3D Printing of NiZn ferrite/ABS Magnetic Composites for Electromagnetic Devices
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3D Printing of NiZn ferrite/ABS Magnetic Composites for Electromagnetic Devices Yunqi Wang, Flynn Castles and Patrick S. Grant Department of Materials, Parks Road, Oxford, OX1 3PH, U.K.
ABSTRACT 3D printing is a versatile fabrication method that offers the potential to realize complex 3D devices with metamaterial characteristics in a single process directly from a computer aided design. However, the range of functional devices that might be realized by 3D printing is limited by the current range of materials that are compatible with a given 3D printing process: fused deposition modelling (FDM), which is a widely used 3D printing method, typically employs only common thermoplastics. Here we describe the development of a magnetic feedstock based on polymer-ferrite composite that is compatible with FDM. The feasibility of the technique is demonstrated by the permittivity and permeability measurement of direct printed blocks and the fabrication of a complex 3D diamond-like lattice structure. The development of printable magnetic composites provides increased design freedom for direct realization of devices with graded electromagnetic properties operating at microwave frequencies. INTRODUCTION Metamaterials have been extensively investigated for manipulating electromagnetic waves in ways useful to practical applications. Starting from arrays of metallic resonators, such as split rings [1], spirals [2], and conducting nanowires [3,4], at microwave frequencies, special physical phenomena including negative permittivity, permeability, and refractive index have been demonstrated. However, dispersive combinations of metallic resonators result in undesired reflections and dissipation that reduce the output of devices. For integration of metamaterials into designs, spatial transformation (ST) can be used to predict how spatial variations in the permittivity and permeability of materials can be used to control and direct electromagnetic waves in unprecedented ways [5], including the use of non-resonant but graded “all-dielectric” materials with wider bandwidth and lower loss. Despite significant progress, practical challenges remain in device fabrication, in particular the need to reliably realize spatial variations in permittivity and permeability, which, for microwaves, must take place over a few mm to several cm’s, and with a “dynamic range” (difference in the lowest to highest permittivity or permeability) that is most useful when it as large as possible. Fused deposition modelling (FDM) is an additive manufacturing process that can place different thermoplastic polymers at different locations in three dimensions with ~100 μm precision, and has been used for the fabrication of devices that operate at microwave frequencies, including an X-band Luneburg Lens where the gradient permittivity ranged from 1.01 to 2.7 by the mixing ratio of air (voids in the structure) and polymer [6], an anisotropic material using a printed spatially varying lattice [7,8], a meander line dipole antenna [9], and channel emulator [10]. However so f
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