Research on Squeezing Film Formation of High-Viscosity Multidroplets with a Macro Model

The morphology distribution of high-viscosity film in a micron gap is crucial for microassembly engineering. This paper presents a simplified macro model for predicting the squeezing film formation of multidroplets. The film-formation processes and mechanical properties are investigated in detail. The simulation results of the macro model for film shape and squeezing force are consistent with the experiment, which indicates that the final film shape is determined by the initial distribution of multidroplets, and the squeezing force increases exponentially as the gap height decreases. The squeezing force of multidroplets can be divided into two stages. The first stage is independent spreading, in which the squeezing force decreases as the number of dispersed droplets N, and approximately follows a relationship of 1/N. In contrast, the second stage is coalescing-spreading, in which the squeezing force is related to the initial distribution of droplets. Nevertheless, the droplet dispersion can effectively alleviate the squeezing force induced by a single droplet in both stages. In addition, the non-Newtonian properties significantly influence the squeezing force but have no obvious effect on the film shape. This paper contributes to the prediction and optimization of squeezing film formation.