Tailored 3D printed micro-crystallization chip for versatile and high-efficiency droplet evaporative crystallization

Abstract

Droplet evaporative crystallization on a micro-structured platform with limited interfacial area has potential applications in crystallization theory, bioengineering, and particle drug preparation. Here, an efficient and versatile approach is discussed for multiple drop-evaporative crystallization processes on a micro-crystallization chip fabricated via three-dimensional printing. A chip with limited interfacial area could be fabricated on a highly controlled crystallizer interface. During liquid injection, various drop locations and evaporative conditions can be used, which enables flexible and distinct crystallization processes. This reveals controlling mechanisms and identifies nucleation locations and growth paths. Various classic crystallization systems were introduced to evaluate the chip performance. Controlled nucleation and growth mechanisms at stable evaporative rates were revealed. From the final crystal morphologies, particle locations, and distributions, the effects of the initial concentration and droplet contact conditions at the triple-phase interface could be investigated with high adjustability. Moreover, the results can provide insights into the ‘coffee ring’ formation during evaporative crystallization, dendritic crystal growth, and hydrate crystallization mechanisms. In the limited microstructure, the capillary flow of a liquid drop can spontaneously drive the crystal distribution and morphology. Finally, incorrect liquid drop locations that led to unpredictable crystal formation and distributions were discussed to improve repeatability and efficiency. Applications include the manufacture of particle drugs and flow chemistry.