Collective dynamics of chemo-mechanical colloidal chains with active tips
Abstract
We report a study of the emergent dynamics arising in two-dimensional suspensions of semi-flexible chains whose tip is chemically active, generating a phoretic field. By varying the chain length (number of monomers per chain Npc), the area fraction ϕ, and the sign of the phoretic coupling J0, we map out a rich non-equilibrium phase diagram in the presence of phoretic interactions. For repulsive phoretic interactions (J0 > 0) between the chains, we find that short chains (Npc = 2) develop a transient chaotic flow state that crosses over at long times to a global polar flock with super-diffusive mean-squared displacement and long-ranged velocity correlations. Surprisingly, we find this state to have suppressed density fluctuations, indicating the emergence of hyperuniformity. At intermediate chain lengths (Npc ∼ 4-$8$), the repulsive chemical field drives chaotic mesoscale flows -- a dry route to active turbulence -- without the need for hydrodynamic interactions or steric alignment interactions. For attractive phoretic interactions (J0 < 0), chains self-organise into hedgehog-like micellar aggregates with heads forming the core and flexible tails radiating outward, in structural analogy with amphiphile micellisation but driven entirely by non-equilibrium self-propulsion. A coarse-grained theory of a tip-emitting active rod predicts the onset of the flocking of dimers, though overestimates the presence of polar order for longer chains. Our results establish phoretic tip activity as a minimal, experimentally realisable mechanism for a spectrum of collective states hitherto attributed to hydrodynamic interactions or steric alignment.
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BibTeX
@misc{subramaniam2026collective,
title = {{Collective dynamics of chemo-mechanical colloidal chains with active tips}},
author = {Arvin Gopal Subramaniam and Rajesh Singh},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.22318},
eprint = {2608.22318},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.22318},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Collective dynamics of chemo-mechanical colloidal chains with active tips
AU - Arvin Gopal Subramaniam
AU - Rajesh Singh
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2608.22318
UR - https://arxiv.org/abs/2608.22318
AB - We report a study of the emergent dynamics arising in two-dimensional suspensions of semi-flexible chains whose tip is chemically active, generating a phoretic field. By varying the chain length (number of monomers per chain N_pc), the area fraction ϕ, and the sign of the phoretic coupling J_0, we map out a rich non-equilibrium phase diagram in the presence of phoretic interactions. For repulsive phoretic interactions (J_0 > 0) between the chains, we find that short chains (N_pc = 2) develop a transient chaotic flow state that crosses over at long times to a global polar flock with super-diffusive mean-squared displacement and long-ranged velocity correlations. Surprisingly, we find this state to have suppressed density fluctuations, indicating the emergence of hyperuniformity. At intermediate chain lengths (N_pc ∼ 4-$8$), the repulsive chemical field drives chaotic mesoscale flows -- a dry route to active turbulence -- without the need for hydrodynamic interactions or steric alignment interactions. For attractive phoretic interactions (J_0 < 0), chains self-organise into hedgehog-like micellar aggregates with heads forming the core and flexible tails radiating outward, in structural analogy with amphiphile micellisation but driven entirely by non-equilibrium self-propulsion. A coarse-grained theory of a tip-emitting active rod predicts the onset of the flocking of dimers, though overestimates the presence of polar order for longer chains. Our results establish phoretic tip activity as a minimal, experimentally realisable mechanism for a spectrum of collective states hitherto attributed to hydrodynamic interactions or steric alignment.
ER -