Using tendon inherent electric properties to consistently track induced mechanical strain

The present work explores the possibility that the inherent electrical properties of a tendon might allow it to act as its own strain gauge. Tendon has been shown to exhibit piezoelectric effects as well as streaming potentials when subjected to a mechanical stress. To assess the feasibility of using these properties to repeatably measure in situ strain,bovine Achilles tendon test specimens were connected in series with a control resistor in a direct current circuit. Longitudinal(along the collagen fiber direction) and transverse test specimens were subjected to sinusoidal tension while electrical resistance data for the specimens was collected. Change in resistance per unit strain and gauge factors (GFs) revealed a repeatable and significantly different correlation between resistance and strain for the longitudinal and transverse specimens (p<0.001). Change in resistance per unit strain values for longitudinal and transverse specimens were 0.85 and 1.76 MX/e, respectively while corresponding GFs were 0.52 and 0.74, respectively. Others have reported piezoelectric mechanisms and streaming potential mechanisms in hydrated collagen, however the present work is unique in presenting an accurate and repeatable model of anisotropic tendon behavior that could be used to develop an in situ strain sensor.