dielektrophoresis

Dielectrophoresis (DEP) is a phenomenon where a non-uniform electric field induces a force on a dielectric<bos> material, causing it to move. This force arises from the polarization of the dielectric material in response to the electric field. When a dielectric particle is placed in a non-uniform electric field, the induced dipole moment within the particle interacts with the field gradient, resulting in a net force. The direction of this force depends on the polarizability of the particle relative to the surrounding medium and the frequency of the applied electric field.

If the particle is more polarizable than the medium, it will be attracted towards regions of higher electric field strength, a phenomenon known as positive dielectrophoresis (pDEP). Conversely, if the particle is less polarizable than the medium, it will be repelled from regions of high electric field strength and move towards regions of lower field strength, exhibiting negative dielectrophoresis (nDEP). The crossover frequency, at which the polarization of the particle equals that of the medium, determines the transition between pDEP and nDEP.

Dielectrophoresis has found numerous applications in science and technology. It is widely used in manipulating and separating biological cells, such as bacteria, viruses, and blood cells, based on their electrical properties. In microfluidic devices, DEP is employed for cell sorting, focusing, and trapping, enabling various diagnostic and analytical procedures. Furthermore, DEP can be utilized for the manipulation of particles in non-biological systems, including the assembly of micro- and nano-scale structures and the sensing of chemical species. The ability to control particle movement without physical contact makes DEP a valuable tool in fields like biotechnology, chemical engineering, and materials science.