A simple model system for self-propelled particles passing a bottleneck

TL;DR

This study investigates how active and passive granular particles, modeled as pharmaceutical capsules, pass through a bottleneck under gravitational bias, revealing differences in their flow behavior on a vibrating, tilted surface.

Contribution

The paper introduces an experimental system using pharmaceutical capsules to compare active and passive granular flow through a bottleneck under gravity.

Findings

Active particles show different flow dynamics compared to passive ones.

Tilted vibrating surface influences particle movement direction.

Particle passage efficiency varies with activity status.

Abstract

We study the passage of active and passive granular particles through a bottleneck under gravitational bias. The grains are pharmaceutical capsules with nearly spherocylindrical shapes on a vibrating table. The vibrating plate is slightly tilted in order to break the in-plane symmetry and to give particles a motivation to move in a preferential direction on the plate. The passage through a narrow gate with openings comparable to the grain length is studied using video imaging, and particle positions and velocities are extracted from the recorded frames. We compare the behaviour of asymmetrically filled, active capsules with symmetrically filled, passive ones.