Nanoparticle Diameter Measurements with Event Camera Tracking

Characterization of gene therapy delivery particles following manufacturing is a difficult measurement task that is motivated by the need for these particles to satisfy safety and efficacy requirements. Quantifying features of these particles is challenging due to their small size (tens of nanometers to hundreds of nanometers) and variance in shape and composition. Single particle tracking (SPT) via light-based microscopy provides a means for measuring the size of nanoscale particles that is amenable to this use case but limited by camera frame speed. Unlike frame-based cameras, which compromise field of view (FOV) for frame speed, event cameras can preserve a constant FOV while collecting data at high frequencies to improve particle trajectory statistics and reduce errors in size estimation. This paper addresses data analysis problems arising from the novel data format generated by event cameras in the context of nanoparticle tracking. Our approach includes investigations of baseline comparisons of frame and event cameras with reference materials, data analysis methods (filtering methods, tracking, target cost), and tradeoffs between imaging sensors at high sampling rates. We report results for a set of one-dimensional event filters to improve tracking fidelity, multiple lens magnifications, and an application-specific cost function while measuring gold particles with known diameters (51.4 nm ± 4.1 nm) over a 24.4 second duration. To our knowledge, these results are the first application of an event camera toward quantitative nanoparticle characterization in the open literature.