Complex interactions between cellular systems and their surrounding extracellular matrices are emerging as important mechanical regulators of cell functions, such as proliferation, motility and cell death, and such cellular systems are often characterized by pulsating actomyosin activities. Here, using an active gel model, we numerically explore spontaneous flow generation by activity pulses in the presence of a viscoelastic medium. The results show that cross-talk between the activity-induced deformations of the viscoelastic surroundings and the time-dependent response of the active medium to these deformations can lead to the reversal of spontaneously generated active flows. We explain the mechanism behind this phenomenon based on the interaction between the active flow and the viscoelastic medium. We show the importance of relaxation time scales of both the polymers and the active particles and provide a phase space over which such spontaneous flow reversals can be observed. Our results suggest new experiments investigating the role of controlled pulses of activity in living systems ensnared in complex mircoenvironments.

细胞系统及其周围细胞外基质之间的复杂相互作用正在作为细胞功能（如增殖，运动性和细胞死亡）的重要机械调节剂出现，并且此类细胞系统通常以脉动肌动蛋白活性为特征。在这里，我们使用活性凝胶模型，在存在粘弹性介质的情况下，通过活动脉冲数值地研究了自发流动的产生。结果表明，粘弹性环境的活动引起的变形与活性介质对这些变形的时间依赖性响应之间的串扰会导致自发生成的活动流发生逆转。我们基于活动流和粘弹性介质之间的相互作用来解释此现象背后的机理。我们显示了聚合物和活性颗粒的弛豫时间尺度的重要性，并提供了可以观察到这种自发逆流的相空间。我们的结果表明，新的实验研究了在复杂的微环境中受控制的活动脉搏在活体系统中的作用。