Mustapha Nadi

Geometric parameters optimization of planar interdigitated electrodes for bioimpedance spectroscopy

Abstract This paper is concerned with a physical model of an interdigitated sensor working in a frequency range from 100 Hz to 10 MHz. A theoretical approach is proposed to optimize the use of the sensor for bioimpedance spectroscopy. The correlation between design parameters and frequency behavior in coplanar impedance sensors are described. CoventorWare® software was used to model the biological medium loaded interdigital sensor in three dimensions to measure its electrical impedance. Complete system simulation by a finite element method (FEM) was used for sensor sensitivity optimization. The influence of geometrical parameters (number of fingers, width of the electrodes) on the impedance spectroscopy of the biological medium was studied. The simulation results are in agreement with the theoretical equations of optimization. Thus, it is possible to design a priori such sensor by taking into account the biological medium of interest that will load the sensor.

Harmonic propagation of finite amplitude sound beams: comparative method in pulse echo measurement of nonlinear B/A parameter

This article presents an original method of B/A measurement with a single plane transducer used in pulse-echo mode. To determine the best conditions of measurement, we use an ideal model with a new solution for the second harmonic. We take into account the phenomena of attenuation and diffraction. Experiments validate simulations in the case of comparative method measurement. Then we present a device to improve the detection of the second harmonic. Thus measurement of the B/A parameter of ethanol and glycerol validates this device and we also show the possibility of its use in nonlinear imaging with a weak excitation.

Harmonic propagation of finite-amplitude sound beams : second harmonic imaging in ultrasonic reflection tomography

In biomedical ultrasound imaging, many studies show the advantages of harmonics to obtain a better quality of image; this is particularly true in echography and diffraction tomography. Recent work confirms that lateral resolution can be improved by the use of the harmonics generated by a nonlinear distortion in the medium. In this study, the enhancement made by the use of the second harmonic in ultrasound reflection tomography is shown. A focused transducer containing both concentric 2.5 and 5 MHz elements composes the experimental device. They are, respectively, the transmitter/receiver of the fundamental field and the receiver of the second harmonic field. The tests are carried out with PVC tubes. The first object is a single tube whereas the second one is an asymmetrical structure made up of two tubes. The image reconstruction is made from the measurements of the fundamental and second harmonics of the reflected fields using the back-projection method. This technique of relying on higher harmonics seems to provide a better resolution of tomographic images.

Ultrasonic Piezoceramic Transducer Modeling With VHDL-AMS: Application to Ultrasound Nonlinear Parameter Simulations

This paper presents an ultrasonic transducer modeling with very high-speed integrated circuit (VHSIC) hardware description language-analog and mixed signal (VHDL-AMS) IEEE 1076.1 integrated in a global measurement cell modeling dedicated to biological tissue ultrasound characterization. Usual modeling of ultrasonic transducers is based on electrical analogy and is not simulated in the global measurement environment. The ultrasonic transducer modeling proposed is simulated with a nonlinear acoustic load and electronic excitation. The nonlinear B/A parameter is used to characterize a medium with a comparative method. The measurement cell is composed of two piezoelectric ceramic transducers, which are implemented with Redwoods electric scheme. The analyzed medium is placed between the transducers and modeled to take into account the nonlinear propagation with the B/A parameter. The usual transmission line model has been modified to take into account the nonlinear propagation for a one-dimensional (1-D) wave. Simulations of the transducer pulse response and electrical impedance show a VHDL-AMS model that is in good agreement with measurement and compared to the usual personal computer simulation program with integrated circuit emphasis results simulations. Results obtained by simulation of mediums (blood, milk, liver, and human fat tissue) showed good agreement between modeling and experimental measurement, and a maximum error of about 12.5% for B/A measurement-simulation

Design and Realization of a Planar Interdigital Microsensor for Biological Medium Characterization

In this work, we present the design of a planar interdigital microsensor for the characterization of biological mediums by impedance spectroscopy. We propose a theoretical optimization of the geometrical parameters of this sensor. The optimization allows to extend the measurement frequency range by reducing the polarization effect which is manifested by a double layer (DL). We present also a new method for a planar interdigital transducer to determine the parameters (relative permittivity, capacitance) of the double layer (DL) on the surface of the electrode loaded by a biological medium. The CoventorWare® software was used to simulate the model design of interdigital transducer in three dimensions (3D). The simulation results are coherent with the method proposed. Therefore, this method can be used to determine the parameters of double layers of a planar interdigital sensor in order to match its frequency band to the intented application.

Computation of Pacemakers Immunity to 50 Hz Electric Field: Induced Voltages 10 Times Greater in Unipolar Than in Bipolar Detection Mode

Thisstudy aims to compute 50 Hz electric field interferences on pacemakers for diverse lead configurations and implantation positions. Induced phenomena in a surface-based virtual human model (standing male grounded with arms closed, 2 mm resolution) are computed for vertical exposure using CST EM® 3D software, with and without an implanted pacemaker. Induced interference voltages occurring on the pacemaker during exposure are computed and the results are discussed. The bipolar mode covers 99% of the implanted pacing leads in the USA and Europe, according to statistics. The tip-to-ring distance of a lead may influence up to 46% of the induced voltage. In bipolar sensing mode, right ventricle implantation has a 41% higher induced voltage than right atrium implantation. The induced voltage is in average 10 times greater in unipolar mode than in bipolar mode, when implanted in the right atrium or right ventricle. The electric field threshold of interference for a bipolar sensing mode in the worst case setting is 7.24 kV·m−1, and 10 times higher for nominal settings. These calculations will be completed by an in vitro study.

Analysis Sensitivity by Novel Needle-Type GMR Sensor Used in Biomedical Investigation

We have attempted to characterize the new needle-type probe giant magnetoresistance (GMR) as a magnetic micro biosensor. The sensitivity of this sensor has been determined. The high sensitivity of GMR sensor has a good ability to estimate magnetic fluid particles (in low concentrations) and to detect the micro or nano magnetic markers in bio-medical application.

Four electrode embedded bioimpedance measurement system

A new extension of the AD5933 impedance measurement chip is presented. It allows to use the chip in the four electrode configuration to reduce the artifact effects of interface impedance between the electrode and the sample to be measured. The measurement approach is validated on various test circuits, and the system has been able to measure small physiological samples (50 ul) in a four microelectrode configuration and with a low sensitivity to interface impedances. The system is a good candidate for any embedded bioimpedance measurement system which requires a low sensitivity to interface impedances.

Interdigitated electrode biosensor for DNA sequences detection

In this work, we present the design of a biosensor for specific DNA sequences detection. Bioimpedance spectroscopy (BIS) is used to characterize DNA hybridization. This theoretical study allows to optimize the geometric parameters of the biosensors by reducing the cell factor (Kcell), where the CoventorWare software was used to modelize the biosensors for design. In addition, the acquisition by a Red Pitaya fast acquisition board for measuring the bioimpedance parameters was studied before the design of the biosensor.

Hybrid Microfluidic Biosensor for Single Cell Flow Impedance Spectroscopy: Theoretical Approach and First Validations

This paper presents a micro-biosensor based on Electrical Bio-Impedance Spectroscopy (EBIS), applied to blood cells diagnosis. Its hybrid conception uses the EBIS system coupled to a microfluidic device for cell by cell dynamic measurements. The microdevice is composed of 20x20μm² section micro channel, with platinum microelectrodes tested for different geometries. A Surface Acoustic Wave (SAW) device allows an accurate control of the fluidic displacement inside the channel. Simulation using athree dimensional Finite Elements Method (3D-FEM) have permitted to determinate the sensitivity of electrodes and to optimize their design, It also demonstrates the ability of our sensor to perform single cell measurements up to several hundred cells per second. First measurements confirms the simulation predictions and proved the ability to measure small impedance variations, less than 0.2%, during passage of particles.