Search

The design of optical sensors aims at providing, among other things, the highest precision in the determination of the target measurand. Many sensor systems rely on a spectral transducer to map changes in the measurand into spectral shifts of a resonance peak in the reflection or transmission spectrum, which is measured by a readout device (e.g., a spectrometer). For these spectral transducers, figures of merit have been defined which are based on specific assumptions on the readout and the data analysis. In reality, however, different transducers achieve optimal performance with different types of readout. Additionally, some transducers present a more complex spectral response for which existing figures of merit do not apply. In this paper, we investigate an approach to quantifying the potential performance of a given transducer for a more general class of readout methods. Starting from the Cramér–Rao lower bound, we define a new figure of merit, the integrated spectral sensitivity, which is directly related to the physical limit of precision and applicable to a wide variety of sensing systems. We apply this analysis to two different examples of transducers. The results bring useful insights into the design of optical sensors. [ABSTRACT FROM AUTHOR]

The present review article discusses the various sensors for biomarker detection available for multiple diseases with the scope of helping and encouraging researchers to design devices for the effective and early detection of diseases. In general, these sensors are classified into various types based on bio-recognition by detection systems or transducers. However, based on optical transducers, these are further divided into chromogenic, luminogenic, chemiluminescence, and optical fiber. Here in this article, attempts have been made for the analysis of various analytes or biomarkers of various diseases using different polymeric systems under the classification of optical chromogenic transducers. Optical detection of biomarkers in the sample solution is obtained via a biochemical reaction that causes changes in optical properties. Herein, results can be easily analyzed by a color change produced via ligand-analyte interaction, which can be measured to help in the diagnosis of various diseases. There are various types of renal biomarkers, which can be used as an indication of the functioning of the kidney like glucose (GL), uric acid (UA), urea, creatinine (CRN), and albumin (AL). GL is also an important biomarker for diabetes mellitus. For urinary tract infections (UTIs), nitrite is an important biomarker in urine samples. Bilirubin is used as a biomarker for liver damage. Increased chloride concentration in the sweat samples can be used as a biomarker for the disease cystic fibrosis. An elevated cholesterol level inside the body acts as a biomarker for cardiac arrest. Lactate appears to be a powerful predictor of sepsis. This review mainly deals with biochemical reactions for the detection of various biomarkers of diseases. Chemical aspects of the reactions are briefly discussed for their colorimetric evaluation to determine the biomarkers. This article also discusses various polymeric supports available for developing point-of-care testing (POCT) strips. • Sensors for the biomarker detection available for the various diseases. • Optical detection of biomarkers in sample solution is based on changes in optical properties. • Renal biomarkers of kidney are glucose (GL), uric acid (UA), urea, creatinine (CRN), and albumin (AL). • For urinary tract infections (UTIs), nitrite is an important biomarker in urine samples. • Various polymeric supports are available for developing point-of-care testing (POCT) strips. [ABSTRACT FROM AUTHOR]

• Nanostructured neural probes enable multimodal sensing and advanced imaging.. • Advanced probes integrate electrodes, sensors, and waveguides for precise analysis. • Decoding neural codes, brain mapping, and therapeutic advances hold great promise. • Addressing data integration and biocompatibility require multifaceted developments. Neuroprobes that use nanostructured photonic interfaces are capable of multimodal sensing, stimulation, and imaging with unprecedented spatio-temporal resolution. In addition to electrical recording, optogenetic modulation, high-resolution optical imaging, and molecular sensing, these advanced probes combine nanophotonic waveguides, optical transducers, nanostructured electrodes, and biochemical sensors. The potential of this technology lies in unraveling the mysteries of neural coding principles, mapping functional connectivity in complex brain circuits, and developing new therapeutic interventions for neurological disorders. Nevertheless, achieving the full potential of nanostructured photonic neural probes requires overcoming challenges such as ensuring long-term biocompatibility, integrating nanoscale components at high density, and developing robust data-analysis pipelines. In this review, we summarize and discuss the role of photonics in neural probes, trends in electrode diameter for neural interface technologies, nanophotonic technologies using nanostructured materials, advances in nanofabrication photonics interface engineering, and challenges and opportunities. Finally, interdisciplinary efforts are required to unlock the transformative potential of next-generation neuroscience therapies. [ABSTRACT FROM AUTHOR]

The most common methodology for performing multiple chemical and biological reactions in parallel is to use microtitre plates with either manual or robotic dispensing of reactants and wash solutions. We envision a paradigm shift where acoustically levitated droplets serve as wells of microtitre plates and are acoustically manipulated to perform chemical and biological reactions in a non-contact fashion. This in turn requires that lines of droplets can be levitated and manipulated simultaneously so that the same operations (merge, mix, and detect) can be performed on them in parallel. However, this has not been demonstrated until this work. Because of the nature of acoustic standing waves, a single focus has more than one trap, and can allow levitation of columns of droplets at the focal point and at half a wavelength above and below that point. Using this approach, we increased the number of acoustically levitated and merged droplets to 6 compared to 2 in the state-of-the-art. We showed that droplets in a column can be moved and merged with droplets in another column simultaneously and in a controlled manner to perform repeats and/or parallelisation of chemical and biological reactions. To demonstrate our approach experimentally, we built an acoustic levitator with top and bottom surfaces made of a 16 × 16 grid of 40 kHz phased array transducers and integrated optical detection system, studied two acoustic trap generation and movement algorithms, and performed an exemplar enzyme assay. This work has made significant steps towards acoustic levitation and manipulation of large numbers of droplets to eventually significantly reduce the use of the current state-of-the-art tools, microtitre plates and robots, for performing parallelised chemical and biological reactions. [ABSTRACT FROM AUTHOR]

Ammonia gas is a colorless gas that is known for its pungent odor. It is commonly used in various industries, such as agriculture, refrigeration, and chemical manufacturing. This paper provides a comprehensive overview of various technologies employed in ammonia gas sensors. The objective is to compare and identify the optimum method to detect ammonia gas. The review encompasses catalytic gas sensors, metal oxide gas sensors, polymer conductivity gas sensors, optical gas sensors, and indirect gas sensors, detailing their respective operational principles. Additionally, the advantages and disadvantages of each technology for ammonia gas detection are outlined. All these technologies have been used for many applications and some of them have been commercialized. Some sensor characteristics suggestions are also stated in order to develop an improved optical ammonia sensor for industrial applications. [ABSTRACT FROM AUTHOR]

Rapid, simultaneous detection of organic chemical pollutants in water is an important issue to solve for protecting human health. This study investigated the possibility of developing an in situ reusable optical sensor capable of selective measurements utilizing a chalcogenide transducer supplemented by a hydrophobic polymer membrane with detection based on evanescent waves in the mid-infrared spectrum. In order to optimise a polyisobutylene hydrophobic film deposited on a chalcogenide waveguide, a zinc selenide prism was utilized as a testbed for performing attenuated total reflection with Fourier-transform infrared spectroscopy. To comply with the levels mentioned in health guidelines, the target detection range in this study was kept rather low, with the concentration range extended from 50 ppb to 100 ppm to cover accidental pollution problems, while targeted hydrocarbons (benzene, toluene, and xylene) were still detected at a concentration of 100 ppb. Infrared measurements in the selected range showed a linear behaviour, with the exception of two constantly reproducible plateau phases around 25 and 80 ppm, which were observable for two polymer film thicknesses of 5 and 10 μm. The polymer was also found to be reusable by regenerating it with water between individual measurements by increasing the water temperature and flow to facilitate reverse exchange kinetics. Given the good conformability of the hydrophobic polymer when coated on chalcogenide photonic circuits and its demonstrated ability to detect organic pollutants in water and to be regenerated afterwards, a microfluidic channel utilising water flow over an evanescent wave optical transducer based on a chalcogenide waveguide and a polyisobutylene (PIB) hydrophobic layer deposited on its surface was successfully fabricated from polydimethylsiloxane by filling a mold prepared via CAD and 3D printing techniques. [ABSTRACT FROM AUTHOR]

One area of active research is the design and characterization of metal complexes synthesized with organic ligands for optoelectronic applications. Due to interaction between metal and organic ligands, metal complexes show distinct optical and electrical properties. The metal–ligand interactions exhibited by the complexes have the capability to modify the structure as well as properties of the complex. Metal complexes present in low-lying excited state are widely used as photosensitizers. Coordination complexes are utilized to create a wide range of inexpensive electronic and optoelectronic devices that generate, detect, and control light. The communication between optics and electronics is known as optoelectronics and involves the research, development, and fabrication of a hardware device that translates electrical energy into light and vice versa. Optoelectronic device is generally an electronic light using device. They are present in optical to electrical or electrical to optical transducers or instruments that utilize it during working. Numerous optoelectronic applications include telecommunications, military, automatic access control systems, and medical devices. This includes optoelectromagnetic actuator, different types of light-emitting diodes, gold as well as fluorescent nanomaterials, optical glasses, fibers, solar cell, laser, etc. The advanced developments of coordination compounds in luminescence, and photovoltaic and optoelectronic fields with applications are included. [ABSTRACT FROM AUTHOR]

This article reports the fine-tuning of the optical resonance wavelength (ORW) of surface-micromachined optical ultrasound transducer (SMOUT) arrays to enable ultrasound data readout with non-tunable interrogation light sources for photoacoustic computed tomography (PACT). Permanent ORW tuning is achieved by material deposition onto or subtraction from the top diaphragm of each element with sub-nanometer resolution. For demonstration, a SMOUT array is first fabricated, and its ORW is tuned for readout with an 808 nm laser diode (LD). Experiments are conducted to characterize the optical and acoustic performances of the elements within the center region of the SMOUT array. Two-dimensional and three-dimensional PACT (photoacoustic computed tomography) is also performed to evaluate the imaging performance of the ORW-tuned SMOUT array. The results show that the ORW tuning does not degrade the optical, acoustic, and overall imaging performances of the SMOUT elements. As a result, the fine-tuning method enables new SMOUT-based PACT systems that are low cost, compact, powerful, and even higher speed, with parallel readout capability. [ABSTRACT FROM AUTHOR]

We present an analysis of a three-layered structure used for both launching and detecting picosecond acoustic waves. To enhance the optical sensitivity to the acoustic disturbances, a cavity is designed, which acts as a Fabry–Perot interferometer. We use analytic modeling based on dual optical and acoustic transfer matrix formalism to analyze the coupled optical and acoustic wave propagation. Assuming a three-layer transducer made of an optical cavity sandwiched between two thin metallic layers, the model allows for mastering of the coupled optical and acoustic responses, which leads to an optimum design of the structure, and it highlights the various acoustic contributions to the reflectivity changes. The sensitivity of this three-layered structure to acoustic disturbances is compared to the numerical predictions we performed for the standard opto-acoustic transducer made of a single metallic layer. [ABSTRACT FROM AUTHOR]

Sensitivity and selectivity of modern electrochemical genotyping methods are insufficient to detect a single-oligonucleotide mismatch in low-concentration native DNA samples. Novel methods of tuning, controlling, and monitoring plasmon modes are necessary to achieve attomolar and higher sensitivity for the modern graphene-based transducers of molecular signals. The electrochemical DNA assay is promising one for applications in the molecular diagnostics of tumors with the genome single-nucleotide polymorphism (SNP) for simultaneously discriminating both wild-type and mutant alleles of the gene in very small concentrations. We offer the plasmon-associated DNA-genotyping method based on the screening effects in assemblies of Raman-optically active conjugates comprising DNA and metallic carbon nanotubes. The impedimetric DNA sensors of non-Faradaic type based on the plasmonic screening effect can be more sensitive than the Raman optical transducer based on Raman DNA optical activity resulting in the plasmon resonance due to liability of the Raman transducer parameters to environmental influence. [ABSTRACT FROM AUTHOR]

This work presents the development and design of aptasensor employing porous silicon (PSi) Fabry‒Pérot thin films that are suitable for use as optical transducers for the detection of lactoferrin (LF), which is a protein biomarker secreted at elevated levels during gastrointestinal (GI) inflammatory disorders such as inflammatory bowel disease and chronic pancreatitis. To overcome the primary limitation associated with PSi biosensors—namely, their relatively poor sensitivity due to issues related to complex mass transfer phenomena and reaction kinetics—we employed two strategic approaches: First, we sought to optimize the porous nanostructure with respect to factors including layer thickness, pore diameter, and capture probe density. Second, we leveraged convection properties by integrating the resulting biosensor into a 3D-printed microfluidic system that also had one of two different micromixer architectures (i.e., staggered herringbone micromixers or microimpellers) embedded. We demonstrated that tailoring the PSi aptasensor significantly improved its performance, achieving a limit of detection (LOD) of 50 nM—which is >1 order of magnitude lower than that achieved using previously-developed biosensors of this type. Moreover, integration into microfluidic systems that incorporated passive and active micromixers further enhanced the aptasensor's sensitivity, achieving an additional reduction in the LOD by yet another order of magnitude. These advancements demonstrate the potential of combining PSi-based optical transducers with microfluidic technology to create sensitive label-free biosensing platforms for the detection of GI inflammatory biomarkers. [ABSTRACT FROM AUTHOR]

This treatise studies a microoptoelectromechanical accelerometer (MOEMA) with an optical measuring transducer built according to the optical tunneling principle (evanescent coupling). The work discusses the design of the accelerometer's microelectromechanical sensing element (MSE) and states the requirements for the design to achieve a sensitivity threshold of 1 µg m/s2 at a calculated eigenvalue of the MSE. The studies cover the selection of the dimensions, mass, eigenfrequency and corresponding stiffness of the spring suspension, gravity-induced cross-displacements. The authors propose and experimentally test an optical transducer positioning system represented by a capacitive actuator. This approach allows avoiding the restrictions in the fabrication of the transducer conditioned by the extremely high aspect ratio of deep silicon etching (more than 100). The designed MOEMA is tested on three manufactured prototypes. The experiments show that the sensitivity threshold of the accelerometers is 2 µg. For the dynamic range from minus 0.01 g to plus 0.01 g, the average nonlinearity of the accelerometers' characteristics ranges from 0.7% to 1.62%. For the maximum dynamic range from minus 0.015 g to plus 0.05 g, the nonlinearity ranges from 2.34% to 2.9%, having the maximum deviation at the edges of the regions. The power gain of the three prototypes of accelerometers varies from 12.321 mW/g to 26.472 mW/g. The results provide broad prospects for the application of the proposed solutions in integrated inertial devices. [ABSTRACT FROM AUTHOR]

External-cavity diode laser (ECDL) can continuously change the output wavelength by scanning its optical resonance cavity (ORC), which is a piezoelectric transducer (PZT) actuated mechanical system. However, because of the inherent hysteresis characteristic of PZT and limited system bandwidth, the dynamic response of the ORC system exhibits both the nonlinearity and vibration while high-frequency triangular wave scanning, thereby resulting in the degradation of the output wavelength performance of the ECDL. As a result, a trajectory optimization method is presented to improve the scanning characteristics of the ORC system. Firstly, the hysteresis behavior of PZT is described by the elliptic model to generate a compensation voltage for the PZT. Secondly, the cusp region of the compensation voltage is optimized by a frequency domain objective function to greatly reduce the high-order harmonic components of the compensation voltage. Finally, an optimal voltage trajectory for driving the ORC system is obtained. The experimental results demonstrate the validity of our proposed trajectory optimization method for simultaneously suppressing the nonlinearity and vibration of the ORC system within the scanning frequency of 100 Hz. • A trajectory optimization method is designed based on an ellipse model and spectrum shaping. • The method can improve the scanning characteristics of the ORC system. • A frequency domain objective function is developed to minimize the ORC system vibration. [ABSTRACT FROM AUTHOR]

Staphylococcal enterotoxins (SEs), the major virulence factors of Staphylococcus aureus, cause a wide range of food poisoning and seriously threaten human health by infiltrating the food supply chain at different phases of manufacture, processes, distribution, and market. The significant prevalence of Staphylococcus aureus calls for efficient, fast, and sensitive methods for the early detection of SEs. Here, we provide a comprehensive review of the hazards of SEs in contaminated food, the characteristic and worldwide regulations of SEs, and various detection methods for SEs with extensive comparison and discussion of benefits and drawbacks, mainly including biological detection, genetic detection, and mass spectrometry detection and biosensors. We highlight the biosensors for the screening purpose of SEs, which are classified according to different recognition elements such as antibodies, aptamers, molecularly imprinted polymers, T-cell receptors, and transducers such as optical, electrochemical, and piezoelectric biosensors. We analyzed challenges of biosensors for the monitoring of SEs and conclude the trends for the development of novel biosensors should pay attention to improve samples pretreatment efficiency, employ innovative nanomaterials, and develop portable instruments. This review provides new information and insightful commentary, important to the development and innovation of further detection methods for SEs in food samples. [ABSTRACT FROM AUTHOR]

The overuse and abuse of antibiotics have led to increased pollution in water environments. Thus, it is crucial to develop a rapid, high-frequency, and cost-effective method for on-site detection of antibiotics. In this regard, a reusable fiber-embedded microfluidic chip was constructed by combining a microfluidic chip with a functionalized fiber bioprobe that served as both a biorecognition element and an optical transducer. The fiber-embedded microfluidic chip enabled the quantitative detection of kanamycin (KANA) by integrating a portable all-fiber evanescent wave fluorescence detection device. Under optimized conditions, quantitative KANA detection was achieved with a detection limit of 0.03 μg L−1 and a linear detection range of 0.21–10.3 μg L−1. The accurate detection of KANA in various water samples can be completed within 25 min without pretreatment. The functionalized fiber-embedded microfluidic chip could be reused more than 200 times without significant performance loss. To demonstrate its suitability for practical applications, the fiber-embedded microfluidic chip was used to investigate KANA residues in surface waters obtained from the Qinghe River in Beijing, China. The results were compared with those of a traditional enzyme-linked immunosorbent assay, which showed a high correlation. Compared to conventional optical microfluidic chips, the proposed fiber-embedded microfluidic chip has several advantages, including its ease of use, miniaturization, cost-effectiveness, reusability, and high flexibility. It is an ideal alternative for rapid, sensitive on-site detection of antibiotics and other trace substances in environmental, food, and medical fields. [ABSTRACT FROM AUTHOR]

The discovery of noble metal plasmonic nanoparticles (PNPs) has introduced surface-enhanced Raman scattering (SERS) as a highly sensitive and specific bioanalytical technique with greater potential in point-of-need disease diagnosis. This Tutorial provides an overview of the principles governing a gold PNP-based biosensor design for sensitive and reliable SERS-based detection of disease biomarkers. First, we will highlight the optical transducer properties of PNPs, the principles of SERS, the benefits of SERS detection, and the modes of SERS for biomarker detection. The analytical performance (sensitivity and specificity) and the reliability (accuracy and reproducibility) of a SERS biosensor are mainly dictated by (i) the chemical and optical transducer properties of PNPs, (ii) the functional nano interface, where the interaction(s) between PNPs and target biomolecules take place, and (iii) SERS data acquisition and evaluation metrics. Maintaining a balance between SERS signal enhancement and reproducibility is critical for advancing the field deployment of SERS technologies. However, the reproducibility of SERS biosensors is often overlooked in lieu of the assay sensitivity. Consequently, next, we will discuss the systematic optimization strategies for fabricating gold PNPs as SERS substrates and designing their functional interface to design SERS biosensors with sufficient sensitivity, specificity, and reproducibility. We will highlight the choice of PNPs and their integration into biosensing platforms depending on the mode of SERS detection. Last, we will discuss the SERS data acquisition and performance evaluation as an integral part of the SERS biosensors development workflow. [ABSTRACT FROM AUTHOR]

This work presents the development of a new photothermal radiometry (PTR) setup using a mix between frequency and spatial domain scans, along with a three-dimensional (3D) heat diffusion model. This newly developed PTR system, with a spatial resolution of 33 μm, is used to measure thermophysical properties of several kinds of materials. These properties include the thermal diffusivity, a, of homogeneous semi-infinite materials, thermal boundary resistance, R t h , and thermal anisotropy of membranes. The measured properties for homogeneous semi-infinite materials and two-layered systems are in good agreement with the literature values. In addition, it was possible to obtain an anisotropic factor of 24.6 between the in-plane and cross-plane thermal diffusivity of a 25 μm anisotropic flexible graphite sheet. Furthermore, it was also possible to measure, both directly and independently, the anisotropic thermal diffusivities for a 1 μm titanium membrane. It is suggested that this new hybrid technique can help us to fill the gap between conventional PTR and other photothermal and thermoreflectance techniques. Using this PTR setup, it is possible to experimentally measure isotropic and anisotropic thermophysical properties of bulk and thin materials, including membranes, with high precision through accurate characterization of the pump beam spots size. This is accomplished without the need for an optical transducer layer. [ABSTRACT FROM AUTHOR]

The field of biosensor development is fueled by innovations in new functional transduction materials and technologies. Material innovations promise to extend current sensor hardware limitations, reduce analysis costs, and ensure broad application of sensor methods. Optical sensors are particularly attractive because they enable sensitive and noninvasive analyte detection in near real-time. Optical transducers convert physical, chemical, or biological events into detectable changes in fluorescence, refractive index, or spectroscopic shifts. Thus, in addition to sophisticated biochemical selector designs, smart transducers can improve signal transmission and amplification, thereby greatly facilitating the practical applicability of biosensors, which, to date, is often hampered by complications such as difficult replication of reproducible selector-analyte interactions within a uniform and consistent sensing area. In this context, stimuli-responsive and optically active Janus emulsions, which are dispersions of kinetically stabilized biphasic fluid droplets, have emerged as a novel triggerable material platform that provides as a versatile and cost-effective alternative for the generation of reproducible, highly sensitive, and modular optical sensing layers. The intrinsic and unprecedented chemical-morphological-optical coupling inside Janus droplets has facilitated optical signal transduction and amplification in various chemo- and biosensor paradigms, which include examples for the rapid and cost-effective detection of major foodborne pathogens. These initial demonstrations resulted in detection limits that rival the capabilities of current commercial platforms. This trend article aims to present a conceptual summary of these initial efforts and to provide a concise and comprehensive overview of the pivotal kinetic and thermodynamic principles that govern the ability of Janus droplets to sensitively and selectively respond to and interact with bacteria. [ABSTRACT FROM AUTHOR]

Photoacoustic microscopy (PAM), due to its deep penetration depth and high contrast, is playing an increasingly important role in biomedical imaging. PAM imaging systems equipped with conventional ultrasound transducers have demonstrated excellent imaging performance. However, these opaque ultrasonic transducers bring some constraints to the further development and application of PAM, such as complex optical path, bulky size, and difficult to integrate with other modalities. To overcome these problems, ultrasonic transducers with high optical transparency have appeared. At present, transparent ultrasonic transducers are divided into optical-based and acoustic-based sensors. In this paper, we mainly describe the acoustic-based piezoelectric transparent transducers in detail, of which the research advances in PAM applications are reviewed. In addition, the potential challenges and developments of transparent transducers in PAM are also demonstrated. [ABSTRACT FROM AUTHOR]

Lightning strikes are the main cause of transmission line faults, and the accurate lightning current number is an important basis to guide scientific lightning protection. The use of sensors with excellent sensing performance to carry out lightning current monitoring on transmission lines is beneficial to the accumulation of key parameters of original lightning strikes, so it is necessary to study the lightning current measurement structure of transmission lines. In this paper, an optical current-sensing unit is used to monitor the lightning current on transmission lines. A measuring structure that can monitor key parameters of the lightning current under different types of lightning strikes is proposed. First, establish the lightning current return channel model and the equivalent model of the tower, study the influence of the transmission tower on the current in the lightning channel, and analyze the direct measurement position of the lightning current on the tower; establish the multi-wave impedance model of the tower, and build a multi-base tower. The simulation model of the transmission system analyzes the transmission characteristics of the lightning current on the transmission line and the lightning protection line in the case of different types of faults; from the perspective of the measurement of key parameters of the lightning current, the lightning current measurement structure of the transmission system is constructed to analyze different lightning strikes. The measurement effect of each monitoring position in the case of a lightning strike and the waveform characteristics of the fault current in the case of insulator flashover are analyzed. [ABSTRACT FROM AUTHOR]

Electrochemical and optical platforms are commonly employed in designing biosensors. However, one signal readout can easily lead to inaccuracies due to the effect of nonstandard test procedures, different operators, and experimental environments. We have developed a dual-signal protocol that combined two transducer principles in one aptamer-based biosensor by simultaneously performing electrochemical- and extraordinary optical transmission (EOT)-based plasmonic detection using gold nanopit arrays (AuNpA). Compared with full hole structures, we found that nanopits, that did not fully penetrate the gold film, not only exhibited a better plasmonic bandwidth and refractive index sensitivity both in the finite-difference time-domain simulation and in experiments by shielding the gold/quartz mode but also enlarged the electrochemical active surface area. Therefore, the periodic non-fully penetrating AuNpA were modified with ferrocene-labeled human serum albumin aptamer receptors. The formation of the receptor layer and human serum albumin binding complex induced a conformational change, which resulted in variation in the electron transfer between the electro-active ferrocene units and the AuNpA surface. Simultaneously, the binding event caused a surface plasmon polaritons wavelength shift corresponding to a change in the surface refractive index. Interestingly, although both transducers recorded the same binding process, they led to different limits of detection, dynamic ranges, and sensitivities. The electrochemical transducer showed a dynamic detection range from 1 nM to 600 μ M, while the optical transducer covered high concentrations from 100 μ M to 600 μ M. This study not only provides new insights into the design of plasmonic nanostructures but also potentially opens an exciting avenue for dual-signal disease diagnosis and point-of-care testing applications. [ABSTRACT FROM AUTHOR]

The versatility of metal complexes of corroles has raised interest in the use of these molecules as elements of chemical sensors. The tuning of the macrocycle properties via synthetic modification of the different components of the corrole ring, such as functional groups, the molecular skeleton, and coordinated metal, allows for the creation of a vast library of corrole-based sensors. However, the scarce conductivity of most of the aggregates of corroles limits the development of simple conductometric sensors and requires the use of optical or mass transducers that are rather more cumbersome and less prone to be integrated into microelectronics systems. To compensate for the scarce conductivity, corroles are often used to functionalize the surface of conductive materials such as graphene oxide, carbon nanotubes, or conductive polymers. Alternatively, they can be incorporated into heterojunction devices where they are interfaced with a conductive material such as a phthalocyanine. Herewith, we introduce two heterostructure sensors combining lutetium bisphthalocyanine (LuPc2) with either 5,10,15-tris(pentafluorophenyl) corrolato Cu (1) or 5,10,15-tris(4-methoxyphenyl)corrolato Cu (2). The optical spectra show that after deposition, corroles maintain their original structure. The conductivity of the devices reveals an energy barrier for interfacial charge transport for 1/LuPc2, which is a heterojunction device. On the contrary, only ohmic contacts are observed in the 2/LuPc2 device. These different electrical properties, which result from the different electron-withdrawing or -donating substituents on corrole rings, are also manifested by the opposite response with respect to ammonia (NH3), with 1/LuPc2 behaving as an n-type conductor and 2/LuPC2 behaving as a p-type conductor. Both devices are capable of detecting NH3 down to 10 ppm at room temperature. Furthermore, the sensors show high sensitivity with respect to relative humidity (RH) but with a reversible and fast response in the range of 30–60% RH. [ABSTRACT FROM AUTHOR]

This study discusses the problem of reducing the influence of external destabilizing factors on microelectromechanical angular velocity transducers. It reveals that for measurements of small angular velocities of the order of a few to tens of microradians per second, micro optoelectromechanical transducers that contain optical readout units are preferable to use. The effect of linear acceleration on the characteristics of a frame micro optoelectromechanical angular velocity transducer with two optical readout channels is analyzed. We consider two methods of angular velocity measurement error compensation when the frame micro optoelectromechanical transducer is under the influence of linear acceleration. The two compensation methods implement amplification factor control and force feedback, respectively. The readout unit, based on the optical tunnel effect and used for precision measurement of the amplitude of oscillations of the sensing element, is experimentally investigated; a function of converting the amplitude of oscillations of the sensing element into voltage is obtained. The possibility of forming transducer output signals, which are proportional to angular velocity and linear acceleration, is presented. The dependences of changes in the amplification factor on the zero off set voltage, proportional to the acting linear acceleration, are presented for different ranges of angular velocities. A system, consisting of a low-pass filter (LPF), a proportionalintegral regulator, and an additional pair of comb-type electrostatic actuators, is proposed for compensating the force effect of a destabilizing linear acceleration. Additional actuators are arranged perpendicular to the actuators that excite the primary oscillations. The measurement error of angular velocity when using the two methods of compensation, respectively, has been estimated. The proposed technical solutions enable to increase the accuracy of angular velocity measurements by micro optoelectromechanical transducers used in navigation and orientation systems of unmanned aircrafts of various types. [ABSTRACT FROM AUTHOR]

Label-free sensing is a promising approach for point-of-care testing devices. Among optical transducers, photonic crystal slabs (PCSs) have positioned themselves as an inexpensive yet versatile platform for label-free biosensing. A spectral resonance shift is observed upon biomolecular binding to the functionalized surface. Commonly, a PCS is read out by a spectrometer. Alternatively, the spectral shift may be translated into an intensity change by tailoring the system response. Intensity-based camera setups (IBCS) are of interest as they mitigate the need for postprocessing, enable spatial sampling, and have moderate hardware requirements. However, they exhibit modest performance compared with spectrometric approaches. Here, we show an increase of the sensitivity and limit of detection (LOD) of an IBCS by employing a sharp-edged cut-off filter to optimize the system response. We report an increase of the LOD from (7.1 ± 1.3) × 10−4 RIU to (3.2 ± 0.7) × 10−5 RIU. We discuss the influence of the region of interest (ROI) size on the achievable LOD. We fabricated a biochip by combining a microfluidic and a PCS and demonstrated autonomous transport. We analyzed the performance via refractive index steps and the biosensing ability via diluted glutathione S-transferase (GST) antibodies (1:250). In addition, we illustrate the speed of detection and demonstrate the advantage of the additional spatial information by detecting streptavidin (2.9 µg/mL). Finally, we present the detection of immunoglobulin G (IgG) from whole blood as a possible basis for point-of-care devices. [ABSTRACT FROM AUTHOR]

Organ-on-a-Chip systems are emerging as an important in vitro analysis method for drug screening and medical research. For continuous biomolecular monitoring of the cell culture response, label-free detection within the microfluidic system or in the drainage tube is promising. We study photonic crystal slabs integrated with a microfluidic chip as an optical transducer for label-free biomarker detection with a non-contact readout of binding kinetics. This work analyzes the capability of same-channel reference for protein binding measurements by using a spectrometer and 1D spatially resolved data evaluation with a spatial resolution of 1.2 μ m. A cross-correlation-based data-analysis procedure is implemented. First, an ethanol–water dilution series is used to obtain the limit of detection (LOD). The median of all row LODs is (2.3 ± 0.4) × 10 − 4 RIU with 10 s exposure time per image and (1.3 ± 0.24) × 10 − 4 RIU with 30 s exposure time. Next, we used a streptavidin–biotin binding process as a test system for binding kinetics. Time series of optical spectra were recorded while constantly injecting streptavidin in DPBS at concentrations of 1.6 nM, 3.3 nM, 16.6 nM and 33.3 nM into one channel half as well as the whole channel. The results show that localized binding within a microfluidic channel is achieved under laminar flow. Furthermore, binding kinetics are fading out at the microfluidic channel edge due to the velocity profile. [ABSTRACT FROM AUTHOR]

The present work describes an alternative method for detecting and identifying Listeria monocytogenes in food samples by developing a nanophotonic biosensor containing bioreceptors and optical transducers. The development of photonic sensors for the detection of pathogens in the food industry involves the implementation of procedures for selecting probes against the antigens of interest and the functionalization of the sensor surfaces on which the said bioreceptors are located. As a previous step to functionalizing the biosensor, an immobilization control of these antibodies on silicon nitride surfaces was carried out to check the effectiveness of in plane immobilization. On the one hand, it was observed that a Listeria monocytogenes-specific polyclonal antibody has a greater binding capacity to the antigen at a wide range of concentrations. A Listeria monocytogenes monoclonal antibody is more specific and has a greater binding capacity only at low concentrations. An assay for evaluating selected antibodies against particular antigens of Listeria monocytogenes bacteria was designed to determine the binding specificity of each probe using the indirect ELISA detection technique. In addition, a validation method was established against the reference method for many replicates belonging to different batches of meat-detectable samples, with a medium and pre-enrichment time that allowed optimal recovery of the target microorganism. Moreover, no cross-reactivity with other nontarget bacteria was observed. Thus, this system is a simple, highly sensitive, and accurate platform for L. monocytogenes detection. [ABSTRACT FROM AUTHOR]

The article "Beginner and Advanced Pianists' Eye Focus on Piano Instructional Videos: A Pilot Investigation" published in the MTNA e-Journal in September 2024 explores the impact of visual components in online piano tutorial videos on beginner and advanced pianists. The study utilized eye-tracking technology to analyze participants' eye focus and attention while watching instructional videos on YouTube. Results indicated that advanced pianists showed higher fixation numbers and time during video viewing, with the overhead view with score being rated as the most effective visual component. The study highlights the importance of visual content in digital video tutorials for piano learners of different skill levels. [Extracted from the article]

Microbial pathogens have threatened the world due to their pathogenicity and ability to spread in communities. The conventional laboratory‐based diagnostics of microbes such as bacteria and viruses need bulky expensive experimental instruments and skilled personnel which limits their usage in resource‐limited settings. The biosensors‐based point‐of‐care (POC) diagnostics have shown huge potential to detect microbial pathogens in a faster, cost‐effective, and user‐friendly manner. The use of various transducers such as electrochemical and optical along with microfluidic integrated biosensors further enhances the sensitivity and selectivity of detection. Additionally, microfluidic‐based biosensors offer the advantages of multiplexed detection of analyte and the ability to deal with nanoliters volume of fluid in an integrated portable platform. In the present review, we discussed the design and fabrication of POCT devices for the detection of microbial pathogens which include bacteria, viruses, fungi, and parasites. The electrochemical techniques and current advances in this field in terms of integrated electrochemical platforms that include mainly microfluidic‐ based approaches and smartphone and Internet‐of‐things (IoT) and Internet‐of‐Medical‐Things (IoMT) integrated systems have been highlighted. Further, the availability of commercial biosensors for the detection of microbial pathogens will be briefed. In the end, the challenges while fabrication of POC biosensors and expected future advances in the field of biosensing have been discussed. The integrated biosensor‐based platforms with the IoT/IoMT usually collect the data to track the community spread of infectious diseases which would be beneficial in terms of better preparedness for current and futuristic pandemics and is expected to prevent social and economic losses. [ABSTRACT FROM AUTHOR]

Micro-opto-electro-mechanical (MOEM) accelerometers that can measure small accelerations are attracting growing attention thanks to their considerable advantages—such as high sensitivity and immunity to electromagnetic noise—over their rivals. In this treatise, we analyze 12 schemes of MOEM-accelerometers, which include a spring mass and a tunneling-effect-based optical sensing system containing an optical directional coupler consisting of a fixed and a movable waveguide separated by an air gap. The movable waveguide can perform linear and angular movement. In addition, the waveguides can lie in single or different planes. Under acceleration, the schemes feature the following changes to the optical system: gap, coupling length, overlapping area between the movable and fixed waveguides. The schemes with altering coupling lengths feature the lowest sensitivity, yet possess a virtually unlimited dynamic range, which makes them comparable to capacitive transducers. The sensitivity of the scheme depends on the coupling length and amounts to 11.25 × 103 m−1 for a coupling length of 44 μm and 30 × 103 m−1 for a coupling length of 15 μm. The schemes with changing overlapping areas possess moderate sensitivity (1.25 × 106 m−1). The highest sensitivity (above 6.25 × 106 m−1) belongs to the schemes with an altering gap between the waveguides. [ABSTRACT FROM AUTHOR]

During stressful conditions, the human body synthesizes catecholamine neurotransmitters such as dopamine and adrenaline, and cortisol. The monitoring of these three molecules levels is crucial for stress management and holds significant medical applications. Here we developed an analytical device that incorporates a biomimetic (tongue-mimic) associated with an optical physico-chemical transducer, able to detect simultaneously cortisol, dopamine and adrenaline in human saliva without pre-treatments, using an array sensor based on fluorescent chemical receptors (BODIPY, Rhodamine, and Naphthylamides) able to interact by non-covalent interaction with cortisol, adrenaline and dopamine, leading to a change of the emission. Calibration, recovery and selectivity have been performed to validate the device. In particular, the linear responses of the array to concentration range of 1 pM–1 mM of the three analytes were demonstrated by PLS analysis, as well as the high selectivity by PLS-DA analysis performed with artificial saliva samples. Analyses in real human saliva samples, compared to the validated analytical methods, demonstrated that our prototype represents the first point-of-care device able to quantify these three analytes in human saliva with one single analysis in a wider concentration range respect to the other standard methods. [Display omitted] [ABSTRACT FROM AUTHOR]

Each year, millions of people suffer from foodborne illness due to the consumption of food contaminated with pathogenic bacteria, which severely challenges global health. Therefore, it is essential to recognize foodborne pathogens swiftly and correctly. However, conventional detection techniques for bacterial pathogens are labor-intensive, low selectivity, and time-consuming, highlighting a notable knowledge gap. A novel approach, aptamer-based biosensors (aptasensors) linked to carbon nanomaterials (CNs), has shown the potential to overcome these limitations and provide a more reliable method for detecting bacterial pathogens. Aptamers, short single-stranded DNA (ssDNA)/RNA molecules, serve as bio-recognition elements (BRE) due to their exceptionally high affinity and specificity in identifying foodborne pathogens such as Salmonella spp., Escherichia coli (E. coli), Listeria monocytogenes , Campylobacter jejuni , and other relevant pathogens commonly associated with foodborne illnesses. Carbon nanomaterials' high surface area-to-volume ratio contributes unique characteristics crucial for bacterial sensing, as it improves the binding capacity and signal amplification in the design of aptasensors. Furthermore, aptamers can bind to CNs and create aptasensors with improved signal specificity and sensitivity. Hence, this review intends to critically review the current literature on developing aptamer functionalized CN-based biosensors by transducer optical and electrochemical for detecting foodborne pathogens and explore the advantages and challenges associated with these biosensors. Aptasensors conjugated with CNs offers an efficient tool for identifying foodborne pathogenic bacteria that is both precise and sensitive to potentially replacing complex current techniques that are time-consuming. [Display omitted] • Aptamer-carbon nanomaterial biosensors offer reliable pathogen detection in food safety. • Aptamers exhibit high specificity and sensitivity in identifying pathogens. • Aptamer incorporated carbon nanomaterials show promises in diverse applications especially in pathogen detection. • Addressing stability and sensitivity issues crucial for biosensor advancement. [ABSTRACT FROM AUTHOR]

Plasmonic nanostructures with tunable optical properties can have many different applications, including high-sensitivity optical sensing for biological and chemical analyses in different field such as medical, environmental and food safety. The realization of an optimized sensing platform is closely related to the ability to finely control optical properties of nanostructures, which are, in turn, intimately linked to their geometrical and compositional characteristics. In this paper, an efficient and reproducible fabrication protocol, based on nanosphere lithography, for the realization of metal nanostructures with tunable plasmonic features is presented. In particular, the relationships between the geometric characteristics of different types of nanostructures with related optical phenomena such as enhanced absorption or extraordinary transmission are investigated in detail. These properties, together with electric field enhancement and confinement, are characterized and optimized in view of the employment of the fabricated nanostructures as optical transducers in nanoplasmonic chemosensor platforms working in the UV-VIS spectral range. [ABSTRACT FROM AUTHOR]

This paper focuses on creating one-dimensional diffractive grooved structures of antigen proteins on glass substrates for the label-free detection of antibodies to dairy allergens. In particular, the fabrication of protein structures is carried out by combining microcontact printing with physisorption, imines coupling, and thiol-ene click chemistry. The work first sets up these patterning methods and discusses and compares the main aspects involved in them (structure, biolayer thickness, functionality, stability). Homogeneous periodic submicron structures of proteins are created and characterized by diffractive measurements, AFM, FESEM, and fluorescence scanning. Then, this patterning method is applied to proteins involved in cow milk allergy, and the resulting structures are implemented as optical transducers to sense specific immunoglobulins G. In particular, gratings of bovine serum albumin, casein, and β-lactoglobulin are created and assessed, reaching limits of detection in the range of 30–45 ng·mL−1 of unlabeled antibodies by diffractive biosensing. [ABSTRACT FROM AUTHOR]

The periodontal ligament (PDL) provides support, proprioception, nutrition, and protection within the tooth–PDL–bone complex (TPBC). While understanding the mechanical behavior of the PDL is critical, current research has inferred PDL mechanics from finite element models, from experimental measures on complete TPBCs, or through direct measurement of isolated PDL sections. Here, transducers are used in an attempt to quantify ex vivo PDL strain. In-fiber Bragg grating (FBG) sensors are small flexible sensors that can be placed within an intact TPBC and yield repeatable strain measurements from within the PDL space. The objective of this study was to determine: 1) if the FBG strain measured from the PDL space of intact swine premolars ex vivo was equivalent to physical PDL strains estimated through finite element analysis and 2) if a change in FBG strain could be linearly related to a change in finite element strain under variable tooth displacement, applied to an intact swine TPBC. Experimentally, individual TPBCs were subjected to 2 displacements (n = 14). The location of the FBG was determined from representative micro–computed tomography images. From a linear elastic finite element model of a TPBC, the strain magnitudes at the sensor locations were recorded. An experimental ratio (i.e., FBG strain at the first displacement divided by the FBG strain at the second displacement) and a finite element ratio (i.e., finite element strain at the first displacement divided by the finite element strain at the second displacement) were calculated. A linear regression model indicated a statistically significant relationship between the experimental and finite element ratio (P = 0.017) with a correlation coefficient (R 2) of 0.448. It was concluded that the FBG sensor could be used as a measure for a change in strain and thus could be implemented in applications where the mechanical properties of an intact PDL are monitored over time. [ABSTRACT FROM AUTHOR]

Plasmonic nanoantennas have earned outstanding credits for their powerful ability to couple light from free‐space into sub‐wavelength‐sized structures and to enhance the electric field confinement. One of the most appealing plasmonic applications is biosensing: to detect and identify many bio‐information of a molecule in a single test. Consequently, surface enhanced spectroscopy in a broad infrared (IR) range is required. In this article, a barcode‐like nanostructured surface of a metal‐insulator‐metal (MIM) platform serves as optical transducer with tunable localized surface resonances (LSPR). The conception, fabrication, and optical characterization of periodic arrays of aluminum bowties (Al‐BT) within a MIM structure compatible with Si‐technology are reported. LSPR positions are extended by controlling the side length of the tip‐to‐tip facing triangles. The reflectance measurements correlate extremely well to numerical simulations. The simulated electrical field confinement provides up to 103 of intensity relying on the tip‐to‐tip nanogap value. Surface‐enhanced infrared absorption (SEIRA) gives simultaneously spectral information on both far‐field behavior and near‐field enhancement of several vibrational lines of our trial molecule (vanillin) achieved with the barcode‐like Al‐BT. The analysis of Fano‐like profiles is concluded with SEIRA enhancement factors higher than 107 for frequency tuning ratios below 1 between the far‐field plasmonic resonances and the selected vanillin IR absorption lines. [ABSTRACT FROM AUTHOR]

The label-free detection of SARS-CoV-2 spike protein is demonstrated by using slightly tapered no-core fiber (ST-NCF) functionalized with ACE2. In the fabricated sensor head, abrupt changes in the mode-field diameter at the interfaces between single-mode fiber and no-core fiber excite multi-guided modes and facilitate multi-mode interference (MMI). Its slightly tapered region causes the MMI to be more sensitive to the refractive index (RI) modulation of the surrounding medium. The transmission minimum of the MMI spectrum was selected as a sensor indicator. The sensor surface was functionalized with ACE2 bioreceptors through the pretreatment process. The ACE2-immobilized ST-NCF sensor head was exposed to the samples of SARS-CoV-2 spike protein with concentrations ranging from 1 to 104 ng/mL. With increasing sample concentration, we observed that the indicator dip moved towards a longer wavelength region. The observed spectral shifts are attributed to localized RI modulations at the sensor surface, which are induced by selective bioaffinity binding between ACE2 and SARS-CoV-2 spike protein. Also, we confirmed the capability of the sensor head as an effective and simple optical probe for detecting antigen protein samples by applying saliva solution used as a measurement buffer. Moreover, we compared its detection sensitivity to SARS-CoV-2 and MERS-CoV spike protein to examine its cross-reactivity. In particular, we proved the reproducibility of the bioassay protocol adopted here by employing the ST-NCF sensor head reconstructed with ACE2. Our ST-NCF transducer is expected to be beneficially utilized as a low-cost and portable biosensing platform for the rapid detection of SARS-CoV-2 spike protein. [ABSTRACT FROM AUTHOR]

Lateral Goos-Hänchen (GH) shifts at the Fano resonances are theoretically investigated in superconducting photonic crystals. The photonic system consists of superconductor layer pairs with embedded graphene and a dielectric layer. With an oblique incident light, multiple Fano resonances are realized in the transmission spectrum because of the embedded graphene. Large GH shifts of the reflected light, including positive (Δ p) and negative (Δ n) GH shifts, are obtained around the Fano resonances. The GH shifts almost keep stable for different chemical potentials of graphene. By decreasing hydrostatic pressure or incident angle, larger Δ p and | Δ n | are achieved and the corresponding frequency has a redshift. By increasing the ambient temperature, Δ p and | Δ n | first increase smoothly and then decrease sharply. Overall, Δ p is more sensitive than Δ n , while the reflectance corresponding to Δ n is much larger than that corresponding to Δ p. Large and tunable GH shifts in our study may have great potential for optical detectors and transducers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Use of local chlorine generation to reduce biofouling in optical sensors. • FTO glass coated with platinum nanoparticles outperforms uncoated FTO anodes. • The Pt-FTO 540 μA probe enabled 65 days of continuous and biofouling-free monitoring. • Effectiveness of copper biocide in protecting sensor housings. Biofouling in marine optical sensors poses a significant challenge as it can compromise data accuracy and instrument functionality. This study investigates the effectiveness of local chlorine generation by seawater electrolysis in mitigating biological fouling and extending the operational lifespan of optical oceanographic instruments. Eight similar turbidity probes integrated with a local chlorine generation system, along with a turbidity probe constructed from ABS and another from PLA with copper filament, were developed for testing in the marine environment. The chlorine probes were designed into two groups: four utilizing standard FTO glass and four featuring FTO glass coated with platinum nanoparticles. Each set of probes employed different excitation currents for chlorine generation. All probes underwent laboratory calibration using formazine before deployment in a coastal environment for 97 days. The findings demonstrate a correlation with higher electrical power leading to prolonged operation intervals free from biofouling interference. Additionally, probes coated with platinum nanoparticles demonstrate higher performance in comparison to those with standard FTO glass. The copper probe did not effectively shield the optical transducers from microfouling, although it effectively demonstrated its efficacy in protecting the structural housing of the device. Overall, this work offers a compelling in situ demonstration of local chlorine generation as a promising strategy for enhancing the performance and longevity of optical oceanographic instruments in marine environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanozyme-based biosensors have recently gained attention. • Nanozyme-based probes as electrochemical and optical transducers are discussed. • An overview of nanozymes, their classification and synthetic routes is provided. • Role of nanozyme-based biosensors for extensive biomolecular sensing is reviewed. • Prospects and challenges for commercialising nanozyme-based biosensors are outlined. As a potential substitute for naturally occurring enzymes, nanozymes (nanomaterials with enzyme-mimicking catalytic activity) have emerged in recent years. Natural enzymes have a number of intrinsic shortcomings that could be addressed by nanozymes, including their expensive price, poor stability, storage complexities, and reliance on particular working conditions (e.g., restricted substrate, pH, and temperature ranges). Therefore, the creation and deployment of sophisticated nanozymes has the potential to drastically alter the state of biosensor applications and the life sciences as they exist today. Biosensors have been utilized for quite some time as a streamlined method to quantitatively detect biomarkers (analytes) of interest. Therefore, the utilization of nanozymes in such biosensors assumes significant importance in the pursuit of cost-effective and dependable biosensors for therapeutic monitoring, disease prognosis, and diagnostics. Nanozymes have been investigated for a wide range of biosensing applications throughout the last few years. However, only few of such initiatives have produced platforms and devices that may be used for point-of-care and on-site monitoring. Hence, by providing a thorough overview of current developments in the classification of common nanozymes, this review seeks to guide and support the future development of biosensor technologies based on nanozymes, with an emphasis on their applications in the biosensing sector. We envision that this review will promote coordinated efforts across disciplines and sectors, helping to bridge the gap that keeps nanozyme-based biosensor technology confined to lab settings rather than being used in real-world situations. [ABSTRACT FROM AUTHOR]

The article proposes a model of a frame micro-optoelectromechanical angular velocity transducer with electrostatic excitation of primary oscillations. The transducer comprises optical readout units based on the optical tunnel effect to perform a precision optical reading of submicrometer movements of the sensing element. The linear region of the function of the working gap converting into optical power was determined after an experimental investigation of the optical reading unit. Two channels for reading optical signals were used to measure the amplitude of the sensing element's secondary vibrations (several hundreds of nanometers). The parameters of elastic suspensions were determined to ensure the secondary movement of the sensing element in the range of optical readout units with high sensitivity. The parameters of the proposed transducer and the nonlinearity of the transformation function in the range of measured angular velocities were estimated. The proposed micro-optoelectromechanical transducer can effectively measure the angular velocities of moving objects with high sensitivity. [ABSTRACT FROM AUTHOR]

In the last years, optical fiber sensors have proven to be a reliable and versatile biosensing tool. Optical fiber biosensors (OFBs) are analytical devices that use optical fibers as transducers, with the advantages of being easily coated and biofunctionalized, allowing the monitorization of all functionalization and detection in real-time, as well as being small in size and geometrically flexible, thus allowing device miniaturization and portability for point-of-care (POC) testing. Knowing the potential of such biosensing tools, this paper reviews the reported OFBs which are, at the moment, the most cost-effective. Different fiber configurations are highlighted, namely, end-face reflected, unclad, D- and U-shaped, tips, ball resonators, tapered, light-diffusing, and specialty fibers. Packaging techniques to enhance OFBs' application in the medical field, namely for implementing in subcutaneous, percutaneous, and endoscopic operations as well as in wearable structures, are presented and discussed. Interrogation approaches of OFBs using smartphones' hardware are a great way to obtain cost-effective sensing approaches. In this review paper, different architectures of such interrogation methods and their respective applications are presented. Finally, the application of OFBs in monitoring three crucial fields of human life and wellbeing are reported: detection of cancer biomarkers, detection of cardiovascular biomarkers, and environmental monitoring. [ABSTRACT FROM AUTHOR]

Label-free biosensors, and especially those based on optical transducers like plasmonic or silicon photonic systems, have positioned themselves as potential alternatives for rapid and highly sensitive clinical diagnostics, on-site environmental monitoring, and for quality control in foods or other industrial applications, among others. However, most of the biosensor technology has not yet been transferred and implemented in commercial products. Among the several causes behind that, a major challenge is the lack of standardized protocols for sensor biofunctionalization. In this review, we summarize the most common methodologies for sensor surface chemical modification and bioreceptor immobilization, discussing their advantages and limitations in terms of analytical sensitivity and selectivity, reproducibility, and versatility. Special focus is placed on the suggestions of innovative strategies towards antifouling and biomimetic functional coatings to boost the applicability and reliability of optical biosensors in clinics and biomedicine. Finally, a brief overview of research directions in the area of device integration, automation, and multiplexing will give a glimpse of the future perspectives for label-free optical biosensors. [ABSTRACT FROM AUTHOR]

High-intensity focused ultrasound (HIFU) transducers are proposed as a new treatment modality for dermatology. The shape and size of pressure fields generated by strongly focused transducers with an f-number equal to 0.75 operating at frequencies up to 20 MHz are analyzed analytically using the Lucas-Muir model and numerically with the wide-angle Khokhlov-Zabolotskaya-Kuznetsov method. The modeling results under quasi-linear conditions are compared against measurements performed in an acoustic tank with the aid of a fiberoptic hydrophone. The size of the focal zone expressed by their depth of focus and focal diameter is found to be directly controlled by their operating frequency and f-number. Devices manufactured for an operating frequency of 20 MHz are characterized by their 6 dB depth of focus of 490 μm and focal diameter of 80.6 µm. The devices are further studied at high power levels using a polyacrylic tissue-mimicking phantom. The devices are equipped with an optical observation system allowing simultaneous treatment and observation of the skin surface. In comparison to conventional cosmetic applications of HIFU, the devices analyzed are concluded to be ideal for treatment of precisely selected and confined layers of the human skin. [ABSTRACT FROM AUTHOR]