Surface force sensed by cells used for autonomous migration

In this study, we develop a platform for investigating the mechanical perceptual ability of a cell and monitor its migration guided by a pure surface gradient rigidity. The cells are cultured on a flexible substrate with variable mechanical stiffness with other conditions kept unvarying. The thickness polydimethylsiloxane (PDMS) layer on glass trench surface with thickness variation was used to create a rigidity gradient between stiff (2.5 µm) and soft (7.5 µm) regions. The changes of surface rigidity were 48.8% in normal direction (stiff: 2.9 N/m, soft: 1.4 N/m) and 25.5% in lateral direction (stiff: 1 N/m, soft: 0.8 N/m), respectively. A fabrication process of rigidity gradient composite layered micro-device was developed to minimize the topographical effect that may alter the patterns of cell attachment and migration. We cultured NIH 3T3 cells on the proposed flexible substrate coated with an extracellular matrix (ECM), and demonstrated that the cells were strongly affected by the mechanical rigidity of surface. The designed device can be used to facilitate our understanding of mechanotransduction in cells under a given environment.