# Active transport in a channel: stabilisation by flow or thermodynamics

## TL;DR

This study uses continuum simulations to explore how active fluids behave in channels, revealing stable flow states and key parameters influencing flow, which aids the development of active microfluidic devices.

## Contribution

It provides a systematic analysis of active fluid behavior in channels, including phase diagrams and the influence of flow alignment or tumbling.

## Key findings

- Identification of multiple stable flow states
- Development of a phase diagram for active flows
- Key parameters include channel width and flow alignment behavior

## Abstract

Recent experiments on active materials, such as dense bacterial suspensions and microtubule-kinesin motor mixtures, show a promising potential for achieving self-sustained flows. However, to develop active microfluidics it is necessary to understand the behaviour of active systems confined to channels. Therefore here we use continuum simulations to investigate the behaviour of active fluids in a two-dimensional channel. Motivated by the fact that most experimental systems show no ordering in the absence of activity, we concentrate on temperatures where there is no nematic order in the passive system, so that any nematic order is induced by the active flow. We systematically analyze the results, identify several different stable flow states, provide a phase diagram and show that the key parameters controlling the flow are the ratio of channel width to the length scale of active flow vortices, and whether the system is flow aligning or flow tumbling.