Fig. 4: Mechanical flexibility and conformability.

a Schematic procedure to induce wrinkling in the ultrathin transistor sample (left) and optical picture of the wrinkled transistor device (right, scale bar 100 µm); the white box indicates the point in which a specific curvature analysis is performed as reported in (b). b Merged optical image, topographic and curvature mapping of a wrinkled sample acquired in the active area of the transistor by optical profilometry at ×150 magnification (scale bar 10 µm); the curvature (K) mapping is calculated by optical profilometry data (details in Supplementary Figs. 8–9). c Transfer characteristic curves for an ultrathin device in saturation mode when recollected on a prestretched PDMS substrate (flat sample, black line) and after PMDS relaxation, which induces strong buckling on the surface (wrinkled sample, red lines). d A film sample containing an array of devices adhering to the skin to demonstrate conformal adhesion and a high level of transparency.