TERAHERTZ PROBING AS AN INDICATOR FOR DETECTING THE ONSET OF BIORESORPTION OF GYROID POLYACTIDE TPMS SCAFFOLDS

Triply periodic minimal surfaces (TPMSs) made of biodegradable polylactide (PLA) are promis-ing metamaterial scaffolds for tissue engineering. However, non-invasive in situ monitoring of resorption of such scaffolds remains a significant challenge. Using the finite-difference frequency-domain (FDFD) method, we simulate the propagation of terahertz radiation in the frequency range 0.65–3.00 THz, taking into account the dielectric properties of PLA (real part of the permittivity ε′ = 2.7) and soft tissues (ε′ = 40, loss cone tangent tan δ ≈ 0.6). It is shown that for the porosity φ = 0.44, the structure is completely opaque to terahertz radiation, whereas for φ = 0.52, a sharp percolation jump is observed in the field amplitude, transmission, and reflection coefficient. At a frequency of 3 THz, the reflection coefficient reaches 0.66, indicating strong frequency selectivity of the response. The phase map and shadow mask confirm the topological sensitivity of the field and serve as additional diagnostic signs of degradation. The obtained results substantiate the applicability of terahertz probing as a sensitive indicator for detecting the very onset of bioresorption in minimally invasive, near-surface diagnostics of, for example, subcutaneous or epidermal implantations.