Optical fiber sensors are the most promising technique in monitoring physical and chemical variables of civil structures. For the brittle material characteristics, a bare sensing fiber is prone to ...breakage under the shear or torsional action existed in the construction and operation. To guarantee the survival and long-term service of the sensors, the packaging measure is particularly significant. This treatment generates an intermedium layer between the sensing fiber and the monitored structure, which leads to the strain of the host material not entirely transferred to the sensing fiber for a portion of strain loss in the transferring path. To correct the error and improve the measurement accuracy, strain transfer theory is developed to establish the quantitative strain relationship between the sensing fiber and the host material. A state-of-the-art review on strain transfer theory of optical fiber based sensors developed for civil structures is addressed. It aims to demonstrate the advance, the application and the challenge of strain transfer theory and provide scientific guidance for the better understanding of the multi-layered sensing model and the theoretical instruction for the optimum design, calibration and measurement accuracy enhancement of optical fiber sensors.
•Strain transfer analysis of a three-layered mechanical model with embedded sensor is conducted for the error modification.•The perturbation of embedded sensor on strain field of host material is ...studied to instruct the protective layer design.•The interfacial shear stress along the bonded length are discussed and the interfacial debonding damaged is recognized.•The influence of sensitive parameters included in the interfacial shear stress function is discussed.•Suggestions are made on the design application of the embedded optical fiber sensor.
To realize the reliable and long-term strain detection, the durability of optical fiber sensors has attracted more and more attention. The packaging technique has been considered as an effective method, which can enhance the survival ratios of optical fiber sensors to resist the harsh construction and service environment in civil engineering. To monitor the internal strain of structures, the embedded installation is adopted. Due to the different material properties between host material and the protective layer, the monitored structure embedded with sensors can be regarded as a typical model containing inclusions. Interfacial characteristic between the sensor and host material exists obviously, and the contacted interface is prone to debonding failure induced by the large interfacial shear stress. To recognize the local interfacial debonding damage and extend the effective life cycle of the embedded sensor, strain transfer analysis of a general three-layered sensing model is conducted to investigate the failure mechanism. The perturbation of the embedded sensor on the local strain field of host material is discussed. Based on the theoretical analysis, the distribution of the interfacial shear stress along the sensing length is characterized and adopted for the diagnosis of local interfacial debonding, and the sensitive parameters influencing the interfacial shear stress are also investigated. The research in this paper explores the interfacial debonding failure mechanism of embedded sensors based on the strain transfer analysis and provides theoretical basis for enhancing the interfacial bonding properties and improving the durability of embedded optical fiber sensors.
•The construction strategies of BC-based functional nanomateirals were summarized.•The biosynthetic and chemical modification of BC can expand its application fields.•Different components can be ...incorporated in situ or ex situ for functionalizing BC.•We focus on the preparation method, mechanism and performance of functional BC.•The sensor, photocatalytic, magnetic and optoelectronic applications were reviewed.
Bacterial cellulose (BC) is a fascinating and renewable natural nanomaterial characterized by favorable properties such as remarkable mechanical properties, porosity, water absorbency, moldability, biodegradability and excellent biological affinity. Intensive research and exploration in the past few decades on BC nanomaterials mainly focused on their biosynthetic process to achieve the low-cost preparation and application in medical, food, advanced acoustic diaphragms, and other fields. These investigations have led to the emergence of more diverse potential applications exploiting the functionality of BC nanomaterials. This review gives a summary of construction strategies including biosynthetic modification, chemical modification, and different in situ and ex situ patterns of functionalization for the preparation of advanced BC-based functional nanomaterials. The major studies being directed toward elaborate designs of highly functionalized material systems for many-faceted prospective applications. Simple biosynthetic or chemical modification on BC surface can improve its compatibility with different matrix and expand its utilization in nano-related applications. Moreover, based on the construction strategies of functional nanomaterial system, different guest substrates including small molecules, inorganic nanoparticles or nanowires, and polymers can be incorporated onto the surfaces of BC nanofibers to prepare various functional nanocomposites with outstanding properties, or significantly improved physicochemical, catalytic, optoelectronic, as well as magnetic properties. We focus on the preparation methods, formation mechanisms, and unique performances of the different BC derivatives or BC-based nanocomposites. The special applications of the advanced BC-based functional nanomaterials, such as sensors, photocatalytic nanomaterials, optoelectronic devices, and magnetically responsive membranes are also critically and comprehensively reviewed.
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► Liquid water is forced through hydrophilic domains in Nafion by hydraulic permeation. ► Hydraulic permeation increases with hydrophilic volume fraction. ► Hydrophilic domains ...consist of hydrophilic channels ∼2.5
nm in diameter spaced 5.5
nm apart.
The flux of liquid water through Nafion membranes of different thickness and equivalent weight was measured as a function of hydrostatic pressure and temperature. Hydraulic water transport across Nafion membranes increases with temperature and equivalent weight of the Nafion. Hydraulic permeability increases with temperature due to both decreased water viscosity and increased hydrophilic volume fraction. Convective flow from the applied hydrostatic water pressure is an order of magnitude greater than the estimated diffusive water flux associated with the water activity gradient. Water sorption and hydraulic permeability data predict a hydrophilic pore network with hydrophilic domains 2.5
nm in diameter spaced 5.5
nm apart. The pore network structure from water sorption and hydraulic permeability are consistent with the spacing between hydrophilic domains observed with small angle X-ray scattering experiments.
We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water ...waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak.
The durability, robustness, and long-term stability of optical-fiber-based sensors applied to practical engineering have always been challenging problems. Refer to the sensors embedded in asphalt ...pavements, the situation becomes serious and feasible sensors with enhanced function are in high demand. Therefore, an improved design to configure the quasi-distributed and distributed optical fiber sensors and FBG-based point sensors for monitoring the three-dimensional information of multilayered asphalt pavements is needed. The in-field data declare that the transversal, longitudinal, and vertical deformations of the tested urban asphalt pavement are mainly affected by temperature. The M-shape strain profile induced by heavy vehicles can decrease to the regular state in approximately 30 min after unloading. The tested asphalt pavement presents good structural performance to bear the tensile strain and permanent deformation. The high survival ratio and the good robustness of the proposed sensors against the harsh construction and operation environment validate the feasibility and reliability for the long-term monitoring. Improved design proposals on the construction scheme of asphalt pavement are also addressed to control the strain of the established asphalt concrete course in relatively low level.
Recently developed chemical vapor deposition (CVD) is considered as an effective way to large‐area and high‐quality graphene preparation due to its ultra‐low cost, high controllability, and high ...scalability. However, CVD‐grown graphene film is polycrystalline, and composed of numerous grains separated by grain boundaries, which are detrimental to graphene‐based electronics. Intensive investigations have been inspired on the controlled growth of graphene single crystals with the absence of intrinsic defects. As the two most concerned parameters, the size and morphology serve critical roles in affecting properties and understanding the growth mechanism of graphene crystals. Therefore, a precise tuning of the size and morphology will be of great significance in scale‐up graphene production and wide applications. Here, recent advances in the synthesis of graphene single crystals on both metals and dielectric substrates by the CVD method are discussed. The review mainly covers the size and morphology engineering of graphene single crystals. Furthermore, recent progress in the growth mechanism and device applications of graphene single crystals are presented. Finally, the opportunities and challenges are discussed.
Recent advances in size and morphology engineering of graphene single crystals via chemical vapor deposition (CVD) are comprehensively reviewed. The growth mechanism and device applications are further presented. Studies of graphene engineering on various substrates by the CVD method pose a great potential in graphene‐based electronics and other applications.
Lithium (Li) metal battery is considered the most promising next‐generation battery due to its low potential and high theoretical capacity. However, Li dendrite growth causes serious safety problems. ...Herein, the 15‐Crown‐5 (15‐C‐5) is reported as an electrolyte additive based on solvation shell regulation. The strong complex effect between Li+ ion and 15‐C‐5 can reduce the concentration of Li ions on the electrode surface, thus changing the nucleation, and repressing the growth of Li dendrites in the plating process. Significantly, the strong coordination of Li+/15‐C‐5 would be able to make them aggregate around the Li crystal surface, which could form a protective layer and favor the formation of a smooth and dense solid electrolyte interphase with high toughness and Li+ ion conductivity. Therefore, the electrolyte system with 2.0 wt% 15‐C‐5 achieves excellent electrochemical performance with 170 cycles at 1.0 mA cm−2 with capacity of 0.5 mA h cm−2 in symmetric Li|Li cells. The obviously enhanced cycle and rate performance are also achieved in Li|LiNi0.6Co0.2Mn0.2O2 (NCM622) full cells. The 15‐C‐5 demonstrates to be a promising additive for the electrolytes toward safe and efficient Li metal batteries.
Owing to the strong coordination ability, 15‐Crown‐5 (15‐C‐5) ether can coordinate with Li+ to form a Li+/15‐C‐5 protective layer in Li surface and favor the formation of smooth and dense solid electrolyte interphase films with high Li+ conductivity. This is found to be effective to enable high‐performance electrolytes for Li metal batteries with a life span of 170 cycles.
Shape-morphing uses a single actuation source for complex-task-oriented multiple patterns generation, showing a more promising way than reconfiguration, especially for microrobots, where multiple ...actuators are typically hardly available. Environmental stimuli can induce additional causes of shape transformation to compensate the insufficient space for actuators and sensors, which enriches the shape-morphing and thereby enhances the function and intelligence as well. Here, making use of the ionic sensitivity of alginate hydrogel microstructures, we present a shape-morphing strategy for microrobotic end-effectors made from them to adapt to different physiochemical environments. Pre-programmed hydrogel crosslinks were embedded in different patterns within the alginate microstructures in an electric field using different electrode configurations. These microstructures were designed for accomplishing tasks such as targeting, releasing and sampling under the control of a magnetic field and environmental ionic stimuli. In addition to structural flexibility and environmental ion sensitivity, these end-effectors are also characterized by their complete biodegradability and versatile actuation modes. The latter includes global locomotion of the whole end-effector by self-trapping magnetic microspheres as a hitch-hiker and the local opening and closing of the jaws using encapsulated nanoparticles based on local ionic density or pH values. The versatility was demonstrated experimentally in both in vitro environments and ex vivo in a gastrointestinal tract. Global locomotion was programmable and the local opening and closing was achieved by changing the ionic density or pH values. This 'structural intelligence' will enable strategies for shape-morphing and functionalization, which have attracted growing interest for applications in minimally invasive medicine, soft robotics, and smart materials.
The novel conductive polyaniline/bacterial cellulose (PANI/BC) nanocomposite membranes have been synthesized in situ by oxidative polymerization of aniline with ammonium persulfate as an oxidant and ...BC as a template. The resulting PANI-coated BC nanofibrils formed a uniform and flexible membrane. It was found that the PANI nanoparticles deposited on the surface of BC connected to form a continuous nanosheath by taking along the BC template, which greatly increases the thermal stability of BC. The content of PANI and the electrical conductivity of composites increased with increasing reaction time from 30 to 90 min, while the conductivity decreased because of the aggregation of PANI particles by further prolonging the reaction time. In addition, the acids remarkably improve the accessibility and reactivity of the hydroxyl groups of BC. The results indicate that the composites exhibit excellent electrical conductivity (the highest value was 5.0 × 10(-2) S/cm) and good mechanical properties (Young's modulus was 5.6 GPa and tensile strength was 95.7 MPa). Moreover, the electrical conductivity of the membrane is sensitive to the strain. This work provides a straightforward method to prepare flexible films with high conductivity and good mechanical properties, which could be applied in sensors, flexible electrodes, and flexible displays. It also opens a new field of potential applications of BC materials.
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