A wide variety of engineered materials have been developed that exhibit advanced magneto-dielectric properties. Such materials can significantly extend the range of microwave characteristics found in common substrates, thus improving the performance of microwave components. In particular, ferrites, ferroelectrics and multiferroics have been widely studied as functional materials with enhanced microwave properties while enabling tunable and low-loss microwave devices. In addition, polymer nanocomposites with unique absorption properties have been identified as an effective functional material for microwave electromagnetic interference (EMI) shielding. Emerging types of metamaterials show promising magneto-dielectric properties. These materials often involve the inclusion of multiple layers and/or periodic resonant arrays in order to produce tailored microwave properties, although typically within a relatively small bandwidth. Magneto-dielectrics have been shown to enable considerable improvements in the bandwidth and/or size reduction of microwave devices, such as antennas. However, the prior art implementations do not simultaneously satisfy many crucial requirements for microwave device applications, such as low dielectric and magnetic losses, low power consumption, low biasing electric or magnetic fields, structural simplicity and ease of integration with existing fabrication processes.
One of the promising ways to develop materials showing magneto-dielectric properties is to exploit polymer composites reinforced with magnetic nanoparticles. However, the dispersion of in-organic nanoparticles into a polymer matrix has been a challenging task for nanocomposite fabrication. Since the polymer matrix and inorganic nanoparticles often possess different polarities, a simple blending of particles and polymer will result in aggregation of particles and poor particle-to-polymer interfacial properties. In fabrication of magneto-dielectric materials, the key challenge is the formation of morphologically controlled and highly ordered arrays of nanoparticles over an extended area or volume.
Due to the challenges in the development of these magneto-dielectric materials, there has been very little progress in exploring their potential for tunable and/or low-loss microwave device applications. There is still a need for improvement with respect to keeping the enhanced magneto-dielectric properties in a wider frequency range, lowering fabrication complexity and reducing size and cost. As a result, extensive utilization of polymer nanocomposites has yet to occur.
Additionally, the magneto-dielectric polymer composite materials currently known in the art are solvent diluted, low-viscosity polymers that have limited applications and must be spin-coated onto the surface of a supporting substrate. The resulting thin films (approximately 2 μm) must be supported by the substrate, which prevents the magneto-dielectric polymer composite materials currently known in the art from being used in 3D printing, compression molding or injection molding application.
Accordingly, there is a need in the art for a low-loss microwave material which exhibits wide tunability of its effective dielectric and magnetic properties, which does not require a supporting substrate and can be amenable to additive manufacturing, compression molding or injection molding processes.