Large strain, tissue-like and self-healing conductive double-network hydrogel for underwater information transmission

Traditional information-transmission systems are poorly suited for rapid underwater communication because of their large size, high cost, and low flexibility, thereby inspiring the development of conductive hydrogel-based alternatives. However, the low extensibility and non-tissue-like flexibility of common hydrogels limit their applications in wearable devices for underwater use. As such, a self-healing double-network hydrogel with a large maximal strain (>1200 %), high conductivity (3.61 S m−1) and fatigue resistance, and tissue-like Young's modulus (<20.4 kPa) was prepared by freeze–thaw and solvent-replacement methods using polyvinyl alcohol and sodium alginate as the raw materials. In addition, the suitability of the resulting self-healing hydrogel for land and underwater applications, including sensing, communication, and energy collection, was demonstrated. The developed material enabled the (i) effective monitoring of multiple human physiological activities on land and (ii) highly consistent real-time underwater information transmission based on the use of the international Morse code at reasonable water temperatures (0–25 °C) and frequencies (1–5 Hz). Thus, this study presents a strategy for the development of soft materials as components of intelligent underwater electronic devices.