Enhanced gravitational trapping of bottom-heavy Janus particles over parallel microgrooves

• Published in: Soft matter 2024-11, Vol.20 (46), p.9208-9218
• Main Authors: Wen, Yan, Liu, Jiayu, Wang, Wei, Lai, Pik-Yin, Tong, Penger
• Format: Article
• Language: English
• Subjects: Alignment; Gravitational effects; Gravity; Nanoparticles; Polydimethylsiloxane; Probability density functions; Trapping
• ISSN: 1744-683X; 1744-6848; 1744-6848
• DOI: 10.1039/d4sm00989d

We report a systematic study on the barrier-crossing dynamics of bottom-heavy self-propelled particles (SPPs) over a one-dimensional periodic potential landscape ( ), which is fabricated on a microgroove-patterned polydimethylsiloxane (PDMS) substrate. From the measured steady-state probability density function (PDF) ( ; ) of the SPPs with different self-propulsion forces , we find that the escape dynamics of slow-rotating SPPs over the periodic potential ( ) can be well described by an activity-dependent potential ( ; ) under the fixed angle approximation. A theoretical model is developed to include the effects of the gravitational-torque-induced alignment on the polar angle and the hydrodynamic wall alignment on the azimuthal angle as well as their influence on the self-propulsion speed . By introducing a proper average of the activity-dependent potential ( ; ) over all possible particle orientations, our model explains the enhanced trapping effect on the bottom-heavy Janus particles. The obtained theoretical results are in good agreement with both the experimental and active Brownian particle simulation results. This work thus provides a thermodynamics description of the non-equilibrium barrier crossing of the Janus particles with nonuniform angular distributions over periodic potentials.