Negative Differential Mobility and Trapping in Active Matter Systems

TL;DR

This paper uses simulations to study how active particles move through obstacles, revealing regimes of increased and decreased mobility depending on activity level and applied force, including trapping effects.

Contribution

It introduces a detailed simulation analysis of active matter mobility, highlighting negative differential mobility and trapping phenomena under various conditions.

Findings

Negative differential mobility occurs at intermediate forces.

Mobility is nonmonotonic with activity levels.

High activity leads to particle trapping and decreased mobility.

Abstract

Using simulations, we examine the average velocity as a function of applied drift force for active matter particles moving through a random obstacle array. We find that for low drift force, there is an initial flow regime where the mobility increases linearly with drive, while for higher drift forces a regime of negative differential mobility appears in which the velocity decreases with increasing drive due to the trapping of active particles behind obstacles. A fully clogged regime exists at very high drift forces when all the particles are permanently trapped behind obstacles. We find for increasing activity that the overall mobility is nonmonotonic, with an enhancement of the mobility for small levels of activity and a decrease in mobility for large activity levels. We show how these effects evolve as a function of disk and obstacle density, active run length, drift force, and motor force.