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This paper presents a smart sensor patch with flexible strain sensor and a printed temperature sensor integrated with a Near Field Communication (NFC) tag to detect strain or temperature in a semi-quantitative way. The strain sensor is fabricated using conductive polymer poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) in a polymer Polydimethylsiloxane microchannel. The temperature sensor is fabricated by printing silver electrodes and PEDOT:PSS on a flexible polyvinyl chloride (PVC) substrate. A customdeveloped battery-less NFC tag with an LED indicator is used to visually detect the strain or temperature by modulating the LED light intensity. The LED shows maximum brightness for relaxed or no strain condition, and also in the case of maximum temperature. In contrast, the LED is virtually off for the maximum strain condition and for room temperature. Both these could be related to food spoilage. Swollen food packages can be detected with the strain sensor, serving as beacons of microbial contamination. Temperature deviations can result in the growth or survival of food-spoilage bacteria. Based on this, the potential application of the sensor system for smart food packaging is presented.

This article presents a novel approach for using a flexible QR code as a metasurface for sensing and identification functionalities. This is achieved by developing conventional QR code, in part or completely, with functional materials such as thermochromic and photochromic papers. The physical stimuli (e.g., temperature) related colour changes on the QR metasurface were visually detected by the smartphone camera and analysed using a custom app. While the colour variation indicates the physical sensing parameter of the product with which QR code is used, the main QR code itself is used as the product identifier. The marriage of multiple functionalities in the conventional QR code, with no change in the code itself or addition of new sensors, is an attractive approach for attaining more functionality with lesser resources, cost-efficiency and sustainable ICT.

Several studies have shown that the determination of pH in sweat, which is one of the most accessible body fluids, can be an indicator of health and wellness, and even be used for potential disease diagnosis. On that basis, we present herein a wearable wristband for continuous and wireless monitoring of sweat pH with potential applications in the field of personal health assessment. The developed wristband consists of two main parts: a microfluidic cloth analytical device (μCAD) to collect continuously the sweat from skin with a color-based pH sensing area; and a readout and processing module with a digital color sensor to obtain the pH of sweat from the color changes in the μCAD. In addition, the readout module includes a low-power Bluetooth interface to transmit the measurements in real-time to a custom-designed smartphone application. To allow continuous operation, an absorbent pad was included in the design to retire and store thsweat from the sensing area through a passive pump path. It was found that the Hue parameter (H) in the HSV color space can be related to the sweat pH and fitted to a Boltzmann equation (R2 = 0.997). The range of use of the wristband device goes from 6 to 8, which includes the pH range of sweat, with a precision at different pH values from 3.6 to 6.0 %. Considering the typical human sweat rate, the absorbent pad allows continuous operation up to more than 1000 min.

Integration of sensors with antennas is becoming popular for compact high-performance wireless sensing systems. In this direction, here we present a silver electrodes and Poly(3,4-ethylenedioxythiophene:polystyrene (PEDOT:PSS) based printed temperature sensor on a flexible PVC substrate. The temperature sensor was characterised using a digital multimeter for a temperature range from 25¤C to 90□C. The sensor showed a 70% change in resistance for the tested temperature range. Further, the sensing part was integrated with a Near Field Communication (NFC) tag with the data obtained semi-quantitatively by means of the intensity of an Light Emittign Diode (LED) connected with the antenna system. In this case, the antenna works as an energy harvester to power an LED indicator connected in series to the resistive temperature sensor. The intensity of the LED, which varies with the increase of temperature, was measured using a lux-meter mobile application. The intensity at 70□C was ~42 lux whereas it decreased down to ~14 lux at room temperature (~25□C). The presented system showed potential use as a smart label in applications requiring temperature monitoring.

This paper presents a miniaturized potentiostat readout circuit patch developed for electrochemical or biosensors. The presented patch has been fabricated on a flexible polyimide substrate using off-the-shelf electronics. In contrast to the traditional bulky equipment for electrochemical analysis, the presented patch is conformable and portable. As a proof of concept, the system has been used for pH measurements in buffer solution (6- 8 pH values) with a printed thick film potentiometric pH sensor having platinum counter electrode. The obtained results are in line with a commercially available potentiostat that has been used for benchmarking.

In this work we present a polymer-based flexible strain sensor integrated with an NFC tag to detect strain by means of a visual LED indicator. The sensor was fabricated using conductive polymer poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as an active material inside a flexible and transparent polymer Polydimethylsiloxane (PDMS) microchannel. The strain sensor changes its resistance at different bending conditions, showing up to three order increase in resistance for $\sim 100$ bending. A custom-developed passive NFC tag with an LED connected in series to the strain sensor is powered from an NFC reader to detect strain in a semi-quantitative way. The light intensity of the LED indicator is modulated according to the strain level, showing maximum brightness $(\sim 67$ lux) for relaxed or no strain condition, and being almost OFF $(\sim 8$ lux) for the maximum strain condition. The potential application of the NFC-based strain sensor system in food package for spoilage detection is also presented.

This work was supported in part by the Spanish Research and Development National Program under Project TIN2016-75097P and Project RTI2018-102002-A-I00, in part by "Junta de Andalucia" under Project B-TIC-402-UGR18 and Project P18.RT.4830, and in part by the Predoctoral Grant FPU18/01965., In this brief, we present a low-loss mechanically reconfigurable phase shifter implemented in gap-waveguide technology for mm-wave frequencies. The proposed design gives a practical implementation of tuning elements inside the waveguide providing alternatives to the use of the E-plane split waveguide at high frequencies in order to avoid leakage losses. The depicted phase shifter design is based on a H-plane split waveguide. The phase shift is controlled by means of a tuning screw, which exerts pressure on a flexible metallic strip inserted inside the waveguide. The flexible strip bends with different curvature radii and determines the phase shift at the output port. Cost-effective manufacturing and simple implementation of the flexible metallic strip are achieved by means of the gap-waveguide design. A prototype has been manufactured for validation purposes. Good impedance matching is achieved from 64 GHz to 75 GHz providing a 15.8% impedance bandwidth. The results show a maximum phase shift of 250° with a maximum and mean insertion loss (IL) of 3 dB and 1.7 dB, respectively., Spanish Research and Development National Program TIN2016-75097P RTI2018-102002-A-I00, Junta de Andalucia B-TIC-402-UGR18 P18.RT.4830, FPU18/01965

A smartphone-based platform for the diagnosis of parasitic infections has been developed, tested and validated. The system is capable of making automatic and accurate analysis of millimetric colorimetric arrays in centrifuge collection tubes, which are well established tools used in clinical analysis. To that end, an Android-based software application has been developed, making use of the smartphone rear camera, enabling precise image processing of the colorimetric spot arrays. A low-cost plastic accessory has been developed using 3D-printing to provide controlled illumination, xed sample positioning and cell phone attachment. The platform was then tested repeatedly for its size detection, edge blurriness and colour detection capabilities. A minimum spot radius of 175 m is detectable when using the developed app, with a tolerance of 15%, corresponding to 0.25%of the area where the spot array is printed. Spot edge de nition has been studied up to 40% of blurriness, resulting in a low average percentage error of 1.24%. Colour detection follows the well-known Gamma correction function. Finally, the whole platform was tested and validated using real DNA to analyse for accurate discrimination of Trypanosomatid species, which are responsible for devastating diseases in humans and livestock. The smartphone-based platform can be further extended to other clinical analysis. Its simplicity and reliable performance mean it can be used in remote, limited-resource settings by relatively unskilled technicians/nurses, where diagnostic laboratories are sparsely distributed. The results can however be sent easily via the smartphone to medical experts as well as government health agencies., This work was supported in part by the Spanish Ministry of Economics and Competitivity under Project CTQ2016-78754-C2-1-R, in part by the European Regional Development Fund (ERDF), and in part by the DestiNA Genomica SL provided reagents, samples and Spin-Tube devices. The work of P. Escobedo was supported by the Spanish Ministry of Education, Culture and Sport (MECD), under Grant (FPU13/05032).

In this paper we present the design, fabrication and characterization of electro-textile inductor and capacitor patterns on denim fabric as a basis for the development of wearable e-textiles. Planar coil inductors have been harnessed as antenna structures for the development of near field communication tags with temperature sensing capability, while interdigitated electrode capacitors have been used as humidity sensors for wearable applications. The effect of bending in the electrical performance of such structures was evaluated, showing variations below 5% in both inductance and capacitance values for bending angles in the range of interest; that is, those fitting to human limbs. In the case of the fabricated near field communication tags, a shift in the resonance frequency below 1.7% was found, meaning that the e-textile tag would still be readable by a near field communication-enabled smartphone. In respect of the capacitive humidity sensor, we obtained a minimum capacitance variation of 40% for a relative humidity range from 10% to 90%. Measured thermal shift was below 5% in the range from 10 to 40℃. When compared with the 4% variation due to bending, it can be concluded that this capacitive structure can be harnessed as a humidity sensor even under bending strain conditions and moderate temperature variations. The development and characterization of such structures on denim fabrics, which is one of the most popular fabrics for everyday clothing, combined with the additional advantage of affordable and easy fabrication methodologies, means a further step towards the next generation of smart e-textile products.

The development of a contactless readout system for High Frequency (HF) tags and its application to relative humidity monitoring is presented. The system consists of a Colpitts oscillator circuit whose frequency response is determined by a built-in logic counter of a microcontroller unit. The novel readout strategy is based on the frequency response change due to the inductive coupling between the coil of the Colpitts oscillator and the load impedance of a parallel LC resonator tag, as a result of the variation of the humidity sensing capacitor. The frequency is monitored with a low cost microcontroller, resulting in a simple readout circuit. This passive LC tag has been directly screen-printed on a humidity-sensitive flexible substrate. The readout circuit experimental uncertainty as frequency meter was 4 kHz in the HF band. A linear temperature drift of (-1.52 ± 0.17) kHz/⁰C was obtained, which can be used to apply thermal compensation if required. The readout system has been validated as a proof of concept for humidity measurement, obtaining a significant change of about 260 kHz in the resonance frequency of the Colpitts oscillator when relative humidity varies from 10% to 90%, with a maximum uncertainty of ±3% (±2 SD). Therefore, the proposed readout system stands as a compact, low-cost, contactless solution for chipless HF tags that avoids the use of bulky and costly equipment for the analog reading of wireless passive LC sensors., This work was supported by project CTQ2016-78754-C2-1-R from the Spanish Ministry of Economics and Competitivity. P. Escobedo wants to thank the Spanish Ministry of Education, Culture and Sport (MECD) for a pre-doctoral grant (FPU13/05032).

The authors would like to acknowledge to the staff of the Hospital Universitario Clínico San Cecilio, Granada, Spain, for their support and use of the facilities. We also thank the reviewers for their useful and constructive comments and suggestions which have improved this paper., Safe quality control of radiotherapy treatments lies in reliable dosimetric sensors. Currently, ionization chambers and solid-state diodes along with electrometers as readout systems are accomplishing this task. In this work, we present a well-known and low-cost semiconductor sensor, the light-dependent resistor (LDR), as an alternative to the existing sensing devices for dosimetry. To demonstrate this, a complete characterization of the response to radiation of commercial LDRs has been conducted in terms of sensitivity, reproducibility and thermal correction under different bias voltages. Irradiation sessions have been applied under the common conditions in radiotherapy treatments using a hospital linear accelerator. Moreover, the same electrometer used for the ionization chamber has also been successfully used for LDRs. In comparison with the sensitivity achieved for the ionization chamber (0.2 nC/cGy at 400 V bias voltage), higher sensitivities have been measured for the proposed LDRs, ranging from 0.24 to 1.04 nC/cGy at bias voltages from 30 to 150 V, with a reproducibility uncertainty among samples of around 10%. In addition, LDR temperature dependence has been properly modeled using the simple thermistor model so that an easy thermal drift correction of dose measurements can be applied. Therefore, experimental results show that LDRs can be a reliable alternative to dosimetric sensors with the advantages of low size, affordable cost and the fact that it could be adopted with minimal changes in routine dosimetry quality control since the same readout system is fully compatible., Junta de Andalucía B-TIC-468-UGR18 PI-0505-2017, European Union (EU)

A portable device based on a colorimetric sensor to determine the atmospheric level of CO2 gas is presented in this work. The system is based on a low-cost, low-power System on a Chip (SoC) microcontroller with integrated Wi-Fi. A user-friendly application was developed to monitor and log the CO2 measurements when the system is connected to a Wi-Fi network. The sensing membrane is directly deposited on the surface of the colour detector, thus reducing the complexity of the system. This sensing membrane is formed by a pH indicator α-naphtholphthalein, tetramethylammonium hydroxide pentahydrate, 1-ethyl-3-methylimidazolium tetrafluoroborate, Tween 20 and hydroxypropyl methylcellulose as the hydrophilic polymer. The system has been fully characterized, obtaining response and recovery times of 1.3 and 2.5 s, respectively, a limit of detection of 51 ppm, and an average resolution of 6.3 ppm. This portable device was applied for the in-situ determination of CO2 gas in the atmosphere inside classrooms in several secondary schools. The measurements were taken during complete workdays and the results were statistically compared with the same measurements taken using a commercially available non-dispersive infra-red (NDIR) device. No significant statistical differences were found between the results obtained using both devices. A complete statistical treatment of the measurements made with the proposed portable device was carried out. The obtained results show that the concentration of CO2 gas in some schools was higher than the desired concentration, with regard to influencing the student's health, safety, productivity and comfort. This demonstrates the need to control this parameter to ensure appropriate indoor environmental quality (IEQ).

In this work we present a novel technique to estimate the resonance frequency of LC chipless tags (inductor-capacitor parallel circuit) with improved sensitivity and linearity. The developed reader measures the power consumption of a Colpitts oscillator during a frequency sweep. The readout circuit consists of a Colpitts oscillator with a coil antenna, varactor diodes to change the oscillator frequency, analog circuitry to measure the power consumption and a microcontroller to control the whole system and send the data to a PC via USB. When an LC tag is inductively coupled to the oscillator, without contact, a maximum power peak is found. As shown by an experimental calibration using an LC tag made on FR4 substrate, the frequency of this maximum is related to the resonance frequency. Both parameters, power consumption and resonance frequency, present an excellent linear dependence with a high correlation factor (R 2 = 0.995). Finally, a screen-printed LC tag has been fabricated and used as relative humidity sensor achieving a sensitivity of (−2.41 ± 0.21) kHz/% with an R 2 of 0.946.

Electronic skin (eSkin) with various types of sensors over large conformable substrates has received considerable interest in robotics. The continuous operation of large number of sensors and the readout electronics make it challenging to meet the energy requirements of eSkin. In this article, we present the first energy generating eSkin with intrinsic tactile sensing without any touch sensor. The eSkin comprises a distributed array of miniaturized solar cells and infrared light emitting diodes (IRLEDs) on soft elastomeric substrate. By innovatively reading the variations in the energy output of the solar cells and IRLEDs, the eSkin could sense multiple parameters (proximity, object location, edge detection, etc.). As a proof of concept, the eSkin has been attached to a 3-D-printed hand. With an energy surplus of 383.6 mW from the palm area alone, the eSkin could generate more than 100 W if present over the whole body (area ∼1.5 m2). Further, with an industrial robot arm, the presented eSkin is shown to enable safe human−robot interaction. The novel paradigm presented in this article for the development of a flexible eSkin extends the application of solar cell from energy generation alone to simultaneously acting as touch sensors.

This communication presents the design of a two-port electronically tunable phase shifter at K band. The phase shifter consists of a 3 dB hybrid coupler loaded with reflective phase-controllable circuits. The reflective circuits are formed by varactors and non-sequential impedance transformers which increase the operational bandwidth and the provided phase shift. The final phase shifter design is formed by two loaded-coupler stages of phase shifting to guarantee a complete phase turn. An 18 GHz phase shifter design with dynamic range of 600 degrees of phase shift is depicted in this document. The prototype is manufactured and validated through measurements showing good agreement with the simulation results., This work has been partially supported by the TIN2016-75097-P, RTI2018-102002-A-I00, and EQC2018- 004988-P projects of the Spanish National Program of Research, Development, and Innovation and project B-TIC-402-UGR18 of Junta de Andalucía

In this work we describe a passive screen printed flexible tag for gas monitoring that can be used in sealed environments. The developed measurement system is based on chemical sensors that are sensitive to gases concentration presenting optical response, luminescent or colourimetric. The measuring electronics consist of a LED for optical excitation of the sensing membrane and a high resolution digital colour detector for the reading of the optical signal. A microcontroller receives and processes the data enabling the detection threshold for the corresponding gas. The whole system is powered by two miniaturized solar cells that provide 4 V and up to 250 μA each one. This system can run in sunlight or using a bright artificial light as the only energy source. The information of the inner environmental conditions regarding the gas concentration is transmitted to the user through a simple optical code using colour light-emitting diodes. These LEDs are activated to indicate whether the concentration of the monitored gas is within the expected limits, or not. Two prototypes based on this architecture and only changing the sensing module have been developed and applied for the determination of two common gases: oxygen and carbon dioxide. In the first case, a luminescent chemical sensor is used while in the second, the sensing membrane presents a colourimetric response. Both types of sensors can be used in this design. Resulting limits of detection are compatible with assessment of modified atmosphere packaging.

Here, we present a technique for the determination of the gaseous oxygen concentration 2 inside packed food. It is based on the use of a luminescent membrane sensitive to O2 that is optically excited and read by a smartphone. The flash of the smartphone along with an optical filter is used as the light source for the optical stimulation of the membrane. The luminescence generated, which is quenched by the surrounding gaseous oxygen, is registered by the rear camera of the same device. The response parameter is defined by combining the registered intensities at two different wavelength ranges corresponding to the emission and the absorption peaks of the sensitive membrane. Thanks to this novel response parameter, the sensitivity is increased and, more importantly, the thermal dependence of the membrane is significantly reduced. This approach allows the use of a luminescent O2-sensitive membrane for intelligent packaging with no need of any associated electronics for its excitation and reading. This means that an oxygen sensor is developed, where a luminescent compound acts as an indicator, therefore combining the advantages of both schemes, that is, the simplicity and reduced cost of indicators with the high sensitivity and accuracy of selective sensors., This work was supported by the Spanish Ministry of Economics and Competivity through the Project CTQ2016-78754-C2-1-R. The work P. Escobedo Araque was supported by the Spanish Ministry of Education, Culture and Sport under Grant FPU13/05032. The work of I. Pérez de Vargas-Sansalvador was supported in part by the European Union’s Horizon 2020 Research and Innovation Program (Multisens) under Grant 706303, in part by the Talentia Postdoc Program launched by the Andalusian Knowledge Agency, in part by the European Union’s Seventh Framework Program, in part by the Marie Skłodowska-Curie actions (COFUND) under Grant 267226, and in part by the Ministry of Economy, Innovation, Science and Employment of the Junta de Andalucía.

The authors acknowledge the Servicio de Radiofísica (Radio-physics Service) of the Hospital Universitario San Cecilio (Granada, Spain) for permitting us to use their installations. This work was funded by the Spanish Government under project FPA2015-67694-P (Spanish Ministry of Economy, Industry and Competitiveness) and a R&D predoctoral grant (FPU13/05032, Spanish Ministry of Education, Culture and Sport). This project is partially supported by European Regional Development Funds (ERDF)., In this work we describe and evaluate a dosimetric system based on an NFC (Near Field Communication) tag and a smartphone that uses commercial MOSFETs as radiation sensors. The tag is designed with commercial integrated circuits and the smartphone is the power source of the tag configured as a readout unit, user interface and storage unit. The NFC tag is supplied wirelessly by the smartphone via NFC, using a home-made structure to align the tag coil and smartphone coil in order to achieve a good inductive coupling. In this case, the commercial DMOS transistor ZVP3306 is used as dosimeter in unbiased mode, connected to the tag before and after each irradiation session to perform the sensor reading. An evaluation of the dosimetric system has been carried out irradiating three transistors with photon beam of 6 MV up to 20 Gy. The average sensitivity found is (4.75 ± 0.15) mV/Gy, which is in good agreement with the results found with our previously developed dosimetric system. Therefore, this miniaturised dosimetric system can be considered as a promising and low cost electronic architecture to be used for dosimetry control in radio-therapy treatments., Servicio de Radiofísica (Radio-physics Service) of the Hospital Universitario San Cecilio (Granada, Spain), Spanish Government under project FPA2015-67694-P (Spanish Ministry of Economy, Industry and Competitiveness) and a R&D predoctoral grant (FPU13/05032, Spanish Ministry of Education, Culture and Sport), European Regional Development Funds (ERDF)

In this work we present a full-passive flexible multigas sensing tag for the determination of oxygen, carbon dioxide, ammonia, and relative humidity readable by a smartphone. This tag is based on near field communication (NFC) technology for energy harvesting and data transmission to a smartphone. The gas sensors show an optic response that is read through high-resolution digital color detectors. A white LED is used as the common optical excitation source for all the sensors. Only a reduced electronics with very low power consumption is required for the reading of the optical responses and data transmission to a remote user. An application for the Android operating system has been developed for the power supplying and data reception from the tag. The responses of the sensors have been calibrated and fitted to simple functions, allowing a fast prediction of the gases concentration. Cross-sensitivity has also been evaluated, finding that in most of the cases it is negligible or easily correctable using the rest of the readings. The election of the target gases has been due to their importance in the monitoring of modified atmosphere packaging. The resolutions and limits of detection measured are suitable for such kinds of applications.

This work presents the design, fabrication, and characterization of a passive printed radiofrequency identification tag in the ultra-high-frequency band with multiple optical sensing capabilities. This tag includes five photodiodes to cover a wide spectral range from near-infrared to visible and ultraviolet spectral regions. The tag antenna and circuit connections have been screen-printed on a flexible polymeric substrate. An ultra-low-power microcontroller-based switch has been included to measure the five magnitudes issuing from the optical sensors, providing a spectral fingerprint of the incident electromagnetic radiation from ultraviolet to infrared, without requiring energy from a battery. The normalization procedure has been designed applying illuminants, and the entire system was tested by measuring cards from a colour chart and sensing fruit ripening.

This work presents the design, fabrication and characterization of a fully passive radiofrequency identification tag in the ultra-high frequency band with multiple optical sensing capabilities. This tag includes five photodiodes to cover a wide spectral range from near infrared to visible and ultraviolet spectral regions. A microcontroller based switch has been implemented to measure in the same access the five magnitudes coming from the optical sensors, providing a spectral fingerprint of the incident electromagnetic radiation.

When component-based systems are large and complex, one faces systems of systems, where interactions are mostly data-information flows. Examples include transport systems. A major issue in the production of such systems is the so-called emergent behaviors. These behaviors are more likely to appear within a bottom-up approach, where components are first produced and then gathered together to form the targeted system. The alternative approach is a top-down one: the system is specified as a whole in an abstract manner, and then individual components are built in away that their assemblage satisfies the system requirements. Therefore, by construction, emergence is better mastered because the system behaviors are specified a priori. In the scope of a top-down approach, we present an incremental testing framework, where the system requirements, involving timing constraints, are specified operationally as UML MARTE sequence diagrams. We use symbolic techniques to analyze the requirements and deduce unitary test cases for components integrating the system. We apply our approach on a railway use case.

Orchestrations are systems deployed on the Internet where there is a central component (called orchestrator) coordinating other components (called Web services), pre-existing to the orchestration design phase. Web services are made available through repositories on the Internet to orchestration designers. Service discovery refers to the activity of identifying Web services offered by third parties. We propose an approach to discover Web services by taking into account the intended behaviors of Web services as they can be inferred from the orchestrator specifications. Web services are tested with respect to those behaviors to decide whether or not they can be selected. Specifications of orchestrators are Timed Input/Output Symbolic Transition Systems. Web service intended behaviors are elicited by means of symbolic execution and projection techniques. Those behaviors can be used as test purposes for our timed symbolic conformance testing algorithm.

International audience; We propose a model-based black-box testing approach to test conformance of Web Service Compositions (WSC). When a WSC under test makes use of implementations of Web Services, two situations may occur: either communications between the WSC and the Web Services are observable or hidden internal actions. We show by means of an example how to generate test cases whose verdicts are provided with explanations taking into account the status of the Web Services

The IMS Learning Design specification aims at capturing the complete learning flow of courses, without being restricted to a particular pedagogical model. Such flow description for a course, called a Unit of Learning, must be able to be reproduced in different systems using a so called run-time environment. In the last few years there has been several tools implementing such functionality, but most of them are standalone and do not benefit from the integration with a Learning Management System. This paper describes GRAIL, an IMS Learning Design run-time environment supporting all three levels of the specification and fully integrated with the .LRN Learning Management System. The paper describes its functionality, explains how each level is implemented, shows the differences with other CopperCore based environments, and analyzes its integration with the rest of .LRN services and other specifications such as QTI and SCORM. Editors: Daniel Burgos.

In this paper, we present a passive tag for the determination of gaseous oxygen in intelligent packaging (IP). The power supply for this tag is obtained from thermoelectric energy harvesting taking advantage of the temperature difference between a cooled package and the human body. For this purpose, a compact Peltier module is attached to the surface of the package. This device is able to generate 1.2 mW when a temperature difference of 25 °C is applied between its surfaces. A dc-to-dc boost converter is included to generate an output voltage of 3.3 V and an output current of $225~\mu \text{A}$ from the harvested energy by the Peltier cell, which are used to supply the measurement circuitry. A luminescent membrane sensitive to oxygen is used as a gas detector in the package. The generated signal is compared to a reference value to evaluate if the oxygen concentration inside the package falls below or above a predetermined value. This is shown by turning on a green or a red LED, respectively. The proposed system presents a resolution of 0.02% of the predicted oxygen concentration in the range of interest (0%–5%) and a limit of detection (LOD) of 0.007%, which makes the instrument appropriate to be used in IP and active packaging (AP) technology.