In this paper we report about combining inkjet printing technology and self-assembly as a scalable manufacturing tool for spherical, well-ordered aggregates. The aggregates consist of a high number of ordered colloidal nanospheres arranged as ball-shaped structures. Applying inkjet printing based on the principle of droplet ejection the spherical aggregates can be deposited on various surfaces in dry environment and under ambient conditions. The aggregation of the nanospheres is independent of the surface energy of the substrate leading to the assumption that the main part of the assembly and aggregation process takes place in-flight .
By applying inkjet printing with an adapted control signal, small droplets of a water-based ink formulation containing monodisperse polystyrene nanoparticles are ejected out of the inkjet nozzles. The ejected droplets serve as a confined geometry for the nanospheres in the carrier liquid during evaporation. As a result, the particles form stable ball-shaped aggregates with hexagonal order. Due to the in-flight self-assembly of the nanospheres, our approach is suitable for any solid surface in dry environment and allows the deposition of the ball-shaped aggregates in appropriate patterns.