Activity-controlled clogging and unclogging of micro-channels

TL;DR

This paper introduces a method to control clogging in micro-channels using active particles whose self-propulsion can be externally toggled, enabling rapid formation or dissolution of obstructions.

Contribution

It demonstrates a novel active system mechanism for reversible clogging control in micro-channels based on external stimuli.

Findings

Active clogging occurs rapidly upon self-propulsion activation.

Phase diagram distinguishes clogged and open states by density and width.

Active clogging is more efficient than passive Brownian particle clogging.

Abstract

We propose a mechanism to control the formation of stable obstructions in two-dimensional micro-channels of variable sections taking advantage of the peculiar clustering property of active systems. Under the activation of the self-propulsion by external stimuli, the system behaves as a switch according to the following principle: by turning-on the self-propulsion the particles become active and even at very low densities stick to the walls and form growing layers eventually blocking the channel bottleneck, while the obstruction dissolves when the self-propulsion is turned off. We construct the phase diagram distinguishing clogged and open states in terms of density and bottleneck width. The study of the average clogging time, as a function of density and bottleneck width, reveals the marked efficiency of the active clogging that swiftly responds to the self-propulsion turning on. The resulting picture shows a profound difference with respect to the clogging obtained through the slow diffusive dynamics of attractive passive Brownian disks. This numerical work suggests a novel method to use particles with externally tunable self-propulsion to create or destroy plugs in micro-channels.