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Bionic ionic skin, having the ionic transduction and chromotropic traits of chameleons, along with multiple sensing, antibacterial, self-healing, and anti-freezing functions, is of great importance in a wide range of applications, such as flexible iontronics, health monitoring systems, and smart wearable devices. Although such advanced intelligence universally exists in natural organisms, these characteristics are rarely achieved in artificial materials simultaneously. By mimicking biological skin, here, a novel electromechanical and mechanochromic dual-sensing ionic skin (DSI-skin) with these superior functions is presented for visually monitoring human motions and expiration. The DSI-skin is mainly generated by the introduction of highly-substituted hydroxypropyl cellulose (H-HPC) forming liquid-crystal structures into a multifunctional ionic hydrogel (MFIH) containing Al3+ ions with ionic conduction. The resulting DSI-skin is the first to realize simultaneously sensitive dual-mode sensing of strain (gauge factor: 4.90; response time: 363 ms; mechanochromic sensitivity: 2.14 nm per %), pressure (sensitivity: 3.14 kPa−1; response time: 631 ms; mechanochromic sensitivity: 8.02 nm kPa−1), and humidity (fast response: 0.5 s; wide range: 30–90% RH) via the change of structure color and resistance. More importantly, owing to the highly synergistic effect of Al3+ ions and H-HPC, the DSI-skin is simultaneously integrated with handy color tuning (426–641 nm), outstanding antibacterial (log reduction > 3.43), excellent self-healing (85.0% efficiency), and anti-freezing (−15 °C) functions for the first time. These utility functions prolong the service life of the materials and expand their applications in many fields. Interestingly, the DSI-skin is also created with Zn2+ ions. Thus, this investigation provides insights into the design and fabrication of high-performance biomimetic materials. [ABSTRACT FROM AUTHOR]

Herein, a novel type of visible-light-induced dynamic covalent bond was developed based on aromatic Schiff base (ASB) bonds, and the prepared waterborne polyurethanes containing dynamic ASB bonds (ASB-WPU) exhibited a desirable self-healability (healing efficiency of 83.8%) after healing under a commercial LED table lamp for 24 hours (temperature of ∼25 °C). Meanwhile, high mechanical properties (tensile stress of 14.32 MPa and toughness of 64.80 MJ m−3) could also be obtained, demonstrating a good balance of room-temperature self-healability and high mechanical properties in our polymers. The imine metathesis of ASB bonds and the H-bonded interactions between urethane groups could afford the ultimate healing result simultaneously, in which the imine metathesis of ASB bonds triggered by visible light is the main factor. Furthermore, these ASB-WPU polymers could also be reprocessed under visible light with well recovered mechanical properties. We envision that this elaborate design philosophy, based on the readily available, clean, safe and easily manipulable visible light, could provide inspiration for preparing room-temperature self-healable and reprocessable polymers with high mechanical properties, which are urgently needed for next-generation smart materials. [ABSTRACT FROM AUTHOR]