4D printing of continuous fiber composites with embedded microcircuits: Synergistic enhancement of electrothermal actuation and load-bearing performance

To address the long-standing trade-off between heating efficiency and mechanical performance in electrothermally driven 4D printing of continuous carbon fiber-reinforced composites (CFRCs), we propose a dual-process hybrid printing strategy that integrates Electric-Field-Driven Microscale 3D Printing with Fused Deposition Modeling. This approach enables the seamless incorporation of continuous carbon fiber structural layers and silver-paste microcircuits, yielding embedded microcircuit CFRCs (EM-CFRCs). The embedded microcircuits significantly enhance electrothermal heating efficiency while maintaining the intrinsic strength of CFRCs. Experimental results show that EM-CFRCs achieve a heating rate of 5.9 °C/s, representing a 118.5 % improvement compared with conventional CFRCs, while the tensile modulus and structural stiffness remain nearly unchanged (increased by 1.5 %). We develop a predictive model based on multilayer beam theory that accurately captures the electrothermally induced deformation behavior and underlying mechanisms. Finally, we fabricate 4D-printed origami structures with complex geometries that demonstrate rapid actuation. These results highlight the potential of EM-CFRCs for aerospace deployable structures (e.g., solar sails), intelligent morphing components, and other advanced functional devices.