Nanoscope 5 dimension 3100 microscope

PDMS substrates were generated as described previously (Zhou et al., 2015 (link), Zhou et al., 2016 ). In brief, PDMS pre-polymer and crosslinker (Sylgard 184; Dow Corning) were mixed in 10:1 ratio (w/w). PDMS substrates (9.5 × 9.5 cm, ∼1.5 mm thickness) were then stretched uniaxially to 130% of their original length. The samples were oxidized between 60 and 500 s in air plasma under pressure of 14 torr (0.2 mbar; Plasma Activate Flecto 10 USB). Removal of strain evoked wrinkle formation of different periodicities and height depending on the oxidation time. All samples were post-treated with air plasma for 10 min to ensure equal oxidation and Young's modulus values (62 MPa). AFM profiles were obtained using a Nanoscope V Dimension 3100 microscope (Veeco), whereas the stiffness analysis was performed on a Catalyst Nanoscoop V instrument (Bruker). Bruker SCANASYST-AIR (0.4 N m⁻¹) and NP (0.017 N m⁻¹) cantilevers made from silicon nitride with silicon tips were used before each measurement.