UT Austin Researchers Create Functional, 3D Printed Knee Joint

This summer, the University of Texas at Austin published an exciting innovation in 3D printing, which has the potential to revolutionize the next generation of medical devices and flexible electronics. Researchers at the university, funded by the US Department of Defense, the National Science Foundation and the Robert A. Welch Foundation, have developed an innovative method which, inspired by a combination of natural materials such as bone and cartilage, enables hard and soft structures to be seamlessly integrated into a single printed object. This has made it possible to create a fully functional knee joint mini-model from a 3D printer.

The new 3D printing method does not use traditional filament, but a special liquid resin that reacts to two light pulses. Ultraviolet light produces hard, plastic-like sections in the hardening process, while violet light produces elastic, rubber-like areas. In this way, transitions from hard to soft can be achieved within a single component.

The artificial knee joint was the researchers’ first attempt to apply the method in practice.

Chemically cross-linked molecules prevent contact points from breaking or becoming structurally weak. As Zak Page, assistant professor at UT Austin, explains: “We built in a molecule with both reactive groups so our two solidification reactions could ‘talk to each other’ at the interface. That gives us a much stronger connection between the soft and hard parts, and there can be a gradual transition if we want.”