Disposable optical sensor chip for medical diagnostics: new ways in bioanalysis

An optical sensor system is described which is particularly well suited for medical point-of-care diagnostics. The system allows for all kinds of immunochemical assay formats and consists of a disposable sensor chip and an optical readout device. The chip is built up from a ground and cover plate with in- and outlet and, between, of an adhesive film with a capillary aperture of 50 microns. The ground plate serves as a solid phase for the immobilization of biocomponents. In the readout device, an evanescent field is generated at the surface of the ground plate by total internal reflection of a laser beam. This field is used for the excitation of fluorophor markers. The generated fluorescence light is detected by a simple optical setup using a photomultiplier tube. Because of the evanescent field excitation, washing or separation steps can be avoided. With this system the pregnancy hormone chorionic gonadotropin (hCG) could be determined in human serum with a detection limit of 1 ng/mL. Recovery values were 86, 106, and 102% for 5, 50, and 100 ng/mL hCG, respectively. The SD in repeated measurements (n = 10) was 5.6%. Furthermore, the feasibility of the system in competitive-type immunoassays was demonstrated for serum theophylline. A linear calibration curve of signal vs theophylline between 1 and 50 mg/L was obtained. Recovery values varied between 118% (10 mg/L) and 81.0% (20 mg/L).     

Olfactory receptor-based polypeptide sensor for acetic acid VOC detection

Rapid detection of food-borne pathogens in packaged food products can prevent the spread of infectious diseases. This study investigates the application of novel sensing material that is sensitive to specific indicator volatile organic compound (VOC) related to Salmonella contamination in packaged meat. Specifically, the objective was to develop an olfactory receptor-based synthetic polypeptide sensor for the detecting acetic acid in low concentrations and at room temperature. Synthetic polypeptide was deposited on a quartz crystal microbalance (QCM) electrode and was evaluated for detecting acetic acid at 10–100 ppm. Developed sensor exhibited repeatable response to a particular concentration of acetic acid and displayed reproducibility among multiple sensors during acetic acid detection. Mean estimated lower detection limits of these sensors were about 1–3 ppm and linear calibration models showed linear relationships. Thus, the QCM sensors exhibited a great potential for detecting low concentrations of acetic acid at room temperature and can be used in the sensor array for packaged meat spoilage and contamination detection.     

Disposable electrochemical sensor for determination of nitroaromatic compounds by a single-run approach

Environmental and security applications have generated major demands for effective field-deployable tools for detecting nitroaromatic compounds, such as chloramphenicol (an antibiotic), parathion (an organophosphate nerve agent), and TNT (2,4,6-trinitrotoluene, an explosive) in a fast, simple, sensitive, reliable, and cost-effective manner. We report here a single-run approach for such a purpose. The reduction potential of different nitroaromatic compounds was found to systematically shift with the substituent group at an electrochemically preanodized screen-printed carbon electrode. The preanodization treatment makes the peak sharp and hence provides a precise way to identify the substituent effect on nitroaromatic compounds. By using potential shifts as analytical characteristics of nitroaromatic compounds, a suitable internal standard can be chosen based on the criteria of well-separated peak potential and rarely found in the real sample of interest. Simply by measuring the ratio of peak currents between analytes of interest and internal standard, the analysis can be done in a single-run measurement. Both the matrix effect and the variation of electrode during the preparation process can be canceled out in this approach and thus allows for a high-precision analysis. Just by placing a 20-microL drop on a single-use amperometric sensor strip incorporating a three-electrode configuration is enough for rapid and sensitive detection of nitroaromatic compounds by square-wave voltammetry. For example, the linear detection range can be up to 100 microM with a detection limit of 0.42 microM (S/N = 3) in the detection of chloramphenicol. This approach was successfully demonstrated in real sample analysis to verify the applicability of the method. The promising performances open new possibilities for rapid determination of nitroaromatic compounds in environmental and biological samples.     

Interferometric optical sensor for measuring glucose concentration

With a specially designed probe, the phase difference between s andp polarization of light reflected under surface-plasmon resonance is measured by use of a common-path heterodyne interferometer. For specific ratios of phase difference to glucose concentration, the glucose concentration can be estimated as a function of the measured phase data. A prototype was set up to demonstrate the feasibility of this sensor, which was experimentally tested in the range 40-500 mg/dl with a small quantity of solution and had a measurement resolution of 1.41 mg/dl at 25 degrees C.     

光扭矩传感器信号转换误差分析

光扭矩传感器的输出信号在进行光电转换过程中，由于温度影响，造成了直流电平漂移误差，影响系统的测量精度。对直流电平漂移误差进行了分析，针对产生误差的原因提出了采用正负温度补偿、热敏电阻和差动电路三种补偿方案，并进行了比较。实验结果表明，采用差动补偿电路的方法，效果良好，能有效地消除直流电平漂移误差。     

Piezoelectric optical fiber stretcher for application in an atmospheric optical turbulence sensor

A piezoelectric optical fiber stretcher has been introduced for working point controlling and low-frequency noise suppression of a fiber-optic atmospheric turbulence sensor. It is actuated by a piezoelectric ceramic stack. The rational structure allows the fiber to extend only along the axial direction, which minimizes the nonlinear birefringence effects for the optical phase shift. What is believed to be a novel method has been proposed to measure its phase-shift coefficient. With the use of this device, the fiber-optic atmospheric turbulence sensor has been tested for the air refractive index measurement.     

A receptor-based bioassay for quantitative detection of gallium

The detection of gallium in biological samples is required due to its role in the diagnosis of tumor and for possible treatment of malignancies. However, the use of purely instrumental techniques is unsuitable for detection of low levels of gallium in biological matrixes. We have synthesized new protein conjugates based on 4-(2-pyridylazo) ligands. The conjugates were successfully employed for the detection of gallium in biological matrixes using a nonantibody-based sandwich assay format. The recovery level obtained was between 97 and 101.3 with a relative standard deviation of less than 5%. The assay resulted in a detection limit of 5 x 10(-8) M and a remarkable selectivity for gallium(III) relative to other metals investigated. The new method provided adequate accuracy for gallium applicable for animal physiology and clinical toxicology.     

一种新型光学直流电压传感器

通过引进电光λ/4波片的Jones矩阵,阐明了用脉冲控制的电光波片构成的光学直流电压传感器的敏感特性;该传感器结构把被测量的直流电压信号转换成了交流脉冲控制的电压信号,因此输出电压信号对电磁干扰不敏感,且消除了输入光强波动的影响;双光路的输出结构消除了温度变化引起的干扰双折射的影响.用该传感器对-500～500V的直流电压进行了测量,其非线性误差在±0.5%以内,实验结果表明,该传感器结构是可行的.     

Micromachined optical fiber current sensor

We describe a micromachined optical fiber current sensor. The sensing element consists of a squared silicon membrane (8 mm long and 20 mum thick) that has a cylindrical permanent magnet (NdFeB alloy, 3-mm diameter, 1.5 mm high) fixed on its central region. This structure allows the permanent magnet to vibrate in the presence of the magnetic field gradient generated by an ac. A linear relation between the electrical current and the magnet displacement was measured with white-light interferometry with an optical fiber low-finesse Fabry-Perot microcavity. A measurement range of 0-70 A and a minimum detectable intensity of 20 mA were obtained when distance D between the membrane and the electrical power line was 5 mm. The output signal directly shows a linear response with distance D.     

Compact and flexible optical sensor designed for on-line monitoring

A new on line optical sensor based on light scattering dedicated to real-time monitoring during processing of polymers blends and polymers nanocomposites has been developed. The sensor is designed to monitor the quality of a polymer melt or of a dispersion of nanofillers in a polymeric matrix during the process of extrusion. This sensor presents three openings: two for light sensor setups (one for transmission measurements and the other for 90°-scattered light measurements) and one for the incident laser beam. The experimental validation of this optical sensor has been realized on two materials: poly(methyl methacrylate) (PMMA) and on the nanocomposites obtained by the melt mixing of this polymer matrix with modified montmorillonite (MMT) clays. Experimental results proved the good results in terms of signal repeatability and sensitivity to organoclay particle concentration and structures of nanocomposites respectively.     

Xerogel optical sensor films for quantitative detection of nitroxyl

Xerogel sensing films were synthesized via sol-gel chemistry were used to fabricate optical nitroxyl (HNO) sensors [corrected] Selective detection of HNO in solution was achieved by monitoring the rates of manganese(III) meso-tetrakis(4-sulfonatophenyl) porphyrinate (MnIIITPPS) reductive nitrosylation in the anaerobic interior of aminoalkoxysilane-derived xerogel films. Nitroxyl permeability in sensor films deposited in round-bottom 96-well plates was enhanced via incorporation of trimethoxysilyl-terminated poly(amidoamine-organosilicon) dendrimers in the xerogel network. The selectivity of MnIIITPPS for HNO, the overall sensitivity, and the working dynamic range of the resulting sensors were characterized. The HNO-sensing microtiter plates were used to quantify pH-dependent HNO generation by the recently described HNO-donor sodium 1-(isopropylamino)diazene-1-ium-1,2-diolate (IPA/NO), and compare HNO production efficiency between IPA/NO and Angeli's salt, a traditional HNO-donor.     

A dual modality optical fiber sensor

We propose and demonstrate a fibre optic system based on bi-tapered silica fibre that can simultaneously measure strain and fibre curvature. Both modalities on the signal can be extracted with no measurable crosstalk between them. The experimental signal has a pure phase modulation when strain is applied to the tapered fibre optic section of the sensor and the signal shows only intensity modulation when an un-tapered fibre section is bent. High sensitivity is achieved from the experimental results for strain and bending losses and the estimation of measurement errors is 0.2 and 0.1%, respectively. This system offers low-cost, compactness and it can be adapted for structural health monitoring.     

A reflectometric optical fiber temperature sensor

A reflectometric fiber-optic temperature sensor was manufactured and characterized. The sensing probe is obtained by replacing the cladding with a temperature sensitive liquid on a short length of fiber. Its reduced dimensions make it suitable for monitoring applications whenever a high spatial resolution is required. A numerical modeling of the sensor, based on a ray-tracing technique, was carried out. The metrological performance of the first prototype seems to be very interesting in terms of accuracy and, above all, response time. A system for multipoint temperature measurements is also described.     

Temperature measurement by multifiber optical sensor

The paper deals with a new multifiber temperature sensor, based on the relationship between temperature and the refractive index of a suitable reference liquid, which replaces a part of the fiber cladding. The sensing element, the microcontroller-based hardware, and the artificial neural network (ANN)-based measurement software are described. The results of the tests carried out in the range 40°C-110°C showed good prototype accuracy and repeatability (both contained within ±0.5°C)     

Shack-Hartmann sensor improvement using optical binning

We present a design improvement for a recently proposed type of Shack-Hartmann wavefront sensor that uses a cylindrical (lenticular) lenslet array. The improved sensor design uses optical binning and requires significantly fewer detector pixels than the corresponding conventional or cylindrical Shack-Hartmann sensor, and so detector readout noise causes less signal degradation. Additionally, detector readout time is significantly reduced, which reduces the latency for closed loop systems and data processing requirements. We provide simple analytical noise considerations and Monte Carlo simulations, we show that the optically binned Shack-Hartmann sensor can offer better performance than the conventional counterpart in most practical situations, and our design is particularly suited for use with astronomical adaptive optics systems.     

Multidimensional optical sensor and imaging system

We describe a multidimensional optical sensor and imaging system (MOSIS). Using a time-multiplexing, polarimetric, and multispectral imaging system, we are able to reconstruct a fully integrated multidimensional scene. Image fusion is used to integrate the multidimensional images. The fused image contains more information than the single two-dimensional and three-dimensional (3D) images. The multidimensional imaging system utilizes polarimetric imaging, multispectral imaging, 3D integral imaging with time and space multiplexing, and 3D image-fusion techniques to reconstruct the multidimensionally integrated scene. Optical experiments and computer simulations are presented.     

Radioluminescent light source for the development of optical sensor arrays

A radioluminescent (RL) light source is evaluated for the development of photonically based chemical-responsive sensor arrays (CRSAs). The RL light source is comprised of a strontium-90 (90Sr) radionuclide and a plastic scintillator. The beta particles emitted from the 90Sr generate blue light (lambda(max) = 435 nm) from the plastic scintillator, and the blue light excites the analyte-responsive luminophores within the CRSA. To assess the RL light source utility, we have determined the analytical figures of merit from two tris(4,7'-diphenyl-1,10'-phenathroline)ruthenium(II)-doped xerogel-based sensor platforms: (i) a planar 5 x 5 multielement array and (ii) a discrete sensor element formed on the proximal face of poly(styrene) pillars that have a frustrated cone (frustum) geometry. We compare the performance from each platform when it is excited by a He-Cd laser (442 nm), a blue light-emitting diode (460-470 nm), and the RL light source. The RL light source yields results that are statistically equivalent to results from either electrically powered light source. The RL light source consumes no electrical power, is compact and simple, and has an extremely stable time-averaged signal. The primary trade-offs for these advantages are the RL light source's lower radiant power and the corresponding longer data acquisition times.     

New azobenzene non-linear optical materials for eye and sensor protection

The synthesis and properties of poly(methylmethacrylate) films containing new azobenzene materials with potential applications in eye and sensor protection devices are reported. These films offer both improved wavelength coverage and optically-induced anisotropy compared to a commercially available azo dye, disperse red-1. Films with added diethyl phthalate plasticizer exhibit enhanced optical characteristics, as evidenced by the relatively faster response time in a pump–probe experiment. Plasticized polymer films showed good mechanical, thermal and optical stability.