Revolutionizing flexible Electronics: Integrating liquid metal DIW 3D printing by bimolecular interpenetrating network

Abstract

Ultra-flexible liquid metal (LM) composites have significant potential in various applications, including soft robotics, wearable electronics, and human–machine interactions. This burgeoning field necessitates mass production at a critical scale alongside highly accurate and fully automated technology. In this study, a direct ink-writing (DIW) 3D all-printing strategy was developed, integrating cellulose nanofibrils (CNF), water-based polyurethane (WPU), and LM to fabricate high-performance LM-based electronic films, circuits, and diverse 2D or 3D structures. The stable ternary interface system was investigated, and bimolecular interpenetrating network system of CNF/WPU significantly enhanced the flexibility, reducing LM damage, mitigation, and leakage. Moreover, the systematic control of the DIW all-printing process facilitated high-resolution and excellent printability. The super-flexibility and precise electrical conductivity were demonstrated by investigating bending deformation and recyclable electrical signals. Electronics based on ultra-flexible LM, with a high LM content (78.0%), exhibited an accurate electrical response to bending deformation, extraordinary flexibility, and recyclable durability (up to 500 cycles). Notably, the all-printed system facilitates the complete automation, complex structuring, and precise moulding of various appliances. DIW 3D all-printing of LM has the potential to create complex conductive architectures for programmable and multi-material LM-based electronics, meeting high-precision, large-scale, and automated production requirements.