Development of novel multi-responsive 4D printed smart nanocomposites with polypyrrole coated iron oxides for remote and adaptive transformation.

Four-dimensional (4D) printing, a state-of-the-art additive manufacturing technology, enables the creation of objects capable of changing shape, properties, or functionality over time in response to external stimuli. However, the lack of effective remote control and reliance on a single actuation method pose significant challenges, limiting its applications in various fields. This study aims to address these limitations by developing a novel multi-responsive nanocomposite. By coating near-infrared light (NIR)-responsive polypyrrole (PPy) onto the surface of magnetic iron oxide (Fe₂O₃) nanoparticles (NPs), multi-responsive PPy@Fe₂O₃ NPs were synthesized. Doping PPy@Fe₂O₃ into a thermo-responsive shape memory polymer (SMP) matrix created a nanocomposite with excellent NIR and magnetic responsiveness, enabling dynamic, remote-controlled shape transformation of printed objects with precise timing and positioning using NIR and a magnetic field. Using the nanocomposite, a proof-of-concept semi-tubular construct was fabricated to evaluate its controllable transformation capability and assess the potential for modulating neural stem cell (NSC) behaviors. Furthermore, three proof-of-concept smart robots with distinct features were designed and fabricated for cargo delivery in diverse scenarios and different purposes. Importantly, all complex operations of these robots were remotely controlled using NIR illumination and an external magnetic field. This novel approach demonstrates significant progress in addressing the key challenges of remote control and actuation in 4D printing, highlighting its potential for enhanced versatility and functionality across various applications.