Bio-inspired mini-eggs with pH-responsive membrane for enzyme immobilization

► Capsule membranes are prepared via minifluidics, adsorption and biosilicification. ► Capsule membranes are composed of inner Ca-alginate/protamine and outer silica layers. ► Diffusional permeability across Ca-alginate/protamine membranes is pH-responsive. ► Enzymatic reaction in capsules can be effectively controlled by ambient pH condition. ► The pH-responsive switching of capsule membrane is rapid, reversible and reproducible.