While both active and granular matter have been extensively studied, here we investigate what happens when we mix the two of them, in a model system combining microparticles and cell assemblies. On a substrate covered with polystyrene or silica microparticles, we notice two regimes in the spreading of a cell aggregate: light particles are pushed by the cells and form a ring, which bonds to the substrate by adhesion forces that oppose spreading, while for heavy particles, the cell monolayer spreads above the particle bed. In both cases, cell activity is transmitted to inert beads, leading to the formation of cell-microparticle aggregates, which flicker and diffuse. We then study the formation and the spreading of hybrid aggregates of microparticles and living cells and observe phase separations and jamming transitions. Our study may have implications on processes such as cancer metastasis and development, and may guide cancer therapies based on inert particles.

尽管对活性物质和颗粒物质都进行了广泛的研究，但在这里我们研究了在结合了微粒和细胞装配体的模型系统中将两者混合时会发生什么。在覆盖有聚苯乙烯或二氧化硅微粒的基底上，我们注意到细胞聚集体的扩散有两种方式：轻粒子被细胞推动并形成环，该环通过与扩散相反的粘附力与基底结合，而重粒子，细胞单层扩散到颗粒床上方。在这两种情况下，细胞活性都传递给惰性珠，导致形成细胞微粒聚集体，该聚集体会闪烁并扩散。然后，我们研究了微粒与活细胞的混合聚集体的形成和扩散，并观察了相分离和干扰转变。