Construction of hydroxyapatite bioceramics with biomimetic structures by weak magnetic field-assisted 3D printing

Hydroxyapatite (HA) is a primary inorganic component of hard tissues, such as bone and teeth, and is widely used in repairing bone defects, but it not suitable for load-bearing implants due to poor mechanical performance, particularly insufficient fracture toughness. And achieving a balance of high strength and toughness in ceramics presents a significant challenge.

Many organisms exhibit remarkable properties, such as nacre, bones, and carapaces, which demonstrate exceptional mechanical attributes due to their unique hierarchical structures evolved over time. This indicates that strong and tough biomimetic ceramics may be engineered by mimicking these natural structures. Inspired by oriented and Bouligand structures in natural organisms, a research team from Shaanxi University of Science and Technology developed a weak magnetic field-assisted direct ink writing 3D printer capable of orienting particles with high aspect ratio in high-viscosity ceramic slurry and constructed biomimetic HA bioceramics with fine microstructures at nanoscale and microscale to enhance the mechanical properties by the printer. The printed biomimetic HA bioceramics under low magnetic field strengths (58 mT - 116 mT) possess balanced strength and toughness.

The team published their work in Journal of Advanced Ceramics on August 1, 2025.

“In this work, we designed and manufactured a magnetic field-assisted direct ink writing 3D printer capable of orienting particles with high aspect ratio in high-viscosity ceramic slurry. The particles are aligned to form oriented structures under weak magnetic field strengths (58 mT - 116 mT). The orientation effects in printed rods can be adjusted by varying magnetic field strengths, and the tunable microstructure can be optimized by adjusting 3D printing parameters to achieve specific performance in the oriented ceramics. We also have successfully fabricated bioceramics with biomimetic structures exhibiting significantly enhanced mechanical properties. ” said Xueni Zhao, professor at College of Mechanical and Electrical Engineering of Shaanxi University of Science and Technology (China).

“The oriented HA bioceramics demonstrate a compressive strength of 93.4 MPa along the printing direction, which is 2.3 times that of non-oriented HA ceramics. The bending strength in the thickness direction is 2.6 times that of non-oriented HA bioceramics, whereas the fracture toughness is 1.44 times that of non-oriented counterparts. The compressive strength, bending strength, and fracture toughness of the Bouligand structural HA bioceramics are 2.6 times, 2.8 times, and 1.2 times, respectively, those of non-oriented HA bioceramics, with observed pseudoplastic deformation during compression. The pseudoplastic deformation is significantly greater than those of ordinary ceramics and could suggest an enhancement in toughness.” said Xueni Zhao.

“Next, the relationship between grains, grain magnetism and magnetic field, and the relationship between microstructure and mechanical properties will also be further investigated. A toughening phase, such as a secondary carbon fiber, bioglass, Fe-Zn alloy, and polymer, are being incorporated in HA system with biomimetic structures to further improve mechanical properties and broaden the material's functional scope. The bioinspired architectures can possess excellent mechanical property and biological performance by incorporating different toughening phases. We aim to simply and efficiently prepare bioceramics with controllable microstructure and excellent mechanical and biological properties which will be applied for bone graft substitute and machining internal fixation devices. Additionally, ceramics, metal, ploymer based composites with biomimetic Structures can be readily and rapidly constructed by the weak magnetic field-assisted 3D printing, laying a foundation for the 3D printing of biomimetic materials with fine microstructure and tunable mechanical properties.” said Xueni Zhao.

Other contributors include Yanyu Guo and Jinxin Guan from College of Mechanical and Electrical Engineering at Shaanxi University of Science and Technology (China).

This work was supported by the National Natural Science Foundation of China (Nos. 52472285 and 51772179), Science and Technology Innovation Team of Shaanxi Province, China (No. 2023-CX-TD-16), Key Research and Development Program of Shaanxi Province, China (No. 2024GX-YBXM-171).

About author

Xueni Zhao holds a BSc from Beijing University of Science and Technology in 1996 and Ph.D. in Northwestern Polytechnical University in 2012. She has visited and studied in the University of Brighton for three months and in Pennsylvania State University for one year. She is the head of the Shaanxi Province Innovation Team and the Young Innovation Team of Shaanxi Universities. She seved as the council member of the Shaanxi Mechanical Engineering Society and member of Additive Manufacturing Industry Technology Innovation Alliance of Shaanxi Province. Her current interests and fields of research are 3D printing technology and equipment, biologically-inspired manufacturing technology and applications, biomaterials and devices, advanced composites forming technology and industrialization. She has published more than 100 papers in peer-reviewed international journals. More than 50 invention patents have been applied. As the first inventor, 24 Chinese invention patents and 1 US invention patent have been authorized. As a sole auhtor, the book Theory and Technology for Preparation of Hydroxyapatite-Based Artificial Bones was published in 2021.

About Journal of Advanced Ceramics

Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen. JAC’s 2024 IF is 16.6, ranking in Top 1 (1/33, Q1) among all journals in “Materials Science, Ceramics” category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508