Stretchable electronics, which could be as soft and stretchable as human tissues, plays a vital role in the full integration of electronic components with human body. Based on it, next-generation bio-electrical interface, bio-mechanical and bio-chemical sensors could be built up to reliably exchange information with human body benefiting portable healthcare monitoring, disease diagnosis and therapy. The key issue to realize stretchable electronics is how to make thin-film conductors accommodate strain and keep conductive under large mechanical deformation. Several methods were proposed to achieve the mesh/mesh-like structure of conductive materials to fabricate stretchable conductors. These methods were all based on the active material design which may limit the functionality of the conductor. Herein, we report an alternative strategy, surface strain regulation, to tune the strain transferring process from the polymeric substrate to the metal thin film, achieving a randomly-distributed locally-concentrated mode of the strain in the meat film. Thus, the metal film can possess a network structure and keep conductive under large mechanical strain. Also, multiple functions can be achieved. High stretchability of ~ 400%, anti-notch and self-healing ability, high interfacial adhesion of ~ 2.5 MPa of metal film and polymer, and hundreds of square centimeters fabrication are achieved. Taking advantages of these superior properties, the stretchable conductor is successfully utilized as the bio-interface electrode to monitor the on-skin and in-vivo bio-electrical signals. Three-month implantation to wirelessly detect intramuscular myoelectric signals in rats was achieved. Besides, based on the concept of surface strain regulation, the sensitivity of the stretchable strain gauge was also significantly enhanced both for our new fiber-shape sensors and for new 3D stretchable strain sensors, benefiting the subtle vibration detection and body gesture monitoring. Our strategy is independent of the metal film formation mechanism and the conductive material used, and opens up a new way to fabricate stretchable conductors with superior properties. It also provides a new design platform of stretchable conductive materials. Based on it, many other new methods and stretchable bio-interface sensors could be further developed.
(See more at: Adv. Mater. 2017, adma.201704229; Adv. Mater. 2017, 29, 1603382; Adv. Mater. 2015, 27, 6230.)