Скачать или смотреть The Countoscope: Counting Particles to Measure Properties of Suspensions in and Out of Equilibrium

Modern microscopy techniques can image complex, microscopic systems with an unprecedented resolution – but methods to analyze these images are much less robust. Available techniques to probe dynamics rely on reconstructing particle trajectories, which can be difficult or impossible in some cases, or some form of video analysis, which can be unreliable and expensive. Inspired by the early work of Smoluchowski, the Colorado School of Mines' Brennan Sprinkle introduces the "Countoscope," a technique that nearly completely ameliorates these issues by simply counting particle number fluctuations in observation boxes. By varying properties like the size or aspect ratio of the boxes and taking different measures of correlation between these observation boxes, researchers can "zoom" in or out to measure individual or collective particle kinetics in both passive and active systems. Using colloidal suspensions as a test case, Sprinkle employs a combination of experiments, simulations, and analytical theory to support his findings.