Sensor Fault Diagnosis for Impedance Monitoring Using a Piezoelectric-Based Smart Interface Technique.

For a structural health monitoring (SHM) system, the operational functionality of sensors is critical for successful implementation of a damage identification process. This study presents experimental and analytical investigations on sensor fault diagnosis for impedance-based SHM using the piezoelectric interface technique. Firstly, the piezoelectric interface-based impedance monitoring is experimentally conducted on a steel bolted connection to investigate the effect of structural damage and sensor defect on electromechanical (EM) impedance responses. Based on the experimental analysis, sensor diagnostic approaches using EM impedance features are designed to distinguish the sensor defect from the structural damage. Next, a novel impedance model of the piezoelectric interface-driven system is proposed for the analytical investigation of sensor fault diagnosis. Various parameters are introduced into the EM impedance formulation to model the effect of shear-lag phenomenon, sensor breakage, sensor debonding, and structural damage. Finally, the proposed impedance model is used to analytically estimate the change in EM impedance responses induced by the structural damage and the sensor defect. The analytical results are found to be consistent with experimental observations, thus evidencing the feasibility of the novel impedance model for sensor diagnosis and structural integrity assessment. The study is expected to provide theoretical and experimental foundations for impedance monitoring practices, using the piezoelectric interface technique, with the existence of sensor faults.

Preload Monitoring in Bolted Connection Using Piezoelectric-Based Smart Interface.

In this study, a preload monitoring method using impedance signatures obtained from a piezoelectric-based smart interface is presented for bolted girder connections. Firstly, the background theory of the piezoelectric-based smart interface and its implementation into the health monitoring of bolted connections are outlined. A simplified electro-mechanical (EM) impedance model of a smart interface-embedded bolted connection system is formulated to interpret a mechanistic understanding of the EM impedance signatures under the effect of bolt preload. Secondly, finite element modeling of a bolted connection is carried out to show the numerical feasibility of the presented method, and to predetermine the sensitive frequency band of the impedance signatures. Finally, impedance measurements are conducted on a lab-scaled bolted girder connection, to verify the predetermined sensitive frequency range and to assess the bolt preload changes in the test structure.

Biomimetic approaches with smart interfaces for bone regeneration.

A 'smart tissue interface' is a host tissue-biomaterial interface capable of triggering favourable biochemical events inspired by stimuli responsive mechanisms. In other words, biomaterial surface is instrumental in dictating the interface functionality. This review aims to investigate the fundamental and favourable requirements of a 'smart tissue interface' that can positively influence the degree of healing and promote bone tissue regeneration. A biomaterial surface when interacts synergistically with the dynamic extracellular matrix, the healing process become accelerated through development of a smart interface. The interface functionality relies equally on bound functional groups and conjugated molecules belonging to the biomaterial and the biological milieu it interacts with. The essential conditions for such a special biomimetic environment are discussed. We highlight the impending prospects of smart interfaces and trying to relate the design approaches as well as critical factors that determine species-specific functionality with special reference to bone tissue regeneration.

Self-Decoupled Oxygen Electrocatalysis for Ultrastable Rechargeable Zn-Air Batteries with Mild-Acidic Electrolyte.

Rechargeable zinc-air batteries (ZABs) have been considered promising as next-generation sustainable energy storage devices; however, their large-scale deployment is hampered by the unsatisfactory cyclic lifespan. Employing neutral and mild-acidic electrolytes is effective in extending the cyclability, but the rapid performance degradation of the bifunctional catalysts owing to different microenvironmental requirements of the alternative oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is still a serious limitation of their cyclic life. Herein, we propose a "self-decoupling" strategy to significantly improve the stability of the bifunctional catalysts by constructing a smart interface in the bifunctional air electrode. This smart interface, containing a resistance-switchable sulfonic acid doped polyaniline nanoarray interlayer, is nonconductive at high potential but conductive at low potential, which enables spontaneous electrochemical decoupling of the bifunctional catalyst for the ORR and OER, respectively, and thus protects it from degradation. The resulting self-decoupled mild-acidic ZAB delivers stable cyclic performances in terms of a negligible energy efficiency loss of 0.015% cycle-1 and 3 times longer cycle life (∼1400 h) compared with the conventional mild-acidic ZAB using a normal bifunctional air electrode and the same low-cost ZnCo phosphide/nitrogen-doped carbon bifunctional catalyst. This work provides an effective strategy for tolerating alternative oxidation-reduction reactions and emphasizes the importance of smart nanostructure design for more sustainable batteries.

Colorimetric oligonucleotide-based sensor for ultra-low Hg2+ in contaminated environmental medium: Convenience, sensitivity and mechanism.

A colorimetric sensor for detection of Hg2+ is developed via graphene oxide/gold nanoparticles (GO/AuNPs) nanocomposite as peroxidase mimic. In the absence of Hg2+, the adsorption of ss-DNA on GO/AuNPs resulted in the decrease of peroxidase-like activity of GO/AuNPs, which catalyzed the oxidation of 3, 3, 5, 5-tetramethylbenzidine (TMB) to be very light blue. In the presence of Hg2+, the oligonucleotides of T-Hg2+-T conformation formed by thymine-Hg(II)-thymine interaction could not be adsorbed or bonded on GO/AuNPs, and the GO/AuNPs resumed their original high activity of peroxidase mimic and catalyzed the oxidation of TMB into distinct blue product. Under optimized conditions, the absorbance value at the wavelength of 655 nm (A655) was linearly related with the concentration of Hg2+ in the range between 5.2 × 10-9 M and 1.2 × 10-7 M with a detection limit of 3.8 × 10-10 M. By visual observation with the naked eye, Hg2+ as low as 3.3 × 10-7 M could cause color change in solution. The specific T-Hg2+-T binding made it easy to selectively detect Hg2+. The results show that the colorimetric assay offers great potential for the detection of Hg2+ in real samples.

On/Off-switchable zipper-like bioelectronics on a graphene interface.

An on/off-switchable graphene-based zipper-like interface is architectured for efficient bioelectrocatalysis. The graphene interface transduces a temperature input signal into structural changes of the membrane, resulting in the amplification of electrochemical signals and their transformation into the gated transport of molecules through the membrane.