International Journal of Extreme Manufacturing

Inspired by natural porous architectures, numerous attempts have been made to generate porous structures. Owing to the smooth surfaces, highly interconnected porous architectures, and mathematical controllable geometry features, triply periodic minimal surface (TPMS) is emerging as an outstanding solution to constructing porous structures in recent years. However, many advantages of TPMS are not fully utilized in current research. Critical problems of the process from design, manufacturing to applications need further systematic and integrated discussions. In this work, a comprehensive overview of TPMS porous structures is provided. In order to generate the digital models of TPMS, the geometry design algorithms and performance control strategies are introduced according to diverse requirements. Based on that, precise additive manufacturing methods are summarized for fabricating physical TPMS products. Furthermore, actual multidisciplinary applications are presented to clarify the advantages and further potential of TPMS porous structures. Eventually, the existing problems and further research outlooks are discussed.

The growing demand for electronic devices, smart devices, and the Internet of Things constitutes the primary driving force for marching down the path of decreased critical dimension and increased circuit intricacy of integrated circuits. However, as sub-10 nm high-volume manufacturing is becoming the mainstream, there is greater awareness that defects introduced by original equipment manufacturer components impact yield and manufacturing costs. The identification, positioning, and classification of these defects, including random particles and systematic defects, are becoming more and more challenging at the 10 nm node and beyond. Very recently, the combination of conventional optical defect inspection with emerging techniques such as nanophotonics, optical vortices, computational imaging, quantitative phase imaging, and deep learning is giving the field a new possibility. Hence, it is extremely necessary to make a thorough review for disclosing new perspectives and exciting trends, on the foundation of former great reviews in the field of defect inspection methods. In this article, we give a comprehensive review of the emerging topics in the past decade with a focus on three specific areas: (a) the defect detectability evaluation, (b) the diverse optical inspection systems, and (c) the post-processing algorithms. We hope, this work can be of importance to both new entrants in the field and people who are seeking to use it in interdisciplinary work.

Polymers are widely used materials in aerospace, automotive, construction, medical devices and pharmaceuticals. Polymers are being promoted rapidly due to their ease of manufacturing and improved material properties. Research on polymer processing technology should be paid more attention to due to the increasing demand for polymer applications. Selective laser sintering (SLS) uses a laser to sinter powdered materials (typical polyamide), and it is one of the critical additive manufacturing (AM) techniques of polymer. It irradiates the laser beam on the defined areas by a computer-aided design three-dimensional (3D) model to bind the material together to create a designed 3D solid structure. SLS has many advantages, such as no support structures and excellent mechanical properties resembling injection moulded parts compared with other AM methods. However, the ability of SLS to process polymers is still affected by some defects, such as the porous structure and limited available types of SLS polymers. Therefore, this article reviews the current state-of-the-art SLS of polymers, including the fundamental principles in this technique, the SLS developments of typical polymers, and the essential process parameters in SLS. Furthermore, the applications of SLS are focused, and the conclusions and perspectives are discussed.

Highlights

• The fundamental principles in selective laser sintering polymers are reviewed.

• The effect of process parameters on the selective laser sintering polymers and the popular polymer materials are discussed.

• The recent applications of selective laser sintering polymers and the future works are explored.

Piezoelectricity in native bones has been well recognized as the key factor in bone regeneration. Thus, bio-piezoelectric materials have gained substantial attention in repairing damaged bone by mimicking the tissue's electrical microenvironment (EM). However, traditional manufacturing strategies still encounter limitations in creating personalized bio-piezoelectric scaffolds, hindering their clinical applications. Three-dimensional (3D)/four-dimensional (4D) printing technology based on the principle of layer-by-layer forming and stacking of discrete materials has demonstrated outstanding advantages in fabricating bio-piezoelectric scaffolds in a more complex-shaped structure. Notably, 4D printing functionality-shifting bio-piezoelectric scaffolds can provide a time-dependent programmable tissue EM in response to external stimuli for bone regeneration. In this review, we first summarize the physicochemical properties of commonly used bio-piezoelectric materials (including polymers, ceramics, and their composites) and representative biological findings for bone regeneration. Then, we discuss the latest research advances in the 3D printing of bio-piezoelectric scaffolds in terms of feedstock selection, printing process, induction strategies, and potential applications. Besides, some related challenges such as feedstock scalability, printing resolution, stress-to-polarization conversion efficiency, and non-invasive induction ability after implantation have been put forward. Finally, we highlight the potential of shape/property/functionality-shifting smart 4D bio-piezoelectric scaffolds in bone tissue engineering (BTE). Taken together, this review emphasizes the appealing utility of 3D/4D printed biological piezoelectric scaffolds as next-generation BTE implants.

Highlights

• Significant findings in bio-piezoelectric material-guided cell behavior and bone tissue engineering are presented.

• Benefits and limitations associated with the latest 3D printing strategies for bio-piezoelectric materials are discussed.

• Challenges and future perspectives on 4D printing smart bio-piezoelectric scaffolds for potential biological applications are outlined.

Atomic layer deposition (ALD) has become an indispensable thin-film technology in the contemporary microelectronics industry. The unique self-limited layer-by-layer growth feature of ALD has outstood this technology to deposit highly uniform conformal pinhole-free thin films with angstrom-level thickness control, particularly on 3D topologies. Over the years, the ALD technology has enabled not only the successful downscaling of the microelectronic devices but also numerous novel 3D device structures. As ALD is essentially a variant of chemical vapor deposition, a comprehensive understanding of the involved chemistry is of crucial importance to further develop and utilize this technology. To this end, we, in this review, focus on the surface chemistry and precursor chemistry aspects of ALD. We first review the surface chemistry of the gas–solid ALD reactions and elaborately discuss the associated mechanisms for the film growth; then, we review the ALD precursor chemistry by comparatively discussing the precursors that have been commonly used in the ALD processes; and finally, we selectively present a few newly-emerged applications of ALD in microelectronics, followed by our perspective on the future of the ALD technology.

Highlights

• The surface chemistry of the gas–solid ALD reactions is reviewed, and the associated mechanisms are elaborately discussed.

• The ALD precursor chemistry is reviewed by comparatively discussing the precursors that have been commonly used.

• Newly-emerged applications of ALD in microelectronics are presented.

• Future perspectives of the ALD technology are outlined.

Three-dimensional (3D) printing, an additive manufacturing technique, is widely employed for the fabrication of various electrochemical energy storage devices (EESDs), such as batteries and supercapacitors, ranging from nanoscale to macroscale. This technique offers excellent manufacturing flexibility, geometric designability, cost-effectiveness, and eco-friendliness. Recent studies have focused on the utilization of 3D-printed critical materials for EESDs, which have demonstrated remarkable electrochemical performances, including high energy densities and rate capabilities, attributed to improved ion/electron transport abilities and fast kinetics. However, there is a lack of comprehensive reviews summarizing and discussing the recent advancements in the structural design and application of 3D-printed critical materials for EESDs, particularly rechargeable batteries. In this review, we primarily concentrate on the current progress in 3D printing (3DP) critical materials for emerging batteries. We commence by outlining the key characteristics of major 3DP methods employed for fabricating EESDs, encompassing design principles, materials selection, and optimization strategies. Subsequently, we summarize the recent advancements in 3D-printed critical materials (anode, cathode, electrolyte, separator, and current collector) for secondary batteries, including conventional Li-ion (LIBs), Na-ion (SIBs), K-ion (KIBs) batteries, as well as Li/Na/K/Zn metal batteries, Zn-air batteries, and Ni–Fe batteries. Within these sections, we discuss the 3DP precursor, designprinciples of 3D structures, and working mechanisms of the electrodes. Finally, we address the major challenges and potential applications in the development of 3D-printed critical materials for rechargeable batteries.

Highlights

• A comprehensive review on the recent advances of various rechargeable batteries utilizing 3D printing technologies to fabricate has been presented.

• Typical features of major 3D-printing methods used for fabricating EESDs, including design principles, materials selectivity, and optimization strategies, are herein outlined;

• 3D-printed critical materials, including anode, cathode, electrolyte, separator, and 3D hosts, for rechargeable batteries, are summarized and discussed;

• Challenges and further research directions for developing 3D-printed critical materials for rechargeable batteries are highlighted.

Nickel-rich layered oxides have been identified as the most promising commercial cathode materials for lithium-ion batteries (LIBs) for their high theoretical specific capacity. However, the poor cycling stability of nickel-rich cathode materials is one of the major barriers for the large-scale usage of LIBs. The existing obstructions that suppress the capacity degradation of nickel-rich cathode materials are as a result of phase transition, mechanical instability, intergranular cracks, side reaction, oxygen loss, and thermal instability during cycling. Core–shell structures, oxidating precursors, electrolyte additives, doping/coating and synthesizing single crystals have been identified as effective methods to improve cycling stability of nickel-rich cathode materials. Herein, recent progress of surface modification, e.g. coating and doping, in nickel-rich cathode materials are summarized based on Periodic table to provide a clear understanding. Electrochemical performances and mechanisms of modified structure are discussed in detail. It is hoped that an overview of synthesis and surface modification can be presented and a perspective of nickel-rich materials in LIBs can be given.

Highlights

• Synthesized process of nickel-rich cathode materials is discussed on their synthetic methods, solvent selections, pH values and sintering temperatures.

• Characterization techniques about nickel-rich cathode materials are summarized and discussed.

• Surface modification of nickel-rich cathode materials is summarized based on Periodic table to provide a clear mechanism.

• A perspective of nickel-rich cathode materials in LIBs is discussed.

• Porous metals are extensively used in load-bearing implants to improve osseointegration.

• Different processing approaches for porous metals are discussed here.

• Static and dynamic mechanical properties are critically reviewed for porous metal implants.

• In vitro and in vivo biological properties of porous metal implants are critically reviewed.

• Current challenges and future directions for porous metal implants are discussed.

Abstract

Porous and functionally graded materials have seen extensive applications in modern biomedical devices—allowing for improved site-specific performance; their appreciable mechanical, corrosive, and biocompatible properties are highly sought after for lightweight and high-strength load-bearing orthopedic and dental implants. Examples of such porous materials are metals, ceramics, and polymers. Although, easy to manufacture and lightweight, porous polymers do not inherently exhibit the required mechanical strength for hard tissue repair or replacement. Alternatively, porous ceramics are brittle and do not possess the required fatigue resistance. On the other hand, porous biocompatible metals have shown tailorable strength, fatigue resistance, and toughness. Thereby, a significant interest in investigating the manufacturing challenges of porous metals has taken place in recent years. Past research has shown that once the advantages of porous metallic structures in the orthopedic implant industry have been realized, their biological and biomechanical compatibility—with the host bone—has been followed up with extensive methodical research. Various manufacturing methods for porous or functionally graded metals are discussed and compared in this review, specifically, how the manufacturing process influences microstructure, graded composition, porosity, biocompatibility, and mechanical properties. Most of the studies discussed in this review are related to porous structures for bone implant applications; however, the understanding of these investigations may also be extended to other devices beyond the biomedical field.

Additive manufacturing (AM) is an emerging customized three-dimensional (3D) functional product fabrication technology. It provides a higher degree of design freedom, reduces manufacturing steps, cost and production cycles. However, existing metallic component 3D printing techniques are mainly for the manufacture of single material components. With the increasing commercial applications of AM technologies, the need for 3D printing of more than one type of dissimilar materials in a single component increases. Therefore, investigations on multi-material AM (MMAM) emerge over the past decade. Lasers are currently widely used for the AM of metallic components where high temperatures are involved. Here we report the progress and trend in laser-based macro- and micro-scale AM of multiple metallic components. The methods covered in this paper include laser powder bed fusion, laser powder directed energy deposition, and laser-induced forward transfer for MMAM applications. The principles and process/material characteristics are described. Potential applications and challenges are discussed. Finally, future research directions and prospects are proposed.

The aerospace community widely uses difficult-to-cut materials, such as titanium alloys, high-temperature alloys, metal/ceramic/polymer matrix composites, hard and brittle materials, and geometrically complex components, such as thin-walled structures, microchannels, and complex surfaces. Mechanical machining is the main material removal process for the vast majority of aerospace components. However, many problems exist, including severe and rapid tool wear, low machining efficiency, and poor surface integrity. Nontraditional energy-assisted mechanical machining is a hybrid process that uses nontraditional energies (vibration, laser, electricity, etc) to improve the machinability of local materials and decrease the burden of mechanical machining. This provides a feasible and promising method to improve the material removal rate and surface quality, reduce process forces, and prolong tool life. However, systematic reviews of this technology are lacking with respect to the current research status and development direction. This paper reviews the recent progress in the nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in the aerospace community. In addition, this paper focuses on the processing principles, material responses under nontraditional energy, resultant forces and temperatures, material removal mechanisms, and applications of these processes, including vibration-, laser-, electric-, magnetic-, chemical-, advanced coolant-, and hybrid nontraditional energy-assisted mechanical machining. Finally, a comprehensive summary of the principles, advantages, and limitations of each hybrid process is provided, and future perspectives on forward design, device development, and sustainability of nontraditional energy-assisted mechanical machining processes are discussed.

Highlights

• A topical review of nontraditional energy-assisted mechanical machining is introduced.

• The advantages and limitations of each hybrid machining process are addressed.

• Perspectives on forward design, device development, and sustainability are discussed.

3D printing techniques offer an effective method in fabricating complex radially multi-material structures. However, it is challenging for complex and delicate radially multi-material model geometries without supporting structures, such as tissue vessels and tubular graft, among others. In this work, we tackle these challenges by developing a polar digital light processing technique which uses a rod as the printing platform. The 3D model fabrication is accomplished through line projection. The rotation and translation of the rod are synchronized to project and illuminate the photosensitive material volume. By controlling the distance between the rod and the printing window, we achieved the printing of tubular structures with a minimum wall thickness as thin as 50 micrometers. By controlling the width of fine slits at the printing window, we achieved the printing of structures with a minimum feature size of 10 micrometers. Our process accomplished the fabrication of thin-walled tubular graft structure with a thickness of only 100 micrometers and lengths of several centimeters within a timeframe of just 100 s. Additionally, it enables the printing of axial multi-material structures, thereby achieving adjustable mechanical strength. This method is conducive to rapid customization of tubular grafts and the manufacturing of tubular components in fields such as dentistry, aerospace, and more.

Highlights

• Polar-coordinate-based line projection enables rapid printing of tubular structures with higher precision and compressive strength.

• Using a cylindrical auxiliary axis allows for the manufacture of radial multi-material structures and facilitates printing of coaxial structures.

• It is beneficial for the rapid customization of tubular implants and for manufacturing tubular components in dentistry, aerospace, and other fields.

Optical imaging systems have greatly extended human visual capabilities, enabling the observation and understanding of diverse phenomena. Imaging technologies span a broad spectrum of wavelengths from x-ray to radio frequencies and impact research activities and our daily lives. Traditional glass lenses are fabricated through a series of complex processes, while polymers offer versatility and ease of production. However, modern applications often require complex lens assemblies, driving the need for miniaturization and advanced designs with micro- and nanoscale features to surpass the capabilities of traditional fabrication methods. Three-dimensional (3D) printing, or additive manufacturing, presents a solution to these challenges with benefits of rapid prototyping, customized geometries, and efficient production, particularly suited for miniaturized optical imaging devices. Various 3D printing methods have demonstrated advantages over traditional counterparts, yet challenges remain in achieving nanoscale resolutions. Two-photon polymerization lithography (TPL), a nanoscale 3D printing technique, enables the fabrication of intricate structures beyond the optical diffraction limit via the nonlinear process of two-photon absorption within liquid resin. It offers unprecedented abilities, e.g. alignment-free fabrication, micro- and nanoscale capabilities, and rapid prototyping of almost arbitrary complex 3D nanostructures. In this review, we emphasize the importance of the criteria for optical performance evaluation of imaging devices, discuss material properties relevant to TPL, fabrication techniques, and highlight the application of TPL in optical imaging. As the first panoramic review on this topic, it will equip researchers with foundational knowledge and recent advancements of TPL for imaging optics, promoting a deeper understanding of the field. By leveraging on its high-resolution capability, extensive material range, and true 3D processing, alongside advances in materials, fabrication, and design, we envisage disruptive solutions to current challenges and a promising incorporation of TPL in future optical imaging applications.

Highlights

• Provide a comprehensive overview of two-photon polymerization lithography (TPL)-based imaging applications.

• Introduce the fundamental imaging theories, key materials properties, and fabrication technologies.

• Classify and summarize the various imaging applications of TPL.

• Envisage the future trends of TPL for imaging optics and offer insights on the potential solutions to current challenges.

Amid the growing interest in triboelectric nanogenerators (TENGs) as novel energy-harvesting devices, several studies have focused on direct current (DC) TENGs to generate a stable DC output for operating electronic devices. However, owing to the working mechanisms of conventional DC TENGs, generating a stable DC output from reciprocating motion remains a challenge. Accordingly, we propose a bidirectional rotating DC TENG (BiR-TENG), which can generate DC outputs, regardless of the direction of rotation, from reciprocating motions. The distinct design of the BiR-TENG enables the mechanical rectification of the alternating current output into a rotational-direction-dependent DC output. Furthermore, it allows the conversion of the rotational-direction-dependent DC output into a unidirectional DC output by adapting the configurations depending on the rotational direction. Owing to these tailored design strategies and subsequent optimizations, the BiR-TENG could generate an effective unidirectional DC output. Applications of the BiR-TENG for the reciprocating motions of swinging doors and waves were demonstrated by harnessing this output. This study demonstrates the potential of the BiR-TENG design strategy as an effective and versatile solution for energy harvesting from reciprocating motions, highlighting the suitability of DC outputs as an energy source for electronic devices.

Highlights

• A mechanical rectification based direct-current triboelectric nanogenerator is developed.

• The system can generate a unidirectional output regardless of direction of rotation.

• A self-adaptive mechanical design is implemented.

• Applications for harvesting abundant ambient reciprocating motion are introduced.

Triboelectric materials with high charge density are the building-block for the commercial application of triboelectric nanogenerators (TENGs). Unstable dynamic processes influence the change of the charge density on the surface and inside of triboelectric materials. The charge density of triboelectric materials depends on the surface and the internal charge transfer processes. The focus of this review is on recent advances in high charge density triboelectric materials and advances in the fabrication of TENGs. We summarize the existing strategies for achieving high charge density in triboelectric materials as well as their fundamental properties. We then review current optimization methods for regulating dynamic charge transfer processes to increase the output charge density: first, increasing charge injection and limiting charge dissipation to achieve a high average surface charge density, and second, regulating the internal charge transfer process and storing charge in triboelectric materials to increase the output charge density. Finally, we present the challenges and prospects in developing high-performance triboelectric materials.

Highlights

• Summarize recent developments in the high charge density of TENG.

• Highlight AC-TENG and DC-TENG and their strategies to increase the charge density.

• Explain the high charge density principle of TENG and its regulation mechanism.

• Demonstrate current methods for manufacturing TENGs and their challenges in system assembly.

• Elucidate future mechanisms, materials, and device directions for satisfying application requirements.

Zinc (Zn) is considered a promising biodegradable metal for implant applications due to its appropriate degradability and favorable osteogenesis properties. In this work, laser powder bed fusion (LPBF) additive manufacturing was employed to fabricate pure Zn with a heterogeneous microstructure and exceptional strength-ductility synergy. An optimized processing window of LPBF was established for printing Zn samples with relative densities greater than 99% using a laser power range of 80 ∼ 90 W and a scanning speed of 900 mm s⁻¹. The Zn sample printed with a power of 80 W at a speed of 900 mm s⁻¹ exhibited a hierarchical heterogeneous microstructure consisting of millimeter-scale molten pool boundaries, micrometer-scale bimodal grains, and nanometer-scale pre-existing dislocations, due to rapid cooling rates and significant thermal gradients formed in the molten pools. The printed sample exhibited the highest ductility of ∼12.1% among all reported LPBF-printed pure Zn to date with appreciable ultimate tensile strength (∼128.7 MPa). Such superior strength-ductility synergy can be attributed to the presence of multiple deformation mechanisms that are primarily governed by heterogeneous deformation-induced hardening resulting from the alternative arrangement of bimodal Zn grains with pre-existing dislocations. Additionally, continuous strain hardening was facilitated through the interactions between deformation twins, grains and dislocations as strain accumulated, further contributing to the superior strength-ductility synergy. These findings provide valuable insights into the deformation behavior and mechanisms underlying exceptional mechanical properties of LPBF-printed Zn and its alloys for implant applications.

Highlights

• A superior strength-ductility synergy was achieved in pure zinc printed by laser powder bed fusion.

• A heterogeneous microstructure with bimodal grains and dislocations was obtained.

• Back-stress hardening, massive dislocations and twins are dominant in deformation.

• Deformation mechanisms responsible for the strength-ductility synergy were revealed.

Optical imaging systems have greatly extended human visual capabilities, enabling the observation and understanding of diverse phenomena. Imaging technologies span a broad spectrum of wavelengths from x-ray to radio frequencies and impact research activities and our daily lives. Traditional glass lenses are fabricated through a series of complex processes, while polymers offer versatility and ease of production. However, modern applications often require complex lens assemblies, driving the need for miniaturization and advanced designs with micro- and nanoscale features to surpass the capabilities of traditional fabrication methods. Three-dimensional (3D) printing, or additive manufacturing, presents a solution to these challenges with benefits of rapid prototyping, customized geometries, and efficient production, particularly suited for miniaturized optical imaging devices. Various 3D printing methods have demonstrated advantages over traditional counterparts, yet challenges remain in achieving nanoscale resolutions. Two-photon polymerization lithography (TPL), a nanoscale 3D printing technique, enables the fabrication of intricate structures beyond the optical diffraction limit via the nonlinear process of two-photon absorption within liquid resin. It offers unprecedented abilities, e.g. alignment-free fabrication, micro- and nanoscale capabilities, and rapid prototyping of almost arbitrary complex 3D nanostructures. In this review, we emphasize the importance of the criteria for optical performance evaluation of imaging devices, discuss material properties relevant to TPL, fabrication techniques, and highlight the application of TPL in optical imaging. As the first panoramic review on this topic, it will equip researchers with foundational knowledge and recent advancements of TPL for imaging optics, promoting a deeper understanding of the field. By leveraging on its high-resolution capability, extensive material range, and true 3D processing, alongside advances in materials, fabrication, and design, we envisage disruptive solutions to current challenges and a promising incorporation of TPL in future optical imaging applications.

Highlights

• Provide a comprehensive overview of two-photon polymerization lithography (TPL)-based imaging applications.

• Introduce the fundamental imaging theories, key materials properties, and fabrication technologies.

• Classify and summarize the various imaging applications of TPL.

• Envisage the future trends of TPL for imaging optics and offer insights on the potential solutions to current challenges.

Triboelectric materials with high charge density are the building-block for the commercial application of triboelectric nanogenerators (TENGs). Unstable dynamic processes influence the change of the charge density on the surface and inside of triboelectric materials. The charge density of triboelectric materials depends on the surface and the internal charge transfer processes. The focus of this review is on recent advances in high charge density triboelectric materials and advances in the fabrication of TENGs. We summarize the existing strategies for achieving high charge density in triboelectric materials as well as their fundamental properties. We then review current optimization methods for regulating dynamic charge transfer processes to increase the output charge density: first, increasing charge injection and limiting charge dissipation to achieve a high average surface charge density, and second, regulating the internal charge transfer process and storing charge in triboelectric materials to increase the output charge density. Finally, we present the challenges and prospects in developing high-performance triboelectric materials.

Highlights

• Summarize recent developments in the high charge density of TENG.

• Highlight AC-TENG and DC-TENG and their strategies to increase the charge density.

• Explain the high charge density principle of TENG and its regulation mechanism.

• Demonstrate current methods for manufacturing TENGs and their challenges in system assembly.

• Elucidate future mechanisms, materials, and device directions for satisfying application requirements.

• The operating mechanism of piezotronic neuromorphic devices and related manufacturing techniques are presented.

• Recent research advances in piezotronic neuromorphic devices including multifunctional applications are summarized.

• Challenges and prospects for modulating novel neuromorphic devices with piezotronic effects are discussed.

Abstract

With the arrival of the era of artificial intelligence (AI) and big data, the explosive growth of data has raised higher demands on computer hardware and systems. Neuromorphic techniques inspired by biological nervous systems are expected to be one of the approaches to breaking the von Neumann bottleneck. Piezotronic neuromorphic devices modulate electrical transport characteristics by piezopotential and directly associate external mechanical motion with electrical output signals in an active manner, with the capability to sense/store/process information of external stimuli. In this review, we have presented the piezotronic neuromorphic devices (which are classified into strain-gated piezotronic transistors and piezoelectric nanogenerator-gated field effect transistors based on device structure) and discussed their operating mechanisms and related manufacture techniques. Secondly, we summarized the research progress of piezotronic neuromorphic devices in recent years and provided a detailed discussion on multifunctional applications, including bionic sensing, information storage, logic computing, and electrical/optical artificial synapses. Finally, in the context of future development, challenges, and perspectives, we have discussed how to modulate novel neuromorphic devices with piezotronic effects more effectively. It is believed that the piezotronic neuromorphic devices have great potential for the next generation of interactive sensation/memory/computation to facilitate the development of the Internet of Things, AI, biomedical engineering, etc.

In the last three decades, carbon dioxide (CO₂) emissions have shown a significant increase from various sources. To address this pressing issue, the importance of reducing CO₂ emissions has grown, leading to increased attention toward carbon capture, utilization, and storage strategies. Among these strategies, monodisperse microcapsules, produced by using droplet microfluidics, have emerged as promising tools for carbon capture, offering a potential solution to mitigate CO₂ emissions. However, the limited yield of microcapsules due to the inherent low flow rate in droplet microfluidics remains a challenge. In this comprehensive review, the high-throughput production of carbon capture microcapsules using droplet microfluidics is focused on. Specifically, the detailed insights into microfluidic chip fabrication technologies, the microfluidic generation of emulsion droplets, along with the associated hydrodynamic considerations, and the generation of carbon capture microcapsules through droplet microfluidics are provided. This review highlights the substantial potential of droplet microfluidics as a promising technique for large-scale carbon capture microcapsule production, which could play a significant role in achieving carbon neutralization and emission reduction goals.

Highlights

• Recent progress in the high-throughput production of carbon capture microcapsules using droplet microfluidics is introduced.

• Manufacturing technologies of microfluidic devices are discussed.

• The methods and hydrodynamics for droplet generation are analyzed.

• Potential applications of droplet microfluidics for carbon capture are presented.

Metal additive manufacturing (AM) technologies have made significant progress in the basic theoretical field since their invention in the 1970s. However, performance instability during continuous processing, such as thermal history, residual stress accumulation, and columnar grain epitaxial growth, consistently hinders their broad application in standardized industrial production. To overcome these challenges, performance-control-oriented hybrid AM (HAM) technologies have been introduced. These technologies, by leveraging external auxiliary processes, aim to regulate microstructural evolution and mechanical properties during metal AM. This paper provides a systematic and detailed review of performance-control-oriented HAM technology, which is categorized into two main groups: energy field-assisted AM (EFed AM, e.g. ultrasonic, electromagnetic, and heat) technologies and interlayer plastic deformation-assisted AM (IPDed AM, e.g. laser shock peening, rolling, ultrasonic peening, and friction stir process) technologies. This review covers the influence of external energy fields on the melting, flow, and solidification behavior of materials, and the regulatory effects of interlayer plastic deformation on grain refinement, nucleation, and recrystallization. Furthermore, the role of performance-control-oriented HAM technologies in managing residual stress conversion, metallurgical defect closure, mechanical property improvement, and anisotropy regulation is thoroughly reviewed and discussed. The review concludes with an analysis of future development trends in EFed AM and IPDed AM technologies.

Highlights

• Performance-control-oriented hybrid additive manufacturing was defined as the review scope.

• Multifarious technologies were classified, summarized and synthesized based on applied objects.

• Microstructural evolution, mechanical property, and defect elimination were depicted and compared.

• The synergetic enhancement of strength and ductility was statistically measured and analyzed.

• Future development trends were predicted on account of the historical outline and research status.