Layer-by-layer (LbL) films have been produced with poly(o-ethoxyaniline) (POEA), chitosan and chitosan-poly(methacrylic acid) (CS-PMAA) nanoparticles. Because the adsorption of LbL films depends on ionic interactions and H-bonding, optimized conditions had to be established for the growth of multilayer films. Unusually thick films were obtained for POEA and CS-PMAA, thus demonstrating the importance of using chitosan in the form of nanoparticles. These nanostructured films were deposited on chromium electrodes to form a sensor array (electronic tongue) based on impedance spectroscopy. This system was used to detect copper ions in aqueous solutions.

1. IEEE Transactions on Dielectrics and Electrical Insulation Vol. 13, No. 5; October 2006
1070-9878/06/$20.00 © 2006 IEEE
1101
Layer-by-layer Films of Poly(o-ethoxyaniline), Chitosan and
Chitosan-poly(methacrylic acid) Nanoparticles and their
Application in an Electronic Tongue
Carlos E. Borato, Fábio L. Leite, Luiz H. C. Mattoso
Embrapa Instrumentação Agropecuária, CP 741, 13 560-970, São Carlos, SP, Brazil
Rejane C. Goy, Sergio P. Campana Filho
Instituto de Química de São Carlos USP, CP 780, 13 560-970 São Carlos, SP, Brazil
Cláudio L. de Vasconcelos, Cypriano G. da Trindade Neto, Márcia R. Pereira, José L. C.
Fonseca
Departamento de Química, Universidade Federal do Rio Grande do Norte, CP 1662, 59078-970 Natal, RN, Brazil
and Osvaldo N. Oliveira Jr.
Instituto de Física de São Carlos USP, CP 369, 13 560-970, São Carlos, SP, Brazil
ABSTRACT
Layer-by-layer (LbL) films have been produced with poly(o-ethoxyaniline) (POEA),
chitosan and chitosan-poly(methacrylic acid) (CS-PMAA) nanoparticles. Because the
adsorption of LbL films depends on ionic interactions and H-bonding, optimized
conditions had to be established for the growth of multilayer films. Unusually thick
films were obtained for POEA and CS-PMAA, thus demonstrating the importance of
using chitosan in the form of nanoparticles. These nanostructured films were deposited
on chromium electrodes to form a sensor array (electronic tongue) based on impedance
spectroscopy. This system was used to detect copper ions in aqueous solutions.
Index Terms – Electronic tongue, chromium electrodes, films, chitosan nanoparticles,
POEA, impedance spectroscopy.
1 INTRODUCTION
NANOSTRUCTURED films of chitosan, a
polysaccharide obtained from the desacetylation of chitin,
have been fabricated in the last few years for a variety of
applications [1,2]. Chitosan is soluble in acidic media and can
be used to produce layer-by-layer (LbL) films, which have
been employed as sensing units in taste sensors [3], and as
templates for immobilization of enzymes used for biosensing
[4]. The main interest in chitosan in the form of thin films is to
exploit its biocompatibility and ability to complex heavy metal
ions [2], in addition to its strong interaction with cholesterol
[5] and other biomolecules [6]. Nanoparticles of chitosan, on
the other hand, have been used as bactericide and
antimicrobial [7,8] and in the controlled release of drugs,
insulin and albumin [9-11]. In general, chitosan nanoparticles
performed better in inhibiting growth of microorganisms than
raw chitosan [8]. It is therefore important to verify whether
LbL films made of chitosan nanoparticles behave differently
from those of chitosan.
In this paper we compare the behavior of chitosan and
chitosan nanoparticles in LbL films with alternated layers of
poly(o-ethoxyaniline) (POEA), a polyaniline derivative.
POEA is highly stable, easily processed and may have its
conductivity varied widely by doping and dedoping upon
protonation and deprotonation, respectively [12]. It has also
been used extensively in the fabrication of LbL films, where it
normally functions as the polycation for adsorption via ionic
interactions, or even through H-bonding [13]. With the
combination of distinct materials, one may envisage
biospecific recognition in LbL films, which opens up a
number of novel possibilities. Of particular relevance for this
work is the deposition of LbL films that may be used in taste
sensors. We use impedance spectroscopy [14] as the method
of detection with sensing units made of LbL films deposited
onto metallic substrates and immersed in the liquid samples to
be analyzed. The aim is to exploit the high sensitivity provided
by the combination of nanostructured films with an ac
electrical characterization method, which has given excellent
results in distinguishing complex liquids, e.g. wine, coffee,
juices and milk, and in detecting pollutants such as pesticides,
heavy metals and humic substances in waters [15-19]. We also
compare the performance of these sensing units with an array
made of bare chrome electrodes.Manuscript received on 9 May 2006, in final form 9 August 2006.

2. C. E. Borato et al.: Layer-by-layer Films of Poly(o-ethoxyaniline), Chitosan and Chitosan-poly(methacrylic acid) Nanoparticles1102
2 EXPERIMENTAL DETAILS
POEA was synthesized according to the procedures
described by Mattoso et al [20]. Chitin extracted from the
exoskeleton of crabs was submitted to desacetylation [21]
resulting in chitosan with viscosity average molecular weight
(Mv) of 170,000 g/mol and average degree of acetylation
( DA ) of 10%. The dispersion of chitosan nanoparticles (CS-
PMAA) was obtained from a 0.2% chitosan solution in
methacrylic acid (0.5%) using potassium persulfate as initiator
[22]. For the fabrication of LbL films of POEA (0.06%) and
chitosan (0.15%) or chitosan nanoparticles (0.2%), the first
step was to determine an optimized immersion time for the
substrate in the aqueous solutions, which were 3 minutes for
POEA and 8 minutes for chitosan and CS-PMAA,
respectively. The substrates were made of glass cleaned with a
solution of 7:3 H2SO4/H2O2 (v/v) (during 60 min.) and then
with a solution of 5:1:1 H2O/NH4OH/H2O2 (v/v)) (during 40
min.). Film growth on the substrate was monitored by
measuring the UV-VIS. absorption spectra of the substrate +
film, with absorption in the visible region being basically due
to POEA. Before proceeding to film fabrication, the
interaction in solution was investigated by measuring the UV-
VIS. spectra of mixtures of POEA and chitosan or CS-PMAA.
The materials used in the study were combined to generate 10
distinct films. LbL films with 10 bilayers were produced for
POEA alternated with chitosan or with CS-PMAA, where the
POEA solutions had pH 3 or 5. Films were also produced
from mixed solutions of 1:1 POEA/chitosan or POEA/CS-
PMAA, and from a single component, namely POEA, chitosan
and CS-PMAA. The 10-layer films from a single component
could be built, with no alternating layers, because secondary
interactions participated in the adsorption process, in addition
to the ionic interactions. All films were characterized with a
Topometrix 2010 Discoverer atomic force microscopy (AFM),
operating in the contact mode. LbL films of POEA and
chitosan or CS-PMAA were also deposited onto chrome
electrodes for impedance spectroscopy measurements. The
latter were measured with a Solartron 1260 Impedance Gain
Phase Analyser at 200 Hz and bias voltage of 50 mV. These
films were used as sensing units to detect copper ions in
aqueous solution of CuSO4. The detection studies were made
in two different steps, both using two arrangements referred to
as A and B. Each arrangement comprised five sensing units
with double face (i.e. two back-to-back units), resulting in ten
sensing units. Measurements using units with no deposited
films, i. e. bare metal electrodes, were also carried out. Table 1
shows a list of films deposited in each arrangement. The
electrodes for the impedance measurements were either
interdigitated bare chrome electrodes or interdigitated chrome
electrodes coated with the films mentioned in Table 1. The
measurements were taken with the electrodes immersed in the
aqueous solutions.
Two sets of experiments were performed. In the first, higher
concentrations of CuSO4 were used, viz. 1, 5, 10, 20 and
50x10-3
mol/L. The sensing units were immersed in 50 mL of
the solutions, with 20 min. elapsing for reaching equilibrium
before the measurement was taken. Measurements with
distilled water were performed before and after the
experiments with CuSO4 to check whether the electrodes had
been contaminated. Three measurements were taken for each
concentration and, more importantly, the concentration was
chosen randomly for each measurement. That is to say, we did
not obtain the measurements in a growing or decreasing
concentration of CuSO4 to minimize systematic errors. In the
second set of experiments, the aim was to check
reproducibility of the measurements and attempt to determine
whether even lower concentrations of copper could be
detected. This was carried out by pouring 50mL of distilled
water into an acrylic trough constructed especially for
coupling the sensor array. After stabilization, measurements
were taken in pure water at each 20 min. For the 31st
measurement, pure water was added to the sample (i.e. copper
ions were deliberately introduced, but the sample suffered
manipulation). In addition, in some other experiments aliquots
of varying concentrations of CuSO4 were added to pure water
to be compared with the cases where only pure water was
added.
3 RESULTS AND DISCUSSION
The first clear difference between chitosan and the
dispersion of chitosan nanoparticles (CS-PMAA) is observed
in the interaction with POEA in aqueous solutions, as
demonstrated in the spectra of Figure 1. The incorporation of
CS-PMAA causes the absorption of POEA to shift
considerably to lower wavelengths owing to dedoping of
POEA. Indeed, for a pH 3 POEA solution an absorption peak
appears at ca. 780 nm, but as chitosan nanoparticles are added
the peak shifts to ca. 530 nm, which is characteristic of
dedoped POEA. POEA dedoping can be associated with the
“competition” for its positive charges – as POEA was
protonated - with the nanoparticles. Further dedoping or
changes in the oxidation state were also observed for a pH 5
solution of POEA and CS-PMAA, which also shifted to lower
wavelengths. On the other hand, Figure 1b shows that addition
of chitosan solution (not in the form of nanoparticles) into a
pH 3 solution of POEA does not cause any shift. The
absorbance merely decreases as a result of a smaller relative
quantity of POEA in the mixed solution due to a dilution
effect as the amount of chitosan is increased.
The adsorption of POEA in LbL films of chitosan and CS-
PMAA was also markedly different, as a much higher amount
of POEA was adsorbed for CS-PMAA. This effect was
particularly strong for POEA at pH 5 and CS-PMAA at pH 3,
as indicated in Figure 2 and Table 2. For instance, a 10-bilayer
LbL film of POEA/CS-PMAA produced under the conditions
just mentioned was ten times thicker than a similar film with
pH 3 for POEA. Even more surprising was the observation
that LbL films of POEA/chitosan were much thinner, as also
indicated in Figure 2 and Table 2. A visual inspection of LbL
films of POEA/CS-PMAA confirmed the fabrication of very
thick films, which is also consistent with AFM images in
Figure 3 where an unusually large scale appears for the Z-axis
(height). The LbL film for POEA/CS-PMAA is ca. 5 μm
thick, which is atypical for a LbL film. In fact, films obtained
with CS-PMAA – with no alternating layers - are already
thick, which clearly points to the importance of the
nanoparticles for a strong adsorption.

3. IEEE Transactions on Dielectrics and Electrical Insulation Vol. 13, No. 5; October 2006 1103
400 500 600 700 800 900
0.0
0.2
0.4
0.6
0.8
1.0
1.2
λ = 532 nm
λ = 647 nm
λ = 778 nm
Absorbance(u.a.)
Wavelength (nm)
POEA
1:0.2
1:0.5
1:0.7
1:1
1:2
1:4
1:8
nanoparticles
(a)
300 400 500 600 700 800 900
0.00
0.25
0.50
0.75
1.00
λ = 684
700
701
703
703
703
703
705
Absorbance(u.a.)
Wavelength (nm)
POEA
1 : 0.2
1 : 0.5
1 : 0.7
1 : 1
1 : 2
1 : 4
1 : 8
(b)
Figure 1. UV-VIS. spectra of mixtures in different proportions of (a) POEA and CS-PMAA and (b) POEA and chitosan.
Table 1. Arrangements A and B and their corresponding deposited films.
Arrangement A Arrangement B
Sensing unit Film Sensing units Film
1 and 6 doped POEA 1 and 6 Chitosan
2 and 7 dedoped POEA 2 and 7 Chitosan nanoparticles (CS-PMMA)
3 and 8 doped POEA alternated with chitosan 3 and 8
doped POEA alternated with CS-
PMMA
4 and 9 dedoped POEA alternated with chitosan 4 and 9
dedoped POEA alternated with CS-
PMMA
5 and 10 Bare 5 and 10 Bare
0 2 4 6 8 10
0.0
0.2
0.4
0.6
0.8
1.0
1.2
POEA 0.06% pH 3 / nanoparticles 0.2% pH 3
POEA 0.06% pH 5 / nanoparticles 0.2% pH 3
Absorbance(u.a.)
Number of layers
(a)
0 2 4 6 8 10
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Absorbance(u.a.)
Number of layers
POEA 0.06% pH=3
POEA 0.06% pH=5
POEA 0.06% pH=3/nanoparticles 0.2% pH=3
POEA 0.06% pH=5/nanoparticles 0.2% pH=3
(b)
Figure 2. (a) Absorption at the peak vs. number of bilayers for LbL films of POEA and CS-PMAA for two pHs of POEA solution (3 and 5) (b) same as in a),
but including the growth of POEA films deposited onto POEA (no alternating layers).
The roughness is extremely high, almost two orders of
magnitude larger than for a chitosan film (Table 2). The films
with CS-PMAA are also thicker and rougher than POEA films
alternated with any other polyanion reported in the literature.
Also presented in Table 2 are the values for POEA films in
which POEA layers have been deposited on top of already
formed POEA layers, with no alternating material. Such
deposition is possible because – in addition to ionic
interactions – H-bonding plays an important role in the
adsorption of polyanilines [23]. Thicker films are deposited

4. C. E. Borato et al.: Layer-by-layer Films of Poly(o-ethoxyaniline), Chitosan and Chitosan-poly(methacrylic acid) Nanoparticles1104
for solutions of POEA pH 5 since there is little repulsion as
POEA is dedoped. The latter film is also less rough than those
obtained with POEA pH 3. Interestingly, the film for POEA
pH 3 alternated with CS-PMMA is much thicker (30 times)
than the film obtained with the mixture between POEA and
CS-PMMA. It seems therefore that strong adsorption leading
to thick films only takes place if CS-PMMA nanoparticles
form a layer on their own, either in a film with a single
component or alternated with POEA. The growth of a layer
containing CS-PMMA mixed with POEA is constrained,
which inevitably has to do with the interaction with POEA.
Since POEA forms much thinner layers, apparently the
number of embedded CS-PMMA nanoparticles is limited by
the conformation of POEA. Nevertheless, a precise
understanding of such interaction will require further studies.
We also deposited 10-bilayer LbL films onto double-faced
chrome electrodes to form sensor arrays as depicted in Table
1. Impedance measurements were taken at 200 Hz and bias
voltage of 50mV, and the data were treated with an equivalent
circuit analysis. The figure of merit used was the capacitance
of the system. Two sets of experiments were performed, the
first involving higher concentrations of CuSO4, namely (1, 5,
10, 20 and 50x10-3
mol/L). In a second set, to be discussed
later, we checked the reproducibility of the sensing units with
smaller concentrations of CuSO4. With the concentrations
mentioned, each sensing unit could detect and distinguish
between these concentrations. By way of illustration, Figure 4
shows the data for the sensing units of arrangements A and B,
which were taken before and after the films were deposited.
Therefore, sensing units 1 through 4 correspond to bare
chrome electrodes while the other sensing units are labeled
according to the material used in the LbL film. It is seen that
all sensing units are capable of detecting the presence of
varied amounts of copper in the aqueous solutions. Moreover,
identical results were obtained in the measurements with pure
water, before and after a series of experiments, which
indicates that the sensing units can be reused if properly
washed, an important feature for an electronic tongue. Note
also the lower capacitance values for the units with LbL films,
though the ability to detect copper was not affected.
Table 2. Average height (Z) and roughness for 10-bilayer LbL films.
Films Z (nm) Roughness (nm)
doped POEA 39.6 6.27
dedoped POEA 27.8 3.18
CS-PMAA 739.0 96.5
doped POEA alternated with CS-PMAA 412.0 61.3
dedoped POEA alternated with CS-PMAA 5200 645
Chitosan 10.6 1.20
doped POEA alternated with Chitosan 17.9 1.68
dedoped POEA alternated with Chitosan 22 3.01
Doped POEA mixed with Chitosan 22.6 2.53
doped POEA mixed with CS-PMMA 14.5 2.20
(a) (b)
(c) (d)
Figure 3. AFM images of the following films: (a) doped POEA alternated with CS-PMMA nanoparticles pH 3, (b) dedoped POEA alternated with CS-PMMA
nanoparticles pH 3, (c) doped POEA alternated with chitosan pH 3 and (d) dedoped POEA alternated with chitosan pH 3.
1.0µm 1.0µm

5. IEEE Transactions on Dielectrics and Electrical Insulation Vol. 13, No. 5; October 2006 1105
When the responses of the sensing units of a given array
were combined in a Principal Component Analysis (PCA),
clusters are formed for the different copper concentrations, as
shown in Figure 5. PCA is a statistical technique largely used
for feature extraction and is based on the reduction of input
data dimension [24]. It works by processing data variance with
a set of principal components, the first of which presents the
highest variance and provides most of the information to
discriminate the input data. Notably, the first component
corresponds to more than 98% of the variance in three of the
plots, which not only denotes good reproducibility but also
indicates that this component could be taken on its own to
distinguish between the various samples. Indeed, data points
for samples with higher concentrations are progressively
located to the right hand side of the plot, which means that the
first principal component is highly correlated with the ion
concentration in the aqueous solutions. A comparison between
Figures 5a, 5c with 5b, 5d indicates that the distinguishing
ability was practically the same for the arrays before and after
film deposition. We shall discuss this point later on. Having
confirmed that the sensing units could easily detect copper
ions in aqueous solutions at the mM level, we examined the
possibility of going further down in concentration. It is known
that electrical properties are very sensitive to any impurities in
the water, especially when interfaces are analyzed [25], which
is actually the reason for the high sensitivity of the electronic
tongues based on nanostructured films and using impedance
spectroscopy. However, this high sensitivity may lead to
artifacts with nominally identical samples being distinguished
from each other by mere manipulation of the samples. With
these concerns in mind, we conceived experiments with
copper ion concentrations down to the nM level, in addition to
control experiments in which water was added into water.
Figure 6 illustrates some of these results for a bare chrome
sensing unit, from which one can see that for 1 μM of CuSO4
or higher the electrical response is distinguished from that of
water being added into pure water (control experiment). For
concentrations below 1 μM, an effect could also be seen if the
scale for the capacitance was expanded, but then the changes
were within the range of changes in the control experiments.
0.00E+00
2.00E-07
4.00E-07
6.00E-07
8.00E-07
1.00E-06
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69
Measurement number
C(F)
sensor unit 1 sensor unit 2 sensor unit 3 sensor unit 4
1mM
5mM
10mM
20mM
50mM
inicial
water
final
water
(a)
0.00E+00
1.00E-07
2.00E-07
3.00E-07
4.00E-07
5.00E-07
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69
Measurementsnumber
C(F)
POEA pH3 POEA pH5
POEA pH3 alternated with chitosan POEA pH5 alternated with chitosan
inicial
water 1mM
5mM
10mM 20mM
50mM
final
water
(b)
0.00E+00
1.00E-07
2.00E-07
3.00E-07
4.00E-07
5.00E-07
6.00E-07
7.00E-07
8.00E-07
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69
Measurements number
C(F)
unit sensor 1 unit sensor 2 unit sensor 3 unit sensor 4
inicial
water
1mM
5mM
10mM
20mM
50mM
final
water
(c)
0.00E+00
1.00E-07
2.00E-07
3.00E-07
4.00E-07
5.00E-07
6.00E-07
7.00E-07
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69
Measurementsnumber
C(F)
Chitosan CS-PMMA
POEA pH3 alternated with CS-PMMA POEA pH5 alternated with CS-PMMA
inicial
water
1mM
5mM
10mM 20mM
50mM
final
water
(d)
Figure 4. Electric response, taking the film capacitance as figure of merit, for several sensing units immersed into solutions containing copper: (a) arrangement
A without films, (b) arrangement A with films, (c) arrangement B without films and (d) arrangement B with films.

6. C. E. Borato et al.: Layer-by-layer Films of Poly(o-ethoxyaniline), Chitosan and Chitosan-poly(methacrylic acid) Nanoparticles1106
The ability to detect μM concentrations was demonstrated for
sensing units with or without a film deposited, as shown in
Figure 7. Though these results again indicate that bare metal
electrodes may be used for taste sensors, which reduces the cost
considerably, an optimized response may be obtained when
interactions between analyte and film material are strong. This
appears to be the case in Figure 7, for the sensitivity of the
electrode coated with a 10-bilayer LbL film of dedoped POEA
and chitosan was higher than for the bare electrode. Figure 8
shows the distinguishing ability of the sensor arrangement A in
PCA plots, again before (bare electrodes) and after depositing
the LbL films. Similar results were obtained with arrangement
B, whose data are therefore omitted. Consistent with the
conclusions drawn from the results for separate sensing units,
samples with 1 μM of CuSO4 concentrations or above could be
distinguished in all cases, but those with lower concentrations
were lamped together with the data points for pure water. With
regard to the surprising results for the sensing units made of
bare chrome electrodes, two points should be emphasized: i) the
response from nominally identical electrodes varied
considerably, which was actually exploited in obtaining a sensor
array with the same (nominally) electrode materials. In another
paper [26], this has been shown to arise from the morphological
differences among chrome electrodes that were produced by
electrodeposition. The differences appear because the electrical
response basically depends on the interface phenomena. ii) by
the same token, with the interface with the liquid under study
governing the response, the performance of a sensor array made
of bare metal electrodes may equal that of an array produced
with nanostructured films, as indicated here in Figures 4, 5 and
8. There are nevertheless cases in which strong interactions with
the analyte become important, as illustrated in Figure 7 for LbL
films of dedoped POEA alternated with chitosan. Therefore, the
challenge in searching for new materials for electronic tongues
is twofold: one has not only to seek various materials that
respond differently to analytes but also identify materials with
some degree of specificity in their interaction with the analytes.
(a) (b)
(c) (d)
Figure 5. PCA plots for the measurements using arrangements A and B with and without films, in detecting various amounts of copper in water. The copper
concentrations are indicated by differing symbols as given in the inset. PC1 and PC2 in the axes refer to the first and second principal components.

7. IEEE Transactions on Dielectrics and Electrical Insulation Vol. 13, No. 5; October 2006 1107
1.85E-09
1.95E-09
2.05E-09
2.15E-09
2.25E-09
2.35E-09
2.45E-09
1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86
Measurements number
C(F)
water addition copper addition
0,1mM
0,01mM
0,001mM
Figure 6. Monitoring of the electric response for a bare chrome sensing unit,
immersed in water and to which pure water and aqueous solutions containing
copper were added.
2.00E-09
2.50E-09
3.00E-09
3.50E-09
4.00E-09
4.50E-09
5.00E-09
5.50E-09
6.00E-09
6.50E-09
1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86
Measurements number
C(F)
without film with film
0,1mM
0,01mM
0,001mM
0,001mM
0,01mM
0,1mM
Figure 7. Capacitance monitored as increasing amounts of copper solution
were added to the water, for two sensing units: with no film and another with
a 10-bilayer LbL film of dedoped POEA (pH 5) alternated with chitosan film
(a) (b)
Figure 8. PCAs plot for the measurements with arrangement A, including those taken with very small amounts of copper: (a) without film and (b) with
deposited films. The different symbols refer to various concentrations of CuSO4 employed and samples of water, as indicated in the insert. PC1 and PC2 in the
axes refer to the first and second principal components.
4 CONCLUSIONS
We have shown that entirely different LbL films are
obtained when chitosan is used in the form of nanoparticles
(CS-PMAA), for the films are much thicker than when raw
chitosan is employed. In a particular case, where the POEA
solution had pH 5 and CS-PMAA had pH 3, a 10-bilayer film
reached ca. 5μm of thickness, which is unusual for an LbL
film. Interaction between the chitosan nanoparticles in the
dispersion and POEA was proven to be much stronger than for
chitosan, being sufficient to alter the doping state of POEA.
UV-VIS. absorption measurements with mixed solutions of
POEA and CS-PMAA indicated that the latter cause POEA to
be dedoped. The LbL films could also be used in sensing units
to detect copper ions in solution down to the μM level.
Furthermore, we showed that high-performance electronic
tongues could also be obtained with an array of bare chrome
electrodes, which may have important implications in
lowering the costs of such devices.
ACKNOWLEDGMENTS
This work was supported by FAPESP, CNPq, Capes,
Nanobiotec, IMMP/MCT, Embrapa/Labex Program and CT-
Hidro (Brazil).
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Carlos Eduardo Borato was born in São Carlos, Brazil,
in 1975. He received the B. Sc. degree in physics in
2000, and the M.Sc. degree in materials science and
engineering, in 2002, both from the University of São
Paulo. He is completing a Ph.D. Project at the University
of São Paulo on novel materials and electrode systems for
taste sensors.
Rejane Celi Goy was born in Tupã, Brazil, in 1974. She
received the B.Sc. degree in chemistry in 1999, and the
M.Sc. degree in materials science and engineering at the
University of São Paulo (USP), in 2002. She is currently
completing her Ph.D. degree, also at USP, on studies
involving chitosan-based materials (spheres,
microspheres and thin films) for detection and removal
of cooper ions from aqueous solutions.
Fabio de Lima Leite was born in Itanhaém, Brazil, in
1975. He obtained the B.Sc. degree in physics from the
São Paulo State University (UNESP), in 2000 and the
M.Sc. degree in materials science and engineering from
the University of São Paulo, in 2002. Currently, he is a
Ph.D. student in the University of São Paulo, in São
Carlos, and doing research on conducting polymers and
atomic force microscopy at the Agricultural Instrumentation Unit of Embrapa.
Cláudio Lopes de Vasconcelos was born in São Paulo,
Brazil, in 1978. He received the B.Sc. degree in
pharmacy in 2000, and the M.Sc. degree in 2003, both at
the Federal University of Rio Grande do Norte. He has
been working in polymer chemistry and colloids. At the
moment, he is enrolled in a Ph.D. program at the Federal
University of Rio Grande do Norte, with the research
focusing on the study of polyelectrolytes in solution,
stabilization of colloids and adsorption process of
biomacromolecules.
Cypriano Galvão da Trindade Neto was born in João
Pessoa, Brazil, in 1977. He received the B.Sc. degree in
pharmacy in 2000, and the M.Sc. degree in chemistry in
2004, both at the Federal University of Rio Grande do
Norte (UFRN). He is completing a Ph.D. project at the
Chemistry Department of UFRN focused on the study of
permeability and diffusion in membranes of chitosan and
its blends.
Sergio P. Campana-Filho was born in Jau, Brazil, in
1957. He obtained the B.Sc. and M.Sc. degrees in
chemistry from the University of São Paulo, in 1979 and
1985, respectively, and the Ph.D. degree from the
University of São Paulo (USP) in 1990. He is a lecturer
at the Instituto de Química de São Carlos, USP, being an
expert on the chemistry and physical chemistry of
polysaccharides from microbial, vegetable and animal
sources. For the last 16 years, he has been working on
bacterial polysaccharides, cellulose, chitin and chitosan.
His work is focused on the extraction processes, chemical derivatization,
characterization and properties/applications of these polysaccharides and
derivatives.

9. IEEE Transactions on Dielectrics and Electrical Insulation Vol. 13, No. 5; October 2006 1109
Márcia Rodrigues Pereira was born in Rio de
Janeiro, Brazil, in 1963. She graduated in chemical
engineering in 1986 at the State University of Rio de
Janeiro. She got the M.Sc. degree in polymer science
and technology at the Federal University of Rio de
Janeiro on the subject of reinforcing of polyurethane
elastomers (1991). In 1994 she obtained a PhD degree
in chemistry at Durham University (UK) on the
subject of permeability of polymeric membranes. Since 1997 she has been a
lecturer at the Chemistry Department of the Federal University of Rio Grande do
Norte and has been working with polymer membranes, solutions, colloids, and
polyelectrolyte complexes.
José Luís Cardozo Fonseca was born in Angra dos
Reis, Brazil, in 1961. He graduated in chemical
engineering in 1985 at the Federal University of Rio de
Janeiro. At the same university he got the M.Sc. degree
in polymer science and technology on the subject of
viscoelastic behavior of polyurethanes (1990). In 1994
he obtained the Ph.D. degree at Durham University (UK)
on the subject of glow-discharge plasma treatment of
polymer films. Since 1996 he has been a lecturer at the
Chemistry Department of the Federal University of Rio Grande do Norte and has
been working with polymer solutions, colloids, polyelectrolyte complexes, and
membranes.
Osvaldo N. Oliveira Jr. was born in Barretos,
Brazil, in 1960. He obtained the B.Sc. and M.Sc.
degrees in physics from the University of São Paulo,
in 1982 and 1984, respectively, and the Ph.D. degree
from the University of Wales, Bangor, in 1990.
Currently he is an associate professor at the
University of São Paulo, in São Carlos, Dr. Oliveira
has led research into the fabrication of novel materials in the form of ultrathin
films obtained with the Langmuir-Blodgett and self-assembly techniques. Most of
this work has been associated with fundamental properties of ultrathin films with
molecular control, but technological aspects have also been addressed in specific
projects. This is the case of an electronic tongue, whose response to a number of
tastants is considerably more sensitive than the human gustatory system. Prof.
Oliveira Jr. has helped establish the Núcleo Interinstitucional de Linguística
Computacional (NILC), which is a leading institute for natural language
processing of Portuguese. Research and development activities at NILC include
the development of a grammar checker for Brazilian Portuguese, now available
worldwide through Microsoft Word, and participation in the Universal
Networking Language (UNL) Project, sponsored by the United Nations
University.
Luiz Henrique Capparelli Mattoso was born in São
Carlos, Brazil, in 1961. He obtained the B.Sc., M.Sc.
and Ph.D. degrees in materials science from the Federal
University of São Carlos, São Paulo, in 1986, 1988 and
1993, respectively. Within this period he was a visiting
researcher at the Universitè des Sciences et Tecnologies
du Languedoc, Montpellier, and Domaine Universitaire
Saint Martin d´Hères, Grenoble, in France, and
University of Pennsylvania, USA. He was head of the
Research and Development Department of the Instrumentation Research Center
of the Brazilian Corporation for Research in Agriculture – Embrapa. He is
currently a lead scientist on nanotechnology and polymer science at Embrapa,
working in an international cooperation program between Brazil and the
Agricultural Research Service (ARS) of the USDA, in Albany, CA, USA. He
leads several R&D projects funded by government and companies on new uses of
agricultural products in plastics and composites, conducting polymers and taste
sensors, technological applications of natural rubber, the most recent being a
nanotechnology network involving several universities and research institutes in
Brazil in cooperation with USA, France and India.