Collaborators: Fridtjof Brauns, Yimin Luo, M. Cristina Marchetti

Publications: Published in PRX Life (open access). Preprint can be accessed here.

Motivated by recent experiments on growing fibroblasts, we examine the development of nematic order in a colony of elongated cells proliferating on a nematic elastomer substrate. After sparse seeding, the cells divide and grow into locally ordered, but randomly oriented, domains that then interact with each other and the substrate. Global alignment with the substrate is only achieved above a critical density, suggesting a collective mechanism for the sensing of substrate anisotropy. The system jams at high density, where both reorientation and proliferation stop. Using a continuum model of a proliferating nematic liquid crystal, we examine the competition between growth-driven alignment and substrate-driven alignment in controlling the density and structure of the final jammed state. We propose that anisotropic traction forces and the tendency of cells to align perpendicular to the direction of density gradients act in concert to provide a mechanism for collective cell alignment.

I will present published results in a talk at APS Global Summit 2026 in the DSOFT Emerging Soft Matter Excellence Award Session.

I presented the homogeneous theory in a poster at the 2024 Active Solids Conference at KITP.

I presented some early results in a poster at the 2024 Boulder School for Condensed Matter.

Cartoon of alignment mechanism. A spherically symmetric gaussian patch of cells becomes an elongated ellipse due to anisotropic diffusion caused by anisotropic friction. The anisotropic density gradients then lead to realignment of cells in the patch.