Experimental study of time response of bending deformation of bone cantilevers in an electric field

Abstract

Bone is a complex composite material with hierarchical structures and anisotropic mechanical properties. Bone also processes electromechanical properties, such as piezoelectricity and streaming potentials, which termed as stress generated potentials. Furthermore, the electrostrictive effect and flexoelectric effect can also affect electromechanical properties of the bone. In the present work, time responses of bending deflections of bone cantilever in an external electric field are measured experimentally to investigate bone's electromechanical behavior. It is found that, when subjected to a square waveform electric field, a bone cantilever specimen begins to bend and its deflection increases gradually to a peak value. Then, the deflection begins to decrease gradually during the period of constant voltage. To analyze the reasons of the bending response of bone, additional experiments were performed. Experimental results obtained show the following two features. The first one is that the electric polarization, induced in bone by an electric field, is due to the Maxwell-Wagner polarization mechanism that the polarization rate is relatively slow, which leads to the electric field force acted on a bone specimen increase gradually and then its bending deflections increase gradually. The second one is that the flexoelectric polarization effect that resists the electric force to decrease and then leads to the bending deflection of a bone cantilever decrease gradually. It is concluded that the first aspect refers to the organic collagens decreasing the electric polarization rate of the bone, and the second one to the inorganic component influencing the bone's polarization intensity.

Electrospun Polyvinylidene Fluoride-Based Fibrous Scaffolds with Piezoelectric Characteristics for Bone and Neural Tissue Engineering

“…Human bones have the ability of self-remodeling through an electromechanical mechanism due to the piezoelectric effect [163]. Thus, mechanical stimulation of bones induces their growth and regeneration as a result of the generation of electrical potential [3,23]. The application of electrical stimulation has been found to be effective in enhancing rat bone marrow mesenchymal stem cells (rBMSCs) and rat adipose-derived mesenchymal stem cells (AT-MSCs) migration, proliferation, differentiation, and stimulates high levels of osteogenic expressions.…”

“…The carbonyl oxygen of peptide has a negative charge, while the amide nitrogen with a positive charge, thus establishing a small electric dipole [21]. When collagen is mechanically deformed, electric charges are produced, and the electrical potential generated promotes bone growth and regeneration [22,23,24,25,26].…”

Variation of Streaming Potentials with Time under Steady Fluid Pressure in Bone

“…The multicomponent materials and hierarchical microporous structure of bone may lead to the rate of MWp being much less than those of the general ionic displacement and dipole orientation polarizations. The polarization time of MWp ranges from 10 −1 s to several hours [36,37], while ionic displacement and dipole orientation polarizations last less than milliseconds [38]. The electrical conductivities of bone collagens and hydroxyapatite crystals are in different orders of magnitude [39] and the hierarchical structure of bone are the conditions of MWp [36,37].…”

“…The polarization time of MWp ranges from 10 −1 s to several hours [36,37], while ionic displacement and dipole orientation polarizations last less than milliseconds [38]. The electrical conductivities of bone collagens and hydroxyapatite crystals are in different orders of magnitude [39] and the hierarchical structure of bone are the conditions of MWp [36,37]. On the one hand, the electric charges on the bone solid cause electric double layers in bone microcanals; on the other hand, the charges form nonuniform electric fields inside bone.…”

Flexoelectric materials and their related applications: A focused review

“…Recent studies suggest that many biological materials such as bones, hairs, and bio-membranes have remarkable flexoelectric response [55][56][57][58][59]. The first studies of the flexoelectricity in biological materials could be traced back to 1975 by Williams and Breger [60].…”