Direct 3D Printing of Hybrid Nanofiber-Based Nanocomposites for Highly Conductive and Shape Memory Applications.

Three-dimensional (3D) printing with conductive polymer nanocomposites provides an attractive strategy for the "on-demand" fabrication of electrical devices. This paper demonstrates a family of highly conductive multimaterial composites that can be directly printed into ready-to-use multifunctional electrical devices using a flexible solvent-cast 3D printing technique. The new material design leverages the high aspect ratio and low contact resistance of the hybrid silver-coated carbon nanofibers (Ag@CNFs) with the excellent 3D printability of the thermoplastic polymer. The achieved nanocomposites are capable of printing in open air under ambient conditions, meanwhile presenting a low percolation threshold (i.e., <6 vol %) and high electrical conductivity (i.e., >2.1 × 10 S/m) without any post-treatments. We further find that this hybrid Ag@CNF-based nanocomposite shows a quick and low-voltage-triggered electrical-responsive shape memory behavior, making it a great candidate for printing electroactive devices. Multiple different as-printed Ag@CNF-based highly conductive nanocomposite structures used as high-performance electrical devices (e.g., ambient-printable conductive components, microstructured fiber sensors, flexible and lightweight scaffolds for electromagnetic interference shielding, and low-voltage-triggered smart grippers) are successfully demonstrated herein. This simple additive manufacturing approach combined with the synergic effects of the multimaterial nanocomposite paves new ways for further development of advanced and smart electrical devices in areas of soft robotics, sensors, wearable electronics, etc.