There has been a significant progress in the field of biotribology and material design for biomedical devices. However, the challenges remain in ensuring effective interaction with the human body. Advanced materials offer benefits like biocompatibility and antimicrobial properties, and are used as coatings, composite fillers, or fluid additives to improve strength and wear resistance. However, each application method involves its unique challenges, such as interface issues with fillers, wear concerns with coatings, and potential toxicity from fluid additives. Hence further innovation is needed to overcome these limitations and optimize device performance.
Graphene based materials
Graphene-based materials, especially graphene oxide (GO) and reduced graphene oxide (rGO), are gaining attention in biotribology for their exceptional wear resistance and low friction. GO can reduce wear by up to 48% compared to traditional materials and shows a very low coefficient of friction (COF) under dry conditions. With a Young’s modulus of up to 1 TPa, graphene is ideal for load-bearing applications. However, differences in oxidation and surface functionalization affect biocompatibility and tribological performance, leading to varied results across studies.
The improved tribological properties of graphene-based materials stem from their layered structure, which enables easy interlayer sliding and reduces friction and wear. Graphene coatings on metal implants can decrease wear by up to 50%. However, achieving uniform distribution and strong adhesion of graphene fillers in composites remains a challenge, affecting their overall mechanical strength and wear resistance.
Molybdenum disulphide and tungsten disulphide
Molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) are effective solid lubricants in biomedical applications due to their layered structures, which enable low friction and high wear resistance. MoS₂ has a COF between 0.02 and 0.05, while WS₂ can achieve COFs as low as 0.03. Both materials offer strong load-bearing capabilities, with MoS₂ films enduring pressures up to 1.5 GPa. However, their long-term biocompatibility and stability in the body require further investigation.
Hydrogels
Hydrogels, particularly poly (vinyl alcohol) (PVA)-based types, are effective in reducing friction and wear between joint surfaces, acting as lubricants with controlled-release properties. They can achieve extremely low COF (as low as 0.005) and reduce wear by up to 80% compared to traditional materials. Hydrogels also exhibit beneficial traits like self-healing and minimal immune response to wear debris. However, challenges include mechanical weakening due to swelling under load and increased wear (up to 25%) in poor lubrication conditions, highlighting the need for further optimization for long-term joint replacement use.
ultra-high molecular weight polyethylene
Ultra-high molecular weight polyethylene (UHMWPE) significantly enhances its biotribological performance when incorporated with vitamin E. Both blending and diffusion methods have been shown to reduce wear by over 90% and greatly improve oxidative stability. Studies report substantial reductions in wear rates, coefficients of friction (up to 88%), and subsurface crack propagation. Vitamin E acts as a free radical scavenger, increasing implant longevity by at least 40% and enhancing mechanical strength without compromising wear resistance. These innovations establish vitamin E-infused UHMWPE as a promising next-generation material for durable, high-performance biomedical implants.
Future biotribology research should prioritize replicating natural bodily conditions and developing cost-effective, patient-specific medical devices, especially for younger, active individuals. Innovations like in vitro testing platforms, 3D bioprinted tissues, and computational models using FEA and machine learning are enhancing predictions of wear and improving implant design. Understanding in vivo lubrication through biphasic models and joint simulators is key to improving implant durability. Advanced materials such as PVA-hybrid gels, ECM scaffolds, and coatings like DLC are promising for reducing wear and enhancing performance. Ongoing research into novel materials like vitamin E-infused UHMWPE, black phosphorus, and MXenes, is essential for the future of biotribological advancements.
