18-Crown-6-ether (18C6; 1,4,7,10,13,16-Hexaoxacyclooctadecane) is an organic compound utilized in forming stable microcapsule responsive layers, which can be further assembled into bilayer microcapsules. For instance, a responsive layer can be prepared using 18-Crown-6-ether and coated with a K+ stabilized G-quadruplex crosslinked hydrogel layer. In the presence of Mg2+ ions, 18-Crown-6-ether and K+ ions can respectively dissociate and lock with the G-quadruplex crosslinked layer, achieving switchable controlled release of the payload.