Nanoindentation-based mechanical characterization of Poly(vinyl alcohol) for biological phantom realization

Intramedullary spinal cord surgery requires surgical instruments capable of operating within highly delicate neural tissue, where localized mechanical and thermal effects may critically influence procedural safety. Ultrasonic Surgical Aspirator, such as the Cavitron Ultrasonic Surgical Aspirator (CUSA), represents a promising tool for controlled soft-tissue resection; however, its interaction with spinal cord tissue remains insufficiently characterized. The use of tissue-mimicking phantoms may therefore provide a controlled and reproducible platform to investigate such interactions. Poly(vinyl alcohol) (PVA) hydrogels are widely used as tissue-mimicking materials due to their stability, biocompatibility, and tunable physical properties. In this study, PVA was selected as a candidate material for spinal cord phantoms since specific formulations have been shown to exhibit thermal properties comparable to those of native neural and tumoral tissues. Since ultrasonic aspiration inherently involves mechanical vibration, accurate mechanical characterization is essential. Accordingly, PVA hydrogels fabricated at three polymer concentrations (10 %, 15 %, and 20 % w / w) were mechanically characterized using a nanoindentation-based approach. Depth-resolved nanoindentation analyses showed that increasing the polymer concentration leads to higher effective elastic modulus and lower viscoelastic dissipation in PVA hydrogels. The measured effective modulus values are slightly higher than those reported for native spinal cord tissue (on the order of tens of kPa) and intramedullary tumors (on the order of a few kPa), but they remain within the regime of soft hydrated materials and enable systematic modulation of mechanical properties across formulations.