# Active Matter Invasion

## TL;DR

This paper uses numerical simulations to explore how confinement and activity influence collective invasion modes in biological active materials, revealing thresholds for different invasion behaviors and their mechanical mechanisms.

## Contribution

It introduces a computational framework to classify invasion modes based on activity levels and confinement, highlighting the transition from coherent growth to blob detachment.

## Key findings

- Active materials grow coherently at low activity levels.
- Blob detachment occurs above a specific activity threshold.
- Invasion speed and mode depend on activity and confinement.

## Abstract

Biological active materials such as bacterial biofilms and eukaryotic cells thrive in confined micro-spaces. Here, we show through numerical simulations that confinement can serve as a mechanical guidance to achieve distinct modes of collective invasion when combined with growth dynamics and the intrinsic activity of biological materials. We assess the dynamics of the growing interface and classify these collective modes of invasion based on the activity of the constituent particles of the growing matter. While at small and moderate activities the active material grows as a coherent unit, we find that blobs of active material collectively detach from the cohort above a well-defined activity threshold. We further characterise the mechanical mechanisms underlying the crossovers between different modes of invasion and quantify their impact on the overall invasion speed.