Velocity-Adaptive Electrohydrodynamic Printing for Microscale Conformal Circuits on Freeform Curved Surfaces

High-resolution printing of conformal circuits on curved surfaces is critical to achieving structure-function integration in electromechanically coupled components like antennas. However, existing printing techniques such as inkjet or extrusion-based printing fail to conformally deposit microscale conductive circuits on freeform curved surfaces with curvature variations. Herein, we propose an innovative electrohydrodynamic (EHD) printing strategy that can adaptively adjust the nozzle-to-substrate distance and printing velocity according to surface curvature, enabling the direct printing of conductive circuits on diverse curved surfaces with microscale resolution and high uniformity. A path-planning algorithm is developed based on the target surface morphology captured from the scanned 3D point cloud data. The printing velocity at each point along the printing trajectory can be adaptively calculated according to the Gaussian curvature and mapping angle. This strategy makes the deposition rate well match the stage's moving speed, facilitating the uniform EHD printing of conductive patterns with a line width of 39.31 ± 4.06 μm on different surfaces with curvatures ranging from 10 to 2000 m^-1. As a proof of concept, a uniform snowflake pattern with good conductivity is EHD printing on a naturally insulated conch with the smallest line width of 35.74 ± 4.24 μm. A metasurface with microscale conductive feature arrays is specially printed on a radome-shaped polymeric surface, exhibiting dual-band cloaking and reduced scattering characteristics compared to conventional metal substrates. We envision that the proposed velocity-adaptive EHD printing technique would mature into a promising and versatile tool to fabricate microscale conductive circuits on diverse curved surfaces for potential applications in conformal antennas and functional sensing or electromagnetic surfaces.