Active Brownian particles can mimic the pattern of the substrate

ABSTRACT

Active Brownian particles (ABPs) have been identified as a successful way of modeling the moving microorganism on the substrate. In recent studies, it is shown that such organisms can sense the characteristics of the substrate. Motivated by such work, we studied the dynamics and the steady state of ABP moving on a substrate with space-dependent activity. On the substrate, some regions are marked as high in activity, and other regions are such that particles behave as passive Brownian particles. The system is studied in two dimensions with step, sigmoid, Gaussian, and cone shape distribution of activity profile on the substrate. The whole interface of the activity profile is symmetrically divided into two regions. This led to the flow of particles from the active region to the passive region. The final steady state of particle density profile, polarization and flux very much follows the structure of the inhomogeneous activity, and the density in high activity region is lower, maximum at the interface and nearly constant with mean density in the passive region. Further, the steady state density profile for various shapes and designs on two-dimensional substrates is studied. Hence, the collection of ABPs on an inhomogeneous substrate can mimic the inhomogeneity of the substrate.

KEYWORDS:

• Active matter
• activity gradient
• inhomogeneous substrate
• phase separation
• self propelled particles

Acknowledgments

P.K.M., A.K., and S.M. thank PARAM Shivay for computational facility under the National Supercomputing Mission, Government of India at the Indian Institute of Technology, Varanasi. Computing facility at the Indian Institute of Technology (BHU), Varanasi, is gratefully acknowledged. S.M. thanks DST-SERB India, MTR/2021/000438, and CRG/2021/006945 for financial support. P.K.M. thanks the University Grant Commission, India, for providing scholarship.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the DST-SERB, India [CRG/2021/006945]; University Grants Commission [1276 CSIR-UGC NET DEC-2018].