Optoelectronic Sensors Research Articles

Precise capture and dynamic relocation of nanoparticulate biomolecules through dielectrophoretic enhancement by vertical nanogap architectures

Toward the development of surface-sensitive analytical techniques for biosensors and diagnostic biochip assays, a local integration of low-concentration target materials into the sensing region of interest is essential to improve the sensitivity and reliability of the devices. As a result, the dynamic process of sorting and accurate positioning the nanoparticulate biomolecules within pre-defined micro/nanostructures is critical, however, it remains a huge hurdle for the realization of practical surface-sensitive biosensors and biochips. A scalable, massive, and non-destructive trapping methodology based on dielectrophoretic forces is highly demanded for assembling nanoparticles and biosensing tools. Herein, we propose a vertical nanogap architecture with an electrode-insulator-electrode stack structure, facilitating the generation of strong dielectrophoretic forces at low voltages, to precisely capture and spatiotemporally manipulate nanoparticles and molecular assemblies, including lipid vesicles and amyloid-beta protofibrils/oligomers. Our vertical nanogap platform, allowing low-voltage nanoparticle captures on optical metasurface designs, provides new opportunities for constructing advanced surface-sensitive optoelectronic sensors.

Method study for implantation positioning of corn seeds

To meet the needs of precision agriculture for crop location information, to achieve accurate plant position of crops, and to solve the problem of low resource utilization rate and high operation cost caused by repeated identification and positioning of plants in each part of field management, a seed positioning method was proposed by using maize planting as research object. A 4-row precision planter was used, all seed tubes were replaced with optoelectronic sensor (OE-sensor) equipped tubes to monitor seeds dropping. An RTK satellite receiver mounted on seeder frame girder provided global position. Furthermore, time and distance compensation model of seed from OE-sensor to implantation process was established based on EDEM numerical simulation. Seeds implantation location prediction and actual position measurement data acquisition programs were developed. Field test results showed that the mean, range and standard deviations (SD) of the longitudinal deviation between prediction location and actual position in operation direction were greater than vertical deviation which is perpendicular to operation direction. 87.7% of corn seeds dropped within 50mm from prediction location at operating speed of 3.2 km/h. This method can provide theoretical reference for synchronous generation of seed map in seeding process.

Impact of Tin concentration in ITO films on Optoelectronic sensor performance

In viewing the opportunity to enhance Photovoltaic application, nine samples having different concentrations (5%, to 70%) were synthesized by sol gel Acrylamide route. XRD study indicates the entire films exhibited single phase with bixbyte structure for all films. EDXA studies confirm the existence SnO2 enclosures in the entire samples. Atomic force micrographs of ITO films conclude that the grain size decreases with increase of tin concentration. Hot probe measurements reinforce the optimum concentration of tin (10%) for its transport properties, their optoelectronic application of DSSC. This paper focuses on the DSSC performance. In this work ITO films and their gas sensing characteristics are studied and their results are reported. ITO based H2S sensor with 70% tin concentration exhibited maximum sensitivity at 100 °C with higher recovery time than the response times. After a long time, ITO films with different concentrations of tin (450 °C) return to the original state.

Validation and Optimization of Calculated Stress Fields in Double-Mold Optoelectronics Sensor Packaging

Thermomechanical modeling of a new double-overmolded optical sensor package, comprising a highly filled, as well as an unfilled, strongly thermally expanding transfer molding compound, is presented. Materials’ characterization of the polymers using thermal, thermomechanical, dynamic, and optical correlation methods was used to set up finite element models of the three major steps in the assembly packaging process. The results of the simulation were validated by in-plane stress determination using a piezoresistive integrated circuit measured at various temperatures. In addition, the overall package substrate warpage was optically characterized while loading the sample on a hot plate. Agreement between the measurement and the simulation was only found when the stress-free state of the polymers was set to be at the curing-onset temperature. The results obtained are compared with different levels of complexity on materials’ characterization and constitutive modeling and could finally be used for sensitivity analysis of the sensor package design. A thicker and more compliant transparent molding compound in this package was found to reduce the stresses that could cause delamination.

A Hybrid Optoelectronic Sensor Platform with an Integrated Solution‐Processed Organic Photodiode

AbstractHybrid systems, unifying printed electronics with silicon‐based technology, can be seen as a driving force for future sensor development. Especially interesting are sensing elements based on printed devices in combination with silicon‐based high‐performance electronics for data acquisition and communication. In this work, a hybrid system integrating a solution‐processed organic photodiode in a silicon‐based system environment, which enables flexible device measurement and application‐driven development, is presented. For performance evaluation of the integrated organic photodiode, the measurements are compared to a silicon‐based counterpart. Therefore, the steady state response of the hybrid system is presented. Promising application scenarios are described, where a solution‐processed organic photodiode is fully integrated in a silicon system.

Influence of film thickness on structural and optical properties of 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine nanostructure thin films for optical applications

Porphine compounds have potential applications on optoelectronic and gas sensors. Organic films of 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine (TTBTP) were fabricated by thermal evaporation method. The atomic force microscopy of TTBTP films demonstrates that these films have uniformly distributed grains. As the thickness increases, the grain size increases, and film morphology seem to be uniform with large grains. The Raman spectra of TTBTP powder and films were studied and showed the mean four peaks characterized the TTBTP at 970, 1074, 1308, and 1583 cm−1. The transmittance spectra confirmed the homogeneity of TTBTP films. Also, it is found that TTBTP films have an indirect electronic transition with two energy bandgaps (Eg1 = 1.75 eV and Eg2 = 3.42 eV) and their values decreased as the film thickness increments. The optical constants were calculated, and the refractive index increments with increasing in the film thickness. This outcome might be credited to the interlude of the film in the initial phase of the deposition. The nonlinear optical parameters for TTBTP film were calculated and found that the third-order optical nonlinearity was increased with increasing the film thickness.

Combining of objects images under conditions of inaccurate description of their images

An attribute of modern robotic systems and control systems for unmanned vehicles is a machine vision, which is based on processing of images obtained from highly informative radar or optoelectronic sensors. Effective image processing and recognition procedures are based on use of morphological features of objects images with high space‑time stability. This paper considers one of the aspects of images morphological analysis related to the influence of errors in the reference contour descriptions of objects. With use of developed analytical apparatus it is shown that the result of such errors is a decreasing of object/background contrast and, as a result, increasing of image comparison errors. The degree of this increase depends on the object type (area, linear) and its characteristics (size, contrast). Practical recommendations on the acceptable level of errors in the representation of object descriptions are justified.

Detecting Soil Microarthropods with a Camera-Supported Trap.

There is an increasing need to monitor activity and population growth of arthropods; however, this is a time-consuming and financially demanding process. Using sensors to detect arthropods in the field can help to follow their dynamics in time. Improving our earlier device, we developed a new camera-supported probe to detect soil microarthropods. An opto-electronic sensor ring detects the caught microarthropod individuals what activates a camera. The camera takes pictures of a specimen when it arrives in the camera chamber. A vacuum device was built into the probe which pumps up the specimen from the probe to a sample container. Here, we describe the construction and operation of the probe. We investigated the precision of the process in a laboratory experiment using living microarthropods and evaluated the accuracy of the probes in a semi-natural investigation when environmental noise was present. Under semi-natural conditions, the percentages of success, i.e., the photographed specimens compared to the caught ones, were between 60% and 70% at the investigated taxa. The automatic camera shooting helped in distinguishing insects from irrelevant detections while collecting the trapped insects allowed species-level determination. This information together serves as a basis for the automatic visual recognition of microarthropod species.

Study of oxygen plasma induced modulation of photoconductivity in MoS2 field effect transistor

Abstract We studied the effect of oxygen plasma treatment on the drain current and photoconductivity of the two dimensional few-layers MoS2 based field-effect transistors (FETs). It was observed that the oxygen plasma can reduce the photoconductivity of MoS2 channel along with variation in the current characteristics. This study shows the contribution of mild oxygen plasma to modulate the photoconductivity of the MoS2 FETs which can have potential in optoelectronic detectors and sensors applications.

Simulation studies of a vision intruder detection system

PurposeThe purpose of this paper is to describe simulation research carried out for the needs of multi-sensor anti-collision system for light aircraft and unmanned aerial vehicles.Design/methodology/approachThis paper presents an analysis related to the practical possibilities of detecting intruders in the air space with the use of optoelectronic sensors. The theoretical part determines the influence of the angle of view, distance from the intruder and the resolution of the camera on the ability to detect objects with different linear dimensions. It has been assumed that the detection will be effective for objects represented by at least four pixels (arranged in a line) on the sensor matrix. In the main part devoted to simulation studies, the theoretical data was compared to the obtained intruders’ images. The verified simulation environment was then applied to the image processing algorithms developed for the anti-collision system.FindingsA simulation environment was obtained enabling reliable tests of the anti-collision system using optoelectronic sensors.Practical implicationsThe integration of unmanned aircraft operations in civil airspace is a serious problem on a global scale. Equipping aircraft with autonomous anti-collision systems can help solve key problems. The use of simulation techniques in the process of testing anti-collision systems allows the implementation of test scenarios that may be burdened with too much risk in real flights.Social implicationsThis paper aims for possible improvement of safety in light-sport aviation.Originality/valueThis paper conducts verification of classic flight simulator software suitability for carrying out anti-collision systems tests and development of a flight simulator platform dedicated to such tests.

Near resonant nanosecond laser-driven nonlinear optical response in As50S50 thin films

Nanosecond near resonant excitation in As50S50 thin films leads to strong nonlinear optical response, i.e. nonlinear absorption coefficient up to 4 × 106 cm GW−1 and nonlinear refractive index of 8.5 cm2 GW−1, both of which are the strongest ever reported in amorphous semiconductors. We propose a three-level energy band model to explain this effect, which indicates that the nonlinear process is reverse saturable absorption in nature, mediated by excited-state absorption from slow interband transition between the conduction and valence band. On the other hand, observation of negative nonlinear refractive index reveals the occurrence of self-defocusing effect. Finally, benefitting from the strong nonlinear response, we demonstrate a promising application of As50S50 thin films as an optical limiter for optoelectronic sensors.

A Contact Force Sensor Based on S-Shaped Beams and Optoelectronic Sensors for Flexible Manipulators for Minimally Invasive Surgery (MIS)

Flexible, highly articulated robotic tools can greatly facilitate procedures in which the operator needs to access small openings and confined spaces. Particularly, in the context of robotic-assisted minimally invasive surgery (RMIS), the application of such manipulation tools can be significantly beneficial in preventing unnecessary interactions with sensitive body organs by which reducing patient’s recovery time when compared with conventional methods. However, these systems usually lack tactile feedback and are not able to perceive and quantify the interactions between themselves and soft body organs. This deficiency may result in damaging the organs due to unwanted excessive force applied. To this end, we introduce a contact force sensor based on three ’dyadic-S-shaped’ beams and three optoelectronic sensors. The modular design of a flexible manipulation system described as part of this paper allows ready integration of a series of the proposed sensors within its structure. The sensor uses our novel sensing principle for measuring contact forces. The strategic employment of custom sensor structure and the optoelectronic components fulfill our design objectives which have been focused on the creation of a modular, low-cost, low-noise (electrically) with large voltage variation, without the need for an amplifier, through a simple fabrication process for MIS. Our experimental results, following a very simple calibration processes show the average errors of ${F}_{x}$ (+19.37%±0.82, −18.32%±2.06) and ${F}_{y}$ (+18.56%±1.69, −17.00%±1.32), and the average RMS errors of ${F}_{x}$ (0.12N±0.0067) and ${F}_{y}$ (0.11N±0.0032) in the measurement of force values within the range of −4 to 4 N.

An installation for studying optoelectronic humidity sensor

An installation for studying optoelectronic humidity sensor

Image sensors for digital photography: a short course for undergraduates. I: Optics

Over the last half century, photography has evolved from photochemical reactions induced on a photosensitive film to optoelectronic devices employed in digital image. Video has done the same migration from classical film movies to optoelectronic acquisition and storage. Digital and video cameras share optics with traditional film cameras, but the image recording is realized by an optoelectronic device –a CCD or CMOS sensor– rather than a film. The quantity of digital photo and video images has dramatically increased in the last decade, arising from the ubiquitous cameras of mobile phones. Despite their popularity, condensed tutorial articles on the subject are still scarce. This work intends to contribute to the knowledge of this field with a medium-level short course that is currently being taughtin a broader subject (Consumer Photonics) to undergraduate students of Telecommunication Engineers at the Universidad Politecnica de Madrid. The course can be followed by students having a basic background on Physics and specifically on Optics and Semiconductors. The course is divided into two chapters. An introduction to optics of cameras and basic concepts of photography has been considered necessary to follow the second part, which is entirely devoted to optoelectronic sensors

Structural, optical, and surface morphological studies of ethyl cellulose/graphene oxide nanocomposites

AbstractMotivated by the outstanding properties and unique structure of graphene oxide (GO), the polymer nanocomposites of ethyl cellulose (EC) as a polymer matrix and the GO as a nano‐filler have been prepared with the different GO wt% concentrations using simple solution blending technique followed by the ultrasonication treatment and characterized by using various advanced techniques. The X‐ray diffraction (XRD) was utilized to determine the preliminary phase determination and for the structural analysis. The optical band gaps were determined with the help of UV‐Vis‐NIR spectrophotometer and were verified by the PL spectra using Spectro‐Fluorescence. According to experimental results, the optical bandgap of the nanocomposite was found to reduce with increasing GO content. The field emission scanning electron microscopy (FESEM) was used to study the surface morphology and to identify the presence of GO in the nanocomposites. The Fourier transform infrared (FTIR) study has been carried out to recognize the presence of functional groups and their vibrational mechanisms. Micro‐Raman imaging technique has been used to determine the Raman bands present in the nanocomposites. The optical band gap of the nanocomposites reflects the semiconducting nature, which might be used in optoelectronic devices and sensor applications.

Decreased respiratory-related postural perturbations at the cervical level under cognitive load.

In healthy humans, postural and respiratory dynamics are intimately linked and a breathing-related postural perturbation is evident in joint kinematics. A cognitive dual-task paradigm that is known to induce both postural and ventilatory disturbances can be used to modulate this multijoint posturo-ventilatory (PV) interaction, particularly in the cervical spine, which supports the head. The objective of this study was to assess this modulation. With the use of optoelectronic sensors, the breathing profile, articular joint motions of the cervical spine, hip, knees and ankles, and centre of pressure (CoP) displacement were measured in 20 healthy subjects (37years old [29; 49], 10 females) during natural breathing (NB), a cognitive dual task (COG), and eyes-closed and increased-tidal-volume conditions. The PV interaction in the CoP and joint motions were evaluated by calculating the respiratory emergence (REm). Only the COG condition induced a decrease in the cervical REm (NB: 17.2% [7.8; 37.2]; COG: 4.2% [1.8; 10.0] p = 0.0020) concurrent with no changes in the cervical motion. The CoP REm (NB: 6.2% [3.8; 10.3]; COG: 12.9% [5.8; 20.7] p = 0.0696) and breathing frequency (NB: 16.6min-1 [13.3; 18.7]; COG: 18.6min-1 [16.3; 19.4] p = 0.0731) tended to increase, while the CoP (p = 0.0072) and lower joint motion displacements (p < 0.05) increased. This study shows stable cervical spine motion during a cognitive dual task, as well as increased postural perturbations globally and in other joints. The concurrent reduction in the PV interaction at the cervical spine suggests that this "stabilization strategy" is centrally controlled and is achieved by a reduction in the breathing-related postural perturbations at this level. Whether this strategy is a goal for maintaining balance remains to be studied.

Pressure-Sensitive Insoles for Real-Time Gait-Related Applications.

Wearable robotic devices require sensors and algorithms that can recognize the user state in real-time, in order to provide synergistic action with the body. For devices intended for locomotion-related applications, shoe-embedded sensors are a common and convenient choice, potentially advantageous for performing gait assessment in real-world environments. In this work, we present the development of a pair of pressure-sensitive insoles based on optoelectronic sensors for the real-time estimation of temporal gait parameters. The new design makes use of a simplified sensor configuration that preserves the time accuracy of gait event detection relative to previous prototypes. The system has been assessed relatively to a commercial force plate recording the vertical component of the ground reaction force (vGRF) and the coordinate of the center of pressure along the so-called progression or antero-posterior plane (CoPAP) in ten healthy participants during ground-level walking at two speeds. The insoles showed overall median absolute errors (MAE) of 0.06 (0.02) s and 0.04 (0.02) s for heel-strike and toe-off recognition, respectively. Moreover, they enabled reasonably accurate estimations of the stance phase duration (2.02 (2.03) % error) and CoPAP profiles (Pearson correlation coefficient with force platform ρCoP = 0.96 (0.02)), whereas the correlation with vGRF measured by the force plate was lower than that obtained with the previous prototype (ρvGRF = 0.47 (0.20)). These results confirm the suitability of the insoles for online sensing purposes such as timely gait phase estimation and discrete event recognition.

One-step fabrication of 1D p-NiO nanowire/n-Si heterojunction: Development of self-powered ultraviolet photodetector

Even though there are reports on NiO-p/Si-n based photodetector, work along 1D NiO/Si self-powered photodetector remains unexplored. 1D materials offer better electron mobility and can provide ballistic transport channel, which helps in achieving high responsivity. In this work, direct single-step deposition of p-type NiO nanowires on n-type Si as a self-powered photodetector was successfully fabricated by engaging simple electrospinning technique. The structural properties as observed from XRD indicate highly crystalline NiO nanowires and FESEM images revealed 60-75 nm diameter with uniform distribution. Growth of nanowires by using stimuli polymer and its completely removal at high temperature was confirmed using TGA and XPS analysis. The responsivity of the fabricated photodetector was calculated to be 9.1 mA W−1 at zero bias, which can be attributed to the p-type NiO interface with the n-type Silicon, which creates an internal electrical field thereby assisting in the effective separation of the photogenerated carriers. Further, under illumination, at zero bias, the photogenerated current still exists suggesting a generation of internal voltage, which makes the fabricated device as self-powered. This fabrication method will enhance the photodetection properties, and it can be implemented in the fields of optoelectronic devices, sensors, and flexible electronics.

Opto-Electronic Refractometric Sensor Based on Surface Plasmon Resonances and the Bolometric Effect

The bolometric effect allows us to electrically monitor spectral characteristics of plasmonic sensors; it provides a lower cost and simpler sample characterization compared with angular and spectral signal retrieval techniques. In our device, a monochromatic light source illuminates a spectrally selective plasmonic nanostructure. This arrangement is formed by a dielectric low-order diffraction grating that combines two materials with a high-contrast in the index of refraction. Light interacts with this structure and reaches a thin metallic layer, that is also exposed to the analyte. The narrow absorption generated by surface plasmon resonances hybridized with low-order grating modes, heats the metal layer where plasmons are excited. The temperature change caused by this absorption modifies the resistance of a metallic layer through the bolometric effect. Therefore, a refractometric change in the analyte varies the electric resistivity under resonant excitation. We monitor the change in resistance by an external electric circuit. This optoelectronic feature must be included in the definition of the sensitivity and figure of merit (FOM) parameters. Besides the competitive value of the FOM (around 400 RIU − 1 , where RIU means refractive index unit), the proposed system is fully based on opto-electronic measurements. The device is modeled, simulated and analyzed considering fabrication and experimental constrains. The proposed refractometer behaves linearly within a range centered around the index of refraction of aqueous media, n ≃ 1.33 , and can be applied to the sensing for research in bio-physics, biology, and environmental sciences.

High-temperature dielectric switch and second harmonic generation integrated in a stimulus responsive material

Stimulus responsive materials can provide a variety of desirable properties in one equipment unit, such as optoelectronic devices, data communications, actuators, memories, sensors and capacitors. However, it remains a large challenge to design such stimulus responsive materials, especially functional materials having both dielectric switch and second harmonic generation (SHG). Here, a new stimuli-responsive switchable material [(CH3)3N(CH2)2Cl]2[Mn(SCN)4(H2O)2] was discovered as a potential second-harmonic generation (SHG) dielectric switch. It is worth noting that it has SHG characteristics before and after undergoing reversible high-temperature phase transitions. In this work, we successfully refined the tetramethylammonium cation to obtain a quasi-spherical cation, which is tetramethylchloroethylamine (TMCEM) cation. By substituting H with a halogen, the increased steric hindrance of the molecular makes energy barrier increased, resulting in the reversible high-temperature phase transition. At the same time, the interactions of quasi-spherical cations and [Mn(SCN)4(H2O)2]2− anions affect a non-centrosymmetric structure to induce the SHG effect. These findings provide a new approach to design novel functional switch materials.