A Tunable Metamaterial Joint for Mechanical Shock Applications Inspired by Carbon Nanotubes

The significant developments of additive manufacturing and especially 3D-printing technologies have broadened the application field of metamaterials. The present study aims at establishing the main design parameters of a novel 3D-printed polymer-based joint. The proposed joint can efficiently absorb impact energy, relieving the material components from extensive plastic deformations. The design of the machine element is inspired by the molecular structure of carbon nanotubes and appropriately adjusted in such a way that it has the ability to partially transform translational motion to rotational motion and, thus, provide axial structural protection from compressive shocks. The utilized material is a photosensitive resin that is typically utilized in 3D manufacturing processes. Experiments are utilized to characterize the mechanical performance of the raw material as well as the static compressive behavior of the joint. Finally, finite element simulations are performed to test the developed design under impact loadings characterized by different frequencies. The damping capabilities of the metamaterial-based joint are revealed and discussed.

Magnetic resonance imaging with a multi-tunable metamaterial-inspired radiofrequency coil

We present the initial experimental results obtained using a two-part receive/transmit (Rx/Tx) radiofrequency (RF) coil design for small animals magnetic resonance imaging at 7 T. The assembly uses a butterfly-type coil tuned to 300 MHz for scanning the 1H nuclei and a non-resonant antenna with a metamaterial-inspired resonator tunable over wide frequency range for X-nuclei. 1H, 31P, 23Na and 13C are selected as test nuclei in this work. Coil simulations show the two parts of the RF-assembly to be efficiently operating at the required frequencies. Simulations and phantom imaging show sufficiently homogeneous transverse transmit RF fields and tuning capabilities for the pilot heteronuclear experiments.

Terahertz Transmission Characteristics of Double-Layer Plasmonic Metamaterial and LC-Based Structure

In this paper, we present a novel design of an electrically tunable metamaterial device in the terahertz frequency range of 325–500 GHz. The device is analyzed and optimized using an equivalent circuit and numerical simulation. The experimental and simulation results are almost identical in the entire design frequency range. A maximum modulation depth of 90.87% is achieved in the transmission window. The bandpass width decreases from 102.55 to 28.7 GHz as the bias voltage increases from 0 to 30 V. This structure provides new insights into the potential of electrically tunable terahertz devices for a wide range of applications.

­­­­A THZ Tunable Metamaterial Reflective Polarization Converter Based Vanadium Oxide Film

In this paper a simple and tunable reflective polarization converter has been investigated numerically based on metamaterial which composes of a two-corner-cut square patch resonator with a slit embedded into Vanadium dioxide film (VO2) and reflective ground layer. All the results obtained by the CST Microwave Studio show that the polarization conversion ratio (PCR) above 90% is achieved from 2.22-5.42THz at the temperature about 25°C under the linearly and circularly polarized wave incidence normally. In addition, the influences on electromagnetic polarization properties have been demonstrated with the insulator-to-metal phase transition of the Vanadium dioxide film (VO2) film by the method of varying the temperature. At the same time, to be demonstrated, the physical mechanism of changeable polarization conversion has been discussed by the distributions of current densities. According to the results, the designed metamaterial could be applied in the area of temperature-controlled sensing, THz wireless communication, tunable polarized devices.

Shape Memory Alloys and Polymers for MEMS/NEMS Applications: Review on Recent Findings and Challenges in Design, Preparation, and Characterization

Rapid progress in material science and nanotechnology has led to the development of the shape memory alloys (SMA) and the shape memory polymers (SMP) based functional multilayered structures that, due to their capability to achieve the properties not feasible by most natural materials, have attracted a significant attention from the scientific community. These shape memory materials can sustain large deformations, which can be recovered once the appropriate value of an external stimulus is applied. Moreover, the SMAs and SMPs can be reprogrammed to meet several desired functional properties. As a result, SMAs and SMPs multilayered structures benefit from the unprecedented physical and material properties such as the shape memory effect, superelasticity, large displacement actuation, changeable mechanical properties, and the high energy density. They hold promises in the design of advanced functional micro- and nano-electro-mechanical systems (MEMS/NEMS). In this review, we discuss the recent understanding and progress in the fields of the SMAs and SMPs. Particular attention will be given to the existing challenges, critical issues, limitations, and achievements in the preparation and characterization of the SMPs and NiTi-based SMAs thin films, and their heterostructures for MEMS/NEMS applications including both experimental and computational approaches. Examples of the recent MEMS/NEMS devices utilizing the unique properties of SMAs and SMPs such as micropumps, microsensors or tunable metamaterial resonators are highlighted. In addition, we also introduce the prospective future research directions in the fields of SMAs and SMPs for the nanotechnology applications.

Nanoporous gold nanoleaf as tunable metamaterial

We have studied optical properties of single-layer and multi-fold nanoporous gold leaf (NPGL) metamaterials and observed highly unusual transmission spectra composed of two well-resolved peaks. We explain this phenomenon in terms of a surface plasmon absorption band positioned on the top of a broader transmission band, the latter being characteristic of both homogeneous “solid” and inhomogeneous “diluted” Au films. The transmission spectra of NPGL metamaterials were shown to be controlled by external dielectric environments, e.g. water and applied voltage in an electrochemical cell. This paves the road to numerous functionalities of the studied tunable and active metamaterials, including control of spontaneous emission, energy transfer and many others.