College of Graduate Studies: Theses & Dissertations

Term of Award

Spring 2026

Degree Name

Master of Science, Mechanical Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Mechanical Engineering

Committee Chair

Sevki Cesmeci

Committee Member 1

Priya Goeser

Committee Member 2

Prakashbhai Bhoi

Abstract

Magnetorheological elastomers (MREs) offer a promising pathway for soft, magnetically actuated drug‑delivery systems, yet material‑selection guidelines remain unclear due to limited comparative data across particle chemistries, size scales, and concentrations. This study systematically evaluates how magnetic filler type (carbonyl iron and magnetite) and particle size (micro vs. nano), at two weight percentages – 40 wt% and 50 wt% – in Sylgard 184 PDMS influence the viscoelastic behavior of MREs intended for compliant biomedical actuation. Eight particle formulations were prepared through sieving, controlled mixing, vacuum degassing, and isotropic curing, producing nineteen total specimens (16 with filler particles and 3 without). Dynamic Mechanical Analysis (DMA), performed in accordance with ASTM D4065 using a 0 °C to +45 °C temperature sweep in 3‑point bending, quantified storage modulus (E′), loss modulus (E″), and tan δ.

Results demonstrate that particle selection strongly governs mechanical performance. Nano‑filled systems, particularly nano carbonyl iron and nano magnetite, exhibited the highest stiffness and elevated damping due to increased interfacial surface area and restricted polymer mobility, rendering them unsuitable for compliant actuation. Micro‑scale fillers produced substantially lower stiffness and damping, with micro carbonyl iron at both 40 wt% and 50 wt% showing the most favorable balance of elastic compliance, low viscous losses, and exceptional reproducibility across replicates. These formulations consistently met the target criteria for stiffness (10⁴-10⁶ Pa) and damping (tan δ ≤ 0.2), while maintaining stable performance across the biomedical operating range. In contrast, magnetite‑based composites, especially at 50 wt%, displayed higher stiffness and greater variability, aligning with expected trends in particle-matrix compatibility.

This work provides a controlled comparison of four magnetic filler systems (iron and magnetite, micro and nano size particles) at high loading under uniform processing conditions and establishes clear structure-property relationships relevant to magnetically actuated biomedical devices. The findings directly inform material selection for future MRE-based drug-delivery membranes, soft microfluidic actuators, and magnetically responsive biomedical components.

Research Data and Supplementary Material

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