Nanoscale characterization of isolated individual type I collagen fibrils: polarization andpiezoelectricity

Abstract

Piezoresponse force microscopy was applied to directly study individual type I collagen fibrils with diametersof ∼100 nm isolated from bovine Achilles tendon. It was revealed that single collagen fibrils behavepredominantly as shear piezoelectric materials with a piezoelectric coefficient on the order of1 pm V−1, and have unipolar axial polarization throughout their entire length. It was estimated that,under reasonable shear load conditions, the fibrils were capable of generating an electricpotential up to tens of millivolts. The result substantiates the nanoscale origin ofpiezoelectricity in bone and tendons, and implies also the potential importance of the shearload-transfer mechanism, which has been the principle basis of the nanoscale mechanicsmodel of collagen, in mechanoelectric transduction in bone.