All-electrical indentation shear modulus and elastic modulus measurement using a piezoelectric cantilever with a tip

Abstract

We have investigated an all-electrical indentation shear modulus and elastic modulus measurement technique using piezoelectric cantilever sensors with a tip for potential in vivo applications. A piezoelectric cantilever with a tip was capable of carrying out compression, shear, indentation, and indentation shear tests, where compression and shear tests refer to those where the sample is not confined by a container and the contact area of the cantilever is the same as or larger than the sample surface area and the indentation and indentation shear tests are those where the contact area of the cantilever is smaller than the sample surface area. Because the cantilever could measure both the elastic modulus and the shear modulus, Poisson’s ratio of a sample could be determined from the ratio of the shear modulus to the elastic modulus with no presumption. We showed that the experimental elastic moduli and shear moduli obtained from the indentation and indentation shear tests agree with those obtained from the compression and shear tests. Furthermore, we showed that the same elastic moduli and the same shear moduli could be obtained either by using the displacement measurements or by the induced voltage measurements across the sensing piezoelectric layer. With a model tissue consisting of modeling clay embedded in gelatin, we demonstrated that the indentation compression and indentation shear tests could produce two-dimensional elastic and shear moduli maps or images that accurately showed the size and location of the modeling clay inclusion.