Revealing Cytoskeletal Dynamics and Avalanches via Active Micropost Arrays*

The cytoskeleton is critical for a wide range of cellular behavior, including motility, morphology, and mechanotransduction. However, understanding of the connections between molecular-scale processes and cell-scale dynamics is not complete. Here we present results using poly(dimethylsiloxane) active micropost array detectors (AMPADs) with embedded magnetic actuators to measure the fluctuations and local rheology of cells’ actomyosin stress fiber network and cortex in detail. We find that both structures display consistent power law rheology, along with highly heterogeneous and intermittent fluctuations. Notably, the fluctuating motion is dominated by large step-like displacements, resembling the dynamics observed in avalanches and earthquakes. The effects of substrate stiffness and geometry will also be discussed. Our results imply that actomyosin contractile units act in a highly collective manner and that cellular actomyosin networks self-organize into marginally stable plastic networks whose properties influence the biomechanical behavior of cells.