2023-05-02 10:25:41
MDespite the ability to tie knots in all areas, humans still have a lot to learn from a tiny, tangle-prone worm.
Header image: “knot” or “blob” of Lumbriculus variegatus worm. (Georgia Tech)
Commonly known as California blackworm (California blackworm), the tiny invertebrate Lumbriculus variegatus has graciously shared some of its secrets as part of a new study looking at the math behind its amazing living nodes.
Researchers at the Georgia Institute of Technology in the United States have been studying black worms for years, intrigued by their capacity for ultra-fast movement and their collective behavior, including how they form large knots, or “blobs”, with thousands of worms that can also disperse within milliseconds. In this new study, researchers from the Georgia Institute of Technology (Georgia Tech) et du Massachusetts Institute of Technology (WITH/ USA) used ultrasound to shed light on the worm ‘blobs’, revealing details that might inspire the design of robots with similar abilities.
Introducing the very rapid entanglement and untangling of the Lumbriculus variegatus. (Georgia Tech College of Engineering)
According to Saad Bhamla, study co-author (link below) and assistant professor in Georgia Tech’s School of Chemical and Biomolecular Engineering:
We wanted to understand the exact mechanisms underlying how worms alter the dynamics of their movements to achieve super-fast entanglement and untangling. Moreover, these are not typical filaments like string, ethernet cables or spaghetti, but living, active tangles that are out of balance, which adds a fascinating layer to the question.
The wild blackworm lives in North America and Eurasia, where it inhabits shallow waters at the edges of ponds, lakes, and swamps, feeding on dead plants and microorganisms in mud. Individuals measure from 4 to 8 centimeters, but they can also intertwine intricately, forming a blob of living worms of up to 50,000 individuals.
Blob formation helps them survive a harsh environment, such as extreme temperatures or a lack of water, which would kill single worms. Research has shown that a blob of worms can behave like a solid or a fluid and can even make collective decisions. And while the worms can take several minutes to come together, they can separate in milliseconds.
According to Harry Tuazon, a bioengineer at Georgia Tech and a graduate student in Bhamla’s lab:
I was shocked when I pointed a UV light at the worms and they dispersed so quickly. But to understand this complex and fascinating maneuver, I started experimenting with just a few worms.
(Harry Tuazon, Bhamla Lab/ Georgia Institute of Technology)
After seeing the Tuazon videos showing the rapid dispersal of worms from a blob, bioengineer Vishal Patil (now at Stanford University) and his colleagues jumped at the chance to team up and to study.
According to Patil:
Knots and tangles are a fascinating area where physics and mechanics meet some very interesting mathematics. These verses seemed like a good playground for studying topological principles in systems made up of filaments.
In one video, Patil noticed a worm moving in a figure 8, a “helical gait” known for decades in the black worm. However, Patil wondered if this movement was not also part of the secret of the ultra-rapid decomposition of the blobs. The researchers hoped to be able to explain a blob of worms mathematically, by modeling how the worms entangle and scatter, but they would need more data. Recording accurate images of a blob’s structure has proven difficult.
(Harry Tuazon, Bhamla Lab/ Georgia Institute of Technology)
Selon Tuazon :
We tried all sorts of imaging techniques for months, including X-rays, confocal microscopy, and tomography, but none of them gave us the real-time resolution we needed.
The researchers ended up finding an effective technique: ultrasound. They immobilized a worm in a non-toxic jelly and used a commercial ultrasound device to look inside. Bhamla, Tuazon and other Georgia Tech researchers analyzed the resulting ultrasound videos and then plotted some 46,000 data points to help Patil and Dunkel study the mechanics and topology of the worm blobs. They used this data to create a mathematical model of entanglement and untangling of the black worm, predicting that each worm should intertwine with at least two others when they merge. This model also suggests that helical gaits are the key to fast dispersals.
Visualizations of their model closely match actual videos of worms tangling and untangling, the researchers report, showing how the worms’ helical movements allow them to rapidly entangle themselves in order to set up a rapid release mechanism, which s presses similar movements.
For Patil:
What is striking is that these tangled structures are extremely complicated. They are messy and complex structures, but these living worm structures are able to manipulate these nodes for crucial functions.
Studying worm nodes might have many practical applications, the researchers note, such as synthetic filaments or shape-shifting robots that can alter their properties on demand.
Selon Bhamla :
Imagine a flexible, non-woven material made up of millions of rope-like filaments that can tangle and untangle on command, forming a clever adhesive bandage that transforms as a wound heals, or a smart filtration material that alters pore topology to trap particles of different sizes or chemical properties. ” The possibilities are limitless.
The study published in Science : Ultrafast reversible self-assembly of living tangled matter and presented on the Georgia Institute of Technology website: Unraveling the Mathematics Behind Wiggly Worm Knots.
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