Ultrasonic signatures of multiphase architectured media: Application to biomechanics

Assessing the mechanical characteristics of periodic architectured scaffolds employed in bone tissue repair, while preserving their structural integrity, poses a significant challenge from both theoretical and experimental viewpoints. By leveraging concepts arising from the phononic crystals community, here we investigate the reflection and transmission of elastic waves propagating through water-immersed biphasic architectured samples in the MHz regime, which exhibit a periodic organization at a length scale of a few hundred micrometers. Experimental outcomes are systematically compared with modeled predictions, spanning a range of scaffold-like samples engineered to mimic the expected variations that take place in a biological environment. A particular attention is given to critical modeling considerations such as the behavior in reflection, the interaction of Bloch waves with the viscoelastic properties of the constituent phases, as well as the role of modal conversion at the interface between the homogeneous incident medium and the architectured one. Altogether, the reported results suggest that specific ultrasonic signatures associated with elastic wave propagation in periodic media, encompassing phenomena such as bandgaps and dispersion, offer valuable insights towards the nondestructive monitoring of micro-architectured media like scaffolds.