The scaffold for tissue engineering not only requires good biocompatibility, mechanical properties, and appropriate structure, but also should actively participate in biophysical and biochemical processes to accelerate tissue repair. A piezoelectric scaffold can generate electrical activity when deformed, which constructs an electrochemical microenvironment for inducing cell signaling pathways and facilitating tissue regeneration, attracting extensive attention in tissue engineering. Herein, piezoelectric materials used in tissue engineering, including piezoelectric ceramics, synthetic piezoelectric polymers, and natural biological piezoelectric materials are systematically summarized, and their advantages and limitations are analyzed. As for the piezoelectric scaffold, the piezoelectric properties mainly stem from the asymmetric crystal structure of materials and the directional arrangement of internal dipoles, which is highly dependent on the fabrication and post-treatment strategies. Therefore, the fabrication techniques of piezoelectric scaffold are detailly introduced, covering both traditional fabrication techniques and additive manufacturing techniques. Besides, rational structural design of the piezoelectric scaffold can alter strain transmission pathways and charge distribution, or add new operational modes to regulate piezoelectric properties. Thereby, the piezoelectric metamaterials, micro/nanostructures, porous structures, heterogeneous structures, and biomimetic structures are comprehensively summarized. Additionally, the functions of piezoelectric scaffold for tissue engineering application in terms of bone regeneration, neural regeneration, antibacterial activity, and intelligent sensing are reviewed. Finally, the challenges and future research directions of the piezoelectric scaffold are discussed.

Magnesium (Mg) alloys have gained recognition as revolutionary biomaterials, owing to their inherent degradability, favorable biocompatibility and mechanical properties. Additive manufacturing (AM) provides high design flexibility and enables the creation of implants with personalized complex shapes and internal porous structures tailored to individual anatomical and functional needs. Particularly, laser powder bed fusion (LPBF), one prevalent AM technique, utilizes a fine laser beam as heat source and results in tiny molten pool with extremely fast cooling rate, which effectively restricts grain growth, inter-metallic precipitation and macroscopic segregation, thus facilitating the fabrication of high-performance metal parts. This review critically assesses the significance of biodegradable Mg alloys and investigates the feasibility of utilizing LPBF for Mg alloys applications in biomedical field. Detailed discussions on LPBF-processed biomedical Mg alloys parts cover process parameters, microstructure, metallurgical defects, and properties like mechanical performance, corrosion behavior, and biological response in both as-built and post-processed states. Additionally, suggestions for advancing knowledge in LPBF of biodegradable Mg alloys for biomedical applications are highlighted to propel further research and development in this field.

Four-dimensional (4D) printing is regarded as a methodology that links 3D printing to time, which is characterized by the evolution of predetermined structures or functions for the printed object after applying stimulation. This dynamic feature endows 4D printing the potential to be intelligent, attracting wide attention from academia and industry. The transformation of shape and function is both obtained from the programming of the object endowed by the intrinsic characteristics of the material or by the manufacturing technology. Therefore, it is necessary to understand 4D printing from the perspective of both mechanism and manufacturing. Here, the state-of-the-art 4D printing polymer was summarized, beginning with the classifications, and leading to the mechanisms, stimulations, and technologies. The links and differences between 4D printing polymer and shape memory polymer, between 4D printing and 3D printing were highlighted. Finally, the biomedical applications were outlined and the perspectives were discussed.

Magnesium (Mg) alloys are considered to be a new generation of revolutionary medical metals. Laser-beam powder bed fusion (PBF-LB) is suitable for fabricating metal implants with personalized and complicated structures. However, the as-built part usually exhibits undesirable microstructure and unsatisfactory performance. In this work, WE43 parts were firstly fabricated by PBF-LB and then subjected to heat treatment. Although a high densification rate of 99.91% was achieved using suitable processes, the as-built parts exhibited anisotropic and layered microstructure with heterogeneously precipitated Nd-rich intermetallic. After heat treatment, fine and nano-scaled Mg₂₄Y₅ particles were precipitated. Meanwhile, the α-Mg grains underwent recrystallization and turned coarsened slightly, which effectively weakened the texture intensity and reduced the anisotropy. As a consequence, the yield strength and ultimate tensile strength were significantly improved to (250.2 ± 3.5) MPa and (312 ± 3.7) MPa, respectively, while the elongation was still maintained at a high level of 15.2%. Furthermore, the homogenized microstructure reduced the tendency of localized corrosion and favored the development of uniform passivation film. Thus, the degradation rate of WE43 parts was decreased by an order of magnitude. Besides, in-vitro cell experiments proved their favorable biocompatibility.

Biodegradable magnesium (Mg) and its alloy show huge potential as temporary bone substitute due to the favorable biocompatibility and mechanical compatibility. However, one issue deserves attention is the too fast degradation. In this work, mesoporous bioglass (MBG) with high pore volume (0.59 cc/g) and huge specific surface area (110.78 m²/g) was synthesized using improved sol-gel method, and introduced into Mg-based composite via laser additive manufacturing. Immersion tests showed that the incorporated MBG served as powerful adsorption sites, which promoted the in-situ deposition of apatite by successively adsorbing Ca²⁺ and HPO₄²⁻. Such dense apatite film acted as an efficient protection layer and enhanced the corrosion resistance of Mg matrix, which was proved by the electrochemical impedance spectroscopy measurements. Thereby, Mg based composite showed a significantly decreased degradation rate of 0.31 mm/year. Furthermore, MBG also improved the mechanical properties as well as cell behavior. This work highlighted the advantages of MBG in the fabrication of Mg-based implant with enhanced overall performance for orthopedic application.