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Abstract In this research, we investigate multi-stimuli responsive multimaterial 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, which 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 direct ink printing. To create complex actuation, a 3D printing system is designed in a way that the magnetic particle-SMP dispersions are oriented using both shear and an external magnetic field, enabling a local angular gradient of magnetic particles. In addition, a global gradient is designed-in by varying the volume fraction of magnetic particles in the SMP suspensions. 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, 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.
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Boron nitride-based shape memory polymers for spatially targeted ultrasound actuation
Abstract Focused ultrasound (FUS) presents unique advantages for noninvasive localized heating, crucial for controlled shape recovery in shape memory polymers (SMPs), especially in biomedical applications. To enhance FUS-driven actuation efficiency, we propose boron nitride (BN)-infused SMP composites (SMPCs) tailored for targeted biomedical interventions. Using tert-butyl acrylate (tBA) and di(ethylene glycol) dimethacrylate as base materials, we integrated BN fillers at varying concentrations (1, 5, and 10 wt.%). A thorough characterization was carried out, including dynamic mechanical analysis, scanning electron microscopy, uniaxial tensile testing, and swelling study. These results show that increasing the BN content improves shape recovery efficiency significantly. Specifically, the 10 wt.% BN composites outperformed plain SMP in terms of shape recovery ratio when activated with FUS, and the highest shape recovery ratio can achieve 75%. However, higher BN content decreases crosslinking density and stiffness, as shown by a lower Young’s modulus and glass transition temperature. This study demonstrates the promise of BN-infused SMPCs for advanced applications in biomedical application, where noninvasive spatiotemporal actuation of SMPs is required.
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- Award ID(s):
- 2016474
- PAR ID:
- 10614261
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Smart Materials and Structures
- Volume:
- 34
- Issue:
- 7
- ISSN:
- 0964-1726
- Format(s):
- Medium: X Size: Article No. 075018
- Size(s):
- Article No. 075018
- Sponsoring Org:
- National Science Foundation
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