Fig. 1.
The DAIMM method: (A) The measurement setup, the theoretical electric field lines, and the electronic circuit of the DAIMM method. Note that an important prerequisite is an asymmetric electrode configuration to establish inhomogeneous electric field conditions in the reaction compartment of the perfusion chamber. (B) The spatial gradient of dielectrophoretic forces on a manipulated single cell. These forces result in a movement of the manipulated cell toward the area of highest field (positive dielectrophoresis), that is, toward the tip of the smaller electrode of the asymmetric electrode configuration (single-spike electrode). Critical for establishing a cell configuration as shown in (A) is that the field parameters are selected in a way assuring that the single-spike electrode will penetrate the cell membrane without disruption of the cell. (C) Establishment of the system configuration depicted in (A) by using a HEK293 cell in a low-conductive medium (2 MHz, 30 Vpp alternating field, pulses of 300-ms duration). White scale bar=10 μm. DAIMM, dielectrophoretically-accessed intracellular membrane-potential measurement.