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Tough interface-enabled stretchable electronics using non-stretchable polymer semiconductors and conductors

Lihua Jin's picture

By Jiheong Kang, Jaewan Mun, Yu Zheng, Masato Koizumi, Naoji Matsuhisa, Hung-Chin Wu, Shucheng Chen, Jeffrey B.-H. Tok, Gae Hwang Lee, Lihua Jin & Zhenan Bao

Semiconducting polymer thin films are essential elements of soft electronics for both wearable and biomedical applications1–11. However, high-mobility semiconducting polymers are usually brittle and can be easily fractured under small strains (<10%)12–14. Recently, improved intrinsic mechanical properties of semiconducting polymer films have been reported through molecular design 15–18 and nanoconfinement19. Here we show that engineering the interfacial properties between a semiconducting thin film and a substrate can significantly delay micro-crack formation in the film. We present a universal design strategy that involves covalently bonding a dissipative interfacial polymer layer, consisting of dynamic non-covalent crosslinks, between a semiconducting thin film and a substrate. This enables high interfacial toughness between the layers, suppression of delamination, and delocalization of strain. As a result, crack initiation and propagation are significantly delayed to much higher strains. Specifically, the crack onset strain of a high-mobility semiconducting polymer thin film improved from 30% strain to 110 % strain without any noticeable microcracks. Despite the presence of a large mismatch in strain between the plastic semiconducting thin film and an elastic substrate after unloading, the tough interface layer helped maintain bonding and exceptional cyclic durability and robustness. Furthermore, we found that our interfacial layer reduces the mismatch of thermal expansion coefficients between different layers. This approach can improve crack onset strain of various semiconducting polymers, conducting polymers and even metal thin films.

Published in Nature Nanotechnology

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