Multi-Point Single-Antenna Sensing Enabled by Wireless Nested Split-Ring Resonator Sensors

In this paper, simultaneous multi-point wireless sensing is proposed and demonstrated via multiple sensors in nested split-ring resonator (NSRR) geometry coupled to a single illuminator antenna. In this passive multi-point sensing system, each probe in the sensor array is assigned a non-overlapping spectral interval for frequency shift in response to local mechanical loading around a unique operating resonance frequency in the band of the antenna. Here, it is shown that the antenna is capable of capturing the responses from all probes in a single frequency sweep. Furthermore, the inter-coupling between the array elements and the effect of antenna illumination on the coupling are experimentally investigated in a systematic way. In addition, as a proof-of-concept real-life application in structural health monitoring, two NSRR sensors are located inside a concrete beam to monitor the strain forming on reinforcing bars, and this dual-probe system is demonstrated to record strain simultaneously via both of the embedded probes. © 2001-2012 IEEE

A wireless passive sensing system for displacement/strain measurement in reinforced concrete members

In this study, we show a wireless passive sensing system embedded in a reinforced concrete member successfully being employed for the measurement of relative displacement and strain in a simply supported beam experiment. The system utilizes electromagnetic coupling between the transceiver antenna located outside the beam, and the sensing probes placed on the reinforcing bar (rebar) surface inside the beam. The probes were designed in the form of a nested split-ring resonator, a metamaterial-based structure chosen for its compact size and high sensitivity/resolution, which is at µm/microstrains level. Experiments were performed in both the elastic and plastic deformation cases of steel rebars, and the sensing system was demonstrated to acquire telemetric data in both cases. The wireless measurement results from multiple probes are compared with the data obtained from the strain gages, and an excellent agreement is observed. A discrete time measurement where the system records data at different force levels is also shown. Practical issues regarding the placement of the sensors and accurate recording of data are discussed. The proposed sensing technology is demonstrated to be a good candidate for wireless structural health monitoring (SHM) of reinforced concrete members by its high sensitivity and wide dynamic range. © 2016 by the authors; licensee MDPI, Basel, Switzerland

An electromagnetic sensing system incorporating multiple probes and single antenna for wireless structural health monitoring

In this study, a wireless and passive displacement/strain sensing system is proposed for structural health monitoring (SHM). The wireless and passive interrogation of the sensing unit [a variant of a nested split-ring resonator (NSRR)] is achieved through the near-field interaction and electromagnetic coupling between the single antenna in the system and the multiple sensors called the NSRR probes. It is demonstrated that the system can acquire data from more than one NSRR probe simultaneously in a real-life scenario, where the probes are confined within concrete inside a beam, while the antenna monitors them from outside. © 2017 Euraap

3D Frequency Selective Surface Displacement Sensor using Complementary Dielectrics

A novel displacement sensor using a frequency selective surface (FSS) with a removable substrate complement is proposed. The new concept sensor is based on modifying the effective permittivity of the FSS when the substrate complement is gradually withdrawn. The change in the effective permittivity produces a change in capacitance, and thus in the resonant frequency. The FSS consists of an array of square loops elements in a square lattice. A 3D convoluted version of the FSS sensor improves the angle of incident behavior and increases the displacement range. The dielectric layers of the 3D FSS sensor were 3D printed while the metal layers were painted using silver conductive paint. The transmission response, S 21 , has been employed as the validation parameter. The proposed sensor operates in a frequency range between 2.0 GHz and 2.8 GHz and has achieved a 0.052 GHz/mm sensitivity and 12 mm dynamic range and has a dimension of 207mm by 207mm. The sensor is passive, compact, inexpensive, and easy to operate. The envisaged application is the wireless detection of structural movement, which can be critical in civil structures such as bridges or buildings or earthquake monitoring

Design of a reconfigurable THz filter based on metamaterial wire resonators with applications on sensor devices

A study on the design, simulation and characterization of a reconfigurable terahertz (THz) filter, composed of two frequency-selective surfaces (FSSs) with applications on sensor devices in general and highly sensitive stress sensors, is presented in this paper. Using the developed theoretical model, we found out that by careful tuning the wire parameters, it is possible to control the filter sensitivity and also the energy transmission and reflection that passes through the structure. Numerical modelling of both the mechanical and electromagnetic components (using the elasticity equation and Maxwell’s equations, respectively) has been undertaken for two types of the device assemblies based on different thermoplastic polymers transparent to the THz radiation, namely: high-density polyethylene (HDPE) and polytetrafluoroethylene (PTFE), operating in a THz window from 395 to 455 GHz. The numerical results allowed us to characterize the relation between the reflectance/transmittance and the amount of force required to obtain a specific frequency shift along that window. It was found that the device assembled with HDPE presents a more linear response and it is able to pass from a full transparency to almost full opacity using only its linear operating zone. Due to its characteristics, this THz filter might be an interesting solution not only for THz sensors based on reconfigurable filters but also for optical modulators for the THz domain.info:eu-repo/semantics/publishedVersio

Triple-Band Metamaterial Inspired Antenna for Future Terahertz (THz) Applications

For future healthcare in the terahertz (THz) band, a triple-band microstrip planar antenna integrated with metamaterial (MTM) based on a polyimide substrate is presented. The frequencies of operation are 500, 600, and 880 GHz. The triple-band capability is accomplished by etching metamaterial on the patch without affecting the overall antenna size. Instead of a partial ground plane, a full ground plane is used as a buffer to shield the body from back radiation emitted by the antenna. The overall dimension of the proposed antenna is 484×484 μm2. The antenna's performance is investigated based on different crucial factors, and excellent results are demonstrated. The gain for the frequencies 500, 600, 880GHz is 6.41, 6.77, 10.1 dB, respectively while the efficiency for the same frequencies is 90%, 95%, 96%, respectively. Further research has been conducted by mounting the presented antenna on a single phantom layer with varying dielectric constants. The results show that the design works equally well with and without the phantom model, in contrast to a partially ground antenna, whose performance is influenced by the presence of the phantom model. As a result, the presented antenna could be helpful for future healthcare applications in the THz band

Design of a novel THz sensor for structural health monitoring applications

In this paper, we propose a study on the characterization, design and simulation of a THz sensor for applications in Structural Health Monitoring (SHM). The proposed sensor is assembled using two frequency selective surfaces (FSSs) based on metamaterial wire resonators. We present a theoretical model to describe its electromagnetics which is used not only to understand the physical principles underlying the functioning of the sensor but also to determine a set of optimized parameters for its operation in the THz window from 395 GHz to 455 GHz. We present our numerical simulations, involving both electromagnetic and mechanical simulation techniques, to determine the reflectance profile of the sensor as a function of applied force. In this study we considered the possibility of using two thermoplastic polymers as host materials: High-Density PolyEthylene (HDPE) and PolyTetraFluoroEthylene (PTFE). The two sensors have a good dynamic range and comparable characteristics. However, we found that with HDPE it is possible to construct a sensor with a more linear response, although not as sensitive as in the case of PTFE. With HDPE we are able to pass from a situation of full transparency to almost full opacity using only its linear operating zone.info:eu-repo/semantics/acceptedVersio

Additive Manufactured Antennas and Novel Frequency Selective Sensors

The research work carried out and reported in this thesis focuses on the application of additive manufacturing (AM) for the development antennas and novel frequency selective surfaces structures. Various AM techniques such as direct writing (DW), material extrusion, nanoparticle conductive inks are investigated for the fabrication of antennas and FSS based sensors. This research has two parts. The first involves the development of antennas at the microwave and millimetre wave bands using AM techniques. Inkjet printing of nanoparticle silver inks on paper substrate is employed in the fabrication of antennas for an origami robotic bird. This provides an exploration on the practicability of developing foldable antennas which can be integrated on expendable robots using low-cost household inkjet printers. This is followed using Aerosol jet printing in the fabrication of fingernail wearable antennas. The antennas are developed to operate at microwave and millimetre wave bands for potential use in 5G Internet of Things (IoT) or body-centric networks. The second part of the research work involves the development of frequency selective sensors. Trenches have been incorporated on an FSS structure to produce a new concept of liquid sensor. The sensor is fabricated using standard etching techniques and then using FDM method in conjunction with nanoparticle conductive ink. Finally, a new concept displacement sensor using an FSS coupled with a retracting substrate complement is introduced. The displacement sensor is a 3D structure which is conveniently fabricated using AM techniques

Passive Planar Microwave Devices

The aim of this book is to highlight some recent advances in microwave planar devices. The development of planar technologies still generates great interest because of their many applications in fields as diverse as wireless communications, medical instrumentation, remote sensing, etc. In this book, particular interest has been focused on an electronically controllable phase shifter, wireless sensing, a multiband textile antenna, a MIMO antenna in microstrip technology, a miniaturized spoof plasmonic antipodal Vivaldi antenna, a dual-band balanced bandpass filter, glide-symmetric structures, a transparent multiband antenna for vehicle communications, a multilayer bandpass filter with high selectivity, microwave planar cutoff probes, and a wideband transition from microstrip to ridge empty substrate integrated waveguide

Novel wireless RF-bioMEMS implant sensors of metamaterials

Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Sciences of Bilkent University, 2010.Thesis (Ph. D.) -- Bilkent University, 2010.Includes bibliographical references leaves 301-308.Today approximately one out of ten patients with a major bone fracture does not heal properly because of the inability to monitor fracture healing. Standard radiography is not capable of discriminating whether bone healing is occurring normally or aberrantly. To solve this problem, we proposed and developed a new enabling technology of implantable wireless sensors that monitor mechanical strain on implanted hardware telemetrically in real time outside the body. This is intended to provide clinicians with a powerful capability to asses fracture healing following the surgical treatment. Here we present the proof-of-concept in vitro and ex vivo demonstrations of bio-compatible radio-frequency (RF) micro-electro-mechanical system (MEMS) strain sensors for wireless strain sensing to monitor healing process. The operating frequency of these sensors shifts under mechanical loading; this shift is related to the surface strain of the implantable test material. In this thesis, for the first time, we developed and demonstrated a new class of bio-implant metamaterial-based wireless strain sensors that make use of their unique structural advantages in sensing, opening up important directions for the applications of metamaterials. These custom-design metamaterials exhibit better performance in remote sensing than traditional RF structures (e.g., spiral coils). Despite their small size, these meta-sensors feature a low enough operating frequency to avoid otherwise strong background absorption of soft tissue and yet yield higher Q-factors (because of their splits with high electric field density) compared to the spiral structures. We also designed and fabricated flexible metamaterial sensors to exhibit a high level of linearity, which can also conveniently be used on non-flat surfaces. Innovating on the idea of integrating metamaterials, we proposed and implemented a novel architecture of ‘nested metamaterials’ that incorporate multiple split ring resonators integrated into a compact nested structure to measure strain telemetrically over a thick body of soft tissue. We experimentally verified that this nested metamaterial architecture outperforms classical metamaterial structures in telemetric strain sensing. As a scientific breakthrough, by employing our nested metamaterial design, we succeeded in reducing the electrical length of the sensor chip down to λo/400 and achieved telemetric operation across thick soft tissue with a tissue thickness up to 20 cm, while using only sub-cm implantable chip size (compatible with typical orthopaedic trauma implants and instruments). As a result, with nested metamaterials, we successfully demonstrated wireless strain sensing on sheep’s fractured metatarsal and femur using our sensors integrated on stainless steel fixation plates and on sheep’s spine using directly attached sensors in animal models. This depth of wireless sensing has proved to suffice for a vast portfolio of bone fracture (including spine) and trauma care applications in body, as also supported by ongoing in vivo experiments in live animal models in collaboration with biomechanical and medical doctors. Herein, for all generations of our RF-bioMEMS implant sensors, this dissertation presents a thorough documentation of the device conception, design, modeling, fabrication, device characterization, and system testing and analyses. This thesis work paves the way for “smart” orthopaedic trauma implants, and enables further possible innovations for future healthcare.Melik, RohatPh.D