Electric-field-driven jet deposition micro-nano 3D printing based on a single-plate electrode

Micro/nano-scale 3D printing has become one of the most popular research topics of additive manufacturing due to its wide range of applications in biological tissue engineering, flexible electronics, new energy, new materials, microelectromechanical systems, and many other fields. Recent work on micro/nano-scale 3D printing has presented a series of advanced techniques, such as microstereolithography, two-photon stereolithography, micro-laser sintering, electrochemical fabrication, and electrohydrodynamic (EHD) jet printing, to directly fabricate 3D micro/nano-scale structures. However, these existing technologies are still faced with challenges in realizing multi-material, macro/micro multi-scale 3D printing. Here, we propose a new electric-field-driven jet deposition micro/nano-scale 3D printing based on a single-plate electrode. Differing from the traditional EHD printing with two counter electrodes and our previously proposed electric-field-driven jet deposition 3D printing with a single nozzle electrode, this 3D printing is achieved using technology based on a self-induced electrostatic field. In this method, the nozzle is no longer used as the electrode, and only a single-plate electrode is needed to connect to the positive electrode of high voltage power supply while the negative electrode is directly grounded, which not only overcomes the mandatory requirement of nozzle conductivity in traditional EHD jet printing, but also solves the discharge and breakdown problem of printing conductive materials on the conductive substrate. The micro/nano-scale additive manufacturing by this proposed method can be achieved by combining the necking effect of Taylor cone formed by the self-induced electrostatic field between the printing material on the nozzle tip and the top surface of the substrate, and multi-layer precise stacking by the polarization charges attraction between the printing material and the already printed materials on the substrate. In addition, considering the high-resolution and high-efficiency printing of various materials with different viscosities, we propose two working modes, including the pulsed cone-jet mode and the continuous cone-jet mode. To prove the advantages and features of the proposed method, we carried out a series of research work systematically. Firstly, the printing mechanism is revealed through theoretical analysis and numerical simulation. The higher the conductivity of the single-plate electrode is and the lower the conductivity of the nozzle is, the greater the electric field intensity is. Then, the feasibility of printing with the nozzle (conductive steel nozzle and non-conductive glass nozzle), substrate (conductive copper plate, semiconductor silicon wafer, and insulating glass plate), and printing material (conductive silver paste and non-conductive polymer) has been verified by systematic experiments. Finally, three typical cases, micro “wall” structure of polylactic acid (PLA) with a line width of 1.139 μm and a high aspect ratio of 46.8:1, high-performance (transmittance of 90.17% and sheet resistance of 4.26 Ω/sq) transparent electrode made of high viscosity silver paste, and multi-layer 3D scaffold with a line width of 20 µm and a total height of 200 µm, have been printed successfully. The new method has been proved to have unique technical advantages in high-resolution printing, multi-material, and macro/micro multi-scale printing. Therefore, it provides a new solution with low cost and high universality for micro/nano-scale additive manufacturing and macro/micro cross scale 3D printing, especially in the field of biological tissue engineering and printing electronics.