The Mechanics Behind California Blackworms' Rapid Tangling and Untangling Behaviors

Monday - May 1 2023, 22:19 UTC - 1 year ago

Georgia Tech and MIT researchers conducted a study focused on understanding the rapid tangling and untangling behaviors of California blackworms using ultrasound imaging and meticulous data tracking. Their research provided the first mathematical model of these behaviors and could inspire the design of advanced, fiber-like, shapeshifting robotics as well as multifunctional materials.

Georgia Tech and MIT researchers have used ultrasound imaging and meticulous data tracking to understand the rapid tangling and untangling behaviors of California blackworms. Their study, which provided the first mathematical model of these behaviors, could inspire the design of advanced, shapeshifting robotics and multifunctional materials.

For millennia, humans have used knots for all kinds of reasons — to tie rope, braid hair, or weave fabrics. But there are organisms that are better at tying knots and far superior — and faster — at untangling them.

Tiny California blackworms intricately tangle themselves by the thousands to form ball-shaped blobs that allow them to execute a wide range of biological functions. But, most striking of all, while the worms tangle over a period of several minutes, they can untangle in mere milliseconds, escaping at the first sign of a threat from a predator.

Saad Bhamla, assistant professor in the School of Chemical and Biomolecular Engineering at Georgia Tech, wanted to understand precisely how the blackworms execute their tangling and untangling movements. To investigate, Bhamla and a team of researchers at Georgia Tech linked up with mathematicians at MIT. Their research, published on April 27 in the journal Science, could influence the design of fiber-like, shapeshifting robotics that self-assemble and move in ways that are fast and reversible. The study also highlights how cross-disciplinary collaboration can answer some of the most perplexing questions in disparate fields.

Fascinated by the science of ultrafast movement and collective behavior, Bhamla and Harry Tuazon, a graduate student in Bhamla’s lab, have studied California blackworms for years, observing how they use collective movement to form blobs and then disperse.

"We wanted to understand the exact mechanics behind how the worms change their movement dynamics to achieve tangling and ultrafast untangling," Bhamla said. "Also, these are not just typical filaments like string, ethernet cables, or spaghetti — these are living, active tangles that are out of equilibrium, which adds a fascinating layer to the question." .

Tuazon, a co-first author of the study, collected videos of his experiments with the worms, including macro videos of the worms’ collective dispersal mechanism and microscopic videos of one, two, three, and several worms to capture their movements.

"I was shocked when I pointed a UV light toward the worm blobs and they dispersed so explosively," Tuazon said. "But to understand this complex and mesmerizing maneuver, I started conducting experiments with only a few worms." .

Bhamla and Tuazon approached MIT mathematicians Jörn Dunkel and Vishal Patil (a graduate student at the time and now a postdoctoral fellow at Stanford University) about a collaboration. After seeing Tuazon’s videos, the two theorists, who specialize in knots and topology, were eager to join.

"Knots and tangles are a fascinating area where physics and mechanics meet some very interesting math," said Patil, co-first author on the paper. "These worms seemed like a good playground to investigate topological principles in systems made up of filaments." .

A key moment for Patil was when he viewed Tuazon’s video of a single worm that had been provoked into the escape response. Patil noticed the wobbling head-to-tail motion — a movement known as the “corkscrew maneuver” — that the worm used to untangle itself.

The researchers constructed a mathematical model describing the movement dynamics of the corkscrew maneuver and applied ultrasound imaging to observe its effects on the worms. They found that having just a few worms corkscrew at once was enough to cause the whole blob to untangle. In addition, the worms did so in a synchronized fashion — an indication that the environment wielded an influence over how the worms moved.