On-Chip Light-Scattering Enhancement Enabled by a Microlens Array for High-Performance Single-Particle Tracking under Conventional Bright-Field Microscopy.

Scattering-based single-particle tracking (S-SPT) has revolutionized the label-free detection and characterization of nanoscopic objects, offering immense potential for diverse analytical applications. However, the high technical demands placed on optical systems have long impeded its widespread adoption. To address this, an on-chip microlens-based approach that significantly enhances light scattering, thereby reducing the requirements on back-end optical systems, is introduced. Unlike existing field enhancement techniques, which are limited by their highly localized field, this approach leverages enhanced long-range optical fields and complex interactions between nanoparticles and the microlens to achieve an enhancement range ten times greater. This method enables high-performance S-SPT using a conventional bright-field microscope under incoherent light sources with relatively low illumination powers. The approach achieves nanometer localization precision for 60 nm gold nanoparticles in an aqueous medium within a substantial 750 µm field of view at a 200 µs exposure time. This advancement will significantly facilitate the practical application of S-SPT in biosensors and related fields, making it more accessible and versatile for a broad range of research and industrial applications.