Development of process control and material for micro/nano-scale electrohydrodynamic inkjet manufacturing

Abstract

This dissertation introduced the development of material and control for electrohydrodynamic inkjet (e-jet) printing system. They include: 1) a method to fabricate functional devices; 2) a method to develop novel material for shielding radiation; 3) a method to monitor the e-jet printing process to reduce defects; 4) a method to predict the dimension of fabricated patterns.Firstly, e-jet printing has been recognized as a novel micro/nano-scale direct writing manufacturing technique. Delicate patterns could be printed on various flexible substrates with conductive silver nanoink material. It is still a challenge to fabricate customized micro/nanoscale biomarkers for the application in biomedical area. Meanwhile, although the X-ray responses of bulk silver have been investigated, the characterization of silver nanoink is still unknown. Both delicate patterns and multi-layer samples were fabricated to demonstrate the robustness of fabricating the X-ray marker by e-jet printing. In this study, microstructures of silver nanoink were printed and characterized by X-ray. In the future, this effective e-jet printing method will enable the tracking of significant devices in the biomedical area such as customized drug delivery system. Secondly, with the development of e-jet printing, more materials were explored to satisfy applications such as aerospace. Tungsten material has the capability of shielding massive X-ray. But there is no tungsten ink in the market for the fabrication of micro/nano-scale shield patterns. In aerospace, critical areas of electronics need to be protected to avoid radiation damage from space. Meanwhile, weight is one of the vital factors to be considered in this situation. Thus, it is required to develop a lightweight and effective shielding device to protect the electronics from harmful X-ray radiation. The methods of synthesis and evaluation of new ink materials for e-jet printing system would be one of the most critical research areas in this field. Thirdly, random defects could happen during the e-jet printing process due to the hardware system's limited performance and environmental factors. It is necessary to develop an in-situ monitoring system to detect the possible defects. Machine vision and laser scalar systems were proposed and established to monitor the printing process, and predict the dimension of printed patterns. These methods have proposed automated image processing algorithms to avoid the massive, time-consuming, and reliable measured data to monitor the e-jet printing process. It was demonstrated to be a robust and practical approach to contribute to the automation of the e-jet printing technique. Fourthly, with the rapid evolvement of the