Three-Dimensionally Printed Stretchable Conductors from Surfactant-Mediated Composite Pastes.

A stretchable conductor is a critical prerequisite to achieve various forms of stretchable electronics. In particular, directly printable stretchable conductors have gathered considerable attention with recent growing interest in a variety of large-area, deformable electronics. In this study, we have developed a chemical pathway of incorporating a surfactant with a moderate hydrophilic-lipophilic balance in formulating composite pastes for printed stretchable conductors, with a possibility of a vertically stackable, three-dimensional printing process. We demonstrate that the addition of a nonionic surfactant, sorbitane monooleate (commonly called SPAN 80) in Ag flake-based composite pastes, allows a critical reduction in resistance variation under an external strain. The four-layer stacked, surfactant-added composite conductors show a resistance variation of merely 1.6 at a strain of 0.6 and excellent cycling durability over 1000 cycles. The effectiveness of the methods suggested in this study is demonstrated with basic light-emitting diode circuits and the thermal heating characteristics of stretchable conductors.