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We present an electronically rewritable chipless RFID tag based on integrated nonvolatile Conductive Bridging Random Access Memory (CBRAM) RF switches. CBRAM is a nonvolatile memory technology, which is identified as an innovative RF switching solution in this decade. Reconfigurable resonator or RF encoding particle (REP) used in this tag is a closed-loop resonator integrated with two switches each to tune its electrical length, and encodes three states each, to represent more than one bit per REP. Presented tag is composed of three such REPs to represent a total of 27 unique states. This chipless RFID tag with CBRAM switches could be written/rewritten electronically using DC voltage pulses, to encode a desired code from a given combination. Thermal impression transfer printing is utilized for printing metallic layers of the presented chipless tag. Complete fabrication steps of presented tag with integrated CBRAM switches are carried out without any “clean room” processes. An insight to working mechanism of presented rewritable REPs using electrical models is included in this article. Proof of concept of a potential hybrid data encoding technique combining frequency shift coding and Radar Cross Section (RCS) magnitude level coding, through experimental studies, for presented REPs, is also given herewith.

International audience; This paper introduces a flexible UHF RFIDsensor to detect food quality. This sensor is based on aninterdigitated capacity included in a RFID antenna on which isdeposited a layer of vegetal biopolymer. Thus, depending on thefood spoilage, electromagnetic coupling between the capacityand the biopolymer is used to modulate adaptation coefficientbetween chip and antenna of the RFID tag. This study isvalidated by experimental measurements of RFID-sensorexposed to real food gas environment in the process ofdegradation.

International audience; This paper address the advantage and additional functionalities obtained by using integrated nonvolatile nano-ionic conductive bridging metal-insulator-metal (MIM) switches for rewritable chipless RFID applications. Improvement in reliability and ease of fabrication on using Nafion as an ion-conductor for MIM switching applications is discussed. A brief review of devices realized using the proposed technique is given. A novel idea of realization of a shape and frequency rewritable resonator structure for chipless RFID applications is also discussed with the help of full wave electromagnetic simulation studies.

This paper reports the fabrication of capacitive humidity sensors by integrating a graphene oxide sensing layer inside paper substrates. Graphene oxide sheets were self-assembled on the papers’ fibers. A comparative study between several sensors with different concentrations of graphene oxide and different processing times in the graphene oxide suspension is reported. Its aim is to optimize the sensing layer in terms of concentration and thickness towards the fabrication of highly sensitive and porous sensors. The morphology of the fabricated sensors was characterized using scanning electron microscopy, their structure and chemical composition using Raman and infrared spectroscopies. The washability and mechanical strength of the graphene oxide coated paper were tested in water and in an ultrasonic bath. Last, the sensing capabilities of the fabricated devices were tested for a relative humidity ranging from 30% to 90% RH. The optimal sensor is highly porous, hydrophobic and exhibits a good response towards humidity with a low hysteresis. This work presents a low cost alternative for the use of polymers and coated-papers as substrates for flexible electronics. It is also a first step towards the integration of flexible electronics into substrates, which enables the fabrication of highly porous, economical and flexible devices ideal for air flow monitoring, e-dressings and e-textiles.

International audience; In this article, we present the design and results of an electronically re-writable chipless RFID tag on paper substrate. This tag consists of two resonators build around a modified shorted dipole, integrated with a non-volatile Metal-Insulator-Metal (MIM) switch, which tunes the electrical length of each resonator to resonate at two different frequencies, depending on state of the switch. One can electronically reconfigure the tag using low power DC pulses to change its RF signature. The integrated MIM switch has a layer architecture of Silver-Nafion-Aluminum, formed exclusively using an in-house process in ambient laboratory conditions, notably without the use of any 'clean room' facilities. Operating mechanism of the tag is validated with the help of developed electrical equivalent model. This study proves the concept of realizing 'electronically reconfigurable' chipless tags on flexible and low cost substrates, with a fabrication process compatible with mass production.

This review discusses the recent developments of flexible chemiresistive gas sensors, focusing on the main materials and fabrication techniques. This article provides a detailed description of the substrates used in the flexible gas sensing industry. It also highlights the main challenges faced when integrating a sensing layer on paper, textile or polymeric substrates. A detailed study of the sensing materials in terms of structural properties and sensing mechanisms is presented. This study uses examples of gas sensors to explain the sensing mechanisms and to emphasize the functionalization effect on the sensing performance of a material. It also highlights the exceptions in polymers sensing behavior. Since flexible substrates can’t sustain high temperatures, the main techniques used to fabricate flexible gas sensors are explained such as coating, printing, physical vapor deposition, in situ-growth, in situ-polymerization and chemical vapor deposition. The last technique, which requires high temperatures, is mostly used prior to transferring a sensing layer to a flexible substrate. At the end, the main challenges facing the flexible gas sensing technology are pointed out.

We report the design and first results of a reconfigurable RF-encoding particle (REP) for chipless RFID tag, based on a Nafion conductive-bridging random-access memory cell. The developed tag consists of a modified shorted dipole as REP, equipped with a copper–Nafion–aluminum metal–insulator–metal (MIM) nonvolatile ionic-bridging switch. The MIM switch is similar to an RC parallel network, which tunes the electrical length of the resonator. The chipless tags switch between two different resonant frequencies, in the set and reset states of the switch. An electrical model is also developed for the REP to explain the mechanism of switching. The experimental results are in close agreement with the simulation results using commercial electromagnetic simulators. This letter is a proof of concept of electronically reconfigurable chipless tags based on integrated switches which have the potential to be directly printed along with the tag.

International audience; We report a novel fully printed RFID based sensor fabricated on paper substrate. The sensitive material is wheat gluten which is a biopolymer having electrical parameters correlated with relative humidity (RH). The sensor is validated with simulation and measurement results varying climatic conditions.

This letter reports the design and development of a conductive bridging RF switch with simple fabrication steps without the use of any clean room technologies. The reported device is a fully passive shunt mode RF switch on a co-planar waveguide transmission line, which operates in the dc-3GHz range. This particular topology is chosen in contemplation to limitations imposed by the chosen realization process. The device is based on a metal-insulator (electrolyte)-metal structure, with copper- Nafion-aluminum switching layers. S 21 switching between -1 dB (RF-ON) and -16 dB (RF-OFF) is demonstrated till 3 GHz by the device. Dc pulses in the range between 18 V/0.5 mA and -20 V/0.1 A are used, respectively, to SET and RESET the switch, and the instantaneous power consumed for SET and RESET is, respectively, 1.7 μW and 3 mW. The SET and RESET state dc resistances of the switch are observed as 2 Ω and 2 MΩ subsequently. The model is initially simulated using commercial finite element method-based electromagnetic modeling tool and validated experimentally.

The fabrication and the performance of PMMA resistive switching device have been studied by using FR-4 (copper), PMMA (poly methyl methacrylate) and aluminum as the active anode, the solid electrolyte and the inert cathode respectively. By etching the copper surface with the acid solution [4HNO3 + 11H3PO4 (98 %) + 5CH3COOH] at 60 °C for 2 min, a good performance of Cu/PMMA/Al device, which can switch until 2300 cycles, has been realized. The spin rate for forming the PMMA coating plays a decisive role in the performance of Cu/PMMA/Al device. The best performance of the Cu/PMMA/Al device was obtained only when the spin rate of deposition of PMMA reached 4000 rpm (low thickness).

RFID (Radio Frequency Identification) technology has considerably grown in the past few years and is nowadays sought to be implemented for the identification of products and for traceability in the agrifood sector, ensuring food safety and quality. RFID is now considered as the worthy successor of the barcode with a foreseen expansion not only in the agrifood sector, but also in industrial sectors for environmental monitoring (temperature, relative humidity and luminosity) through namely WSN (Wireless Sensor Network) and WST (Wireless Sensor Technology). Research studies are being progressively performed in the objective of coupling sensors to the RFID technology. This interfacing would lead to a better monitoring of packaging headspace by means of the development of different sensors, as well as their coupling to RFID tags through the microchip or directly to the RFID antenna. The present work gives an overview of the basics of the RFID technology, the existing sensors and the ones being developed to be interfaced with the technology, as well as the existing RFID sensor tags. The presented literature studies, mainly in the agrifood sector, demonstrate how RFID may meet our needs for a better monitoring of food quality by coupling radio frequency communication and traceability. The implementation of sensors which is a very new technology being studied and concomitantly developed may lead to a better detection of food degradation markers and thus to a reduction in food loss which is one of the world's major issue.

Nosocomial infections are contracted in a hospital or health care facility. Bacterial cause is the most common in 87% of cases. Studies have been conducted for the detection of these bacteria. The aim of this biosensor is to make an early detection tool, easy to use, reliable, not invasive and low cost. The goal is to detect in real time and simultaneously in a small amount of body fluids such as urine, sweat or saliva, the major bacterial pathogens causing these diseases: Escherichia Coli, Pseudomonas aeroginosa, Acinetobacter baumannii, Staphylococcus aureus and Clostridium difficile.

The use of wheat gluten as sensing material to detect carbon dioxide is a promising approach. The dielectric properties of wheat gluten are modified in contact with carbon dioxide gas at high relative humidity (90%) and at a temperature of 25 °C due to a structural change in the sensing material, where amino groups act as receptors to carbon dioxide molecules. In the present study, the effects of carbon dioxide on the electrical and dielectric properties of wheat gluten at 20% and 90% of relative humidity (usually found in food packaging) are determined and discussed. At 90% of relative humidity, a linear increase of the dielectric permittivity and dielectric loss was observed with a significant hysteresis which increased with the number of carbon dioxide treatment cycles. One of the significant results is the increase in the dielectric permittivity from 7.01 ± 0.07 to 12.02 ± 0.03 with a sensitivity of 31.38 ± 0.06 fF/%CO2 measured at 868 MHz. The developed sensor is sought to be integrated in the design of UHF-RFID (ultra-high frequency − radio frequency identification) systems working at 868 MHz.

An interdigital capacitor (IDC) system was designed in order to provide a controlled high exposure (high surface/thickness ratio) to the environmental atmosphere of a sensing layer of which the dielectric properties were identified by a finite element method simulation and validated using a common parallel plate capacitor technique. The dielectric properties of one of the most sensitive and widely available plant polymers in nature: wheat gluten (WG) proteins were determined at ultra high frequency (500 MHz-1000 MHz) at 25 degrees C and at two different values of relative humidity (RH). Increasing relative humidity from 20% RH to 80% RH increased the dielectric loss and permittivity of wheat gluten from 0.39 +/- 0.01 to 0.84 +/- 0.02 and from 5.01 +/- 0.06 to 7.07 +/- 0.18, respectively. This effect was discussed in the light of wheat gluten composition (constituting amino acids), structure (high molecular weight, proteins unfolding and mobility) and water content (adsorbed water-bonding state). In addition to RH, two other analytes known as food quality markers, carbon dioxide (CO2) and ethanol were studied in terms of sensitivity. The sensitivities of 10.0 +/- 0.4 fF/%RH, 31.38 +/- 0.06 fF/%CO2 and 25.50 +/- 0.05 pF/%ethanol obtained should pave the way for the development of innovative green radio frequency identification (RFID) tags using renewable, cheap and biodegradable plant polymers as gas and vapor sensors. The sensors are intended to be interfaced to low-cost, ultra high frequency, passive, RFID tags for monitoring food quality and freshness volatile markers in packaging headspace.

The innovative use of gelatin as a temperature sensor based on capacitance was studied at a temperature range normally used for meat cooking (20–80 °C). Interdigital electrodes coated by gelatin solution and two sensors of different thicknesses (38 and 125 µm) were studied between 300 MHz and 900 MHz. At 38 µm, the capacitance was adequately measured, but for 125 µm the slope capacitance versus temperature curve decreased before 900 MHz due to the electrothermal breakdown between 60 °C and 80 °C. Thus, for 125 µm, the capacitance was studied applying 600 MHz. Sensitivity at 38 µm at 868 MHz (0.045 pF/°C) was lower than 125 µm at 600 MHz (0.14 pF/°C), influencing the results in the simulation (temperature range versus time) of meat cooking; at 125 µm, the sensitivity was greater, mainly during chilling steps. The potential of gelatin as a temperature sensor was demonstrated, and a balance between thickness and frequency should be considered to increase the sensitivity.

The fabrication process of anodic aluminium oxide (AAO) on a paper-based substrate is challenging because the use of a highly economical, conformable and ecological substrate. This process is based on a simple, cost-effective, self-ordering anodization of aluminium, which yields a vertically aligned and a highly ordered nanoporous structure. The manufacturing process on a flexible substrate with the use of phosphoric acid is described, and a capacitive sensor produced on this layer is investigated versus the humidity concentration and the frequency. The AAO morphology and the structure obtained were analysed, and the electrical properties of the sensing layer were investigated, using a 4192A LF network analyser in a climatic chamber. The surface conduction mechanism and the effect of humidity on the dielectric properties of a porous anodic aluminium oxide are discussed.

This paper studies the implementation of an UHF RFID sensor combining temperature detection with motion detection to improve pallet tracking applications. The aim is to control the integrity of the tagged object during its complete product life (realization, transportation, end-user). It is based on a dedicated IC SL900A from AMS connected to an anisotropic magneto-resistive sensor. The temperature detection is provided by an internal sensor in the IC. The motion is detected by the external magneto-resistive sensor due to the apparent variation of the earth's magnetic field when it rotates. Electromagnetic simulations of the tag's antenna and practical validations of the motion sensor are presented.

PEDOT:PSS is a conductive polymer that is used as electrodes in organic electronic devices, but also in neuronal probes and implantable devices. This material can also be used for building deformable electrodes in soft substrates for several sensing applications. However, this material being sensitive to several chemicals and moisture it is difficult to pattern microstructures using standard lithography techniques. This paper will review and show some techniques developed for patterning PEDOT:PSS thin films using both soft lithography, such as microcontact printing and shadow masking, and conventional lithography techniques. In addition of this review we present a new lithography technique using silicon nitride protection layer and an analysis and comparison of ICP RIE dry plasma etch rates of PEDOT:PSS with different gases.

In this paper, the refractive index, extinction coefficient and optical band gap of xPbO–(1 − x)TiO2 systems are determined by spectroscopic ellipsometry in the spectral range of wavelength 250–850 nm. All films are elaborated by mixed reactive thermal co-evaporation on a SiO2/Si substrate. The Tauc–Lorentz model is used to extract the optical responses and characteristics of the layers. The best values of the fitted parameters are reported. The wavelength-by-wavelength numerical inversion, carried out without considering any fitting parameter, is also represented as another way to derive the optical constants of the layers. The refractive index and the extinction coefficient depend on the PbO content in xPbO–(1 − x)TiO2 systems. The obtained values of the optical band gap are found to change between 2.54 and 3.38 eV. It is demonstrated here that the xPbO–(1 − x)TiO2 systems with the studied compositions have an indirect optical band gap.

In the present work, the design of a micromachined thermal accelerometer based on convection effect was studied. The accelerometer sensitivity and especially the frequency response have been experimentally and numerically studied with low cavity volume. Although this type of sensor has already been intensively examined, few information concerning the frequency response modeling is currently available. In particular, no experimental result about frequency response for low volume and their variation according to the external temperature variation was reported in the literature. In certain particular condition, we assumed that a bandwidth of 120 Hz at −3 dB has been measured. By using numerical resolution of fluid dynamics equations with the computational fluid dynamics (CFD) software package Fluent V6.2 and a simple model based on thermo-conduction, a good accordance with the experimental results has been demonstrated. So, the effects of these two parameters like the volume and the external temperature variation on the thermal accelerometer response have been theoretically, experimentally and numerically investigated.

This paper reports the characterization of lithium tantalite (LiTaO 3 ) thin films deposited by sol gel process. Thin films were deposited on (001) sapphire substrates by spin coating. In order to study the effect of annealing temperature on the structural and optical properties, the films were annealed at several heating temperatures, ranging from 600 to 750 °C. From X-ray diffraction measurements it is confirmed that LiTaO 3 films are highly c -axis oriented, the line width and the intensity of the (006) peak are sensitive to the variation of the annealing temperature and the best results were found at 700 °C. From SEM pictures it is found that the grain size increases from 100 to 200 nm when the annealing temperature is increased to 700 °C. From the optical transmittance and absorbance measurements, the band gap energy was extrapolated at about 4.6 eV which closely agrees with the LiTaO 3 bulk value. Fourier transform infrared (FTIR) reflectivity and Raman backscattering were used as two complementary experiments to probe the zone center optical phonons in the lithium tantalite thin films.

International audience; This paper describes the growth conditions and the structural characterization of thin films PbTiO3 elaborated by a mixed reactive thermal co-evaporation. In a same chamber, in oxygen atmosphere, the titanium source is deposited by electron beam evaporation of TiO2 and the lead source is brought by thermal evaporation of PbO. Crystallographic properties are presented using X-ray diffractometry, morphological aspects are shown by means of electronic and atomic force microscopes (MEB and AFM). The effect of post-annealing on morphology is presented

This paper reports the design, fabrication and preliminary tests of planar microcoils associated with a micromachined channel in silicon. These microcoils are used as nuclear magnetic resonance (NMR) radio frequency detection coils. They allow in vitro NMR analysis of small quantities introduced into the microchannel. It is a real challenging task to develop microsystems for NMR spectrum extraction for smaller and smaller sample volumes. Moreover, it is advantageous that these microsystems could be integrated in a micro total analysing system (µ-TAS) as an analysing stage. In this paper the description, fabrication process and electrical characterization of planar microcoil receivers are described. Results obtained on NMR microspectroscopy experiments have been performed in water and ethanol, using a 500 µm × 500 µm planar microcoil tuned and matched at 85.13 MHz (proton frequency at 2 T).

In this paper, we propose a new way for the determination of aw in fresh and salt meat. The principle is founded on the analysis of a small air volume inside the product. First we describe the fundamental definition of water activity, the state‐of‐the‐art of commercial aw meters, the effects of aw on microbiology in food. In the second step, after a description of the sensor, the principle and the procedure of measurement are explained. The measurements of aw are realized in meat at different stages of drying. Reproducibility and the temperature effect are particularly analyzed.

In this work an original humidity sensor is described. It is based on the study of Seebeck voltage evolution during the water evaporation of a micro‐module Peltier (MMP). The measurement principle is to detect (after cooling) the small temperature decrease created when total water evaporation occurs over the MMP. All the active thin layers of the sensor are made from (Bi2Te3)0.9(Bi2Se3)0.1 (N) films and (Bi2Te3)0.25(Sb2Te3)0.75 (P) films flash evaporated. Experimental measures were performed in a climatic chamber for several values of relative humidity (50 to 90 per cent). The phenomenon (evaporation) appears after a delay time τ. This delay time is the response time of the sensor. Therefore it is possible to draw the evaporation delay time as a function of relative humidity.

International audience; A proof of concept of application of Nano-Ionic Conductive-Bridging Metal-Insulator-Metal (MIM) switches in electronically reconfigurable band stop filters, through design, and experimental results are presented in this article. Two similar designs of band stop filters with different mechanism of operation are proposed herewith. One is a microstrip, resonant open stub based band stop filter and the other is a microstrip tuned shorted stub based band stop filter. Electrical length of the stubs in both these devices are tuned by an integrated MIM switch forcing them to resonate at different frequencies and thus achieving electronically switchable band stop filtering characteristics. Working mechanism of the devices is validated with the help of developed electrical equivalent circuit models. Analysis on time stability of switch states for 1000 minutes with affirmative results is also presented herewith. These devices are fabricated without any soldered electrical components and without the use of any clean room technologies, using proven low cost method, and are promising to work at very-low power and have the potential to be directly printed on low cost flexible substrates like paper, for potential disposable applications.