3D Controllable Crystallization by Programmable Seeding

Crystallization is a fundamental phenomenon in nature with significant implications across science and industry, including pharmaceuticals, semiconductors and metallurgicals. However, research on 3D controllable crystallization remains unexplored. In this work, we develop a novel strategy for controlling the crystallization of supersaturated sodium acetate trihydrate through programmable seeding, to investigate the crystallization principle from confined channels to unconfined flat plane and 3D space. In confined channels, geometric constraints drive crystals to align along the channel direction, except in right-angle channels. In unconfined conditions, various programmable seeding templates (e.g., point, lines, planes, and 3D structures) are used to initiate nucleation and control growth of crystal. Crystallization follows a universal principle, where crystals grow perpendicularly to seeding templates, attributable to constraints from their needle-like habit and surface energy minimization. Specifically, points seeding induces radial crystal alignment, while linear and planar seeding lead to perpendicular crystal growth. Furthermore, overall crystal patterns generated from multiple seeding templates are successfully analyzed and predicted using Voronoi diagrams, a spatial discretization model. Controllable crystallization enables barrier-guided path planning and the fabrication of 3D bionic tree structures with capillary-active channels. Understanding 3D crystallization principles opens new avenues for novel manufacturing techniques, advanced crystallization processes and high-performance functional materials.