Impedance spectroscopy represents a non-invasive means of characterizing the physicochemical properties of many assemblies, including biological systems. IS entails the small-signal measurement of the linear electrical response of the material of interest and the subsequent analysis of the response, yielding useful information about the system. We are currently developing a multifunctional microfluidic pipette with an integrated impedance spectroscopy setup. This device will allow simultaneous single cell superfusion and impedance measurement, to stimulate and analyze, for example, changes within the cell life cycle, or changes in ion channel state within the cell plasma membrane (Fig. 1). These determinations are of specific interest in drug discovery and pharmacology. Microfluidic pipettes are fabricated out of a photosensitive epoxy SU-8 (Fig. 2) and integration of electrodes takes place through a complex step-by-step microfabrication process due to the device structure and fluidic/electrical interfaces both to the cell at the tip and to the fluidic control unit and impedance analyzer.
Figure 1 Schematic illustration of the concept.
Figure 2 Microfluidic pipettes fabricated in SU-8, the image to the right illustrates a possible interface setup.