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Self-healing polymers can address the damage susceptibility in soft robotics. However, in most cases, their healing requires a heat stimulus, provided by an external device. This paper presents a self-healing soft actuator with an integrated healable flexible heater, functioning as the stimuliproviding system. The actuator is constructed out of thermoreversible elastomers that are crosslinked by the Diels-Alder (DA) reaction, which provides the healing ability. The heater is manufactured from a DA-based composite network filled with 20 wt% carbon black to provide electrically conductive properties for resistive Joule heating. The flexibility of the heater does not compromise the actuator performance upon integration and the self-healing properties of both heater and actuator allow for damage repair. This includes very large damages, as both heater and actuator can recover (near 100%) from being cut completely in two pieces, using Joule heating at 90 °C with a bias voltage of about 30 V. The embedded heater avoids the need for external intervention in the healing process, and provides healing quality assessment and a healing ondemand mechanism, paving the way for an optimum healing solution of damage resilient soft robots that require heat as a healing stimulus.

No abstract

Self-healing polymers render their life cycle more sustainable by recovering their properties upon healing. Intrinsic self-healing polymers can be recycled, which further reduces waste production. Yet, despite these intrinsic benefits, several sustainability issues remain largely neglected, including the use of fossilderived materials, hazardous chemicals, and material management at the end of its life. Herein, we report a series of castor oil-based self-healing elastomers that account for these challenges and show improved mechanical and self-healing capabilities compared to the other bio-based self-healing materials. Castor oil was functionalized using a simple, one-pot, solventless synthesis from renewable resources and cross-linked by Diels−Alder cycloaddition. They can be reprocessed and recycled or hydrolytically degraded at the end of their service life. The mechanical properties of the materials can be tuned (Young's modulus 0.5−20 MPa), with a fracture strain of up to 487%. A fracture strain of 100% could already be recovered after just 60 s at room temperature and 75% of the mechanical properties after just 24 h. By taking advantage of these properties, a soft pneumatic gripper has been developed, capable of healing autonomously, which is fully recyclable and degradable. Hence, we provide a sustainable alternative for soft robotic applications and for self-healing elastomers in general.

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