  The cytoskeleton is a model active matter system that controls diverse
cellular processes from division to motility. While both active actomyosin
dynamics and actin-microtubule interactions are key to the cytoskeleton's
versatility and adaptability, an understanding of their interplay is lacking.
Here, we couple microscale experiments with mechanistic modeling to elucidate
how connectivity, rigidity, and force-generation affect emergent material
properties in in vitro composites of actin, tubulin, and myosin. We use
time-resolved differential dynamic microscopy and spatial image autocorrelation
to show that ballistic contraction occurs in composites with sufficient
flexibility and motor density, but that a critical fraction of microtubules is
necessary to sustain controlled dynamics. Our active double-network models
reveal that percolated actomyosin networks are essential for contraction, but
that networks with comparable actin and microtubule densities can uniquely
resist mechanical stresses while simultaneously supporting substantial
restructuring. Our findings provide a much-needed blueprint for designing
cytoskeleton-inspired materials that couple tunability with resilience and
adaptability.
