Electro-active Paper Actuator Research Articles

A highly flexible, renewable and green alginate polymer for electroactive biological gel paper actuators reinforced with a double-side casting approach

Biological gel paper actuators (BGPAs) constitute a rising class of electroactive smart artificial muscles with the advantages of large deformation and high energy density at low cost, and they are extensively used in areas such as soft robots, aerospace applications, and biomedical engineering. In this study, a double-side casting process and evaluation methods were proposed for manufacturing electroactive BGPAs and testing their output force characteristics. Furthermore, the effect and optimization mechanism of the double-side casting temperature on the output force performance and electrically activated mechanochemical behavior of a BGPA were studied in depth under single-cycle and repeated work periods. The experimental results demonstrated that when the casting temperature was 50 °C, various hydrogel membranes of BGPAs had optimal connections, with a penetration thickness of 6 μm, which reduced the interfacial contact resistance and drastically increased the quantity of interlayer hydrated ions. Moreover, the specific capacitance of this BGPA reached a maximum at 551.34 mF/g, but its elastic modulus, internal resistance and water loss rate all reached minimum values of 5.934 MPa, 1.91 Ω and 0.176%, respectively. Hence, the ideal values of the working life and output force density were similarly obtained for the BGPA, which were 891 s and 16.249 mN/g, respectively. In general, this optimized high-performance BGPA holds great value for the development and validation of natural smart polymers and engineering solutions.

폴리아닐린이 코팅된 Electro-Active Paper 작동기 성능평가

Bending actuators composed of cellulose with an electrically conducting polymer (CP) are fabricated and their performance is characterized in the air. Two different counter ions, perchlorate and tetrafluoroborate are used as dopant ions in the polyaniline CP processing. CPcellulose- CP trilayer and CP-cellulose bilayer samples are fabricated with different dopant ions, and their actuation performance is evaluated in terms of tip displacement, blocked force and electrical power consumption along with the humidity level and actuation frequency. The trilayer samples substantially enhanced the tip displacement compared to the bilayer ones. The actuation performance of the trilayer actuator is three times better than that of original cellulose electroactive paper (EAPap) actuator. The displacement and blocked force of CP-EAPap actuators are dependent on the humidity and frequency.

Remotely powered and controlled EAPap actuator by amplitude modulated microwaves

This paper reports on a remotely powered and controlled Electro-Active Paper (EAPap) actuator without onboard controller using amplitude modulated microwaves. A rectenna is a key element for microwave power transmission that converts microwaves into dc power through coupling and rectification. In this study, the concept of a remotely controlled and powered EAPap actuator is proposed by means of modulating microwaves with a control signal and demodulating it through the rectenna rectification. This concept is applied to a robust EAPap actuator, namely cellulose–polypyrrole–ionic liquid (CPIL) EAPap. Details of fabrication and characterization of the rectenna and the CPIL-EAPap actuator are explained. Also, the charge accumulation problem of the actuator is explained and resolved by connecting an additional resistor. Since this idea can eliminate the onboard controller by supplying the operating signal through modulation, a compact and lightweight actuator can be achieved, which is useful for biomimetic robots and remotely driven actuators.

Flexible Patch Rectennas for Wireless Actuation of Cellulose Electro-active Paper Actuator

This paper reports a flexible patch rectenna for wireless actuation of cellulose electro-active paper actuator (EAPap). The patch rectenna consists of rectifying circuit layer and ground layer, which converts microwave to dc power so as to wirelessly supply the power to the actuator. Patch rectennas are designed with different slot length at the ground layer. The fabricated devices are characterized depending on different substrates and polarization angles. The EAPap integrated with the patch rectenna is actuated by the microwave power. Detailed fabrication, characterization and demonstration of the integrated rectenna-EAPap actuator are explained.

Highly Durable, Biomimetic Electro-Active Paper Actuator Based on Cellulose Polypyrrole-Ionic Liquid (CPIL) Nanocomposite

Cellulose has received much attention as a emerging smart material, named as electro-active paper (EAPap), which can produce a large bending displacement with applied external electrical field. In spite of many advantages over other reported electro active polymers, there are some issues to be addressed: its actuator performance: (i) sensitive to environmental humidity, (ii) humidity dependent displacement output of the actuator and (iii) degradation of performance with time. In present paper, we have successfully developed the highly durable EAPap actuator working at ambient condition with large displacement output. To improve the performance and durability of EAPap, nanoscaled PPy layer into cellulose EAPap was formed by in-situ polymerization technique. Cellulose-PPy-IL nanocomposite based EAPap actuator showed nearly 100% improvement of the actuator performance compared that of pure cellulose based EAPap actuator systems.

Fabrication and testing of cellulose EAPap actuators for haptic application

Piezoelectric behavior of the cellulose electro-active paper (EAPap) actuators is studied for a possible haptic actuator. Using a thin stretched EAPap film with a material fiber orientation of 45°, stacked and unimorph EAPap actuators are prepared and their performance is investigated as functions of frequency and applied electric field. A small actuation displacement is observed from the stacked EAPap actuator. The displacement of the stacked actuator is dependent on the actuation frequency. The actuation displacement and resonance frequency of the unimorph type EAPap actuators are investigated with different beam lengths. At 1 Hz, the piezoelectric constant d 33 of the 32-layer-stacked EAPap actuator is about 150 pm/V and decreases as the operating frequency increases. A unimorph EAPap actuator with 60 mm length and 10 mm width shows a 75 μm of bending displacement at 10 Hz. From the experimental study, we demonstrate the feasibility of the cellulose EAPap for haptic applications.

The Effect of Residual Ionic Liquid for Cellulose Based Electro-Active Paper Actuator

The cellulose was directly dissolved in 1-butyl-3-methylimidazolium chloride at 80°C. The clear and transparent cellulose solution was cast on the glass substrate using tape-casting method. The cast films were soaked into various solvents such as methanol, methanol-deionized water, deionized water, and isopropyl alcohol-deionized water. UV-visible transmittances were approximately 74% to 50% depending on the curing solvents. High thermal stability was observed for the cellulose film regenerated with high ratio of water content. Using these cellulose films, EAPap actuators were fabricated by coating gold-electrodes on both sides. The resonance frequency shifted to lower frequency as the amount of residual ionic liquids increased. The resonance frequency shift to lower frequency might be due to the hygroscopic nature of the ionic liquids.

Wirelessly driven electro-active paper actuator made with cellulose–polypyrrole–ionic liquidand dipole rectenna

This paper reports a wirelessly driven electro-active paper actuator that consists of a dipolerectenna array, a power control circuit and two cellulose–polypyrrole–ionic liquid (CPIL)electro-active paper actuators. The CPIL nanocomposite actuator was fabricated byincorporating nanoscaled PPy onto cellulose by an in situ polymerization technique, whichwas followed by activation in a room temperature ionic liquid. The CPIL actuator showsits maximum bending displacement of 10 mm at an ambient humidity conditionwith 30 mW electrical power consumption. The CPIL actuator is very stable inits actuator performance. The dipole rectenna array receives microwaves andconverts them to dc power so as to wirelessly supply power to the actuators. Threeflexible dipole rectenna arrays are designed, manufactured and characterized. Therectenna array that has nine rectenna elements generates the maximum power of75 mW. This power was used to successfully activate the two CPIL actuatorsand the control circuit. Detailed fabrication and characterization of the CPILactuator and the dipole rectenna array as well as the control circuit are explained.

An electro-active paper actuator made with cellulose–polypyrrole–ionic liquidnanocomposite: influence of ionic liquid concentration, type of anion and humidity

This paper reports a cellulose–polypyrrole–ionic liquid (CPIL) nanocomposite thatcan produce large actuating displacement in a low humidity environment. Thefabrication process and actuator performance of the CPIL nanocomposite actuator areillustrated. Experimental results revealed that the size of anion, concentrationof ionic liquid and ambient humidity level have a significant influence on theactuator performance of the CPIL nanocomposite. The bending displacement of theCPIL nanocomposite actuator was enhanced with increasing anion size, ionicliquid concentration and humidity level. CPIL nanocomposite made with 4%BMIBF4 ionic liquid exhibited a very large bending displacement with excellentdurability under ambient conditions (30% relative humidity and25 °C). This is probably the first report that cellulose based electro-active paper actuator canexhibit such a large bending displacement under ambient conditions. Experimental resultsrevealed that the proposed CPIL nanocomposite actuator under study can be operated upto 70% humidity level.

Nanocoating of ionic liquid and polypyrrole for durable electro-active paper actuators working under ambient conditions

This paper reports that nanocoating of polypyrrole (PPy) and ionic liquid (IL) on cellulose film improves the electromechanical performance and durability of a cellulose electro-active paper actuator. Cellulose–PPy–IL nanocomposites were fabricated by the polymerization-induced adsorption process of PPy followed by subsequent activation in IL solutions. X-ray photoelectron spectroscopy, transmission electron microscopy and secondary ion mass spectroscopy analyses validated the successful nanocoating of the PPy and IL layers on the cellulose. The results revealed that the cellulose–PPy–IL nanocomposites are suitable for durable bending actuators working under ambient conditions. Preparation, characterization and performance test of the nanocomposites are explained.

Paper Actuators Made with Cellulose and Hybrid Materials

Recently, cellulose has been re-discovered as a smart material that can be used as sensor and actuator materials, which is termed electro-active paper (EAPap). This paper reports recent advances in paper actuators made with cellulose and hybrid materials such as multi-walled carbon nanotubes, conducting polymers and ionic liquids. Two distinct actuator principles in EAPap actuators are demonstrated: piezoelectric effect and ion migration effect in cellulose. Piezoelectricity of cellulose EAPap is quite comparable with other piezoelectric polymers. But, it is biodegradable, biocompatible, mechanically strong and thermally stable. To enhance ion migration effect in the cellulose, polypyrrole conducting polymer and ionic liquids were nanocoated on the cellulose film. This hybrid cellulose EAPap nanocomposite exhibits durable bending actuation in an ambient humidity and temperature condition. Fabrication, characteristics and performance of the cellulose EAPap and its hybrid EAPap materials are illustrated. Also, its possibility for remotely microwave-driven paper actuator is demonstrated.

The preparation, characterization and actuation behavior of polyaniline and celluloseblended electro-active paper

This paper reports polyaniline and cellulose blended electro-active paper(EAPap) that can produce large bending displacement at ambient humidityconditions with long lifetime durability. A novel solution processable polyaniline-p-toluene sulfonate (PANI–PTSA) salt was prepared by an invertedemulsion polymerization technique using benzoyl peroxide andp-toluene sulfonic acid. Cellulose solution prepared by dissolving cotton with lithiumchloride/N, N-dimethylacetamide was mixed with the PANI emaraldine salt solution and acellulose–PANI blended film was obtained. The obtained cellulose–PANI film wascharacterized by ultraviolet–visible (UV–visible), x-ray diffraction, scanning electronmicroscopy and tensile test methods. A cellulose–PANI EAPap actuator was made bydepositing very thin gold electrodes on both sides of the cellulose–PANI film. When theactuator performance of the cellulose–PANI EAPap was evaluated in terms of bendingdisplacement with respect to the actuation frequencies, voltages and relative humiditylevels, a large bending displacement was shown at ambient humidity conditions with longlifetime durability.

Effect of polyethylene oxide–polyethylene glycol content and humidity on performance of electro‐active paper actuators based on cellulose/polyethylene oxide–polyethylene glycol microcomposite

AbstractThe effect of humidity and polyethylene oxide (PEO)–polyethylene glycol (PEG) content on the actuator performance of cellulose/PEO–PEG microcomposites was studied. Upon blending 5% PEO–PEG, the maximum bending displacement of the actuator increased nearly twice compared to that of cellulose EAPap actuator. However, further increase of PEO–PEG content resulted in decreased actuator performance. This might be due to the increased intermolecular interaction by hydrogen bonding that reduces the mobility of the molecules. The actuator performance test showed that the increase in humidity level rather reduced the maximum displacement of the actuators. X‐ray diffractogram and Fourier transform infrared spectrum analysis suggested a structural change of the microcomposites as well as disruption of cellulose/PEO–PEG association attributed to the actuator performance degradation at high humidity level. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

Effect of Electrode Pattern on the Actuator Performance of Cellulose Electro-Active Paper

The effect of electrode patterns on the actuator performance of electro-active paper (EAPap) is studied. A rectangular electrode pattern has been typically used for EAPap actuator. Since the electrical field can be concentrated at the edge of electrodes, the electrode patterns of EAPap can influence the actuator performance. Thus, a fishbone pattern electrode was designed and fabricated on EAPap materials and its actuation characteristics were compared with the rectangular electrode ones. Two EAPap materials, DCell, which is made by dissolving cellulose pulp with N,N-Dimethylacetamide and LiCl followed by curing process, and cellophane were used. Bending displacements and the resonance frequencies of EAPap actuators were investigated. Although the bending displacements of the fishbone patterned EAPap actuators were slightly lower than the rectangular patterned actuators, the resonance frequencies of the fishbone patterned actuators were higher than the rectangular patterned actuators. Electrical field concentration around the edge of fishbone pattern electrode might result in increased bending stiffness of the actuator and electrical power consumption. Electrical power consumption and electrode damage of the fishbone pattern electrode were addressed.

Dry and durable electro-active paper actuator based on natural biodegradable polymer

This article describes a dry and durable electro-active paper (EAPap) actuator based on natural biodegradable polymer: cellulose and chitosan. To fabricate this actuator, cellulose and chitosan were dissolved in trifluoroacetic acid. The solution was cast to form a film followed by depositing thin gold electrode on both sides of the film. The actuator was actuated under AC voltage at an ambient condition by changing the actuation voltage, frequency, and time. The actuator revealed a large bending displacement under low voltage, electrical power consumption at low humidity condition. This cellulose–chitosan blended EAPap actuator is suitable for dry and durable actuator. Details about the fabrication, durability, electrical power consumption, and characteristics as well as morphology of the actuator are explained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effect of Polyelectrolyte Nanocoating on the Performance and Durability of Cellulose Electro-Active Paper Actuator

The effect of Polyelectrolyte nanocoating on a cellulose electro-active paper (EAPap) was investigated to improve the actuator performance and durability of EAPap actuators. Nanocoatings of Poly(styrenesulfonate) (PSS) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) were carried out by immersing cationized cellulose films in to aqueous solutions of PSS and PEDOT:PSS. 2,3-epoxypropyltrimethylammonium chloride was used as cationic reactant. UV-visible spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis showed the successful build up of PSS and PEDOT:PSS nanolayers over the cationized cellulose films. Results revealed that, nanocoating not only improved the durability of the actuators but it also greatly reduced (90%) the energy consumption of the actuators. Preparation, characterization and performance test of the actuators are explained.

Hygrothermal behavior of electro-active paper actuator

Mechanical properties of the electro-active paper (EAPap) actuator were tested to investigate its hygrothermal behavior. Tensile creep behavior was studied with constant load at 30–70% relative humidity ranges and 25–40°C temperature. Creep deformation showed typical trend of abrupt strain increase in a short period followed by steady increase of strain, which resulted from the breakdown of cellulose microfibrils. Dependence on the material orientation of EAPap was observed in the creep tests. As changing the orientation of EAPap samples, the creep resistances were varied. Creep strains and creep strain rates were increased as increasing the relative humidity level at 25°C. However, at the elevated temperature of 40°C, the creep strain rate at secondary creep was not significantly raised under increased relative humidity level from 30% to 50%. The hygrothermal effect by increasing the relative humidity level and temperature on the creep rate was reduced due to the saturated moisture at a higher temperature even with lower humidity level. The activation energy levels for creep were around 607–658 kJ/mol for 30% relative humidity level and 623–671 kJ/mol for 50% relative humidity level depending on the material orientation. Understanding of hygrothermal effect in conjunction with the humidity and temperature provides useful information for the potential nano-bio applications of the EAPap actuator.

Characterization of micro-scale creep deformation of an electro-active paper actuator

The creep deformation process of an electro-active paper (EAPap) actuator wasinvestigated by adapting stepwise dead-weight loading. To understand the deformationmechanism of the EAPap film, including morphological and structural changes, variousloading conditions below yield strength were applied to cellophane EAPap. From thestructural observation, micro-dimples and micro-cracks were detected at applied load lowerthan 10% of yield strength, while they were not found in higher load conditions. It ishypothesized that only short and random fibers in the amorphous region may respond tothe applied stress at the low loading condition, not the fibers in the crystalline area. As aresult, deformation energy at the localized spot accumulated and created micro-defects atthe surface. Meanwhile, fibers in the crystalline region may sustain most of the loads ascreep load increases to a high level. Molecular chains in the fiber may rotate and elongatewith high load. Elongated fibers were observed only at a high level of load. From thestructural change as a function of applied load, a peak shift of crystal orientation wasobserved only in high load conditions by wide angle x-ray measurement. This mayconfirm that creep deformation could give rise to structure changes in EAPap.

Covalently bonded multi-walled carbon nanotubes-cellulose electro-active paper actuator

Covalently bonded multi-walled carbon nanotubes (MWNTs) to cellulose were used to fabricate electro-active paper (EAPap) and its mechanical properties as well as actuator performance were investigated. A cellulose solution was prepared by dissolving cotton pulp in LiCl/ N, N-dimethylacetamide (DMAc) solution. MWNTs were covalently bonded to cellulose by reacting MWNTs-imidazolides with cellulose solution. Using this, MWNTs/cellulose (M/C) EAPap was fabricated with different weight percents of MWNTs. This EAPap was analyzed by Fourier-transform IR, X-ray diffraction and X-ray photoelectron spectroscopy and their Young's modulus was measured. The actuator performance of M/C EAPap was evaluated in terms of bending displacement, resonance frequency and electrical power consumption depending on the weight percent of MWNTs and humidity levels. Due to the presence of covalent bonds between MWNTs and cellulose, the Young's modulus of M/C EAPap was remarkably enhanced more than the MWNTs blended EAPap. The enhanced Young's modulus was strongly associated with the crystallinity change of cellulose. The actuator performance of M/C EAPap was improved also. More explanation about the characteristics, actuation principle and actuator performance of M/C EAPap actuator is addressed.

Dry Electroactive Paper Actuator Based on Cellulose/Poly(Ethylene Oxide)—Poly(Ethylene Glycol) MicroComposite

Cellulose Electroactive Paper (EAPap) is an attractive material to construct biomimetic actuators and MEMS devices due to its lightweight, biodegradability, large displacement, and low actuation voltage. However, the performance of the actuator is sensitive to humidity levels. In this article, cellulose/poly(ethylene oxide) (PEO)—poly(ethylene glycol) (PEG) microcomposites were fabricated for EAPap actuators working at ambient humidity condition, and the effect of different PEO : PEG ratios (0.95 : 0.05 to 0.99 : 0.01) on the actuation behavior was investigated. Based on the bending displacement, power consumption, and durability, 0.95 :0.05 ratio was identified as an optimum ratio of PEO : PEG to blend with cellulose for EAPap actuator. The actuation mechanism of the cellulose/PEO—PEG actuator was addressed.