A method is provided, including identifying that a subject is at risk of suffering from atrial fibrillation. A left-handed material includes a substrate, a plurality of deformed split ring resonators, and a plurality of metallic bars, wherein the DSRR and the metallic bars are disposed on the substrate with each DSRR and metal bar alternately arranged. Preferred eukaryotic cells for use in the present invention are plant cells and mammalian cells.