Soft Elastomeric Capacitor for Strain and Stress Monitoring on Sutured Skin Tissues

Sutures are ubiquitous medical devices for wound closures in human and veterinary medicine, and suture techniques are frequently evaluated by comparing tensile strengths in ex vivo studies. Direct and nondestructive measurement of tensile force present in sutured biological skin tissue is a key challenge in biomechanical fields because of the unique and complex properties of each sutured skin specimen and the lack of compliant sensors capable of monitoring large levels of strain. The authors have recently proposed a soft elastomeric capacitor (SEC) sensor that consists of a highly compliant and scalable strain gauge capable of transducing geometric variations into a measurable change in capacitance. In this study, corrugated SECs are used to experimentally characterize the inherent biomechanical properties of canine skin specimens. In particular, an SEC corrugated with a re-entrant hexagonal honeycomb pattern is studied to monitor strain and stresses for three specific suture patterns: simple interrupted, cruciate, and intradermal patterns. Stress is estimated using constitutive models based on the Fractional Zener and the Kelvin-Voigt models, parametrized using a particle swarm algorithm from experimental data and results from a validated finite element model. Results are benchmarked against findings from the literature and show that SECs are valuable for clinical evaluation of tensile force in biological skins. It was found that both the ranking of suture pattern performance and the sutured skin's Young's modulus using the proposed approach agreed with data reported in the literature and that the estimated stress at the suture level closely matched that of an approximate finite element model.