Representative images of endothelial focal adhesions after 24 hours on TCPS, SiO2 membranes, Stiff (2 MPa) PDMS and Soft (5 kPA) PDMS substrates. Cells were stained for nuclei (DAPI, blue), F-actin (phalloidin, green), and focal adhesions (anti-vinculin, red). Bottom: Quantification of focal adhesion formation after 24 hours of culture. Formation of distinct focal adhesions was quantified for all substrates - percent of cells with distinct focal adhesions and number of focal adhesions per cell (n > 20 for each substrate; mean ± standard deviation; one-way ANOVA with a Tukey post hoc analysis).