Nondestructive Characterization of Magnetic Polymeric Scaffolds Using Terahertz Time-of-Flight Imaging

Magnetic scaffolds (MagS) are 3-D composite materials, in which magnetic nanoparticles (MNPs) are used to load a polymeric matrix. Due to their wide use in several medical applications, there is an increasing demand of advanced techniques for nondestructive quality assessment procedures aimed at verifying the absence of defects and, more generally, dedicated to the characterization of MagS. In this framework, the use of terahertz (THz) waves for nondestructive characterization of multifunctional scaffolds represents an open challenge for the scientific community. This article deals with an approach for the characterization of MagS by means of a THz time-domain system used in reflection mode. THz analyzes are performed on poly-caprolactone (PCL) scaffolds magnetized with iron oxide (Fe
$_{3}$
O
$_{4}$
) MNPs through a drop-casting deposition and tuned to obtain different distributions of MNP in the biomaterial. The proposed data processing approach allows a quantitative characterization of the MagS, in terms of their (estimated) thickness and refractive index. Moreover, the proposed procedure allows us to identify the areas of the scaffold wherein MNP are mainly concentrated, and thus, it gives us information about MNP spatial distribution.