18-Crown-6-ether (18C6; 1,4,7,10,13,16-Hexaoxacyclooctadecane) is an organic compound that can be used to prepare stable microcapsule responsive layers for further assembly into bilayer microcapsules. For example, 18-Crown-6-ether is used to prepare the response layer and is coated with a G-quadruplex cross-linked hydrogel layer stabilized by K⁺; when Mg²⁺ ions are present, 18-Crown-6-ether and K⁺ ions can respectively Dissociates and locks with the G-quadruplex cross-linked layer, thereby achieving switchable controlled release of the load^[1].