Nanotechnologies / Materials
Medical/Healthcare materials, High-temperature materials

Anisotropic control of shape and material properties via metal 3D printing~ A new axis in the creation of high performance metallic devices ~Division of Materials & Manufacturing Science, Graduate School of Engineering
Professor Takayoshi Nakano

https://researchmap.jp/read0013987

Specially Appointed Professor Takuya Ishimoto

https://researchmap.jp/i_taku

Associate Professor Aire Matsugaki

https://researchmap.jp/airaAssistant Professor Ryosuke Ozasa

https://researchmap.jp/ozasa_r

Nanotechnologies / Materials

Abstract
By utilizing a metal 3D printer, Nakano Laboratory has succeeded in controlling the material properties of metallic materials, especially the crystallographic texture (direction and degree of atomicarrangement), in addition to the precise shape control, and has
created many highly functional metallic materials. We have created and commercialized a novel titanium alloy spinal cage basedon our original design concept for rapid induction of high-qualitybone using a unidirectional micro-groove structure on the cellularorder, which can only be realized by utilizing a metal 3D printer.
Furthermore, we have achieved high functionality through material
control in a wide range of materials, from structural materials suchas titanium-, nickel-, and iron-based alloys, to cutting-edge metallic
materials, such as high-entropy alloys.

▍ Significance of the research and Future perspective

The control of “anisotropic shape and material” by 3D printer,
which is made possible by our laboratory, is a 180-degree turnaround in the utilization of 3D printers, which have been focused
only on the functionalization based on shape characteristics. Thecreation of a design strategy based on shape and material anisotropy, which is made possible by 3D printers for the first time, is expected not only to dramatically improve product performance, butalso to revolutionize product design guidelines.

▍ Background & Results
From our research to date, we have realized that it is indispensable for the creation of ultra-high functional materials to express
high-functional properties specifically in the required direction by
imparting anisotropy. Based on the perspective on anisotropy, ourlaboratory is promoting the creation of “Materials Science of Anisotropy” to develop materials expressing ultimate high-functionalproperties and elucidate the mechanism underlining the expression of anisotropy. We recently realized that metal 3D printer is atechnology that is extremely well matched to “anisotropy”.
The precise shape control capability of 3D printers has madeit possible to control the metal surface morphology at the cellularorder. The formation of unidirectional micro-groove structures facilitated the alignment of osteoblasts and successfully induced highlyoriented and highly strengthened bone (Figure 1). This specificstructure has been mounted on a spinal cage, and a nationwide
large-scale clinical trial has started in September 2022, alreadycontributing to improving the health and quality of life of many patients.
On the other hand, the precise tuning of solidification behavior ina fine melt pool has enabled extensive control of crystallographic
orientation (Figure 2). Single crystal exhibits anisotropy in mechanical functions such as Young’s modulus, and the choice of crystallographic orientation allows the selection of varied properties
according to the application, even though they are the single material. In addition, laser scanning with a small periodicity realizes a
micro-lamellar structure consisting of two layers with different crystallographic orientations and creates resistance to slip deformation
at the layer interface, resulting in a significant strengthening.
Thus, the control of anisotropy on the sub-mm and atomic orderachieved by metal 3D printers gives metallic materials new highfunctionality. We will continue to promote research on anisotropy
control by metal 3D printers as a priority issue of our laboratory.

Figure 1. Titanium alloy spinal cage with a micro-groove structure based on theprecise shape control capability of a metal 3D printer. The micro-groove structure induces mechanically integrated high quality bone, resulting in a significant increasein strength at the initial implantation period compared to conventional cages.

Figure 2. Flexible control of crystallographic texture achieved via metal 3D printer,and unusual strengthening by forming a specific lamellar structure (example ofInconel 718). Further strengthening is achieved by changing the resistance to slip
deformation at the layer interface by changing the loading axis.

P a t e n t Japanese Patent Application No. 2022-115147, Japanese Patent No. 6767699
Gokcekaya, Ozkan; Nakano, Takayoshi et al. Acta Materialia. 2021, 212, 116876, doi: 10.1016/j.actamat.2021.116876
Ishimoto, Takuya; Nakano, Takayoshi et al. Additive Manufacturing, 2021, 43, 102004, doi: 10.1016/j.addma.2021.102004
Takase, Aya; Nakano, Takayoshi et al. Additive Manufacturing, 2021, 47, 102257, doi: 10.1016/j.addma.2021.102257
Tr e a t i s eSun, Shi-Hai; Nakano, Takayoshi et al. Additive Manufacturing, 2021, 47, 102329, doi: 10.1016/j.addma.2021.102329
Amano, Hiroki; Nakano, Takayoshi et al. Additive Manufacturing, 2021, 48, 102444, doi: 10.1016/j.addma.2021.102444
Ishimoto, Takuya; Nakano, Takayoshi et al. ISIJ International, 2020, 60, 1758-1764, doi: 10.2355/isijinternational.ISIJINT-2019-744
URL http://www.mat.eng.osaka-u.ac.jp/msp6/nakano/K e y w o r d 3D printer, crystallographic texture, anisotropy