Stabilizing Rayleigh-Plateau Instability in 3D Printing of Newtonian Liquids Embedded in Viscoplastic Matrices*

The Rayleigh-Plateau instability, a universal phenomenon where a liquid column breaks into droplets due to surface tension, must be considered for stable printing in embedded 3D printing processes. In general, both the printed liquid and the surrounding liquid need to be viscoplastic to prevent this instability. However, when printing liquids with low mechanical properties, such as biomaterials or Newtonian liquids, the critical conditions to prevent the instability remain unclear. In this study, we investigate printing Newtonian liquids, specifically silicone oil and liquid metal, into a viscoplastic matrix, focusing on the critical role of the yield stress of the supporting matrix. By varying the concentration of the surrounding liquid and the types of printing liquids, we found the relationship between yield stress and interfacial tension in mitigating these instabilities. Additionally, we studied how the diameter of the printed liquid affects its stability, showing that the optimal conditions depend on the printing resolution. We believe that this research broadens the potential applications of Newtonian embedded printing, enabling the creation of 3D circuits using liquid metal and providing a foundational framework for printing biomaterials and other fluids with low viscoplasticity, thereby enhancing the versatility of embedded 3D printing techniques.