Polythiophene Nanofibril Bundles Surface‐Embedded in Elastomer: A Route to a Highly Stretchable Active Channel Layer

: A stretchable polymer channel layer for organic field-effect transistors is obtained by spin-coating a blend solution of polythiophene and rubber polymer. A network of the polythiophene nanofibril bundles surface-embedded in the rubber matrix allows large stretchability of the polythiophene film layer.