Self-sustained frictional cooling in active matter
Abstract
Cooling processes in nature are typically generated by external contact with a cold reservoir or bath. According to the laws of thermodynamics, the final temperature of a system is determined by the temperature of the environment. Here, we report a spontaneous internal cooling phenomenon for active particles, occurring without external contact. This effect, termed ``self-sustained frictional cooling'', arises from the interplay between activity and dry (Coulomb) friction, and in addition is self-sustained from particles densely caged by their neighbors. If an active particle moves in its cage, dry friction will stop any further motion after a collision with a neighbor particle thus cooling the particle down to an extremely low temperature. We demonstrate and verify this self-sustained cooling through experiments and simulations on active granular robots and identify dense frictional arrested clusters coexisting with hot, dilute regions. Our findings offer potential applications in two-dimensional swarm robotics, where activity and dry friction can serve as externally tunable mechanisms to regulate the swarm's dynamical and structural properties.
Keywords
Cite
@article{arxiv.2503.02996,
title = {Self-sustained frictional cooling in active matter},
author = {Alexander P. Antonov and Marco Musacchio and Hartmut Löwen and Lorenzo Caprini},
journal= {arXiv preprint arXiv:2503.02996},
year = {2025}
}