Highly lubricative, self-healing, chemically degradable, anti-flaming and anti-irradiating magnetic gels simply prepared from binary mixtures of Fe₃O₄ nanoparticles and water

Aqueous magnetic gels normally fabricated by embedding inorganic magnetic particles into organic hydrophilic polymeric networks have been well-established for various potential applications, but developing their counterparts that barely comprise inorganic magnetic particles and water remains an appealing challenge in light of the underlying preponderances in facile preparation, high safety, eco-friendliness and good stability under strong irradiating conditions. In addition, although aqueous magnetic gels have been exploited for numerous industrial and biomedical purposes, there have been few reports on aqueous magnetic gels for tribological applications. Herein, we illustrate magnetic gels simply prepared from binary mixtures of composite Fe3O4 nanoparticles and water. The aqueous gels can provide ultralow friction and wear for steel/ZrO2 interfaces even under very high load-bearing conditions owing to the tribochemical reactions of the magnetic nano-gelator. They show excellent self-healing capacity either upon alternately changing external shear strains or cutting. Considering the advantages of their organic scaffold-free nature, the gels possess inherent low cytotoxicity, flame retardancy, chemical degradability and irradiation resistance that contribute to minimizing their health risks, safety concerns, environmental burdens and stability issues under harsh conditions. Our study may provide new insights into the design and preparation of novel inorganic-based smart soft materials for nanotechnology, sustainable engineering and colloidal chemistry.