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1. Thin Film Enabled Engineered Substrate for Miniaturized Antennas with Improved Bandwidth

   https://doi.org/10.1109/IEEECONF35879.2020.9329840  

   Ge, Jinqun; Wang, Guoan (July 2020, 2020 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting)

   null (Ed.)

   This paper presents a novel engineered substrate enabled by patterned Permalloy (Ni 80 Fe 20 , Py) thin films for the development of miniaturized antenna with improved bandwidth. The perspective substrate is implemented with multiple layers of 100 nm thick Py thin film patterns embedded on arbitrary microwave substrate, and each Py layer consists of an array of Py patterns with a dimension of 15μm×40μm and 5 μm gaps among them to suppress the magnetic loss. An equivalent permeability of 2.398 is achieved for engineered substrate embedding with 10 layers of Py thin films. A simple patch antenna has been implemented on the engineered substrate to demonstrate the efficacy of designing miniaturized antenna with improved bandwidth, compared to antenna on regular substrate, results show that the developed antenna on engineered substrate has a size reduction of 47.3% and an improved bandwidth of 49.6%. 

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2. Characterization of Thin Film Enabled Engineered Substrate for RF Applications

   https://doi.org/10.1109/IEEECONF35879.2020.9330159  

   Ge, Jinqun; Wang, Guoan (July 2020, 2020 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting)

   null (Ed.)

   Engineered substrate enabled by Permalloy (Ni 80 Fe 20 , Py) thin films has been well developed for RF applications with high and tunable permeability and moderate loss. A full investigation on the characteristics of the engineered substrate is presented in this paper. The loss and equivalent permeability generated by the Py patterns are characterized through a microstrip line model. Multiple factors of Py patterns are taken into consideration to define the performance of the engineered substrate, including filling density, thickness, dimensions, and locations. The analytical results give a detailed guideline for the design of engineered substrate. 

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3. Tunable coupling in magnetic thin film heterostructures with a magnetic phase transition

   https://doi.org/10.1038/s41598-023-34322-5  

   Stojak Repa, Kristen; Kirby, Brian J.; Miller, Casey W. (December 2023, Scientific Reports)

   Abstract The magnetic properties of permalloy-based trilayers of the form Py 0.8 Cu 0.2 /Py 0.4 Cu 0.6 /Py/IrMn were studied as the spacer layer undergoes a paramagnetic to ferromagnetic phase transition. We find the coupling between the free Py 0.8 Cu 0.2 layer and the exchange bias pinned Py to be strongly temperature-dependent: there is negligible coupling above the Curie temperature of the Py 0.4 Cu 0.6 spacer layer, strong ferromagnetic coupling below that temperature, and a tunable coupling between these extremes. Polarized neutron reflectometry was used to measure the depth profile of the magnetic order in the system, allowing us to correlate the order parameter with the coupling strength. The thickness dependence shows that these are interface effects with an inverse relationship to thickness, and that there is a magnetic proximity effect that enhances the Curie temperature of the spacer layer with characteristic length scale of about 7 nm. As a demonstration of potential functionality of such a system, the structure is shown to spontaneously flip from the antiparallel to parallel magnetic configuration once the spacer layer has developed long-range magnetic order. 

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4. Integrating microsystems with metamaterials towards metadevices

   https://doi.org/10.1038/s41378-018-0042-1  

   Zhao, Xiaoguang; Duan, Guangwu; Li, Aobo; Chen, Chunxu; Zhang, Xin (January 2019, Microsystems & Nanoengineering)

   Abstract Electromagnetic metamaterials, which are a major type of artificially engineered materials, have boosted the development of optical and photonic devices due to their unprecedented and controllable effective properties, including electric permittivity and magnetic permeability. Metamaterials consist of arrays of subwavelength unit cells, which are also known as meta-atoms. Importantly, the effective properties of metamaterials are mainly determined by the geometry of the constituting subwavelength unit cells rather than their chemical composition, enabling versatile designs of their electromagnetic properties. Recent research has mainly focused on reconfigurable, tunable, and nonlinear metamaterials towards the development of metamaterial devices, namely, metadevices, via integrating actuation mechanisms and quantum materials with meta-atoms. Microelectromechanical systems (MEMS), or microsystems, provide powerful platforms for the manipulation of the effective properties of metamaterials and the integration of abundant functions with metamaterials. In this review, we will introduce the fundamentals of metamaterials, approaches to integrate MEMS with metamaterials, functional metadevices from the synergy, and outlooks for metamaterial-enabled photonic devices. 

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5. Bending behavior of biomimetic scale covered beam with tunable stiffness scales

   https://doi.org/10.1038/s41598-020-74147-0  

   Tatari, Milad; Kamrava, Soroush; Ghosh, Ranajay; Nayeb-Hashemi, Hamid; Vaziri, Ashkan (December 2020, Scientific Reports)

   null (Ed.)

   Abstract Biomimetic scales provide a convenient template to tailor the bending stiffness of the underlying slender substrate due to their mutual sliding after engagement. Scale stiffness can therefore directly impact the substrate behavior, opening a potential avenue for substrate stiffness tunability. Here, we have developed a biomimetic beam, which is covered by tunable stiffness scales. Scale tunability is achieved by specially designed plate like scales consisting of layers of low melting point alloy (LMPA) phase change materials fully enclosed inside a soft polymer. These composite scales can transition between stiff and soft states by straddling the temperatures across LMPA melting points thereby drastically altering stiffness. We experimentally analyze the bending behavior of biomimetic beams covered with tunable stiffness scales of two architectures—one with single enclosure of LMPA and one with two enclosures of different melting point LMPAs. These architectures provide a continuous stiffness change of the underlying substrate post engagement, controlled by the operating temperature. We characterize this response using three-point bending experiments at various temperature profiles. Our results demonstrate for the first time, the pronounced and reversible tunability in the bending behavior of biomimetic scale covered beam, which are strongly dependent on the scale material and architecture. Particularly, it is shown that the bending stiffness of the biomimetic scale covered beam can be actively and reversibly tuned by a factor of up to 7. The developed biomimetic beam has applications in soft robotic grippers, smart segmented armors, deployable structures and soft swimming robots. 

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