Enhancing LIBS detection of oil-borne metallic microparticles via acoustic manipulation chip-based enrichment.

Metallic wear debris in lubricating oils can reflect abnormal wear conditions in rotating machinery, and the rapid analysis of chemical elements in wear particles can timely predict the exact fault positions, thereby enabling ordinary operation and maintenance support in diverse industrial applications. Emerging as a quick and convenient analytical tool, laser-induced breakdown spectroscopy (LIBS) is promising for directly detecting oil-borne metallic microparticles. However, its efficiency has been greatly hindered by the low concentration of micrometric particles sparsely distributed in the oil matrix. Here, we present an acoustic manipulation strategy for enhancing the LIBS detection of oil-borne metallic microparticles. A sandwich-type configuration was selected to build the acoustic manipulation chip with dual parallelized serpentine microchannels, and the acoustic radiation force dominates the quick enrichment of randomly distributed metallic particles. With increased particle concentration, the LIBS spectral intensity was significantly enhanced for 3 typical elements (Fe, Cu, and Ni). The experimental results illustrated that the large background noise interference from the oil matrix was effectively suppressed, and the metallic elements after enrichment could be accurately recognized. The proposed acoustic enrichment method lays a solid foundation for enhancing the LIBS detection of oil-borne metallic particles, offering a new alternative for quick fault diagnosis and in-time health management of mechanical rotating systems in practical applications.