Electromechanical Transduction with Charged Polyelectrolyte Membranes

Collagen and other polyelectrolyte materials in a homogeneous, aqueous electrolyte are studied and modeled as a seat of electromechanical transduction. The frequency response of collagen membranes in a range of chemical environments shows how transduction with a deformable membrane coupled hydrodynamically to an external mechanical system can lead to a mechanical response resulting from an electrical stimulus and an electrical response to a mechanical excitation. Dynamic measurements, which can more easily distinguish between membrane and electrode phenomena, result in electromechanical coupling coefficients that show reciprocity and agree with values determined by stationary techniques. A model representing the membrane at the interfibrillar level by a system of cylindrical pores is developed relating externally measured potentials, membrane deformations, currents, and mass fluxes to equivalent pore radius, fibril diameter, and polyelectrolyte charge. Measured values of the membrane coupling coefficients are then used to infer average microstructural parameters of the membrane that compare favorably to available data based on electron microscopy.