It is highly desirable, although very challenging, to develop self‐healable materials exhibiting both high efficiency in self‐healing and excellent mechanical properties at ambient conditions. Herein, a novel Cu(II)–dimethylglyoxime–urethane‐complex‐based polyurethane elastomer (Cu–DOU–CPU) with synergetic triple dynamic bonds is developed. Cu–DOU–CPU demonstrates the highest reported mechanical performance for self‐healing elastomers at room temperature, with a tensile strength and toughness up to 14.8 MPa and 87.0 MJ m−3, respectively. Meanwhile, the Cu–DOU–CPU spontaneously self‐heals at room temperature with an instant recovered tensile strength of 1.84 MPa and a continuously increased strength up to 13.8 MPa, surpassing the original strength of all other counterparts. Density functional theory calculations reveal that the coordination of Cu(II) plays a critical role in accelerating the reversible dissociation of dimethylglyoxime–urethane, which is important to the excellent performance of the self‐healing elastomer. Application of this technology is demonstrated by a self‐healable and stretchable circuit constructed from Cu–DOU–CPU.

Stretchable conductive fibers are key elements for next‐generation flexible electronics. Most existing conductive fibers are electron‐based, opaque, relatively rigid, and show a significant increase in resistance during stretching. Accordingly, soft, stretchable, and transparent ion‐conductive hydrogel fibers have attracted significant attention. However, hydrogel fibers are difficult to manufacture and easy to dry and freeze, which significantly hinders their wide range of applications. Herein, organohydrogel fibers are designed to address these challenges. First, a newly designed hybrid crosslinking strategy continuously wet‐spins hydrogel fibers, which are transformed into organohydrogel fibers by simple solvent replacement. The organohydrogel fibers show excellent antifreezing (< ‐80 °C) capability, stability (>5 months), transparency, and stretchability. The predominantly covalently crosslinked network ensures the fibers have a high dynamic mechanical stability with negligible hysteresis and creep, from which previous conductive fibers usually suffer. Accordingly, strain sensors made from the organohydrogel fibers accurately capture high‐frequency (4 Hz) and high‐speed (24 cm s−1) motion and exhibit little drift for 1000 stretch–release cycles, and are powerful for detecting rapid cyclic motions such as engine valves and are difficult to reach by previously reported conductive fibers. The organohydrogel fibers also demonstrate potential as wearable anisotropic sensors, data gloves, soft electrodes, and optical fibers.

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The bio-integrated electronics industry is booming and becoming more integrated with biological tissues. To successfully integrate with the soft tissues of the body (eg. skin), the material must possess many of the same properties including compliance, toughness, elasticity, and tear resistance. In this work, we prepare mechanically and biologically skin-like materials (PSeD-U elastomers) by designing a unique physical and covalent hybrid crosslinking structure. The introduction of an optimal amount of hydrogen bonds significantly strengthens the resultant elastomers with 11 times the toughness and 3 times the strength of covalent crosslinked PSeD elastomers, while maintaining a low modulus. Besides, the PSeD-U elastomers show nonlinear mechanical behavior similar to skins. Furthermore, PSeD-U elastomers demonstrate the cytocompatibility and biodegradability to achieve better integration with tissues. Finally, piezocapacitive pressure sensors are fabricated with high pressure sensitivity and rapid response to demonstrate the potential use of PSeD-U elastomers in bio-integrated electronics.

Triboelectric nanogenerator (TENG) devices have gotten great attention in wearable power sources and physiological monitoring. However, the complicated assembling and the molding processing retard their applications. Here, 3D-printed TENGs (3DP-TENGs) are designed and readily fabricated by a single integrated process without additional assembling steps. The TENGs contain poly(glycerol sebacate) (PGS) and carbon nanotubes (CNTs) as the two electrification components. Conductive CNTs also serve as electrodes. Elastic PGS matrix makes TENGs intrinsically responsive to biomechanical motions leading to robust energy outputs. The hierarchical porous structure of the 3DP-TENG results in higher output efficiency than traditional molded microporous TENG counterparts. TENGs with different 3D shapes are readily fabricated for different applications. The 3DP-TENG insole efficiently harvests biomechanical energy to drive electronics. A ring-shaped TENG acts as a self-powered sensor to monitor the motion of fingers. Furthermore, the use of bio-based and biodegradable PGS matrix combining with efficient recycle of CNTs makes 3DP-TENGs favorable from sustainable perspective. This work provides a new strategy to design and tailor 3D TENGs that will be very useful for diverse electronic applications.

Wearable electronics have become an important part of daily lives. However, its rapid development results in the problem of electronic waste (e‐waste). Consequently, recyclable materials suitable for wearable electronics are highly sought after. In this study, a conductive recyclable composite (PFBC) is designed based on a dynamic covalently cross‐linked elastomer and hierarchical hybrid nanofillers. The PFBC shows excellent wide‐ranging properties including processability, elasticity, conductivity, and stability, which are superior to previous materials used for recyclable electronics, and exhibits outstanding mechanical properties and environmental tolerance including high temperature, high humidity, brine, and ethanol owing to its covalent cross‐linking. Reversible dissociation of Diels–Alder networks allows for convenient processing and recycling. After three recycles, the toughness of the PFBC remained at 10.1 MJ m−3, which is conspicuous among the reported recyclable electronic materials. Three types of PFBC‐based wearable electronics including a triboelectric nanogenerator, a capacitive pressure sensor, and a flexible keyboard, are successfully 3D printed with excellent performance. The PFBC possessed both recyclability and degradability, the combination of which provides a new way to reduce e‐waste. This is the first work to recycle electronics using direct 3D printing and presents promising new design principles and materials for wearable electronics.

Three-dimensional (3D) printing thermosets offers great potential to customize sophisticated constructs for a myriad of applications.

The rapid development of flexible electronics has resulted in serious pollution in the form of electronic waste. Accordingly, recyclability is highly desirable for these devices, but this remains a significant challenge. A dynamically hybrid crosslinked polyurethane (FPU) elastomer is designed in this study to address this challenge. Distinctive Diels-Alder adducts with suitable dissociation and reassociation dynamics are designed as crosslinking units to provide an efficient time frame for recycling. FPU is maintained in a state with a low crosslinking density after heating at 120 °C for 5 min. FPU-based electronics can therefore be dissolved in chloroform under ambient conditions to separate the electronic components and polymers for the refabrication of new electronic devices. This is the first reported thermoset elastomer that can be completely recycled at room temperature without chemical treatment to decompose the polymer chain. The design concept is applied by demonstrating the fabrication by recycling of different FPU-based flexible electronic devices: position sensor, flexible keyboard, and motion sensor. Furthermore, the FPU has many advantages as a material for flexible electronics in terms of its biomimetic mechanical properties, room-temperature self-healing, and facile processability. This study provides promising new design principles to develop materials for promoting sustainable flexible electronics.