Towards a novel tensile elastometer for soft tissue

A device designed to determine the tensile properties of soft tissue is proposed for use within the surgical environment. Two pins indent the surface of a bulk of soft tissue and are separated laterally. Using an approximation, the measured load and displacement are mapped to the uniaxial stress and strain of a central volume of material. A correction factor is introduced that depends on geometric factors only for Mooney–Rivlin materials subject to strains of up to 15%, if edge effects are not significant. It is the intention of this study and subsequent studies to design the instrument such that edge effects are minimised. Numerical analysis is employed to test the limits of both the device and the model for Mooney–Rivlin materials. Further analysis is required to determine viability for soft tissue that can display significant anisotropy, material non-homogeneities and highly nonlinear elastic responses. Some initial results towards this end are presented. The method is demonstrated with the use of a prototype device, employing common elastomers to model the soft tissue. An assessment of the accuracy of the prototype and limitations on the use of the device are inferred from the experimental and numerical studies. The modulus of the test materials was subsequently measured to an accuracy of 4% with a spread of 6.5% (using a 95% confidence interval).