Chemical-diffusion Metamaterials with “Plug and Switch” Modules for Ion Cloaking, Concentrating and Selection: Design and Experiments

Abstract The outstanding abilities of metamaterials to manipulate physical fields have been extensively studied in wave-based fields. Recently, this research has been extended to diffusion fields. Chemical diffusion behavior is crucial in a wide range of fields including the transportation of various matters, and metamaterials with the ability to manipulate diffusion with practical applications associated with chemical and biochemical engineering have not yet been proposed. In this work, we propose the idea of a “plug and switch” metamaterial to achieve the switchable functions of ion cloaking, concentrating and selection in liquid solvents by plugging modularized functional units into a functional motherboard. The respective modules are theoretically designed based on scattering cancellation, and the properties are verified by both simulations and experiments. Plugging in any module barely affects the environmental diffusion field, but the module choice impacts different diffusion behaviors in the central region. Cloaking strictly hinds ion diffusion, and concentrating promotes a large diffusion flux, while cytomembrane-like ion selection permits the entrance of some ions but blocks others. In addition to property characterization, these functions are demonstrated in special applications. The concentrating function is experimentally verified by catalytic enhancement, and the ion selection function is verified by protein protection. This work not only demonstrates the effective manipulation of metamaterials in terms of chemical diffusion behavior but also shows that the "plug and switch" design is extensible and multifunctional, and facilitates novel applications including sustained drug release, catalytic enhancement, bioinspired cytomembranes, etc.