title: In situ Materials Characterization using the Tissue Diagnostic Instrument.
abstract: An understanding of the mechanical behavior of polymers is critical towards the design, implementation, and quality control of such materials. Yet experiments and method for the characterization of material properties of polymers remain challenging due the need to reconcile constitutive assumptions with experimental conditions. Well-established modes of mechanical testing, such as unconfined compression or uniaxial tension, require samples with specific geometries and carefully controlled orientations. Moreover, producing specimens that conform to such specifications often requires a considerable amount of sample material. In this study we validate a micromechanical indentation device, the Tissue Diagnostic Instrument (TDI), which implements a cyclic indentation method to determine the material properties of polymers and elastomeric materials. Measurements using the TDI require little or no sample preparation, and they allow the testing of sample materials in situ. In order to validate the use of the TDI, we compared measurements of modulus determined by the TDI to those obtained by unconfined compression tests and by uniaxial tension tests within the limit of small stresses and strains. The results show that the TDI measurements were significantly correlated with both unconfined compression (p<0.001; r(2) = 0.92) and uniaxial tension tests (p<0.001; r(2)=0.87). Moreover, the measurements across all three modes of testing were statistically indistinguishable from each other (p=0.92; ANOVA) and demonstrate that TDI measurements can provide a surrogate for the conventional methods of mechanical characterization.
authors.affiliation: Department of Orthopedic Surgery, University of California, San Francisco, CA, 94143.
authors.forename: Simon Y
authors.initials: SY
authors.lastname: Tang
authors.forename: Phillip
authors.initials: P
authors.lastname: Mathews
authors.forename: Connor
authors.initials: C
authors.lastname: Randall
authors.forename: Eugene
authors.initials: E
authors.lastname: Yurtsev
authors.forename: Kirk
authors.initials: K
authors.lastname: Fields
authors.forename: Andrew
authors.initials: A
authors.lastname: Wong
authors.forename: Alfred
authors.initials: A
authors.lastname: Kuo
authors.forename: Tamara
authors.initials: T
authors.lastname: Alliston
authors.forename: Paul
authors.initials: P
authors.lastname: Hansma