*Article* **Development and Characterization of Field Structured Magnetic Composites**

**Balakrishnan Nagarajan <sup>1</sup> , Yingnan Wang <sup>1</sup> , Maryam Taheri 2,3, Simon Trudel <sup>2</sup> , Steven Bryant <sup>3</sup> , Ahmed Jawad Qureshi <sup>1</sup> and Pierre Mertiny 1,\***


**Abstract:** Polymer composites containing ferromagnetic fillers are promising for applications relating to electrical and electronic devices. In this research, the authors modified an ultraviolet light (UV) curable prepolymer to additionally cure upon heating and validated a permanent magnet-based particle alignment system toward fabricating anisotropic magnetic composites. The developed dual-cure acrylate-based resin, reinforced with ferromagnetic fillers, was first tested for its ability to polymerize through UV and heat. Then, the magnetic alignment setup was used to orient magnetic particles in the dual-cure acrylate-based resin and a heat curable epoxy resin system in a polymer casting approach. The alignment setup was subsequently integrated with a material jetting 3D printer, and the dual-cure resin was dispensed and cured in-situ using UV, followed by thermal post-curing. The resulting magnetic composites were tested for their filler loading, microstructural morphology, alignment of the easy axis of magnetization, and degree of monomer conversion. Magnetic characterization was conducted using a vibrating sample magnetometer along the in-plane and out-of-plane directions to study anisotropic properties. This research establishes a methodology to combine magnetic field induced particle alignment along with a dual-cure resin to create anisotropic magnetic composites through polymer casting and additive manufacturing.

**Keywords:** magnetic polymer composites; anisotropic properties; dual-cure resin; polymer casting; additive manufacturing
