Holographic patterning of high-performance on-chip 3D lithium-ion microbatteries

3D-Printed Polymeric Biomaterials for Health Applications

3D printing, also known as additive manufacturing, holds immense potential for rapid prototyping and customized production of functional health-related devices. With advancements in polymer chemistry and biomedical engineering, polymeric biomaterials have become integral to 3D-printed biomedical applications. However, there still exists a bottleneck in the compatibility of polymeric biomaterials with different 3D printing methods, as well as intrinsic challenges such as limited printing resolution and rates. Therefore, this review aims to introduce the current state-of-the-art in 3D-printed functional polymeric health-related devices. It begins with an overview of the landscape of 3D printing techniques, followed by an examination of commonly used polymeric biomaterials. Subsequently, examples of 3D-printed biomedical devices are provided and classified into categories such as biosensors, bioactuators, soft robotics, energy storage systems, self-powered devices, and data science in bioplotting. The emphasis is on exploring the current capabilities of 3D printing in manufacturing polymeric biomaterials into desired geometries that facilitate device functionality and studying the reasons for material choice. Finally, an outlook with challenges and possible improvements in the near future is presented, projecting the contribution of general 3D printing and polymeric biomaterials in the field of healthcare.

Tailor-Made Design of Three-Dimensional Batteries Using a Simple, Accurate Geometry Optimization Scheme

In the rapidly evolving Internet of Things (IoT) society, the demand for microbatteries with high areal energy density is surging. As a promising strategy to enhance areal energy density, three-dimensional (3D) batteries have attracted attention. The feature of 3D batteries is the decoupling of the electrode thickness from the ion-transport distance through the modification of the spatial arrangement of the positive and negative electrodes beyond the conventional parallel plates configuration. This allows for the accommodation of a larger amount of active materials without increasing internal resistance. However, identifying the optimal 3D geometry is a complex task, as it depends on printable materials, the resolution of the fabrication equipment, as well as battery usage, which constitutes a multiobjective optimization problem. To overcome this challenge, we propose a novel approach to determine the optimal 3D microbattery geometry. Our innovative method involves a 3D battery optimization system, which integrates an automatic geometry generator with a quick and accurate performance simulator. This approach allows, for the first time, the discovery of material- and discharge-current-dependent optimal geometries. We successfully apply this optimization scheme to two standard electrode pairs (LiFePO4/Li4Ti5O12 and LiNi0.5Mn0.3Co0.2O2/graphite), demonstrating a significant increase in energy density (30%-40% greater than the current state-of-the-art geometry), particularly under high current conditions. These findings underscore the importance of tailor-made batteries for diverse IoT applications and showcase the potential of our approach in realizing such designs.

Exploring role of microbatteries in enhancing sustainability and functionality of implantable biosensors and bioelectronics

Microbatteries are emerging as a sustainable, miniaturized power source, crucial for implantable biomedical devices. Their significance lies in offering high energy density, longevity, and rechargeability, facilitating uninterrupted health monitoring and treatment within the body. The review delves into the development of microbatteries, emphasizing their miniaturization and biocompatibility, crucial for long-term, safe in-vivo use. It examines cutting-edge manufacturing techniques like physical and chemical vapor deposition, and atomic layer deposition, essential for the precision manufacture of the microbatteries. The paper contrasts primary and secondary batteries, highlighting the advantages of zinc-ion and magnesium-ion batteries for enhanced stability and reduced reactivity. It also explores biodegradable batteries, potentially obviating the need for surgical extraction post-use. The integration of microbatteries into diagnostic and therapeutic devices is also discussed, illustrating how they enhance the efficacy and sustainability of implantable biosensors and bioelectronics.

Integrated Structural Modulation Inducing Fast Charge Transfer in Aqueous Zinc-Ion Batteries

Aqueous Zn-ion batteries (AZIBs) are promising energy-storage devices owing to their exceptional safety, long cycle life, simple production, and high storage capacity. Manganese oxides are considered potential cathode materials for AZIBs, primarily because of their safety, low cost, simple synthesis, and high storage capacity. However, MnO2-based cathodes tend to deteriorate structurally during long-term cycling, which reduces their reversible capacity. In this study, an advanced α-MnO2@SnO2 nanocomposite via facile hydrothermal synthesis is developed. The synergistic effects of lattice disorder and increased electron conductivity in the α-MnO2@SnO2 nanocomposite mitigate structural degradation and enhance the overall electrochemical performance. The nanocomposite exhibits a high reversible capacity of 347 mAh g-1 at a current density of 100 mA g-1 after 50 cycles. Furthermore, it exhibits excellent rate performance and stable capacity even after 1000 cycles, maintaining a capacity of 78 mAh g-1 at a high current density of 5 A g-1. This excellent electrochemical performance is attributed to the reversible Zn intercalation in α-MnO2@SnO2 nanocomposites due to the increased structural stability and fast ion/electron exchange caused by the distortion of the tunnel structure, on the basis of various ex situ experiments, density functional theory calculations, and electrochemical characterizations.

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.

Insights into Nano- and Micro-Structured Scaffolds for Advanced Electrochemical Energy Storage

Adopting a nano- and micro-structuring approach to fully unleashing the genuine potential of electrode active material benefits in-depth understandings and research progress toward higher energy density electrochemical energy storage devices at all technology readiness levels. Due to various challenging issues, especially limited stability, nano- and micro-structured (NMS) electrodes undergo fast electrochemical performance degradation. The emerging NMS scaffold design is a pivotal aspect of many electrodes as it endows them with both robustness and electrochemical performance enhancement, even though it only occupies complementary and facilitating components for the main mechanism. However, extensive efforts are urgently needed toward optimizing the stereoscopic geometrical design of NMS scaffolds to minimize the volume ratio and maximize their functionality to fulfill the ever-increasing dependency and desire for energy power source supplies. This review will aim at highlighting these NMS scaffold design strategies, summarizing their corresponding strengths and challenges, and thereby outlining the potential solutions to resolve these challenges, design principles, and key perspectives for future research in this field. Therefore, this review will be one of the earliest reviews from this viewpoint.

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.

Nanoscale Vertical Resolution in Optical Printing of Inorganic Nanoparticles

Direct optical printing of functional inorganics shows tremendous potential as it enables the creation of intricate two-dimensional (2D) patterns and affordable design and production of various devices. Although there have been recent advancements in printing processes using short-wavelength light or pulsed lasers, the precise control of the vertical thickness in printed 3D structures has received little attention. This control is vital to the diverse functionalities of inorganic thin films and their devices, as they rely heavily on their thicknesses. This lack of research is attributed to the technical intricacy and complexity involved in the lithographic processes. Herein, we present a generalized optical 3D printing process for inorganic nanoparticles using maskless digital light processing. We develop a range of photocurable inorganic nanoparticle inks encompassing metals, semiconductors, and oxides, combined with photolinkable ligands and photoacid generators, enabling the direct solidification of nanoparticles in the ink medium. Our process creates complex and large-area patterns with a vertical resolution of ∼50 nm, producing 50-nm-thick 2D films and several micrometer-thick 3D architectures with no layer height difference via layer-by-layer deposition. Through fabrication and operation of multilayered switching devices with Au electrodes and Ag-organic resistive layers, the feasibility of our process for cost-effective manufacturing of multilayered devices is demonstrated.

Deeply Reconstructed Hierarchical Ni-Co Microwire for Flexible Ni-Zn Microbattery with Excellent Comprehensive Performance

The rise of flexible electronics calls for efficient microbatteries (MBs) with requirements in energy/power density, stability, and flexibility simultaneously. However, the ever-reported flexible MBs only display progress around certain aspects of energy loading, reaction rate, and electrochemical stability, and it remains challenging to develop a micro-power source with excellent comprehensive performance. Herein, a reconstructed hierarchical Ni-Co alloy microwire is designed to construct flexible Ni-Zn MB. Notably, the interwoven microwires network is directly formed during the synthesis process, and can be utilized as a potential microelectrode which well avoids the toxic additives and the tedious traditional powder process, thus greatly simplifying the manufacture of MB. Meanwhile, the hierarchical alloy microwire is composed of spiny nanostructures and highly active alloy sites, which contributes to deep reconstruction (≈100 nm). Benefiting from the dense self-assembled structure, the fabricated Ni-Zn MB obtained high volumetric/areal energy density (419.7 mWh cm-3 , 1.3 mWh cm-2 ), and ultrahigh rate performance extending the power density to 109.4 W cm-3 (328.3 mW cm-2 ). More surprisingly, the MB assembled by this inherently flexible microwire network is extremely resistant to bending/twisting. Therefore, this novel concept of excellent comprehensive micro-power source will greatly hold great implications for next-generation flexible electronics.

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.

Zn Microbatteries Explore Ways for Integrations in Intelligent Systems

As intelligent microsystems develop, many revolutionary applications, such as the swallowing surgeon proposed by Richard Feynman, are about to evolve. Nonetheless, integrable energy storage satisfying the demand for autonomous operations has emerged as a major obstacle to the deployment of intelligent microsystems. A reason for the lagging development of integrable batteries is the challenge of miniaturization through microfabrication procedures. Lithium batteries, generated by the most successful battery chemistry, are not stable in the air, thus creating major manufacturing challenges. Other cations (Na⁺ , Mg²⁺ , Al³⁺ , K⁺ ) are still in the early stages of development. In contrast, the superior stability of zinc batteries in the air brings high compatibility to microfabrication protocols and has already demonstrated excellent practicability in full-sized devices. To obtain energy-dense and high-power zinc microbatteries within square-millimeter or smaller footprints, sandwich, pillar, and Swiss-roll configurations are developed. Thin interdigital and fiber microbatteries find their applications being integrated into wearable devices and electronic skin. It is foreseeable that zinc microbatteries will find their way into highly integrated microsystems unlocking their full potential for autonomous operation. This review summarizes the material development, configuration innovation, and application-oriented integration of zinc microbatteries.

Microbatteries with twin-Swiss-rolls redefine performance limits in the sub-square millimeter range

To maintain the downscaling of microelectronic devices with footprints less than one square millimeter, next-generation microbatteries should occupy the same area and deliver adequate energy for running a new generation of multi-functional microautonomous systems. However, the current microbattery technology fails in accomplishing this task because the micrometer-sized electrodes are not compatible with on-chip integration protocols and technologies. To tackle this critical challenge, an on-chip Swiss-roll microelectrode architecture is employed that exploits the self-assembly of thin films into ultra-compact device architectures. A twin-Swiss-roll microelectrode on a chip occupies a footprint of 0.045 mm² and delivers an energy density up to 458 μW h cm^-2. After packaging, the footprint of a full cell increases to 0.11 mm² with a high energy density of 181 μW h cm^-2. The volumetric energy density excluding the chip thickness is 16.3 mW h cm^-3. These results open opportunities for deploying microbatteries as energy and power sources to drive smart dust microelectronics and microautonomous systems.

Structured Electrode Additive Manufacturing for Lithium-Ion Batteries

As the world increasingly swaps fossil fuels, significant advances in lithium-ion batteries have occurred over the past decade. Though demand for increased energy density with mechanical stability continues to be strong, attempts to use traditional ink-casting to increase electrode thickness or geometric complexity have had limited success. Here, we combined a nanomaterial orientation with 3D printing and developed a dry electrode processing route, structured electrode additive manufacturing (SEAM), to rapidly fabricate thick electrodes with an out-of-plane aligned architecture with low tortuosity and mechanical robustness. SEAM uses a shear flow of molten feedstock to control the orientation of the anisotropic materials across nano to macro scales, favoring Li-ion transport and insertion. These structured electrodes with 1 mm thickness have more than twice the specific capacity at 1 C compared to slurry-cast electrodes and have higher mechanical properties (compressive strength of 0.84 MPa and modulus of 5 MPa) than other reported 3D-printed electrodes.

Miniaturized lithium-ion batteries for on-chip energy storage

The development of microelectronic products increases the demand for on-chip miniaturized electrochemical energy storage devices as integrated power sources. Such electrochemical energy storage devices need to be micro-scaled, integrable and designable in certain aspects, such as size, shape, mechanical properties and environmental adaptability. Lithium-ion batteries with relatively high energy and power densities, are considered to be favorable on-chip energy sources for microelectronic devices. This review describes the state-of-the-art of miniaturized lithium-ion batteries for on-chip electrochemical energy storage, with a focus on cell micro/nano-structures, fabrication techniques and corresponding material selections. The relationship between battery architecture and form-factors of the cell concerning their mechanical and electrochemical properties is discussed. A series of on-chip functional microsystems created by integrating micro-lithium-ion batteries are highlighted. Finally, the challenges and future perspectives of miniaturized lithium-ion batteries are elaborated with respect to their potential application fields.

Laser Diffraction Zones and Spots from Three-Dimensional Graded Photonic Super-Crystals and Moiré Photonic Crystals

The laser diffraction from periodic structures typically shows isolated and sharp point patterns at zeroth and ±nth orders. Diffraction from 2D graded photonic super-crystals (GPSCs) has demonstrated over 1000 spots due to the fractional diffractions. Here, we report the holographic fabrication of three types of 3D GPSCs through nine beam interferences and their characteristic diffraction patterns. The diffraction spots due to the fractional orders are merged into large-area diffraction zones for these three types of GPSCs. Three distinguishable diffraction patterns have been observed: (a) 3 × 3 Diffraction zones for GPSCs with a weak gradient in unit super-cell, (b) 5 × 5 non-uniform diffraction zones for GPSCs with a strong modulation in long period and a strong gradient in unit super-cell, (c) more than 5 × 5 uniform diffraction zones for GPSCs with a medium gradient in unit super-cell and a medium modulation in long period. The GPSCs with a strong modulation appear as moiré photonic crystals. The diffraction zone pattern not only demonstrates a characterization method for the fabricated 3D GPSCs, but also proves their unique optical properties of the coupling of light from zones with 360° azimuthal angles and broad zenith angles.

A Flexible Aqueous Zinc-Iodine Microbattery with Unprecedented Energy Density

Currently, reported aqueous microbatteries (MBs) only show unsatisfactory electrochemical performance (≤120 mWh cm^-3 volumetric energy density and <1000 μWh cm^-2 areal energy density) and it remains challenging to develop durable aqueous MBs that can simultaneously offer both high volumetric and areal energy density. Herein, an in situ electrodeposition strategy is adopted to construct a flexible aqueous zinc-iodine MB (ZIDMB). Notably, the fabrication process well avoids the use of common additives (such as binders, conductive agents, and toxic solvent) and also bypasses subsequent time-consuming procedures such as grinding, coating, drying, etc., thus greatly simplifying the manufacture of the ZIDMB. Meanwhile, owing to the suppression of the shuttle effect of triiodide ions and the high ionic conductivity of the polyelectrolyte, the ZIDMB can simultaneously deliver record-high volumetric and areal energy densities of 1647.3 mWh cm^-3 and 2339.1 μWh cm^-2 , thus achieving values at least 13.5- and 2.3-fold better than those of best available aqueous MBs, respectively. This work affords an innovative strategy to construct an ideal micro-power-source for future miniaturized and integrated electronics.

Photopatternable Porous Separators for Micro-Electrochemical Energy Storage Systems

The miniaturization of electrochemical energy storage (EES) systems, one of the key challenges facing the rapid expansion of the Internet-of-Things, has been limited by poor performance of the various energy-storage components at the micrometer scale. Here, the development of a unique photopatternable porous separator that overcomes the electrolyte difficulties involving resistive losses at small dimensions is reported. The separator is based on modifying the chemistry of SU-8, an epoxy-derived photoresist, through the addition of a miscible ionic liquid. The ionic liquid serves as a templating agent, which is selectively removed by solution methods, leaving the SU-8 scaffold whose interconnected porosity provides ion transport from the confined liquid electrolyte. The photopatternable separator exhibits good electrochemical, chemical, thermal, and mechanical stability during the operation of electrochemical devices in both 2D and 3D formats. For the latter, the separator demonstrates the ability to form conformal coatings over 3D structures. The development of the photopatternable separator overcomes the electrolyte issues, which have limited progress in the field of micro-EES.

Engineering Stress in Thin Films: An Innovative Pathway Toward 3D Micro and Nanosystems

Transformation of conventional 2D platforms into unusual 3D configurations provides exciting opportunities for sensors, electronics, optical devices, and biological systems. Engineering material properties or controlling and modulating stresses in thin films to pop-up 3D structures out of standard planar surfaces has been a highly active research topic over the last decade. Implementation of 3D micro and nanoarchitectures enables unprecedented functionalities including multiplexed, monolithic mechanical sensors, vertical integration of electronics components, and recording of neuron activities in 3D organoids. This paper provides an overview on stress engineering approaches to developing 3D functional microsystems. The paper systematically presents the origin of stresses generated in thin films and methods to transform a 2D design into an out-of-plane configuration. Different types of 3D micro and nanostructures, along with their applications in several areas are discussed. The paper concludes with current technical challenges and potential approaches and applications of this fast-growing research direction.

Updated Insights into 3D Architecture Electrodes for Micropower Sources

Microbatteries (MBs) and microsupercapacitors (MSCs) are primary on-chip micropower sources that drive autonomous and stand-alone microelectronic devices for implementation of the Internet of Things (IoT). However, the performance of conventional MBs and MSCs is restricted by their 2D thin-film electrode design, and these devices struggle to satisfy the increasing IoT energy demands for high energy density, high power density, and long lifespan. The energy densities of MBs and MSCs can be improved significantly through adoption of a 2D thick-film electrode design; however, their power densities and lifespans deteriorate with increased electrode thickness. In contrast, 3D architecture electrodes offer remarkable opportunities to simultaneously improve MB and MSC energy density, power density, and lifespan. To date, various 3D architecture electrodes have been designed, fabricated, and investigated for MBs and MSCs. This review provides an update on the principal superiorities of 3D architecture electrodes over 2D thick-film electrodes in the context of improved MB and MSC energy density, power density, and lifespan. In addition, the most recent and representative progress in 3D architecture electrode development for MBs and MSCs is highlighted. Finally, present challenges are discussed and key perspectives for future research in this field are outlined.

Tuning the Mechanical and Electrical Properties of Porous Electrodes for Architecting 3D Microsupercapacitors with Batteries-Level Energy

Microsupercapacitors (MSCs) are vital power sources for internet of things (IoTs) and miniaturized electronics. The performance of MSCs is often restricted by its low areal energy density, which is due to the low areal mass loading of active materials. Constructing thick planar microelectrode with fine structure and high aspect ratio is an efficient way to increase mass loading, but limited by the breakable nature of porous electrode materials. Here, it is found that the mechanical and electrical properties of porous electrodes, as well as their surface area utilization and internal ion diffusion pathway, can be synergistically tuned by infilling gel electrolyte into internal pores of porous electrode films. The tuned thick porous electrode films are robust enough to enable laser ablation of three dimensional (3D) microelectrodes for high mass loading and high aspect ratio. The areal capacitance of 3D microelectrodes is able to increase linearly with mass loading (or thickness) up to at least 13 mg cm^-2  (or 260 µm) for a value of up to 4640 mF cm^-2 based on active carbon. The 3D MSCs deliver areal energy density of 1318 μWh cm^-2 , which is comparable to the best of Li-ion 3D microbatteries while exhibiting superior electrochemical and mechanical stability.

Multitasking MXene Inks Enable High-Performance Printable Microelectrochemical Energy Storage Devices for All-Flexible Self-Powered Integrated Systems

The future of mankind holds great promise for things like the Internet of Things, personal health monitoring systems, and smart cities. To achieve this ambitious goal, it is imperative for electronics to be wearable, environmentally sustainable, and safe. However, large-scale manufacture of self-sufficient electronic systems by exploiting multifunctional materials still faces significant hurdles. Herein, multitasking aqueous printable MXene inks are reported as an additive-free high-capacitance electrode, sensitive pressure-sensing material, highly conducting current collector, metal-free interconnector, and conductive binder. By directly screen printing MXene inks, MXene-based micro-supercapacitors (MSCs) and lithium-ion microbatteries (LIMBs) are delicately fabricated on various substrates. The as-prepared MSCs exhibit ultrahigh areal capacitance of 1.1 F cm^-2 and the serially connected MSCs offer a record voltage of 60 V. The quasi-solid-state LIMBs deliver a robust areal energy density of 154 μWh cm^-2 . Furthermore, an all-flexible self-powered integrated system on a single substrate based on the multitasking MXene inks is demonstrated through seamless integration of a tandem solar cell, the LIMB, and an MXene hydrogel pressure sensor. Notably, this integrated system is exceptionally sensitive to body movements with a fast response time of 35 ms. Therefore, this multipurpose MXene ink opens a new avenue for powering future smart appliances.

High-Performance Packaged 3D Lithium-Ion Microbatteries Fabricated Using Imprint Lithography

Fabrication of high-energy-density and high-power-density packaged long-cycle-life rechargeable microbatteries remains a considerable challenge. Here, high-performance microbatteries with high active volume fraction, thick, 3D-structured electrodes (V₂ O₅ cathode and Li metal anode) are realized through a combination of imprint lithography, self-assembly, and electrodeposition. To assist the critical challenge of hermetic packaging, the microbattery is infilled with a gel electrolyte. The packaged cell exhibits high areal energy and power densities of 1.24 J cm^-2 and 75.5 mW cm^-2 , respectively, and can be cycled 550 times in argon or 200 times in air with 75% capacity retention of the initial discharge capacity. An unpackaged cell, using a liquid electrolyte, provides a power density of 218 mW cm^-2 . As far as it is known, the microbatteries have the highest peak power density among all reported microbatteries.

Electroplated Functional Materials with 3D Nanostructures Defined by Advanced Optical Lithography and Their Emerging Applications

Electroplating has been favored to date as a surface treatment technology in various industries in the development of semiconductors, automobiles, ships, and steel due to its advantages of being a simple, solution-based process, with low cost and high throughput. Recently, classical electroplating has been reborn as an advanced manufacturing process for functional materials by combining it with unconventional optical three-dimensional (3D) nanofabrication techniques capable of generating polymer templates with high-resolution 3D periodic nanostructures. The bottom-up filling behavior of electroplating rising from a seed layer makes it possible to densely fill the nanoporous network of the template with heterogeneous inorganic materials. At this time, understanding and optimizing the process parameters (e.g., additive, current density, type of current waveform, etc.) of electroplating is critical for defect control. In addition, since electroplating is generally performed near room temperature, unlike other thin film deposition techniques, structural damage to the polymer template by heat during electroplating is almost negligible. Based on the excellent compatibility of electroplating and optical 3D nanofabrication, innovative functional materials with 3D periodic nanostructures targeting electrochemical or energy-related applications have been created. In this mini review, a strategy for producing functional materials with 3D periodic nanostructures through a templating process will be covered, and the recent cases of successful applications to electrodes for energy storage devices, electrocatalysts, and thermoelectric materials will be summarized. We will also discuss technical issues that need to be considered in the process to improve the quality of the resulting functional materials with 3D nanoarchitectures.

Stereolithography Three-Dimensional Printing Solid Polymer Electrolytes for All-Solid-State Lithium Metal Batteries

Liquid-free all-solid-state lithium metal batteries (ASSLMBs) are promising candidates to meet the requirements of safety and high energy density for energy storages. However, poor interfacial contact is a major obstacle limiting their applications. Herein, we report a solid polymer electrolyte (SPE), originally prepared by stereolithography (SLA) three-dimensional (3D) printing for ASSLMBs. A 3D-Archimedean spiral structured SPE is rationally designed, which can shorten the Li-ion transport pathway from the electrolyte into the electrode, reinforce the interfacial adhesion, and improve the mass loading of active materials. The SLA printed SPE exhibits a high ionic conductivity of 3.7 × 10^-4 S cm^-1 at 25 °C. Furthermore, Li|3D-SPE|LFP cells achieve reduced interfacial impedance and higher specific capacity of 128 mAh g^-1 after 250 cycles than those using structure-free SPE of 32 mAh g^-1. This work opens the great promise of SLA 3D printing technology to fabricate high-performance SPEs in ASSLMBs for next-generation energy storages.

Recent Advances in High-Performance Microbatteries: Construction, Application, and Perspective

High-performance miniaturized energy storage devices have developed rapidly in recent years. Different from conventional energy storage devices, microbatteries assume the main responsibility for micropower supply, functionalization, and characterization platforms. Evolving from the essential goals for battery design of high power density, high energy density, and long lifetime, further practical demands for microbatteries (MBs) have been raised for the microfabrication technique and device design. Numerous studies have generally focused on specific aspects of the microelectrode structures or certain microfabrication techniques, while the connection from techniques to functional applications is rarely involved. This Review generally fills such blanks from an application-oriented perspective. First, some basic micromachining techniques with different compatible features are summarized. Afterward, device designs including diversified battery reaction types, configuration, and assembly are highlighted, as well as microbatteries serving powering resources or further complicated functional systems. Finally, through providing the overall design concept based on requirements in application, this Review offers innovative insights for further development of microbatteries.

Stress-Actuated Spiral Microelectrode for High-Performance Lithium-Ion Microbatteries

Miniaturization of batteries lags behind the success of modern electronic devices. Neither the device volume nor the energy density of microbatteries meets the requirement of microscale electronic devices. The main limitation for pushing the energy density of microbatteries arises from the low mass loading of active materials. However, merely pushing the mass loading through increased electrode thickness is accompanied by the long charge transfer pathway and inferior mechanical properties for long-term operation. Here, a new spiral microelectrode upon stress-actuation accomplishes high mass loading but short charge transfer pathways. At a small footprint area of around 1 mm² , a 21-fold increase of the mass loading is achieved while featuring fast charge transfer at the nanoscale. The spiral microelectrode delivers a maximum area capacity of 1053 µAh cm^-2 with a retention of 67% over 50 cycles. Moreover, the energy density of the cylinder microbattery using the spiral microelectrode as the anode reaches 12.6 mWh cm^-3 at an ultrasmall volume of 3 mm³ . In terms of the device volume and energy density, the cylinder microbattery outperforms most of the current microbattery technologies, and hence provides a new strategy to develop high-performance microbatteries that can be integrated with miniaturized electronic devices.

3D-Microbattery Architectural Design Optimization Using Automatic Geometry Generator and Transmission-Line Model

Optimization of the 3D battery architecture is crucial to improve the performance of microbatteries. However, such optimization is difficult and time consuming by hand for even experts. In this article, we propose a battery optimization system, which consists of an automatic geometry generator and performance simulators. The geometry generator creates feasible 3D batteries without using any human intuition and experience for the spatial arrangement of positive and negative electrodes. For quick evaluation of the internal resistance, which relates power and energy densities, we propose the transmission line model, the so-called 3D porous electrode model, as one of the performance simulators. To show the effectiveness of the optimization system, we designed the lithium-ion microbatteries. In the trade-off frontier for the internal resistance and the capacity, we successfully found a new battery architecture that has higher power and energy densities over the conventional interdigitated plates configuration.

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The automatic geometry generator created feasible 3D microbattery architectures

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The use of TLM enabled quick evaluation of the internal resistance of the 3D battery

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The optimization system could evaluate the performance of 200,000 3D microbatteries

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The optimized battery showed better performance over the interdigitated geometry

Cathode Architectures for Rechargeable Ion Batteries: Progress and Perspectives

To satisfy the rising demand for energy, battery electrodes with higher loading, to simultaneously increase areal energy and power, are necessary. Nevertheless, in conventional thin-film electrodes, there is mutual exclusion between energy (capacity) and power. Increasing the thickness of electrodes alone is not feasible since this will lead to reductions in ion-diffusion efficiency, as well as electrode flexibility. To address this difficulty, 3D electrode architectures, especially cathode architectures, are proposed to pave a new path for the design and optimization of battery devices. Recent research suggests that 3D cathode architectures may optimize the configuration and engineering processes of battery technologies. Herein, the state-of-the-art progress of cathode architectures in various rechargeable-ion-battery technologies is summarized. Emphasis is placed on the different architecture strategies, areal loading, and mechanical understanding of 3D electrodes. Upcoming research directions are further outlined for future development in this field.

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

Additive manufacturing has revolutionized the building of materials, and 3D-printing has become a useful tool for complex electrode assembly for batteries and supercapacitors. The field initially grew from extrusion-based methods and quickly evolved to photopolymerization printing, while supercapacitor technologies less sensitive to solvents more often involved material jetting processes. The need to develop higher-resolution multimaterial printers is borne out in the performance data of recent 3D printed electrochemical energy storage devices. Underpinning every part of a 3D-printable battery are the printing method and the feed material. These influence material purity, printing fidelity, accuracy, complexity, and the ability to form conductive, ceramic, or solvent-stable materials. The future of 3D-printable batteries and electrochemical energy storage devices is reliant on materials and printing methods that are co-operatively informed by device design. Herein, the material and method requirements in 3D-printable batteries and supercapacitors are addressed and requirements for the future of the field are outlined by linking existing performance limitations to requirements for printable energy-storage materials, casings, and direct printing of electrodes and electrolytes. A guide to materials and printing method choice best suited for alternative-form-factor energy-storage devices to be designed and integrated into the devices they power is thus provided.

Electrodeposition Technologies for Li-Based Batteries: New Frontiers of Energy Storage

Electrodeposition induces material syntheses on conductive surfaces, distinguishing it from the widely used solid-state technologies in Li-based batteries. Electrodeposition drives uphill reactions by applying electric energy instead of heating. These features may enable electrodeposition to meet some needs for battery fabrication that conventional technologies can rarely achieve. The latest progress of electrodeposition technologies in Li-based batteries is summarized. Each component of Li-based batteries can be electrodeposited or synthesized with multiple methods. The advantages of electrodeposition are the main focus, and they are discussed in comparison with traditional technologies with the expectation to inspire innovations to build better Li-based batteries. Electrodeposition coats conformal films on surfaces and can control the film thickness, providing an effective approach to enhancing battery performance. Engineering interfaces by electrodeposition can stabilize the solid electrolyte interphase (SEI) and strengthen the adhesion of active materials to substrates, thereby prolonging the battery longevity. Lastly, a perspective of future studies on electrodepositing batteries is provided. The significant merits of electrodeposition should greatly advance the development of Li-based batteries.

Inverse Design Strategies for 3D Surfaces Formed by Mechanically Guided Assembly

Deterministic transformations of 2D patterns of materials into well-controlled 3D mesostructures serve as the basis for manufacturing methods that can bypass limitations of conventional 3D micro/nanofabrication. Here, guided mechanical buckling processes provide access to a rich range of complex 3D mesostructures in high-performance materials, from inorganic and organic semiconductors, metals and dielectrics, to ceramics and even 2D materials (e.g., graphene, MoS₂ ). Previous studies demonstrate that iterative computational procedures can define design parameters for certain targeted 3D configurations, but without the ability to address complex shapes. A technical need is in efficient, generalized inverse design algorithms that directly yield sets of optimized parameters. Here, such schemes are introduced, where the distributions of thicknesses across arrays of separated or interconnected ribbons provide scalable routes to 3D surfaces with a broad range of targeted shapes. Specifically, discretizing desired shapes into 2D ribbon components allows for analytic solutions to the inverse design of centrally symmetric and even general surfaces, in an approximate manner. Combined theoretical, numerical, and experimental studies of ≈20 different 3D structures with characteristic sizes (e.g., ribbon width) ranging from ≈200 µm to ≈2 cm and with geometries that resemble hemispheres, fire balloons, flowers, concave lenses, saddle surfaces, waterdrops, and rodents, illustrate the essential ideas.

All Two-Dimensional Pseudocapacitive Sheet Materials for Flexible Asymmetric Solid-State Planar Microsupercapacitors with High Energy Density

With the rapid development of portable devices and wireless protocols, miniaturized energy storage units have become an important prerequisite. Although in-plane microsupercapacitors are emerging as competitive candidate devices, their practical applications have been severely hindered by their low energy density. Here, employing pseudocapacitive active materials working in complementary voltage windows, namely, manganese oxide (MnO₂) and titanium carbide (Ti₃C₂), both in the two-dimensional sheet morphology, a flexible asymmetric interdigitated solid-state microsupercapacitor was assembled. Profiting from the perfect voltage complementarity of the two types of sheets, the high exposure of electrochemically active sites and the maximized utilization of the sheets due to the planar ion transport, the designed device achieved excellent electrochemical performance even when using a gel electrolyte. In particular, the device obtained a high specific capacitance of 106 F g^-1 (295 mF cm^-2), a wide potential window (2 V), an ultrahigh rate performance (retaining 83% even with a 20-fold in current density to 20 A g^-1), an excellent cycling stability (87% retention after 10⁴ cycles at 10 A g^-1), and a competitive energy density of 58 W h kg^-1 (162 μW h cm^-2) that are even comparable to those of some microbatteries, while maintaining a high power density of 985 W kg^-1 (2.7 mW cm^-2). Importantly, this outstanding electrochemical performance was also stably maintained under various bending conditions. These results indicate that two-dimensional pseudocapacitive sheet materials have a plethora of possibilities for constructing flexible and wearable devices.

Nanoelectrode design from microminiaturized honeycomb monolith with ultrathin and stiff nanoscaffold for high-energy micro-supercapacitors

Downsizing the cell size of honeycomb monoliths to nanoscale would offer high freedom of nanostructure design beyond their capability for broad applications in different fields. However, the microminiaturization of honeycomb monoliths remains a challenge. Here, we report the fabrication of microminiaturized honeycomb monoliths-honeycomb alumina nanoscaffold-and thus as a robust nanostructuring platform to assemble active materials for micro-supercapacitors. The representative honeycomb alumina nanoscaffold with hexagonal cell arrangement and 400 nm inter-cell spacing has an ultrathin but stiff nanoscaffold with only 16 ± 2 nm cell-wall-thickness, resulting in a cell density of 4.65 × 10⁹ cells per square inch, a surface area enhancement factor of 240, and a relative density of 0.0784. These features allow nanoelectrodes based on honeycomb alumina nanoscaffold synergizing both effective ion migration and ample electroactive surface area within limited footprint. A micro-supercapacitor is finally constructed and exhibits record high performance, suggesting the feasibility of the current design for energy storage devices.

Photopatterning and Electrochemical Energy Storage Properties of an On-Chip Organic Radical Microbattery

One potential way to fabricate battery-on-chip is photopatterning electrochemical energy storage materials directly on electronics through lithography, but applicable materials are primarily limited to transparent photocurable resins. The transparency of the photoresist would be sacrificed after extra addition of insoluble inorganic battery materials and conductors. Given the importance of radical polymers for their appropriate solubility, optical transparency, and radical robustness, they may have potential application in on-chip energy storage, transport, and conversion devices. Herein, an anodic photoresist is proposed by modifying the MicroChem SU8 resist with a radical polymer poly(2,2,6,6-tetramethyl-4-piperidinyl-N-oxyl methacrylate) and an ionic conductor lithium perchlorate. It can be photopatterned on silicon wafer with 10 μm scale resolution, and it exhibits charge/discharge potentials at ca. 0.68 V versus silver chloride electrode; the coulomb efficiency is regarded as nearly equaling 100%. Although the specific capacity of the photopatterned film electrode is found to be modest, 1 × 10^-5 mA h·cm^-2, it presents 1/8 of its theoretical electron storage ability. All-solid-state half-cells with circular features 30 μm in diameter are prepared by means of overlay exposure using the as-prepared photoresist and lithium perchlorate-modified SU8 as the anodic electrode and solid electrolyte, respectively. These results suggest a promising way of using radical polymers for the integration of electrochemical energy in microelectronics.

All-Solid-State Planar Sodium-Ion Microcapacitors with Multidirectional Fast Ion Diffusion Pathways

With the relentless development of smart and miniaturized electronics, the worldwide thirst for microscale electrochemical energy storage devices with form factors is launching a new era of competition. Herein, the first prototype planar sodium-ion microcapacitors (NIMCs) are constructed based on the interdigital microelectrodes of urchin-like sodium titanate as faradaic anode and nanoporous activated graphene as non-faradaic cathode along with high-voltage ionogel electrolyte on a single flexible substrate. By effectively coupling with battery-type anode and capacitor-type cathode, the resultant all-solid-state NIMCs working at 3.5 V exhibit a high volumetric energy density of 37.1 mWh cm-3 and an ultralow self-discharge rate of 44 h from V max to 0.6 V max, both of which surpass most reported hybrid micro-supercapacitors. Through tuning graphene layer covered on the top surface of interdigital microelectrodes, the NIMCs unveil remarkably enhanced power density, owing to the establishment of favorable multidirectional fast ion diffusion pathways that significantly reduce the charge transfer resistance. Meanwhile, the as-fabricated NIMCs present excellent mechanical flexibility without capacitance fade under repeated deformation, and electrochemical stability at a high temperature of 80 °C because of using nonflammable ionogel electrolyte and in-plane geometry. Therefore, these flexible planar NIMCs with multidirectional ion diffusion pathways hold tremendous potential for microelectronics.

The Road Towards Planar Microbatteries and Micro-Supercapacitors: From 2D to 3D Device Geometries

The rapid development and further modularization of miniaturized and self-powered electronic systems have substantially stimulated the urgent demand for microscale electrochemical energy storage devices, e.g., microbatteries (MBs) and micro-supercapacitors (MSCs). Recently, planar MBs and MSCs, composed of isolated thin-film microelectrodes with extremely short ionic diffusion path and free of separator on a single substrate, have become particularly attractive because they can be directly integrated with microelectronic devices on the same side of one single substrate to act as a standalone microsized power source or complement miniaturized energy-harvesting units. The development of and recent advances in planar MBs and MSCs from the fundamentals and design principle to the fabrication methods of 2D and 3D planar microdevices in both in-plane and stacked geometries are highlighted. Additonally, a comprehensive analysis of the primary aspects that eventually affect the performance metrics of microscale energy storage devices, such as electrode materials, electrolyte, device architecture, and microfabrication techniques are presented. The technical challenges and prospective solutions for high-energy-density planar MBs and MSCs with multifunctionalities are proposed.

Metasurface-generated complex 3-dimensional optical fields for interference lithography

Fast submicrometer-scale 3D printing techniques are of interest for various applications ranging from photonics and electronics to tissue engineering. Interference lithography is a versatile 3D printing method with the ability to generate complicated nanoscale structures. Its application, however, has been hindered by either the complicated setups in multibeam lithography that cause sensitivity and impede scalability or the limited level of control over the fabricated structure achievable with mask-assisted processes. Here, we show that metasurface masks can generate complex volumetric intensity distributions with submicrometer scales for fast and scalable 3D printing. These results push the limits of optical devices in controlling the light intensity distribution and significantly increase the realm of possibilities for 3D printing.

Fast, large-scale, and robust 3-dimensional (3D) fabrication techniques for patterning a variety of structures with submicrometer resolution are important in many areas of science and technology such as photonics, electronics, and mechanics with a wide range of applications from tissue engineering to nanoarchitected materials. From several promising 3D manufacturing techniques for realizing different classes of structures suitable for various applications, interference lithography with diffractive masks stands out for its potential to fabricate complex structures at fast speeds. However, the interference lithography masks demonstrated generally suffer from limitations in terms of the patterns that can be generated. To overcome some of these limitations, here we propose the metasurface-mask–assisted 3D nanofabrication which provides great freedom in patterning various periodic structures. To showcase the versatility of this platform, we design metasurface masks that generate exotic periodic lattices like gyroid, rotated cubic, and diamond structures. As a proof of concept, we experimentally demonstrate a diffractive element that can generate the diamond lattice.

Transformation of 2D Planes into 3D Soft and Flexible Structures with Embedded Electrical Functionality

Three-dimensional (3D) structures composed of flexible and soft materials have been in demand for implantable biomedical devices. However, the fabrication of 3D structures using microelectromechanical system (MEMS) techniques has limitations in terms of the materials and the scale of the structures. Here, a technique to selectively bond polydimethylsiloxane (PDMS) and parylene-C by plasma treatment is reported, with which two-dimensional structures that are fabricated using MEMS techniques are turned into 3D structures by the inflation of selectively non-bonded patterns. The bonding strength and the bonding mechanism were analyzed by mechanical tests and chemical analyses, respectively. We fabricated soft and flexible 3D structures with various patterns and dimensions, even with embedded electrical functions, including light emitting diodes and electrocorticogram electrodes. Based on these results, the flexible, soft, and MEMS-capable 3D structures that are obtained by the developed selective bonding technique are promising for applications in a wide range of biomedical applications.

Dual-phase nanostructuring of layered metal oxides for high-performance aqueous rechargeable potassium ion microbatteries

Aqueous rechargeable microbatteries are promising on-chip micropower sources for a wide variety of miniaturized electronics. However, their development is plagued by state-of-the-art electrode materials due to low capacity and poor rate capability. Here we show that layered potassium vanadium oxides, K_xV₂O₅·nH₂O, have an amorphous/crystalline dual-phase nanostructure to show genuine potential as high-performance anode materials of aqueous rechargeable potassium-ion microbatteries. The dual-phase nanostructured K_xV₂O₅·nH₂O keeps large interlayer spacing while removing secondary-bound interlayer water to create sufficient channels and accommodation sites for hydrated potassium cations. This unique nanostructure facilitates accessibility/transport of guest hydrated potassium cations to significantly improve practical capacity and rate performance of the constituent K_xV₂O₅·nH₂O. The potassium-ion microbatteries with K_xV₂O₅·nH₂O anode and K_xMnO₂·nH₂O cathode constructed on interdigital-patterned nanoporous metal current microcollectors exhibit ultrahigh energy density of 103 mWh cm⁻³ at electrical power comparable to carbon-based microsupercapacitors.

Aqueous rechargeable microbatteries could enable new microelectronics, but their current electrode materials still suffer from low capacity and poor rate capability. Here the authors show that layered K_xV₂O₅·nH₂O with an amorphous/crystalline dual-phase nanostructure can address these issues.

Harnessing the interface mechanics of hard films and soft substrates for 3D assembly by controlled buckling

Techniques for forming sophisticated, 3D mesostructures in advanced, functional materials are of rapidly growing interest, owing to their potential uses across a broad range of fundamental and applied areas of application. Recently developed approaches to 3D assembly that rely on controlled buckling mechanics serve as versatile routes to 3D mesostructures in a diverse range of high-quality materials and length scales of relevance for 3D microsystems with unusual function and/or enhanced performance. Nonlinear buckling and delamination behaviors in materials that combine both weak and strong interfaces are foundational to the assembly process, but they can be difficult to control, especially for complex geometries. This paper presents theoretical and experimental studies of the fundamental aspects of adhesion and delamination in this context. By quantifying the effects of various essential parameters on these processes, we establish general design diagrams for different material systems, taking into account 4 dominant delamination states (wrinkling, partial delamination of the weak interface, full delamination of the weak interface, and partial delamination of the strong interface). These diagrams provide guidelines for the selection of engineering parameters that avoid interface-related failure, as demonstrated by a series of examples in 3D helical mesostructures and mesostructures that are reconfigurable based on the control of loading-path trajectories. Three-dimensional micromechanical resonators with frequencies that can be selected between 2 distinct values serve as demonstrative examples.

Strategies for Building Robust Traffic Networks in Advanced Energy Storage Devices: A Focus on Composite Electrodes

The charge transport system in an energy storage device (ESD) fundamentally controls the electrochemical performance and device safety. As the skeleton of the charge transport system, the "traffic" networks connecting the active materials are primary structural factors controlling the transport of ions/electrons. However, with the development of ESDs, it becomes very critical but challenging to build traffic networks with rational structures and mechanical robustness, which can support high energy density, fast charging and discharging capability, cycle stability, safety, and even device flexibility. This is especially true for ESDs with high-capacity active materials (e.g., sulfur and silicon), which show notable volume change during cycling. Therefore, there is an urgent need for cost-effective strategies to realize robust transport networks, and an in-depth understanding of the roles of their structures and properties in device performance. To address this urgent need, the primary strategies reported recently are summarized here into three categories according to their controllability over ion-transport networks, electron-transport networks, or both of them. More specifically, the significant studies on active materials, binders, electrode designs based on various templates, pore additives, etc., are introduced accordingly. Finally, significant challenges and opportunities for building robust charge transport system in next-generation energy storage devices are discussed.

Spray-Printed and Self-Assembled Honeycomb Electrodes of Silicon-Decorated Carbon Nanofibers for Li-Ion Batteries

Directional, micron-scale honeycomb pores in Li-ion battery electrodes were fabricated using a layer-by-layer, self-assembly approach based on spray-printing of carbon nanofibers. By controlling the drying behavior of each printed electrode layer through optimization of (i) the volume ratio of fugitive bisolvent carriers in the suspension and (ii) the substrate temperature during printing, self-assembled, honeycomb pore channels through the electrode were created spontaneously and reliably on current collector areas larger than 20 cm × 15 cm. The honeycomb pore structure promoted efficient Li-ion dynamics at high charge/discharge current densities. Incorporating an optimum fraction (2.5 wt %) of high-energy-density Si particulate into the honeycomb electrodes provided a 4-fold increase in deliverable discharge capacity at 8000 mA/g. The spray-printed, honeycomb pore electrodes were then investigated as negative electrodes coupled with similar spray-printed LiFePO₄ positive electrodes in a full Li-ion cell configuration, providing an approximately 50% improvement in rate capacity retention over half-cell configurations of identical electrodes at 4000 mA/g.

Flexible Electronics Based on Micro/Nanostructured Paper

Over the past several years, a new surge of interest in paper electronics has arisen due to the numerous merits of simple micro/nanostructured substrates. Herein, the latest advances and principal issues in the design and fabrication of paper-based flexible electronics are highlighted. Following an introduction of the fascinating properties of paper matrixes, the construction of paper substrates from diverse functional materials for flexible electronics and their underlying principles are described. Then, notable progress related to the development of versatile electronic devices is discussed. Finally, future opportunities and the remaining challenges are examined. It is envisioned that more design concepts, working principles, and advanced papermaking techniques will be developed in the near future for the advanced functionalization of paper, paving the way for the mass production and commercial applications of flexible paper-based electronic devices.

3D Printing Fiber Electrodes for an All-Fiber Integrated Electronic Device via Hybridization of an Asymmetric Supercapacitor and a Temperature Sensor

Wearable fiber-shaped electronic devices have drawn abundant attention in scientific research fields, and tremendous efforts are dedicated to the development of various fiber-shaped devices that possess sufficient flexibility. However, most studies suffer from persistent limitations in fabrication cost, efficiency, the preparation procedure, and scalability that impede their practical application in flexible and wearable fields. In this study, a simple, low-cost 3D printing method capable of high manufacturing efficiency, scalability, and complexity capability to fabricate a fiber-shaped integrated device that combines printed fiber-shaped temperature sensors (FTSs) with printed fiber-shaped asymmetric supercapacitors (FASCs) is developed. The FASCs device can provide stable output power to FTSs. Moreover, the temperature responsivity of the integrated device is 1.95% °C-1.

Laser-etch patterning of metal oxide coated carbon nanotube 3D architectures

This paper describes a way to fabricate novel hybrid low density nanostructures containing both carbon nanotubes (CNTs) and ceramic nanotubes. Using atomic layer deposition, a thin film of aluminum oxide was conformally deposited on aligned multiwall CNT foams in which the CNTs make porous, three-dimensional interconnected networks. A CO₂ laser was used to etch pure alumina nanotube structures by burning out the underlying CNT substrate in discrete locations via the printed laser pattern. Structural and morphological transitions during the calcination process of aluminum oxide coated CNTs were investigated through in situ transmission electron microscopy and high-resolution scanning electron microscopy. Laser parameters were optimized to etch the CNT away (i.e. etching speed, power and focal length) while minimizing damage to the alumina nanotubes due to overheating. This study opens a new route for fabricating very low density three dimensionally patterned materials with areas of dissimilar materials and properties. To demonstrate the attributes of these structures, the etched areas were used toward anisotropic microfluidic liquid flow. The demonstration used the full thickness of the material to make complex pathways for the liquid flow in the structure. Through tuning of processing conditions, the alumina nanotube (etched) regions became hydrophilic while the bulk material remained hydrophobic and electrically conductive.