The morphology regulation mechanism of microdroplet printing based on heterogeneous wettability surfaces

Abstract

Microdroplet printing technology can effectively realize the precision preparation of complex electronic devices at the micro-scale, relying on the mutual interaction between the tiny micro-droplets, which can improve the organizational microstructure of the fabricated parts and effectively enhancement the mechanical properties of the fabricated parts. In this paper, the interaction process between micro-droplets and patterned wetted modified surfaces during the microdroplet printed process is studied based on the coupled level collective integral number method (CLSVOF) and equivalent heat capacity method. The influence of patterned schemes for non-uniform surface wetting modification, regional wetting differences and impingement process parameters on the impingement spreading flow of metal droplets and their heat transfer cooling process is investigated. The evolution mechanisms of the droplet geometry and the distribution characteristic of the droplet internal temperature and heat flow density during the impingement spreading process are discussed. The optimization mechanism of heterogeneous wetting modified surfaces for molten droplet forming is revealed. The results show that the four-way homogeneous pattern modification scheme can effectively improve the microdroplet stabilization rate and enhance the preparation efficiency by ensuring the shape size and positioning accuracy. Four three-phase contact lines morphology patterns for the equilibrium state of droplets, namely, circular, rectangular, concave shape and rhombic, were obtained by adjusting the wetting differences between the areas. A scheme to regulate the surface behavior of printed microdroplets with lyophilic high-adhesion region to anchor the droplets and lyophobic low-adhesion environment to provide a physical barrier to confine the droplet morphology was developed. In addition, the pattern modification scheme has an obvious optimization effect for the droplet forming and its heat exchange process in the process of metal droplet printing. Basis on the ensuring the radial dimensional accuracy and sphericity of the molten droplet molding, the rebound and oscillation behavior of the molten droplet is effectively suppressed. The stabilizing efficiency of droplet printing is greatly enhanced and further improves the heat transfer performance of the droplet. The results further enrich the theory of precise regulation of the dynamic behavior of droplet surfaces. Not only can it be used as a new strategy for universal high-precision printing and droplet control, but it will also promote the application and development of technologies in numerous fields, such as liquid transport and microfluidics.