Ethan Evans

Date of Award

2025

Document Type

Thesis

Publisher

Santa Clara : Santa Clara University, 2025

Degree Name

Master of Science (MS)

Department

Bioengineering

First Advisor

Maryam Mobed-Miremadi

Abstract

This thesis presents a mechanical and microstructural characterization of agarose-based hydrogels as synthetic thrombus analogs for balloon catheter testing. Agarose gels ranging from 0.25% to 1.0% (w/v) were fabricated and analyzed using dynamic shear rheometry, capillary flow porometry, and gas pycnometry. Rheological data showed a nonlinear increase in storage modulus (G′), from 110 ± 66 Pa at 0.25% agarose to 4,900 ± 1,600 Pa at 1.0%, effectively mimicking the viscoelastic spectrum of acute to chronic thrombi. Gas pycnometry measurements indicated that true density (Ptrue) increased modestly from 1.03 g/mL to 1.13 g/mL over the same concentration range. This disproportionate relationship, where a ~10% increase in Ptrue corresponds to over a 40-fold increase in G′, suggests that minor changes in material density, likely due to matrix densification, lead to major alterations in mechanical stiffness. Drying methods significantly influenced mass and volume retention: freeze-dried samples lost up to 0.79 g/cm³ in apparent density, while vacuum-dried gels experienced volume shrinkage of up to 0.67 cm³. Porometry failed to resolve consistent through-pore networks post-lyophilization, underscoring the fragility and collapse-prone nature of low-density gels. Together, these results demonstrate that true density serves as a sensitive indicator of microstructural changes that dramatically affect the mechanical properties of thrombus analogs, and they validate agarose hydrogels as cost-effective, tunable test beds for thrombectomy device development.

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