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Sensors and Actuators A 185 (2012) 53– 58

Contents lists available at SciVerse ScienceDirect

Sensors and Actuators A: Physical

jo u rn al hom epage: www.elsev ier .com/ locate /sna

echanical model of flex sensors used to sense finger movements

iovanni Saggio ∗

niversity of Rome “Tor Vergata”, Dept. of Electronic Eng., via del Politecnico 1, 00133 Rome, Italy

r t i c l e i n f o

rticle history:eceived 28 May 2012eceived in revised form 26 July 2012ccepted 26 July 2012vailable online 3 August 2012

eywords:lex sensorodeling of sensors

a b s t r a c t

Flex sensors change in their electrical resistance value depending on the amount of bend they are sub-jected. These sensors can be realized with different techniques, but the mostly adopted are based on aresistive element film, which can be made of a PEDOT:PSS polymer or of a carbon-based element, printedon a plastic substrate.

We investigated from a theoretical point of view the mechanical aspect of these sensors related to theirutilization to sense finger movements, to determine the relationship with the electrical behavior. Thiswas to provide enhanced degrees of understanding and predictability in performances.

Experiments were conducted on custom-made flex sensors based on PEDOT:PSS polymer, to measure

EDOT:PSS the resistance variations vs. the amount of bend radius induced in the sensors, in either of two opposingdirections (outward and inward).

Results demonstrated that the mechanical behavior influences the electrical counterpart but linearly,the more the bent the more the increase in the resistance, in a direct proportion. When a nonlinearbehavior is measured, as in the case of commercially available Flexpoint sensors, it was found to dependonly to causes strictly related to physical changes in the resistive element (cracks under stress).

© 2012 Elsevier B.V. All rights reserved.

. Introduction

Several works deal with sensors utilized to measure goniomet-ic parameters related to the human body, such as postures andexion dynamics of fingers, wrist, elbow, knee, ankle. In generalhose works intended to measure the bending of all sorts of “humanoints”. In such a view, the sensors have been placed on the user’skin within singular sleeves [1], or inserted in an open wearablerchitecture [2], or embedded into clothes [3,4], or deposited ontoextile fibers [5], or even directly utilized as a sort of skin them-elves [6]. In all these occurrences, it is a common opinion thathe sensors have always to strictly adhere to the joint, so to movexactly as the related joint, to guarantee correct measures. But,ccording to our knowledge, there is a lack of research investigationn how the mechanical performances are related to the electricalnes, and how a not perfect mechanical adhesion of the sensor fromts related human’s joint, could affect the results of the measure-

ents.In this work we utilized the so called flex sensors (also known

s bend sensors), described in the next section.

∗ Tel.: +39 06 72597260; fax: +39 06 23314067.E-mail address: saggio@uniroma2.it

924-4247/$ – see front matter © 2012 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.sna.2012.07.023

2. The materials

2.1. The sensors

We utilized and investigated the mechanical and electrical prop-erties of flex sensors. In particular we measured low cost, flexible,polymeric sensors, made of conductive polymer (PEDOT:PSS) thinfilms, deposited on flexible substrates of polyimide (see Fig. 1).These were custom-made flex sensors but known by the scientificcommunity and easy replicable with low cost techniques.

On a substrate of highly doped p+ silicon wafer cov-ered with thermal grown silicon oxide, it was patterned ametallic layer (Au/Cr), on top of which it was depositedthe PEDOT:PSS polymer matrix by electrochemical polymeriza-tion. The patterned electrodes were transferred to a polyimidesupport, obtained depositing a solution of a poly(trimellitic-anhydride-chloride copolymerized with 4,4-methylenedianiline)in N-methylpyrrolidone. After curing, a flexible and toughpolyamide film is peeled off from the anode surface. Accuratedetails of all the steps are reported in [7].

For comparison, measurements were made also on commercialsensors by Flexpoint Inc. (www.flexpoint.com), which have a sensi-

ble part made of carbon elements deposited on supporting flexiblethicker plastic film.

The fundamental characteristic of flex sensors is that theychange their electrical resistance value when flexed. So, a necessary

54 G. Saggio / Sensors and Actuators A 185 (2012) 53– 58

Ftm

sria

2

moitfcfiw

Fpti

hδ

x

y

z

Fig. 3. Schematization of the sensor as a rectangular parallelepiped, of total thick-

ig. 1. The PEDOT:PSS patterned layer on a plastic substrate. Mechanical proper-ies guarantee the possibility to flex the sensor even with large bending angles but

aintaining elastic and electric properties.

tep was to measure the resistance-angle pairs to determine theirelationship. The procedure can be time-consuming, and a source ofnaccuracy [8] so, to drastically reduce these problems, we realizedn automatic procedure with an ad-hoc home-made set-up.

.2. The set-up

An home-made set-up was realized to mimic the flex-extensionovements that a human finger’s joint can do. The set-up consisted

f a hinge, made of a knuckle through which a central circular pins passed, and with two notched leafs which extend laterally fromhe knuckle (see Fig. 2). The hinge was made with tolerances ofew microns. One of the leaf of the hinge was fixed with the pin, so

apable to revolve together it, while the other one was maintainedxed. A stepper motor (PD-109-57 by Trinamic) was connectedith the central pin of the hinge through an elastic joint in order

ig. 2. The set-up consisting of a stepper motor (at the bottom), driving the centralin of a hinge (upper in the figure), made of two leafs one of which was fixed andhe other can rotate. The sensor is visible only in its central part, since the remainingn under buttonholes to remain attached to the hinge.

ness h + ı (substrate + sensible part), and the longitudinal side longer than thetransversal one. The darker pads are for electrical contacts.

to minimize friction torque, and the system was controlled with aLABVIEW routine ad-hoc realized.

The electrical resistance values of the sensors were measured ateach bending angle by a 5.5 digits digital multimeter (34405A byAgilent). We devoted particular attention to let the sensors undermeasure to be under bending forces but without shears or torsions.

3. The theory

The sensors here treated have the characteristic of a substratemuch thicker compared to the sensible part, and have geometricand mechanic characteristic similar to those of the beams. This isthe reason why we applied for them the standard beam theory.

We considered each sensor as a homogeneous and isotropicbody, of a constant cross section and of finite size. In particular thethickness of the sensible part “ı”, was considered to be negligiblewith respect to the thickness of the substrate “h” (see Fig. 3).

Let’s start considering the Gauge factor (GF), or strain factor,being an indicator of the ratio of relative change in electrical resis-tance to the mechanical strain ε = �l/l (“�l” is the absolute changein length and “l” the original length), which is the relative changein length, according to the formula:

GF = �R/R

ε(1)

when the temperature can be considered, as in our case, of a con-stant value.

It is possible to define different GF as function of the direction ofthe applied strain “ε” [9]. Here we consider the longitudinal gaugefactor GFL, according to the fact that the strain was applied in thelongest part of the sensor, the x axes, parallel to the current flow.This GFL value depends on the characteristic of the film and on themechanical properties of the substrate [10].

To proceed with the theory we distinguish three possible cases:(A) the sensor flexes and its body remains in contact for all its lengthwith the finger, as schematized in Fig. 4a; (B) the sensor flexes andits body remains partially in contact with the finger, i.e. in the seg-ments O–A, O–A′ and points B and B′, as in Fig. 4b; (C) the sensorflexes but its body remains in contact with the finger only in thepoints, O, B, B′, being the segments O–A and O–A′ reduced to justpoints.

3.1. (A) Complete adhesion of the sensor to the finger

Anything that bends (deflects) experiences tension and com-pression. The deflection of a material is its vertical displacement(strain) from the unstressed (neutral) position.

When the sensor, comparable to a sort of beam for our purposes,is subjected to a bending force in an outward mode (see Fig. 5),its bottom fibers are subjected to shorten (compression), and theupper fibers, where the sensible part is deposited, are subjected to

lengthen (tension). This internal combination of compression andtension is referred to as bending stress. The only unchanged fibersare those of the middle plane, which is the neutral axis, since noelongation or shortening is for it.

G. Saggio / Sensors and Actuators A 185 (2012) 53– 58 55

Fig. 4. The sensor (a) perfectly adhere or (b) have detachments respect the hinge( ′

a

ph

apttl

l

a

l

Fg

or the joint). In the latter case the contacts can be segments and point (O–A, O–And B, B′) or points (O, B, B′).

This mechanical behavior is exactly what occurs to the sensorlaced over a finger’s joint, as visualized in Fig. 6, or placed on theinge as in Fig. 2.

Let “r” be the radius of the pin over which the sensor is placed,nd �ϕ the rotation of the hinge. As schematized in Fig. 4, only aart of the sensor of length “lb” is subjected to be bent. Consideringhat the thickness of the sensible part is negligible with respecto the sensor’s substrate, ı � h, and that r � h/2 we can write theength of the bent sensible part as:

b =(

r + h

2

)�ϕ ∼= r �ϕ (2)

nd the total elongated sensible part as:

b + �l =(

r + h + ı

2

)�ϕ (3)

Δϕ

h

PO

AO’P’

rr*

l+ lΔ

δ

neutral axis

ig. 5. Perspective view of the bent sensor when flexed. The part subjected to elon-ation is within the 0–0′ points. 0–P and O′–P′ parts are without variations.

Fig. 6. Sensor (gray color) positioned over the Proximal-Inter-Phalangeal joint ofthe index finger.

It follows that the mechanical strain “ε” is:

ε =(

�l

l

)= (r + h + ı/2)�ϕ − (r + h/2)�ϕ

(r + h/2)�ϕ= (h/2 + ı/2)

(r + h/2)

= �(h + ı)2

∼= �(

h

2

)(4)

where the curvature of the longitudinal axis is

� =[

1r + h/2

]∼= 1

r(5)

But, maintaining the “b” subscript for the strained bent part, andrecalling the definition of GFL, we have:

�Rb

Rb= εGFL (6)

Now, considering the simple proportion:

Rb =(

lbl

)R (7)

and observing that �Rb = �R, since only the strained part of thesensible material contributed to the resistance variation, we canadmit that:

�R

R=

(Rb

R

) (�Rb

Rb

)=

(lbl

)εGFL ∼=

(h

2l

)�ϕGFL (8)

So, in accordance to this final equation, it results that the output�R/R signal which can be obtained from the sensor when bentaccording to the flexion of a human joint, is expected to be indepen-dent from the radius r of the joint (or of the hinge’s pin), and linearlyproportional to the bending value �ϕ, considerable as an inputvalue. Furthermore, the relative change in electrical resistance ofthe sensor is directly proportional to the longitudinal gauge factorGFL and to the substrate thickness “h”, while it is inversely propor-tional to the length “l” of the sensible part of the sensor. This lattercan be reported as the distance between the electrodes by whichthe signal is acquired (see pads for electrical contacts in Fig. 3), sofor the current analysis it makes sense to anchor the electrodes onlyouter of the length named “lb”.

This theory refers to the case of a sensor which completelyadheres to the hinge (or finger) when bent. Let’s consider cases

of a not complete adhesion, i.e. with detachments (see Fig. 4b).

These detachments can reasonably occur in the parts of the sen-sor which lay between the zone in correspondence with the flexingjoint and the sensor’s ends.

56 G. Saggio / Sensors and Actuators A 185 (2012) 53– 58

ΔϕB

F2 F1x

y

zA0

lcl*-lc

l*/2

F

3

cbad

ti

t

•

•

r“t

4

t

l

T�csaga

h

idsso

4

t

Fig. 8. Relative changes of electrical resistance value of the PEDOT:PSS based sensorvs. the angles of bending, both for outward and for inward mode. Bars report thevalues of standard deviation. The two dotted linear lines refer to values of GF equal

22

ig. 7. Half sensor under rotation forces which cause detachment conditions.

.2. (B) Partial adhesion of the sensor to the finger

For the case of partial adhesion of the sensor to the finger, itan be considered the theory of a clamped-clamped linear elasticeam, one clamp subject to an imposed rotation, accordingly to thenalysis of statically indeterminate structures by the displacement (orirect stiffness) method.

Let’s define r* = r + h/2, l* the distance between two extreme con-act points (constrains) B–B′, and lC the length where the adhesions complete (see Fig. 4b).

Recurring to Fig. 7, which represents half of the sensor (beinghe other part symmetrically disposed), we can affirm that:

when �ϕ > l*/4r*, the substrate adheres to the hinge (or the fin-ger’s joint) along the segment “OA”, and in the point “B”;when �ϕ < l*/4r*, the substrate adheres to the hinge (or the fin-ger’s joint) only at point “O”, and remains outdistanced from thewing of the hinge (or the finger) until point “B”.

At the point “B” the curvature is equal to 1/r*. In particular, theelative rotation of the sensor’s cross section in “A” with respect toB” is given by �ϕ/2 − lC/2r*. Then, imposing the curvature at “A”o be 1/r*, the following equation is obtained:(

�ϕ

2− lC

2r∗

) (2

l∗ − lC

)= 1

r∗ (9)

hen

C =(

4r∗

3

) (�ϕ − l∗

4r∗

)(10)

he value of lC is positive when �ϕ > l*/4r*, and vanishes whenϕ = l*/4r*, which can be considered as a cutoff situation. In any

ase the curvature � (defined in Eq. (5)) is not uniform along theubstrate: indeed, it is a function of the curvilinear abscissa “s”, �(x),long the substrate axis. As a consequence, the strain “ε” in the film,iven by Eq. (4), does depend on “x”, ε = ε(x), and Eq. (8) generalizess:

�R

R= 1

lGFL

∫ l∗/2

−l∗/2

ε(x)dx = 1l

GFL

∫ l∗/2

−l∗/2

�(x)h

2dx = GFL

h

2l�ϕ (11)

aving adopted the evident equality∫ l∗/2

−l∗/2�(s)ds = �ϕ.

It is interesting to note that Eq. (8) governing the sensor responsen the latter model coincides with Eq. (11), obtained after intro-ucing the simplifying assumption of tight contact between theubstrate and the wings of the hinge (or the finger). In fact, it can behown that it governs the sensor response as far as the assumptionf vanishing axial strains in the substrate is appropriate.

. The measures

Relationship between the relative changes of electrical resis-ance values of the sensors and the angles of bending were assessed.

to 21.8 (=17.8 + 4) and 13.8 (=17.8 − 4), i.e. the external values with respect to themedium value of 17.8, so taking into account the related error. The measured valuesare within these two dotted lines accordingly with the theory.

The PEDOT:PSS polymer based sensors presented properties ofbi-directionality, since when they were bent towards the printedside, i.e. outward mode (as schematized in Fig. 5), the conductiveelement increased the resistance values, while in opposite direc-tion, i.e. inward mode, the electrical resistance values decreased.

So, all measurements were swept from −90◦ to +90◦, iterating10 times both in inward (−90◦ to 0◦) than in outward (0◦ to +90◦)mode. Within the single sweep, we paused for 6 s every 10◦ in angle,acquiring 10 measures each time, so a total of 1900 measures werecollected (19 steps for every sweep, by 10 measures, by 10 iter-ations). The same procedure was repeated adopting three hingesdifferent in pin radius, of 0.8 cm, 1.0 cm and 1.2 cm respectively,acquiring a total of 5700 resistance values. The overall process wasthen repeated once a day for 10 days, to take into account eventualshort-time drifts in performances, so that the total amount of datawere recorded in a matrix of 57,000 cells. For repeatability anal-ysis, the 10 samples acquired during each pause every 10◦ wereaveraged, and the dimension of the matrix reduced to 5700.

Each element of the bi-dimensional matrix was named xij, beingi = 1, 2, . . ., 10 the iteration number and j = 1, 2, . . ., 19 the step num-ber associated at every stepped angle.

Few modifications of the set-up were made to realize the partialadhesion of the sensor to the substrate as considered in Section 3.1.In particular we forced only the ends of the sensor and its centerpart (points B, B′ and O in Fig. 4b) to remain in contact with thesubstrate during the measures.

For comparison, measurements were performed on commercialsensors too. In particular we utilized 2 in., polyester over-laminatedsensors from Flexpoint Inc., since their very low values in sig-nal drifts [11], compared to other type of Flexpoint sensors(bare or polyester over-laminated) and to other similar commer-cial products too (for instance the Abrams-Gentile Flex Sensor,www.imagesco.com). The procedure was the same as for thePEDOT:PSS polymer based sensors, except that we could collectmeasures only for the outward mode, because the Flexpoint sensorsdo not present bi-directional capabilities.

5. Results and discussion

Fig. 8 shows the values of the relative changes of resistance �R/R

of the PEDOT:PSS based sensor vs. outward and inward bending val-ues in degree. For each point representing a measure is reportedalso a bar related to the relative standard deviation (SD) of thexij values. The sensor demonstrated a resistance resting value of

G. Saggio / Sensors and Actuators A 185 (2012) 53– 58 57

Fig. 9. Relative changes of electrical resistance values of the 2 in. polyester over-lt

auiadco

eu(mrgvv

fwad

ftta

mo[sraltF

kflato

st

Fig. 10. Micro cracks are visible in a SEM image of the electrical conductive carbon-based element which is the surface layer of the Flexpoint sensor. These micro cracks

aminated Flexpoint sensor vs. the angles of bending, only for outward mode sincehis type of sensor do not present inward capabilities.

bout 2.89 �. Under outward bending conditions the resistance val-es pretty linearly increased till about 3.58 � at 90◦, while under

nward bending conditions, it similarly decreased to about 2.24 �t −90◦. Similar results were obtained under all measurement con-itions and no hysteresis was seen in any case. The value of R2 wasalculated for regression analysis, obtaining the interesting resultsf 0.9979 as average.

Let’s compare the results of the measures with the valuesxpected from the theory. In [7], we reported a GFL = 17.8 ± 4. Now,tilizing the two extremes of GFL values, respectively equal to 21.8=17.8 + 4) and 13.8 (=17.8 − 4), in Eqs. (8) or (11), we expected the

easured �R/R values to fall within the two dotted linear lineseported in Fig. 8. As it is evident, the measurement results are inood agreement with the theory, and even the experimental SDalues always remain confined between the extreme theoreticalalues.

The same measured were made with the same sensor but dif-erent pin radius “r” of the hinge (0.8 cm, 1.0 cm and 1.2 cm). Itas found that no meaningful changes were in the �R/R values,

gain in accordance with the theory since Eqs. (8) and (11) are notependant from “r”.

The experiments were then repeated in the same day but in theollowing 10 days too. We found that the SD values remained belowhe 4% within the same day and the same sweep, below 6.5% withinhe same day for all the 10 cycles, and around the 10% consideringll the 10 days of experimentation.

For comparison purpose, we want to refer also to measure-ents relative the aforementioned commercial 2 in., polyester

ver-laminated, sensors by Flexpoint, reported in a previous work12]. The comparison is necessarily not exhaustive, since these sen-ors demonstrated no properties of bi-directionality (meaningfulesults are only for outward mode), and no GFL was given. But, inny case, we could expect, accordingly to the theory, a somewhatinear trend of the �R/R vs. angles function. Differently, the func-ion that fits the data cannot be confined within two strict lines asig. 9 shows, except beyond 40◦.

We believe this can be due to a particular aspect related to thisind of sensors. In fact, a Flexpoint sensor consists of a single thin,exible plastic film coated with a proprietary coating which sep-rates into many micro cracks that open and close accordingly tohe degree the sensor is bent (see Fig. 10). The opening and closingf cracks causes a measurable change in resistance.

Our theory presumes the hypothesis of isotropy both for theubstrate and the coating material. In such a view, the fact thathe Flexpoint sensor offers a �R/R vs. angles linear behavior only

get larger according to the degree the sensor is bent. The opening and closing ofcracks causes a measurable change in resistance.

beyond 40◦ let us suppose that from 0◦ to 40◦ the micro cracks varyin dimension, while just after that value of bending the micro cracksmaintain their shape or change linearly.

6. Conclusions

A novel theory for a mechanical model of flex sensors is here pre-sented. It was tested on sensors used to sense finger movements. Inparticular we used PEDOT:PSS based sensors indigenously designedand fabricated and commercial sensors by Flexpoint too. Themeasurements to obtain �R/R vs. angle pairs, were made by ahome-made set-up realized to mimic the flex-extension capabil-ities of a human finger.

The theory has been developed under conditions of both com-plete or even partial adhesion of the sensor to the finger withbending of the joints, and has been validated with accurate mea-surements.

The results demonstrated that we can expect a �R/R vs. anglefunction to be linear for sensors made of homogeneous, isotropic,constant cross section body. Future work will investigate howthings can change when this hypothesis is no longer verified, andwill investigate commercial sensors in detail.

Acknowledgement

Sincere thanks to the colleague Paolo Bisegna for his interest,ideas and helpful discussions.

References

[1] L.K. Simone, D.G. Kamper, Design considerations for a wearable monitor to mea-sure finger posture, Journal of NeuroEngineering and Rehabilitation 2 (2005)5.

[2] M.A. Saliba, F. Farrugia, A. Giordmaina, A compact glove input device to measurehuman hand, wrist and forearm joint positions for teleoperation applica-tions, in: Proceedings of the IEEE/APS Int. Conf. on Mechatronics and Robotics,Aachen, Germany, September, 2004.

[3] S. Wise, W. Gardner, E. Sabelman, E. Valainis, Y. Wong, K. Glass, et al., Evaluationof a fiber optic glove for semi-automated goniometric measurements, Journalof Rehabilitation Research and Development 27 (4) (1990) 411–424.

[4] R. Gentner, J. Classen, Development and evaluation of a low-cost sensor glovefor assessment of human finger movements in neurophysiological settings,Journal of Neuroscience Methods 178 (2009) 138–147.

[5] F. Lorussi, W. Rocchia, E.P. Scilingo, A. Tognetti, D. De Rossi, Wearable, redun-dant fabric-based sensor arrays for reconstruction of body segment posture,IEEE Sensors Journal 4 (6) (2004) 807–818.

[6] T. Someyal, T. Sakurai, T. Sekitanil, Future prospects of flexible, large-area

sensors and actuators with organic transistor, in: IEEE International ElectronDevices Meeting, 2005, IEDM Technical Digest., 5 December, 2005.

[7] G. Latessa, F. Brunetti, A. Reale, G. Saggio, A. Di Carlo, Piezoresistive behaviour offlexible PEDOT:PSS based sensors, Sensors and Actuators B 139 (2009) 304–309.

5 ctuat

[

[

[

B

Gt

research interests are related to the fields of brain computer interface, biosensors,sensor’s characterization, and human kinematics’ measurements, about which hehas got four patents. Currently he is member of Italian Space BioMedical Society,Principal investigator of a Project from ASI (Space Italian Agency) and of a Projectfrom INAIL (Italian Workers’ Compensation Authority).

8 G. Saggio / Sensors and A

[8] L. Dipietro, A.M. Sabatini, P. Dario, A survey of glove-based systems and theirapplications, IEEE Transactions on Systems, Man and Cybernetics 38 (July (4))(2008) 461–482.

[9] C. Grimaldi, P. Ryser, S. Strassler, Gauge factor enhancement driven by het-erogeneity in thick-film resistors, Journal of Applied Physics 90 (32) (2001)2–327.

10] T.V. Papakostas, N.M. White, Influence of substrate on the gauge factor of poly-mer thick-film resistor, Journal of Physics D: Applied Physics 33 (14) (2000)L73–L75.

11] N.P. Oess, J. Wanek, A. Curt, Design and evaluation of a low-cost instrumentedglove for hand function assessment, Journal of NeuroEngineering and Rehabil-itation 9 (2012) 2.

12] G. Saggio, Electrical resistance profiling of bend sensors adopted to measurespatial arrangement of the human body, in: ISABEL 2011, 4th Proceedings ofthe International Symposium on Applied Sciences in Biomedical and Commu-nication Technologies, October 26–29, Barcelona, Catalonia (Spain), 2011.

iography

iovanni Saggio received the Dr. Eng. degree in Electronic Engineering fromhe University “Tor Vergata”, Rome, Italy, in 1991, and the Ph.D. degree in

ors A 185 (2012) 53– 58

Microelectronic and Telecommunication Engineering, in 1996, from the same Uni-versity. For his Ph.D. degree he carried out research at the Nanoelectronics ResearchCentre, Dept. of Electronics and Electrical Eng., University of Glasgow, Scotland, andat the Cavendish Lab., Dept. of Physics, University of Cambridge, England. From 1991to 1993, he worked with a grant in CNR (Italian Center for Research Counsel), and wasa Visiting Scientist at the Rutherford Appleton Lab., Central Microstructure Facility,Oxford, England. His initial research activities covered the area of nanodevices, sur-face acoustic wave devices, noise in electronic devices. He is currently a Researcherat the University “Tor Vergata”, Rome, Italy. He teaches courses about Electronicsat the Faculty of Engineering (Departments of Informatics, Telecommunications,Mathematics, Automations, Master on Sound Engineer. Master on CBRN Protection)and the Faculty of Medicine (Departments of Medicine and Surgery, Orthopedicsand Traumatology, Neurophysiopathology, Hearing Aid Practitioner). His current