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  • Open access
  • 75 Reads
Characterization of hand gestures by a smartphone-based optical fiber force myography sensor

The development of sensors for human-machine interfaces is essential for various applications in robotics, assistive technologies, rehabilitation, and medicine. Gestures recognition has great importance for monitoring and integration with actuators; however, most commercial sensors are expensive and complex, which limits their operation by non-high skilled users. In this context, the force myography technique (FMG), which characterizes the stimuli of forearm muscles in terms of mechanical pressures, emerges as an alternative to the surface electromyography. In this work, an optical fiber sensor based on the FMG technique was proposed for identifying the hand gestures, wherein the interrogation system was integrated into a smartphone to provide a simplified and intuitive user interface. The smartphone flashlight excites a pair of polymer optical fibers coupled with a 3D-printed case, whereas the output signal is detected by the camera. The light intensity is modulated through wearable force-driven microbending transducers placed in the forearm. Subsequently, the acquired optical signals are processed by an algorithm based on decision trees and residual error. The classifier was tested for different thresholds from 3 to 20% of the light intensity signal, and the best results were verified for 8% cutoff limit. Furthermore, the receiver operating characteristic (ROC) curves were plotted for each pattern and generated areas under the ROC curves near the unit. The sensor provided a hit rate of 87% regarding four postures, yielding reliable performance with a simple, portable, and low-cost setup embedded on a smartphone.

  • Open access
  • 91 Reads
Portable label-free amperometric immunosensor based on decorated PVA-co-PE nanofibers for amoxicillin detection in milk
Published: 14 November 2020 by MDPI in 7th International Electronic Conference on Sensors and Applications session Posters

Milk is a highly nutritious food, and it is a source of necessary macro- and micronutrients for the growth, development and maintenance of human health. However, it may also be a source of food contaminants such as mycotoxins, pesticides and antibiotics that may cause disease. Amoxicillin (AMX) is one of the most frequently used lactam antibiotics in the world, the presence of its residues in milk poses a potential risk to public health. FDA and ECC 2377/90 have established the maximum residue limits (MRL) for AMX in milk to be 4 ng ml-1. In recent years, nanofiber technology has opened up new horizons for the development of the biosensor to enhance the sensitivity, selectivity, and detection time. In this work, a novel ultrasensitive label-free electrochemical immunosensor for AMX has been developed. The immunosensor was fabricated by immobilization of anti-AMX on citric acid-grafted-Poly (vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membrane modified screen-printed electrode. PVA-co-PE nanofibrous membrane was prepared by electrospinning technique and characterized by scanning electron microscope (SEM) and the activation step was confirmed by Fourier transform infrared spectroscopy. The employment of PVA-co-PE nanofibers comparing with PVA-co-PE casted membrane and the successful fabrication steps were investigated by electrochemical impedance spectroscopy (EIS). The amperometric response measured at +0.65 V vs. the silver pseudo-reference electrode. Under the optimal conditions, the established immunosensor exhibited high sensitivity for AMX determination in a lower range of 0.009 – 10 ng mL-1 with a determination limit of 7.5 pg mL-1. The proposed immunosensor was evidenced to its applicability for AMX determination in milk samples without pretreatment, showing stability, reusability and good selectivity.

  • Open access
  • 80 Reads
Sons al balcó: Soundscape map of the Confinement in Catalonia

In this study, we aim to study the effect that the lockdown due to the COVID-19 pandemic has caused on the perception of noise in Catalonia. The hypothesis is that the annoyance coming from outdoor noise, minimized by the lockdown, could be associated with better perception of the soundscape by people. The project we have designed allows to validate this hypothesis in two different ways. On the one hand, by means of subjective questionnaires conducted to people living in pre-defined diverse acoustic areas (urban, suburban and rural environments), and on the other hand, by the use of objective measurements of the noise levels , and the study of the soundscape in these areas, by means of short pieces of video collected by citizens. For this purpose, we have designed an on line test to be conducted by any citizen aiming to contribute to this wide study for all the territory of Catalonia, both from rural areas and from cities. A communication campaign was conducted to reach a significant participation. During the lockdown, more than 350 questionnaires and videos were collected, and a first map of the soundscape of the confinement in Catalonia was depicted.

  • Open access
  • 133 Reads
Transfer Printing of Conductive Thin-Films on PDMS with Soluble Substrates for Flexible Biosensors

The resolution of commercially available electrocorticography (ECoG) electrodes is limited due to the large electrode spacing and therefore allows only a limited identification of the active nerve cell area. This paper describes a novel manufacturing process for neural implants with higher spatial resolution combining microtechnological processes and PDMS as flexible, biocompatible material. The conductive electrode structure is deposited on a water-soluble transfer substrate by PVD processes. Subsequently, the structure is contacted. Finally the transfer to PDMS and dissolution of the transfer substrate takes place. In this way, high-resolution conductive structures can be produced on the PDMS. The transferred gold structures exhibit higher adhesion and conductivity than transferred platinum structures. The adhesion can be improved by applying a silica surface modification to the conductive layer prior to transferring. Furthermore, the conductive layer is flexible, conductive up to an elongation of 10% and resistant to sodium chloride solution, which is intended to mimic brain fluids. Using the introduced production process, it is possible to manufacture an ECoG electrode, which was characterized for its functionality in an electrochemical impedance measurement. Furthermore, the electrodes are flexible enough to adapt to different shapes. The transfer process can also be carried out in a 3-dimensional mould to produce electrodes tailored to the individual patient.

  • Open access
  • 96 Reads
Moisture-responsive polymer films on flexible substrates for optical sensing of humidity
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Rapid advances in material science and processing methods over the past decade accelerated the development of flexible and stretchable sensors for various innovative applications in healthcare, medicine, biology and environment. Such devices have the potential to be applied to soft surfaces of different shape like textile fabrics or human skin. Flexible substrates allow continuous roll processing, thus providing the potential for efficient and low cost mass production.

In this paper a flexible humidity sensor is prepared by spin-coating of moisture-sensitive polymer on three types of substrates: poly(ethylene terephthalate) (PET), polylactide (PLA) and composite polysiloxane. The optical properties, surface morphology and roughness of the substrates are studied by transmittance measurements and surface profiling, respectively. Thin spin-coated polymer films of amphiphilic copolymer obtained by partial acetalization of poly(vinyl alcohol) are used as humidity sensitive media. In order to increase the sensitivity a thin metal layer of Au-Pd is incorporated between the polymer film and substrate. The thickness of metal layer is optimized in order the transmittance level of the sensor to be in the range 40-50%. The sensing properties are probed through transmittance measurements at different levels of relative humidity (RH). The influence of substrate type is studied by comparing hysteresis and sensitivity of flexible sensors with those deposited on glass substrate. The successful application of the designed flexible humidity sensors is demonstrated and discussed.

  • Open access
  • 57 Reads
Stator Winding Fault Phase Identification Using Piezoelectric Sensors in Three-Phase Induction Motors.

Three Phase Induction Motors (TIMs) play a key role in industrial production lines. Due to its robustness and versatility, TIMs are commonly used to drive different devices like fans, conveyors, sieves, and compressors. However, these equipment are often exposed to mechanical and electrical faults. Among them, failures in stator winding insulation lead to severe damage to the TIMs and can cause operational interruptions. Therefore, several approaches have been developed to monitor electrical faults in induction motors. The acoustic emission (AE) stands out as an efficient non-destructive technique (NDT) for TIM diagnosis. In this work, the AE analysis was applied to detect winding insulation faults and identify which electrical phase was affected. To achieve this proposal, a TIM was subjected to insulation faults in each of the three electrical phases, and the acoustic signals were acquired by four piezoelectric sensors attached to the motor. These signals were processed using a new technique, which calculates the energy of a specific range of the signal spectrum and assigns the energy values of each piezoelectric sensor to a coordinate axis (x, y). By ploting the values for each fault condition, this technique allows the detection of insulation faults and correctly identifies the affected phase by clustering the resulting values. Finally, the proposed methodology presented satisfactory results in winding insulation diagnosing.

  • Open access
  • 80 Reads
High Frequency Performance of Piezoelectric Diaphragms for Impedance-Based SHM Applications

Piezoelectric transducers are used in a wide variety of applications, including damage detection in structural health monitoring (SHM) applications. Among the various methods for detecting structural damage, the electromechanical impedance (EMI) method is one of the most investigated in recent years. In this method, the transducer is typically excited with low frequency signals up to 500 kHz. However, recent studies have indicated the use of higher frequencies, usually above 1 MHz, for the detection of some types of damage and the monitoring of some structure’s characteristics that are not possible at low frequencies. Therefore, this study investigates the performance of low-cost piezoelectric diaphragms excited with high frequency signals for SHM applications based on the EMI method. Piezoelectric diaphragms have recently been reported in the literature as alternative transducers for the EMI method and, therefore, investigating the performance of these transducers at high frequencies is a relevant subject. Experimental tests were carried out with piezoelectric diaphragms attached to two aluminum bars, obtaining the impedance signatures from diaphragms excited with low and high frequency signals. The analysis was performed using the real part of the impedance signatures and two basic damage indices, one based on the Euclidean norm and the other on the correlation coefficient. The experimental results indicate that piezoelectric diaphragms are feasible for the detection of structural damage at high frequencies, although the sensitivity decreases.

  • Open access
  • 220 Reads
Highly Sensitive Hydrogen Sensor Based on Palladium-Coated Tapered Optical Fiber at Room Temperature

This paper describes the application of a palladium (Pd)-coated tapered optical fiber in order to develop hydrogen (H2) sensor. A transducing channel was fabricated with multimode optical fiber (MMF) with cladding and core diameters of 125 µm and 62.5 µm respectively, to enhance the evanescent field of light propagation through the fiber. The multimode optical fiber was tapered from cladding diameter of 125 µm to waist diameter of 20 µm, waist-length of 10 mm, and down taper and up of 5 mm and coated with Pd using drop-casting technique. In order to establish the palladium’s properties, various characterization techniques were applied such as FESEM, EDX and XRD. The developed palladium sensor functioned reproducibly at a gas concentration of 0.125% to 1.00% H2 at room temperature in the synthetic air. In this case, the response and recovery times were 50 and 200 seconds, respectively. Furthermore, this study demonstrated that the production of a dependable, effective, and reproducible H2 sensor by applying a basic cost-effective method is possible.

  • Open access
  • 85 Reads
Reducing food waste with a tiny CMOS-MEMS gas sensor, dubbed GMOS

The global food losses is one of the most urgent issues for international community today. The fruits and vegetables waste and losses may reach up to 50% of the initial production quantity. Beside the natural waste, the lost food also represents the waste in resources for its production such as water and energy that leads to unnecessary CO2 emissions. The immediate question that arises is, what can be done to reduce such high food losses? And the possible solution is by monitoring of food storage environment. Fruits and vegetables produce ethylene gas during the ripening process, therefore monitoring of ethylene level allows us to determine when the food is edible or ready for marketing before it is spoiled. It seems to be an easy solution, but the problem lies in the ethylene low concentration that should be monitored (0.05 – 10 ppm). Nowadays ethylene can be detected mostly by large, expensive and non-selective detection systems.

In this work, we present a tiny combustion type gas sensor (named GMOS) that is fabricated in standard CMOS-SOI-MEMS technology. It is a low-cost thermal sensor with embedded heater, catalytic layer and suspended transistor as sensing element. The sensor principle relies on a combustion reaction that takes place on the catalytic layer. The heat of chemical reaction releases and leads to sensor temperature increase, which modifies transistor current-voltage characteristics. The sensor performance shows an excellent sensitivity of 40 mV/ppm and selective ethylene detection using nanoparticle catalytic layers of Pt as well as TiO2. Together with low energy consumption, it makes GMOS a promising technology towards low-cost ethylene detection systems for different stages in food supply chain that may reduce the global fruits and vegetables loss and waste.

  • Open access
  • 128 Reads
Wafer Level Packaged CMOS-SOI-MEMS Thermal Sensor at Wide Pressure Range for IoT Applications

Thermal IR sensors are widely used in various fields such as automotive, IoT applications, human intruder alert systems as well as smart building management (lighting, heating) or temperature sensing, with an increasing market forecast for the next years. Technologies currently in use for optical uncooled infrared devices are bolometers, thermopiles, and pyroelectric sensors. More recently, a new generation of uncooled thermal sensor based on CMOS-SOI-MEMS technology has emerged, dubbed “TMOS”.

The TMOS is a suspended, thermally isolated micro-machined floating transistor, which absorbs infrared radiation. The resulting temperature change is transduced into an electric signal. The TMOS operates in the subthreshold region, therefore requiring low power consumption, which is essential for wearable applications. Moreover, the inherent gain of the transistor results in the highest temperature sensitivity, compared to the commercial thermal sensors.

Wafer Level Packaging with a controlled vacuum quality is essential to ensure high performance and low cost. This paper focuses on the study of the thermal performance of a wafer-level packaged TMOS, where the pressure varies between deep high vacuum (0.01 Pa) and atmospheric pressure. The study is based on Finite Element Analysis (FEA) simulations performed by ANSYS software as well as analytical expressions. The measurements of vacuum quality in packaged devices are in line with the modeling and simulations.

The talk will describe the TMOS Wafer Level Packaging as well as the modeling and simulations and how to perform vacuum quality measurements of the packaged MEMS device. The talk will present the innovations and the maturity of the new generation of sensors, which are highly useful for wearable and consumer sensor applications.