Highly efficient three-dimensional optical condensation of nano- and micro-particles using a gold-coated optical fibre module

Abstract Detecting trace amounts of harmful bacteria and nanoscale biomarkers is essential for early diagnosis and disease prevention. However, conventional methods, such as cultivation and immunoassays, are time-consuming and suffer from limited biological sensitivity. To address these limitations, we developed a rapid and highly sensitive detection method based on optical condensation using a metallic thin-film-coated optical fibre module. Acting as a photothermal source, this module induces convection and bubble formation at the fibre tip, enabling efficient three-dimensional condensation of targets within liquid samples. When positioned away from the substrate, the module assembled 10 3 –10 5 bacteria and microparticles from a 20 μL sample within 60 s. This approach increased assembly efficiency by more than ten-fold compared with conventional two-dimensional photothermal methods, concentrating over 10% of all target objects through combined horizontal and vertical convection. These findings highlight the potential of this technique for advancing bioanalytical detection, drug delivery and material assembly technologies.