Piezoelectricity in collagen type II fibrils measured by scanning probe microscopy

The converse piezoelectric effect in collagen type II fibrils, the main collagen constituent in cartilage, was investigated using piezoresponse force microscopy. The fibrils exhibited shear piezoelectric behavior similar to that previously reported in collagen type I fibrils and followed the same cantilever-fibril angle dependence present for type I. A uniform polarization directed from the amine to carboxyl termini, as seen for collagen type I, was observed in all type II fibrils studied. The shear piezoelectric coefficient, d₁₅, however, for type II was roughly 28-32% of the value measured for type I fibrils. Possible explanations for the reduced piezoelectric coefficient of type II collagen are provided.