Structuring and Shaping of Mechanically Robust and Functional Hydrogels Toward Wearable and Implantable Applications.

Hydrogels possess unique features such as softness, wetness, responsiveness, and biocompatibility, making them highly suitable for biointegrated applications that have close interactions with living organisms. However, conventional man-made hydrogels are usually soft and brittle, making them inferior to the mechanically robust biological hydrogels. To ensure reliable and durable operation of biointegrated wearable and implantable devices, mechanical matching and shape adaptivity of hydrogels to tissues and organs are essential. Recent advances in polymer science and processing technologies have enabled mechanical engineering and shaping of hydrogels for various biointegrated applications. In this review, we summarize polymer network structuring strategies at micro/nano scales for toughening hydrogels, and further discuss representative mechanical functionalities that exist in biological materials but are not easily achieved in synthetic hydrogels. We review three categories of processing technologies namely 3D printing, spinning, and coating for fabrication of tough hydrogel constructs with complex shapes, and the corresponding hydrogel toughening strategies are also highlighted. These developments enable adaptive fabrication of mechanically robust and functional hydrogel devices, and promote application of hydrogels in the fields of biomedical engineering, bioelectronics and soft robotics. This article is protected by copyright. All rights reserved.