In the past decade, there has been tremendous progress in integrating chalcogenide phase-change materials (PCMs) on the silicon photonic platform for non-volatile memory to neuromorphic in-memory computing applications. In particular, these non von Neumann computational elements and systems benefit from mass manufacturing of silicon photonic integrated circuits (PICs) on 8-inch wafers using a 130 nm complementary metal-oxide semiconductor line. Chip manufacturing based on deep-ultraviolet lithography and electron-beam lithography enables rapid prototyping of PICs, which can be integrated with high-quality PCMs based on the wafer-scale sputtering technique as a back-end-of-line process. In this article, we present an overview of recent advances in waveguide integrated PCM memory cells, functional devices, and neuromorphic systems, with an emphasis on fabrication and integration processes to attain state-of-the-art device performance. After a short overview of PCM based photonic devices, we discuss the materials properties of the functional layer as well as the progress on the light guiding layer, namely, the silicon and germanium waveguide platforms. Next, we discuss the cleanroom fabrication flow of waveguide devices integrated with thin films and nanowires, silicon waveguides and plasmonic microheaters for the electrothermal switching of PCMs and mixed-mode operation. Finally, the fabrication of photonic and photonic–electronic neuromorphic computing systems is reviewed. These systems consist of arrays of PCM memory elements for associative learning, matrix-vector multiplication, and pattern recognition. With large-scale integration, the neuromorphicphotonic computing paradigm holds the promise to outperform digital electronic accelerators by taking the advantages of ultra-high bandwidth, high speed, and energy-efficient operation in running machine learning algorithms.

Metal additive manufacturing (AM) has been extensively studied in recent decades. Despite the significant progress achieved in manufacturing complex shapes and structures, challenges such as severe cracking when using existing alloys for laser powder bed fusion (L-PBF) AM have persisted. These challenges arise because commercial alloys are primarily designed for conventional casting or forging processes, overlooking the fast cooling rates, steep temperature gradients and multiple thermal cycles of L-PBF. To address this, there is an urgent need to develop novel alloys specifically tailored for L-PBF technologies. This review provides a comprehensive summary of the strategies employed in alloy design for L-PBF. It aims to guide future research on designing novel alloys dedicated to L-PBF instead of adapting existing alloys. The review begins by discussing the features of the L-PBF processes, focusing on rapid solidification and intrinsic heat treatment. Next, the printability of the four main existing alloys (Fe-, Ni-, Al- and Ti-based alloys) is critically assessed, with a comparison of their conventional weldability. It was found that the weldability criteria are not always applicable in estimating printability. Furthermore, the review presents recent advances in alloy development and associated strategies, categorizing them into crack mitigation-oriented, microstructure manipulation-oriented and machine learning-assisted approaches. Lastly, an outlook and suggestions are given to highlight the issues that need to be addressed in future work.

Driven by the growing demand for next-generation displays, the development of advanced luminescent materials with exceptional photoelectric properties is rapidly accelerating, with such materials including quantum dots and phosphors, etc. Nevertheless, the primary challenge preventing the practical application of these luminescent materials lies in meeting the required durability standards. Atomic layer deposition (ALD) has, therefore, been employed to stabilize luminescent materials, and as a result, flexible display devices have been fabricated through material modification, surface and interface engineering, encapsulation, cross-scale manufacturing, and simulations. In addition, the appropriate equipment has been developed for both spatial ALD and fluidized ALD to satisfy the low-cost, high-efficiency, and high-reliability manufacturing requirements. This strategic approach establishes the groundwork for the development of ultra-stable luminescent materials, highly efficient light-emitting diodes (LEDs), and thin-film packaging. Ultimately, this significantly enhances their potential applicability in LED illumination and backlighted displays, marking a notable advancement in the display industry.

Lightweight aluminum (Al) alloys have been widely used in frontier fields like aerospace and automotive industries, which attracts great interest in additive manufacturing (AM) to process high-value Al parts. As a mainstream AM technique, laser-directed energy deposition (LDED) shows good scalability to meet the requirements for large-format component manufacturing and repair. However, LDED Al alloys are highly challenging due to their inherent poor printability (e.g. low laser absorption, high oxidation sensitivity and cracking tendency). To further promote the development of LDED high-performance Al alloys, this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys. The porosity, cracking, distortion, inclusions, element evaporation and resultant inferior mechanical properties (worse than laser powder bed fusion) are the key challenges in LDED Al alloys. Processing parameter optimizations, in-situ alloy design, reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys. The underlying correlations between processes, alloy innovation, characteristic microstructures, and achievable performances in LDED Al alloys are discussed. The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized. This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys. Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.

The heat generation of electronic devices is increasing dramatically, which causes a serious bottleneck in the thermal management of electronics, and overheating will result in performance deterioration and even device damage. With the development of micro-machining technologies, the microchannel heat sink (MCHS) has become one of the best ways to remove the considerable amount of heat generated by high-power electronics. It has the advantages of large specific surface area, small size, coolant saving and high heat transfer coefficient. This paper comprehensively takes an overview of the research progress in MCHSs and generalizes the hotspots and bottlenecks of this area. The heat transfer mechanisms and performances of different channel structures, coolants, channel materials and some other influencing factors are reviewed. Additionally, this paper classifies the heat transfer enhancement technology and reviews the related studies on both the single-phase and phase-change flow and heat transfer. The comprehensive review is expected to provide a theoretical reference and technical guidance for further research and application of MCHSs in the future.

The traditional von Neumann computing architecture has relatively-low information processing speed and high power consumption, making it difficult to meet the computing needs of artificial intelligence (AI). Neuromorphic computing systems, with massively parallel computing capability and low power consumption, have been considered as an ideal option for data storage and AI computing in the future. Memristor, as the fourth basic electronic component besides resistance, capacitance and inductance, is one of the most competitive candidates for neuromorphic computing systems benefiting from the simple structure, continuously adjustable conductivity state, ultra-low power consumption, high switching speed and compatibility with existing CMOS technology. The memristors with applying MXene-based hybrids have attracted significant attention in recent years. Here, we introduce the latest progress in the synthesis of MXene-based hybrids and summarize their potential applications in memristor devices and neuromorphological intelligence. We explore the development trend of memristors constructed by combining MXenes with other functional materials and emphatically discuss the potential mechanism of MXenes-based memristor devices. Finally, the future prospects and directions of MXene-based memristors are briefly described.

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.

The development of various artificial electronics and machines would explosively increase the amount of information and data, which need to be processed via in-situ remediation. Bioinspired synapse devices can store and process signals in a parallel way, thus improving fault tolerance and decreasing the power consumption of artificial systems. The organic field effect transistor (OFET) is a promising component for bioinspired neuromorphic systems because it is suitable for large-scale integrated circuits and flexible devices. In this review, the organic semiconductor materials, structures and fabrication, and different artificial sensory perception systems functions based on neuromorphic OFET devices are summarized. Subsequently, a summary and challenges of neuromorphic OFET devices are provided. This review presents a detailed introduction to the recent progress of neuromorphic OFET devices from semiconductor materials to perception systems, which would serve as a reference for the development of neuromorphic systems in future bioinspired electronics.

The burning of fossil fuels in industry results in significant carbon emissions, and the heat generated is often not fully utilized. For high-temperature industries, thermophotovoltaics (TPVs) is an effective method for waste heat recovery. This review covers two aspects of high-efficiency TPV systems and industrial waste heat applications. At the system level, representative results of TPV complete the systems, while selective emitters and photovoltaic cells in the last decade are compiled. The key points of components to improve the energy conversion efficiency are further analyzed, and the related micro/nano-fabrication methods are introduced. At the application level, the feasibility of TPV applications in high-temperature industries is shown from the world waste heat utilization situation. The potential of TPV in waste heat recovery and carbon neutrality is illustrated with the steel industry as an example.

Fluid lubricated bearings have been widely adopted as support components for high-end equipment in metrology, semiconductor devices, aviation, strategic defense, ultraprecision manufacturing, medical treatment, and power generation. In all these applications, the equipment must deliver extreme working performances such as ultraprecise movement, ultrahigh rotation speed, ultraheavy bearing loads, ultrahigh environmental temperatures, strong radiation resistance, and high vacuum operation, which have challenged the design and optimization of reliable fluid lubricated bearings. Breakthrough of any related bottlenecks will promote the development course of high-end equipment. To promote the advancement of high-end equipment, this paper reviews the design and optimization of fluid lubricated bearings operated at typical extreme working performances, targeting the realization of extreme working performances, current challenges and solutions, underlying deficiencies, and promising developmental directions. This paper can guide the selection of suitable fluid lubricated bearings and optimize their structures to meet their required working performances.

3D printing stands at the forefront of transforming space exploration, offering unprecedented on-demand and rapid manufacturing capabilities. It adeptly addresses challenges such as mass reduction, intricate component fabrication, and resource constraints. Despite the obstacles posed by microgravity and extreme environments, continual advancements underscore the pivotal role of 3D printing in aerospace science. Beyond its primary function of producing space structures, 3D printing contributes significantly to progress in electronics, biomedicine, and resource optimization. This perspective delves into the technological advantages, environmental challenges, development status, and opportunities of 3D printing in space. Envisioning its crucial impact, we anticipate that 3D printing will unlock innovative solutions, reshape manufacturing practices, and foster self-sufficiency in future space endeavors.

Additive manufacturing provides achievability for the fabrication of bimetallic and multi-material structures; however, the material compatibility and bondability directly affect the parts' formability and final quality. It is essential to understand the underlying printability of different material combinations based on an adapted process. Here, the printability disparities of two common and attractive material combinations (nickel- and iron-based alloys) are evaluated at the macro and micro levels via laser directed energy deposition (DED). The deposition processes were captured using in situ high-speed imaging, and the dissimilarities in melt pool features and track morphology were quantitatively investigated within specific process windows. Moreover, the microstructure diversity of the tracks and blocks processed with varied material pairs was comparatively elaborated and, complemented with the informative multi-physics modeling, the presented non-uniformity in mechanical properties (microhardness) among the heterogeneous material pairs was rationalized. The differences in melt flow induced by the unlike thermophysical properties of the material pairs and the resulting element intermixing and localized re-alloying during solidification dominate the presented dissimilarity in printability among the material combinations. This work provides an in-depth understanding of the phenomenological differences in the deposition of dissimilar materials and aims to guide more reliable DED forming of bimetallic parts.

Recent advances in functionally graded additive manufacturing (FGAM) technology have enabled the seamless hybridization of multiple functionalities in a single structure. Soft robotics can become one of the largest beneficiaries of these advances, through the design of a facile four-dimensional (4D) FGAM process that can grant an intelligent stimuli-responsive mechanical functionality to the printed objects. Herein, we present a simple binder jetting approach for the 4D printing of functionally graded porous multi-materials (FGMM) by introducing rationally designed graded multiphase feeder beds. Compositionally graded cross-linking agents gradually form stable porous network structures within aqueous polymer particles, enabling programmable hygroscopic deformation without complex mechanical designs. Furthermore, a systematic bed design incorporating additional functional agents enables a multi-stimuli-responsive and untethered soft robot with stark stimulus selectivity. The biodegradability of the proposed 4D-printed soft robot further ensures the sustainability of our approach, with immediate degradation rates of 96.6% within 72 h. The proposed 4D printing concept for FGMMs can create new opportunities for intelligent and sustainable additive manufacturing in soft robotics.

There is a perpetual pursuit for free-form glasses and ceramics featuring outstanding mechanical properties as well as chemical and thermal resistance. It is a promising idea to shape inorganic materials in three-dimensional (3D) forms to reduce their weight while maintaining high mechanical properties. A popular strategy for the preparation of 3D inorganic materials is to mold the organic–inorganic hybrid photoresists into 3D micro- and nano-structures and remove the organic components by subsequent sintering. However, due to the discrete arrangement of inorganic components in the organic-inorganic hybrid photoresists, it remains a huge challenge to attain isotropic shrinkage during sintering. Herein, we demonstrate the isotropic sintering shrinkage by forming the consecutive –Si–O–Si–O–Zr–O– inorganic backbone in photoresists and fabricating 3D glass–ceramic nanolattices with enhanced mechanical properties. The femtosecond (fs) laser is used in two-photon polymerization (TPP) to fabricate 3D green body structures. After subsequent sintering at 1000 ◦C, high-quality 3D glass–ceramic microstructures can be obtained with perfectly intact and smooth morphology. In-suit compression experiments and finite-element simulations reveal that octahedral-truss (oct-truss) lattices possess remarkable adeptness in bearing stress concentration and maintain the structural integrity to resist rod bending, indicating that this structure is a candidate for preparing lightweight and high stiffness glass–ceramic nanolattices. 3D printing of such glasses and ceramics has significant implications in a number of industrial applications, including metamaterials, microelectromechanical systems, photonic crystals, and damage-tolerant lightweight materials.

It is a challenge to polish the interior surface of an additively manufactured component with complex structures and groove sizes less than 1 mm. Traditional polishing methods are disabled to polish the component, meanwhile keeping the structure intact. To overcome this challenge, small-grooved components made of aluminum alloy with sizes less than 1 mm were fabricated by a custom-made printer. A novel approach to multi-phase jet (MPJ) polishing is proposed, utilizing a self-developed polisher that incorporates solid, liquid, and gas phases. In contrast, abrasive air jet (AAJ) polishing is recommended, employing a customized polisher that combines solid and gas phases. After jet polishing, surface roughness (Sa) on the interior surface of grooves decreases from pristine 8.596 µm to 0.701 µm and 0.336 µm via AAJ polishing and MPJ polishing, respectively, and Sa reduces 92% and 96%, correspondingly. Furthermore, a formula defining the relationship between linear energy density and unit defect volume has been developed. The optimized parameters in additive manufacturing are that linear energy density varies from 0.135 J mm^-1 to 0.22 J mm^-1. The unit area defect volume achieved via the optimized parameters decreases to 1/12 of that achieved via non-optimized ones. Computational fluid dynamics simulation results reveal that material is removed by shear stress, and the alumina abrasives experience multiple collisions with the defects on the heat pipe groove, resulting in uniform material removal. This is in good agreement with the experimental results. The novel proposed setups, approach, and findings provide new insights into manufacturing complex-structured components, polishing the small-grooved structure, and keeping it unbroken.

High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications, such as high-performance heat transfer enhancement and surface plasmon devices. However, the fast and cost-effective fabrication of high-aspect-ratio microstructures on metallic surfaces remains challenging for existing techniques. This study proposes a novel cutting-based process, namely elliptical vibration chiseling (EV-chiseling), for the high-efficiency texturing of surface microstructures with an ultrahigh aspect ratio. Unlike conventional cutting, EV-chiseling superimposes a microscale EV on a backward-moving tool. The tool chisels into the material in each vibration cycle to generate an upright chip with a high aspect ratio through material deformation. Thanks to the tool's backward movement, the chip is left on the material surface to form a microstructure rather than falling off. Since one microstructure is generated in one vibration cycle, the process can be highly efficient using ultrafast (>1 kHz) tool vibration. A finite element analysis model is established to explore the process mechanics of EV-chiseling. Next, a mechanistic model of the microstructured surface generation is developed to describe the microstructures' aspect ratio dependency on the process parameters. Then, surface texturing tests are performed on copper to verify the efficacy of EV-chiseling. Uniformed micro ribs with a spacing of 1–10 μm and an aspect ratio of 2–5 have been successfully textured on copper. Compared with the conventional EV-cutting that uses a forward-moving tool, EV-chiseling can improve the aspect ratio of textured microstructure by up to 40 times. The experimental results also verify the accuracy of the developed surface generation model of microstructures. Finally,the effects of elliptical trajectory, depth of cut, tool shape, and tool edge radius on the surface generation of micro ribs have been discussed.

Elucidating the complex interactions between the work material and abrasives during grinding of gallium nitride (GaN) single crystals is an active and challenging research area. In this study, molecular dynamics simulations were performed on double-grits interacted grinding of GaN crystals; and the grinding force, coefficient of friction, stress distribution, plastic damage behaviors, and abrasive damage were systematically investigated. The results demonstrated that the interacted distance in both radial and transverse directions achieved better grinding quality than that in only one direction. The grinding force, grinding induced stress, subsurface damage depth, and abrasive wear increase as the transverse interacted distance increases. However, there was no clear correlation between the interaction distance and the number of atoms in the phase transition and dislocation length. Appropriate interacted distances between abrasives can decrease grinding force, coefficient of friction, grinding induced stress, subsurface damage depth, and abrasive wear during the grinding process. The results of grinding tests combined with cross-sectional transmission electron micrographs validated the simulated damage results, i.e. amorphous atoms, high-pressure phase transition, dislocations, stacking faults, and lattice distortions. The results of this study will deepen our understanding of damage accumulation and material removal resulting from coupling between abrasives during grinding and can be used to develop a feasible approach to the wheel design of ordered abrasives.

Hydrogels inevitably undergo dehydration, structural collapse, and shrinkage deformation due to the uninterrupted evaporation in the atmosphere, thereby losing their flexibility, slipperiness, and manufacturing precision. Here, we propose a novel bioinspired strategy to construct a spontaneously formed 'skin' on the slippery hydrogels by incorporating biological stress metabolites trehalose into the hydrogel network, which can generate robust hydrogen bonding interactions to restrain water evaporation. The contents of trehalose in hydrogel matrix can also regulate the desiccation-tolerance, mechanical properties, and lubricating performance of slippery hydrogels in a wide range. Combining vat photopolymerization three-dimensional printing and trehalose-modified slippery hydrogels enables to achieve the structural hydrogels with high resolution, shape fidelity, and sophisticated architectures, instead of structural collapse and shrinkage deformation caused by dehydration. And thus, this proposed functional hydrogel adapts to manufacture large-scale hydrogels with sophisticated architectures in a long-term process. As a proof-of-concept demonstration, a high-precision and sophisticated slippery hydrogel vascular phantom was easily fabricated to imitate guidewire intervention. Additionally, the proposed protocol is universally applicable to diverse types of hydrogel systems. This strategy opens up a versatile methodology to fabricate dry-resistant slippery hydrogel for functional structures and devices, expanding their high-precision processing and broad applications in the atmosphere.

The controllable transfer of droplets on the surface of objects has a wide application prospect in the fields of microfluidic devices, fog collection and so on. The Leidenfrost effect can be utilized to significantly reduce motion resistance. However, the use of 3D structures limits the widespread application of self-propulsion based on Leidenfrost droplets in microelectromechanical system. To manipulate Leidenfrost droplets, it is necessary to create 2D or quasi-2D geometries. In this study, femtosecond laser is applied to fabricate a surface with periodic hydrophobicity gradient (SPHG), enabling directional self-propulsion of Leidenfrost droplets. Flow field analysis within the Leidenfrost droplets reveals that the vapor layer between the droplets and the hot surface can be modulated by the SPHG, resulting in directional propulsion of the inner gas. The viscous force between the gas and liquid then drives the droplet to move.

Small-scale electromagnetic soft actuators are characterized by a fast response and simple control, holding prospects in the field of soft and miniaturized robotics. The use of liquid metal (LM) to replace a rigid conductor inside soft actuators can reduce the rigidity and enhance the actuation performance and robustness. Despite research efforts, challenges persist in the flexible fabrication of LM soft actuators and in the improvement of actuation performance. To address these challenges, we developed a fast and robust electromagnetic soft microplate actuator based on a laser-induced selective adhesion transfer method. Equipped with unprecedentedly thin LM circuit and customized low Young’s modulus silicone rubber (1.03 kPa), our actuator exhibits an excellent deformation angle (265.25°) and actuation bending angular velocity (284.66 rad·s^-1). Furthermore, multiple actuators have been combined to build an artificial gripper with a wide range of functionalities. Our actuator presents new possibilities for designing small-scale artificial machines and supports advancements in ultrafast soft and miniaturized robotics.