Fig. 2: Mechanical effect of the soft interlayer design in significantly improving the stretchability of functional layers on a much softer substrate.
a–d FEA simulation of the suppression of the stress concentration behavior given by a soft interlayer of three design parameters: modulus (Ef and Ei for Young’s modulus of film and interlayer, respectively), normalized by that of the functional film (b), thickness (Tf and Ti for the thickness of film and interlayer respectively), normalized by that of the functional thin film (c), and delamination condition, delaminated area around the notch in the film normalized by notch area (d) (stress is normalized by the modulus of the functional film). e The soft interlayer design is applied to a stretchable polymer semiconductor film for the integration on an ultrasoft Ecoflex substrate, by using a SEBS film as the interlayer. The moduli of the three layers are labeled in the schematic image. f Representative optical images of cracks formed in the stretchable semiconductor films with the SEBS interlayers of varied thicknesses (scale bar 20 μm). g Soft contact lamination method for the measurement of these semiconducting films on an ultrasoft substrate during stretching. h Representative evolvement of the charge-carrier mobility of these stretchable semiconductor films with different SEBS interlayer thicknesses, during the stretching from 0 to 100% strain.
