Particle-on-demand electrohydrodynamic printing from a reciprocating tip

While inkjet printing has revolutionized manufacturing of graphics and decorations, flexible electronics, and has enabled new additive manufacturing (AM) technologies, direct micro-scale deposition of metals remains challenging. Here, we present a particle-on-demand electrohydrodynamic printing approach, using a reciprocating tip mechanism that enables particles to be fed and ejected individually from an oil-coated membrane, and then printed to a target substrate. We examine the mechanism of printing using high-speed imaging and study the limiting mechanisms via controlled experiments with a range of particle sizes and materials, and then extract representative scaling laws for the ejection behavior. Based on this understanding, we demonstrate printing of two-dimensional patterns of stainless steel microparticles over a wide size range (50–700 μm particle diameter). With envisioned improvements to the tip geometry and particle-fluid interaction, and via parallelization, this particle-on-demand approach would be a versatile addition to high-resolution printing technologies for metals, including for manufacturing of intricate miniature components.