Figure 2. Outer hair cell's active force measurement in the microchamber experiment.

The cell is partially inserted into a large pipette (microchamber), and voltage V_app is applied to the chamber environment. The voltage in the microchamber results in the membrane potentials, V_in, and V_ex, of the included and excluded parts of the cell. These potentials have opposite signs, and the two (included and excluded) parts of the electromotile cell become, respectively, shorter and thicker and longer and thinner. The excluded part pushes the AFM cantilever of a prescribed stiffness, and the generated active force, F, can be estimated based on the displacement of the cantilever.