Electron lenses may operate electrostatically or magnetically. Such polypeptide ligands are often positively charged and interact electrostatically with anionic membranes. Sodium sulfate is a typical electrostatically bonded ionic sulfate. Ligands may interact with DNA by covalently binding, electrostatically binding, or intercalating. Ions are electrostatically trapped in an orbit around a central, spindle shaped electrode. The ions bond electrostatically with negative sites on bacterial cell walls and denature proteins. This suggests that the ball occludes the channel by binding electrostatically rather than covalently. Ohmic switches are controlled by electrostatically controlled cantilevers. The artificial and structureless background charge interacts electrostatically with itself and the electrons. This process puts a coating on an item electrostatically, which is then cured by heat. The dye interacts electrostatically but noncovalently with the amino and carboxyl groups of proteins. Microfiber can be electrostatically charged for special purposes like filtration. Some regard the helix macrodipole as interacting electrostatically with such groups. Newer developments also enabled electrostatically activated bimorphs for the use in microelectromechanical systems. The ball domain is electrostatically attracted to the inner channel domain.