Development of new biomaterials is essential for further advancing implants, prostheses and tissue engineering. New biomaterials can lead to better medical devices, with improved biocompatibility and faster healing. Additionally, the development of new biomaterials drives innovation and creates new market opportunities. One of the main challenges in the field of biomaterials is to find a suitable alloy composition simultaneously fulfilling a
properties:

a) good mechanical properties,

b) high corrosion resistance,

c) long-term tribology behavior,
d) chemical stability in the human body and

e) absence of cytotoxic elements.

One family of materials that are promising in this respect are metallic glasses.

Metallic glasses are non-crystalline multicomponent alloys, i.e. they are solid metals with the structure of a liquid. Within the field of physical metallurgy, metallic glasses show so unique properties utterly different from the conventional crystalline compounds. The mu larger solubility ranges of liquid metals, as compared to intermetallic crystalline phases, makes it possible to tune the composition of metallic glasses without losing chemical homogeneity. In addition, the absence of crystalline orientations and grain boundaries makes these materials homogeneous and isotropic down to the nanometer scale. The high yield stress at room temperature, the possibility of thermoplastic forming near the glass transition region and the recent advent of new metallic glass synthesis methods, such as thin film deposition and additive manufacturing techniques, appoint metallic glasses good candidates to develop new metallic surfaces with highly specific properties. The surface characteristics are of crucial importance in biomedical applications due to the continuous interaction between the surface of the implanted material and the physiological environment in which it is embedded.

In this regard, not only the chemical properties are relevant but also the surface morphology can modulate the biological response. The overall objective of this project is to open a new line of research, between GCM and BBT groups, to develop and characterize new metallic surfaces, with liquid-like atomic scale structure, for biomedical applications. The major challenges to overcome would be, among others: a) to assess the relationship between surface properties and the performance of bioinert and, in some cases, biodegradable metallic glasses, b) to control the degradation process in the case of biodegradable materials, c) to develop porous and nano-designed surfaces and study their effect and d) to enhance the surface bioactivity. a first step, the project will be focused on Ti-Zr and Mg-Ca metallic glass-forming alloys.

The synthesis of the materials will be performed in the GCM laboratory and in collaboration with international groups. The surface characterization of physical, chemical and mechanical properties will profit from the CCEM facilities (XPS, AFM, Nanoindentatio Corrosion testing) and the biocompatibility and the interaction behavior with biological systems will be characterized in the BBT laboratory. Synthesis of the samples will be performed by standard casting methods, rapid
solidification methods and thin film deposition. Surface treatments will be applied surface nano-structuring. XPS experiments will be carried out to study the chemical surface state. Ion release experiments will be performed in water solutions to study the dissolution behavior of these materials. Electrochemical techniques (e.g. cyclic voltammetry, electrochemical impedance spectroscopy, potentiostatic and corrosion experiments) will be used to study their oxidation/reduction behavior and corrosion. Mechanical and micromechanical characterization by standard mechanical testing and nanoindentation will also be used, combined with high-resolution STEM imaging. Additionally, biological studies will characterize the in vitro biocompatibility of the alloys for selected cell lines.

It is expected that the know-how obtained during this research project, about the development and characterization of new metallic surfaces, will be also useful in other fiel of interest for the CCEM like, for instance, the development of new anode materials for lithium batteries and the synthesis of new metallic disordered materials for heterogeneous catalysis and electrocatalysis. These already ongoing research projects will complement synergistically with this project in terms of key characterization and synthesis techniques, hopefully building a strong research line in the development and application of new, nanostructured metallic surfaces.