How do you turn salt and magnesium (left) into a bone implant with regularly...
How do you turn salt and magnesium (left) into a bone implant with regularly structured pores (right)? ETH researchers developed a method using a template of 3D-printed salt (centre).
Source: Laboratory of Metal Physics and Technology / Complex Materials / ETH Zurich)

3D printed salt template for bone implants

With the help of a 3D printed salt template, researchers have succeeded in producing magnesium scaffolds with structured porosity that are suitable for bioresorbable bone implants.

For the treatment of complex bone fractures or even missing bone parts, surgeons typically deploy metal implants. In this context, an attractive alternative to the traditional materials like bioinert titanium are biodegradable magnesium and its alloys. Implants made of the latter light metal are advantageous because they can biodegrade in the body, which can absorb magnesium as a mineral nutrient, rendering a second surgery for implant removal unnecessary. To promote rapid healing, the design of implants or their surfaces should be directed towards promotion of cellular adhesion or even in-growth. Materials researchers from the Laboratory of Metal Physics and Technology and the Complex Materials Group at ETH Zurich have therefore collaborated to develop a new procedure for the manufacture of magnesium implants that contain numerous structurally ordered pores but still retain their mechanical stability.

To create a porous structure the researchers first printed a three-dimensional salt template using a 3D printer. Because pure, standard table salt is not suitable for printing, they developed a gel-like salt paste for this purpose. The strut diameters and spacings of the salt template can be tailored by the printing process. To gain sufficient mechanical strength the salt structure was subsequently sintered. During sintering the fine-grained materials are heated significantly, while the temperature is chosen safely below the paste’s melting point to retain the structure of the workpiece.

The next step was to infiltrate the pores with magnesium melt. “The infiltrates obtained in this way are mechanically very stable and can be easily polished, turned and shaped,” says Jörg Löffler, Professor of Metal Physics and Technology in the Department of Materials. After mechanical shaping the researchers dissolved the salt, leaving a pure magnesium implant with numerous, regularly structured pores.

3D-printed salt template (left, scale: 1 mm), into which in a further step...
3D-printed salt template (left, scale: 1 mm), into which in a further step magnesium melt is infiltrated. After leaching of the salt, magnesium with regularly arranged pores remains (r.).
Source: Laboratory of Metal Physics and Technology / Complex Materials / ETH Zurich)

Decisive for clinical success

“The possibility to control the pore size, distribution and orientation in the material is decisive for clinical success, because bone cells like to grow into these pores,” says Löffler. Growth into pores is in turn decisive for the rapid integration of the implant in bone.

The new procedure for manufacturing these template structures from salt can be applied to other materials besides magnesium. Co-authors Martina Cihova and Dr Kunal Masania expect that the process can also be used to tailor pore geometries in polymers, ceramics and other light metals.

The idea of this new manufacturing procedure emerged within the framework of the Master’s thesis of Nicole Kleger, whose study was supported by an ETH Zurich Excellence Scholarship & Opportunity stipend. Her work was also awarded with the ETH medal for excellent Master’s theses. Nicole Kleger is now a doctoral student in the Complex Materials Group of ETH professor André Studart, under whose direction the initial salt template was 3D printed. In her doctoral thesis project Kleger is now developing the 3D printing procedure further.

Subscribe to our newsletter

Related articles

Aerogel: the micro structural material of the future

Aerogel: the micro structural material of the future

In a research-first, scientists from Empa were able to 3D print stable well-shaped microstructures made from silica aerogels for use in biotechnology and precision engineering.

Machine learning speeds up bioscaffold development

Machine learning speeds up bioscaffold development

A dose of artificial intelligence can speed the development of 3D-printed bioscaffolds that help injuries heal.

A 3D printed device to excite nerves

A 3D printed device to excite nerves

A tiny, thin-film electrode with a 3D-printed housing has been implanted in the peripheral nervous system of songbirds, where it successfully recorded electrical impulses that drive vocalizations.

An universal carrier ink for 3D printing

An universal carrier ink for 3D printing

Researchers have produced a gel from cellulose fibres and biodegradable nanoparticles that liquifies when pressed through the nozzle of a 3D printer, but then quickly returns to its original shape.

3D printable biomaterial for personalised medicine

3D printable biomaterial for personalised medicine

Marc Knebel, head of Medical Systems at Evonik, explains the benefits and applications of the new high-performance polymer VESTAKEEP Care M40 3DF.

Insulin-producing implant for diabetics

Insulin-producing implant for diabetics

Bioengineers are using 3D printing and smart biomaterials to create an insulin-producing implant for type 1 diabetes patients.

3D printed knee implant for arthritis sufferers

3D printed knee implant for arthritis sufferers

A groundbreaking new treatment that uses 3D printed implants and that could bring relief to tens of thousands of knee osteoarthritis sufferers has received approval to be trialled in UK patients.

Controlling the performance of 3D printed implants

Controlling the performance of 3D printed implants

In order to quickly customize implants with complex structures, scientists use 3D printing technology to prepare Ti-Mo alloy implants, and then adjust the microstructure and performance through subsequent heat treatment.

Medical technologies that come out of the printer

Medical technologies that come out of the printer

Fraunhofer-Gesellschaft's German-Polish High-Performance Center brings additive manufacturing to medical technology – first demonstrators will already be presented by the end of 2021.

Popular articles

Subscribe to Newsletter