Self-Healing, Recyclable, and Degradable Castor Oil-Based Elastomers for Sustainable Soft Robotics

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 fossil-derived 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.