Application Issues Using Fibre Bragg Gratings as Strain Sensors in Fibre Composites

Abstract: Fibre Bragg grating sensors have been developed as a strain measurement technique. With regard to practical applications, there is growing knowledge and experience. However, many application issues remain unsolved. These issues include signal interpretation, confidence in measurement accuracy, calibration, and zero-strain definition. This paper reports some issues which have been encountered in practical measurements and application trials. The investigation covers various aspects of strain measurement. The measurement accuracy in a composite laminate is found to be influenced by the formation of cracks in adjoined layers, interface between fibre sensor and host materials and nonuniform stress fields.     

Nanostructured Materials for Room‐Temperature Gas Sensors

Sensor technology has an important effect on many aspects in our society, and has gained much progress, propelled by the development of nanoscience and nanotechnology. Current research efforts are directed toward developing high‐performance gas sensors with low operating temperature at low fabrication costs. A gas sensor working at room temperature is very appealing as it provides very low power consumption and does not require a heater for high‐temperature operation, and hence simplifies the fabrication of sensor devices and reduces the operating cost. Nanostructured materials are at the core of the development of any room‐temperature sensing platform. The most important advances with regard to fundamental research, sensing mechanisms, and application of nanostructured materials for room‐temperature conductometric sensor devices are reviewed here. Particular emphasis is given to the relation between the nanostructure and sensor properties in an attempt to address structure–property correlations. Finally, some future research perspectives and new challenges that the field of room‐temperature sensors will have to address are also discussed.     

大型结构应变场光纤分布监测系统

研究了一种用于大型工程结构应变、变形状态监测的基于光时域反射技术的分布式光纤应变传感系统。设计了一种新型的光纤微弯传感器结构,用于对沿传感光纤分布各测量点的应变信息进行提取;在此新结构的基础上,了全光纤型应变传感器串行阵列,以对构件应变测量和安全监测为主要目标,建立了起了分布光纤应变实时监测系统,进行了系统实验了得到了良好的结构。     

Wet-Style Superhydrophobic Antifogging Coatings for Optical Sensors

Transparent substrates are widely used for optical applications from lenses for personal and sports eyewear to transparent displays and sensors. While these substrates require excellent optical properties, they often suffer from a variety of environmental challenges such as excessive fogging and surface contamination. In this work, it is demonstrated that a wet-style superhydrophobic coating, which simultaneously exhibits antifogging, antireflective, and self-cleaning properties, can be prepared by pattern transferring low-surface-energy microstructures onto a heterostructured nanoscale thin film comprising polymers and silica nanoparticles. The polymer–silica nanocomposite base layer serves as a hydrophilic reservoir, guiding the water molecules to preferentially condense into this underlying region and suppress reflection, while the low-surface-energy microstructure enables contaminants adsorbed on the surface to be easily removed by rinsing with water.     

工程结构光纤应变传感器

研究了一种用于土木工程结构监测的本征型强度调制光纤传感器，其敏感部分是利用光刻技术在多模光纤上形成的齿槽周期结构。详细分析了该传感器原理，首次得到这种传感器既能测量拉就变，也能测量压应变的统一表示公式。传感器对应变的响应具有 线性变和重复性，而且应变灵敏度完全由敏感元结构参数决定。     

Polymer-Grafted,Gold Nanoparticle-Based Nano-Capsules as Reversible Colorimetric Tensile Strain Sensors

Colloidal colorimetric microsensors enable the in-situ detection of mechanical strains within materials. Enhancing the sensitivity of these sensors to small scale deformation while enabling reversibility of the sensing capability would expand their utility in applications including biosensing and chemical sensing. In this study, we introduce the synthesis of colloidal colorimetric nano-sensors using a simple and readily scalable fabrication method. Colloidal nano sensors are prepared by emulsion-templated assembly of polymer-grafted gold nanoparticles (AuNP). To direct the adsorption of AuNP to the oil-water interface of emulsion droplets, AuNP (≈11nm) are functionalized with thiol-terminated polystyrene (PS, M_n = 11k). These PS-grafted gold nanoparticles are suspended in toluene and subsequently emulsified to form droplets with a diameter of ≈30µm. By evaporating the solvent of the oil-inwater emulsion, we form nanocapsules (AuNC) (diameter < 1µm) decorated by PS-grafted AuNP. To test mechanical sensing, the AuNC are embedded in an elastomer matrix. The addition of a plasticizer reduces the glass transition temperature of the PS brushes, and in turn imparts reversible deformability to the AuNC. The plasmonic peak of the AuNC shifts towards lower wavelengths upon application of uniaxial tensile tension, indicating increased inter-nanoparticle distance, and reverts back as the tension is released.     

全印制柔性应变传感器的原理与智能包装应用

目的随着可穿戴电子技术的快速发展,因具有较高的传感系数,柔性应变传感器在电子皮肤和机器人领域得到了广泛关注,但如何降低其制造成本成为一种挑战。近年来,印刷电子技术的快速发展推动了柔性应变传感器的发展,并逐渐在一些新的领域得到应用,尤其是智能包装领域。方法结合课题组在全印制应变传感器方面的研究进展,对柔性传感器的原理、印刷制造方法和主要应用进行综述。结论大量的研究表明,印刷柔性应变传感器已经开始应用于智能包装中,利用印刷电子技术制造智能包装也有利于降低其制造成本,推动其走向实际应用。     

The Time Stability of Integrated Sensors as the Most Important Condition for Their Use in Aviation Microprocessor Systems

The main structural and technological methods which enable the technical level of sensors to be improved are classified by analyzing publications on the technical parameters of modern integrated pressure sensors and methods of improving their stability.     

Nanostructured Complex Cobalt Oxides as Potential Materials for Solar Thermoelectric Power Generators

Thermoelectrically active and stable perovskite‐type materials e.g. La_1–xCa_xCoO₃ (0<x<0.4), La_1–xCa_xCo_0.99Ti_0.01O₃ (0<x<0.2), and Ca₃Co₄O₉ have been successfully synthesized using selected precursor compounds. This soft chemistry route allows the control of the elemental composition from 1% level to 50% substitution. Accordingly the Co valency and therefore the transport properties of the product phases can be controlled. It has been found that the pH of the precursor solution results in a pronounced influence on the morphology of the products. The thermoelectric values measured of the nanostructured “misfit cobaltite Ca₃Co₄O₉” shows a Seebeck coefficient of S_300K ～ + 123 μVK^–1, and a resistivity of ρ ～ 1.9 mΩ cm at room temperature, which is comparable to the reported value for single crystals. Ca‐ and Ti‐substituted LaCoO₃ reveal thermopower values in the range from S_300K ～ + 70 to + 180 μVK^–1. The electrical conductivity of the nanostructured compounds is high in spite of the fact that the grain boundary influence is increasing. The Seebeck coefficient values of the products are positive in the whole temperature range indicating p‐type conduction.     

Nanostructured Polymeric Coatings Based on Chitosan and Dopamine‐Modified Hyaluronic Acid for Biomedical Applications

In a marine environment, specific proteins are secreted by mussels and used as a bioglue to stick to a surface. These mussel proteins present an unusual amino acid 3,4‐dihydroxyphenylalanine (known as DOPA). The outstanding adhesive properties of these materials in the sea harsh conditions have been attributed to the presence of the catechol groups present in DOPA. Inspired by the structure and composition of these adhesive proteins, dopamine‐modified hyaluronic acid (HA‐DN) prepared by carbodiimide chemistry is used to form thin and surface‐adherent dopamine films. This conjugate was characterized by distinct techniques, such as nuclear magnetic resonance and ultraviolet spectrophotometry. Multilayer films are developed based on chitosan and HA‐DN to form polymeric coatings using the layer‐by‐layer methodology. The nanostructured films formation is monitored by quartz crystal microbalance. The film surface is characterized by atomic force microscopy and scanning electron microscopy. Water contact angle measurements are also conducted. The adhesion properties are analyzed showing that the nanostructured films with dopamine promote an improved adhesion. In vitro tests show an enhanced cell adhesion, proliferation and viability for the biomimetic films with catechol groups, demonstrating their potential to be used in distinct biomedical applications.     

Carbon Nanotube Yarn for Fiber-Shaped Electrical Sensors,Actuators, and Energy Storage for Smart Systems

Smart systems are those that display autonomous or collaborative functionalities, and include the ability to sense multiple inputs, to respond with appropriate operations, and to control a given situation. In certain circumstances, it is also of great interest to retain flexible, stretchable, portable, wearable, and/or implantable attributes in smart electronic systems. Among the promising candidate smart materials, carbon nanotubes (CNTs) exhibit excellent electrical and mechanical properties, and structurally fabricated CNT-based fibers and yarns with coil and twist further introduce flexible and stretchable properties. A number of notable studies have demonstrated various functions of CNT yarns, including sensors, actuators, and energy storage. In particular, CNT yarns can operate as flexible electronic sensors and electrodes to monitor strain, temperature, ionic concentration, and the concentration of target biomolecules. Moreover, a twisted CNT yarn enables strong torsional actuation, and coiled CNT yarns generate large tensile strokes as an artificial muscle. Furthermore, the reversible actuation of CNT yarns can be used as an energy harvester and, when combined with a CNT supercapacitor, has promoted the next-generation of energy storage systems. Here, progressive advances of CNT yarns in electrical sensing, actuation, and energy storage are reported, and the future challenges in smart electronic systems considered.     

Thick Graded Nanostructured Zirconia-NiCoCrAlY Composite Coatings by Plasma Spraying

Thick Nanostructured PSZ-NiCoCrAlY graded TBCs were got byair plasma spraying. The results reveal the morphology and phase transformation of TBCs by means of SEM and XRD. The plasma spray process results in a characteristic layered structure consisting of lamellae, unmelted nano-particles and an inter-lamellar porosity. The test results of thermal shock show that the graded coatings have different failure behavior. The failure mode was the spallation of top coat due to thermal stress. It has been found that the lamella consists of nanoscale columnar grains parallel to the spraying direction.     

Fabrication and Characterization of Single-Layer Textile-Based Flexible Pressure Sensors for Smart Wearable Electronics Applications

Textile-based sensors have been widely studied for wearable monitoring. The sensor systems demand a large sensing area, flexibility, and scalable fabrication method. Herein, single-layer piezoresistive sensors are developed by a machine stitching technique using metallic and graphene nanoplatelets-coated conductive threads and fabrics. The pressure-sensing mechanism is based on measuring the electrical resistance due to the change in the contact area between the conductive thread and fabric as pressure on the sensor varies. The single-layer sensor design provides flexibility and overcomes the physical drift of the sensor during human activities, which enhances wearability and performance. The coated textiles are characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy. Physical and electromechanical tests are performed on the sensors to evaluate their wearability and sensing performance. The sensors exhibit a wide working range of up to 100 kPa and good sensitivity with excellent durability against repeated mechanical deformations. The application potential of the sensors in real-time monitoring is demonstrated by embedding them into clothing as a wearable device. Moreover, the effectiveness of the sensors is tested for posture correction. This article suggests a novel technique to fabricate durable, flexible, and highly efficient pressure sensors for smart wearable applications.     

VO2/TiN Plasmonic Thermochromic Smart Coatings for Room‐Temperature Applications

Vanadium dioxide/titanium nitride (VO₂/TiN) smart coatings are prepared by hybridizing thermochromic VO₂ with plasmonic TiN nanoparticles. The VO₂/TiN coatings can control infrared (IR) radiation dynamically in accordance with the ambient temperature and illumination intensity. It blocks IR light under strong illumination at 28 °C but is IR transparent under weak irradiation conditions or at a low temperature of 20 °C. The VO₂/TiN coatings exhibit a good integral visible transmittance of up to 51% and excellent IR switching efficiency of 48% at 2000 nm. These unique advantages make VO₂/TiN promising as smart energy‐saving windows.