An increasing demand for flexible, wearable electronics, sensors, antennas and medical devices has led researchers at the Wyss Institute to develop a laser-assisted direct ink writing method that allows microscopic metallic, free-standing 3D structures to be printed without auxiliary support material.

The method can produce not only sweeping curves and spirals but also sharp angular turns and directional changes, opening up near limitless new potential applications in electronic and medical devices that rely on customized metallic architectures.

The printing process uses an ink composed of silver nanoparticles, sending it through a printing nozzle and then annealing it by employing a precisely programmed 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 silver wires less than the width of a hair can be printed into virtually any 3D shape in free space within seconds.

The printed wires exhibit excellent electrical conductivity, almost matching that of bulk silver.

When compared to conventional 3D printing techniques used to fabricate conductive metallic features, laser-assisted direct ink writing is not only superior in its ability to produce curvilinear, complex wire patterns in one step, but the localized laser heating also enables electrically conductive silver wires to be printed directly on low cost substrates.