Myosin-Driven Advection and Actin Reorganization Control the Geometry of Confined Actomyosin Gel

Harnessing nanoscale motor proteins to control material shape is a promising strategy in nanotechnology and material science. One notable system is the actomyosin network, composed of actin filaments and myosin motor proteins, providing a platform for constructing contractile, shape-adaptive materials. While the role of actomyosin in shaping cells has been studied, the reverse question of how the boundary shape affects the actomyosin system remains poorly understood. Here, we present a microwell system that reveals how geometrical confinement directs the organization of actomyosin networks. By combining experiments and simulations, we show that the asymmetric shape of the microwells is transferred to contracted actomyosin gels via actin flow, which propagates laterally and upward, leading to actomyosin accumulation at the top surface. Furthermore, tuning the myosin contractility and actin polymerization rate allows control over gel size and shape. Our findings provide a framework for integrating molecular motors and cytoskeletons into confined architectures to create responsive biomaterials.