Trapping proteins on nanopores by dielectrophoresis

Interest in the phenomenon of dielectrophoresis has gained significant attention in recent years due to its potential for sorting, manipulation, and trapping of solutes, such as proteins, in aqueous solutions. For many decades, protein dielectrophoresis was considered impossible, as the predicted magnitude of the force arising from experimentally accessible field strengths could not out-compete thermal energy. This conclusion was drawn from the mainstay Clausius-Mossotti (CM) susceptibility applied to the dielectrophoretic force. However, dielectric interfacial polarization leading to the CM result does not account for a large protein dipole moment that is responsible for the dipolar mechanism of dielectrophoresis outcompeting the CM induction mechanism by three to four orders of magnitude in the case of proteins. Here, we propose an explicit geometry within which the dipolar susceptibility may be put to the test. The electric field and dielectrophoretic force are explicitly calculated, and the dependence of the trapping distance on the strength of the applied field is explored. A number of observable distinctions between the dipolar and induction mechanisms are identified.