Healing-on-demand composites based on polymer artificial muscle

• The PE copolymer artificial muscle from commercial fishing line exhibits repeatable actuation upon thermal activation.
• The composite based on polymeric muscle and solid healing agent could heal wide-opened crack efficiently.
• The coil spring index slightly affects the crack healing efficiency.
• The prestrain level of artificial muscle significantly affects the healing efficiency.

In this study, a new polymer artificial muscle based healing-on-demand composite was prepared and characterized. The composite consists of polymer artificial muscle made of commercial fishing line, thermoset host, and thermoplastic particle. Three-point bending damage to the beam sample can be healed even at a constrained boundary condition upon local heating, undergoing a close-then-heal procedure. The fractured beams were heated locally by a heat gun for 10 min. The healing efficiency was investigated at both free boundary condition and fixed boundary condition. The fast contraction of artificial muscle brings the fractured surfaces in spatial proximity; simultaneously, the melting thermoplastic agent fills the crack via capillary action and bonds the two fracture surfaces. With 60% prestrain of the reinforcing polymer artificial muscles (8% volume fraction), over 60% of healing efficiency was achieved at free boundary condition and 54% at fixed boundary condition after repeated damage-healing events. Due to its low cost, high healing efficiency, good compatibility, and excellent flexibility, we envision that the polymer artificial muscle will be a new device in designing next generation healing-on-demand polymer composite.

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