Ion Georgescu

Surface acoustic wave humidity sensor

Embodiments of the present disclosure include devices and methods for humidity and temperature sensing. For example, in one embodiment, a sensing device can include a first surface acoustic wave (SAW) component, wherein the first SAW component is a temperature component, a second SAW component, wherein the second SAW component is a humidity component, a third SAW component, wherein the third SAW component is a reference component, and a piezoelectric layer, wherein the first SAW component, the second SAW component, and the third SAW component are on a surface of the piezoelectric layer.

Surface Acoustic Wave devices and their sensing capabilities

Since mid 60s, Surface Acoustic Wave (SAW) devices have been using extensively in electronics for telecommunication. However, their potential use in the sensors field is only a matter of recent interest. This paper presents an overview of the sensing mechanisms that allow detection of temperature, strain (for pressure & torque), mass, conductivity (e.g. gas detection) and viscosity by means of SAW based devices. Design and technological challenges are presented, as well as solutions to overcome them in order to obtain reliable devices. The possibility of using such devices as passive wireless sensors is also discussed.

A novel concept for low drift chemical sensing at micro and nano-scale

It is the purpose of this paper to present a novel generic concept for low drift chemical sensing which is applicable at micro and nanometer scale, based on a new, all-differential approach. At micrometer level, our principle is explained by means of surface acoustic wave (SAW) chemical sensing, while at nano level, we are using the resonant sensing principle to develop our genuine differential concept. Unlike the traditional differential approaches based on functionalized sensing layer in the sensing loop, and on a uncoated surface in the reference loop, our all differential concept provides a better response subtraction between the two paths, as the sensing loop consists of a functionalized sensing layer, as before, but, the reference loop consists of a functionalized non-sensing layer, with the same ageing and humidity behavior as the sensing layer. Twinned electronic reading is used for both loops, and thus all the common mode signals are subtracted in the differential reading, assuring the minimum base line drift of the sensor. Preliminary results of all differential sensor response to humidity and temperature variations are shown for the SAW sensors, with the sensor signal kept independent of their changes.

High efficiency coupling devices for guided wave radar-based level sensors

In this work we present novel coupling devices, in terms of feed-throughs and launchers, which are able to increase the efficiency of the electromagnetic power transmission along the propagation chain of guided wave radar (GWR) transmitters for level and interface measurement. The novel concepts are validated by 2D 1COMSOL® axisymmetric simulations which prove that the innovative design improvements are able to increase the electromagnetic efficiency by at least 6 dB. Such novel GWR level transmitters can improve the accuracy and the measurement range of the next generation of GWR level transmitters.

SOI membrane-based pressure sensor in stress sensitive differential amplifier configuration

This paper introduces a pressure sensing structure configured as a stress sensitive differential amplifier (SSDA), built on a Silicon-on-Insulator (SOI) membrane. Theoretical calculation show the significant increase in sensitivity which is expected from the pressure sensors in SSDA configuration compared to the traditional Wheatstone bridge circuit. Preliminary experimental measurements, performed on individual transistors placed on the membrane, exhibit state-the-art sensitivity values (1.45mV/mbar).

Studies for an optimal balancing system for Li ion batteries based on state of health assessment

Li-ion batteries are the most popular energy storage choice for a wide range of applications, especially electric and hybrid electric vehicles, because of their superior characteristics in comparison to the other energy storage technologies. It has been observed that there are significant differences regarding parameters within the same batch of batteries manufactured and that mainly due to technological barriers which cannot be over passed without expensive efforts. To avoid additional stress and battery premature destruction it is necessary to develop a new approach for balancing between cells during electrical or hybrid-electrical vehicles driving cycles. This paper presents a thorough behavioral study of Li-ion cells during the ageing phenomenon, as well as the possibility of employing electrochemical impedance spectroscopy for assessing the batteries state-of-health. The latter can be used to further develop a coherent algorithm to be employed in a smart adaptive balancing system.

Simulation of SAW gas sensors with polymer layers using the finite element method

This paper presents a finite element (FE) model for SAW gas sensors with polymer layers, taking into account not only the mass loading effect, but also the viscoelastic properties of polymer layers, including loss. The FE model considers both variations of layer density and thickness with absorbed gas concentration. The damped eigenvalue analysis allows the calculation of complex propagation constants. This is an improvement over previously published FE works in this field, e.g. [1], which considered only the frequency shift and neglected the attenuation.