High-resolution robotic electrohydrodynamic printing on rough, freeform surfaces via a self-stabilized electric-field technique

Abstract 3D conformal printing has emerged as one of the most promising strategies for constructing micropatterns or microstructures on large-area curved surfaces, enabling innovative applications such as electromagnetic metamaterials and electronic devices. The robotic conformal electrohydrodynamic (EHD) printing (RE-printing) technique is highly appealing in this respect because of its capability for submicron-scale patterning and compatibility with a broad range of ink viscosities. However, maintaining a steady electric field to ensure uniform deposition on curved and rough surfaces is challenging. Here, we propose an eye-inlaid printhead with a ‘neighborhood’ path compensation algorithm and a self-stabilizing electric field mechanism to significantly improve the accuracy of RE printing and find that a steady electric field strength, rather than a constant printing height, affects the uniformity of EHD-printed patterns more. This printhead integrates a camera for tangent plane positioning alongside a laser displacement sensor for measuring normal displacement and facilitates precise 3D positioning. The path compensation algorithm can maintain the electric field strength during the printing process by calculating the average local nozzle-to-substrate distance through in situ measurements of the printing height. This approach can not only stabilize the electric field but also reduce the robotic vibration caused by a fluctuating path on rough surfaces, reducing the electric field strength fluctuations from 20% to 5% and the vibration amplitude from 55 μm to nearly 0 μm compared with those of the traditional ‘point–to–point’ path compensation technique. In addition, it can adaptively correct substrate model errors, frame deviations, and robot motion inaccuracies. The mean absolute deviation of the nozzle-to-substrate distance can be reduced to 20 μm, presenting an enhancement in printing precision by 77.23% compared with that of the ‘point–to–point’ path compensation strategy. As a result, this approach achieves consistent line width and electrical resistance on curved substrates, supporting high-resolution conformal printing on surfaces with curvature radii as small as 1 mm and resolutions up to 5 μm. Finally, de-icing heaters have been conformally fabricated on an airplane wing, and their performance has been confirmed through subsequent de-icing trials. This approach promises a versatile solution for the RE printing of large-area 3D conformal electronic devices.