Ultrafast electrohydrodynamic 3D printing with submicrometer resolution

Identifier:  TDX:3108

Handle: https://hdl.handle.net/20.500.11797/TDX3108

Authors:  Liashenko, Ievgenii

Abstract:
Additive manufacturing (AM) technologies based on layer-by-layer deposition of material ejected from a nozzle provide unmatched versatility but are limited in terms of printing speed and resolution. Electrohydrodynamic (EHD) jetting uniquely allows generating submicrometer jets that can reach speeds above 1 m/s, but such jets cannot be deposited on a moving substrate with submicron accuracy even when using state-of-the-art mechanical stages, which are limited to accelerations below ~30 m/s^2. Here, we demonstrate a new printing approach in which the EHD jet trajectory can be continuously adjusted with lateral accelerations up to 10^6 m/s^2 via controlling voltages applied to electrodes positioned around the jet. Using high-speed imaging we have conducted a parametric analysis of how the deflection signal parameters and setup configurations influence the jet deflection. Custom-made software has been developed to generate jet-deflecting signals which control the jet to print 2D patterns, as well as 3D objects with submicrometer features. Such 3D objects have been printed by stacking nanofibers at layer-by-layer frequencies as high as 2000 Hz. The high jet speeds and layer-by-layer frequencies achieved translate into printing speeds up to 0.5 m/s in-plane and 0.4 mm/s in the vertical direction, which is three to four orders of magnitude faster than for other AM techniques providing equivalent feature sizes. We have also used electrostatic jet deflection to develop a novel method for determining the speed of EHD jets. Unlike all previous approaches, which rely on ex-situ high-resolution microscopy analysis of the printed fiber, our method is based on image recognition of predefined printed patterns, allowing in-situ monitoring of the jet speed. Finally, in an additional study on stage-based printing of slow EHD jets of polymer melts, we show that updating the printing path for each deposited layer enables to significantly expand the range of printable structures and thus manipulate their mechanical properties.