---
title: "No friction required: Self-locking in entangled assemblies of curved filaments"
authors:
  - "Benjamin R. Greenvall"
  - "Jay van den Berg"
  - "Ross E. Meinhart"
  - "Patrick A. Staudenmayer"
  - "Alfred J. Crosby"
  - "Gregory M. Grason"
year: 2026
venue: "arXiv preprint (cond-mat.soft)"
arxiv: "2610.36330"
doi: null
source: "https://arxiv.org/abs/2610.36330"
topics:
  - "soft-matter"
  - "filaments"
  - "elasticity"
  - "topology"
seed_rank: 2475
seed_batch: "curiosity-2026-10-31"
reviewed: "2026-10-31"
pool: "maths"
relevance_score: 7
cites:
  - title: "No friction required: Self-locking in entangled assemblies of curved filaments"
    url: "https://arxiv.org/abs/2610.36330"
    year: 2026
    arxiv: "2610.36330"
    doi: null
see: ["2433-the-elastic-figure-eight-knot-is-not-planar"]
---

# No friction required: Self-locking in entangled assemblies of curved filaments

## One-sentence takeaway

Bundles of intrinsically helical filaments can hold together with no friction and no external load. Elastic pre-stress from overcrowding alone locks them, and the alternative, depending on filament number and preferred shape, is spontaneous unravelling by a soliton-like detanglement front. Some bundle geometries cannot be made self-locking for any friction.

## Why it's lovely

Since Galileo, rope has been explained as twist turning tension into pressure, with friction doing the holding, which is why a cut rope frays. Greenvall, Grason and coworkers show that a frictionless model of curved filaments can still lock, purely through the competition between bending elasticity and non-overlap. When it does not lock, the unravelling travels down the bundle like a soliton. Galileo, rope and knot topology are joined by a clean mechanism, and it is also a design rule for materials that assemble and disassemble on demand. It sits next to the elastic-knot card from the last Curiosity run.

## Key ideas

- **Minimal ingredients.** Intrinsically curved (helical) filaments, an elastic energy for changing shape, and traction-free repulsion. No friction and no load.
- **Two fates.** Overcrowding pre-stress gives either self-locking entanglement or spontaneous detanglement, propagating as a soliton-like front.
- **Fracture criterion.** A generalized criterion for spontaneous detangling is tested in experiments and in simulations with friction.
- **Negative result.** Some bundled structures cannot self-lock at any friction value, so shape elasticity, not friction, decides.
- **Broader reach.** "Purely elastic cohesion" may explain knits, knots and bird's-nest jams, and it suggests stimuli-responsive active filament materials.

## Caveats

Rope-like helical bundles only; braids, knits and weaves are suggested, not shown. Real fibers do have friction, so the frictionless model isolates a mechanism rather than describing any particular rope. I read the abstract and the introduction.

## Links

- arXiv abstract: https://arxiv.org/abs/2610.36330
- PDF: https://arxiv.org/pdf/2610.36330