Interfacial Chirality Transfer Induced by Vortices inside Microdroplets

Chiral materials have broad applications in optics. Precise regulation of the chiral signal, however, remains highly challenging. Herein, a microfluidic strategy is proposed in which the cooperative action of dual driving forces regulates vortical flow inside droplets. The flow rate and interfacial tension are adjusted to induce ordered Marangoni convection and shear flow within microdroplets. Under these conditions, chiral signals are transmitted both within droplets and across the liquid-liquid interface. Tetrakis(4-sulfonatophenyl)porphyrin and phenethylamine are employed as a supramolecular co-assembly pair to probe the relation between vortex strength/distribution and chiral-signal transfer. Assemblies obtained under microdroplet vortex fields exhibit markedly enhanced and nearly mirror-image circular dichroism (CD) responses in comparison with those prepared under conventional magnetic stirring. These observations confirm that vortical flow efficiently promotes chiral amplification and enantioselective supramolecular assembly. Flow-field visualization by micro-particle image velocimetry (μ-PIV), combined with hydrodynamic analysis, reveals the formation mechanism and evolution of microvortices under the dual driving forces. Overall, this study demonstrates a practical approach to modulating supramolecular chiroptical signals via vortexes in confined environments.