Stretchable Printed Device for the Simultaneous Sensing of Temperature and Strain Validated in a Mouse Wound Healing Model

Temperature and strain are two vital parameters that play a significant role in wound diagnosis and healing. As periodic temperature measurements with a custom thermometer or strain measurements with conventional metallic gauges became less feasible for the modern competent health monitoring, individual temperature and strain measurement modalities incorporated into wearables and patches were developed. The proposed research in the article shows the development of a single sensor solution which can simultaneously measure both the above mentioned parameters. This work integrates a thermoelectric principle based temperature measurement approach into wearables, ensuring flexibility and bendability properties without affecting its thermo-generated voltage. The modified thermoelectric material helped to achieve stretchability of the sensor, thanks to its superior mechano-transduction properties. Moreover, the stretch-induced resistance changes become an additional marker for strain measurements so that both the parameters can be measured with the same sensor. Due to the independent measurement parameters (open circuit voltage and sensor resistance ), the sensing model is greatly attractive for measurements without cross-sensitivity. The highly resilient temperature and strain sensor show excellent linearity, repeatability and good sensitivity. Besides, due to the compatibility of the fabrication scheme to low temperature processing of the flexible materials and to mass volume production, printed fabrication methodologies were adopted to realize the sensor. This promises low cost production and a disposable nature (single use) of the sensor patch. The temperature-strain dual parameter semi-transparent sensor has been further tested on mice wounds in vivo. The preliminary experiments on mice wounds offer prospects for developing smart, i.e. sensorized, wound dressings for clinical applications.

GRAPHICAL METHOD FOR DETERMINATION OF MQ-SERIES GAS SENSOR CIRCUIT PARAMETERS FOR A STAND-ALONE GAS ALARM SYSTEM

Background: MQ-series gas sensors belong to the metal oxide semiconductor (MOS) family of sensors that can sense the presence of many gases. These sensors find their application in gas alarm systems as key components. While necessary sensor circuit output voltage value for alarm point in a stand-alone gas alarm system is desirable, but what exact combination of the sensor circuit parameters is required? Hitherto, the determination of these circuit parameters has not been given much attention in the research community. Aim: the purpose of this work is to explore a structured graphical approach of determination of MQ series gas sensor circuit parameters for a stand-alone gas alarm system that yields desired sensor circuit output voltage value for the alarm point; the main objective of the study was to develop mathematical model equations that relate the: (i) sensor resistance (RS) with the gas concentration (x) and the sensor resistance at standard calibration concentration of the sensor base gas in the clean air (Ro) and (ii) sensor circuit output voltage (VRL), load resistance (RL) and sensor resistance (RS). It is expected from the model equations developed that graphical correlations of the sensor circuits parameters will be generated. Using these graphs for a particular case of an MQ-4 gas sensor under the influence of LPG, the parameters that yield desired sensor circuit output voltage of 2V for 1000 ppm of LPG alarm point will be determined. Methods: Model equations were developed for the sensor dynamics, and based on these model equations, graphs for the determination of required sensor parameters were plotted for a case of MQ-4 gas sensor response to LPG. Results and Discussion: The results yielded optimal values for R_O,R_S and R_L of 20 kΩ, 30 kΩ and 20 kΩ respectively, for alarm settings of 1000 ppm and a desired sensor circuit output voltage of 2 V. Based on determined parameters, the calibration equation for determination of best concentration value for a given value of emulated LPG concentration was developed. Using the method proposed in this study makes the process of determining the MQ-series gas sensor circuit parameters less cumbersome as their value can easily be obtained from the resulting graphs. Conclusions: a structured graphical approach for determination of MQ-series gas sensor circuit parameters for alarm points in a stand-alone gas alarm system showed that using MQ-4 gas sensor and LPG as the target gas, and for a sensor circuit output voltage of 2 V for alarm point at 1000 ppm of LPG, the corresponding value of R_O, R_S and R_L obtained were 20 kΩ, 30 kΩ, and 20 kΩ respectively. Hence, a structured graphical approach is suitable for determining MQ series gas sensor circuit parameters for a stand-alone gas alarm system under the influence of its associated gases.

Combinatorial selectivity with an array of phthalocyanines functionalized TiO2/ZnO heterojunction thin film sensors

The development of electronic noses requires the control of the selectivity pattern of each sensor of the array. Organic chemistry offers a manifold of possibilities to this regard but in many cases the chemical sensitivity is not matched with the response of electronic sensor. The combination of organic and inorganic materials is an approach to transfer the chemical sensitivities of the sensor to the measurable electronic signals. In this paper, this approach is demonstrated with a hybrid material made of phthalocyanines and a bilayer structure of ZnO and TiO2. Results show that the whole spectrum of sensitivity of phthalocyanines results in changes of the resistance of the sensor, and even the adsorption of compounds, such as hexane, which cannot change the resistance of pure phthalocyanine layers, elicits changes of the sensor resistance. Furthermore, since phthalocyanines are optically active, the sensitivity in dark and visible light are different. Thus, operating the sensor in dark and light two different signals per sensors can be extracted. As a consequence, an array of 3 sensors made of different phthalocyanines results in a virtual array of six sensors. The sensor array shows a remarkable selectivity respect to a set of test compounds. Principal component analysis scores plot illustrates that hydrogen bond basicity and dispersion interaction are the dominant mechanisms of interaction.

Aerosol Jet Printing of Nickel Oxide Nanoparticle Ink with Ultraviolet Radiation Curing for Thin Film Temperature Sensors

In this study, ultraviolet (UV) radiation curing process and furnace curing process for curing aerosol jet printed nickel oxide (NiO) nanoparticle thin films were investigated. NiO has a negative temperature coefficient and can be used to fabricate temperature sensors. Four UV power settings (for 10 minutes) and four furnace temperatures (for one hour) were used to cure the aerosol jet printed sensors. The resultant sensor resistance at 100°C and 180°C were measured, and the sensor’s sensitivity was characterized by B value. Confocal microscopy was performed to characterize the sensor surface. The 60% UV power setting yields the lowest resistance and the highest B value among all sensors. The analysis of variations shows that the UV power setting is not a significant factor on the resistance and B value, while the furnace temperature is a significant factor. This indicates that UV curing is a more robust method and does not need to be optimized to achieve good results. The UV curing process not only reduces the required curing time but also improve the performance of the temperature sensor.

NORMALIZED PARAMETERS OF A MAGNETORESISTIVE SENSOR IN BRIDGE CIRCUITS

Magnetoresistive sensors are considered as part of bridge circuits for measuring magnetic field strength and electric current value. Normalized or relative expressions are introduced to change the resistance of the sensor and the measured bridge voltage to increase the information content of the regime to provide the possibility of comparing the regimes of different sensors. To justify these expressions, a geometric interpretation of the bridge regimes, which leads to hyperbolic straight line geometry and a cross ratio of four points, is given. Upon a change in the sensor resistance, the bridge regime is quantified by the value of the cross ratio of four samples (three characteristic values and the current or real value) of voltage and resistance. The cross ratio, as a dimensionless value, is taken as a normalized expression for the bridge voltage and sensor resistance. Moreover, the cross ratio value is an invariant for voltage and resistance. The proposed approach considers linear and nonlinear dependences of measured voltage on sensor resistance from general positions.

Internet of Food (IoF), Tailor-Made Metal Oxide Gas Sensors to Support Tea Supply Chain

Tea is the second most consumed beverage, and its aroma, determined by volatile compounds (VOCs) present in leaves or developed during the processing stages, has a great influence on the final quality. The goal of this study is to determine the volatilome of different types of tea to provide a competitive tool in terms of time and costs to recognize and enhance the quality of the product in the food chain. Analyzed samples are representative of the three major types of tea: black, green, and white. VOCs were studied in parallel with different technologies and methods: gas chromatography coupled with mass spectrometer and solid phase microextraction (SPME-GC-MS) and a device called small sensor system, (S3). S3 is made up of tailor-made metal oxide gas sensors, whose operating principle is based on the variation of sensor resistance based on volatiloma exposure. The data obtained were processed through multivariate statistics, showing the full file of the pre-established aim. From the results obtained, it is understood how supportive an innovative technology can be, remotely controllable supported by machine learning (IoF), aimed in the future at increasing food safety along the entire production chain, as an early warning system for possible microbiological or chemical contamination.

Dynamic Characterization of Macrobending Loss Optical Fiber-Based Load Sensor

The weight of vehicles passing through the road greatly affects road damage, so it is necessary to have a non-stop weighing system or Weight in Motion (WIM). In this study, the dynamic characterization of the WIM sensor was carried out based on the principle of optical fiber macrobending. In this study, a single-mode step-index optical fiber was used as the sensor material and a laser diode with a power of 5 mW and a wavelength of 1,550 nm as a light source. Characterization was carried out by running over the sensor using a motor with three variations of speed, namely 10 km/hour, 15 km/hour, and 20 km/hour. Two different conditions were also carried out, namely, the sensor was directly crushed and the sensor was reinforced in the form of a half-cylinder wooden beam. The test was carried out with three different types of sensors. From the observations, data shows that the addition of a beam can increase the accuracy of the reading as seen from the smaller the difference in the output voltage reading for the same type of sensor and vehicle speed. Besides that, there is a strengthening of the sensor resistance up to 10 times which is known from the sensor output voltage where the voltage at the addition of the beam is 1/10 of the reading without the beam. This is due to an increase in the sensor area exposed to the load.

Experimental Complex for Studying the Possibilities of Using Hydroacoustic Sensors in Underwater Vision Systems

A description of a laboratory experimental and measuring complex is given, including a linear aquatic environment in the form of an extended cylindrical reservoir (hydro wave) and an experimental pool equipped with a system for generating test hydroacoustic signals, a set of electroacoustic and acoustoelectric transducers, and a system for amplifying and digitizing received signals. The results of experimental studies of hydroacoustic piezoelectric sensors and the features of the propagation of the waves generated by them in the described laboratory complex are presented. These results include: an assessment of the sensitivity of sensors, an assessment of the frequency characteristics of sensors, a study of the frequency response of a system of two sensors fixed at the ends of a horizontal hydro-wave guide, a comparison of the results of measurements of the frequency response of sensors in a pipe and a pool, a comparison of signal pulling over time in a pipe and a pool, a study of operation sensors in sonar mode. The most significant results illustrating the behavior of hydroacoustic signals and the potential of the measuring complex are the established possibilities for determining the resonance features of electroacoustic transducers and the detail of the characteristics of the reflection of acoustic signals from objects in an aquatic environment. The main investigated characteristics of hydroacoustic sensors are the sensitivity and frequency characteristics of the investigated sensors, the amplitude-frequency characteristics of the system from the transmitting and receiving transducers, and the features of the transducers' operation in the sonar mode. According to the research results, the characteristics of the sensitivity of the sensors and the assessment of the spread of the sensitivity indicators for representatives of the same type of different parties were obtained. The study of the frequency characteristics of the sensors was focused on the study of the dependence of the module and the phase of the sensor resistance on the frequency and on the determination of the resonance characteristics of the sensors. The presence of resonances (resistance minima) and antiresonances (resistance maxima) in several frequency regions was established. When examining the transducers in sonar mode, a glare structure of echo signals from the components of a complex object (a sphere suspended by a thread), separated by time intervals of 12.3 microseconds, was clearly observed. The delay of the signal reflected from the filament in relation to the signal reflected from the front wall of the sphere is due to the distance by two radii of the sphere, covered by the signal reflected from the filament. Carrying out research in two experimental situations (linear hydro wave and experimental pool) allows assessing the degree of adequacy of the results obtained in the sense of comparing similar experiments in different conditions.

Hand Gesture Controlled Robot Arm

Robotic Arms are generally a programmable type of mechanical arm with functions similar to human arm which is either the sum of total mechanism or may be a complex robot part. These robotic arms are employed in assembly line of industries performing complex process like drilling, painting and painting etc. It is possible to fabricate gesture controlled Industrial robot arms. The robot is easily accessible and requires lesser controlling effects. In this work a glove attached to human hand is incorporated with flex sensors and transceiver. The flex sensor resistance can be varied by hand movement which is transferred to the axis of robot. The resistance of glove can make robot rotate either angular or in a linear motion about its axis. A transceiver circuit is employed for signal control which is capable of transmitting and receiving signal between human hand and robotic arm.The flex sensor senses and gives corresponding signals. The analog signal from the flex sensor given to Arduino, it will work according to the Arduino program. The signal is transmitted from Arduino to Zigbee for wireless communication. The driver circuit put together with transistor to control the relay. The relay output is connected directly to motor joined with the robot. With this arrangement arm can be used for pick and place application. The robotic arm delivers the programmed movement and the proposed model have widespread application for people working in hazardous areas.

Lead-Wire-Resistance Compensation Technique Using a Single Zener Diode for Two-Wire Resistance Temperature Detectors (RTDs)

In remote measurement systems, the lead wire resistance of the resistance sensor will produce a large measurement error. In order to ensure the accuracy of remote measurement, a novel lead-wire-resistance compensation technique is proposed, which is suitable for a two-wire resistance temperature detector. By connecting a zener diode in parallel with the resistance temperature detector (RTD) and an interface circuit specially designed for it, the lead-wire-resistance value can be accurately measured by virtue of the constant voltage characteristic of the zener diode when reverse breakdown occurs, and compensation can thereby be made when calculating the resistance of RTD. Through simulation verification and practical circuit testing, when the sensor resistance is in 848–2120 Ω scope and the lead wire resistance is less than 50 Ω, the proposed technology can ensure the measuring error of the sensor resistance within ±1 Ω and the temperature measurement error within ±0.3 °C for RTDs performing 1000 Ω at 0 °C. Therefore, this method is able to accurately compensate the measurement error caused by the lead wire resistance in two-wire RTDsand is suitable for most applications.