Lipophilic carbon quantum dots enable fluorescence-traceable lubricant release and tribofilm formation in self-lubricating fabric composites

Lubricant delivery and transfer-film formation govern friction and wear in enclosed sliding contacts, yet these buried interfacial processes are difficult to monitor. Oil-loaded microcapsules can supply lubricants to self-lubricating fabric composite liners, but their release behavior is usually optically silent. Here, we report an optically self-reporting microcapsule strategy for AF/PTFE fabric composites, in which dodecyl-chain-modified carbon quantum dots (CQDs-C₁₂) were dispersed in PAO4 and encapsulated in SiO₂ microcapsules as fluorescent lubricant reservoirs. During ball-on-disk sliding, local contact stresses triggered the release of CQDs-C₁₂/PAO4 into the wear track. The normalized integrated fluorescence area provided a semi-quantitative optical indication of the cumulative release and accumulation of the fluorescent lubricant phase. The optimized CD–MCs /Fabric achieved a friction coefficient of 0.085 and a wear volume of 1.03 × 10^-10 m³, which were 61.7% and 44.5% lower than those of Pure Fabric, respectively. SEM/EDS, Raman, XPS and cross-sectional FIB-TEM analyses confirmed the formation of a continuous multi-component tribofilm on the steel counterpart, which reduced direct fabric/steel contact and interfacial shear. This work couples optical release reporting with tribofilm-mediated lubrication, providing a route toward observable self-lubricating fabric composites for enclosed sliding contacts.