The increasing demand for flexible, wearable electronics, sensors, antennas and biomedical devices has led a team at Harvard’s Wyss Institute for Biologically Inspired Engineering and John A. Paulson School of Engineering and Applied Sciences (SEAS) to innovate an eye-popping new way of printing complex metallic architectures – as though they are seemingly suspended in midair. This laser-assisted direct ink writing method allows microscopic metallic, free-standing 3D structures to be printed in a single step without auxiliary support material. 

The ink composed of silver nanoparticles is sent through a printing nozzle and then annealed using a laser that applies just the right amount of energy to drive the ink’s solidification. The printing nozzle moves along x, y, and z axes and is combined with a rotary print stage to enable freeform curvature. In this way, tiny hemispherical shapes or spiral motifs made of silver wires less than the width of a hair can be printed in free space within seconds.
The printed wires exhibit excellent electrical conductivity. Localized laser heating enables electrically conductive silver wires to be printed directly on low-cost plastic substrates.