Brice Sorli

Quartz Crystal Microbalance (QCM) used as humidity sensor

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.

Porous silicon layer coupled with thermoelectric cooler: a humidity sensor

Abstract In this work, an original humidity sensor is described. It is based on the study of the capacitance variation of a porous silicon layer (PSL) during water condensation induced by a commercial small-size thermoelectric cooler (TEC). The measurement principle is to detect the weak increase of capacitance created when water condensation occurs in a PSL stuck on a TEC. This important variation of capacitance is related to the high difference between the dielectric constant of PS ( e r e r ≅80). The dielectric constant of PS ranges from these of silicon oxide ( e r =3.9) to these of silicon ( e r =12) [H. Mathieu, Physique des semiconducteurs et des composants electroniques, Masson, 1987, p. 36]. Experimental measurements are performed in a climatic chamber for several values of relative humidity from 10% to 95% and for a TEC current equal to 0.43 A for the cooling part of the process. The analysis of the PS capacitance leads to information over the condensation formation during the TEC cooling. A quick increase of the capacitance appears after a delay time, τ , of 0.5–2 s from the start of the TEC cooling. The higher the humidity level, the faster the capacitance increase. It is possible to draw the capacitance reached after 1 s, from the start of the TEC cooling as a function of the relative humidity level.

A Review: Origins of the Dielectric Properties of Proteins and Potential Development as Bio-Sensors

Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i) Defining the origins of the dielectric properties of natural polymers by reviewing proteins. Despite their complex molecular chains, proteins present several points of interest, particularly, their charge content conferring their electrical and dielectric properties; (ii) Identifying factors influencing the dielectric properties of protein films. The effects of vapors and gases such as water vapor, oxygen, carbon dioxide, ammonia and ethanol on the dielectric properties are put forward; (iii) Finally, potential development of protein films as bio-sensors coated on electronic devices for detection of environmental changes particularly humidity or carbon dioxide content in relation with dielectric properties variations are discussed. As the study of the dielectric properties implies imposing an electric field to the material, it was necessary to evaluate the impact of frequency on the polymers and subsequently on their structure. Characterization techniques, on the one hand dielectric spectroscopy devoted for the determination of the glass transition temperature among others, and on the other hand other techniques such as infra-red spectroscopy for structure characterization as a function of moisture content for instance are also introduced.

Toward reliable readers for chipless RFID systems

We report in this paper several techniques to make chipless RFID systems more reliable in order to overcome some drawbacks such as detuning effects, unwanted echoes from the surrounding environment as well as the spurious interferences due to concurrent wireless systems in the ISM bands. As a figure of merit, we show through the implementation of signal processing techniques and by using optimized design that reading a chipless tag on water bottles or on a pack of metallic cans is possible and reliable. Such readings are usually not possible by using conventional designs and systems. The various techniques proposed are tested with the help of simulations, and measurements in a practical indoor environment.

A RFID-enabled sensor platform for pervasive monitoring

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 earths magnetic field when it rotates. Electromagnetic simulations of the tags antenna and practical validations of the motion sensor are presented.

Fabrication of Thermoelectric Sensor and Cooling Devices Based on Elaborated Bismuth-Telluride Alloy Thin Films

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

Pyroelectric LiTaO3 Thin Films Elaborated by RF Magnetron Sputtering on RuO2/SiNx

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.

Feasibility of a Gelatin Temperature Sensor Based on Electrical Capacitance

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.

Thermal sensor using the differential thermal analysis for the detection of relative humidity

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.

Micro‐module Peltier elaborated by flash technique and used as a humidity sensor

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.