In this video Ron describes how cells can be selectively manipulated and sorted according to their intrinsic electrical properties, using gentle forces generated by applying radio frequency signals to microelectrode arrays.
 
Background:

The forces acting on the cells shown in these two video clips are known as dielectrophoretic forces, and require the use of microelectrodes whose geometries have been designed to generate high electric field gradients. Using microelectrodes is important because they can generate the required field gradients using small applied voltages that do not harm the cells or cause electrolysis. Dielectrophoresis is therefore a non-destructive way to characterise or manipulate cells. Also, because the dielectrophoretic forces that act on a cell depend on its unique dielectric properties, the cells can be selectively manipulated or sorted without tagging or labelling them with magnetic beads or fluorescent labels, for example. Dielectrophoresis can also be used to isolate or manipulate other biological particles, such as bacteria, viruses, proteins, DNA and RNA.

In the first video, an example is given of how pancreatic cells can be formed into an artificial cell structure for diabetes research. The second video shows breast cancer cells separating from each other according to stages of their cell division. To achieve such cell sorting using current biological techniques would require fluorescent labelling of the nuclear DNA, in order to distinguish those cells at the early stage of their life cycle from those about to divide to form two cells. At the electronic frequencies used in the examples shown in the two videos, the dielectrophoretic force is sensitive to changes in the capacitance and electrical conductance of the cell membrane. This is being used to selectively isolate and characterise stem cells according to their stages of differentiation. To be of clinical use, stem cells should not be labelled.

Our current efforts are also directed towards extending the electronic signals from radio frequencies up to VHF frequencies, where the dielectrophoretic response of a cell depends on its internal properties such as the conductivity of the cytoplasm and the relative size of the nucleus to the cytoplasm volume. The hope is that increased cell sorting efficiency can be achieved by combining the radio frequency selectivity based on cell membrane properties with that achieved at VHF based on the cell’s internal properties.