Bioinspired Smart Coating with Superior Tribological Performance

Bioinspired and Multifunctional Tribological Materials for Sliding, Erosive, Machining, and Energy-Absorbing Conditions: A Review

Friction, wear, and the consequent energy dissipation pose significant challenges in systems with moving components, spanning various domains, including nanoelectromechanical systems (NEMS/MEMS) and bio-MEMS (microrobots), hip prostheses (biomaterials), offshore wind and hydro turbines, space vehicles, solar mirrors for photovoltaics, triboelectric generators, etc. Nature-inspired bionic surfaces offer valuable examples of effective texturing strategies, encompassing various geometric and topological approaches tailored to mitigate frictional effects and related functionalities in various scenarios. By employing biomimetic surface modifications, for example, roughness tailoring, multifunctionality of the system can be generated to efficiently reduce friction and wear, enhance load-bearing capacity, improve self-adaptiveness in different environments, improve chemical interactions, facilitate biological interactions, etc. However, the full potential of bioinspired texturing remains untapped due to the limited mechanistic understanding of functional aspects in tribological/biotribological settings. The current review extends to surface engineering and provides a comprehensive and critical assessment of bioinspired texturing that exhibits sustainable synergy between tribology and biology. The successful evolving examples from nature for surface/tribological solutions that can efficiently solve complex tribological problems in both dry and lubricated contact situations are comprehensively discussed. The review encompasses four major wear conditions: sliding, solid-particle erosion, machining or cutting, and impact (energy absorbing). Furthermore, it explores how topographies and their design parameters can provide tailored responses (multifunctionality) under specified tribological conditions. Additionally, an interdisciplinary perspective on the future potential of bioinspired materials and structures with enhanced wear resistance is presented.

Micro-mechanical and tribological behavior of Al/SiC/B4C/CNT hybrid nanocomposite

The aluminum nanocomposite is fabricated through squeeze stir casting method where CNT, SiC/B4C powder has been used as a reinforcement in an aluminum matrix. Squeeze action in stir casting opted due to proper reinforcement of 2 vol% of CNT in the matrix. The boron carbide and silicon carbide have been added by 8 and 12 vol% in the matrix. Uniform distribution of reinforcement and phase analysis has been shown by scanning electron microscopy (SEM) and XRD analysis. The formation of intermetallic compounds like Al3BC and Al4C3, dislocation forests, and the interaction of the reinforcement with the matrix are all confirmed by transmission electron microscopy (TEM). The micro-mechanical behavior of aluminum nanocomposites was investigated using nano indentation. The nano hardness, Vickers hardness, and Young's modulus of 12 vol% B4C compared with 12 vol% of SiC are increased by 12%, 23%, and 16%, respectively, and the same trend has been observed for the 8 vol% B4C reinforced composite. The model analysis for Young's modulus has been done and the experimental value for the modulus of elasticity of the composite are validated and not find such differences significantly. The surface topography was determined, furrow scratches and wear scars, and it was discovered that B4C reinforced composites have reduced stripping pits inside the wear marks, as well as lower wear width and depth. Wear analysis is essential because abrasive encounters result in substantial damage owing to larger pits and bigger wear scars.

Fabricating the cartilage: recent achievements

This review aims to describe the most recent achievements and provide an insight into cartilage engineering and strategies to restore the cartilage defects. Here, we discuss cell types, biomaterials, and biochemical factors applied to form cartilage tissue equivalents and update the status of fabrication techniques, which are used at all stages of engineering the cartilage. The actualized concept to improve the cartilage tissue restoration is based on applying personalized products fabricated using a full cycle platform: a bioprinter, a bioink consisted of ECM-embedded autologous cell aggregates, and a bioreactor. Moreover, in situ platforms can help to skip some steps and enable adjusting the newly formed tissue in the place during the operation. Only some achievements described have passed first stages of clinical translation; nevertheless, the number of their preclinical and clinical trials is expected to grow in the nearest future.

Supramolecular hydrogel-infiltrated ceramics composite coating with combined antibacterial and self-lubricating performance

Inspired by the structure and dynamic weeping lubricating mechanism of articular cartilage, a novel composite coating composed of a textured Y₂O₃-stabilized ZrO₂ (YSZ) ceramics reservoir and silver nanoparticles (AgNPs) hybrid supramolecular hydrogel was developed on the basis of a soft/hard combination strategy. The precursor solution including the poly(ethylene glycol) (PEG)-modified AgNPs and α-cyclodextrins (α-CDs) could be infiltrated deep into (50-60 μm) the pores of a textured YSZ ceramics substrate by a vacuum infiltration method, in situ forming a supramolecular hydrogel within the pores through host-guest inclusion between α-CDs and PEG chains distributed onto the surface of AgNPs. The AgNPs hybrid hydrogel showed thixotropic and thermoresponsive gel-sol transition behavior, low cytotoxicity, and excellent drug-loading capacity, as well as significant antibacterial properties. The textured YSZ ceramics not only provided a hard supporting skeleton and stable reservoir to protect the supramolecular hydrogel from destruction under load-bearing or shear condition, but also allowed retaining the stimuli-responsive gel-sol transition property and drug-release capability of the infiltrated hydrogel, endowing the composite coating with excellent antibacterial properties, and self-lubrication and wear-resistance performance. The composite coating in this work brings a new insight into the design of antibacterial and self-lubricating ceramic coatings for artificial joint applications.

Poly(ethylene oxide)-Li10SnP2S12 Composite Polymer Electrolyte Enables High-Performance All-Solid-State Lithium Sulfur Battery

Composite polymer electrolyte membranes are fabricated by the incorporation of Li₁₀SnP₂S₁₂ into the poly(ethylene oxide) (PEO) matrix using a solution-casting method. The incorporation of Li₁₀SnP₂S₁₂ plays a positive role on Li-ionic conductivity, mechanical property, and interfacial stability of the composite electrolyte and thus significantly enhances the electrochemical performance of the solid-state Li-S battery. The optimal PEO-1%Li₁₀SnP₂S₁₂ electrolyte presents a maximum ionic conductivity of 1.69 × 10^-4 S cm^-1 at 50 °C and the highest mechanical strength. The possible mechanism for the enhanced electrochemical performance and mechanical property is analyzed. The uniform distribution of Li₁₀SnP₂S₁₂ in the PEO matrix inhibits crystallization and weakens the interactions among the PEO chains. The PEO-1%Li₁₀SnP₂S₁₂ electrolyte exhibits lower interfacial resistance and higher interfacial stability with the lithium anode than the pure PEO/LiTFSI electrolyte. The Li-S cell comprising the PEO-1%Li₁₀SnP₂S₁₂ electrolyte exhibits outstanding electrochemical performance with a high discharge capacity (ca. 1000 mA h g^-1), high Coulombic efficiency, and good cycling stability at 60 °C. Most importantly, the PEO-1%Li₁₀SnP₂S₁₂-based cell possesses attractive performance with a high specific capacity (ca. 800 mA h g^-1) and good cycling stability even at 50 °C, whereas the PEO/LiTFSI-based cell cannot be successfully discharged because of the low ionic conductivity and high interfacial resistance of the PEO/LiTFSI electrolyte.