Fig. 4: Results of two droplets fusion simulation.

a Simulated two-droplet fusion morphology of cases without a UDF and with the CAH UDF. b Simulated two-droplet fusion morphology of cases with different densities and impact velocities. c Simulated two-droplet fusion morphology of cases with different surface tensions and viscosities. All pictures are top views of simulated two-droplet fusion morphology. a Shows the difference between cases without UDFs and with CAH UDF. b Results reveal that the influence of impact velocity and density mainly worked in the early stage(<0.05 s) and can be ignored in the whole printing process. c Shows that the same value of surface tension/viscosity is the major factor that determines the simulated morphology at different times.