Electrically induced flapping motion of aluminum foil with a high frequency is demonstrated. The flapping motion was recorded by using a high speed camera and characterized by analyzing the tip displacement of the foil. It is found that a critical voltage presents to induce the flapping motion and the vibration frequency depends on the dimensions of the foils as well as the dielectric properties of the supporters for the foil. Induced directional airflow by the flapping motion was also demonstrated here. This study may provide a simple way to realize the two-dimensional flying vehicle in the future.
A highly sensitive flexible piezoelectric material is developed by using a composite nanofibers web of polymer and metal. The nanofibers webs are made by electrospinning a mixed solution of poly(vinylidene fluoride) (PVDF) and silver nanowires (AgNWs) in the co-solvent of dimethyl formamide and acetone. SEM images show that the obtained webs are composed of AgNWs doped PVDF fibers with diameters ranging from 200nm to 500nm. Our FTIR and XRD results indicate that doping AgNWs into PVDF fiber can enhance the contents of beta phase of the PVDF. UV-Vis spectrum shows a slightly red shift at 324 nm and 341 nm after the AgNWs doping into PVDF, proving the presence of interaction between AgNWs and the PVDF polymer chain. The piezoelectric constant d33 of the nanofibers webs tested with a homemade system, reveals a good agreement with FTIR and XRD characteristic, and the highest one is up to 29.8 pC/N for the nanofibers webs containing 1.5% AgNWs, which is close to that of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE), 77/23). This study may provide a way to develop high-performance flexible sensors.
Electrochromism is the phenomenon displayed by some color changing materials when a burst of charge is applied.
Viologens (Vio) are cathodic electrochromic materials, and triphenylamines (TPA) are anodic electrochromic materials.
Here, we reported a new electrochromic compound composed of Vio, TPA and phosphonic acid groups, thus the
molecules can be anchored on electrode, which will lead to faster switching speed and high stability. An electrochromic
device was assembled using the new Vio as primary electrochromes and Prussian blue as secondary electrochromes. The
device exhibits high transparency. In addition, it shows fast switching speed and good stability.
A novel smart goggle with tunable light transmittance was designed, fabricated and characterized in this research. The
developed smart goggle lens was all-plastic based electrochromic (EC) device. The working EC material was a layer of
thin film conducting polymer: poly (3,4-(2,2-dimethylpropylenedioxy)thiophene) (PProDOT-Me2), while the counter
material of the device was a layer of thin film inorganic oxide: vanadium oxide-titanium oxide (V2O5-TiO2) composite,
which serves as an ion storage layer. A transparent electrolyte as the ion transport layer was sandwiched between the
working and counter parts of the device. The whole device was sealed with an UV cured flexible film sealant. The smart
goggle exhibited tunable light transmittance in visible light wavelength (380-800nm), with a maximum contrast ratio at
580nm. Meanwhile, other unique properties include fast switching speed, low driving voltage, memory function (no
power needed after switching, bi-stable), great durability, high flexibility, light weight, and inexpensiveness.
KEYWORDS: Polymers, Dye sensitized solar cells, Solar cells, Atrial fibrillation, Energy harvesting, Organic photovoltaics, Solar energy, Thermoelectric materials, Semiconductors, Nanocomposites
Energy harvesting and storage systems (EHSS) for future AF vehicles are reviewed with emphasis on thermoelectics,
organic materials, specifically, dye-sensitized solar cells and polymer batteries. The organic solar cells include solid-state
organic solar cells and dye-sensitized solar cells (DSSC). The advantages of using such organic EHSS for AF vehicles
are their specific performance, its scalability to larger skin area and low-temperature processing route, thus cost-effective
however, there are several technical challenges preventing us to develop the organic EHSS in a speedy way.
This paper discusses the design, fabrication and characterization of lens for smart sunglasses based on electrochromic
devices. The prepared electrochromic device was fabricated with ITO coated PET plastic. The working EC material film
was poly [3,3-dimethyl-3,4-dihydro-2H-thieno [3,4-b][1,4]dioxepine] (PProDOT-Me2), while the counter layer of the
device was vanadium oxide titanium oxide (V2O5/TiO2) composite film, which serves as an ion storage layer. A solution
type electrolyte as the ionic transport layer was sandwiched between the working and counter layers. The lens exhibited
tuneable shade in visible light wave length, with a maximum contrast ratio at 580nm.
Proposed thin film battery is comprised of a polymer-lithium ion cell material with barrier-layer packaging and
mechanical reinforcing layers. A semi-solid/ solid electrolyte and a mesoporous polymer separator are sandwiched in
between of anode and cathode. A composite film with a carbon nanotube (CNT) network serves as the anode and a
mesoporous transitional metal oxide LixCoO2 as the cathode, where porous metal sheets serve as the current collector.
The CNT network fabrics have high in-plane tensile strength. LiCoO2 is used as the cathode, because the Co atoms do
not migrate to Li layers, so that cathode does not generate flammable gases during charging that create safety problems.
Merit of this study is using the porous metal sheet, which is flexible, lightweight, low electric resistance, high strength
and strong stability in alkaline solution. This paper presented development of electrolyte for laminated polymer lithium
rechargeable battery. Two-type electrolytes, semi-solid and solid, were attempted; high ionic conductivity of Li ion
electrolytes was achieved.
Ionic polymer metal composites based on Nafion and Flemion have attracted great attention as an newly developed
actuator and sensor materials due to their good performance, such as light weight, good flexibility, low actuation voltage,
large strain, good sensitivity. Previous investigations were mostly focused on actuation performance. Recently, we
reported some work on flexible tactile sensors based on Flemion ionic polymer metal composites. In this work, we
expanded the previous single-dome tactile sensor into a three by three arrayed structure. The correlated substrate and
signal collective lines were designed. Several mechanical-electrical relationships on different test domes were obtained
when different mechanical input pulses were applied. According to the experiment results, this tactile sensor arrays could
achieve good special resolution. By further improving signal circuits, a flexible large-area sensing system could be
achieved based on this material. Flemion based ionic polymer metal composites would be a good candidate for
bio-related sensors especially for artificial derma applications.
Electroactive polymers, Nafion and Flemion, have been widely investigated as actuator materials due to their good
performance, such as light weight, good flexibility, low actuation voltage, large strain. However, less research work has
been done on the sensing behaviors of these materials. In this work, we design and fabricate a tactile sensor based on
Flemion with water as solvent. Several mechano-electro relationships were obtained when different mechanical input
pulses were applied. According to the experiment results, Flemion-based composite could survive much longer time as
sensor materials than that as actuator materials in air. By proper design and fabrication, a tactile sensor for potential
three-dimensional sensing could be achieved based on this material. Electroactive based polymers would be a good
candidate for bio-related sensors especially for artificial derma applications.
Five-layer-structured electrochromic glass (window), containing a transparent conductive layer, an electrochromic layer, an ionic conductive layer, an ionic storage layer and a second conductive transparent layer, was fabricated. The electrochromic glass adopts the conjugated polymer, poly[3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine] (PProDOT-Me2), as a blue electrochromic active layer, vanadium pentaoxide film as an ion storage layer and polymer gel electrolyte as the ionic transport layer. Dimension of smart glass up to 12 x 20 inch was developed. UV curable sealant was applied for the sealing devices. Color changing or switching speed of 12 x 20 inch smart glass from dark state to the transparent state (or vise versa) is less than 15 seconds under applied 1.5 voltages. Besides the long open circuit memory (the colored state or transparent state remains the same state after the power is off), the smart window can be adjusted easily into the intermediate state between the dark state and the transparent state by just simply turn the power on or off. No space consuming or dirt collecting shades, curtains or blinds are needed. The applications of the smart window, e.g. in the aircrafts, automobiles and architectures were discussed as well.
A perfluorinated carboxylic acid membrane, i.e. Flemion, shows improved performance as actuator material compared with Nafion (perfluorinated sulfonic acide). Flemion has a higher ion exchange capacity and good mechanical strength. Especially, Flemion will deform with no back relaxation when applied electrical stimulus. However, with water as solvent, the operation of Flemion in air has serious problems. Since water would evaporate quickly in air. Moreover, the electrochemical stability for use in water is around 1V at room temperature. In previous work, investigations on Nafion with ionic liquid as solvents have been carried out and good results have been obtained. In this work, we explore the use of highly stable ionic liquid instead of water as solvent in Flemion. Experimental results indicate that Flemion based actuators with ionic liquid as solvent have improved stability as compared to the water samples. Although the forces exhibited by Flemion based actuators with the use of ionic liquid decreased dramatically as compared to water, these preliminary results suggest a good potential for use of Flemion with ionic liquid in some applications.
The preparation and characterization of a type of ECD which was based on a cathodic EC polymer film, Poly [3, 3-dimethyl-3, 4-dihydro-2H-thieno [3, 4-b][1, 4] dioxepine] (PProDOT-Me2) is reported. A typical device was constructed by sandwiching a gel electrolyte between a PProDOT-Me2 EC film deposited on Indium Tin oxide (ITO) coated glass and a counter electrode which was also ITO glass coated by a Vanadium oxide (V2O5) thin film. The ECD has been characterized. Device contrast ratio, measured as Ε%T, was equal to 60%, and ranged from 2% to 62% between the colored and bleached state measured at 580 nm. A lifetime of over 100,000 cycles between the fully oxidized and fully reduced state has been achieved with only 6% change in the transmittance. The switching speed of a 2.5cm x 2.5cm ECD could be reached in 1 second between the bleached and colored state. The device also has a long open circuit memory. It can remain in the bleached or colored state without being energized for 30 days, and the change in transmittance is less than 6% in colored state. The cyclic voltammetry method was used to detect the moisture content in the gel electrolyte. ECDs of various dimensions were also prepared, 2.5cm x 2.5cm, 7.5cm x 7.5cm, 15cm x 15cm and 30cm x 30cm. The largest scale EC polymer device achieved is 30cm x 30cm. Low sheet resistance ITO glass and a thin-film silver deposition frame were applied to overcome the electric potential drop across the ITO glass surface.
A preparation and characterization of thin film vanadium oxide for use as a transparent ion storage layer/counter-electrode in organic ECDs is reported. A cathodic polymer film, Poly[3,3-dimethyle-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine] (PProDOT-Me2) was used as the electrochromic material. Counter-electrodes were prepared using a sol-gel method and deposited using electrophoresis. Indium Tin oxide (I TO) glass was used as an electrically conductive and transparent substrate. This paper focuses on optimized characteristics complimentary to a PProDOT-Me2 based electrochromic thin film. Gels of vanadium oxide were created from V2O5 powder mixed with hydrogen peroxide (H2O2) and deionized water. Thin films were deposited onto a substrate submerged in the solution and subjected to cyclic voltammetry. Deposition parameters were varied and their effect on counter electrode characteristics investigated. The thin film exhibited a capacitance curve similar to the PProDOT-Me2 based EC film while maintaining a transmittance greater than 60% indicating that V2O5 is a suitable material. The ensuing 1 inch x 1 inch smart window exhibits a change in transmittance of 60% and a lifetime of over 100,000 cycles at a switching speed of 1 second. Larger sized devices of six and twelve inches were successfully prepared and switched between the dark blue and transparent states in less than 15 seconds.
The synthesis, characterization and polymerization of two new electrochromic (EC) monomers based on 3, 4-alkylenedioxythiophene are reported. One is 3, 4-bis-(2, 2, 2-trifluoro-ethoxy)-thiophene which contains electron withdrawing group. Another is 6, 6-dimethy-6, 7-dihydro-5H-4, 8-dioxa-2-thia-6-sila-azulene which contains an electron donating group. Primary experiment results show that the new monomers have potential to form EC materials with new colors after polymerization. Color mixing of two EC polymers with blue and red color was studied. The principle of subtractive color mixing for achieving new color EC materials is also demonstrated.
A comparison of key parameters of seven different gel electrolytes for use in electrochromic devices (ECD) is reported. The ionic conductivity, transmittance, and stability of the gel electrolytes are important considerations for smart window applications. The gel electrolytes were prepared by combining polymethylmethacrylate (PMMA) with a salt and a solvent combination. Two different salts, lithium perchlorate (LiClO4) and trifluorosulfonimide (LiN(CF3SO2)2), and three solvent combinations, acetonitrile and propylene carbonate (ACN and PC), ethylene carbonate and propylene carbonate (EC and PC), and Gamma-butyrolactone and propylene carbonate (GBL and PC) were investigated. Results show that gel electrolytes composed of a LiClO4 and GBL+PC combination and a LiClO4 and EC+PC combination are the best candidates for a smart window device based on its high conductivity over time and various temperatures, as well as its electrochemical stability and high transmittance.
A microwave switch based on EAP presents several advantages. A switch based on Flemion is studied. Flemion a perfluorinated carboxylic acid membrane shows improved performance as actuator material compared with Nafion (perfluorinated sulfonic acid). Flemion has a higher ion exchange capacity and good mechanical strength. In order to get a good Flemion actuator, highly conductive soft gold electrodes with large fractal structure have to be deposited on the membrane. The impregnation reduction technique used for plating requires exchange of a gold complex and reduction by gradual sodium sulfite additions. K+ shows the highest exchange ratio with the gold complex and reducing bath temperatures around 60°C with enough reducing agent present are shown to promote the growth of a gold fractal structure. The resulting material shows an actuation displacement with no relaxation, a key feature for switch applications. A simple mechanical switch based on a flemion actuator is prepared and tested as a microwave switch.
A large contrast ratio and rapid switching EC polymer device which consists of a laminated two-layer structure between two electrodes was prepared. The new design consists of an ITO glass electrode, a cathodic EC polymer film, a gel electrolyte and a counter-electrode that replaces the anodic EC polymer and ITO electrode. Several types of EC polymers, such as, poly[3,3-dimethyl-3,4-dihydro-2H-thieno(3,4-b)(1,4)dioxepine] (PProDOT-(CH3)2) and
poly[3,4-(2,2-dimethylpropylenedioxy)-pyrrole] (PProDOP-(CH3)2) were synthesized as cathodic EC polymers. A carbon-based counter-electrode was prepared for comparison with an Au-based counter-electrode. Screen-printing was utilized for the carbon-based counter-electrode. Lithography and sputtering were used for the Au patterned glass counter-electrodes. Several kinds of polymer gel electrolytes were prepared for solid-state applications. Color change of high contrast ratio of visible light transmittance (>ΔΤ55%)of the device is rapidly obtained (0.5-1s) when even less than 2.5V is applied. The repeatability of color changeable EC polymer windows was estimated by the method of electrochemistry and spectrophotometry. This "smart window" technology can be used in many applications where a rapid
color change between transparent and color states is required.
A new actuator system has been developed. This actuator uses Nafion, a solid electrolyte, in combination with Platinum Copper (Pt-Cu) electrodes and mobile ions of Cu2+ to create much larger actuation displacement at smaller levels of applied voltage (1V or less). This actuator provides bending deformation. Large deformation is provided by electrode reaction of copper. Since this reaction is reversible, Cu electrode is not consumed by using polarity change of applied voltage. This actuation mechanism is different from others. Because the induction of the large deflection of Nafion, the large number of the mobile cations is essential. Although it is possible to induce a large deflection by applying a higher electric field as alternative way, this would introduce the electrolysis of water that is not desired unless the device is always submerged in water. To convert bending deformation to liner actuation, we designed a device using a pair of Nafion actuator, which is termed as loop actuator. This loop actuator can be designed into the device with large force by making parallel array. Solid polymer electrolyte-metal composite actuator contains water inside. Therefore coating that prevents water from evaporation is needed for its use in dry condition.
A large contrast ratio and rapid switching electrochromic(EC) polymer device which consists of laminated two-layer structure between two electrodes was proposed. The new design which only comprises an ITO coated glass electrode, a cathodic poly(3,4-propylenedioxythiophene) derivative (PProDOT-(CH3$2) EC polymer film, a solid electrolyte and an Au-based counterelectrode which replaces anodic EC polymer and ITO electrode. Carbon-based counterelectrode was prepared for comparing with Au-based counterelectrode. Lithography and sputtering were used for Au patterning on glass substrate, while screen printing was used for carbon-based counterelectrode. Covering percentage of Au is less than 20%, in order to keep the electrode high transmittance. We also prepared a solid electrolyte, such as poly(methyl metracrylate)(PMMA) based containing LiClO4 gel electrolyte for solid state applications. A special parafilm was utilized on sealing the assembly device. Color change of high contrast ratio of transmittance (>(Delta) 50% T) of the device is rapidly (0.5-1s) obtained upon applied 2.5V voltage and repeatable (10,000 times). The temperature range under which the switching is stable is wide, -40 degree(s)C ~ 100 degree(s)C. The repeatability of current of EC polymer devices while color change was estimated by electrochemistry.
A fast (0.8sec), large (>10%) and reversible deformation of Poly(vinyl alcohol) gel (PVA) swollen with dimethyl sulfoxide (DMSO) upon electric field was realized, and the maximum observed strain reached quite high 27% (DP2100). St-PVA gels were found to exhibit more stable and reversible deformation than at-PVA gels. Furthermore, we have studied the macroscopic structure of PVA/DMSO gels and its influence on their strain exhibition. Four differently structured PVA/DMSO gels, monolayer, circular, triple-layered and porous, were prepared. Monolayer gel exhibited the highly reproducible strain behavior. The mechanism of electric actuation of PVA/DMSO gel is proposed. Then a design of gel mechanical switch is shown, which exhibited the fast response to the electric field with a large, stable and reversible stretching deformation.
Polyacrylamide hydrogels containing bis-[4- {dimethylamine}phenyl]{4-vinyl-phenyl}methyl leucohydroxide which is so called vinyl derivative of Malachite Green have been studied as color changeable gels. The response times of the color and the volume changes of the gel were measured under 6 and 2 different stimuli, respectively. We found a way to increase their color change speed upon applied electric current (E-current), and designed a gel actuator using Nafion film as a separator between two compartments and as a cation conductor. In addition acrylamide gel swollen with Na2SO4 solution was used as a medium for increasing electric conductivity. We varied the concentration of dvMG in the gel to control the degree of color change. Furthermore, we have studied the influence of gel thickness on the color change rate. In light of the results obtained, we have proposed one device consisting of this color changeable gel.
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