Keywords

alginate hydrogel; radiologically equivalent phantom; computational fluid dynamics; bubble dispersion; Hounsfield Unit; radiological property

Abstract

The foaming of hydrogels presents a promising strategy for tailoring mechanical and radiological properties to replicate biological soft tissues for biomedical phantoms. Achieving uniform and predictable void fraction distributions in alginate hydrogel foams remains a challenge due to the complex interplay between bubble dynamics, matrix rheology, and interfacial forces during the pre-gelation aeration stage. This thesis develops a Computational Fluid Dynamics framework using the transient Eulerian two-fluid approach to predict void fraction distribution in alginate hydrogel precursor solutions aerated by air injection through a bottom nozzle. The objective is to use the framework for design of the foaming system to match desired gas-fraction distribution and radiological property. The framework is first validated against three independent air-water experimental benchmarks. Seven parametric cases are then investigated, comprising variation of the  inlet air velocity, alginate concentration, and surface tension. The predicted results show that higher inlet velocities promote stronger jet penetration and larger gas accumulation, while increasing alginate concentration confines the bubble plume, with quasi-steady gas fractions displaying a non-monotonic trend with concentration. Elevated surface tension yields broader plume coverage and improved uniformity at the expense of peak void fraction. The predicted quasi-steady void fractions map to radiological property (Hounsfield Unit) values of -34 to -103, spanning the adipose and fatty breast tissue range (-50 to -150 HU). At 5.0 wt% alginate, the peak gas fraction yields -307 HU, approaching published experimental CT measurements for the same formulation (-460 to -233 HU). The computational framework is further extended to three-dimensional lung mold phantom geometries with and without mechanical agitation, establishing a computational-to-fabrication pathway for production of radiologically equivalent biomedical phantoms.

Completion Date

2026

Semester

Spring

Committee Chair

Olusegun Ilegbusi

Degree

Master of Science in Mechanical Engineering (M.S.M.E.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Document Type

Dissertation/Thesis

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