Unconventional characteristics of magnetic toroidal multipoles have triggered researchers to study these unique resonant phenomena by using both 3D and planar resonators under intense radiation. Here, going beyond conventional planar unit cells, we report on the observation of magnetic toroidal modes using artificially engineered multimetallic planar plasmonic resonators. The proposed microstructures consist of iron (Fe) and titanium (Ti) components acting as magnetic resonators and torus, respectively. Our numerical studies and following experimental verifications show that the proposed structures allow for excitation of toroidal dipoles in the terahertz (THz) domain with the experimental Q-factor of ∼18. Taking the advantage of high-Q toroidal line shape and its dependence on the environmental perturbations, we demonstrate that room-temperature toroidal metasurface is a reliable platform for immunosensing applications. As a proof of concept, we utilized our plasmonic metasurface to detect Zika-virus (ZIKV) envelope protein (with diameter of 40 nm) using a specific ZIKV antibody. The sharp toroidal resonant modes of the surface functionalized structures shift as a function of the ZIKV envelope protein for small concentrations (∼pM). The results of sensing experiments reveal rapid, accurate, and quantitative detection of envelope proteins with the limit of detection of ∼24.2 pg/mL and sensitivity of 6.47 GHz/log(pg/mL). We envision that the proposed toroidal metasurface opens new avenues for developing low-cost, and efficient THz plasmonic sensors for infection and targeted bioagent detection.

Solid state gas sensors are a core enabling technology to a range of measurement applications including industrial, safety, and environmental monitoring. The technology associated with solid-state gas sensors has evolved in recent years with advances in materials, and improvements in processing and miniaturization. In this review, we examine the state-of-the-art of solid state gas sensors with the goal of understanding the core technology and approaches, various sensor design methods to provide targeted functionality, and future prospects in the field. The structure, detection mechanism, and sensing properties of several types of solid state gas sensors will be discussed. In particular, electrochemical cells (solid and liquid), impedance/resistance based sensors (metal oxide, polymer, and carbon based structures), and mechanical sensing structures (resonators, cantilevers, and acoustic wave devices) as well as sensor arrays and supporting technologies, are described. Development areas for this field includes increased control of material properties for improved sensor response and durability, increased integration and miniaturization, and new material systems, including nano-materials and nano-structures, to address shortcomings of existing solid state gas sensors.

Engineered terahertz (THz) plasmonic metamaterials have emerged as promising platforms for quick infection diagnosis, cost-effective and real-time pharmacology applications owing to their non-destructive and harmless interaction with biological tissues in both and assays. As a recent member of THz metamaterials family, toroidal metamaterials have been demonstrated to be supporting high-quality sharp resonance modes. Here we introduce a THz metasensor based on a plasmonic surface consisting of metamolecules that support ultra-narrow toroidal resonances excited by the incident radiation and demonstrate detection of an ultralow concertation targeted biomarker. The toroidal plasmonic metasurface was designed and optimized through extensive numerical studies and fabricated by standard microfabrication techniques. The surface then functionalized by immobilizing the antibody for virus-envelope proteins (ZIKV-EPs) for selective sensing. We sensed and quantified the ZIKV-EP in the assays by measuring the spectral shifts of the toroidal resonances while varying the concentration. In an improved protocol, we introduced gold nanoparticles (GNPs) decorated with the same antibodies onto the metamolecules and monitored the resonance shifts for the same concentrations. Our studies verified that the presence of GNPs enhances capturing of biomarker molecules in the surrounding medium of the metamaterial. By measuring the shift of the toroidal dipolar momentum (up to Δ~0.35 cm) for different concentrations of the biomarker proteins, we analyzed the sensitivity, repeatability, and limit of detection (LoD) of the proposed toroidal THz metasensor. The results show that up to 100-fold sensitivity enhancement can be obtained by utilizing plasmonic nanoparticles-integrated toroidal metamolecules in comparison to analogous devices. This approach allows for detection of low molecular-weight biomolecules (≈13 kDa) in diluted solutions using toroidal THz plasmonic unit cells.

This paper establishes the feasibility of a reusable biosensor that can be operated and stored at room temperature, for detection of small molecules in low resource settings. The sensor was fabricated using molecularly imprinted polymers (MIP) and cortisol was chosen as a model analyte. Cortisol imprinted polymer films were prepared by electropolymerizing pyrrole on an electrode surface in the presence of cortisol. Electrochemical over-oxidation of polypyrrole (PPy) was performed for the controlled release of cortisol templates and to create cortisol specific imprinting sites. Stepwise fabrication of imprinted sensors was characterized through cyclic voltammetry (CV) and scanning electron microscopy (SEM). The sensor exhibited a detection limit of 1 pM L−1 for cortisol. A unique feature of the sensor was that cross-reactivity with prednisolone (which has 100% interference in ELISA), was minimized to 18.3% compared to ELISA. The sensitivity of the sensor remained over 90% after 7 cycles of elution/rebinding, while the sensitivity decreased by 10% after 4 weeks of storage at room temperature, suggesting the sensor can be used multiple times and used with low overhead costs in low resource settings such as agricultural fields. The sensor was used for detection of cortisol in saliva samples of farm workers; benchmarking with ELISA showed excellent correlation. These findings indicate that such a sensor can be used for in-field measurements of small molecules (e.g. cortisol).

The downtime of industrial machines, engines, or heavy equipment can lead to a direct loss of revenue. Accurate prediction of such failures using sensor data can prevent or reduce the downtime. With the availability of Internet of Things (IoT) technologies, it is possible to acquire the sensor data in real-time. Machine Learning and Deep Learning (DL) algorithms can then be used to predict the part and equipment failures, given enough historical data. DL algorithms have shown significant advances in problems where progress has eluded the practitioners and researchers for several decades. This paper reviews the DL algorithms used for predictive maintenance and presents a case study of engine failure prediction. We also discuss the current use of sensors in the industry and future opportunities for electrochemical sensors in predictive maintenance.

Sensors fabricated on fabrics provide an elevated ease of use for wearable sensors. Such sensors will play a critical role in detecting the elevations in the concentrations of biochemical markers in human sweat. The ability of making such measurements is becoming an important tool for non-invasive and real-time health monitoring. We present a yarn-based flexible and superwettable electrochemical immunosensing strategy for highly selective and sensitive detection of cortisol in sweat. ZnO nanorods (ZnONRs)-coated flexible carbon yarns were prepared by using a hydrothermal method for immobilizing specific anti-cortisol antibodies and used as an immunosensing platform for detecting sweat cortisol levels. The morphology, elemental composition, crystallinity, and specific surface area were analyzed by using analytical techniques such as transmission electron microscopy (TEM), field emission scanning electron microscopy coupled energy-dispersive X-ray analysis (FE-SEM/EDS), X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The ZnONRs integrated carbon yarns showed excellent mechanical stability and superwettable properties. The immunosensor exhibited a wide linear detection range from 1 fg/mL to 1 μg/mL. The detection limits of the immunosensor were calculated to be between 0.45 and 0.098 fg/mL by using CV and DPV techniques, respectively. Additionally, cell viability studies were performed to investigate the biocompatibility and cytotoxicity of this carbon yarn ZnO sensing platform. The immunosensor was applied to measure the cortisol concentration in human sweat samples, and the outcomes were validated by using a chemiluminescent immunoassay system.

The detection of cortisol in saliva is an important screening tool for psychological stress and health monitoring, including the diagnosis of Cushing's syndrome, Addison's disease, and post-traumatic stress disorder (PTSD). In this work, a simple, low-cost, label-free, electrochemical immunosensing platform is explored for highly sensitive and selective detection of cortisol in saliva. Anti-Cortisol antibodies (Anti-C ab ) covalently immobilized on self-assembled monolayer (SAM) of dithiobis(succinimidylpropionte) (DTSP) modified microfabricated interdigitated microelectrodes (IDEs) were used for electrochemical detection of cortisol. The non-binding sites of immunosensor surface were blocked using ethyleneamine (EA). Electrochemical response studies as a function of cortisol concentrations were conducted using cyclic voltammetry (CV). The sensor exhibited a detection range from 10 pg/mL to 100 ng/mL, a detection limit of 10 pg/mL, and a sensitivity of 6 μA/(pg/mL) with the regression coefficient of 0.99. The obtained sensing parameters were in physiological range. The sensor was successfully tested on multiple specimen samples of saliva collected at different time intervals from two participants. The obtained cortisol concentrations from the developed electrochemical system correlate well with those were obtained using ELISA.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 199.212.65.7 Downloaded on 2014-11-04 to IP B3078Journal of The Electrochemical Society, 161 (2) B3077-B3082 (2014) ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 199.212.65.7 Downloaded on 2014-11-04 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 199.212.65.7 Downloaded on 2014-11-04 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 199.212.65.7 Downloaded on 2014-11-04 to IP

We have successfully developed a technique to electroplate thick CoNiMnP-based permanent magnet arrays with controlled direction of magnetization and improved magnetic properties by applying external magnetic fields during electroplating. The magnet arrays with individual magnet shapes and sizes were fabricated on a Si substrate using micromachining and electroplating techniques. The magnetic properties of these magnets have been characterized with the vibrating sample magnetometer. The optimized processing conditions with external magnetic fields during electroplating have improved the coercivity and the retentivity of the magnets by more than 200% and 350%, respectively, comparing with those without external magnetic fields. This paper describes the process for fabricating the magnets and the effect of external magnetic fields in controlling and improving the properties of the magnets. In addition to the capability of full scale integration, the high vertical anisotropy of thick magnet arrays can be used for many MEMS device applications.