Credit: Image courtesy of Zvonimir Dogic, Brandeis University
Upon confinement and powered by tiny molecular motors, an “active” fluid transitions from locally chaotic (left) to long-range unidirectional flow, as seen in the donut-shaped (center) and circular (right) pipes. Each figure contains the instantaneous (left) and time-averaged (right) motion. Localized counter-clockwise (blue) and clockwise (red) whirlpools are shown. The organization of the colored areas is a measure of the extent to which the fluid is flowing in one direction.