Experimental characterization of biphasic materials using rate-controlled Hertzian indentation

• Describes a new method to characterize biphasic material properties.
• Method uses standard indentation techniques with a Hertzian contact.
• Paper directly validates the method against the gold standard.

This paper describes a new method, based on Hertzian biphasic theory (HBT), to characterize properties of biphasic materials with reduced time demands, increased surface sensitivity, and reduced computational demands compared to the current gold standards. Indentation experiments were conducted at a single location on a representative osteochondral plug to demonstrate and validate the HBT method against two gold standards, linear biphasic theory (LBT) and tension–compression nonlinear biphasic theory (TCN). The (1) aggregate moduli, (2) permeability and (3) tensile moduli from HBT, LBT, and TCN were (1) HA=0.47, 0.47, and 0.40 MPa, (2) k=0.0026, 0.0014 and 0.0016 mm4/Ns, and (3) Et=8.7, 0.46, and 10.3 MPa, respectively. The results support the HBT method and encourage its use, especially in light of its practical advantages.