Nanodroplet Flight Control in Electrohydrodynamic Redox 3D Printing

Abstract

Electrohydrodynamic 3D printing is an additive manufacturing technique with enormous potential in plasmonics, microelectronics, and sensing applications thanks to its broad material palette, high voxel deposition rate, and compatibility with various substrates. However, the electric field used to deposit material is concentrated at the depositing structure, resulting in the focusing of the charged droplets and geometry-dependent landing positions, which complicates the fabrication of complex 3D shapes. The low level of concordance between the design and printout seriously impedes the development of electrohydrodynamic 3D printing and rationalizes the simplicity of the designs reported so far. In this work, we break the electric field centrosymmetry to study the resulting deviation in the flight trajectory of the droplets. Comparison of experimental outcomes with predictions of an FEM model provides new insights into the droplet characteristics and unveils how the product of droplet size and charge uniquely governs its kinematics. From these insights, we develop reliable predictions of the jet trajectory and allow the computation of optimized printing paths counterbalancing the electric field distortion, thereby enabling the fabrication of geometries with unprecedented complexity.

Direct In‐ and Out‐of‐Plane Writing of Metals on Insulators by Electron‐Beam‐Enabled, Confined Electrodeposition with Submicrometer Feature Size

“…The operando observation of the printing process will further help to understand the growth dynamics and optimize path planning and droplet guiding-possibly enabling a simulation-guided deposition model that has been applied successfully to e-beam induced deposition of complex 3D nano-geometries. [32] Important for an application of the technique, the here demonstrated, direct deposition on insulators proofs compatibility of the EHD-RP process with all classes of materials (deposition on semiconductors was shown earlier [26] ). In concert with recent demonstrations of the growth of semiconductors, [28] as well as binary and ternary alloys [30] by EHD-RP, the extension to insulating substrates may constitute an important step toward a sub-micrometer, multimaterial AM technology for the deposition of functional, multimaterial devices.…”

“…It has previously unlocked the growth of structures with very high aspect ratios [26] or complex 3D geometries that are reproduced with high accuracy when field-guiding of droplets is properly taken into account. [32] Further, we see no fundamental limitation of the build space other than the range of the stages and the size of the vacuum chamber. The operando observation of the printing process will further help to understand the growth dynamics and optimize path planning and droplet guiding-possibly enabling a simulation-guided deposition model that has been applied successfully to e-beam induced deposition of complex 3D nano-geometries.…”

“…The variability of diameter and shape of deposited pillars is notably larger than in previous studies of EHD-RP in ambient conditions that demonstrated reproducible growth of various geometries. [26,28,32] We attribute the observed variations to non-ideal deposition parameters that should be optimized in the future (level of contamination, vibrations of the setup, or beam current).…”