Precise Morphological Control of DNA Crystals Through Concentration‐Modulated Microfluidic Droplets

ABSTRACT The lack of control over macroscopic crystal morphology and quantity in traditional DNA crystallization methods has hindered detailed investigation of DNA crystals. Here, we present a novel approach to synthesize high‐quality single crystals with precisely defined morphology using proportional encapsulation within microfluidic double emulsion droplet (DED) microreactors. The concentration of crystallization habit modifier within each microreactor can be precisely tuned by adjusting the flow rates of solutions in two coaxial channels, enabling regulation of the macroscopic crystal morphology. This platform allows for the precise regulation of DNA crystal self‐assembly, supporting both directional macroscopic growth (longitudinal or transverse) and the fabrication of rhombohedral crystals with controllable aspect ratios ranging from 5.94 to 1.10. This novel method for producing high‐quality single DNA crystals significantly expands their applicability in microengineering and enables in‐depth investigations of crystallization kinetics.