Particle-Based Detection of Surface Chemistry via Optical Microscopy-Integrating Microfluidics, Light-Induced Activity of Colloids and Data Science.

We present particle-resolved methods for determining the porosity and surface area of microparticles, based on single-particle trajectory analysis conducted via optical video microscopy integrated with microfluidics and LED illumination. This technique introduces a unique combination of analytical advantages that address key limitations of conventional methods, such as BET nitrogen adsorption. Notably, (1) the method operates with extremely low analyte quantities on the order of micrograms or less and in the form of dilute aqueous dispersions, eliminating the need for drying or bulk sample preparation; (2) surface area quantification is performed on a per-particle basis, with total surface area determined by summing up all individual particle measurements, enabling high-resolution analysis of particle-to-particle heterogeneity; and (3) the entire workflow from sample preparation to data acquisition and surface area calculation is rapid, straightforward, and relies only on a pre-defined, self-generated reference data library. We validate the method using both plain and mesoporous SiO2 microparticles, demonstrating a relative precision of approximately 9%, in line with benchmark techniques such as nitrogen sorption. This approach thus offers a robust, accessible alternative for surface area analysis, utilizing standard optical microscopy equipment available in most laboratory settings, and is particularly well suited for low-sample-volume applications in material characterization.