Extrusion-based Direct Write of Functional Materials From Electronics to Magnetics

New micro- and nanoscale fabrication methods are of vital importance to drive scientific and technological advances in electronics, materials science, physics and biology areas. Direct ink writing (DW) describes a group of mask-less and contactless additive manufacturing (AM), or 3D printing, processes that involve dispensing inks, typically particle suspensions, through a deposition nozzle to create 2D or 3D material patterns with desired architecture and composition on a computer-controlled movable stage. Much of the functional material printing and electronics area remains underdeveloped for this new technology. There is a need to understand and establish the advantages and shortcomings of extrusion-based DW over other AM technologies for various applications. Further, the integration of extrusion DW with other AM technologies, such as stereolithography (SLA), remains an active area of research. In this study, we performed a comprehensive study of the relationships between ink properties/machine parameters and the printed line dimensions, including parametric studies of the machine parameters, an in-nozzle flow dynamics simulation, and a preliminary 3D comprehensive flow dynamics simulation. We explored the boundary and possibilities of extrusion-based DW. We pushed the limit of DW printing resolution, solid content of nonspherical particles, and printed polymer-bonded magnets with the highest density and magnetic performance among all 3D printing magnet techniques. We optimized the design of DW ink from rheological, mechanical, and microscopic perspectives. We are one of the first experimentalists as of author’s knowledge to perform bimodal highly concentrated suspension rheology analysis using nonspherical particles. Great improvements in solid loading were achieved by using the best large-to-small particle size ratio and large particle volume ratio found. The data and analysis could provide a new standard and solid experimental support for functional material printing