Cell Driven Buckling of Active Collagen Microbeams

Collective cell migration and multi-cellular force generation has been explored in recent years in order to gain fundamental insight into the role mechanics plays in tissue development, health, and disease. Great progress has been made studying 2D monolayers, with an emerging understanding of the collective cell response to substrate stiffness and cell density. To more broadly model and investigate mechanical processes in living tissues, it is critical to develop the 3D counterparts of these 2D systems. Here we 3D print simple structures from fibroblasts dispersed in collagen-I networks, which are gently supported within a jammed microgel growth medium. For the case of long, thin microbeams, we observe a self-induced mechanical buckling that can be predicted from classical Euler-Bernoulli beam theory. By varying the beam aspect ratio and cell number density, we can control the transition between stable contracting beams and unstable buckling beams. This transition also allows the indirect measurement of cell generated contractile stress in 3D.