Why does an artificial joint replacement wear out within a few years, while human cartilage lasts a lifetime? This is precisely the question research teams around the world are trying to answer, including scientists from the Faculty of Mechanical Engineering BUT. In the field of biotribology, they connect engineering with medicine and seek to understand the processes of friction and wear in living organisms. The interdisciplinary nature of the field has also attracted Daniel Němeček, who received the Brno Ph.D. Talent award for his research and also succeeded in the Werner von Siemens Award.

“I didn’t want to do purely mechanical engineering; I was drawn to something with overlap. Biotribology is a step from engineering into medicine,” says doctoral student Daniel Němeček from the Institute of Machine and Industrial Design, who has been involved in the field since his bachelor’s studies. At that time, he tested hip replacements with textured surfaces; later, he moved on to hydrogels, which aim to mimic natural cartilage.

“A hydrogel is a water-based material, and cartilage is also largely composed of water, so we try to imitate it. In terms of friction, we are able to achieve very similar values with hydrogels as with cartilage, but the key issue is their strength and wear. A hydrogel can be damaged in a very short time, whereas cartilage functions for decades,” explains Němeček.

This very disparity is one of the major unknowns of current research. “At first glance, the materials behave similarly, but they differ in key properties. I would like to know what we are missing—what the crucial mechanism is,” reflects Němeček.

Research into joint implants, which biotribologists at BUT are engaged in, certainly does not end with a single type of material. Several research directions are running in parallel—from possible surface treatments of implants, through the aforementioned hydrogels, to the use of so-called 2D nanomaterials, which have the potential to significantly reduce both friction and wear. “A 2D material can be imagined as a thin sheet of paper, but fifty to one hundred thousand times smaller. If it can be appropriately incorporated into metal replacements, it may fundamentally change their properties and significantly extend the lifespan of implants,” explains Němeček’s supervisor, David Nečas.

It is precisely the research on 2D materials that is linked to a project of the Czech Science Foundation, led by Nečas, which also includes Němeček’s dissertation and his Brno Ph.D. Talent project. The motivation is clear: current joint replacements have a limited lifespan, and some patients require revision surgery. “An implant lasts on the order of ten to twenty years. Approximately five to ten percent of all major joint surgeries are therefore revision procedures. These are more demanding, more expensive, and represent a significant burden for patients, both psychologically and physically,” says Nečas.

The topic is truly global in scope. Millions of hip and knee replacements are performed worldwide every year. As the population continues to age, their number will grow further, with another significant increase expected thanks to increasingly accessible healthcare in countries such as India and China. “In the relatively near future, this could amount to tens of millions of operations annually. Any improvement in implant lifespan therefore has an enormous global impact,” Nečas points out.

In his work, David Nečas follows what he learned during his own doctoral studies: science is about collaboration—ideally international. This is why, this spring, in cooperation with colleagues from Imperial College London, TU Wien, Leibniz University Hannover, and industrial partners, he prepared a Horizon Europe project. “If we want to be among the best, we must collaborate with the best. This project focuses not only on research but also on team development and support for young scientists,” explains Nečas. It is set to include internships, workshops, and intensive exchange of experience.

For Daniel Němeček, this international dimension, together with interdisciplinarity, is one of the main motivations for pursuing doctoral studies. If the project succeeds, he will have the opportunity to collaborate with leading experts in his field. He is therefore hoping for a positive outcome. “I enjoy meeting inspiring people. I wouldn’t want to be confined only to an office or a laboratory,” says the Brno Ph.D. Talent award holder, who sees the recognition as confirmation that he is on the right path. “It’s encouragement that what I do makes sense.”

In addition to research into new materials, the researchers are also addressing more general tribological questions. One of them is so-called superlubricity—a state of extremely low friction—in joints as well as in machines. “In laboratory conditions, we can already achieve it today. The greatest challenge is to transfer these findings from the micro world to the macro world. There is enormous potential here as well, because according to estimates, up to a quarter of all produced energy is lost precisely due to friction and wear. If we could achieve superlubricity in machines, we as a planet would become significantly more efficient in our use of energy,” concludes Nečas.

(ivu)