Tribological behavior of bioactive multi-material structures targeting orthopedic applications

Infinite Approaching Superlubricity by Three-Dimensional Printed Structures

The rapid development of three-dimensional (3D) printing technology opens great opportunities for the design of various multiscale lubrication structures. 3D printing allows high customization of arbitrary complex structures and rapid prototyping of objects, which provides an avenue to achieve effective lubrication. Current experimental observations on superlubricity are limited to atomically smooth clean surfaces, extreme operating conditions, and nano- or microscales. With the in-depth exploration of 3D printed lubrication, construction of multifunctional 3D structures with refined dimensions spanning from micronanoscale to macroscale is increasingly regarded as an important means to approach superlubricity and has aroused great scientific interest. To document recent advances in 3D printing for structural lubrication, a detailed literature review is provided. Emphasis is given on the design and lubrication performance of geometric and bioinspired lubrication structures with characteristic dimensions. The material requirements, merits, drawbacks, and representative applications of various 3D printing techniques are summarized. Potential future research trends aiming at the design strategy and manufacturing process of 3D printed lubrication structures are also highlighted.

Performance analysis of grafted poly (2-methacryloyloxyethyl phosphorylcholine) on additively manufactured titanium substrate for hip implant applications

The incidence of total hip arthroplasty (THA) has been evidently growing over the last few decades. Surface modification, such as polymer grafting onto implant surfaces using poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC), has been gaining attention due to its excellent biocompatibility and high lubricity behaviour resulting in reducing surgical recurrence number and increasing implant lifetime. Investigating thermal stability and mechanical properties of the grafted polymer is, therefore, extremely important as these properties define the failure mechanism of implants. This study focuses on optimising monomer concentration to achieve the best physical, thermal and mechanical properties of the grafted additively manufactured titanium (Ti6Al4V) implants. Three different concentration of monomers, 0.4 M, 0.6 M and 0.8 M, were investigated, and grafted implants were characterised. The results from thermal analysis confirmed that the PMPC polymer is thermally stable for implant applications regardless of the monomer concentrations. A significant reduction in Young's modulus of polymer grafted samples (33.2-42.9%), in comparison with untreated Ti6Al4V samples and consequent improvement of wear resistance and elasticity behaviour, proved the potentiality of polymer films for implant applications. In summary, polymer grafted implant prepared with 0.6 M monomer concentration showed the optimal thermal, physical and wear resistance properties.