High resolution electrohydrodynamic 3D printing for high viscosity materials

With rapid growth of demand in microelectronic industry and biotechnology, traditional manufacturing methods cannot satisfy the developing needs of these industries. This thesis introduces the development of a new printing technology, called electrohydrodynamic (EHD) inkjet printing. The process involved, known as "electrospray in the cone-jet mode", can produce a thin and intact jet without the need to miniaturize the nozzle. The first aim of the thesis is to investigate essential science and physics of cone-jet formation and study effects of operating parameters (electric potential and flow rate), material properties (surface tension, electric conductivity and viscosity) and geometry parameters (nozzle size and height between positive and ground electrode). The second aim is to explore a novel multi-material and multifunction additive manufacturing (AM) system. The new AM system has the following features: (1) Exchangeable printing nozzles for materials with different viscosities; (2) A pair-electrode with fixed distance to print layer built-up 3D objects; (3) The resolution of moving stage up to 0.5[mu]m; (4) Precise controllable heating, fluid and voltage supply unit. Thirdly, an innovate printing head is designed to integrate air focusing flow (AFF) method into EHD printing process. The advantages of AFF include high yielding rate, elimination of solid friction, and insensitive to material properties.