A hybrid meta-biomaterial that promotes bone growth is not something you will find in nature, but it can be created using a 3-D printer and existing biomaterials. TU Delft researchers have developed a meta-implant that combines a conventional meta-biomaterial with an auxetic meta-biomaterial. Unlike natural materials, auxetics have a negative Poisson’s ratio—when stretched, they become thicker perpendicular to the applied force. The material may, therefore, be used in hip implants to ensure their long-term fixation. The TU Delft researchers published their findings in the scientific journal Materials Horizons on 2 January 2018.
Meta-biomaterials are the biomedical variant of so-called metamaterials, materials that display characteristics that are not found in nature. In their publication, Zadpoor and his colleagues outline the immense potential of metamaterials in the development of medical implants. “Auxetic meta-biomaterial, designed using simple geometry and printed in titanium, displays the unique mechanical property of expanding when put under pressure. This makes it ideal for use alongside materials that do the opposite,” explains Zadpoor. “When someone with a hip implant walks, the prosthesis is subjected to various forces. If too much pressure develops on one side of the prosthesis, it can become detached from the bone, which is extremely undesirable.”
The researchers believe that a hybrid prosthesis made of meta-biomaterials with a positive Poisson’s ratio and those with a negative Poisson’s ratio will become much more fixated in the body. “This will significantly improve the chances of bone growth onto the hybrid meta-biomaterials, holding the implant much more securely in place.” Zadpoor also thinks that he will be able to use this new material in the future to address the most significant cause of implant loosening. “Since there will be fewer unnatural forces at work on the prosthesis, there is a smaller chance of plastic particles wearing off in the hip cup, which can increase the risk of loosening.”