In lab, blackworms move faster through narrow channels

A simulated worm did something that looked backward: it moved through a narrow channel faster than a wide one. The model, developed by Justin Xu and the team in Saad Bhamla's lab, reduced the animal to a flexible chain that could propel itself forward. When the same idea was tested with living California blackworms, the result held.

Ph.D. student Paulami Sarkar designed experiments using 12-centimeter-long channels, about twice the length of a worm. Their widths ranged from 1 to 8 millimeters; a worm is about half a millimeter in diameter. For that channel length, the worms took nearly three times as long to escape from the wider channels as from the narrower ones.

The narrow passage acts like a guide rail. Its walls limit sideways movement and keep the worm pointed toward the exit. In the wider channel, the worms had room to pause, bend, change direction and explore across the space. Those repeated detours turned extra freedom into slower progress.

The finding differs from the usual picture of confinement in passive threadlike materials such as DNA, whose movement through tighter pores generally slows because there is less room to bend and change shape. Blackworms are active filaments: they continuously propel themselves by contracting and bending their flexible bodies.

So what does it change in practice? The result gives robot designers a physical clue for machines that may need to travel through narrow gaps: restricting sideways motion could sometimes make a self-propelled flexible robot reach its destination sooner. That remains an implication, not a demonstrated product—the reported work tested simulations and worms, not a robot.