Integrated inductive sensors for the detection of magnetic microparticles

372 IEEE SENSORS JOURNAL, VOL. 5, NO. 3, JUNE 2005

Integrated Inductive Sensors for the Detectionof Magnetic Microparticles

Salvatore Baglio, Senior Member, IEEE, Salvatore Castorina, and Nicolò Savalli

Abstract—In this paper, we deal with novel inductive microsen-sors, realized by using standard CMOS microelectronic technolo-gies, for the detection of small amounts of magnetic beads that areplaced in selected regions over the surface of the microsensor. Thesensor proposed here represents a step toward the development ofintegrated inductive biosensors for application in the area of mag-netic immunoassay where magnetic markers, carrying specific an-tibodies that selectively bind to the cells or molecules to be detected,are used; the measurement of the analyte concentration is there-fore accomplished by determining the concentration of magneticparticles tied to it. A planar differential transformer structure isproposed here as part of the measurement strategy. The analysis,simulation, and design of the proposed device are reported, and itssensitivity to the quantity of micromagnetic beads deposited overits surface has been also demonstrated through experiments.

Index Terms—CMOS technology, inductive microsensors, mag-netic immunoassay, planar differential transformer.

I. INTRODUCTION

THIS PAPER deals with the development of a microinduc-tive sensor for the detection of small magnetic beads.

The research efforts toward the development of such kind ofsensors are motivated by the potential of magnetic beads to beused, with suitable functionalization of their surface, as spe-cific markers for cells or molecules in magnetic immunoassaysystems. With respect to other types of markers (radioactive,enzymes, fluorophores, luminescent, etc.), magnetic ones havemany potential advantages: lower cost, higher stability, absenceof toxicity, etc.

In addition, biomolecules fixed to magnetic nanoparticles canbe easily localized and manipulated by suitable magnetic fields.

The aim of this paper is to demonstrate the feasibility of inte-grated inductive magnetic sensors and their sensitivity to smallamounts of magnetic beads, which is a promising characteristicfor the future application of the proposed approach to high-sen-sitivity, low-cost, portable immunoassay devices.

High-sensitivity magnetic sensors can be designed usingdifferent principles of detection, such as magnetic resistivetransducers, atomic force microscope based transducers, and

Manuscript received February 17, 2003; revised June 16, 2004. The associateeditor coordinating the review of this paper and approving it for publication wasProf. Michiel Vellekoop.

The authors are with the Dipartimento di Ingegneria Elettrica Elet-tronica e dei Sistemi (DIEES), University of Catania, 95125 Catania, Italy(e-mail: [email protected]; [email protected];[email protected]).

Digital Object Identifier 10.1109/JSEN.2004.839892

Fig. 1. Schematic of principle of the differential transformer.

Fig. 2. Three-dimensional sketch of the transformer.

Fig. 3. Working principle of the planar differential transformer.

inductance devices [1]. These latter transducers present impor-tant advantages, which are related to their higher simplicity,compatibility with standard Silicon technology materials, lowcost, and higher flexibility. They are based in the detection ofchanges in the relative magnetic permeability of gas, liquid,and solid samples that are positioned inside a measuring coil[1], [2].

In order to focus on integrated device in standard CMOS tech-nology, it is straightforward to consider planar microcoils. Thepresence of the magnetic markers (microparticles) in the core ofthe coil (or near it) produces a change in the inductance value.

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BAGLIO et al.: INTEGRATED INDUCTIVE SENSORS 373

Fig. 4. Equivalent circuit of the transformer.

Fig. 5. Signal conditioning circuit for the planar differential transformer.

The detection of this change is therefore a measure of the quan-tity of particles in the core of the coil or, better stated, of thedensity of magnetically active material in the core.

Planar inductors can be easily realized in standard CMOStechnology, and several realizations have been presented in lit-erature for RF and proximity sensors applications [3]–[5]. How-ever, in this paper, working frequencies well below the RF rangehave been assumed as design constraint in order to simplify thereadout circuitry that would be less sensitive to external inter-ferences than in the case of high-frequency circuits. Moreover,from the point of view of the application as a biosensor, low-fre-quency operations would avoid possible alterations of the bio-logical samples.

In the following sections, a detailed description, together withaccurate modeling of planar differential transformers, will begiven; then, the signal conditioning circuitry developed and thesensor prototypes realized will be introduced. Finally, some ofthe experimental results obtained will be reported and discussedin order to show the suitability of the proposed approach.

II. PLANAR DIFFERENTIAL TRANSFORMER

A. Principle of Detection

Several approaches to inductive sensing and to the relativesignal detection and conditioning have been presented; they areoften based on the use of a single coil in filters or oscillators.

The differential approach is used here in order to filter out un-desired effects related to interfering signals. A differential trans-former, where only one of the two secondary windings is madesensitive to the magnetic particles, is considered; the other sec-ondary coil allows subtracting spurious effects from the totaloutput of the transformer.

The device presented here is based on a planar coreless dif-ferential transformer configuration. A primary coil generates amagnetic flux which links with two secondary coils, with oppo-site winding sense, connected in a differential arrangement. InFigs. 1 and 2, both the simplified schematics and a sketch of theproposed device are shown.


Fig. 6. Simulated gain of the transformer for relative inductance change between 0% and 2.5% (step 0.25%).

The primary coil generates a magnetic flux that induces equal,but opposite, voltages at the secondary coils, due to their oppo-site winding sense; therefore, the resulting output voltage, whichis the difference between the voltages across the secondary coils,is zero when no magnetic particles are present. On the otherhand, the presence of magnetic particles in one of the secondarycoils will cause a redistribution of the magnetic flux lines, whichwill result denser near the magnetic particles (if paramagneticparticles are used), therefore resulting in a nonzero differentialoutput voltage. This working principle is schematized in Fig. 3.

In this approach, one of the secondary coils acts as the “ac-tive” sensor, while the other one acts as “dummy,” like in mostdifferential sensing approaches. In particular, here, the differen-tial configuration is used not to enhance sensitivity; in fact, thereare no opposite variations of inductance, but to lower the noisefloor. The primary coil is a source of excitation of the sensor.This approach allows a more flexible optimization of the devicein terms of sensitivity; in fact, in the case of the transformer,the open circuit voltage at the secondary coil, if expressed interms of the current applied to the primary winding, is propor-tional to the product of the number of turns of the primary andthe secondary coils. While the secondary coils can be subjectedto more restrictive design constraints due to their sensing func-tion, the primary coils has less restrictions; therefore, both thesensitivity requirements and eventual design constraints can be

more easily satisfied with respect to the single inductor case, byproper designing the primary and secondary coils.

Furthermore, the approach presented here is intrinsically dif-ferential, thus allowing a better rejection of noise and interfer-ences. It is suitable for the integration in CMOS technology dueto its simple and planar geometry. Moreover, it is not based onthe direct estimation of the inductance, resulting in a great sim-plification of the measurement strategy. In fact, the magneticparticles act as a moveable nucleus and the differential outputvoltage at the secondary coils is directly related to the number(or density) of magnetic particles. Therefore, a high-impedancedetection of the differential output voltage at the secondary coilsis a simple, but good, strategy in the detection of the magneticparticles.

The feasibility of this approach has been first validated with a“macro” prototype realized with the printed circuit board (PCB)technique and iron filing grains instead of the magnetic mi-croparticles, and then CMOS prototypes have been designed,realized, and tested with magnetic microparticles.

B. Analysis of the Planar Differential Transformer

The simple schematic of Fig. 1 can be used to describe the op-eration of the sensor in ideal conditions, but it does not allow fortaking into account some real operation needing and some par-asitic effects. First, integrated inductance values are very small


Fig. 7. Simulated gain of the transformer versus relative inductance change at different frequencies.

TABLE IGEOMETRIC AND ELECTRIC FEATURES OF A TRANSFORMER

and require operation in the RF field. However, from the pointof view of the perspected application in magnetic immunoassay,the RF range should be avoided because of the risk of alterationsof biological samples due to the induced heating. Moreover, op-erations at RF introduce the problems of shielding, interference,and all the typical effects of such a range of frequency that couldexcessively complicate the design of the system and the relia-bility of the measurements. For such reasons, the operating fre-quency of the device is limited by connecting capacitive loadsto the secondary windings.

Fig. 8. PCB transformer prototype.

Furthermore, the small dimensions of the tracks used to re-alize the coils, especially in the integrated version of the sensor,the absence of a magnetic core, thus the nonperfect magneticcoupling between primary and secondary windings suggest tomake use of a circuital model where the nonidealities of thetransformer, like the series resistance of the coils, their leakageinductance, and their nonideal coupling are taken into account.

The leakage inductance takes into account for the part of themagnetic flux that does not contribute to the magnetic coupling;the magnetizing inductance takes into account the finite induc-tance of the transformer [6], [7].

Due to the planar structure of the transformer, where the pri-mary winding faces the secondary ones, a capacitive couplingbetween the windings may affect the operation of the device;therefore, it should be taken into account in the model.

The complete circuit model of the transformer is shown inFig. 4, where represents the leakage inductance of the th


Fig. 9. Experimental procedure and setup for the characterization of the PCB transformer prototype with iron filing.

coil, and are the magnetizing inductances, is theseries resistance of the th coil, and are the parasiticcapacitance between the primary coil and each secondary coil,and and are, respectively, the resistance and the capac-itance of the load, which is the signal conditioning circuit.also takes into account for the capacitance used to adjust the res-onance frequency.

The voltage across the load connected to the secondary 2 (andsimilarly the voltage across the load connected to secondary 3)results

(1)

where

(2)

and is the complex frequency.The gain of the transformer in the frequency domain is

(3)

for the circuit of Fig. 4, , and are given by

(4)

(5)

where

(6)

and, by expressing the variable inductance as, with , the mutual inductance results

and, therefore

(7)

(8)

(9)

The coupling capacitance between the primary coil and eachsecondary ones has been calculated by approximating the coilsto circular plates. This is a worst-case approximation and, there-fore, it produces a conservative value. This value is low enough

to have no appreciable effects at the operating frequencies of thedevice.

The self and mutual inductances of the coils have been calcu-lated by using the method proposed by Hurley and Duffy [8].

III. SIGNAL CONDITIONING CIRCUITS

Commercially available, general-purpose discrete compo-nents and ICs have been used to realize the signal conditioningcircuit for the proposed sensor.

As stated in the previous section, there is the need to supplythe primary winding with a sinusoidal current with constantamplitude; therefore, a voltage-to-current converter is requiredto provide such a current to be insensitive to the impedancechanges at the primary coil.

The voltages at the secondary coils can be detected by usingan oscilloscope; however, a circuital detection of the outputsignal has been taken into account here. In particular, the dif-ference in the peak voltages at the secondary coils is of interest;therefore, two peak detectors are required. Voltages at thesecondary coils are picked-up by unity gain buffers (BUF 04)to ensure a high-impedance reading. The dc values provided bythe peak detectors are amplified with an instrumentation ampli-fier (INA 111). Load capacitances are connected in parallel tothe secondary coils to reduce the resonant frequency value.

A complete circuit diagram of the signal conditioning circuitis shown in Fig. 5.

IV. SIMULATION OF THE PLANAR

DIFFERENTIAL TRANSFORMER

Equation (3) has been used to simulate the behavior of the de-vice in MATLAB. The simulated gain, defined as the differentialoutput voltage at the secondary coils, divided the current in theprimary, i.e., the transconductance of the transformer, for a rela-tive inductance change from 0% to 2.5%, is shown in Fig. 6 as afunction of frequency and in Fig. 7 as a function of the relativeinductance change. Such a simulation is relative to the trans-former with the geometrical and electrical features summarizedin Table I.

The plots in Figs. 6 and 7 show, as expected, that the change inthe inductance value produces a variation in the gain value, witha maximum in correspondence to the resonance frequency. Fur-thermore, the variation of the gain with the relative inductancechange is linear with good approximation for small values of


Fig. 10. Measured gain of the transformer for different amounts of iron filings in a secondary coil core (dotted lines with markers). The best-fitting simulated plotsare also reported for comparison (continuous lines). The relative inductance variation caused by a given amount of iron filing has been approximately estimated bycomparing simulated and experimental results.

. The change in the transformer gain value is directly corre-lated to a change in the differential output voltage, if a constantamplitude sinusoidal current is provided to the primary winding.

V. EXPERIMENTAL RESULTS

A. PCB Macro-Prototype

The PCB prototypes have been realized by “printing” the pri-mary and secondary coils on two distinct boards and then by su-perimposing them to realize the transformer. Double-face PCBshave also been used, but, in this case, the eventual “printing”misalignments between the two sides cannot be corrected.

Circular spiral windings have been considered because theypresent lower series resistance and interwinding capacitancedue to their lower area to perimeter ratio, with respect to othergeometries.

The layout of the coils and a photo of the two boards areshown in Fig. 8. The geometric and electric features of the pro-totype are reported in Table I.

The characterization of the “macro” PCB transformer proto-type has been performed by placing some amounts of iron filinginside one of the secondary coil cores and by measuring the cor-responding variations in the output voltage with respect to an

“equilibrium” condition where no iron grains were present. Theexperimental procedure and setup are shown in Fig. 9.

In a first characterization procedure, the iron filing has beenplaced in the PCB transformer core in quantities correspondingto an integer multiple of a well reproducible one; the weight ofsuch a “unitary” amount of iron filing has been measured withan assay balance, and its value is mg. The amountsof iron filing used in this phase go from one to four times the“unitary” quantity. In Fig. 10, the measured transformer gainis shown, together with the simulated plots, that better fit themeasured data. In such a way, the inductance variation inducedby a given amount of iron filing has also been approximatelyestimated. The measured differential output voltage at 21 MHz,i.e., close to the resonance peak, for different amounts of ironfiling is reported in Fig. 11. From this latter plot, an averagesensitivity to the presence of iron filing of 2.6 mV/mg can beestimated.

The operating frequency can be further reduced by increasingthe load capacitance. However, a significant decrease in theoutput voltage and, then, in the sensitivity has been predictedand observed; therefore, a tradeoff should be accurately chosen.

In a second phase of the characterization, a more refinedvalidation of the device has been performed by placing single


Fig. 11. Measured differential output voltage of the transformer versus quantity of iron filing. The average sensitivity results 2.6 mV/mg.

grains of iron filing. The results relative to the differentialoutput voltage at 9.7 MHz for 100 grains are shown in Fig. 12.

In Fig. 12, two different series of measurements are reported.From these results, good linearity and reproducibility arise. Thedifferences between the two plots and the “steps” in their trendcould be due to the nonhomogeneities in the grain size. FromFig. 12, a qualitative sensitivity of about 1 mV/grain can beestimated.

The “macro” PCB prototype has been conceived and realizedto validate the approach prior to proceed to an integrated CMOSrealization of the sensor.

In the next section the design, simulation, and characteriza-tion of such integrated devices are reported.

B. CMOS Integrated Microprototype

Some integrated prototypes have been designed by using the0.8- m CMOS CXQ technology by Austria Mikro Systeme(AMS). This is a standard CMOS technology with two metallayers. These layers have been used to realize the windings ofthe planar transformer. The primary winding has been realizedin the Metal 1 layer, while the Metal 2 layer has been used to re-alize the secondary windings. The secondary coils are separatedfrom the primary one by the VIA oxide. The passivation layercovers the whole transformer except for the central area of thesecondary coils.

A picture of a circular transformer prototype is reported inFig. 13, and a schematic cross section is shown in Fig. 14.

The geometric and electric parameters of such microtrans-formers are summarized in Table II. Here, the self and mutualinductance values have been calculated with the method pro-

posed by Hurley and Duffy [8]. The coupling capacitance be-tween the primary and each secondary has been calculated byconsidering the spiral windings as circular plates.

The characterization of the transformer with open circuit con-ditions at the secondary coils is shown in Fig. 15, and it revealsa slight asymmetry between the voltages across the two wind-ings. At a given working frequency, this asymmetry results in anoffset in the differential output voltage that does not affect themeasurement; however, such an offset can be eventually com-pensated by the signal conditioning circuit. It can be highlightedthat, without any capacitive load connected in parallel to the sec-ondary windings, the resonance frequency of the system is about34 MHz, which is well below the RF range, but, depending onthe application, it could be high enough to introduce undesiredeffects in the measurement process and/or to complicate thesignal processing. Therefore, as for the PCB prototypes, loadcapacitance will be connected in parallel to each secondary coilto reduce the resonant frequency to a convenient value.

The circuit shown in Fig. 5, in the case of the CMOS micro-transformer , has been assembled on a suitably designed PCB. Inthe realization of such a circuit and PCB, particular attention hasbeen devoted to shielding and minimizing electromagnetic in-terferences. The whole PCB has been placed in a metallic shieldbox and connected to the measurement instrumentation throughcoaxial shielded cables. The final system assembly is shown inFig. 16.

The characterization of the device has been performed byplacing over increasing quantities of micromagnetic particlesone secondary coil and by detecting the amplified difference inthe peak voltages at the secondary coil in a wide range of fre-quencies. The particles used for the characterization were the


Fig. 12. Experimental “single grain” characterization of the transformer.

Fig. 13. Layout of the circular microtransformer prototype.

SPHERO Polystyrene Carboxyl Magnetic Pparticles, SmoothSurface by Spherotech, Inc. A 0.5-ml 2.5% w/v sample of par-ticles with an average diameter of 4.1 m, containing a totalamount of 12.5 mg of particles having a density of 1.05 g/cm ,has been used for the characterization.

Since only one sample of magnetic particles with a given con-centration was available for the device characterization, the in-crease of concentration has been “simulated” by incremental de-position of the sample over the sensors. First, a given amount ofsample volume has been drawn, placed over the sensor, dried

out, and then the output voltage has been measured. The suc-cessive characterization steps have been performed by addingother amounts of sample to the dry quantity already depositedover the sensor in such a way that several concentrations havebeen simulated. The lack of a repeatable drawing system didnot allow for the same amount of samples each time; however,this does not affect the validity of the characterization methodadopted.

Four different amounts of samples have been withdrawn interms of percentage of the initial sample volume. Samples havebeen agitated before each withdrawal to ensure a homogeneousdistribution of particles.

The four phases of the characterization, with the dried parti-cles deposited over the sensor, are show in Fig. 17. The resultsof the characterization are reported in Fig. 18 in terms of thepeak voltage difference between the secondary coils, in the fre-quency range MHz, while, in Fig. 19, the response ofthe system in terms of output voltage versus sample concentra-tion at 13.2 MHz is reported.

From the plot of Fig. 19, a sensitivity of 2.93% /mg/mlcan be estimated for concentrations higher than 25 mg/ml.

To compare the responses of both the device prototypes pre-sented in this paper, the PCB and the CMOS ones, it is necessaryto express the response of the integrated transformer in terms ofparticles weight instead of concentration; in fact, the character-ization of the PCB transformer has been done by using “dry”deposited iron filing. The responses of the two devices are com-pared in Figs. 20 and 21, in logarithmic and normalized scales,respectively.


Fig. 14. Schematic of the cross section along a radial direction.

Fig. 15. Measured frequency response of the CMOS integrated microtransformer with open-circuit secondary coils.

Both Figs. 20 and 21 show the performance improvementachieved with the integrated sensor; in fact, the output voltageof the circuit employing the integrated device is higher than thePCB one, and a high-output voltage is achieved with smalleramounts of sample. Such a gain in terms of performance is evenhigher if the different nature of the samples used for the charac-terization of the two prototypes is considered; in fact, the para-magnetic particles used for the characterization of the integratedsensor have a relative magnetic permeability at least one orderof magnitude smaller than those of the ferromagnetic iron filingused in the case of the PCB device.

In terms of sample weight, the sensitivity of the integratedprototype can be estimated in 730 mV/mg, which is 280 timeshigher than the sensitivity of the PCB one.

VI. POTENTIAL APPLICATION: MAGNETIC IMMUNOASSAY

There is an important need for the development, in futureyears, of low-cost and high-performance transducers for the de-

Fig. 16. Experimental assembly for the CMOS microtransformer and its signalconditioning electronics.

tection of biological agents. This is critical in many fields relatedto public health, foods industry, water management, and clinical


Fig. 17. Four phases of the characterization of the CMOS microtransformerwith magnetic particles.

TABLE IIGEOMETRIC AND ELECTRIC FEATURES OF THE CMOS MICROTRANSFORMER

and diagnostic analysis. In particular, requirements for publichealth and environmental impact demand for the availability ofhigh sensitivity, low cost, and simple analytical tools. All thisimposes the need of sensors, for application to biological sys-tems, combining the characteristics of low cost, high sensitivity,and specificity, with short analysis time, ease of handling, andease of transporting for in situ and in-field measurements.

High sensitivity and specificity can be obtained by using im-munological techniques [9], which are based in the biologicalrecognition of the analyte to be detected by specific antigen orantibodies.

The application of the measurement system to magnetic im-munoassay proposed here requires the realization of function-alized surfaces, the coil core or its whole surface [10], and themagnetic particles to be used as markers. Such functionaliza-tion consists of the coating of the sensors and particles surfaceswith suitable materials to allow the binding of the suitable an-tibodies, as schematized in Fig. 22(a) and (c). These steps are

essential to apply a given detection system or method to im-munoassay and to achieve the required specificity. As shownin Fig. 22(a)–(d), only the targeted analyte binds to its specificantibodies, remaining trapped to the sensor surface, then thefunctionalized markers bind to the trapped analyte which canbe detected. Once the “sandwich” represented in Fig. 22(d) isformed, then the problem is to detect the number or density ofthe markers. Suitable methods and systems should be adopteddepending on the type of markers used.

In the specific case of magnetic immunoassay based on in-ductive sensors, the quantitative detection of the analyte in thespecimen is determined by the amount of magnetic nanoparti-cles fixed to the surface, which in turns determines a change inthe inductance of the coil. Measurement of the inductance witha simple electronic circuit allows the quantification of the ana-lyte content in the specimen.

In this paper, we demonstrated that inductive microsensorsrealized by means of standard IC technologies are sensitive tothe presence of magnetic beads of the type which can be used asmarkers in a perspected application to magnetic immunoassaysystems.

The device presented here can be considered a preliminarystep toward the realization of such magnetic immunoassaysensors.

Further efforts must be devoted to realize suitable functional-ization of the sensor and beads surfaces with specific antibodiesin order to achieve the desired selectivity against the analyte,and the experimental conditions represented in Fig. 22, wherea monolayer of markers is tied to the sensor surface, in orderto prove that the proposed approach can achieve sensitivityvalues comparable with those of “traditional” immunoassaytechniques.

VII. CONCLUSION

An inductive, integrated microsensor based on the use of theplanar differential transformer configuration, for the detectionof small magnetic particles, has been described here.

Analytical models have been derived for the sensor and itsbehavior with respect to inductance change has been simulated.A suitable signal conditioning circuit has been also designed,realized, and tested together with the sensor prototypes.

The proposed approach has been firstly validated by meansof “macroscopic” sensor prototypes realized with the PCB tech-nique. Then a miniaturized sensor has been developed in a stan-dard CMOS technology.

The ability of the proposed sensor to detect different amountsof micromagnetic particles has been demonstrated here.

Arrays of sensors can be easily realized on the same substrate,together with the signal conditioning electronics, thus realizinga fully-integrated analysis system.

The performance of the integrated device presented hereencourages further efforts for the development of low-cost,high-sensitivity, integrated magnetic immunoassay systems.


Fig. 18. Experimental results of the characterization with magnetic particles.

Fig. 19. Characterization of the sensor with magnetic particles. The amplifier’s output voltage is reported versus different “simulated” concentration values ofthe sample.


Fig. 20. Comparison between the responses of the PCB and the CMOS transformer prototypes in terms of sample weight.

Fig. 21. Comparison between the responses of the PCB and the CMOS transformer prototypes in terms of sample weight normalized to the maximum sampleamount for each case.


Fig. 22. Schematics of the detection principle. (a) The sensor surface isfunctionalized with the specific antibodies. (b) Only the specific analyte in thesample binds to its antibody on the surface. (c) The functionalized markersbind to the trapped analyte. (d) The “sandwich” is ready for detection.

ACKNOWLEDGMENT

The authors would like to thank the researchers of the Univer-sity of Barcelona, Spain, and of the Centro Nacional de Micro-electronica, Barcelona, Spain, in collaboration with whom thiswork has been developed into the framework of the EU project“MicroBioL .”

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Salvatore Baglio (S’91–M’94–SM’03) was born inCatania, Italy, in 1965. He received the Laurea andPh.D. degrees from the University of Catania in 1990and 1994, respectively.

He was a Lecturer of automatic control theoryat the University of Messina, Messina, Italy, and ofelectronic measurement systems at the University ofCatania. He was also a Consultant for STMicroelec-tronics in the field of soft computing methodologiesfor nonlinear and chaotic circuits and systems.Since 1996, he has been with the Dipartimento di

Ingegneria Elettrica Elettronica e dei Sistemi, University of Catania, where heis now Associate Professor of electronic instrumentation and measurements.He teaches courses in measurement theory and sensors and transducers. Heis the coauthor of more than 150 scientific publications, among which papershave been published in international journals or presented at internationalconferences or as chapters in books, and he holds several U.S. patents. Hisresearch interests are mainly focused on measurement methodologies, smartsensors, microsensors and microsystems.

Dr. Baglio has been an Associate Editor for the IEEE TRANSACTIONS ON

CIRCUITS AND SYSTEMS and a Distinguished Lecturer for the IEEE Circuits andSystem Society.

Salvatore Castorina was born in Catania, Italy, in1974. He received the M.S. and the Ph.D. degrees inelectronic and automation engineering from Univer-sity of Catania in 2000 and 2004, respectively.

He is collaborating with the electronic mea-surement group at University of Catania as aConsultant. He is the coauthor of several scientificpapers published in international conferences andjournals. His research interests are in the fields ofmicrosensors and microactuators, microrobotics,and nanotechnologies.

Nicolò Savalli was born in Siracusa, Italy, in 1972.He received the M.S. and Ph.D. degrees from the Uni-versity of Catania, Catania, Italy, in 1999 and 2003,respectively.

Since 1999, he has been with the Dipartimento diIngegneria Elettrica Elettronica e dei Sistemi, Engi-neering Faculty, University of Catania. He teachescourses in measurement theory and measurementapplications. He is the coauthor of more than 35scientific publications, among which papers havebeen published in international journals or pre-

sented at international conferences. His research interests include MEMSand MOEMS realized in standard and nonstandard technologies, tactilesensors, and soft computing strategies for measurements.

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Integrated inductive sensors for the detection of magnetic microparticles