As a kind of important functional material, flexible piezoelectric materials can realize the effective conversion between mechanical energy and electrical energy, with the advantages of good toughness, high plasticity and light weight. Therefore, they can be attached to the human body to obtain human or environment information in real time, which is widely used in the fields of motion detection, health monitoring, and human-computer interaction. Due to high requirements of various three-dimensional (3D) structures of the flexible piezoelectric materials, additive manufacturing has been extensively utilized to fabricate different kinds of piezoelectric materials. This technology is expected to break the bottleneck of traditional processing of piezoelectric material by improving the structural design freedom and the performance of flexible piezoelectric materials, and provides enormous potential and opportunities for the application of flexible piezoelectric materials. Based on the introduction of the classification and features of flexible piezoelectric materials, this paper explained the main additive manufacturing technologies, including fused deposition modeling, direct ink writing, selective laser sintering, electric-assisted direct writing, stereolithography, and inkjet printing that commonly used in processing these materials. Then, various structural designs, such as multi-layer structure, porous structure, and interdigital structure for the flexible piezoelectric materials produced by different additive manufacturing approaches were reviewed. Moreover, the applications of additive manufactured flexible piezoelectric materials in energy harvesting, piezoelectric sensing, human-computer interaction, and bioengineering were introduced. Finally, the challenges faced by additive manufacturing on processing flexible piezoelectric materials and the development trends in the future were summarized and prospected.

Oxide ceramics, known for their outstanding strength and excellent oxidation and corrosion resistance, are prime candidates for high-temperature structural materials of aero-engines. These materials hold vast potential for application in high-end equipment fields of the aerospace industry. Compared with traditional ceramic preparation methods, laser additive manufacturing (LAM) can directly realize the integrated forming from raw powders to high-performance components in one step. LAM stands out for its high forming efficiency and good flexibility, enabling rapid production of large complex structural components with high performance and high precision. Recently, research on LAM for melt-grown oxide ceramics, which involves liquid-solid phase transition, has surged as a hot topic. This paper begins by outlining the basic principles of LAM technology, with an emphasis on the process characteristics of two typical LAM technologies: selective laser melting and laser directed energy deposition. On this basis, the paper summarizes the microstructure characteristics of several different oxide ceramics prepared by LAM and examines how process parameters influence these microstructures. The differences in mechanical properties of laser additive manufactured oxide ceramics with different systems are also summarized. Finally, the existing problems in this field are sorted out and analyzed, and the future development trend is prospected.

Advanced ink printing techniques, such as printing and coating, have overcome the limitations of traditional manufacturing methods, allowing for rapid prototyping of films and electronic devices with sophisticated structures and specific functions. These techniques hold enormous potential in wearable smart identification, energy storage, electromagnetic shielding and absorption, touch display, and so on. The key to printing advanced energy and electronic devices lies in the development of cutting-edge functional inks and their corresponding printing technologies. MXene, a family of two-dimensional compounds composed of transition metal carbides, nitrides, or carbonitrides, was discovered in 2011. MXene exhibits remarkable physical and chemical properties, including high conductivity, pronounced hydrophilicity, and diverse surface chemistry, which has garnered significant attention within the research community and made it particularly suitable as inks in printing applications. Conducting research on the printing behavior and mechanisms of MXene inks is crucial not only for achieving high-precision patterns but also for establishing a solid foundation for manufacturing techniques that can precisely create multiscale, multimaterial and multifunctional films, and electronic devices. This article begins with a brief discussion of MXene flakes’ synthesis and colloidal stability, followed by a detailed examination of its rheological characteristics, printable ink formulation, and printing methods. Additional, special attention is given to the latest advances of MXene ink in energy, health, and sensing applications. The perspective concludes with a summary of current research challenges and future directions in this area, offering new perspectives and insights for researchers.

Al₂O₃-TiC_p (AT) composites are frequently used as materials for metal cutting tools due to their superior mechanical properties. However, conventional sintering methods for AT materials have limitations in terms of energy consumption and cycle time. Therefore, in this study, direct additive manufacturing of AT composite ceramic materials was investigated using laser directed energy deposition technology. Effects of different TiC_p ratios on the microstructure and mechanical properties of composite ceramic materials were explored. The results demonstrate that TiC_p particles are uniformly distributed throughout the matrix of the fabricated samples, leading to refinement of Al₂O₃ grains. Stress induced by mismatch between the thermal expansion coefficients of TiC_p and the Al₂O₃ matrix causes cracks to deflect and penetrates the particles, which consumes the crack extension energy and effectively suppresses the cracks in AT materials. Additionally, doping TiC_p particles affects the molten pool by increasing the gas escape rate and improving the material density. However, high TiC_p content aggravates the reaction with Al₂O₃ at high temperature, resulting in generation of gas and large pores in the composite material, which reduces the mechanical properties. Composites with TiC_p mass fraction of 30% exhibit the best mechanical properties, with a relative density of 96.64%, microhardness and fracture toughness of 21.07 GPa and 4.29 MPa·m^1/2.

Ceramic-based porous structures not only inherit the excellent properties of dense ceramic materials such as high-temperature resistance, electrical insulation, and chemical stability, but also have unique advantages similar to porous structures, including low density, high specific surface area, and low thermal conductivity. They show great potential in various applications, such as thermal insulation, bone tissue engineering, filtration and pollutants removal, and electronic components. However, there still exist some challenges for shaping complex geometries on the macro- scale and adjusting pore morphologies on the micro- and nano-scale through the conventional preparation strategy of ceramic-based porous structures. In recent decades, researchers have been devoting themselves to developing novel manufacturing techniques for ceramic-based porous structures. The direct-ink-writing 3D printing, as one of the representative additive manufacturing technologies, has become a current research hotspot, rapidly developing a series of mature theories and innovative methodologies for fabricating porous structures. In this work, the conventional strategies and additive manufacturing strategies for obtaining porous structures were firstly summarized. The direct-write assembly processes of pore structures were further introduced in detail, mainly including pseudoplastic ink formulation, solidification strategy, drying, and post-treatment. Meanwhile, the feasibility of direct-ink-writing 3D printing technologies combined with conventional manufacturing strategies in constructing ceramic-based hierarchical pore structures was analyzed emphatically. The new perspectives, developments, and discoveries of direct-ink-writing 3D printing technologies were further summarized in the field of manufacturing complex ceramic-based porous structures. In addition, the developments and challenges in the future were prospected according to the actual application status.

Silicon carbide (SiC) ceramics, as a high-performance structural-functional integrated material, are widely used in aerospace, nuclear industry and braking system. However, the conventional fabrication methods can not meet the increasing demands for large-scale and complex-structured SiC ceramics, such as engine nozzles, flaps and turbine blades. Binder jetting (BJ) 3D printing technology can overcome the traditional obstacle and provide a novel manufacturing roadmap. Here, we adopted this technique via SiC particle grading, optimized the particle size ratio based on gradation theory, and studied the influence of BJ printing on properties of SiC green body and as-sintered ceramic. For the particle-graded green body after BJ printing, SiC ceramics with a maximum flexural strength of (16.70±0.53) MPa was obtained after one precursor impregnation and pyrolysis (PIP) treatment, whose flexural strength was improved by 116% as compared with that BJ printed from a median diameter of 20 μm. SiC ceramics were further densified using liquid phase siliconization, with the density, flexural strength, elastic modulus, and fracture toughness reaching (2.655±0.001) g/cm³, (285±30) MPa, (243±12) GPa, and (2.54±0.02) MPa·m^1/2, respectively. XRD results demonstrated that the sintered SiC ceramics were mainly composed of 3C structured-β-SiC. All results show that high-performance SiC ceramic materials are innovatively prepared by an efficient and reliable method, based on the combined techniques of particle grading, BJ printing, PIP and liquid silicon infiltration.

Bioceramic scaffolds with excellent osteogenesis ability and degradation rate exhibit great potential in bone tissue engineering. Akermanite (Ca₂MgSi₂O₇) has attracted much attention due to its good mechanical property, biodegradability and enhanced bone repair ability. Here, akermanite (Ca₂MgSi₂O₇) scaffolds were fabricated by an extrusion-type 3D printing at room temperature and sintering under an inert atmosphere using printing slurry composed of a silicon resin as polymer precursor, and CaCO₃ and MgO as active fillers. Furthermore, the differences in structure, compressive strength, in vitro degradation, and biological properties among akermanite, larnite (Ca₂SiO₄) and forsterite (Mg₂SiO₄) scaffolds were investigated. The results showed that the akermanite scaffold is similar to those of larnite and forsterite in 3D porous structure, and its compressive strength and degradation rate were between those of the larnite and forsterite scaffolds, but it showed a greater ability to stimulate osteogenic gene expression of rabbit bone marrow mesenchymal stem cells (rBMSCs) than both larnite and forsterite scaffolds. Hence, such 3D printed akermanite scaffold possesses great potential for bone tissue engineering.

As an emerging manufacturing technology, additive manufacturing technology, also known as 3D printing technology, has received extensive attention in recent years. Additive manufacturing technology has great potential in the industry of high-performance ceramics. It is expected to break the technical bottle neck of the traditional manufacturing technologies used for ceramic fabrication and greatly improve the flexibility of design and manufacturing of high-performance ceramics. This will provide a transformative impetus for the development of the manufacturing technology of the high-performance ceramic materials. Polymer-derived ceramics (PDCs) are a class of polymers obtained by chemical methods and can be transformed into ceramics by heat treatments, i.e., pyrolysis. Due to the good machinability and formability of the PDC materials themselves, the pre-forming of the designed target structures can be easily realized. These structures might not be possible with traditional ceramic manufacturing. Therefore, the combination of PDCs and additive manufacturing technology has attracted great attention from researchers. This review introduces characteristics of the additive manufacturing technology used for preceramics. Based on that, the present research status, trends and applications are also systematically described and discussed. The challenges and future directions of the additive manufacturing of polymer-derived ceramics are given for the guidance of future development.