# Shape Transformations of Vesicles induced by Swim Pressure

## TL;DR

This paper investigates how active forces from Brownian particles inside vesicles induce diverse shape transformations, revealing novel phase transitions and dynamic behaviors through combined theoretical and simulation approaches.

## Contribution

It introduces a comprehensive study of active force effects on vesicle shapes, uncovering new phase transitions and oscillatory behaviors not seen in passive systems.

## Key findings

- Discontinuous spherical to prolate transition at low swim pressure
- Stochastic oscillations at high swim pressure
- Active forces induce novel shape dynamics in vesicles

## Abstract

While the behavior of vesicles in thermodynamic equilibrium has been studied extensively, how active forces control vesicle shape transformations is not understood. Here, we combine theory and simulations to study the shape behavior of vesicles containing active Brownian particles. We show that the combination of active forces, dimensionality and membrane bending free energy creates a plethora of novel phase transitions. At low swim pressure, the vesicle exhibits a discontinuous transition from a spherical to a prolate shape, which has no counterpart in two dimensions. At high swim pressure it exhibits stochastic spatio-temporal oscillations. Our work helps to understand and control the shape dynamics of membranes in active-matter systems.