Binder droplet impact mechanism on a hydroxyapatite microsphere surface in 3D printing of bone scaffolds

The combination of hydroxyapatite composite powder and three-dimensional (3D) printing rapid prototyping techniques has markedly improved skeletal interactions in orthopedic surgery applications. 3D printing methodology ensures effective bionic microstructure and shape interactions between an implant and the surrounding normal tissue. In effort to enhance the quality, precision, and mechanical properties of printed bone scaffolds, this study examines binder droplet spreading performance on the surface of hydroxyapatite (HA) microspheres. The piezoelectric nozzle diameter is about 10 μm, which sprays droplets 20 μm in diameter. The average size of HA powder particles is about 60 μm in diameter. Most laboratories, however, are limited to observation of a single droplet 20 μm or smaller in diameter impacting a spherical surface 60 μm in diameter. Based on non-dimensional scale similarity theory in axisymmetric Stokes flow dynamics, this study conducted experiments and simulation on the same collision conditions (droplet 200 μm in diameter, spherical surface 600 μm in diameter). Simulation results were consistent with experiment data, and form a basis for future research on modeling droplet impact on spherical surfaces.