Fig. 1.

Single cell and multicellular traction forces in 2D and 3D systems. Traction forces exerted by a single cell migrating on a 2D substratum, b population of cells migrating collectively on a 2D substratum, c single cell migrating in a 3D matrix, and d population of cells migrating collectively in a 3D matrix. Cell-generated traction forces displace fiducial markers embedded in the substratum or matrix as cells migrate. Traction forces can be quantified by measuring the displacement of beads. Inspired by [20, 158]