Dielectric elastomer actuators (DEA) and bistable electroactive polymers (BSEP) both require compliant
electrodes with rubbery elasticity and high conductivity at large strains. Stretchable opto-electronic
devices additionally require the compliant electrodes to be optically transparent. Many candidate
materials have been investigated. We report a new approach to mechanically robust, stretchable compliant
electrodes. A facile in-situ composite synthesis and transfer technique is employed, and the resulting
composite electrodes retain the high surface conductivity of the original conductive network formed by
nanowires or nanotubes, while exhibiting the mechanical flexibility of the matrix polymer. The composite
electrodes have high transparency and low surface roughness useful for the fabrication of polymer thinfilm
electronic devices. The new electrodes are suitable for high-strain actuation, as a complaint resistive
heating element to administer the temperature of shape memory polymers, and as the charge injection
electrodes for flexible/stretchable polymer light emitting diodes. Bistable electroactive polymers
employing the composite electrodes can be actuated to large strains via heating-actuation-cooling cycles.
Poly(t-butyl acrylate) is a bistable electroactive polymer (BSEP) capable of rigid-to-rigid actuation. The BSEP combines
the large-strain actuation of dielectric elastomers with shape memory property. We have introduced a material approach
to overcome pull-in instability in poly(t-butyl acrylate) that significantly improves the actuation lifetime at strains greater
than 100%. Refreshable Braille display devices with size of a smartphone screen have been fabricated to manifest a
potential application of the BSEP. We will report the testing results of the devices by a Braille user.
Temperature dependant electrical behaviors of cellulose based flexible paper transistor were studied. Due to the
covalently bonded single walled carbon nanotube into cellulose structure (SCBC), the conduction current of SCBC paper
transistor shows two different slopes which is related to the measurement temperature and gate bias voltage of transistor.
The electron hopping mechanism among the covalently bonded carbon nanotube in the regenerated cellulose is discussed
by increasing measurement temperature of SCBC paper transistor.
We report a flexible paper transistor made with regenerated cellulose and covalently bonded single-walled carbon
nanotubes. Functionalized single-walled carbon nanotubes (SWNTs) are reacted with N, N-Carbonyldiimidazoles to
obtain SWNTs-imidazolides. SWNTs can be covalently bonded to cellulose by acylation of cellulose with SWNTsimidazolides.
Using the product, SWNTs covalently bonded cellulose (S/C) composite paper is fabricated and it is
mechanically stretched to align SWNTs with cellulose chains. Finally, inter-digital comb shaped source and drain
electrode and bottom gate electrode is formed on the paper via lift-off process. Aligned SWNTs can contribute to
establishing stable electron channel paths in the cellulose layer. The alignment of SWNTs can be key a role in improving
characteristics of the paper transistor. The characteristics of the paper transistor are evaluated by measuring mobility, onoff
ratio depending on the alignment of SWNTs in S/C composite paper transistors.
A cellulose solution was prepared by dissolving cotton pulp in LiCl/ N,N-Dimethylacetamide (DMAc) solution, and
functionalized multi-walled carbon nanotubes (MWCNTs) were reacted with N, N-Carbonyldiimidazoles to obtain
MWCNTs-imidazolides. By acylation of cellulose with MWCNTs-imidazolides, MWCNTs were covalently bonded
with cellulose chains. Using the product, MWCNTs covalently bonded cellulose composite (M/C) composite was
fabricated with mechanical stretching to align MWCNTs with cellulose. Finally, inter-digital comb electrode was formed
on the composite via lift-off process. Chemo-electrical properties of the M/C composite in response of absorption of the
volatile vapors corresponding to 1-propanol, 1-butanol, methanol and ethanol were investigated. Due to sensitive and
reversible expansion/contraction of the M/C composite matrix in response to absorption of each analyte, the M/C
composite showed fast and reversible change in chemo-electrical property. The ranking of relative resistance response of
the composite was methanol < ethanol < 1-propanol < 1-butanol.
A cellulose solution was prepared by dissolving cotton pulp in LiCl/DMAc solution. Functionalized multi-walled carbon
nanotubes (MWNTs) were reacted with N, N-Carbonyldiimidazoles to obtain MWNTs-imidazolides. By acylation of
cellulose with MWNTs-imidazolides, MWNTs were covalently bonded with cellulose. Using the product, MWNTs-
Cellulose (M/C) composite were fabricated and its characteristics were investigated by FT-IR and Raman spectroscopy,
scanning electron microscopy and Young's modulus. The presence of covalent bonds remarkably enhanced mechanical
property of M/C composite, which improved its actuator performance. The actuator performance of M/C EAPap is
investigated in terms of bending displacement and resonance frequency depending on humidity level.
To improve the piezoelectricity of cellulose electro-active paper (EAPap), electrical field and magnetic field
alignments were investigated. EAPap is made with cellulose by dissolving cotton pulp and regenerating cellulose with
aligned cellulose fibers. EAPap made with cellulose has piezoelectric property due to its structural crystallinity.
Noncentro-symmetric crystal structure of EAPap, which is mostly cellulose II, can exhibit piezoelectricity. However,
EAPap has ordered crystal parts as well as disordered parts of cellulose. Thus, well alignment of cellulose chains in
EAPap is important to improve its piezoelectricity.
In this paper, uniaxial alignments of cellulose chains were investigated by applying electric field and magnetic field.
As exposing different fields to EAPap samples, the changed characteristics were analyzed by X-Ray diffractometer
(XRD) and Scanning electron microscopy (SEM). Finally, the piezoelectricity of EAPap samples was evaluated by
comparing their piezoelectric charge constant [d31]. As increasing applied electric field up to 40V/mm, d31 value was
gradually improved due to increased cellulose crystallinity as well as alignment of cellulose chains. Also the alignment
of cellulose chains was improved with increasing the exposing time to magnetic field (5.3T) and well alignment was
achieved by exposing EAPap sample on the magnetic field for 180min.
Piezoelectricity is one of major actuating mechanisms of a cellulose-based Electro-Active paper (EAPap). Wet drawn
stretching method was introduced in the fabrication process of cellulose film to increase piezoelectricity of EAPap. The
characteristics of wet drawn cellulose were studied by scanning electron microscope (SEM), X-ray diffractogram (XRD)
and pull test. The performance of EAPap was evaluated by measuring bending displacement and piezoelectric charge
constant. The performance of EAPap was sensitive to the fabrication process and material orientation of cellulose film.
Aligning cellulose fibers in the fabrication process was a critical parameter to improve mechanical and electromechanical
properties of EAPap. The experimental results provided that wet drawn stretching is an effective fabrication method to
improve mechanical stiffness and piezoelectricity of EAPap.
Electro-Active Paper(EAPap) actuator materials based on cellulose has been discovered as a smart material that has merits in terms of low voltage operation, lightweight, dryness, low power consumption, bio-degradability, abundance and low price. Since EAPap material requires low power consumption, a remotely driven actuator has been proposed by using microwave power transmission. This concept is attractive for many biomimetic systems such as crawling micro-insect robots, flying objects like dragon fly, and smart wall papers. However, the actuation performance of EAPap is sensitive to humidity. Thus, in this paper, a new EAPap that is less sensitive to humidity is studied. The fabrication of EAPap is explained and the actuations are shown with actuating voltage, frequency, humidity level and time. The fabrication process includes dissolving cellulose fibers, eliminating solvent and Li ions with DI (deionized) water and IPA (Isopropyl alcohol) mixture, washing with water, drying and gold coating. Morphology of the fabricated EAPap is analyzed by taking scanning electron microscope images and X-ray diffractogram. The actuator performance is tested in terms of bending displacement with frequency and humidity level.
Cellulose based Electro-Active Paper (EAPap) is attractive due to advantages in terms of biodegradable, lightweight,
dry condition, large displacement output, low actuation voltage and low power consumption. However, its output force
and actuating frequency band should be enhanced to realize its potential applications. Thus, MWNTs are mixed with
cellulose solution in this paper. To fabricate the cellulose solution, cellulose fibers are dissolved with LiCl/N,N-dimethyl-
acetamide (DMAc) by heating at 150°C. Carboxyl groups functionalized MWNTs (F-MWNT) were used to
make well-dispersion of MWNTs in cellulose matrix. F-MWNTs are dispersed in cellulose solution by sonication for 2
hours. The suspension is spin-coated and pressurized to fabricate an F-MWNT/cellulose EAPap. The prepared F-MWNT/
cellulose EAPap is tested in terms of bending displacement and output force. The actuating performance is compared with MWNT/cellulose EAPap and EAPap only.
Cellulose Electro-Active Paper (EAPap) has potential as a smart material due to its advantages of biodegradability,
lightweight, air actuation, large displacement output, low actuation voltage and low power consumption. However,
improvement of its small output force and low actuating frequency band still remain as drawbacks. In this study,
asymmetrical arrangement of Multi-Walled Carbon Nanotubes (MWNTs) in cellulose matrix was investigated to resolve
drawbacks. Corona discharging technique was used by means of DC electrophoresis of MWNTs in cellulose matrix. To
make MWNTs mixed cellulose EAPap, cellulose fibers were well dissolved in 8%(w/w) LiCl/DMAc (N,N-dimethyl
acetamide) by swelling procedure followed by solvent exchange technique. MWNTs were well dispersed in the cellulose
solution by sonication for 2 hours, and the suspension was spin-coated on an ITO (Indium tin oxide) coated glass, and
high DC electric field was given to the spincoated suspension for 3 hours at 40°C. The structure of MWNT/Cellulose
film was characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and
X-ray diffraction (XRD). It was seen that most of MWNTs were moved and biased toward cathode, and film having
double layer-like structure was made.
Electro-Active Paper (EAPap) materials based on cellulose are attractive for many applications because of their low voltage operation, lightweight, dryness and low power consumption. In addition, EAPap materials are bio-degradable that is important property for artificial muscle actuators as bio-mimetic actuators with controlled properties and shapes. EAPap actuators have been made using cellulose papers coated with thin electrode layers. This actuator showed a reversible and reproducible bending movement. In order to improve both displacement and force of this, complementary conjugated novel material, composed of conductive polymer and carbon nanotubes, is coated on both sides of EAPap. This composite coated EAPap is termed as hybrid EAPap. Used composite consist of multi-walled carbon nanotubes (MWNT) and polyaniline (PANi). It is expected that the use of MWNT can enhance the stiffness of the tri-layered actuator as well as improving the force output. Furthermore, the presence of the MWNT/PANi electrodes may increase the actuation performance of the EAPap material. MWNTs are dispersed in NMP (1-Methyl-2-pyrrolidine), and the resulting suspension is mixed and sonicated with anion doped PANi. Obtained MWNT/PANi/NMP solution is cast on the EAPap by spin coating, and it is dried in a vacuum oven. The effect of processing parameters on the final performance of the composite electrodes is assessed and quantified in terms of the electrical conductivity under dc and ac measurement conditions. The actuation output of the MWNT/PANi/EAPap samples is tested in an environmental chamber in terms of free displacement and blocking force. The performance of the hybrid actuators is also investigated in terms of frequency, voltage and humidity to help shed light on the mechanism responsible for actuation. Comparison of these results in that of the EAPap with PANi and EAPap are also accomplished.
This paper deals with micro-patterning process of EAPap (Electro-Active Paper) for achieving biodegradable and flexible MEMS. EAPap has been known as an active material with an interesting actuation phenomenon of papers. Such active materials were made by depositing very thin electrodes on both sides of cellulose paper strip. When an electric field is applied to the paper strip, a large displacement was produced. This active material has merits in terms of large strain, low voltage, low power consumption, dryness, cheap and biodegradable nature. This material can be designed in such a way that its advantages can be optimized. With these advantages and possibility, this material is attractive for biodegradable and flexible MEMS. This paper reports a micro-patterning process on flexible EAPap material. Key issues in this biodegradable MEMS fabrication with EAPap are 1) the preparation of EAPap material for micro scale fabrication, 2) micro patterning possibility on EAPap and 3) functional capabilities of sensing and actuation. This paper will introduce a micro contact printing for the micro patterning process on the EAPap flexible membrane.
This paper presents a new Electro-Active Paper (EAPap) made by mixing multi-walled carbon nanotubes (MWNTs) with cellulose solution. EAPap material is attractive as smart materials due to its merits in terms of lightweight, dry condition, large displacement output, low actuation voltage, low power consumption and biodegradability. However, there are some challenges in EAPap material in improving and frequency band. For the sake of this, MWNT is mixed in the cellulose solution. This approach will enhance not only the mechanical property but also the electrical property of EAPap material. Cellulose solution is made with non-aqueous solvent, DMAc/LiCl, and MWNT are mixed by stirring and sonicating. The mixed solutions are cast into a sheet form by means of spin coating. Physical and electrical characteristics of these samples are examined via X-Ray Diffractogram, SEM. The performance of these EAPap materials is tested in terms of tip displacement, blocking force, electrical power consumption with frequency and humidity. An optimal weight ratio of MWNT is investigated to satisfy the goal of materials. From the characterization and performance evaluation results, the actuation mechanism of the new EAPap material is addressed.
Electro-Active Paper (EAPap) has been investigated as an attractive EAP material for artificial muscles due to its many advantages such as lightweight, availability, low cost, large displacement output, low actuation voltage and low power consumption. The EAPap is based on cellulose material, and is shown to involve primarily transport of ions in response to an external electric field. Depending on the electrode material, EAPap has shown actuation displacement in the range of 2-4mm, at a few volts. Drawbacks of EAPap actuators include a low force output and a dependence on humidity. To address these limitations, a hybrid EAPap actuator is developed by incorporating an electrode fabricated using single-wall carbon nanotubes (SWNT)/Polyaniline (PANI) with different dopants. SWNT is dispersed in 1-Methy-2-pyrrolidone (NMP), and the resulting solution is used as a solvent for PANI and the various dopants. The SWNT/PANI/NMP solution is then deposited on the EAPap by spin coating. The coated EAPap is dried in a vacuum oven. Raman spectroscopy, X-Ray diffractometry and SEM tests are taken to confirm that the SWNT/PANI/dopant electrode material is successfully prepared by in situ polymerization. The actuation output of the SWNT/PANI/EAPap samples is tested in an environmental chamber in terms of free displacement and blocked force. When the SWNT/PANI/Cl- coated hybrid actuator is excited with 7Vp-p, a maximum displacement of 3.1mm and a maximum power output of 0.29mW are obtained. The hybrid actuator shows an improved actuation force as a result of enhanced stiffness of EAPap.
The application of electroactive polymer devices requires the availability of their properties at various operating conditions. This in turn necessitates a structure-property relationship based on an in-depth understanding of the underlying mechanism responsible for their strain-field response. Cellulose-based Electro-Active Paper (EAPap) has been studied as an attractive EAP material for artificial muscles due to its low cost, availability, lightweight, large displacement output, low actuation voltage and low power consumption. The understanding of the actuation mechanism of this material is important in order to improve the performance and also to better target the application. So far, based on the structure and processing of cellulose-based EAPap, it is believed that two actuation mechanisms are possible: ion transport and dipolar orientation. To physically investigate the actuation mechanism of EAPap, several tests are performed. X-ray diffractogram study exhibits that EAPaps have more amorphous parts than raw cellulose fibers, and there is some possibility of structural change during activation. NMR study shows that the cellulose paper is an ordered structure. TSC current showed a linear relationship with poling electric field, indicating dipolar orientation. . Impedance analysis of EAPap showed an evidence of ionic migration effect. Thus, we conclude that there can be piezoelectric effect and ionic migration effect at the same time associated with dipole moment of cellulose paper ingredients. The amount of these effects may be depending on environmental condition. Quantitative investigation of these two effects on EAPap should be followed with environmental condition.
The construction of electromechanical actuator has been achieved by using the conducting polypyrrole films deposition onto a gold-coated cellophane paper. This is probably the first report of this type of paper actuator. The conducting polypyrrole was electro-generated using either galvanostatic or potentiostatic conditions at 0.5 mA/cm2 current density or 0.7 volts applied potential. The two types of actuators were constructed namely: 1.Ppy/Cellophane bilayer 2. Ppy/ Cellophane paper /Ppy trilayer using electrochemical technique. These actuators showed a reversible and reproducible displacement in acetonitrile solution containing LiClO4 (1M). The maximum displacement of 9.1 mm was recorded for tri-layer device and 3.5 mm for bi-layer device in 1M LiClO4 acetonitrile solutions. The prepared actuator devices were investigated for their mechanical actuation in air medium. The actuation in air is comparatively less than in solution actuation, but still it showed significant movement in air also. The results obtained in acetonitrile solution containing 1M LiClO4 shows that the actuator requires very low excitation voltages of 0.2 MV m-1 at 0.5 Hz frequencies. The effect of humidity on the actuation properties was addressed. The humidity measurement was carried out between 60% to 95% humidity with the help of humidity-temperature controlled chamber. The resonating frequency of 3 Hz at 6 volts had shown 1.8 mm displacement at 95% humidity for gold-coated cellophane sample without polypyrrole.
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