Highly Conductive Liquid Metal Emulsion Gels for Three-Dimensionally Printed Stretchable Electronics.

Gallium-based liquid metals are promising for stretchable electronics due to their inherent deformability and excellent conductivity. However, the lack of a scalable and automated fabrication process has limited their practical applications. This study introduces a two-step method to create liquid metal emulsion gels suitable for 3D printing, characterized by densely packed liquid metal microcapsules within polymer matrices. The resulting emulsion gel demonstrates favorable rheological properties for 3D printing and minimal shrinkage through solidification. With a substantial fraction of sizable microcapsules, the printed features can be activated into compliant conductors with exceptional conductivity of ≈2.2× 10⁴ S cm^-1 and an ultrahigh stretchability of up to ≈1000% strain. Stretchable lighting emitting diode displays and near field communication tags are successfully fabricated through 3D printing to demonstrate the practicality of liquid metal microcapsule gels. These developments provide a versatile platform to design liquid metal inks for printed stretchable electronics.