Rapid trapping and label-free optical characterization of single nanoscale extracellular vesicles and nanoparticles in solution

Achieving high-efficiency, comprehensive analysis of single nanoparticles to determine their size, shape, and composition is essential for understanding particle heterogeneity with applications ranging from drug delivery to environmental monitoring. Existing techniques are hindered by low throughput, lengthy trapping times, irreversible particle adsorption, or limited characterization capabilities. Here, we introduce Interferometric Electrohydrodynamic Tweezers (IET), an integrated platform that combines rapid molecular trapping, interferometric scattering imaging, and Raman scattering to rapidly trap and characterize single nanoparticles within seconds in one integrated platform. The IET platform enables to perform both trapping and Raman analysis within seconds in contrast with laser trapping Raman spectroscopy that often require several minutes per measurement. Furthermore, the IET platform can also operate under low particle concentration media, where particle loading is slow for conventional laser trapping Raman spectroscopy approach. We demonstrate the platform's capabilities by trapping and characterizing the size and chemical composition of colloidal polymer beads and nanoscale extracellular vesicles (EVs), while trapped in solution. Our IET represents a powerful optofluidics platform for comprehensive characterization of nanoscale objects, opening new avenues in nanomedicine, environmental monitoring, and beyond.