Session: SYMP 1-2: Shape Memory Polymers

Paper Number: 140167

140167 - Towards Complex Shape Actuation: An Investigation of Local and Global Magnetoactive Gradients in 3d-Printed Multi-Stimuli Responsive Shape Memory Polymer Composites 

In this research, we investigate multi-stimuli responsive multi-material structures by combining shape memory polymers (SMPs) with magnetoactive fillers. Our objective is to design 3D-printed composites with local and global magnetoactive filler gradients, enabling them to exhibit complex shape actuation under magnetic and thermal fields. We first carry out a rheological study of SMP dispersions containing surface-treated magnetic particles to understand the effect of magnetic particle surface treatment, additives content, and shear rate on the complex flow behavior. Our findings reveal that dispersions filled with surface-treated magnetic particles exhibit enhanced shear thinning behavior and shape integrity compared to unfunctionalized dispersions. The improved rheological behavior and shape integrity are important results that indicate that PEG-functionalized SMP composites are promising candidates for 3D printing using direct ink printing. To create complex actuation, a 3D printing system was designed in a way that the magnetic particle-SMP dispersions are oriented using shear and an external magnetic field, enabling the composite to develop a local angular gradient of magnetic particles. In addition, a global gradient is designed-in by controlling the volume fraction of magnetic particles in the SMP suspensions. To ensure the rheological properties of the SMP_Silica_Fe3O4_PEG mixtures remain consistent across varying Fe₃O₄ concentrations, rheological adjustments are made to the SMP_Silica_Fe₃O₄_PEG30 mixtures. This understanding of the rheological behavior allows us to maintain the viscosity variations to below 4 Pa.s, while the range of both the power law index and power law constant is between 0.56-0.72 and 9-16, respectively. Modeling the flow behavior of this non-Newtonian fluid within a tube confirms that the rheological characteristics of the inks remain stable under flow rate of 930 ml/s. By adjusting the local and global gradients of magnetic particles within the SMP, different actuation patterns can be achieved. SEM analysis confirms the presence of the global gradient in iron oxide particles and their alignment along the magnetic field direction post-printing. Vibrating Sample Magnetometry (VSM) studies reveal an improved mass magnetization along the length of the printed samples, moving away from the printing origin. In addition, and based on the VSM results, the iron oxide weight percent in the samples increases from 2.5 wt.% at the printing origin to 12.5wt.% at the end, creating a pronounced Fe₃O₄ global gradient. These findings contribute to the development of advanced stimuli-responsive materials with tunable properties for various applications where complex shape actuation is required, including soft robotics, and biomedical devices.

Presenting Author: Mohammad Hossein Zamani Pennsylvania State University

Presenting Author Biography: Mohammad Hossein Zamani is a Ph.D. candidate in Mechanical Engineering at the Pennsylvania State University. Mr. Zamani obtained his BSc and MSc in Polymer Engineering from Amirkabir University of Technology and the University of Tehran, respectively, specializing in smart polymer nanocomposite systems. He joined Penn State in Spring 2023. Currently, Mr. Zamani is researching shape memory polymers, 4D printing, and magneto-active elastomers to develop multifield-responsive polymer composite systems.

Authors:

Mohammad Hossein Zamani
Daniel Raymond Strobel
Zoubeida Ounaies