Papers by Keyword: Sensor

Abstract: A new composite of graphene/MoS₂ is synthesized by co-exfoliation of graphite and MoS₂ in isopropanol (IPA) using the organic salt potassium sodium tartrate as the assistant. The composite is characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectra. The results of TEM, XPS, and Raman spectra all illustrate that the graphene/MoS₂ composite has been synthesized successfully. Furthermore, the composite is modified on glassy carbon electrode to fabricate a sensor to detect dopamine (DA). The sensor shows two linear detection ranges for DA. One is 1-45 μM and the other is 45-120 μΜ. The detection limit of the sensor (S/N=3) is 0.76 μM.

Abstract: This paper presents the feasibility of developing an electromechanical in-situ viscosity measurement technique by analyzing the detectability of small variations in the viscosity of different shear thickening fluids and their different compositions. Shear thickening fluid (STF) is a kind of non-Newtonian fluid showing an increasing viscosity profile under loading. STF is utilized in several applications to take advantage of its tunable rheology. However, process control in different STF applications requires rheological measurements, which cause a costly investment and long-lasting labor. Therefore, one of the most commonly used in-situ structural health monitoring techniques, electromechanical impedance (EMI), was used in this study. In order to actuate the medium electromechanically, a piezoelectric wafer active sensor (PWAS) was used. The variations in the spectral response of PWAS resonator that can be submerged into shear thickening fluid are analyzed by the root mean square deviation, mean absolute percentage deviation and correlation coefficient deviation. According to the results, EMI metrics provide good correlations with the rheological parameters of STF and thereby enabling quick and low-cost rheological control for STF applications such as vibration dampers or stiffness control systems.

Abstract: Escherichia coli bacteria sensors have been broadly developed broadly to overcome a diarrheal disease caused by Escherichia coli on poor hygienic water. Sensing layer, as a main part of the sensor, contacts directly to the analyte on sensors system. Some materials were costly and harmful to detect bacteria. Potentially, graphene is a natural carbon derivative with some excellence properties; easy synthesis, and biocompatible. Hence, the quality of the SiO₂/graphene sensing layer was conducted through optical, physical, and electrical characterization to analyze biocompatibility, repeatability, and selectivity. The result showed that Escherichia coli bacterial growth was found around SiO₂/graphene after bacterial exposure indicating a biocompatible material. Raman peak also pointed the fingerprint of graphene after 25 times Escherichia coli exposure through G (1584.52 cm^–1) and 2D peak (2701.5 cm^–1) promising as a repeatable material. The ID/IG ratio increased by the time the bacteria exposure times increased indicating a withstand material from defects and or disorders after bacteria exposure. Through I/V meter, the increasing number of Escherichia coli could increase the resistance value of SiO₂/graphene. This sensing layer could detect the presence of Escherichia coli in limit of detection 16 CFU/mL.

Abstract: The rapid glucose detection is great significance in the food, biological and medical fields. In this paper, we show an unusual strategy for the synthesis of α-Fe₂O₃/g-C₃N₄ composite material with C-O-Fe bonds for applications in glucose detection. The structural composition and the existence of C-O-Fe bonds of α-Fe₂O₃/g-C₃N₄ were evaluated by XRD, FTIR, SEM, TEM and XPS. Due to the formation of C-O-Fe bonds, the BET surface area and electron transport ability of α-Fe₂O₃/g-C₃N₄ are improved. The electrochemical experiments revealed that the α-Fe₂O₃/g-C₃N₄ sensor exhibited a fast response time (< 5 s), a low detection limit (2.3 μM) and a wide linear range (0.1 mM - 5 mM). Furthermore, the powerful C-O-Fe binding energy provides a guarantee for the reasonable stability of the α-Fe₂O₃/g-C₃N₄ sensor. The presence of high concentrations of KCl, citric acid, ascorbic acid, dopamine and sucrose appeared to have no effects on the detection of glucose, indicating a high selectivity of this sensor.

Abstract: A rehabilitation device for a post-stroke is essential because stroke attacks can cause disable to part or half of the human body. An exoskeleton could be a vital device for rehabilitation for a post-stroke patient. Several studies have proposed the exoskeleton design for rehabilitation purposes to a human limb disorder. This study aims to review the state-of-the-art of hand exoskeleton devices based on myoelectric or any other sensors. This paper is expected to contribute to design a hand exoskeleton device using both myoelectric and force sensors. This was achieved by reviewing several articles related to the development of the exoskeleton, especially in the sensor system, data processing, and actuator system. The results show that the use of Ag electrode disposable Ag (AgCl) is still commonly found to detect the movement of the fingers on the hand because this sensor can reduce the artifact noise. The use of myo-armband is also found in several studies because it has wireless properties so that it is easy to use. In terms of processors, Arduino microcontrollers are more widely used than others. In order to activate the hand exoskeleton, servo motors are more widely used to actuate the finger joints, which is more precise than other actuators. In a further development, integration between exoskeleton systems and information systems will be an expected challenge. Furthermore, hopefully, the development of this exoskeleton can be applied as a rehabilitation device for patients with malfunction or hand paralysis.

Abstract: Direct laser processing of various materials with nano- and femtosecond (fs) laser pulses is known to be a facile and inexpensive technology for fabrication of various surface morphologies. Since ultrafast deposition of the laser energy to target material typically creates unique experimental conditions with extremely high pressure and temperature, we hypothesized that carrying out this process in anhydrous non-oxidizing environment containing functionalizing agent (fluorophore with vinyl functional group) will allow one-step fabrication and subsequent functionalization of the surface of high-n material. In this paper, we demonstrate successful implementation of this idea by fabricating high-spatial-frequency laser-induced periodic surface structures (LIPSS) via direct fs-pulse ablation of bulk crystalline Si wafer immersed in solution of N-vinylcarbazole in toluene. Laser processing with linearly polarized fs-laser pulses was found to produce LIPSS with a characteristic period around 100 nm functionalized with N-vinylcarbazole molecules via photo-activated hydrosililation reaction. The unique LIPSS with hierarchical roughness and remarkable light trapping performance functionalized with sensory fluorophore show high sensitivity due to implementation of surface enhanced fluorescence effect. By using N-vinylcarbazole as functionalizing agent we demonstrate one-step fabrication of high-performance sensor for detecting nitrobenzene in water with a detection limit of 40 nM.

Abstract: In manufacturing technology, sensors are important elements for monitoring process parameters and for recording data in the Industrie 4.0. Thin sensors manufactured by means of physical vapor deposition (PVD) offer a way to combine wear and corrosion protection on the one hand and the integration of a temperature sensor function on the other hand. For the analysis of the performance of PVD sensor coatings based on the thermoelectric effect, no standardized methods and procedures are state of the art. In this paper a measuring setup is presented, which allows reference measurements using a calibrated thermocouple and a thermographic camera besides the potential difference measurement of the sensor coating. Two measuring modes, which allow a continuous and a discontinuous measurement, are presented. The measuring methodology was evaluated using the PVD sensor coating Al₂O₃+Ni+NiCr+Al₂O₃. This multilayer sensor coating was deposited using an industrial coating unit and was tested with regard to the sensor properties. The deposition technology used for the sensor coating results in an interface without defects between the two sensor layers with a smooth transition. This provides a suitable electrical contact and a promising compound adhesion. The results show a suitable and detailed measurement of temperature and potential differences by means of calibrated measurement methods and the sensor coating. The measured results are reproducible and show a linear relationship between the potential difference and the surface temperature.

Abstract: In order to study the electrochemical sensor of nanometer mechanism materials to realize the high sensitive detection of different chemical molecules, in this research, the preparation methods of molybdenum dioxide nanomaterials, molybdenum dioxide/metal particles (Au, Pt, Au@Pt) composites and the preparation of molybdenum dioxide nanomaterials, molybdenum dioxide /Au composite nanomaterials, molybdenum dioxide /Pt composite nanomaterials and molybdenum dioxide /Au @Pt composite nanomaterials were introduced. Then the electrochemical behavior of several modified electrodes, electrochemical behavior in catechol system, scanning and pH were applied to the modified electrode. Finally, the electrode p-catechol system was detected by differential pulse voltammetry and the actual samples were analyzed. The results showed that compared with unmodified electrode materials, the electrode modified by molybdenum dioxide nanomaterials, molybdenum dioxide /Au composite nanomaterials, molybdenum dioxide /Pt composite nanomaterials and molybdenum dioxide /Au @Pt composite nanomaterials has better electrocatalytic performance and the detection of catechol has a good effect. Among them, the electrochemical sensor constructed by MoS₂-Au@Pt composite has the best detection performance for catechol. The results have a good guiding significance for the performance improvement of electrochemical sensor.

Abstract: Acetylcholine (ACh) is a main neurotransmitter functioning in smooth muscle and cardiovascular system control. It also plays a key role in memory and learning. While excessive acetylcholine level results in decreased heart rates, depleted level of acetylcholine in human brains can lead to Alzheimer disease. Therefore, detection of acetylcholine is clinically vital. This study aimed at examining potential usage of titanium dioxide (TiO₂) doped with 2.5 mol% Zn as electrochemical sensors for acetylcholine detection. Zn-doped TiO₂ powder was synthesized by a solution combustion technique. Phase identification, microstructural examination, as well as electrocatalytic activity evaluation of the synthesized powder were conducted. The synthesized powder showed anatase phase with fine particle sizes ranging from 9.3 to 11.4 nanometers on average. Specific surface area of 75.48 m²/g was observed. Electrocatalytic activities of the powder in cholin acetate solutions with concentrations ranging from 0.05 to 0.1 μM and 1 to 10 μM were evaluated via cyclic voltammetry technique. At applied voltage of 0.05 V, peak currents corresponding to oxidation reactions between ACh and Zn-doped TiO₂ were detected. Sensitivity values of 3.13x10^-4 and 1.32 μA/(μMmm²), which is in an acceptable range, were evident.

Abstract: Metal oxide semiconductor gas sensors have been widely utilized in a variety of different roles and industries. They are relatively inexpensive, robust, lightweight, long lasting and benefit from high material and quick response time compared to other sensing technologies. However, there are major challenges need to overcame by developers in order to construct a semiconductor metal oxide gas sensor that is efficient, and durable and most importantly can work at lower temperature. Therefore, in this research, TiO₂ dopants was introduced into conventional high purity ZnO gas sensor whereby the samples were prepared in pellet form using powder metallurgy route. The improvement in the mechanical properties as well as the electrical properties of the samples was wished to be observed through this research. The density measurement showed that the adding of TiO₂ was efficient to promote the densification of ZnO sample in which 9 wt% TiO₂ doped ZnO sample showed the highest density. The XRD results showed that the diffraction pattern was basically attributed to the wurtzite structure of ZnO. This was proven by the plane (1 0 1) had the highest intensity in all the samples except 6 wt% TiO₂ and 9 wt% TiO₂ doped ZnO sample. SEM showed that the grain size of ZnO decreased with the addition of TiO₂. This was caused by the formation of the new phase which was Zn₂TiO₄. The smaller the grain size, the higher the specific surface area and oxygen adsorption quantity, and therefore the higher the gas sensitivity is. UV-Vis showed that the wavelength of all samples was located around 380 nm. Therefore, the calculated exitonic energy was around 3.20 eV which was nearly matched with the theoretical band gap of ZnO (3.37 eV). The measurement of the resistivity using four point probe showed that the electrical resistivity of the samples decrease up to addition of 9 wt% TiO₂. This was attributed to increased carrier concentration. Vickers hardness test showed that the doping of TiO₂ had increased the hardness of the sample whereby the 9 wt% TiO₂ doped ZnO sample showed the highest value of hardness. The addition of TiO₂ into high purity ZnO has influenced the mechanical and electrical properties of ZnO. From observing the microstructural and density measurement to the measurement of the surface resistivity as well as the determination of the Vickers hardness value, it was found that 9 wt% TiO₂ doped ZnO was predicted as a candidate for substituting a conventional high purity ZnO as the gas sensor.