Posture selection in active elastic filaments
Abstract
Posture control in slender bodies such as snakes and eels arises from the interplay between passive deformation, active internal actuation, and task-level constraints. We formulate a general framework for the selection of stable postures in active elastic filaments subject to distributed forcing from gravity and fluid drag, by combining the constraints of mechanical equilibrium with optimal control theory. Our theory leads to a minimal description in terms of parameters governing the competition between hydrodynamic and gravitational loading, elasticity, and activity. We show that posture selection reflects a trade-off between control cost, function and dynamical stability, leading to the coexistence of distinct solution branches and abrupt transitions between them. Applying the theory to sessile eels in flow, we recover the experimentally observed transition from upright to reclining postures and predict scaling laws for body shape and exposed length. More generally, our results provide a unified perspective on how active filaments can regulate geometry to maintain function in external fields, with implications for biological and artificial systems.
Related
- The hydrodynamic Euler-elastica: shape transitions in the dynamical buckling of elastic filaments in Stokes flow
- Localization of Active Particles on Random Arrays of Parallel Filaments
- Spontaneous Motion Generates Reversible Nonreciprocity in an Achiral Active Elastic Ring
- From Action Principle to Stochastic Thermodynamics of Elastic and Viscous Active Matter
- Linear and nonlinear active microrheology of viscous, viscoelastic, and elastic media: A fluid particle dynamics approach
BibTeX
@misc{pearl2026posture,
title = {{Posture selection in active elastic filaments}},
author = {Adam Pearl and Ludwig A. Hoffmann and L. Mahadevan},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.17924},
eprint = {2609.17924},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.17924},
note = {CC BY-SA 4.0},
}
RIS
TY - UNPB
TI - Posture selection in active elastic filaments
AU - Adam Pearl
AU - Ludwig A. Hoffmann
AU - L. Mahadevan
PY - 2026
DA - 2026/09/15
PB - arXiv
DO - 10.48550/arxiv.2609.17924
UR - https://arxiv.org/abs/2609.17924
AB - Posture control in slender bodies such as snakes and eels arises from the interplay between passive deformation, active internal actuation, and task-level constraints. We formulate a general framework for the selection of stable postures in active elastic filaments subject to distributed forcing from gravity and fluid drag, by combining the constraints of mechanical equilibrium with optimal control theory. Our theory leads to a minimal description in terms of parameters governing the competition between hydrodynamic and gravitational loading, elasticity, and activity. We show that posture selection reflects a trade-off between control cost, function and dynamical stability, leading to the coexistence of distinct solution branches and abrupt transitions between them. Applying the theory to sessile eels in flow, we recover the experimentally observed transition from upright to reclining postures and predict scaling laws for body shape and exposed length. More generally, our results provide a unified perspective on how active filaments can regulate geometry to maintain function in external fields, with implications for biological and artificial systems.
ER -