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Low power and high switching ratio are the development direction of the next generation of resistive random access memory (RRAM). Previous techniques could not increase the switching ratio while reducing the SET power. Here, we report a method to fabricate low-power and high-switching-ratio RRAM by adjusting the interstice radius (

In this letter, we demonstrate the possibility to design a compact and ultralow power wireless node for environment sensing operating in the UHF band at 868 MHz. The wireless device is based on an ultralow power 8 b microcontroller associated with a digital temperature and relative humidity sensor. It communicates according to the backscattering principle to a software-defined radio (SDR) controlled by a graphical user interface developed in GNU Radio. The wireless node features a power consumption of 5 μA under 1.8 V, which is good enough for communicating data with a packet error rate of 10% at 110 b/s over a range of 30 m in an indoor environment for a transmitting power of 20 dBm. The design of the wireless node and its SDR-based detection system is validated with wireless measurements both in an anechoic chamber and in the indoor environment.

In this article, we present the design and realization of an electronically rewritable RF encoding particle (REP) for chipless RFID applications. This (REP) resonator geometry is integrated with two conductive bridging random access memory (CBRAM) based non-volatile RF switches, and could be electronically programmed using DC pulses to any of possible four resonant states to represent two bits of information. Emerging additive manufacturing (AM) technique based thermal transfer printing is utilized for the realization of this resonator on flexible and low cost Polyethylene terephthalate (PET) substrate. At present the size of the REP is such that five such REPs could be arranged on a standard credit card size tag. Also this REP encodes the most number of bits reported among non-volatile electronically rewritable REPs for chipless RFID applications - 2 bits, till date.

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; In this article we present the concept of a practical approach to realization of a fully passive electronically rewritable chipless RFID tag. Integrated non-volatile and solid state Conductive Bridging Random Access Memory (CBRAM) based Metal-Insulator-Metal (MIM) switches are used to realize the rewritable functionality. A solution to the primary challenge of requirement of obtaining very low ON states resistances (~ < 10 Ω) in case of an RF switch, for efficient operating conditions is addressed in this paper. Here we propose a reconfigurable resonator design with a ground plane, which could operate efficiently for higher ON state resistances (~ > 100 Ω) of a CBRAM/MIM RF switch. A technique of data encoding in electronically rewritable dipole resonators, by effectively modulating the impedance states of integrated CBRAM/MIM switches is presented herewith in detail. This example is presented through a model design of a 3bit rewritable chipless RFID tag.

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.

We report the design of a passive UHF RFID sensor compliant with the EPC Gen2 standard for tilt and temperature monitoring of fragile objects during transportation. The solution is based on the combination of a Farsens Rocky100 IC and a 3-axis accelerometer ADXL362 IC embedding a temperature sensor. The design is validated by simulation, measurement of the reading performance with a dedicated bench, and test of the RFID sensor in practical situations.

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.

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.

Flexible electronics on paper is currently a challenging area of research. The use of an economical and ecological substrate, such as paper, has significant potential compared to a plastic substrate, such as PET (Polyethylene Terephthalate) or Kapton® (Polyimide). However, the roughness and tearing of paper due to moisture and temperature during operation constitute major technical challenges, considering the potential application in electronics. The use of printing techniques, such as gravure, flexographic, screen, offset, inkjet, conductive and dielectric inks, and organic polymers, all of which have different viscosities suitable for machine deposition, may allow to electronic devices on a paper substrate; example products using this technology include flexible batteries, solar cell, displays, and biomedical devices. This technology only presents a small number of disadvantages, which include poor conductivity, expensive materials, and difficulties with subtractive batch processes, such as photolithography and vacuum processes. In this article, the authors chose an unconventional way to reduce the impact of these disadvantages by adapting technological processes of microelectronics (i.e., photolithography, metal vapour deposition, electroplating, and etching) for use on a standard paper substrate.

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.

International audience; This study reports the design and experimental results of a fully-passive solid-state RF switch based on the Conductive Bridging Memory Technology, popularly known as CBRAM. The developed device is a shunt mode RF switch based on a Metal-Insulator-Metal (MIM) structure with Copper-Nafion-Aluminum switching layers on a Coplanar Waveguide (CPW) transmission line, operational in the DC to 3GHz range. DC pulses in the range +12V to-20V are used to operate the switch. The design is initially simulated using the FEM based CST microwave Studio and then realized and validated on a low cost FR4 substrate, and without using any sophisticated clean room technology.

A low-cost passive UHF RFID tag-based sensor is presented. The proposed tag-based sensor comprises a dual-feed patch antenna incorporated with passive sensor and passive RFID chips operating at UHF RFID bands. By introducing the passive sensor (i.e. resistive sensor nodes) in one of the tag antenna feed, low-cost wireless nodes with radio frequency identification and sensing capabilities are implemented. To remotely record the sensed data at any arbitrary distance from the reader, the other feed of the tag antenna is incorporated with only RFID chip and it serves as a reference node. By measuring the difference of the required minimum power transmitted by the reader to wake-up the RFID chips in both the reference and sensor nodes, the reader then can extract the sensed data (i.e. temperature) at the tag location.

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.

The principal motivation of this work is the development and realization of smart cooling and sensors devices based on the elaborated and characterized semiconducting thermoelectric thin film materials. For the first time, the details design of our sensor and the principal results are published. Fabrication and characterization of Bi/Sb/Te (BST) semiconducting thin films have been successfully investigated. The best values of Seebeck coefficient (α(T)) at room temperature for Bi2Te3, and (Bi1−xSbx)2Te3 with x = 0.77 are found to be −220 µV/K and +240 µV/K, respectively. Fabrication and evaluation of performance devices are reported. 2.60°C of cooling of only one Peltier module device for an optimal current of Iopt=2.50 mA is obtained. The values of temperature measured by infrared camera, by simulation, and those measured by the integrated and external thermocouple are reported. A sensitivity of the sensors of 5 mV Torr−1 mW−1 for the pressure sensor has been found with a response time of about 600 ms.

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.

We report a new design and operation of a microelectromechanical systems (MEMS) differential scanning calorimeter (DSC) for heat-capacity measurements. The sensor consists of a 500-nm silicon nitride membrane supported by four bridges on a silicon wafer. On one side of the membrane, a serpentine-shaped platinum layer is deposited and used as both a resistive heater and a thermometer during the DSC measurement. This MEMS design can provide a self-alignment between the DSC cell and the material to be analyzed in order to prevent its deposition on the sloping side walls of the silicon frame. According to FEM calculations, the system exhibits good thermal isolation and high uniformities in the temperature field in the sensing area of the device. To evaluate the use of this calorimetric device for liquid samples, we measure the heat of vaporization of nanoliter-scale water droplets with high preciseness using the calorimeter in both scanning and heat conduction modes.

LiTaO 3 thin films were deposited on RuO 2 electrode by RF magnetron sputtering with a Li 2 O 2 /Ta 2 O 5 (50%–50%) target. This article presents a morphological, structural, dielectric and pyroelectric study of LiTaO 3 thin films. The originality of this work resides on the choice of the substrate: silicon nitride on Si (SiN x /Si) membrane. The final aim is to improve the pyroelectric coefficient for infrared pyroelectric detectors applications. The best pyroelectric coefficient of LiTaO 3 thin films (400 nm) is equal to 60 μC/m 2 K. It was obtained for deposited temperature of 400°C, and a pressure of 10 mTorr.

In this paper we focus on the design of a miniaturized implantable RFID sensor to enable remote identification and sensing for orthopedic prosthesis dedicated to hips and knees. The current issues to overcome in the world of orthopedic surgery are a better tracking of patient's implants integrity during the whole cycle life of the prosthesis. Second, in case the prosthesis should be changed, it would be interesting to have a clear picture of the prosthesis model before the surgical operation to be sure that no surprise arises during the operation. The RFID is a technology which can perfectly match these required key points. A passive RFID tag doesn't need any local battery supply since it harvests energy from the electromagnetic (EM) field of the reader. In its simplest form it is composed of an antenna connected to a chip. The technology involved is shared mainly between HF technologies based on near field communication principle, and UHF technology (867 MHz in Europe). In this paper we study the possibility to design an implant based on UHF RFID tag. Even though, the wireless link losses are higher in human body tissues, the main interest to compare with HF RFID is the higher read range capability (up to several meters) which is more compatible with the aforementioned application for which a detection distance of 50 cm is needed. In order to sense if the prosthesis is properly inserted within the bone, and if it doesn't show any tilt, a pressure sensor is attached to the dedicated RFID IC SL900A from AMS with no additional components as shown in Fig. 1 (a). In order to miniaturize the implant, a ceramic chip antenna operating around 900 MHz is connected to the AMS IC (see Fig. 1 (b)). The whole assembly made of the pressure sensor, the IC and the antenna is coated with PDMS silicon-based resin. This makes a flexible 20×20mm2 RFID-enabled sensor operating at a distance in free space up to 0.6 meter in passive mode as shown in Fig. 1 (c).

For improving sensitivity of nuclear magnetic resonance (NMR) measurements, an in-field preamplifier in a low-cost CMOS process is presented. It is based on a second-generation positive current conveyor (CCII+), with an impedance-matching output stage. The circuit has been designed with optimization of key performances, such as bandwidth, noise, and offset voltage. There have also been precautions taken against potential effect of strong magnetic field under which the circuit should operate. The designed preamplifier has a voltage gain of 15 dB and a bandwidth of 100 MHz. After fabrication of the circuit, we have carried out testing work, including in-field circuit test and characterization of MOS transistors. Under 2-T magnetic field, there have not been substantial changes in overall circuit performances compared to results obtained by post-layout simulations. For an experiment of NMR measurements with and without in-field preamplifier, the circuit is coupled with a receiver micro-coil. The experiment has been to detect protons at 85.13-MHz resonance frequency under 2-T magnetic field with water sample. The obtained results have shown a 14-dB signal-to-noise ratio improvement when the preamplifier is associated with the receiver coil.

In this work an original humidity sensor is described. It is based on the cooled mirror principle with optical detection. The sensor is composed of a reflective sensor and a Peltier module. The thermoelectric cooling allows to reach the dew point and to evaporate the condensate water. The response of the reflective sensor placed opposite to the mirror follows the appearance and evaporation of water condensate mass. The integral of the optical signal variation is proportional to the percentage of relative humidity. Relative humidity measurements are performed in a dew point generator (HUMOR 10) in the range of 80–95% RH, with a high accuracy and an excellent reproducibility. The measurement of the analyzed air is made in 10 s.

International audience

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.

This article describes a new humidity sensor using the technique of differential thermal analysis (DTA). The energy of water vaporisation is estimated via the measurement of the Seebeck voltage of miniature thermocouples used in differential mode on a Peltier module causing condensation from the ambient air. This sensor uses the sensitivity of alloys V2VI3 containing [Bi, Te, Sb, Se], 400‐440μV.K–1. Experimental measurements have been performed in a climatic chamber at constant temperature. The time variation of the differential Seebeck voltage with relative humidities HR varying from 10 to 90 per cent makes it possible to identify with precision the point of water evaporation. For each value of the relative humidity, it is directly a function of the condensate mass. The integration of these curves over time makes it possible to calculate the energy of vaporisation and the condensate mass.

This paper describes an application of Quartz Crystal Microbalance (QCM) used as humidity sensor. Moisture apparition is detected by using a QCM associated with a Peltier module. When water condensation produced by the Peltier cooling appears on the QCM, a change of mass on the crystal sensitive surface results in the decrease of the resonant frequency. If we measure the delay time between the beginning of Peltier supply and the apparition of water condensation on the quartz, we determine the relative humidity and the condensation velocity. A study of thermal transfer is first presented. Relative humidity measurements are then realised in a climatic chamber. A theoretical approach is finally compared with the experimental results.