Battery-Free Antenna Sensors for Strain and Crack Monitoring: Technical Report

This project studies a wireless patch antenna as a novel strain/crack sensing technique for structural health monitoring (SHM). The strain/crack induced resonance frequency shift of the antenna can be wirelessly detected and utilized to estimate the surface strain and crack propagation. However, temperature fluctuation can generate some unwanted changes in resonance frequency and introduce significant noises in measurement. This project studies a thermally stable patch antenna sensor through both numerical simulations and laboratory experiments. Using a substrate material with a steady dielectric constant, a patch antenna sensor is designed to perform reliably under temperature fluctuations. In addition, a dual-mode patch antenna sensor is designed to achieve long interrogation distance. Various types of materials used in substrate are investigated through laboratory tests. Strain/crack sensing performance has been validated through multi-physics simulations and experiments. The patch antenna sensors are demonstrated to be effective in wireless strain/crack measurements and have potential for large-scale monitoring of structures

Micro/Nano Structures and Systems

Micro/Nano Structures and Systems: Analysis, Design, Manufacturing, and Reliability is a comprehensive guide that explores the various aspects of micro- and nanostructures and systems. From analysis and design to manufacturing and reliability, this reprint provides a thorough understanding of the latest methods and techniques used in the field. With an emphasis on modern computational and analytical methods and their integration with experimental techniques, this reprint is an invaluable resource for researchers and engineers working in the field of micro- and nanosystems, including micromachines, additive manufacturing at the microscale, micro/nano-electromechanical systems, and more. Written by leading experts in the field, this reprint offers a complete understanding of the physical and mechanical behavior of micro- and nanostructures, making it an essential reference for professionals in this field

Suivi immergé de durabilité du béton par nano capteurs sans fil

Making the construction industry more sustainable requires the extension of the life of structures, achievable through the anticipation of structural deficiencies. Structural deficiencies often originate at the core of concrete structures from micro scale defects, whose detection is the key to predict structural ageing. The in-situ, real-time detection of such defects remains a major scientific and technological challenge and no cost effective technique is currently available. In this thesis, we present the design, fabrication and validation of the first wireless nano sensor node for embedded monitoring of concrete structures.The device is composed of 3 main parts: a sensing element, a conditioning circuit and an antenna. The first is a highly reproducible, hysteresis-free, flexible sensor fabricated by inkjet printing carbon nanotubes (CNTs) on polymer. We achieved the batch production of more than 140 sensors and also demonstrated low dispersion in device resistance as well as in its sensitivity to strain and temperature. The sensor also responds to humidity and pH, indicating that this fabrication process is adapted to the creation of a multifunctional nano sensor.The low-cost, low-power conditioning circuit adapts the sensors’ output to the input requirements of a regular analog-to-digital converter (ADC), compensating for temperature sensitivity. The antenna is specifically designed to maximise transmission through concrete for the wireless communication of the measurements. Power is supplied by a battery enabling the operation of the node for over 5 years. The circuitry is housed in a protective casing to insulate it from the harsh concrete environment. The volume of the assembled device is more than 3 times smaller than state of the art embedded nodes for concrete.The devices are tested both in laboratory conditions and in real-size concrete structures. The outputs of the sensors embedded in a mortar slab under 3-point bending tests suggest that the devices are capable of detecting the opening of micro cracks caused by increasing load. Moreover, continuous outdoor deployment since December 2014 demonstrates that this setup may be capable of detecting thermal-induced micrometric deformations and suggests that our technology provides a higher durability for embedded monitoring than commercial metallic strain gauge. In conclusion, the scientific and technological results of this research show the strong applicative potential of wireless nano sensors for embedded monitoring of concrete materials.Mettre en œuvre le développement durable en construction nécessite de prolonger la durée de vie des structures grâce à la détection précoce des fragilités structurales. Celles-ci trouvent très souvent leur origine au cœur même des structures, au niveau de défauts micrométriques. Détecter ces défauts in situ et en temps réel représente un défi scientifique et technologique majeur et aucune solution bas coût n’est actuellement disponible. Cette thèse présente le premier nanocapteur intelligent sans fil pour le suivi noyé des structures en béton. Le système est composé de trois parties : un élément sensible, un circuit de conditionnement du signal, et une antenne. Le premier est un capteur de déformation fabriqué par impression jet d’encre de nanotubes de carbone sur polymère. Ces capteurs sont fabriquées en série, jusqu’à 140 à la fois. Ils ne présentent pas d’hystérésis, résistent aux cyclages mécaniques, et sont très reproductibles en termes de résistance et de sensibilité (en température et en déformation) au sein d’une même série. Les capteurs sont sensibles également au pH et à l’humidité, ce qui suggère que cette technologie pourrait être adaptée à la création de nano capteurs multifonctionnels. Le circuit de conditionnement est à bas coût et faible consommation énergétique. Il met en forme le signal du capteur tout en compensant sa sensibilité à la température. L’antenne a été conçue pour maximiser sa portée à cœur du béton, permettant ainsi la communication sans fil des mesures du capteur vers l’utilisateur. Le système, protégé par un boitier spécialement conçu, est alimenté par une batterie pour une durée de vie estimée à plus de 5 ans. Le volume total du système final est plus de 3 fois inférieur à l’état de l’art des capteurs noyés.De nombreuses expériences en laboratoire ainsi que dans une structure en béton de taille réelle suggèrent que le dispositif est capable d’observer à la fois l’ouverture de micro fractures dues à des charges appliquées et les déformations micrométriques dues à des dilatations thermiques. De plus, nos capteurs à base de nanotubes ont montré une durabilité plus importante au cœur du béton que des capteurs de déformation métalliques commerciaux. En conclusion, les résultats scientifiques et technologiques de ces travaux montrent le fort potentiel applicatif des nano capteurs sans fil pour l’instrumentation noyée des matériaux cimentaires

Passively-coded embedded microwave sensors for materials characterization and structural health monitoring (SHM)

Monitoring and maintaining civil, space, and aerospace infrastructure is an ongoing critical problem facing our nation. As new complex materials and structures, such as multilayer composites and inflatable habitats, become ubiquitous, performing inspection of their structural integrity becomes even more challenging. Thus, novel nondestructive testing (NDT) methods are needed. Chipless RFID is a relatively new technology that has the potential to address these needs. Chipless RFID tags have the advantage of being wireless and passive, meaning that they do not require a power source or an electronic chip. They can also be used in a variety of sensing applications including monitoring temperature, strain, moisture, and permittivity. However, these tags have yet to be used as embedded sensors. By embedding chipless RFID tags in materials, materials characterization can be performed via multi-bit sensing; that is, looking at how the multi-bit code assigned to the response of the tag changes as a function of material. This thesis develops this method through both simulation and measurement. In doing so, a new coding method and tag design are developed to better support this technique. Furthermore, inkjet-printing is explored as a manufacturing method for these tags and various measurement methods for tags including radar cross-section and microwave thermography are explored --Abstract, page iii

Reconfigurable Antennas Using Liquid Crystalline Elastomers

This dissertation demonstrates the design of reversibly self-morphing novel liquid crystalline elastomer (LCE) antennas that can dynamically change electromagnetic performance in response to temperature. This change in performance can be achieved by programming the shape change of stimuli-responsive (i.e., temperature-responsive) LCEs, and using these materials as substrates for reconfigurable antennas. Existing reconfigurable antennas rely on external circuitry such as Micro-Electro-Mechanical-Systems (MEMS) switches, pin diodes, and shape memory alloys (SMAs) to reconfigure their performance. Antennas using MEMS or diodes exhibit low efficiency due to the losses from these components. Also, antennas based on SMAs can change their performance only once as SMAs response to the stimuli and is not reversible. Flexible electronics are capable of morphing from one shape to another using various techniques, such as liquid metals, hydrogels, and shape memory polymers. LCE antennas can reconfigure their electromagnetic performance, (e.g., frequency of operation, polarization, and radiation pattern) and enable passive (i.e., battery-less) temperature sensing and monitoring applications, such as passive radio frequency identification device (RFID) sensing tags. Limited previous work has been performed on shape-changing antenna structures based on LCEs. To date, self-morphing flexible electronics, including antennas, which rely on stimuli-responsive LCEs that reversibly change shape in response to temperature changes, have not been previously explored. Here, LCE antennas will be studied and developed. Also, the metallization of LCEs with different metal conductors and their fabrication process, by either electron beam (E-Beam) evaporation or optical gluing of the metal film will be observed. The LCE material can have a significant impact on sensing applications due to its reversible actuation that can enable a sensor to work repeatedly. This interdisciplinary research (material polymer science and electrical engineering) is expected to contribute to the development of morphing electronics, including sensors, passive antennas, arrays, and frequency selective surfaces (FSS)

The 3rd International Conference on the Challenges, Opportunities, Innovations and Applications in Electronic Textiles

This reprint is a collection of papers from the E-Textiles 2021 Conference and represents the state-of-the-art from both academia and industry in the development of smart fabrics that incorporate electronic and sensing functionality. The reprint presents a wide range of applications of the technology including wearable textile devices for healthcare applications such as respiratory monitoring and functional electrical stimulation. Manufacturing approaches include printed smart materials, knitted e-textiles and flexible electronic circuit assembly within fabrics and garments. E-textile sustainability, a key future requirement for the technology, is also considered. Supplying power is a constant challenge for all wireless wearable technologies and the collection includes papers on triboelectric energy harvesting and textile-based water-activated batteries. Finally, the application of textiles antennas in both sensing and 5G wireless communications is demonstrated, where different antenna designs and their response to stimuli are presented

Structural Health Monitoring of Fatigue Cracks for Steel Bridges With Wireless Large-Area Strain Sensors

This paper presents a field implementation of the structural health monitoring (SHM) of fatigue cracks for steel bridge structures. Steel bridges experience fatigue cracks under repetitive traffic loading, which pose great threats to their structural integrity and can lead to catastrophic failures. Currently, accurate and reliable fatigue crack monitoring for the safety assessment of bridges is still a difficult task. On the other hand, wireless smart sensors have achieved great success in global SHM by enabling long-term modal identifications of civil structures. However, long-term field monitoring of localized damage such as fatigue cracks has been limited due to the lack of effective sensors and the associated algorithms specifically designed for fatigue crack monitoring. To fill this gap, this paper proposes a wireless large-area strain sensor (WLASS) to measure large-area strain fatigue cracks and develops an effective algorithm to process the measured large-area strain data into actionable information. The proposed WLASS consists of a soft elastomeric capacitor (SEC) used to measure large-area structural surface strain, a capacitive sensor board to convert the signal from SEC to a measurable change in voltage, and a commercial wireless smart sensor platform for triggered-based wireless data acquisition, remote data retrieval, and cloud storage. Meanwhile, the developed algorithm for fatigue crack monitoring processes the data obtained from the WLASS under traffic loading through three automated steps, including (1) traffic event detection, (2) time-frequency analysis using a generalized Morse wavelet (GM-CWT) and peak identification, and (3) a modified crack growth index (CGI) that tracks potential fatigue crack growth. The developed WLASS and the algorithm present a complete system for long-term fatigue crack monitoring in the field. The effectiveness of the proposed time-frequency analysis algorithm based on GM-CWT to reliably extract the impulsive traffic events is validated using a numerical investigation. Subsequently, the developed WLASS and algorithm are validated through a field deployment on a steel highway bridge in Kansas City, KS, USA