For the first time, it has been demonstrated theoretically that a functionalized CNT embedded in a lipid bilayer can selectively allow cations to move across under the influence of an applied electric field.25 The NT, 0.91 nm in diameter and 3.6 nm in length, is functionalized with hydrogen at the ends and in two thin circular rings near the entrances of the NT, as illustrated in Figure 6. This NT is selectively permeable to monovalent cations, binds divalent cations, and rejects anions. The characteristics of this channel resemble the antibiotic gramicidin A, one of the first antibiotics used clinically, but the potassium current is six times larger. Moreover, Hilder et al68 designed a CNT 1 nm in diameter and 3.6 nm in length that is functionalized with carboxylic acid at the ends. In the presence of an electric field the NT exhibits the ability to selectively conduct cations by an ion chaperoning mechanism, whereby a chloride ion ferries a sodium ion across the channel.