Dielectrophoresis
In dielectrophoresis , an inhomogeneous electric field - consisting of direct current (DC) and alternating current (AC) - is used to manipulate particles. The inhomogeneous field induces a dipole moment in the particles , which then interacts with the applied field: the particles experience a force and - depending on the field and dipole moment - move in areas of higher (positive DEP) or lower (negative DEP) Field strength . The force effect is proportional to the volume of the particles. In this way, particles can also be captured in a "field cage" depending on their size. Dielectrophoresis is used for sorting and detecting nanoparticles , viruses, etc.
For a cylinder that is parallel to the field with a radius and half the length with a dielectric constant in a medium with a constant , the dielectrophoretic force is given by:
One application in biology is e.g. B. to move a cell in an inhomogeneous alternating electric field regardless of its surface charge. For a polarizable sphere (e.g. a spherical cell) the following equation applies as a good approximation:
- : Nabla - Operator (field inhomogeneity between two points)
- : absolute dielectric constant (8.85 10 −12 F m −1 )
- : relative dielectric constant of the medium
- : relative dielectric constant of the cell
- E : electric field strength
literature
- Frieder Ostermaier: Curvature-sensitive biomembrane sensors: A structure with carbon nanotubes . Ed .: Frank OR Fischer. Springer-Verlag, Wiesbaden 2016, ISBN 978-3-658-11926-3 , p. 50–53 ( limited preview in Google Book Search).