Flow sorter with video-regulated droplet spacing

Abstract

A droplet-deflection flow sorter images a series of droplets, analyzes the image to determine droplet spacing, and alters flow velocity to achieve a desired spacing. Cells in a suspension are forced by gas pressure into a narrow conduit to serialize them and then out a nozzle that includes a "window" that allows cells of interest to be characterized. Droplets breaking off from the exiting jet are imaged by a video system including a strobed light source and a video camera. Droplet spacing is determined by locating the centers of gravity of the droplets. The centers of gravity are located by processing the droplet images to produce line segments corresponding to volumetric droplet slices, with the relative volumes of the slices being proportional to the squares of the line segment lengths. This approach determines droplet center positions and thus spacing more accurately than non-imaging methods, especially with aspherical droplets and droplets with satellites. The actual droplet spacing is compared to desired spacing, and the pressure regulator is adjusted accordingly. Synchronously, voltage is applied to droplets of interest. The droplets pass between a pair of deflection plates with a potential difference between them, so that charged droplets containing cells of interest are deflected and gathered while uncharged droplets not containing such cells are not deflected.

Dependencies are inferred from the claim text.