ABSTRACT There is still emerging need for more effective and technologically simple electrode mat... more ABSTRACT There is still emerging need for more effective and technologically simple electrode materials for low voltage ionic EAP materials. Most extensively used carbon materials for bending and linear actuators are different types of carbon nanotubes. We have used for the electrode layers carbide-derived carbon (CDC) and several carbon aerogels. The differences in actuation performance were analyzed in the context of pore characteristics of carbons, electromechanical and electrochemical (EIS) properties. Quantum chemistry and molecular dynamics simulations were used to analyze in detail the actuation/sensor processes in material.
ABSTRACT This paper presents a realization of a self-sensing ionic polymer-metal composite (IPMC)... more ABSTRACT This paper presents a realization of a self-sensing ionic polymer-metal composite (IPMC) device by patterning its surface electrodes and thus creating separate actuator and sensor parts. The sensor and actuator elements of such device are still electrically coupled through the capacitance and/or conductivity of the ionic polymer. By creating a separate grounded shielding electrode between the two parts, it is possible to suppress significantly the undesired cross-talk from the actuator to the sensor. The paper at hand compares three different methods for separating sensor and actuator parts: manual scraping, machine milling, and laser ablation. The basis of comparison of the methods is the electrical characteristics of the device after realizing the surface patterns and the convenience of manufacturing.
Aqueous electrochemical flow capacitors (EFCs) have demonstrated high-power capabilities and safe... more Aqueous electrochemical flow capacitors (EFCs) have demonstrated high-power capabilities and safety at low cost, making them promising energy storage devices for grid applications. A primary performance metric of an EFC is the steady-state electrical current density it can accept or deliver. Performance prediction, design improvements, and up-scaling are areas in which modeling can be useful. In this paper, a novel stochastic superparticle (SP) modeling approach was developed and applied to study the charging of carbon electrodes in the EFC system, using computational superparticles representing real carbon particles. The model estimated the exact values of significant operating parameters of an EFC, such as the number of particles in the flow channel and the number of electrolytic ions per carbon particle. Optimized model parameters were applied to three geometrical designs of an EFC to estimate their performance. The modeling approach allowed study of the charge per carbon particl...
Polypyrrole/Carbide-derived carbon-based electroactive hybrid films for bending and diametrically... more Polypyrrole/Carbide-derived carbon-based electroactive hybrid films for bending and diametrically expanding actuators
In this work, we address the problem of position control of ionic electroactive polymer soft actu... more In this work, we address the problem of position control of ionic electroactive polymer soft actuators under varying relative humidity conditions. The impact of humidity on the actuation performance of ionic actuators is studied through frequency response and impedance spectroscopy analysis. Considering the uncertain performance of the actuator under varying humidity conditions, an adaptable model using the neural network method is developed. The model uses relative humidity magnitude as one of the model parameters, making it robust to different environmental conditions. Utilizing the model, a closed-loop controller based on the model predictive controller is developed for position control of the actuator. The developed model and controller are experimentally verified and found to be capable of predicting and controlling the actuators with excellent tracking accuracy under relative humidity conditions varying in the range of 10–90%.
Abstract Full polymeric trilayer bending actuators are used as a tool to identify solvent influen... more Abstract Full polymeric trilayer bending actuators are used as a tool to identify solvent influence on the driving reactions. The actuator’s structure includes two opposite polypyrrole-dodecylbenzene sulfonate (PPy-DBS) films interpenetrating a polyvinylidene fluoride (PVdF) central membrane placed between them. The actuators are electrochemically and electrodynamically characterized using parallel video-recording of the angular displacements in four electrolytes with different solvents. Actuation in aqueous (Aq) and ethylene glycol (EG) solutions occurs by reaction-driven exchange of cations while actuation in propylene carbonate (PC) and acetonitrile (AN) solutions is motivated by reaction-driven exchange of anions. The solvent changes the actuation mechanism from reaction-driven cation to reaction-driven anion exchanges. The attained results can be explained if a solvent dependent (different dielectric constants and dipolar moments) shift of the playing intra-molecular forces in those dense polymeric gels during reaction is considered. Reaction-driven ionic exchanges were corroborated by EDX analysis of the oxidized and reduced films. Whatever the solvent, the studied actuators are Faradaic polymeric motors (the described angle is a linear function of the reaction charge) with a large hysteresis due to cooperative osmotic and electroosmotic processes.
With lowering of the elastic modulus, the CDC–POM–PPy composite shows a 20× improved strain respo... more With lowering of the elastic modulus, the CDC–POM–PPy composite shows a 20× improved strain response over PPy/DBS.
Journal of Intelligent Material Systems and Structures, 2014
This article is focused on proposing a unified methodology for automating the measurement procedu... more This article is focused on proposing a unified methodology for automating the measurement procedures of ionic electroactive polymer actuators. The proposed methodology and large-scale automation would make testing ionic electroactive polymer actuators less labor-intensive and allow analyzing many ionic electroactive polymer actuators simultaneously. Defining a clear framework for testing ionic electroactive polymer actuators performance and reliability would make the testing process reproducible and provide better comparison between ionic electroactive polymer actuators of either different or similar classes. Our methodology separates two types of degradation: degradation during operation and spontaneous self-degradation.
We report a fabricating method for ion-conducting carbon electrodes on top of industrially produc... more We report a fabricating method for ion-conducting carbon electrodes on top of industrially produced PVDF membrane by spin-coating. Spin-coating is desirable due to its potential application in large-scale actuator manufacturing and its possibility to produce very thin electrodes. The industrial grade membrane was chosen in order to investigate more accurately the results of spin-coating without considering the deviations present in a hand-made membrane. Spin-coating and surface resistivity measurements via four-point probe were described in further detail. The production process of electrode suspension and suspension dispensing were developed and fine-tuned. The spin coater was programmed to obtain electrodes with uniform electrical properties. The arrangement of the spin coater was slightly altered to remove swelling and bubble formation effects concurrent with usage of the porous membrane. Electrodes produced with the developed method were measured and analyzed. Thickness of the film was measured with micrometer screw gauge and four-point probe was used to measure sheet resistivity, in addition film was studied under scanning electron microscope. In best cases the coefficient of variation for sheet conductivity was 6.2%. For all electrode sheet conductivities the median coefficient of variation was 7%. The thickness of the electrodes varied from 6 to 23 μm. As a proof of concept for the developed method a working actuator with spin-coated electrodes was produced.
Electroactive Polymer Actuators and Devices (EAPAD) 2015, 2015
The research is focused on lifetime and degradation of ionic electroactive polymer actuators (IEA... more The research is focused on lifetime and degradation of ionic electroactive polymer actuators (IEAP). The lifetime measurements were carried out using identical methodology upon the different IEAP types. The experiment conducted with large number of samples shows that two types of degradation have serious effect to the IEAPs: degradation during operation and spontaneous self-degradation. Additionally, two ways of occasional damage decrease their overall reliability. In the scope of the current paper we describe degradation of two different types of IEAP actuators: with carbonaceous electrodes and with conducting polymer electrodes. Nevertheless, the common evolutionary trends, rather than the comparative data analysis or formal statistics of all particular samples, are given. Analyzing the electromechanical and electrical impedances of the samples during their whole lifetime, we have found that observing the electric current gives adequate information about the degradation level of any IEAP actuator. Moreover, tracking this electrically measurable parameter enables detecting the occasional damage of an actuator.
ABSTRACT An investigation is reported into the electrochemomechanical deformation (ECMD) of polyp... more ABSTRACT An investigation is reported into the electrochemomechanical deformation (ECMD) of polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) in the form of freestanding films and deposited onto conductive substrates (chemically fixed poly-3,4-(ethylenedioxythiophene, PEDOT) based on PVdF (poly(vinylidenefluoride)). Linear actuation has been achieved starting from a trilayer bending actuator design with a stretchable middle layer. To allow evaluation of the proposed design, commercially available PVdF membranes were chosen as model material. For bending trilayer functionality, electronic separation of both electrode layers is essential, but in order to obtain linear actuation, the CP layers on either side are connected to form a single working electrode. The PPyDBS free standing films and PPyDBS deposited on PEDOT-PVdF-PEDOT were investigated by electrochemical methods (cyclic voltammetry, square wave potentials) in a 4-methyl-1,3-dioxolan-2-one (propylene carbonate, PC) solution of tetrabutylammonium trifluoromethanesulfonate (TBACF3SO3). This study also presents a novel method of utilizing scanning ion-conductance microscopy (SICM) to accurately examine the electrochemical redox behavior of the surface layer of the linear actuator using a micropipette tip.
Although electroactive materials based on conducting polymers have improved considerably during t... more Although electroactive materials based on conducting polymers have improved considerably during the last two decades, further improvement, especially with regards to strain and speeds are required. Here, we present a novel concept of synthesizing hybrid materials comprising polypyrrole (PPy) and carbonaceous materials in order to increase the performance. Hybrid electroactive films composed of nanoporous amorphous carbon and PPy were successfully electropolymerized. PPy and the carbon materials were integrated to form a continuous film without additional binder which is often an insulator and inevitably reduces the electrical and electrochemical performance. The incorporation of nanoporous carbon in film structure was verified using ATR-FTIR. The redox behavior of PPy/carbon hybrid and PPy films, as well as electrochemical capacitance properties were investigated using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) methods. The conductive polymer-carbonaceous films exhibited good electrochemical reversibility during cycling. The surface morphology of the polymer hybrids were investigated with SEM. The porous structure of PPy/carbon hybrid considerably increases the area of the electrolyte/composite film interface, which is leading to higher electric double-layer capacitance and higher redox capacitance, and leaving adequate working space to assure facile electrolyte penetration and better faradaic utilization of the electroactive PPy.
Electroactive Polymer Actuators and Devices (EAPAD) 2011, 2011
In this work we report an actuator material, that consist of carbon aerogel, 1-ethyl-3-methylimid... more In this work we report an actuator material, that consist of carbon aerogel, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) and poly(vinylidene-co-hexafluoropropylene) (PVdF(HFP)). Actuators were made by using layer-by-layer casting method and they work as a bending actuators. Carbon aerogel is synthesized from 5- methylresorcinol, which is a waste product in oil-shale industry. It makes the material "environmentally green". Carbon aerogels have a very low density and considerable specific surface area. It is generally understood that the large interfacial surface area of electrodes gives rise to better actuation performance; therefore, designing actuators with high specific surface area electrodes is of interest. The assembled three layer actuators require low voltage to operate and work steadily in open air due to non-volatile electrolyte. The electromechanical and electrical characteristics of prepared actuators were examined and compared to our previously reported actuators based on the carbide-derived carbon and activated carbon electrodes. The differences in actuation performance were analyzed in the context of pore characteristics and degree of graphitization of carbons. The gas sorption measurements were performed to characterize pore size distribution. These actuators show high strain, low back-relaxation and low power consumption and they are good for slow-response applications compared to carbon nanotube actuators.
ABSTRACT There is still emerging need for more effective and technologically simple electrode mat... more ABSTRACT There is still emerging need for more effective and technologically simple electrode materials for low voltage ionic EAP materials. Most extensively used carbon materials for bending and linear actuators are different types of carbon nanotubes. We have used for the electrode layers carbide-derived carbon (CDC) and several carbon aerogels. The differences in actuation performance were analyzed in the context of pore characteristics of carbons, electromechanical and electrochemical (EIS) properties. Quantum chemistry and molecular dynamics simulations were used to analyze in detail the actuation/sensor processes in material.
ABSTRACT This paper presents a realization of a self-sensing ionic polymer-metal composite (IPMC)... more ABSTRACT This paper presents a realization of a self-sensing ionic polymer-metal composite (IPMC) device by patterning its surface electrodes and thus creating separate actuator and sensor parts. The sensor and actuator elements of such device are still electrically coupled through the capacitance and/or conductivity of the ionic polymer. By creating a separate grounded shielding electrode between the two parts, it is possible to suppress significantly the undesired cross-talk from the actuator to the sensor. The paper at hand compares three different methods for separating sensor and actuator parts: manual scraping, machine milling, and laser ablation. The basis of comparison of the methods is the electrical characteristics of the device after realizing the surface patterns and the convenience of manufacturing.
Aqueous electrochemical flow capacitors (EFCs) have demonstrated high-power capabilities and safe... more Aqueous electrochemical flow capacitors (EFCs) have demonstrated high-power capabilities and safety at low cost, making them promising energy storage devices for grid applications. A primary performance metric of an EFC is the steady-state electrical current density it can accept or deliver. Performance prediction, design improvements, and up-scaling are areas in which modeling can be useful. In this paper, a novel stochastic superparticle (SP) modeling approach was developed and applied to study the charging of carbon electrodes in the EFC system, using computational superparticles representing real carbon particles. The model estimated the exact values of significant operating parameters of an EFC, such as the number of particles in the flow channel and the number of electrolytic ions per carbon particle. Optimized model parameters were applied to three geometrical designs of an EFC to estimate their performance. The modeling approach allowed study of the charge per carbon particl...
Polypyrrole/Carbide-derived carbon-based electroactive hybrid films for bending and diametrically... more Polypyrrole/Carbide-derived carbon-based electroactive hybrid films for bending and diametrically expanding actuators
In this work, we address the problem of position control of ionic electroactive polymer soft actu... more In this work, we address the problem of position control of ionic electroactive polymer soft actuators under varying relative humidity conditions. The impact of humidity on the actuation performance of ionic actuators is studied through frequency response and impedance spectroscopy analysis. Considering the uncertain performance of the actuator under varying humidity conditions, an adaptable model using the neural network method is developed. The model uses relative humidity magnitude as one of the model parameters, making it robust to different environmental conditions. Utilizing the model, a closed-loop controller based on the model predictive controller is developed for position control of the actuator. The developed model and controller are experimentally verified and found to be capable of predicting and controlling the actuators with excellent tracking accuracy under relative humidity conditions varying in the range of 10–90%.
Abstract Full polymeric trilayer bending actuators are used as a tool to identify solvent influen... more Abstract Full polymeric trilayer bending actuators are used as a tool to identify solvent influence on the driving reactions. The actuator’s structure includes two opposite polypyrrole-dodecylbenzene sulfonate (PPy-DBS) films interpenetrating a polyvinylidene fluoride (PVdF) central membrane placed between them. The actuators are electrochemically and electrodynamically characterized using parallel video-recording of the angular displacements in four electrolytes with different solvents. Actuation in aqueous (Aq) and ethylene glycol (EG) solutions occurs by reaction-driven exchange of cations while actuation in propylene carbonate (PC) and acetonitrile (AN) solutions is motivated by reaction-driven exchange of anions. The solvent changes the actuation mechanism from reaction-driven cation to reaction-driven anion exchanges. The attained results can be explained if a solvent dependent (different dielectric constants and dipolar moments) shift of the playing intra-molecular forces in those dense polymeric gels during reaction is considered. Reaction-driven ionic exchanges were corroborated by EDX analysis of the oxidized and reduced films. Whatever the solvent, the studied actuators are Faradaic polymeric motors (the described angle is a linear function of the reaction charge) with a large hysteresis due to cooperative osmotic and electroosmotic processes.
With lowering of the elastic modulus, the CDC–POM–PPy composite shows a 20× improved strain respo... more With lowering of the elastic modulus, the CDC–POM–PPy composite shows a 20× improved strain response over PPy/DBS.
Journal of Intelligent Material Systems and Structures, 2014
This article is focused on proposing a unified methodology for automating the measurement procedu... more This article is focused on proposing a unified methodology for automating the measurement procedures of ionic electroactive polymer actuators. The proposed methodology and large-scale automation would make testing ionic electroactive polymer actuators less labor-intensive and allow analyzing many ionic electroactive polymer actuators simultaneously. Defining a clear framework for testing ionic electroactive polymer actuators performance and reliability would make the testing process reproducible and provide better comparison between ionic electroactive polymer actuators of either different or similar classes. Our methodology separates two types of degradation: degradation during operation and spontaneous self-degradation.
We report a fabricating method for ion-conducting carbon electrodes on top of industrially produc... more We report a fabricating method for ion-conducting carbon electrodes on top of industrially produced PVDF membrane by spin-coating. Spin-coating is desirable due to its potential application in large-scale actuator manufacturing and its possibility to produce very thin electrodes. The industrial grade membrane was chosen in order to investigate more accurately the results of spin-coating without considering the deviations present in a hand-made membrane. Spin-coating and surface resistivity measurements via four-point probe were described in further detail. The production process of electrode suspension and suspension dispensing were developed and fine-tuned. The spin coater was programmed to obtain electrodes with uniform electrical properties. The arrangement of the spin coater was slightly altered to remove swelling and bubble formation effects concurrent with usage of the porous membrane. Electrodes produced with the developed method were measured and analyzed. Thickness of the film was measured with micrometer screw gauge and four-point probe was used to measure sheet resistivity, in addition film was studied under scanning electron microscope. In best cases the coefficient of variation for sheet conductivity was 6.2%. For all electrode sheet conductivities the median coefficient of variation was 7%. The thickness of the electrodes varied from 6 to 23 μm. As a proof of concept for the developed method a working actuator with spin-coated electrodes was produced.
Electroactive Polymer Actuators and Devices (EAPAD) 2015, 2015
The research is focused on lifetime and degradation of ionic electroactive polymer actuators (IEA... more The research is focused on lifetime and degradation of ionic electroactive polymer actuators (IEAP). The lifetime measurements were carried out using identical methodology upon the different IEAP types. The experiment conducted with large number of samples shows that two types of degradation have serious effect to the IEAPs: degradation during operation and spontaneous self-degradation. Additionally, two ways of occasional damage decrease their overall reliability. In the scope of the current paper we describe degradation of two different types of IEAP actuators: with carbonaceous electrodes and with conducting polymer electrodes. Nevertheless, the common evolutionary trends, rather than the comparative data analysis or formal statistics of all particular samples, are given. Analyzing the electromechanical and electrical impedances of the samples during their whole lifetime, we have found that observing the electric current gives adequate information about the degradation level of any IEAP actuator. Moreover, tracking this electrically measurable parameter enables detecting the occasional damage of an actuator.
ABSTRACT An investigation is reported into the electrochemomechanical deformation (ECMD) of polyp... more ABSTRACT An investigation is reported into the electrochemomechanical deformation (ECMD) of polypyrrole (PPy) doped with dodecylbenzenesulfonate (DBS) in the form of freestanding films and deposited onto conductive substrates (chemically fixed poly-3,4-(ethylenedioxythiophene, PEDOT) based on PVdF (poly(vinylidenefluoride)). Linear actuation has been achieved starting from a trilayer bending actuator design with a stretchable middle layer. To allow evaluation of the proposed design, commercially available PVdF membranes were chosen as model material. For bending trilayer functionality, electronic separation of both electrode layers is essential, but in order to obtain linear actuation, the CP layers on either side are connected to form a single working electrode. The PPyDBS free standing films and PPyDBS deposited on PEDOT-PVdF-PEDOT were investigated by electrochemical methods (cyclic voltammetry, square wave potentials) in a 4-methyl-1,3-dioxolan-2-one (propylene carbonate, PC) solution of tetrabutylammonium trifluoromethanesulfonate (TBACF3SO3). This study also presents a novel method of utilizing scanning ion-conductance microscopy (SICM) to accurately examine the electrochemical redox behavior of the surface layer of the linear actuator using a micropipette tip.
Although electroactive materials based on conducting polymers have improved considerably during t... more Although electroactive materials based on conducting polymers have improved considerably during the last two decades, further improvement, especially with regards to strain and speeds are required. Here, we present a novel concept of synthesizing hybrid materials comprising polypyrrole (PPy) and carbonaceous materials in order to increase the performance. Hybrid electroactive films composed of nanoporous amorphous carbon and PPy were successfully electropolymerized. PPy and the carbon materials were integrated to form a continuous film without additional binder which is often an insulator and inevitably reduces the electrical and electrochemical performance. The incorporation of nanoporous carbon in film structure was verified using ATR-FTIR. The redox behavior of PPy/carbon hybrid and PPy films, as well as electrochemical capacitance properties were investigated using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) methods. The conductive polymer-carbonaceous films exhibited good electrochemical reversibility during cycling. The surface morphology of the polymer hybrids were investigated with SEM. The porous structure of PPy/carbon hybrid considerably increases the area of the electrolyte/composite film interface, which is leading to higher electric double-layer capacitance and higher redox capacitance, and leaving adequate working space to assure facile electrolyte penetration and better faradaic utilization of the electroactive PPy.
Electroactive Polymer Actuators and Devices (EAPAD) 2011, 2011
In this work we report an actuator material, that consist of carbon aerogel, 1-ethyl-3-methylimid... more In this work we report an actuator material, that consist of carbon aerogel, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) and poly(vinylidene-co-hexafluoropropylene) (PVdF(HFP)). Actuators were made by using layer-by-layer casting method and they work as a bending actuators. Carbon aerogel is synthesized from 5- methylresorcinol, which is a waste product in oil-shale industry. It makes the material "environmentally green". Carbon aerogels have a very low density and considerable specific surface area. It is generally understood that the large interfacial surface area of electrodes gives rise to better actuation performance; therefore, designing actuators with high specific surface area electrodes is of interest. The assembled three layer actuators require low voltage to operate and work steadily in open air due to non-volatile electrolyte. The electromechanical and electrical characteristics of prepared actuators were examined and compared to our previously reported actuators based on the carbide-derived carbon and activated carbon electrodes. The differences in actuation performance were analyzed in the context of pore characteristics and degree of graphitization of carbons. The gas sorption measurements were performed to characterize pore size distribution. These actuators show high strain, low back-relaxation and low power consumption and they are good for slow-response applications compared to carbon nanotube actuators.
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