Unraveling the three-dimensional morphology and dynamics of the optically evolving polystyrene nanoparticle assembly using dual-objective lens microscopy

Dynamically fluctuating assembly is prepared by trapping microparticles or nanoparticles at an interface. This phenomenon was previously described for 500 nm polystyrene nanoparticles optically trapped at water/glass interface, yielding a single disk-like assembly, which size is much larger than the focal volume. In this work, we use a dual-objective lens microscope to study the three-dimensional shape and dynamics of such disk-like assembly. The higher resolution of this system together with fast image acquisition (80 fps) rendered novel insights (e.g., particle fluctuation, assembly shape, interparticle distance, and so on), which could not be resolved using a conventional inverted microscope. These new insights will help to unravel the basis of this not yet fully understood “optically evolved phenomena,” which has a large potential in different research fields such as optical trapping, soft matter, and colloidal chemistry.