Smart composite origami with reconfigurable permanent states via electrothermal-based annealing

Electrothermally actuated composite origami structures integrate versatile shape-morphing with high load-bearing capacity, yet their precise regulation typically necessitates complex multi-physics modeling, hindering practical deployment. Here, an annealing-assisted electrothermal four-dimensional printing strategy is reported to address these challenges. This strategy employs co-extrusion printing to fabricate continuous carbon fiber-reinforced thermoplastic polymer composite hinges with surface-integrated conductive films, establishing localized and uniform Joule-heating pathways. The permanent state of these hinges can be reconfigured by annealing at a fixed, prescribed folding angle near 80 °C, a process driven by molecular chain relaxation and oriented crystallization. Unlike solutions requiring continuous external stimuli, these structures deploy into predefined configurations via a single electrothermal activation, maintaining their geometry and load-bearing capacity post-cooling without requiring sustained electrical heating to hold the shape. Furthermore, quantitative correlations between annealing parameters and permanent hinge angles are established to enable inverse design tailored to specific functional requirements. Finally, the strategy is validated through the demonstration of frequency-tunable vibration isolators, stiffness-programmable metamaterials, and vision-guided adaptive grippers, underscoring its potential for advanced engineering applications.