Maïté Croonenborghs
PhD student
Ir. at UCL in 2017

Main project: Influence of defects on the life of biomedical implants
Funding: UCL Assistant
Supervisor(s): Pascal Jacques, Thomas Pardoen

Implants are devices aiming to support, help, or even correct biological structures. However, with time, some of these implants show aging problems. The roots of these problems can have numerous explanations. In some cases, the body reacts to the presence of a foreign body, and this can lead to health risks. Sometimes, the material can show, with time, signs of weakness. Later on, these defects can lead to the failure of the implant.

In the case of permanent stent implants, the presence of a foreign body in the blood vessels can lead to restenosis or late thrombosis. This is why bioresorbable stents are nowadays developed. These stents should support the vessels during their healing period and dissolve in an inoffensive way afterward. Iron-based alloys are investigated for their appropriate mechanical properties but their degradation rate is too low. One investigated solution is to increase surface roughness to dissolve faster the implant. The effect of this roughness on the expansion process has not been analyzed for now.

The case of growth rods shows that the material itself can lead to implant failure. These rods are placed, during surgery, along the spine of scoliotic children. They aim to support the spine and help it to straighten back. However, fracture events occur in 36% of the patients. During the surgery, the rods are bent to fit the natural shape of the spine. The tools employed for this process can introduce some indentation marks on the surface of the rods and decrease their fatigue lifetime.

From these case studies, it is observed that the completion of an implant (i.e. stent implantation process) or its lifetime (i.e. growth rod failure) can be affected by its surface state. This research will therefore focus on the imperfection sensitiveness of such devices. Various kinds of defects are introduced at the sample surface. To understand the influence of these defects on the mechanical properties, these samples are tested and compared.

IMMC main research direction(s):
Processing and characterisation of materials

medical device
metallic alloys

Research group(s): IMAP