Ivory substitute can be 3D printed with extreme precision

Ivory, material from the tusks of elephants and other animals, has been used to make fine ornaments and tools for thousands of years. In an effort to protect elephant populations, the ivory trade was banned internationally in 1989 although an illegal trade in the material remains.

The ban has sparked demand for ivory substitutes to restore ivory artefacts and produce new ivory-like objects. These substitutes include bones, shells, nuts, and synthetic materials such as plastics, although a satisfactory solution has not yet been found.

Scientists from TU Wien worked with TU Wien spin-off 3D-printing company Cubicure to develop a high-tech ivory substitute they named 'Digory'. This material consists of synthetic resin and calcium phosphate particles, which can be 3D printed in the desired shape and then polished and colour matched to create extremely authentic-looking objects.

“The research project began with a valuable 17th-century state casket in the parish church of Mauerbach,” said Professor Jürgen Stampfl, of the university’s Institute of Materials Science and Technology. “It is decorated with small ivory ornaments, some of which have been lost over time. The question was whether they could be replaced with 3D-printing technology.”

The team had some experience with similar materials, having worked with ceramics for dental technology. Nevertheless, developing an ivory substitute was particularly challenging due to the range of requirements that must be fulfilled. “The material should not only look like ivory, the strength and stiffness must also be right, and the material should be machinable,” said Thaddäa Rath, who worked on the project as part of her dissertation.

Rath and her colleagues honed in on a mixture of micro-scale calcium phosphate particles in a special resin, with a very fine silicon oxide powder. The mixture is processed at high heat in Cubicure’s 3D printers using the hot lithography process: the material (in a hot liquid state) is cured layer by layer with a UV laser until the structure is completely formed.

“You have to bear in mind that ivory is translucent,” Rath explained. “Only if you use the right amount of calcium phosphate will the material have the same translucent properties as ivory.” Afterwards, the colour of the object can be touched up (the researchers got good results with tea staining), and the characteristic dark lines running through ivory can be applied with high precision.

The new material is a huge step forwards for art restoration; not only is Digory more beautiful, but it provides an easier material to work with as the finest details can be reproduced by a 3D printer in hours rather than carved by hand.

Konstanze Seidler of Cubicure added: “With our specially developed 3D-printing systems, we process different material formulations for completely different areas of application, but this project was also something new for us. In any case, it is further proof of how diverse the possible applications of stereolithography are.”