Programmable line-morphologies of material-extrusion 3D printed self-leveling inks with various apparent viscosity

Material-extrusion 3D printing is a promising technology for flexible electronics and rapid biomedical manufacturing. However, the complex interplay between printing process parameters and ink rheological properties makes the precise control of printed-line morphologies challenging. Existing morphology regulation methods often rely on inefficient empirical trial-and-error procedures, whereas recent approaches based on two-dimensional process phase diagrams remain limited by ink compatibility. To address this issue, we propose a printing morphology regulation strategy that integrates multiple printing parameters with the rheological behavior of different inks. The experimental results show that accuracy losses induced by changes in rheological properties can be partially compensated by optimizing the printing speed and nozzle height. Based on the extrusion states of printed lines, a three-dimensional phase diagram was developed. This diagram enables direct prediction of printed-line morphology using three independent parameters, namely normalized velocity, normalized height, and wall apparent viscosity. Moreover, the boundaries between different extrusion states in the phase diagram can be used to identify process windows for different ink materials. This work provides useful guidance for morphology regulation and rapid printing of material-extrusion 3D-printed sensors with diverse material systems and multifunctional designs.