FIGURE 1.

Schematic cross section of cell on silicon chip. The chip is insulated by silicon dioxide that is coated with extracellular matrix protein. There is a cleft of thickness between the oxide (area-specific capacitance ) and the lipid bilayer of the cell membrane (area-specific capacitance ). The diameter of the cell-chip contact is ∼20 μm, the thickness of membrane and oxide are ∼5 nm and ∼15 nm, respectively, and the distance of cell and chip is ∼75 nm. The cleft is filled with an electrolyte of resistivity . Its sheet resistance is . When the electrical voltage between substrate and bulk electrolyte is changed, the voltages and across the attached and free membrane change as probed with a voltage-sensitive dye.