Local deposition of polypyrrole on aluminum by anodizing, laser irradiation, and electrolytic polymerization and its application to the fabrication of micro-actuators

Article abstract of DOI:10.1016/j.electacta.2005.12.049

Polypyrrole was deposited at selected areas on aluminum by anodizing, laser irradiation, and electrolytic polymerization, and the application of the technique for fabricating micro-actuators was attempted. Aluminum specimens covered with porous type anodic oxide films were irradiated with a pulsed Nd-YAG laser to remove the oxide films locally, and then thin Ni layers were deposited at areas where film had been removed. Polypyrrole could be successfully deposited only on the Ni layer by anodic polarization of the specimens in pyrrole monomer solution, and a polypyrrole/Ni bilayer structure could be obtained by dissolution of the aluminum substrate and anodic oxide film in NaOH solutions. The bilayer structure was found to be inactive to doping and dedoping of ions during anodic and cathodic polarization. A three-layer structure, nitrocellulose/Ni/polypyrrole, fabricated by electrolytic polymerization after nitrocellulose coating on a Ni layer detached from the aluminum substrate, showed ion-doping and -dedoping activity, suggesting the possibility of fabricating micro-actuators in this manner.

Full text of DOI:10.1016/j.electacta.2005.12.049

Electrochimica Acta 51 (2006) 4834–4840
Local deposition of polypyrrole on aluminum by anodizing,
laser irradiation, and electrolytic polymerization and
its application to the fabrication of micro-actuators
∗
1
Y. Akiyama, T. Kikuchi , M. Ueda, M. Iida, M. Sakairi, H. Takahashi
Graduate School of Engineering, Hokkaido University, N13 W8 Kita-Ku, Sapporo, Japan
Received 15 September 2005; received in revised form 15 December 2005; accepted 17 December 2005
Available online 17 February 2006
Abstract
Polypyrrole was deposited at selected areas on aluminum by anodizing, laser irradiation, and electrolytic polymerization, and the application of
the technique for fabricating micro-actuators was attempted. Aluminum specimens covered with porous type anodic oxide films were irradiated with
a pulsed Nd-YAG laser to remove the oxide films locally, and then thin Ni layers were deposited at areas where film had been removed. Polypyrrole
could be successfully deposited only on the Ni layer by anodic polarization of the specimens in pyrrole monomer solution, and a polypyrrole/Ni
bilayer structure could be obtained by dissolution of the aluminum substrate and anodic oxide film in NaOH solutions. The bilayer structure was
found to be inactive to doping and dedoping of ions during anodic and cathodic polarization. A three-layer structure, nitrocellulose/Ni/polypyrrole,
fabricated by electrolytic polymerization after nitrocellulose coating on a Ni layer detached from the aluminum substrate, showed ion-doping and
-
©
dedoping activity, suggesting the possibility of fabricating micro-actuators in this manner.
2006 Elsevier Ltd. All rights reserved.
Keywords: Aluminum; Anodizing; Conducting polymer; Electrolytic polymerization; Micro-actuator
1
. Introduction
In the fabrication process of the three-dimensional
microstructures [13], cylindrical and prismatic aluminum bars
covered with anodic oxide film were rotated and moved up-
and down-wards during laser irradiation, and later metals and
acrylic acid resins were deposited electrochemically. After
the metal/acrylic acid resin deposition, the specimens were
immersed in a NaOH solution to lift off the metal- or organic-
layer by dissolution of the aluminum substrate and anodic oxide
film. Free-standing metal/acrylic acid resin structures of cylin-
drical and prismatic network cages, rings, springs, and bellows
were obtained by these processes.
The success of the fabrication of free-standing 3D
microstructures suggested the authors to deposit conducting
polymers locally on these, and to fabricate micro-actuators by a
combination of the techniques described above with electrolytic
polymerization of pyrrole [14]. Actuators based on conducting
polymers, such as polypyrrole (PPy), polyaniline, polythio-
phene, polymethylaniline, poly(3-methylthiophene), poly(i-
methylpyrrole), and polyurethane have been investigated exten-
sively [15–25] for the fabrication of micro-electromechanical
systems (MEMS) and bio-mimetic devices, and among these
actuators polypyrrole-based actuators appear to be the most
The authors have been developing a novel method of micro-
patterning of aluminum using anodizing, laser irradiation, and
electrochemical techniques [1–8]. In the process, aluminum
specimens covered with anodic oxide films are irradiated with a
pulsed Nd-YAG laser to remove the oxide film locally [1], and
then a metal layer is deposited by electroplating [2,3] or electro-
less plating [4–6] at areas where oxide films have been removed
by laser irradiation. An acrylic acid resin was also deposited
locally by electrophoretic deposition after laser irradiation [7].
Local etching and anodizing/dissolution after laser irradiation
enabled the formation of micro-pores and -grooves on the alu-
minum substrate [8]. The authors have recently applied these
techniques to the fabrication of printed circuit boards [9,10],
plastic injection molds [11], micro-reactors [12], and three-
dimensional microstructures [13].
∗
Corresponding author. Tel.: +81 11 706 7112; fax: +81 11 706 7881.
E-mail address: kiku@elechem1-mc.eng.hokudai.ac.jp (T. Kikuchi).
ISE member.
1
0
013-4686/$ – see front matter © 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2005.12.049

Y. Akiyama et al. / Electrochimica Acta 51 (2006) 4834–4840
4835
attractive, due to the high electro-conductivity and high
stability in various media [15]. The principle of actuators
consisting of a bilayer structure of a conducting polymer/non-
conducting organic layer (or metal layer), is based on the
volume expansion of the conducting polymer by ion-doping
into the polymer film and volume shrinkage by ion-dedoping
into electrolyte solutions. The expansion and shrinkage of
the polymer enable the swing of the bilayer actuators by
changing applied potential, since the backing layer does not
change in volume. Micrometer scale actuators are fabricated
preferentially by photolithography with a resist pattern for-
mation and selective polymerization. As photolithography
is seldom applied to materials with three-dimensional (3D)
structures such as rods, spheres, and others, a technique to fab-
ricate 3D micro-actuators without photolithography would be
useful.
Specimens were immersed in Ni2+ solutions in a cell, and set
in a defocused position 5 mm from the focal plane of a laser beam
that had passed through a beam splitter, a pentagonal-shaped iris
diaphragm, a convex lens with 60 mm focal length, and a quartz
window. Details of the laser irradiation setup have been shown
elsewhere [7]. The set specimens were irradiated with 10 mW
of a pulsed Nd-YAG laser (GCR-130-10, Spectra Physics) to
remove the anodic oxide film. The laser used the second har-
monic wave with 532 nm wavelength, 8 ns pulse width, 10 Hz
frequency, and <0.5 mrad beam divergence (full angle). During
the laser irradiation, the specimen was moved at 200 ␮m/s with
a PC-controlled XY-stage to obtain square and mesh patterned
laser-irradiated areas.
The laser-irradiated specimens were polarized cathodically
for 10–20 min at constant potentials between −1.0 and −1.1 V
and 293 K in the Ni2 solutions which had been used for the laser
irradiation [2]. A Pt plate was used as the counter electrode and
a saturated KCl-Ag/AgCl electrode as the reference electrode
for the Ni electroplating.
+
The present investigation used a micro-patterning technique
in the fabrication of PPy micro-actuators by aluminum anodiz-
ing, laser irradiation, and pyrrole electrolytic polymerization.
2
.3. Fabrication of the bilayer structure of polypyrrole/Ni
2
. Experimental
layers
2
.1. Specimens and anodizing
The bilayer structure of polypyrrole and Ni layers was fabri-
cated through two processes (Fig. 1). In Process-A, electrolytic
polymerization was carried out before separating the bilayer
structure from the aluminum specimen, while, in Process-B,
polypyrrole was deposited on the Ni layer after lifting it off
the aluminum specimen.
InProcess-A, theNi-depositedaluminumspecimenwassetin
de-aerated 0.1 M HNO3/0.2 M pyrrole solution at room temper-
ature, and anodically polarized for 10–120 min at 0.55–0.65 V
Highly pure aluminum plate (99.99 wt.%, 0.35 mm thick,
2
0 mm × 18 mm with a handle, Nippon Light Metal) was used
as the specimens. The specimens were degreased ultrason-
ically in C2H OH for 10 min, and then electropolished in
5
1
3.6 M CH3COOH/2.56 M HClO4 solution at 28 V and 280 K.
After electropolishing, the specimens were anodized in 0.22 M
COOH)2 solution at 293 K for 30 min with a constant current
(
−
2
of 100 A m to form 9 ␮m thick porous type oxide films. The
anodized specimens were immersed in 0.029 M alizarin red S
dying solution at 323 K for 5 min, and then boiled in doubly
distilled water for 15 min to seal the pores.
(versus Ag/AgCl) to deposit PPy films on the Ni metal layer.
Structural changes in the specimens by electrolytic polymer-
ization were examined by confocal scanning laser microscopy
(CSLM: 1SA21, LASERTEC). For the observations of the ver-
tical cross-sections of specimens, they were embedded in epoxy
resin and polished mechanically. Finally, the specimens were
immersed in 3 M NaOH solution at room temperature for 30 min
to dissolve the aluminum substrate and oxide films. The fabri-
cation process of the PPy/Ni bilayer microstructure is shown in
Fig. 1 (Process-A).
2
.2. Laser irradiation and local Ni plating
Two kinds of Ni2+ ion solution were prepared for laser irradi-
ation and Ni electroplating. Solution I was composed of 0.31 M
NiSO4 and 0.40 M H3BO3, and Solution II of 1.0 M NiSO4,
0
.5 M H3BO3, 0.2 M NiCl2, and additives of saccharin sodium
In Process-B, Ni-deposited aluminum specimens were
immersed in 3 M NaOH at room temperature for 30 min to dis-
solve the aluminum substrate and oxide films. One surface of
the Ni metal layer obtained in this manner was covered with a
nitrocellulose film by painting one surface of the specimen with
a nitrocellulose/ethyl acetate solution with a brush. The Ni metal
film, one side of which had been shielded with nitrocellulose,
was polarized anodically in 0.1 M sodium dodecylbenzensul-
fate (NaDBS)/0.2 M pyrrole solution at room temperature for
and 2-butyne-1,4-diol (see Table 1).
Table 1
The compositions and operating conditions of Ni electroplating
Composition/condition
Solution I
Solution II
NiSO4 (M)
H3BO3 (M)
NiCl2 (M)
Saccharin sodium (M)
0.31
0.40
–
–
–
1.0
0.50
0.20
0.01
0.0025
120 min at 0.60 V (versus Ag/AgCl) to obtain PPy films on the
2
-Butyne-l,4-diol (M)
uncovered Ni metal layer side (see Fig. 1, Process-B).
pH
3.40
293
2.06
293
−1.0
10
Cyclic voltammograms of the two- and three-layer struc-
tures obtained by Process-A and -B were measured in 0.1 M
NaDBS solution, at a potential scanning rate of 5 mV/s
between 0.4 and −0.8 V (versus Ag/AgCl), and the motion of
Temperature (K)
Potential (vs. saturated Ag/AgCl) (V)
Plating time (min)
−1.1
20

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Y. Akiyama et al. / Electrochimica Acta 51 (2006) 4834–4840
Fig. 2. Change in anodic current density, ia, with potential, E, in 0.1 M
HNO3/0.2 M pyrrole solution using Ni electrodeposited specimens after anodiz-
ing, laser irradiation, and Ni electroplating.
following reaction:
(
1)
−
During the electrolytic polymerization of pyrrole, NO3 ions
are considered to become doped into the PPy film.
Fig. 3 shows CSLM two-dimensional contrast images of the
surface of Ni layers polarized at (a) E = 0.55 V, (b) E = 0.60 V,
Fig. 1. Fabrication of PPy microstructures by anodizing, laser irradiation,
Ni/PPy electrodeposition, and dissolution of the aluminum substrate and oxide
films.
a
a
and (c) Ea = 0.65 V for ta = 15–20 min in 0.1 M HNO3/0.2 M pyr-
role solution. At Ea = 0.55 V (Fig. 3a) and 0.6 V (Fig. 3b), the
whole Ni layer surface is uniformly covered with black, adhe-
sive PPy film, and the surface of the PPy films becomes rougher
at higher potentials. However, at Ea = 0.65 V, the PPy film is
removed locally from the Ni metal layer after drying the speci-
mens, due to poor adhesion.
the microstructures was recorded on video during the cyclic
voltammetry.
3
. Results and discussion
Fig. 4 shows a CSLM contrast image of the cross-section
of a specimen at the laser-irradiated area after polarization at
Ea = 0.60 V for 30 min in 0.1 M HNO3/0.2 M pyrrole solution.
The CSLM image shows a four layer structure: aluminum sub-
strate, Ni-deposited layer, PPy layer, and epoxy resin. The PPy
layer/epoxy resin and Al/Ni layer interfaces are traced with
white and black lines to show their boundaries. It can be seen
from Fig. 4 that the interface between aluminum substrate and
Ni metal layer is relatively rough due to laser ablation of the
aluminum substrate during laser irradiation, and that, on the alu-
minum, there is a 14 ␮m-thick Ni layer with a surface roughness
similar to that at the Al/Ni interface. Fig. 4 also shows that an
about 30 ␮m-thick PPy layer is deposited on the Ni layer, and
that the surface roughness of the PPy layer is much higher than
that of the Ni layer.
3
.1. Deposition of PPy on the Ni-deposited layer
Fig. 2 shows the anodic polarization curve, the ia versus E
curve, obtained at a 2 mV/s scanning rate in 0.1 M HNO3/0.2 M
pyrrole solution at room temperature on the aluminum specimen
after anodizing, laser irradiation, and Ni electroplating. Here, the
specimen was irradiated with the laser to obtain a 3 mm × 3 mm
filmremovedarea, and thenthis area was covered witha Ni metal
layer by cathodic polarization in Solution I. The ia value shows a
peak at E = 0.10 V, and very small values at E = 0.30–0.55 V. The
ia peak of at 0.10 V corresponds to active dissolution of Ni metal,
while the small current between 0.30 and 0.55 V corresponds to
the passive current on Ni. At potentials above E = 0.55 V, the ia
rapidly increases at more positive potentials, accompanied by
changes in color from gray to black at the Ni-deposited area,
suggesting the deposition of PPy. In the Ea > 0.55 V region, PPy
is deposited electrochemically on the Ni layer according to the
Fig. 5 shows the changes in the thickness of the PPy layer, δ,
with polarization time, ta, at Ea = 0.60 V in 0.1 M HNO3/0.2 M
pyrrole solution. The δ increases rapidly in the initial period, and
then increases linearly with ta at a rate of about 40 ␮m/h.

Y. Akiyama et al. / Electrochimica Acta 51 (2006) 4834–4840
4837
Fig. 4. CSLM contrast image of a vertical cross-section of a specimen at an area
with deposited PPy.
from Fig. 6a, PPy is deposited only at the laser-irradiated area,
clearly suggesting that the anodic oxide films are very stable
during the Ni plating and PPy deposition, and that they can be
used as templates.
Fig. 6b shows a photograph of the PPy/Ni bilayer microstruc-
ture after immersing the PPy-patterned specimen (see Fig. 6a)
in 3 M NaOH solution. Fig. 6b clearly shows that the PPy/Ni
bilayer structure can be detached from the specimen.
3.2. Cyclic voltammograms
Fig. 7 shows the cyclic voltammogram at the scanning rate
of 5 mV/s in 0.1 M NaDBS solution at room temperature on a
PPy/Ni bilayer ribbon structure (0.3 mm × 12 mm) fabricated by
Process-A (see Fig. 1b). The electrolytic polymerization for the
formation of PPy layer was carried out at Ea = 0.60 V in 0.1 M
HNO3/0.2 M pyrrole solution. The anodic current, i, increases
Fig. 3. CSLM contrast images of the surface of specimens after laser irradiation,
Ni electroplating, and electro-polymerization for (a) Ea = 0.55 V, (b) Ea = 0.60 V,
and (c) Ea = 0.65 V.
Fig. 6a shows a photograph of the PPy micro-pattern fabri-
cated on the aluminum specimen by anodizing, laser irradiation,
Ni electroplating, and PPy deposition. In Fig. 6a, the black parts
correspond to the PPy-deposited area, and the gray parts to the
anodic oxide film-covered area not subjected to laser irradiation.
The PPy microstructure consists of a mesh-pattern with 120 ␮m
line width in a 9 mm × 3 mm rectangular pattern. As can be seen
Fig. 5. Change in the PPy film thickness, δ, with electro-polymerization time,
ta, in 0.1 M HNO3/0.2 M pyrrole solution.

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Y. Akiyama et al. / Electrochimica Acta 51 (2006) 4834–4840
by scanning the potential in the anodic direction from E = 0 V
up to E = 0.3 V, and during the potential scanning in the cathodic
direction from 0.3 V i decreases, and changes to cathodic current
at about 0 V, showing an increase in the cathodic current with
E down to −0.8 V. The potential scanning in the anodic direc-
tion from E = −0.8 V causes a decrease in the cathodic current,
passing zero at −0.2 V becoming an anodic current. As shown
in Fig. 7, the PPy/Ni bilayer structures fabricated by Process-A
shows some hysteresis in the cyclic voltammogram, suggesting
an electro-inactive state of polypyrrole with only little doping
and dedoping of ions taking place during the potential scanning
between 0.3 and −0.8 V. The motion of the ribbon structure was
examined on video, but no motion could be detected during the
potential scanning.
The cyclic voltammogram of the PPy-deposited specimen
before removal from the Al substrate showed an anodic peak
and a cathodic peak (not shown here), and the electro-inactive
state of the PPy/Ni bilayer structures fabricated by Process-A
is considered to be due to the immersion in NaOH solution.
Osaka et al. [26–29] reported that electro-inactive PPy can be
obtained by electrolytic polymerization in an aqueous alkaline
solution. Inganas et al. [30] found that the conductance of PPy
films decrease drastically after immersion in alkaline solution.
Kuwabata et al. [31] reported that the transition of PPy from
an electro-active state to an electro-inactive state is due to the
disruption of N–H bonds in PPy in alkaline solution. Xie et
al. [32] examined the transition of polypyrrole by in situ FTIR
spectroscopy, and found that some pentacyclic rings in the PPy
chain are opened up after long periods of immersion in alkaline
solutions.
ThetransientofPPytoanelectro-inactivestateduringimmer-
sion of PPy-deposited aluminum specimens in NaOH solution
observed in this investigation can be considered to be due to
−
Fig. 6. Optical micrograph of (a) PPy micro-pattern on an aluminum spec-
imen after anodizing, laser irradiation, Ni electroplating, and PPy electro-
polymerization; and (b) PPy/Ni bilayer microstructure after dissolution of the
aluminum substrate and oxide films.
the influence of OH ions, as reported by the authors above.
De-protonation of PPy by PPy-reduction may be an additional
reason as will be detailed as follows.
When PPy-deposited specimens were immersed in NaOH
solution, the aluminum substrate dissolves according to the fol-
lowing equations:
−
−
−
Al + 4OH = [Al(OH)4] + 3e
3
(2)
(3)
−
−
H2O + 3e = 3OH + (3/2)H2
Eq. (2)istheanodicdissolutionofaluminumandEq. (3)isthe
cathodic reduction of water to evolve H2. The overall reaction
of the aluminum substrate dissolution can be expressed in the
following equation:
−
−
Al + 3H2O + OH = [Al(OH)4] + (3/2)H2
(4)
The counter reaction to Eq. (2) could also be a reduction of
−
PPy, leading to dedoping of NO3 ions:
Fig. 7. Cyclic voltammogram of the PPy/Ni microstructure in 0.1 M NaDBS
solution. The microstructure was fabricated by Process-A.
(5)

Y. Akiyama et al. / Electrochimica Acta 51 (2006) 4834–4840
4839
Fig. 9. Video images of the bending behavior of the PPy/Ni/nitrocellulose
microstructures in 0.1 M NaDBS solution at applied potentials of (a) −0.6 V
and (b) 0.6 V.
Fig. 8. Cyclic voltammogram of the PPy/Ni/Nitrocellulose microstructure in
0
.1 M NaDBS solution. The microstructure was fabricated by Process-B.
volume of PPy to shrink, leading to the bending and twisting of
the microstructure.
Fig. 8 shows the cyclic voltammogram at a scanning rate
The motion induced by the potential switching from −0.6 to
of 5 mV/s in 0.1 M NaDBS solution at room temperature for a
PPy/Ni/nitrocellulose three-layer microstructure fabricated by
Process-B (see Fig. 1). There is an oxidation peak at approx-
imately −0.25 V and a reduction peak around −0.60 V. These
peaks correspond to electrochemical doping/dedoping of sol-
0
.6 V was five times faster than that from 0.6 to −0.6 V. This is
due to the relatively high conductivity of PPy at −0.6 V and the
+
decrease in the conductivity with dedoping (Na )s.
The present investigation showed the fabrication of an actu-
ator consisting of a PPy/Ni/Nitrocellulose three-layer structure,
+
+
vated Na ions, (Na )s, into the PPy film:
(
6)
−
The PPy formed by Process-B are doped with DBS ions,
because electrolytic polymerization of pyrrole has been carried
by successive processes of aluminum anodizing, laser irra-
diation, Ni electroplating, substrate dissolution, and pyrrole
electrolytic polymerization. This result indicates the feasibil-
ity of fabricating micro-manipulators by applying the technique
described here to the three-dimensional microstructures which
have been developed in previous work.
−
out in NaDBS solution. The relatively large size of DBS ions
+
−
causes the doping/dedoping of (Na )s, rather than that of DBS
during the cyclic voltammogram measurements. It can be seen
from Fig. 8 that the nitrocellulose/Ni/PPy three-layer structure
fabricated by Process-B has electro-active properties. This is
due to the electrolytic polymerization occurring after removing
the Ni layer from the aluminum specimen. It is noteworthy that
the current density of the cyclic voltammogram in the electro-
active state is much higher than that in the electro-inactive state
4. Conclusions
The following conclusions may be drawn:
(
comparing Figs. 7 and 8).
Fig. 9 shows photographs illustrating the movement of the
1. Polypyrrole (PPy) can be deposited successfully at selected
areas of aluminum by anodizing, laser irradiation, Ni electro-
plating, and electrolytic polymerization, to form PPy micro-
patterns.
PPy/Ni/nitrocellulose microstructure by switching the applied
potential from (a) −0.6 V to (b) 0.6 V in 0.1 M NaDBS solution.
The microstructure was a 2 mm × 14 mm ribbon connected to
Cu wire with Dotite electro-conductive paste. Fig. 9a shows the
vertical cross-section of the three-layer structure: a PPy layer
2. Microstructures consisting of PPy/Ni bilayers can be fab-
ricated by immersing PPy-deposited specimens in NaOH.
Polypyrrole becomes electro-inactive during immersion in
−
(
left), a Ni layer (middle), and a nitrocellulose layer (right).
NaOH, due to a reaction of PPy with OH ions.
At E = −0.6 V, the ribbon appears like a plain sheet, forming a
thin straight line, while at E = 0.6 V the ribbon bends upwards
and twists clock wise. The potential change from 0.6 to −0.6 V
returned the ribbon to the same shape as in Fig. 9a. This strongly
suggeststhatanodicpolarizationofthemicrostructurecausesthe
3. The PPy/Ni/nitrocellulose three-layer structure can be fab-
ricated by anodizing, laser irradiation, Ni electroplating,
Ni-film detachment, nitrocellulose coating, and PPy elec-
trolytic polymerization. The PPy in the three-layer structure
fabricated in this manner is electro-active, and shows an oxi-

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Y. Akiyama et al. / Electrochimica Acta 51 (2006) 4834–4840
[13] T. Kikuchi, M. Sakairi, H. Takahashi, J. Electrochem. Soc. 150 (2003)
dation current peak at −0.25 V and a reduction current peak
C567.
at −0.60 V in the cyclic voltammogram. A ribbon shaped
[
14] Y. Akiyama, T. Kikuchi, M. Iida, M. Ueda, M. Sakairi, H. Takahashi,
Abstract of the 110th Meeting of Surface Finishing Society of Japan,
PPy/Ni/nitrocellulose structure moves reversibly by chang-
ing the potential from −0.6 to 0.6 V, and vice versa.
2004, p. 150.
[
15] T.F. Otero, H. Grande, J. Rodriguez, Synth. Met. 83 (1996) 205.
References
[16] T.F. Otero, J.M. Sansinena, Adv. Mater. 10 (1998) 491.
[
[
[
17] T.F. Otero, I. Cantero, H. Grande, Electrochim. Acta 44 (1999) 2053.
18] T.F. Otero, I. Boyano, J. Phys. Chem. B 107 (2003) 6730.
19] J.W. Paquette, K.J. Kim, D. Kim, Sens. Actuators A 118 (2005)
[
1] H. Takahashi, K. Nukui, M. Seo, Y. Matsumi, M. Kawasaki, Proceed-
ings of the Symposium on Oxide Films on Metals and Alloys VII,
Electrochemical Society, 1995, p. 50.
135.
[
[
20] J.H. Lee, J.H. Lee, J.D. Nam, H. Choi, K. Jung, J.W. Jeon, Y.K. Lee,
K.J. Kim, Y. Tak, Sens. Actuators A 118 (2005) 98.
[
[
[
[
[
[
[
[
2] M. Sakairi, J. Wakabayashi, H. Takahashi, N. Katayama, J. Surf. Finish.
Soc. Jpn. 49 (1998) 1220.
3] M. Sakairi, Z. Kato, S.Z. Chu, H. Takahash, Y. Abe, N. Katayama,
Electrochemistry 71 (2003) 920.
21] M. Onoda, H. Shonaka, K. Tada, Curr. Appl. Phys.
94.
22] W. Lu, I.D. Norris, B.R. Mattes, Aust. J. Chem. 58 (2005) 263.
5 (2005)
1
[
[
4] S.Z. Chu, M. Sakairi, H. Takahashi, Z.X. Qui, J. Electrochem. Soc. 146
23] M.A. Careem, K.P. Vidanapathirana, S. Shaarup, K. West, Solid State
Ionics 175 (2004) 725.
24] S. Hara, T. Zama, W. Takashima, K. Kaneto, Synth. Met. 149 (2004)
(
1999) 537.
5] S.Z. Chu, M. Sakairi, H. Takahashi, J. Electrochem. Soc. 146 (1999)
876.
[
[
2
1
99.
25] T. Zama, S. Hara, W. Takashima, K. Kaneto, Bull. Chem. Soc. Jpn. 78
2005) 506.
6] S.Z. Chu, M. Sakairi, H. Takahashi, K. Shimizu, Y. Abe, J. Electrochem.
Soc. 147 (2000) 2182.
7] T. Kikuchi, S.Z. Chu, S. Jonishi, M. Sakairi, H. Takahashi, Electrochim.
Acta 47 (2001) 225.
8] T. Kikuchi, M. Sakairi, H. Takahashi, Y. Abe, N. Katayama, J. Elec-
trochem. Soc. 148 (2001) C740.
9] H. Takahashi, M. Sakairi, T. Kikuchi, J. Surf. Sci. Soc. Jpn. 22 (2001)
(
[
[
26] T. Osaka, K. Ouchi, T. Fukuda, Chem. Lett. (1990) 1535.
27] T. Osaka, T. Fukuda, K. Ouchi, T. Nakajima, Denki Kagaku 59 (1991)
1019.
[28] T. Osaka, T. Momma, H. Kanagawa, Chem. Lett. (1993) 649.
[29] T. Osaka, T. Momma, S. Komaba, H. Kanagawa, J. Electroanal. Chem.
3
70.
372 (1994) 201.
[
[
[
10] T. Kikuchi, M. Sakairi, H. Takahashi, Y. Abe, N. Katayama, J. Surf.
Finish. Soc. Jpn. 54 (2003) 137.
11] S.M. Moon, M. Sakairi, H. Takahashi, K. Shimamura, Electrochemistry
[
[
[
30] O. Inganas, R. Erlandsson, C. Nylander, I. Lundstrom, J. Phys. Chem.
Solids 45 (1984) 432.
31] S. Kuwabata, N. Nakamura, H. Yoneyama, J. Electrochem. Soc. 137
7
1 (2003) 260.
(
1990) 2147.
12] H. Takahashi, M. Sakairi, K. Watanabe, T. Kikuchi, M. Yamada, J. Surf.
Finish. Soc. Jpn. 54 (2003) 436.
32] H. Xie, M. Yan, Z. Jiang, Electrochim. Acta 42 (1997) 2361.