Shape transformation and manipulation of a vesicle by active particles.

Langevin dynamics simulations are employed to study the shape transformation of a two-dimensional vesicle induced by active particles both inside and outside. We find that the shape of the vesicle changes from circle, to capsule, and eventually to dumbbell with the enhancement of the particle activity. Under the cooperation between the inside and the outside active particles, such significant shape transformation is realized by tuning the activity in a small range. And unexpectedly, the fluctuations of the capsule and the dumbbell shapes are not completely random but mostly along the direction of the short axis. In the situation of strong activity, the inside of the dumbbell vesicle is analogous to a system of two chambers, which are connected by a narrow channel. Intriguingly, we observe the vibration of the channel width, accompanied with the exchange of active particles between the two chambers. We also find that dynamical manipulation of the vesicle shape is possible through tuning the particle activity dynamically. This work provides new ideas to the control of the vesicle morphology and new insights into the dynamics in the vesicle's shape transformation.