Hollow fiber membrane governed microjet flow regime for confined crystallization of large-sized crystal aggregates

Confined crystallization can realize controllable nucleation and growth of crystals with targeted morphologies in a restricted region. Here, we achieved confined reactive crystallization within a novel micro columnar jet flow regime constructed by the hollow fiber membrane. The interface of the jet flow corresponds as the restricted region for reactive crystallization, and the large-sized calcium carbonate (CaCO 3 ) crystals aggregates with millimeter length can ordered and self-assembly grow along the boundary of this region. Formation mechanism of the jet flow was systematically investigated by real-time observation and force analysis. The detected detachment-regrowth cycle during the experiments furtherly uncovered the potential for continuous operation. Linear (diameter: 0.12–0.3 mm; length: 1.5–3.1 mm) and lamellar crystals (thickness of 200–300 nm and average area of 0.21 mm 2 ) were obtained by effectively manipulating the diameter and effective length of jet flow.