ionic conductivity of 1.24 × 10-3 S cm-1 at low-lithium-salt content (10 wt.%) in ambient temperature and favorable thermal stability to about 300 °C. The FTIR results show that addition of LiClO4 to the polymer matrix caused a shift in carbonyl, ester and amide functional groups. In addition, FTIR deconvolution peaks of LiClO4 show 10 wt.% has the highest amount of free ions, in line with the highest conductivity achieved. Finally, the PUA GPE was printed into 3D complex structure to show SLA flexibility in designing an electrolyte, which could be a potential application in advanced battery fabrication.

Direct Ink Printing of PVdF Composite Polymer Electrolytes with Aligned BN Nanosheets for Lithium-Metal Batteries

The use of polymer electrolytes is of great interest for lithium-metal batteries (LMBs) due to their stability with lithium metal. However, the low thermal conductivity of polymer electrolytes poses a significant barrier to minimizing the formation of local hot spots during electrochemical reactions in lithium batteries that may lead to dendritic plating of Li or thermal runaway events. Electrolyte nanocomposites with proper distribution of thermally conductive nanomaterials offer an opportunity to address this shortcoming. Utilizing a custom-designed direct ink writing (DIW) process, we show that highly aligned boron nitride (BN) nanosheets can be embedded in poly(vinylidene fluoride-hexafluoropropylene) (PVdF) polymer composite electrolytes (CPE-BN), enabling novel architectural designs for safe Li-metal batteries. It is observed that the CPE-BN electrolytes possess a 400% increase in their in-plane thermal conductivity, which enables faster heat distribution in the CPE-BN electrolyte compared to the polymer electrolytes without BN nanosheets. The CPE-BN containing symmetric lithium cell exhibits stable Li plating/stripping for over 2000 cycles without short-circuiting due to the suppression of dendritic lithium. The lithium-ion half-cells made with the CPE-BN show stable cycling performance at 1C charge-discharge rate for 250 cycles with 90% capacity retention. This reported DIW-printed PVdF composite polymer electrolyte could be used as a model for developing new architectures for other electrolytes or electrodes, thus enabling new chemistry and improved performances in energy-storage devices.

Direct Ink Writing: A 3D Printing Technology for Diverse Materials

Additive manufacturing (AM) has gained significant attention due to its ability to drive technological development as a sustainable, flexible, and customizable manufacturing scheme. Among the various AM techniques, direct ink writing (DIW) has emerged as the most versatile 3D printing technique for the broadest range of materials. DIW allows printing of practically any material, as long as the precursor ink can be engineered to demonstrate appropriate rheological behavior. This technique acts as a unique pathway to introduce design freedom, multifunctionality, and stability simultaneously into its printed structures. Here, a comprehensive review of DIW of complex 3D structures from various materials, including polymers, ceramics, glass, cement, graphene, metals, and their combinations through multimaterial printing is presented. The review begins with an overview of the fundamentals of ink rheology, followed by an in-depth discussion of the various methods to tailor the ink for DIW of different classes of materials. Then, the diverse applications of DIW ranging from electronics to food to biomedical industries are discussed. Finally, the current challenges and limitations of this technique are highlighted, followed by its prospects as a guideline toward possible futuristic innovations.

Eco-friendly chitosan@silver/plant fiber membranes for masks with thermal comfortability and self-sterilization

The surgical masks have been essential consumables for public in the COVID-19 pandemic. However, long-time wearing masks will make wearers feel uncomfortable and massive discarded non-biodegradable masks lead to a heavy burden on our environment. In this paper, we adopt degradable chitosan@silver (CS@Ag) core-shell fibers and plant fibers to prepare an eco-friendly mask with excellent thermal comfort, self-sterilization, and antiviral effects. The thermal network of CS@Ag core-shell fibers highly improves the in-plane thermal conductivity of masks, which is 4.45 times higher than that of commercial masks. Because of the electrical conductivity of Ag, the fabricated mask can be electrically heated to warm the wearer in a cold environment and disinfect COVID-19 facilely at room temperature. Meanwhile, the in-situ reduced silver nanoparticles (AgNPs) endow the mask with superior antibacterial properties. Therefore, this mask shows a great potential to address the urgent need for a thermally comfortable, antibacterial, antiviral, and eco-friendly mask.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10570-022-04582-x.

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.

Intrinsic Field-Induced Nanoparticle Assembly in Three-Dimensional (3D) Printing Polymeric Composites

Nanoparticles (NPs) are materials considered to be 1-100 nm in size and are available in different dimensional shapes, geometrical sizes, physical morphologies, mechanical robustness, and chemical compositions. Irrespective of the dimensions (i.e., zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D)), NPs have a tendency to become entangled together, forming aggregations due to high attraction, making it hard to realize their full potential from their ordered counterparts. Many challenges exist to attain high-quality stabilized dispersion and long-range ordered assembly of NPs. Three-dimensional printing (3DP), also known as additive manufacturing (AM), is a technique dependent on layer-by-layer material addition for building 3D structures and encompasses a few categories based on the feedstock material types and printing mechanisms. One benefit from the 3DP procedures is their capability to produce anisotropic microstructural/nanostructural characteristics for desired mechanical reinforcement, transport phenomena, energy management, and biomedical implants. This paper briefly overviews relevant 3DP methods with an embedded nature to assemble nanoparticles without interference with external fields (e.g., magnetic or electrical). Our focus is the shear-field-induced nanoparticle alignment, covering material jetting-, electrohydrodynamic-, filament melting-, and ink writing-based 3DP. A concise summary of photopolymerization and its "optical tweezer" effects on nanoparticle confinement also inspires creative approaches in generating ordered nanostructures. The nanoparticles and polymers involved in this review are diverse, consisting of metallic, ceramic, and carbon nanoparticles in matrices or on surfaces of varying macromolecules. A short statement of challenges (e.g., low resolution, slow printing speed, limited material options) for 3DP-enabled nanoparticle orders provides some perspectives toward the enormous potential of 3DP in directing NPs assembly and fabricating high-performance polymer/nanoparticle composites.

Aqueous Inks of Pristine Graphene for 3D Printed Microsupercapacitors with High Capacitance

Three-dimensional (3D) printing is gaining importance as a sustainable route for the fabrication of high-performance energy storage devices. It enables the streamlined manufacture of devices with programmable geometry at different length scales down to micron-sized dimensions. Miniaturized energy storage devices are fundamental components for on-chip technologies to enable energy autonomy. In this work, we demonstrate 3D printed microsupercapacitor electrodes from aqueous inks of pristine graphene without the need of high temperature processing and functional additives. With an intrinsic electrical conductivity of ∼1370 S m^-1 and rationally designed architectures, the symmetric microsupercapacitors exhibit an exceptional areal capacitance of 1.57 F cm^-2 at 2 mA cm^-2 which is retained over 72% after repeated voltage holding tests. The areal power density (0.968 mW cm^-2) and areal energy density (51.2 μWh cm^-2) outperform the ones of previously reported carbon-based supercapacitors which have been either 3D or inkjet printed. Moreover, a current collector-free interdigitated microsupercapacitor combined with a gel electrolyte provides electrochemical performance approaching the one of devices with liquid-like ion transport properties. Our studies provide a sustainable and low-cost approach to fabricate efficient energy storage devices with programmable geometry.