The Wanderings of Micro-Scallops

A flexible three-particle hinge.

In the 19th century, botanist Robert Brown observed pollen granules beneath his microscope jittering randomly. Einstein showed that this motion resulted from the impacts of much-smaller atoms against the particles. For small enough objects, the random walk of Brownian motion dominates their dynamics. A new study explores how flexible objects move at this Brownian scale.

The researchers used trios of colloids — microscopic particles — held together by a lipid fluid layer that allows the three particles to change shape without losing contact. Essentially, each trio forms a tiny hinge. As atoms strike the colloids, they both move and change shape.

Compared to rigid shapes, the researchers found their flexible hinges moved around in space about 3-15% faster. They also found coupling between the shape changes and motion. When the colloids hinge closed, it propels them in the direction the hinge points. Because this resembles the propulsion of scallops, the researchers refer to this as the “Brownian quasi-scallop mode.” (Image and research credit: R. Verweij et al.; via

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