Living cells can adapt their shape in response to their environment, a process driven by the interaction between their flexible membrane and the activity of the underlying cytoskeleton. However, the precise physical mechanisms of this coupling remain unclear. Here we show how cytoskeletal forces acting on a biomimetic membrane affect its deformations. Using a minimal cell model that consists of an active network of microtubules and molecular motors encapsulated inside lipid vesicles, we observe large shape fluctuations and travelling membrane deformations. Quantitative analysis of membrane and microtubule dynamics demonstrates how active forces set the temporal scale of vesicle fluctuations, giving rise to fluctuation spectra that differ in both their spatial and temporal decays from their counterparts in thermal equilibrium. Using simulations, we extend the classical framework of membrane fluctuations to active cytoskeleton-driven vesicles, demonstrating how correlated activity governs membrane dynamics and the roles of confinement, membrane material properties and cytoskeletal forces. Our findings provide a quantitative foundation for understanding the shape-morphing abilities of living cells.

活细胞可以根据环境调整其形状，这一过程由其柔性膜与底层细胞骨架活性之间的相互作用驱动。然而，这种耦合的确切物理机制仍不清楚。在这里，我们展示了作用在仿生膜上的细胞骨架力如何影响其变形。使用由封装在脂质囊泡内的微管和分子马达的活性网络组成的最小细胞模型，我们观察到较大的形状波动和移动膜变形。膜和微管动力学的定量分析表明，主动力如何设置囊泡波动的时间尺度，从而产生在空间和时间衰减上与热平衡中的波动光谱不同的波动光谱。使用模拟，我们将膜波动的经典框架扩展到活性细胞骨架驱动的囊泡，展示了相关活动如何控制膜动力学以及限制、膜材料特性和细胞骨架力的作用。我们的研究结果为理解活细胞的形状变形能力提供了定量基础。