Omnidirectional Strain‐Independent Organic Transistors Integrated onto an Elastomer Template with a Spontaneously Formed Fingerprint‐Mimicking Microtopography

Abstract

Here, a stretchable organic field-effect transistor (OFET) that exhibits constant electrical performance irrespective of the strain direction is demonstrated. The device is integrated onto an elastomer template with randomly oriented wrinkles on its surface; these wrinkles are spontaneously formed because of the differences in the thermal–mechanical properties of the plastic layer and the underlying elastomer. To achieve this microtopography, a relatively hard polymer, Parylene C, is ad-deposited onto an elastomer blended with polydimethylsiloxane and Ecoflex, resulting in PD-flex. Consequently, this microtopography offers stable device operations of a dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene OFET array under 5% elongation irrespective of strain direction. Furthermore, the electrical performance is highly stable during 10 000 cycles of uniaxial strain, as verified by negligible modulation of the device's field-effect mobility, threshold voltage, and drain-current maximum. This approach allows nonstretchable device components to be relevant to stretchable electronics. More importantly, it is highly compatible to device alignment and provides stability under various kinds of mechanical deformations. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim