Imagine if your neck could stretch long enough to reach your local store while sitting on the couch. That would be a human representation of what a single-celled predator can do. And now, a long-standing mystery has been solved: how that animal can stretch its “neck” to more than 30 times the length of its “body.”

The organism’s cell membrane is folded into a series of folds that can only unfold and fold in one direction. Elliot Flaum Stanford University and her colleagues Manu Prakash They found ways to stretch and fold the paper without it getting tangled. “Most of this came from just playing with paper,” Prakash says.

Lacrimaria Aurore It is a single-celled organism, or protist, that lives in freshwater and hunts prey with a highly extensible neck-like protrusion. Its name means “swan’s tears” after its swan-like neck and teardrop-shaped body.

The cell membrane is very flexible, but it is not elastic and does not stretch. L. Aurore Why their necks stretch so far has remained a mystery since they were first observed under a microscope in the 16th century. “Compared to a lot of other organisms, the neck stretches by an order of magnitude,” Prakash says. “That’s the mystery.”

He and Flaum L. Aurore To solve this mystery, samples taken from the swamp six or seven years ago were studied. Flaum used a variety of techniques to L. Aurore And inside that cytoskeleton is made up of structures called microtubules. “We looked at it in a variety of different ways to try to understand what was going on,” she says.

This means: L. Aurore It is folded into 15 pleats, with each pleat spiralling around the cell to form a helical structure, a folding pattern Prakash calls “curved crease origami,” or “lacrigami.”

but, L. Aurore How can such a vast region of the cell membrane unfold and fold without getting tangled? What Prakash and Flaum discovered is that because the pleats are stabilized by bands of microtubules connected to them, the entire fold cannot unfold at once. Instead, only a single point of the fold can unfold or fold at any one time.

As these points move in parallel along each of the 15 wrinkles, the cell membrane unfolds in an orderly fashion, lengthening the neck. Reversing this process shortens the neck.

“Instead of folding randomly like you would when crumpling a sheet of paper, it has guide rails that help you fold it the same way every time,” Flaum says.

The folding and unfolding of cells is driven by the beating of cilia that cover the entire surface of the cell, Prakash said. Unlike springs, cilia require energy to refold and unfold, whereas cell membranes bend easily and require very little energy.

As far as he knows, no one has discovered this origami technique before. “When I discovered this, I always assumed that someone playing with paper would have discovered this origami,” Prakash says. “It’s so easy.” He says anyone with paper and tape can make it.

“The neck’s ingenious origami-like design makes the cilia effective for high-speed, long-distance hunting,” they write. Leonardo Gordillo and Enrique Cerda At the University of Santiago in Chile Accompanying Articles“The origami-like protrusion mechanism identified by Flaum and Prakash has the potential to inspire new strategies in soft-matter engineering.”

In fact, Prakash and Flaum are currently working on developing a medical robot based on Rakurigami. “If you had a tiny microrobot in a very tight space, and it could suddenly stretch, that would be very useful for microsurgery,” he says. “But we did this research because it’s just beautiful and a mystery to solve. We didn’t expect it to be useful in any way.”