Ultrafast electrohydrodynamic 3d printing with submicrometer resolution
- Autores: Ievgenii Liashenko
- Directores de la Tesis: Joan Rosell Llompart (dir. tes.), Andreu Cabot Codina (codir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: Ignacio González Loscertales (presid.), Jordi Grifoll Taverna (secret.), Eyal Zussman (voc.)
- Programa de doctorado: Programa de Doctorado en Nanociencia, Materiales e Ingeniería Química por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Additive manufacturing 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 precisely collected by too slow mechanical stages.
Here, we demonstrate that through controlling the voltage applied to electrodes located around the electrified jet, its trajectory can be continuously adjusted to control the jet deposition location, thus allowing to print arbitrary 2D micropatterns. Extensive experimental study revealed that electrostatically deflected EHD jet can reach lateral accelerations up to 10^6 m/s^2, greatly exceeding accelerations provided by best mechanical stages, which are limited to maximum 30 m/s^2. The jet was found to be surprisingly resilient and stable even when being deflected at frequencies as high as 10000 Hz. Using high-speed imaging we conducted a parametric analysis, revealing the effect of deflection signal parameters and setup configurations on the deflection angle.
To control the printing and to locate arriving jet into 2D patterns, a custom-made software was developed to generate jet-deflecting signals. Through such electrostatic jet deflection, 3D objects with submicrometer features were printed by stacking nanofibers on top of each other at layer-by-layer frequencies as high as 2000 Hz. The fast jet speed and large 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 other additive manufacturing techniques providing equivalent feature sizes.
Accurate printing entails that the jet speed must be closely matched by the printing speed (i.e. jet-deflection speed). This, however, requires that the EHD jet speed is stable and precisely measured, in the first place. Current methods to identify the jet speed are cumbersome and involve powerful/expensive microscope techniques (such as SEM). Here we address this issue by proposing a novel method to determine the jet speed via jet deflection, which does not rely on resolving individual fibers. Advantageously, simple optical imaging is enough to implement this method, and we demonstrate that it could be used in-situ to monitor the jet speed through image recognition.
When EHD jet can be made slow, such as in melt-based EHD jetting, XY stages are sufficient for printing structures that don’t comprise small curvature radii (sharp corners). While most previous research involved unsophisticated pattern designs based on straight lines and vertical stacking of fiber-layers, here we introduce a novel method enabling to significantly expand the variety of possible printed geometries. By updating the printing path for each deposited layer, we demonstrate prints with complex geometries, such as overhangs produced without support structures, branching and texturing of fiber-walls, as well as nature-inspired designs and tailored scaffolds. We show that this powerful design approach also can be used to control the mechanical properties of the printed structures, which can be beneficial in a spectrum of value-added applications.
