Table 1. Relative amounts of parts A and B of QGel 920 (by mass) and parts A and B of QGel 903 (both by Quantum Silicones) used to prepare silicone gels with different elastic moduli, E (in kPa).

E (kPa)	0.4	0.7	3.7	18	30	54	130
920A	1	1	1	1	1	1	1
920B	0.95	1	1.1	2	1	1	2
903A	–	–	–	–	0.13	0.19	0.22
903B	–	–	–	–	0.13	0.19	0.22

The elastic moduli were measured with accuracies of 5–10% by applying a known shear hydrodynamic stress using a microfluidic device and measuring the resulting shear strain [26]. The gels with E = 0.4–18 kPa were prepared using QGel 920 only, whereas the gels with E = 30–130 kPa were prepared with a mixture of QGel 920 and QGel 903 components. The experiments with HUVEC were only performed on gel substrates with E of 0.4, 3.7, 18, and 130 kPa.