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Magnetic-actuated electrospun shape memory mats Wang, Xirui


Shape memory materials are the materials that can be deformed and fixed to a temporary shape and recover their original shape on exposure to external stimulus. Shape memory properties have been widely used for various applications such as actuators, adaptive mateirals and so on. This study firstly imparts this special property to nanofibers in light of various advantages including nanoporous structure, excellent recoverability and good biocompatibility. Then magnetite nanoparticles are incorporated into this system to realize the magnetic actuation of shape memory effect. In the first stage, poly (ɛ-caprolactone)-based polyurethane nanofibers were successfully fabricated by means of electrospinning. Through cyclic tensile testing, it was shown that in comparison with shape memory bulk films, the polyurethane shape memory nanofiber nonwovens had better shape recovery ability ascribed to molecular orientation. In the second stage, magnetite was successfully incorporated into polyurethane shape memory mats through the sonic mixing and subsequently the electrospinning process. SEM images showed that the fibers became more uniform and the diameter increased after magnetite incorporation. Differential scanning calorimetry and dynamic mechanical analysis revealed that the magnetite-incorporated mats still featured the melting transition which was similar with the pure mats, providing the magnetite-incorporated mats large possibilities to have shape memory effect. Through cyclic tensile testing, the recovery ratio decreased slightly because incorporated magnetite nanoparticles damaged the polyurethane matrix continuity. Moreover, electrospun mats with 5 wt%, 7.5 wt%, and 10 wt% magnetite were able to be heated to above their transition temperatures under a magnetic field with strength of 0.03T and frequency of 410 kHz. Helix recovery directly demonstrated that shape memory effect of magnetite-incorporated electrospun mats could be triggered under a specific magnetic field. Magnetic-actuated electrospun shape memory mats hold great potential for biomedical applications such as scaffolds in tissue engineering and drug delivery matrix in drug releasing system.

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