Development of Electrohydrodynamic Printing Technology with Einzel Lens Focusing

Abstract

Additive manufacturing has several advantages over conventional subtractive fabrication techniques such as CNC machining, including limited waste and the ability to build complicated structures using fewer processing steps. Recently, a cost-effective, versatile method of high-resolution printing called electrohydrodynamic printing has been developed. With this technique, droplets are deposited from a tip by applying an external electric field. This method allows for spatial resolution in the hundreds of nanometers when used in a drop-on-demand mode of operation. However, this mode has the drawback of relatively slow deposition rates. To increase the rate of deposition, it is desired to deposit the droplets using a continuous spray, which is called the cone jet mode. However, this mode of operation has a much lower resolution because of the space charge effect (lateral spread of the stream of charged droplets from Coulomb repulsion). The primary goal of this research project was to develop an electrohydrodynamic printing system with a focusing element to allow printing at much higher deposition rates than the drop-on-demand mode while maintaining reasonably high lateral resolution. After modeling different focusing systems, an Einzel lens was determined to be the optimal focusing element. A custom electrohydrodynamic printing system with a three-element Einzel lens was fabricated and tested with 10% polyethylene glycol solution. Droplets with a lateral diameter of ~1 μm after drying were successfully deposited. The incorporation of the Einzel lens resulted in an order of magnitude improvement in lateral resolution of the spray.