Lecture Hall HCI J6, 16:30
Tatiana Akhmetshina
Laboratory for Metal Physics and Technology, ETH Zürich
Smart Metals in Medicine: Designing Implants that Support and Disappear
Millions of patients undergo secondary surgeries to remove permanent metal implants after fracture healing. Biodegradable magnesium alloys offer temporary support that dissolves safely in the body. Existing systems rely on complex compositions with unclear health impacts and limited understanding of degradation mechanisms. This work presents chemically simple Mg-Ca alloys (< 1 wt.% Ca) that achieve unprecedented mechanical performance while maintaining complete biodegradability. Through advanced processing and innovative 3D nanoscale imaging, we visualized the degradation lifecycle and identified key mechanisms governing material behavior. These alloys demonstrate superior strength-to-composition ratios and controlled degradation compared to current medical-grade materials. This research provides practical guidelines for implant development and new methods to predict long-term performance, accelerating translation of biodegradable metals into clinical applications.
Dragan Damjanovic
Laboratory for Ferroelectrics and Functional Oxides, EPFL
Defects, Symmetry-Breaking and Multi-property Coupling in Complex Materials
Piezoelectricity and pyroelectricity are typically linked to noncentrosymmetric crystal structures, but their thermodynamic definition only requires the macroscopic sample to be noncentrosymmetric or to possess a polar axis. This explains why amorphous electrets can show these effects despite lacking long-range crystalline order. An interesting question is whether materials with long-range centrosymmetric crystal structures can still display piezoelectric or pyroelectric behavior. Thermodynamically the answer is simple, yet such reports remain surprising, especially when the effects are large, suggesting nontrivial mechanisms. Here, we discuss emergent pyroelectricity and piezoelectricity in doped CeO₂ and in various perovskite oxides and halides with nominally centrosymmetric structures. In several cases, the observed polarization originates from inhomogeneous distributions of charged defects, such as oxygen vacancies, whose arrangement can be controlled or switched by external fields. This defect engineering also opens possibilities for multi-property coupling, such as electro-chemo-photo-thermo-mechanical responses, which will be discussed in the talk.