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- Front Matter: Volume 6524
- EAP as Emerging Actuators and Biomimetic Technologies
- Electronic EAP
- Ionic EAP I
- Memorial Honoring of Alberto Mazzoldi
- New and Other EAP I
- New and Other EAP II
- EAP Characteristics and Database
- Ionic EAP II
- Nano and Micro EAP
- Modeling
- Applications of EAP I
- Applications of EAP II
- Applications of EAP III
- Poster Session
Front Matter: Volume 6524
Front Matter: Volume 6524
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This PDF file contains the front matter associated with SPIE Proceedings Volume 6524, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.
EAP as Emerging Actuators and Biomimetic Technologies
How fish swim: flexible fin thrusters as an EAP platform
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Fish are capable of remarkable locomotor performance and use their fins extensively for both propulsion and
maneuvering. Recent interest in using fishes as inspiration for the design of a new generation of autonomous underwater
vehicles has prompted both new experimental studies of fish locomotor function and efforts to use electroactive
polymers (EAP) as actuators in fish-inspired propulsive devices. The fins of fishes allow precise control over body
position and vectoring of thrust during propulsion and maneuvering. Recent experimental studies of fish locomotion
have revealed that fins exhibit much greater flexibility than previously suspected and that there is considerable
deformation of the fin surface during locomotion. The fins of the large group known as ray-finned fishes are supported
by fin rays, which have a bilaminar structure that allows active curvature control of the ray and fin surface by the fin
musculature. Fish have up to seven different fins, and these fins may interact with each other hydrodynamically during
locomotion. Fish fins provide an excellent test platform for the use of electroactive polymer actuators as the frequency
of movement is typically less than 5 Hz, and fin muscle strains typically range from 2 to 10%. Recent developments of
biorobotic fish pectoral fins actuated with EAP are reviewed.
Electroactive polymers (EAP) as an enabling tool in biomimetics
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Nature is filled with highly effective biological mechanisms that were refined thru evolution over millions of years offering an incredible model for inspiring human innovation. Humans have always made efforts to imitate nature's inventions. Advances in technology led to capabilities that allow adapting nature innovation beyond simply copying and the pool of possibilities in materials, structures, methods, processes and systems is enormous. Electroactive polymers (EAP) are increasingly being recognized as an important enabling technology for making biologically inspired capabilities. Using them as artificial muscles they are being considered for use a wide range of fields including medical, commercial, entertainment and many others. This paper reviews the up to date role that EAP is playing in advancing biomimetics and the field outlook.
A hands-on paradigm for EAP education: undergraduates, pre-college students, and beyond
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Electroactive polymers (EAPs) are receiving increasing interest from researchers due to their unique capabilities
and numerous potential applications in biomimetic robots, smart structures, biomedical devices, and micro/nanomanipulation. Since these materials are relatively new, it is imperative to educate students and the
general public to raise their awareness of EAP potentials and produce the talent pool needed for continuing, rapid
advances in the field of EAPs. In this paper we describe our concerted effort in teaching EAP to undergraduates,
grade school students, and the general public, through hands-on research and learning on EAP-based biomimetic
robots. Two integrated activities are highlighted: A senior Capstone design program on EAP robots, and the
subsequent programs that use these developed robots to reach out to pre-college students. A robotic fish and a
sociable robot enabled by ionic polymer-metal composite materials are used as examples throughout the paper.
Benefits and challenges of using ionic polymer metal composites in medical device applications
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Ionic Polymer Metal Composites (IPMCs) have several unique characteristics such as, low driving voltage, no
moving parts, etc., that allow the material to fulfill specific needs for medical device applications. However, there are
numerous challenges that must be addressed in order to utilize IPMC in medical devices. The research presented is a
culmination of efforts that address a number of these issues; such as electrolysis of water, safety concerns, material
characterization and in vitro testing. Work on IPMC development has raised the threshold of the electrolysis of water
during actuation from 2.35 V to 2.46 V in Tyrode's solution. The problem of back relaxation under DC excitation has
been reduced. To ensure accurate measurements of IPMC performance, for medical applications, it is imperative that the
appropriate in vitro testing conditions are chosen, such details are discussed. Material characterization techniques
developed and used by Pavad Medical, which are based on medical device needs, are also highlighted.
Electronic EAP
A road to practical dielectric elastomer actuators based robotics and mechatronics: discrete actuation
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Fundamental studies of Dielectric Elastomer Actuators (DEAs) using viscoelastic materials such as VHB 4905/4910
from 3M showed significant advantages at high stretch rates. The film's viscous forces increase actuator life and the
short power-on times minimize energy losses through current leakage. This paper presents a design paradigm that
exploits these fundamental properties of DEAs called discrete actuation. Discrete actuation uses DEAs at high stretch
rates to change the states of robotic or mechatronic systems in discrete steps. Each state of the system is stable and can
be maintained without actuator power. Discrete actuation can be used in robotic and mechatronic applications such as
manipulation and locomotion. The resolution of such systems increases with the number of discrete states, 10 to 100
being sufficient for many applications. An MRI-guided needle positioning device for cancer treatments and a space
exploration robot using hopping for locomotion are presented as examples of this concept.
Robust adaptive control of conjugated polymer actuators
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Conjugated polymers are promising actuation materials for bio and micromanipulation systems, biomimetic
robots, and biomedical devices. Sophisticated electrochemomechanical dynamics in these materials, however,
poses significant challenges in ensuring their consistent, robust performance in applications. In this paper an
effective adaptive control strategy is proposed for conjugated polymer actuators. A self-tuning regulator is
designed based on a simple actuator model, which is obtained through reduction of an infinite-dimensional
physical model and captures the essential actuation dynamics. The control scheme is made robust against
unmodeled dynamics and measurement noises with parameter projection, which forces the parameter estimates to
stay within physically-meaningful regions. The robust adaptive control method is applied to a trilayer polypyrrole
actuator that demonstrates significant time-varying actuation behavior in air due to the solvent evaporation.
Experimental results show that, during four-hour continuous operation, the proposed scheme delivers consistent
tracking performance with the normalized tracking error decreasing from 11% to 7%, while the error increases
from 7% to 28% and to 50% under a PID controller and a fixed model-following controller, respectively. In the
mean time the control effort under the robust adaptive control scheme is much less than that under PID, which
is important for prolonging the lifetime of the actuator.
Characterization of electroelastomers based on interpenetrating polymer networks
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Interpenetrating polymer networks (IPN) in which one elastomer network is under high tension balanced by
compression of the second network have been shown to exhibit electrically-induced strain up to 300% and promise a
number of polymer actuators with substantially enhanced performance and stability. This paper describes the
mechanical and thermal properties of the IPN electroelastomer films. The quasi-linear viscoelastic model and Yeoh
strain energy potential are used to characterize the viscoelastic response and stress-strain behavior of the IPN films in
comparison with 3M VHB films, primary component network in the IPN films. Material parameters were determined
from uniaxial stress relaxation experiments. An analysis of the results confirms that the IPN composites have reduced
viscoelasticity and fast stress-strain response due to preserved prestrain. Differential scanning calorimetry showed two
glass transition temperatures that are slightly shifted from the two component networks, respectively. The two networks
in the IPN are considered to be independent of each other. The thermal property is also studied with termogravimetric
analysis (TG).
Electromechanical coupling in cylindrical dielectric elastomer actuators
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Dielectric elastomer actuators in a cylindrical configuration, called "spring roll", have been used by the Empa team for
the first arm wrestling match between a human and a robotic arm driven by electroactive polymers (EAP) on the EAPAD
conference 2005 in San Diego. In this work, electromechanical coupling in EAP is investigated at the example of spring
rolls. The commonly used equation derived by Pelrine et al. (Sensors and Actuators A, 64, 1998) is analyzed and the
influence of the uncoated ("passive") parts is evaluated. Longer passive parts cause a force reduction in axial direction
which affects the performance of the actuator. Results have shown that (i) the equation of Pelrine represents a simplified
description of electromechanical coupling; (ii) the equation can be used for modeling electromechanical coupling in
spring rolls and (iii) the relative force reduction agrees to a great extent with the ratio between the uncoated area of a
spring roll and the total (coated and uncoated) area. These results are relevant for design and optimization of spring rolls.
Ionic EAP I
Can we overcome the relaxation of ionic polymer-metal composites?
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Currently, there is a major engineering challenge associated with Ionic Polymer-Metal Composites (IPMCs) that needs to be resolved before they can be widely adopted in future engineering markets--relaxation of the IPMC actuator under a DC voltage. In this paper, we rigorously discuss the origin of the relaxation phenomena of IPMCs. Our measured voltammograms and deflection data of IPMCs reveal that the relaxation phenomena of the IPMC actuators are primarily caused by the overpotential of surface electrodes. The overpotential values of ca. +1 V were clearly noted in many IPMC samples. We believe that the relaxation of IPMCs originate from the platinum oxide formation during actuation-a key surface reaction. The IPMC solvated with 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6]) showed a large bending, but there was no relaxation during actuation because there was no platinum oxide formation.
Finite element simulations of the bending of the IPMC sheet
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This paper presents a electro-mechanical model of an IPMC sheet. The model is developed using Finite Element method. The physical bending of an IPMC sheet due to the drift of counter-ions (e.g Na+) and water in applied electric field are simulated. Our model establishes a cause-effect relationship between the charge imbalance of the counter-ions and the mechanical bending of the IPMC sheet. The model takes into account the mechanical properties of the Nafion polymer as well as the platinum coating. As the simulations are time dependent, a transient model is used and some additional parameters, such as damping coefficients, are included. In addition to electro-mechanical model, electrochemical reactions are introduced. Equations describing periodic adsorption and desorption of CO and OH on a platinum electrode of an IPMC muscle immersed into formaldehyde solution are coupled to mechanical properties of the proposed model. This permits us to simulate self-oscillatory behavious of an IPMC sheet. The simulation results are compared to experimental data.
Charge redistribution under dynamic actuation of ionic polymer-metal composites
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In this paper, one-dimensional charge redistribution of IPMC material under dynamic electric potentials is studied. An
analytical solution of normalized charge density is obtained to account for the charge movement under applied electric
potentials. This solution is applicable for both static and dynamic electric potentials applied to IPMC material. Based on
this solution, the thicknesses of boundary layers under dynamic potentials can be calculated. The obtained solutions are
useful for further understanding and modeling of the mechanism of IPMC sensing and actuation.
Memorial Honoring of Alberto Mazzoldi
Contractile folded dielectric elastomer actuators
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New lightweight, compliant, reliable and cheap contractile linear actuators are demanded today for many fields of
application, such as robotics, automation and biomedical disciplines. Within the family of electroactive polymers,
dielectric elastomers are rapidly emerging as high-performance transduction materials, resulting particularly attractive in
order to accomplish different kinds of tasks. The design of efficient device architectures, capable of taking the most
from the material properties with practical solutions, is not trivial. In particular, the state of the art of contractile
dielectric elastomer actuators offers device configurations resulting not always of easy fabrication. To overcome this
drawback, a new actuating configuration, referred to as 'folded dielectric elastomer actuator', has been recently
described. This paper presents prototype samples of this new type of actuator, along with different examples of
applications currently being developed.
Integrated cell-based sensors and cell clinics utilizing conjugated polymer actuators
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Cell-based sensors are being developed to harness the specificity and sensitivity of biological systems for sensing
applications, from odor detection to pathogen classification. These integrated systems consist of CMOS chips
containing sensors and circuitry onto which microstructures have been fabricated to transport, contain, and nurture the
cells. The structures for confining the cells are micro-vials that can be opened and closed using polypyrrole bilayer
actuators. The system integration issues and advances involved in the fabrication and operation of the actuators are
described.
New and Other EAP I
Towards artificial molecular motor-based electroactive/photoactive biomimetic muscles
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Artificial molecular motors have recently attracted considerable interest from the nanoscience and nanoengineering
community. These molecular-scale systems utilize a 'bottom-up' technology centered around the design and
manipulation of molecular assemblies, and are potentially capable of delivering efficient actuations at dramatically
reduced length scales when compared to traditional microscale actuators. When stimulated by light, electricity, or
chemical reagents, a group of artificial molecular motors called bistable rotaxanes - which are composed of mutually recognizable
and intercommunicating ring and dumbbell-shaped components - experience relative internal motions of
their components just like the moving parts of macroscopic machines.
Bistable rotaxanes' ability to precisely and cooperatively control mechanical motions at the molecular level reveals the
potential of engineering systems that operate with the same elegance, efficiency, and complexity as biological motors
function within the human body. We are in a process of developing a new class of bistable rotaxane-based
electroactive/photoactive biomimetic muscles with unprecedented performance (strain: 40-60%, operating frequency: up
to 1 MHz, energy density: ~50 J/cm3, multi-stimuli: chemical, electricity, light). As a substantial step towards this longterm
objective, we have proven, for the first time, that rotaxanes are mechanically switchable in condensed phases on
solid substrates. We have further developed a rotaxane-powered microcantilever actuator utilizing an integrated
approach that combines "bottom-up" assembly of molecular functionality with "top-down" micro/nano fabrication. By
harnessing the nanoscale mechanical motion from artificial molecular machines and eliciting a nanomechanical response
in a microscale device, this system mimics natural skeletal muscle and provides a key component for the development of
nanoelectromechanical system (NEMS).
Description and characterization of an electroactive polymer synthetic jet actuator
Show abstract
The objective of this research was to describe and characterize the performance of an innovative new method of actuating a synthetic jet. This particular method utilizes a pre-strained dielectric elastomer membrane excited to operate at resonance. The paper describes the mechanism by which the actuator operates, the experimental techniques used to characterize it and discusses the results of the characterization. A series of experiments were devised to capture the influence of specific device parameters on the actuator system performance. The device parameters considered were: chamber volume, orifice diameter, orifice length, electrode area, excitation frequency, and excitation amplitude. Six metrics were collected for each of the tests: membrane displacement, chamber pressure, exit velocity, auditory signal, supply voltage, and supply current. Based on the cases tested, peak attainable orifice velocity was experimentally determined to be approximately 17 m/s, though the authors believe this can be significantly increased. Basic system design guidelines were also determined, and directions for future work have been identified.
Linear artificial muscle actuator based on synthetic elastomer
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In this paper we present a new artificial muscle actuator for rectilinear motion made of synthetic elastomer,
which is mainly focused on the robotic applications. Previously, we have developed a new material for actuating
means, named "synthetic elastomer". Synthetic elastomer allows their material properties such as mechanical as
well as electrical properties to be adjusted according to the requirements. Using the synthetic elastomers made
of the recipe adjusted for the robotic application, a new design of the artificial muscle actuator, called multi
stacked actuator is proposed. The actuator is comprised of multiple stacks of synthetic elastomer coated with
compliant electrodes and connecting disks. This unique design enables its linear actuation with the large strain
of active length as well as large force. Experimental works are conducted and the effectiveness of the actuator is
validated.
Investigation of electronechanical coupling and visco-elastic behavior of cellulose-based electro-active paper actuator
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Material properties of Electro-active paper (EAPap) actuator were investigated under different environmental conditions
such as humidity and temperature. Understanding of humidity and temperature effects on the material behavior of
EAPap during visco-elastic deformation regime provided useful information on structural changes of EAPap by
environmental factors. The pulling test results showed that the humidity and temperature heavily impact the mechanical
properties of EAPap. Electro-mechanical coupling effects were investigated by applying electric field during the pulling
test. Change of elastic modulus under different electric fields provides directional dependency of EAPap and strong
shear electro-mechanical coupling. Creep behavior of cellulose paper was studied to figure out mechanical strength of
EAPap under different ambient conditions. Tests under different humidity levels with fixed temperature and different
temperatures with fixed humidity provided the coupled hygrothermal effects on the performance of EAPap.
New and Other EAP II
Attempting a classification for electrical polymeric actuators
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Polymeric actuators, electroactive polymer actuators, electromechanical polymeric actuators, artificial muscles, and
other, are usual expressions to name actuators developed during the last 15-20 years based on interactions between the
electric energy and polymer films. The polymeric actuators can be divided into two main fields: electromechanical
actuators working by electrostatic interactions between the polymer and the applied electric fields, and
electrochemomechanical actuators, or reactive actuators, working by an electrochemical reaction driven by the flowing
electric current. The electromechanical actuators can be classified into electrostrictive, piezoelectric, ferroelectric,
electrostatic and electrokinetic. They can include a solvent (wet) or not (dry), or they can include a salt or not. Similitude
and differences related to the rate and position control or to the possibility or not to include sensing abilities are
discussed.
Epoxy hydrogels as sensors and actuators
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Most hydrogel actuators and sensors are made via acrylate polymerizations. Because these chain reactions are inhibited
by oxygen, it is difficult to prepare thin films or dots with good control. Epoxy curing chemistry is much less sensitive
to experimental conditions. We have previously shown that hydrogels formed from reaction between water-soluble
amines and epoxides can be readily printed. If the gel is filled with conducting carbon at a level close to the percolation
threshold, the resistance changes as water is taken up or removed from the gel. In particular, a pH decrease results in
ionization of amine groups and drives swelling of the gel. By incorporating an enzyme, such as glucose oxidase, that
releases hydrogen ions when its substrate is present, a resistance change can be used to measure substrate concentrations.
These gels also respond to stress with a change in resistance. By making the gel the anode or cathode of an electrolytic
cell, they can also be formed as actuators that expand or contract as the pH changes locally. Epoxy chemistry has been
little explored for gels. It is very versatile and could be used to make a wide range of gel composites with one or more
phases, varying water contents, varying functional groups and a range of electrical conductivity.
New electrode materials for dielectric elastomer actuators
Show abstract
Dielectric elastomer actuators exert strain due to an applied electric field. With advantageous properties such as high efficiency and their light weight, these actuators are attractive for a variety of applications ranging from biomimetic robots, medical prosthetics to conventional pumps and valves. The performance and reliability however, are limited by dielectric breakdown which occurs primarily from localized defects inherently present in the polymer film during actuation. These defects lead to electric arcing, causing a short circuit that shuts down the entire actuator and can lead to actuator failure at fields significantly lower than the intrinsic strength of the material. This limitation is particularly a problem in actuators using large-area films. Our recent studies have shown that the gap between the strength of the intrinsic material and the strength of large-area actuators can be reduced by electrically isolating defects in the dielectric film. As a result, the performance and reliability of dielectric elastomers actuators can be substantially improved.
Large response photo-activated polymer gel actuator
Show abstract
One drawback of Electro Active Polymer (EAP) materials for industrial actuation purposes is that the power needed to
scale up the technology is prohibitive both in the sheer magnitude and cost. The development of a reversible ionic
photo-activated polymer (IPAP) actuator material is a way to circumvent the prohibitive power needs and gain
industrial acceptance of polymer actuator materials. By doping electro active or ionic polymers with photo reversible
ionic sources it is possible to create similar response characteristics to that of ionic EAP actuators. The power needed
to drive a single light source would inherently be much less that needed to drive individual EAP actuators as size of
application increased, this reduction in power would also be multiplied by the number of actuators in a given system. It
is also theorized that the speed of actuation cycles would be increased by diffuse irradiation throughout the material.
Even more attractive is the possibility of the material being activated from natural daylight irradiation and the need for
electrical power eliminated.
EAP Characteristics and Database
Electroactive polymer actuator online database
Show abstract
As polymer actuator performance improves there is an increasing demand to understand and compare properties. Past comparisons have relied on general statements of properties but do not capture the interdependence of these properties or keep up with the rapid pace of change. Modeling such interdependencies is complex. An alternative is to compile many measurements. A new actuator database has been created that is a compilation of experimental methods and results (mechanical, electrical, chemical and other properties) combined with a web interface. The objective is to capture actuator performance under a wide variety of conditions. The current content of the page is presented and justified. Researchers may submit data to the web page via an online form.
Ionic EAP II
Chemo-electric characterization and modeling of the high surface area electrodes in ionic polymer transducers
Show abstract
Ionomeric polymer transducers have received considerable attention in the past ten years due to their ability to generate large bending strain and moderate stress at low applied voltages. Ionic polymer transducers consist of an ionomer, usually Nafion, sandwiched between two electrically conductive electrodes. Recently, a novel fabrication technique denoted as the direct assembly process (DAP) enabled controlled electrode architecture in ionic polymer transducers. A DAP transducer consists of two high surface area electrodes made of uniform distributed particles sandwiching an ionomer membrane.
In this paper theoretical investigations as well as experimental verifications are performed. The model consists of a convection-diffusion equation describing the chemical field as well as a Poisson equation describing the electrical field. This modeling technique is modified to capture the chemo-electric behavior in the high surface area electrodes of a DAP fabricated transducer. The model assumes highly conductive particles randomly distributed in the electrode area. This is the first electro-chemical modeling account of high surface area electrodes in ionic polymer transducers. Traditionally, these kinds of electrodes were simulated with boundary conditions representing flat electrodes with a large dielectric permittivity at the polymer boundary. In the experimental section, several transducers are fabricated using the DAP process on Nafion 117 membranes. The architecture of the high surface area electrodes in these samples is varied. The concentration of the spherical gold particles is varied from 30 vol% up to 60 vol%, while the overall thickness of the electrode is varied from 10 &mgr;m up to 40 &mgr;m micrometer at a fixed concentration. The flux and charge accumulation in the materials are measured experimentally and compared to the results of the numerical simulations. Finally, the high surface area electrodes are compared to flat gold electrodes.
Manufacturing of ionic polymer-metal composites (IPMCs) that can actuate into complex curves
Show abstract
Ionic polymer-metal composites (IPMC) are soft actuators with potential applications in the fields of medicine and
biologically inspired robotics. Typically, an IPMC bends with approximately constant curvature when voltage is applied
to it. More complex shapes were achieved in the past by pre-shaping the actuator or by segmentation and separate
actuation of each segment. There are many applications for which fully independent control of each segment of the
IPMC is not required and the use of external wiring is objectionable. In this paper we propose two key elements needed
to create an IPMC, which can actuate into a complex curve. The first is a connection between adjacent segments, which
enables opposite curvature. This can be achieved by reversing the polarity applied on each side of the IPMC, for
example by a through-hole connection. The second key element is a variable curvature segment. The segment is
designed to bend with any fraction of its full bending ability under given electrical input by changing the overlap of
opposite charge electrodes. We demonstrated the usefulness of these key elements in two devices. One is a bi-stable
buckled IPMC beam, also used as a building block in a linear actuator device. The other one is an IPMC, actuating into
an S-shaped curve with gradually increasing curvature near the ends. The proposed method of manufacturing holds
promise for a wide range of new applications of IPMCs, including applications in which IPMCs are used for sensing.
Mixed-ion linear actuation of PPy and PEDOT in propylene carbonate-triflate electrolytes
Show abstract
Investigations of the actuation properties of free standing PPy and PEDOT films in a propylene carbonate-triflate electrolyte (PC/TBACF3SO3) under isotonic (constant load)
conditions are presented in this work. The PPy film showed mixed ion movement during charging and discharging in cyclic voltammetric and chronoamperometric experiments. At a potential of -1.0 V the maximum strain was in the range of 1-2 % whereas at the anodic potential of +1.0 V strains in the range of 3-4 % were observed. Cyclic voltammetry experiments at higher scan rates to 10 mV/s led to a decrease in the anodic strain and an increase in the cathodic strain before it declined at higher scan rates. The free-standing PEDOT films showed mainly cathodic actuation at the potential -1.0 V and the size of actuation was again dependent upon the scan rate. Cation movement is discussed in terms of
the immobilisation of CF3SO3- anions during polymerisation. Extended potential step experiments showed good actuation and low creep in the potential range between 0.0 and
+1.0 V. The surface morphology (SEM) showed an open porous structure for PEDOT in contrast to the smooth morphology of PPy.
Synthesis and characterization of porous polyaniline conductive polymers
Show abstract
Polyaniline conductive polymers exhibit great potential for linear actuator applications. Many recent studies
report methods to develop polyaniline-based materials with increased mechanical properties, electrical conductivity,
and faster response time during actuation. In this study, porous blends of poly(methylmethacrylate) and
polyaniline are processed using a two phase batch foaming setup. The effect of materials, processing, and system
parameters on the physical properties of the resulting cellular structure are investigated. Hence, the effect of
density and cell morphology on the electrical conductivity is elucidated.
Nano and Micro EAP
Mechanical properties of electroactive polymer microactuators with ion-implanted electrodes
Show abstract
We report on the use of the bulge test method to characterize the mechanical properties of miniaturized buckling-mode dielectric elastomer actuators (DEA). Our actuator consists of a Polydimethylsiloxane (PDMS) membrane bonded to a silicon chip with through holes. Compliant electrodes are fabricated on both sides of the membrane by metal ion implantation. The membrane buckles when a critical voltage is applied to the electrodes. The maximum displacements as well as the efficiency of such actuators strongly depend on the mechanical parameters of the combined electrode-elastomer-electrode layer, mainly effective Young's modulus E and residual stress &sgr;. We report measured E and &sgr; obtained from bulge tests on PDMS membranes for two PDMS brands and for several different curing methods, which allows tuning the residual stress by controlling the rate of solvent evaporation. Bulge test measurements were then used to study the change in membranes' mechanical properties due to titanium ion implantation, compared to the properties obtained from depositing an 8 nm thick gold electrode. At the doses required to create a conductive layer, we find that the Ti ion implantation has a low impact on the membrane's overall rigidity (doubling of the Young's modulus and reducing the tensile stress) compared to the Au film (400% increase in E). The ion implantation method is an excellent candidate for DEAs' electrodes, which need to be compliant in order to achieve large displacements.
Modeling
Development and modeling of novel extensional ionic polymer transducers
Show abstract
Ionic polymer transducers (IPT), sometimes referred to as artificial muscles, are known to generate a large bending strain
and a moderate stress at low applied voltages. Bending actuators have limited engineering applications due to the low
forcing capabilities and the need for complicated external devices to convert the bending action into rotating or linear
motion desired in most devices. Recently Akle and Leo (2006) reported extensional actuation in ionic polymer
transducers. Model prediction indicates that such actuators can produce strain up to 10% and a blocked stress up to
20MPa under a +/- 2V applied electric potential. Compared to other smart materials, IPT is a flexible membrane and it
has a reliability of over one million cycles. In this work novel extensional IPT actuators are developed for the purpose of
increasing the overall displacement of the actuator. The electromechanical coupling is measured and a correlation of the
experimental data with the active areas model by Akle and Leo (2006) and the numerical electromechanical model by
Wallmersperger and Leo (2004) are presented. The coupling between each test case with the model parameters enables
further understanding of the physical actuation phenomena as the role of diffusion of ions and diluents and the
electrostatic forces between the charged species. In this study the displacement of an extensional ionic polymer
transducer is measured and compared to the bending of the same IPT actuator. The bending strain is measured to be
approximately 2.5%, while the extensional strain for the same ionomer is in the order of 17.5%. Finally an interesting
behavior, reported for the first time is the steady expansion of the IPT sample due to the application of a symmetrical
sine wave. This indicates that charge accumulation is occurring at the electrode.
A scalable model for trilayer conjugated polymer actuators and its experimental validation
Show abstract
Conjugated polymers have promising applications as actuators in biomimetic robotics and bio/micromanipulation.
For these applications, it is highly desirable to have predictive models available for feasibility study and design
optimization. In this paper a geometrically-scalable model is presented for trilayer conjugated polymer actuators
based on the diffusive-elastic-metal model. The proposed model characterizes actuation behaviors in terms of
intrinsic material parameters and actuator dimensions. Experiments are conducted on polypyrrole actuators of
different dimensions to validate the developed scaling laws for the quasi-static force and displacement output,
the electrical admittance, and the dynamic displacement response.
Self-sensing McKibben actuators using dielectric elastomer sensors
Show abstract
In this paper, a self-sensing McKibben actuator using dielectric elastomer sensors is presented. Fiber-reinforced
cylindrical actuators offer one potential solution to the low-force output problem that plagues many artificial muscle
actuators. Placing a cylindrical dielectric elastomer sensor in direct contact with the inner surface of the McKibben
actuator facilitates in situ monitoring of actuator strains and loads. The deformation of the McKibben actuator and hence
the cylindrical dielectric elastomer sensor results in a change in the electrical signal read from the electroded surfaces of
the dielectric elastomer. In this paper, we present a model for predicting the response of fiber reinforced cylindrical
constructs (McKibben actuators) that are actuated by an inflation pressure, which is used to support an axial load. The
model is based on Adkins and Rivlin's large deformation model for the inflation and contraction of tubes reinforced with
inextensible fibers. In this model, the McKibben actuator is considered as a surface of revolution since the initially near
cylindrical shape is nearly always compromised during mechanical loading. A series of experiments measuring the force
versus contraction behavior of the actuators are used to validate the numerical model. The material constants for an
Ogden model were determined by uni-axial extension of cylindrical samples. A comparison of the numerical and
experimental results shows that the correlation is good. The model enables a number of key analyses such as the effect
of the braid angle and the tension generated in the fibers.
Integrated extension sensor based on resistance and voltage measurement for a dielectric elastomer
Show abstract
This paper presents a method for creating a smart Dielectric Elastomer Actuator (DEA) with an integrated extension
sensor based on resistance and voltage measurement. Such a sensor can reduce cost, complexity, and weight compared to
external sensor solutions when used in applications where external sensing is difficult or costly, such as Micro-Electro-
Mechanical Systems (MEMS). The DEAs developed for integrated feedback are 20mm by 70mm and 30 &mgr;m thick
double layer silicone-dielectric actuators with reinforcing silicone ribs. Loose-carbon-powder electrodes produced the
best electrical and mechanical characteristics out of several possibilities tried.
Electrically isolated circuits were used to measure electrode resistance and driving voltage. These parameters were then
related to experiment using a model to predict DEA length. An offline regression method was used to fit the model to
within 2% of the full sensor range and the results were verified experimentally. The sensor feedback inaccuracy
immediately after a position step disturbance was shown to be around 20% of the full sensor range. This improved over 5
seconds to less than 5% as the transient creep effects in the silicone membrane that introduced the initial inaccuracy
decayed. Long term creep reduced the accuracy of the model, necessitating periodic retraining of the sensor. Overall the
sensor-estimated extension shows a very good qualitative or 'shape' match with the actual extension in the system.
On a distributed parameter model for electrical impedance of ionic polymer
Show abstract
From the observation of the measured frequency response, the electrical impedance of IPMC has the characteristics
of a distributed parameter system. Especially in the case of TEA ion, we found that the frequency response
cannot be approximated by a simple ideal capacitor or even by low-order transfer functions. In this study, we
discuss a black-box circuit modeling of the electrical system of IPMC from the point of view of the frequency
response. We employ some models whose transfer functions are not rational. One of such models is a distributed
circuit (transmission line). Another is a black-box circuit model with a distributed parameter element (constant
phase element). Both transfer functions consist of square root of 's'. In the experiment, the electrical impedance
of an IPMC (gold plated Nafion) is measured under some conditions such as electrode clamp sizes and two
cation species, Na ion and TEA ion. From the result, we found that the electrode clamp condition less affects
the measured impedance. However, we observed that the impedance highly depends on the cation species. From
the experimental frequency response, the parameters of the model are identified. Larger resistance and smaller
capacitive element are identified in TEA case than those in Na case. The identified parameters are consistent
with the physical intuition that TEA ion movement is slower than Na ion.
Modeling of the nonlinear effects in pH sensors based on polyelectrolytic hydrogels
Show abstract
pH-sensitive hydrogels are capable of reversibly converting chemical energy into mechanical energy and therefore they
are widely used as sensitive materials for pH sensors. However nonlinear effects such as hysteresis and drift are observed
in the swelling behaviour of the polyelectrolytic hydrogels complicating the calibration procedure for the pH sensor and
affecting the signal reproducibility.
In the present work, in order to realize a pH sensor with a high signal reproducibility and high long-term stable sensor
sensitivity, the complicated kinetics of gel swelling/deswelling processes is analysed and the origin of the hysteresis
nonlinearities is elucidated. It is found that the long-time drift in the sensor characteristic is caused by the drift of
hydrated ions and water into the gel or out of the gel in dependence on the pH range of the solution and on the chemical
reactions which occur in the gel during the swelling or shrinking processes. The rate of the water drift is determined by
the change rate of the concentration of ionized groups which increase the gel hydrophilicity and consequently the gel
swelling.
Applications of EAP I
Development of soft actuator: mechanism with vibration element using dielectric elastomer to generate large displacement
Show abstract
An electric active polymer (EAP) using a dielectric elastomer is superior in the points of view of generated stress and
strain, response velocity, and energy efficiency. On the other hand, it is well known that a high polymer material has
creep properties. There is no research about creep of a dielectric elastomer actuator (DEA) as far as we know. It is
necessary to get a clear grasp of the creep properties of a DEA in order to design a DEA. The purpose of our research
was to investigate the creep characteristics and propose a mechanism of a DEA that can generate a large displacement
without creep deformation. At first, a sample element of a DEA was made and tested. As a result, it was found that creep
deformation was generated and accumulated by the repeated actions. Secondly, an element structure of a DEA was
proposed. The element had two driven areas on opposite sides and these two areas are actuated alternately. Therefore, the
proposed element worked as a vibration element. The repeated fatigue tests of the proposed vibration element gave proof
of the effectiveness against creep deformation. At last, a unit mechanism of a DEA was proposed. The proposed unit
mechanism was a combination of the vibration element and a ratchet mechanism. Through a performance test of the
proposed experimental unit mechanism, it was confirmed that the mechanism was able to be driven and the transport
velocity was changed by changing the drive frequency of the vibration element.
EAP as actuator for a gripper with variable curvature
Show abstract
Nowadays, the bottleneck of the fabrication of hybrid microsystems is the assembling phase of microscopic components.
Indeed, at microlevel, as a result of the high surface to volume ratio, superficial forces become dominant with respect to
other ones and the development of new handling techniques is strongly required. In this context, innovative handling
systems have been studied at ITIA. The possibilitiy of controlling and exploiting the capillary force has been investigated
and an original handling system, based on capillary force, has been conceived. The theoretical studies led to the
development of a first prototype of a gripper with variable curvature and the results obtained from this prototype
encouraged the development of a smaller prototype, able to manipulate objects with weight of the order of milligrams.
Regarding the actuation system of such a gripper, smart materials seemed to be required. Specifically, a novel
configuration based on electroactive polymers (EAP) has been conceived. A feasibility study to evaluate their
functionality and performances, as actuation system, has been carried out and the results are presented in this paper.
Study of flapping actuator modules using IPMC
Show abstract
The Ionic Polymer Metal Composite (IPMC), an electro-active polymer, has many advantages including bending
actuation, low weight, low power consumption, and flexibility. These advantages coincide with the requirements of
flapping-wing motion. Thus, IPMC can be an adequate smart material for the generation of the flapping-wing motions.
In this research, a flapping actuator module operated at the resonant frequency is developed using an IPMC actuator.
First, IPMC actuators are fabricated to investigate the mechanical characteristics of IPMC as an actuator. The
performances of the IPMC actuators, including the deformation, blocking force and natural frequency, are then obtained
according to the input voltage and IPMC dimensions. Second, the empirical performance model and the equivalent
stiffness model of the IPMC actuator are established. Third, flapping actuator modules using the first resonance
frequency are developed, and their flapping frequency and stroke characteristics are investigated. Fourth, adequate
flapping models for a flapping actuator module are selected, and dimensional data such as wing area and wing mass are
obtained. Finally, the flapping actuator module is designed and manufactured to adjust the flapping models and its
performance is tested. Experimental results demonstrate the potential IPMC has for use as a flapping actuator.
A linear actuator from a single ionic polymer-metal composite (IPMC) strip
Show abstract
We present a novel linear actuator made from a single Ionic Polymer-Metal Composite (IPMC) strip. In its simplest
form the device activates into the shape of a double-clamped buckled beam. This structure was chosen following
observation of the buckle failure modes of axially compressed beams. The practical realization of this device is made
possible by the development of new manufacturing techniques also described. The benefit of this buckled beam
structure is that bending moments in the two halves of the beam cancel each other out. As a result, only one bending
actuator is needed to form a single linear actuator and there is no need for mechanical joining of separate actuators - a
disadvantage of previous linear actuator designs. The non-rotating nature of the end fixing in the double-clamped
buckled beam also means that joining multiple elements to increase displacement or force is trivial. We present initial
experimental results of a single linear actuator and a balanced, pair-connected linear actuator.
Ionic polymer-metal composite as energy harvesters
Show abstract
The Ionic Polymer Metal Composite (IPMC) is an Electroactive Polymer (EAP) capable of soft sensing as well as soft
actuation under low driving voltage. Typically, the transduction model includes two resistors and two capacitors, which
primarily accounts for the effective electrodes on the surface of the IPMC (top and bottom). There is a resistor placed
between the two RC circuits to account for material between the electrodes and the resistance due to ion migration
through the polymer matrix. In this paper we report our recent effort on IPMCs in connection with the application in
energy harvesters. The experiments conducted use IPMC samples with various lengths, various widths and various
thicknesses, and compare the charging rates of the different transducer sizes. The experimental results clearly indicate
that IPMCs are attractive applicants for energy harvesting.
Sensor-actuator coupled device for active tracheal tube using solid polymer electrolyte membrane
Show abstract
A sensor-actuator coupled device was developed using solid polymer electrolyte membrane (SPM) as an active tracheal
tube for ventilator. Active tracheal tube is a novel type of tube for ventilator that removes patient's phlegm
automatically upon sensing the narrowing of trachea by phlegm. This type of active tube is extremely useful in clinical
settings as currently the sole measure to remove phlegm from patient's tube is to do it manually by a nurse every few
hours.
As SPM works both as a sensor and an actuator, an effective compact device was developed. SPM based
sensor-actuator coupled device was fabricated with modified gold plating method. Prepared SPM was fixed as an array
on a plastic pipe of diameter 22 mm and was connected to a ventilator circuit and driven by a ventilator with a volume
control ventilation (VCV) mode. SPM was connected both to a sensing unit and an actuation unit.
Generated voltage developed by the membrane with the setting of the maximum pressure from 5 cmH2O to 20 cmH2O
was in order of several hundred &mgr;V. SPM sensor demonstrated a biphasic response to the ventilator flow. The sensor
data showed nearly linearly proportional voltage development to the intra-tracheal pressure.
The sensed signal was filtered and digitized with an A/D converting unit on a PC board. A real time operating program
was used to detect the sensed signal that indicates the narrowing of trachea. The program then activated a driving
signal to control the actuation of the membrane. The signal was sent to a D/A converting unit. The output of the D/A
unit was sent to an amplifier and the galvanostat unit which drives the membrane with constant current regardless of the
change in the load.
It was demonstrated that the sensor-actuator unit detects the narrowing of trachea within several hundreds milli-seconds
and responds by actuating the same membrane with the driving voltage of 3-4 V and driving current of several hundred
milli-ampere for each membrane. SPM array actuated the obstructing material of 2 g to expel from the trachea tube.
Also, a theoretical model of the propagating wave generated by SPM was examined.
Applications of EAP II
Applications of conducting polymers: robotic fins and other devices
Show abstract
Conducting polymers are becoming viable engineering materials and are gradually being integrated into a wide range of
devices. Parallel efforts conducted to characterize their electromechanical behavior, understand the factors that affect
actuation performance, mechanically process films, and address the engineering obstacles that must be overcome to
generate the forces and displacements required in real-world applications have made it possible to begin using
conducting polymers in devices that cannot be made optimal using traditional actuators and materials. The use of
conducting polymers has allowed us to take better advantage of biological architectures for robotic applications and has
enabled us to pursue the development of novel sensors, motors, and medical diagnostic technologies. This paper uses the
application of conducting polymer actuators to a biorobotic fin for unmanned undersea vehicles (UUVs) as a vehicle for
discussing the efforts in our laboratory to develop conducting polymers into a suite of useful actuators and engineering
components.
Applications of dielectric elastomer EPAM sensors
Show abstract
While Electroactive Polymer Artificial Muscle (EPAM) has been presented extensively as a solution for actuation and generation technology, EPAM technology can also be used in multiple novel applications as a discrete or integrated sensor. When an EPAM device, an elastic polymer with compliant electrodes, is mechanically deformed, both the capacitance of the EPAM device, as well as the electrode and dielectric resistance, is changed. The capacitance and resistance of the sensor can be measured using various types of circuitry, some of which are presented in this paper. EPAM sensors offer several potential advantages over traditional sensors including operation over large strain ranges, ease of patterning for distinctive sensing capabilities, flexibility to allow unique integration into components, stable performance over a wide temperature range and low power consumption. Some existing challenges facing the commercialization of EPAM sensors are presented, along with solutions describing how those challenges are likely to be overcome. The paper describes several applications for EPAM sensors, such as an integrated diagnostic tool for industrial equipment and sensors for process and systems monitoring.
A compact electroactive polymer actuator suitable for refreshable braille display
Show abstract
The large strain, high elastic modulus, and easy processing of P(VDF-TrFE-CFE) electrostrictive terpolymer make it
very attractive to replace low strain piezoceramics and piezopolymers in many applications with much improved
performance. In this paper, a compact polymer actuator is developed utilizing the electrostrictive terpolymer, which
is suitable for full page Braille Display and graphic display. Key issues related to the reliability of electroactive
polymers used in the compact actuators and for the mass fabrication of these polymer actuators are investigated.
Making use of a recently developed conductive polymer, a screen printing deposition method was developed which
enables direct deposition very thin conductive polymer electrode layer (< 0.1 &mgr;m) with strongly bonding to the
terpolymer surface and short fabrication time. It was observed that the thin conductive polymer electrodes lead to the
self-healing of the polymer after electric breakdown. An EAP compact Braille actuator was designed and fabricated
with these terpolymer films wound on a spring core. The test results demonstrate that the EAP Braille actuator meets
all the functional requirements of actuators for refreshable full Braille display, which offers compact size, reduced
cost and weight.
Capacitive charging and background processes in carbon nanotube yarn actuators
Show abstract
Twist-spun carbon nanotube yarns actuate when extra charge is added to the yarn. This charge can be stored in a doublelayer
capacitor formed when the yarn is submersed in an electrolyte. The dependence of the actuation stress and strain on
the stored charge must be studied if double layer charging models are to be fully verified over large potential ranges.
However, background currents are generated in the system when an electrical potential is applied, making it hard to
discern the charge stored in the actuator and the charge that passes through the cell due to faradaic processes. A model is
developed to separate the capacitive and faradaic portions of the actuator current. The model is then applied to the
analysis of the actuation data. The consistency of the results paves the way to understanding the real strain-charge
behavior of the actuator.
Piezoresistive sensors for smart textiles
Show abstract
We have used inkjet printing to deposit silver conducting lines and small PEDOT (conducting polymer) sensors onto fabrics. The printed conductors penetrate into the fabric and can be shown to coat the individual fibers within the yarn, through the full thickness of the cloth. The PEDOT sensor has a resistance in the region of a few kilo-ohms and is connected to measuring equipment by printed silver lines with a resistance of a few ohms. In this way, local strains can be measured at different sites on a fabric. The PEDOT responds to a tensile strain by a reduction in resistance with a gauge factor (change in resistance/strain) from -5 to -20. This compares with conventional strain gauges where the gauge factor is normally +2. These sensors cycle to strains of over 10%. We have measured gauge factors as a function of the orientation of the sensing line to the fabric axes, to the strain axes for different fabric structures. We can correlate the gauge factor with the extent to which the twisted multifilament yarns are expected to become laterally compressed. In preliminary tests we have shown that these printed sensors can be used to monitor knee and wrist motions and so could be used to provide information in applications such as rehabilitation from joint damage.
Applications of EAP III
Tri-layer conducting polymer actuators with variable dimensions
Show abstract
The ability of conducting polymer actuators to convert electrical energy into mechanical energy is influenced by many
factors ranging from the actuators physical dimensions to the chemical structure of the conducting polymer. In order to
utilise these actuators to their full potential, it is necessary to explore and quantify the effect of such factors on the
overall actuator performance. The aim of this study is to investigate the effect of various geometrical characteristics such
as the actuator width and thickness on the performance of tri-layer polypyrrole (PPy) actuators operating in air, as
opposed to their predecessors operating in an appropriate electrolyte. For a constant actuator length, the influence of the
actuator width is examined for a uniform thickness geometry. Following this study, the influence of a varied thickness
geometry is examined for the optimised actuator width. The performance of the actuators is quantified by examination of
the force output, tip displacement, efficiency as a function of electrical power and mechanical power, and time constant
for each actuator geometry. It was found that a width of 4mm gave the greatest overall performance without curling
along the actuator length (which occurred with widths above 4mm). This curling phenomenon increased the rigidity of
the actuator, significantly lowering the displacement for low loads. Furthermore, it was discovered that by focussing a
higher thickness of PPy material in certain regions of the actuators length, greater performances in various domains
could be achieved. The experimental results obtained set the foundation for us to synthesize PPy actuators with an
optimised geometry, allowing their performance to reach full potential for many cutting applications.
Design and fabrication of tactile sensors based on electroactive polymer composites
Show abstract
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.
Low voltage, highly tunable diffraction grating based on dielectric elastomer actuators
Show abstract
We present an electrically tunable diffraction grating, driven by thin-film dielectric elastomer actuators. The device
combines the advantages of dielectric elastomer actuators, capable of generating very large strains, with the desirable
properties of Micro-Opto-Electro-Mechanical Systems (MOEMS). The soft materials based tunable diffraction grating
achieves a continuous grating period change of 19.2%, when a voltage of 500 V is applied. This is an improvement by a
factor of 90 compared to conventional analog tunable diffraction gratings based on hard materials. Further device
characterization yielded a tunable angular range of more than 100 mrad. Additionally, we show that in combination with
a collimated white light source (e.g. white light emitting diode), the discussed tunable diffraction grating can be used for
wavelength-adjustable luminous sources. Integrated into displays, these light sources could facilitate the first technology
able to reproduce all perceivable colors.
Concept study on active shells driven by soft dielectric EAP
Show abstract
Adaptive structures are capable to change their shape in a smart way in order to "adapt" to variable external conditions.
Active shell structures with large out-of-plane deformation potential may be used to generate an interaction between the
structural shape and the environment. Exemplarily, such shell-like actuators may be utilized for the propulsion of
vehicles through air or water. Among the electroactive polymers (EAPs) especially soft dielectric EAP are promising for
driving shell-like actuators due to their huge active strain potential and intrinsic compliancy.
The challenging task of this study was to explore the potential of the DE actuator technology for the design of shell-like
actuators with the ability to perform complex out-of-plane deflections. We present and evaluate concepts for the design
of active shell structures driven by soft dielectric EAP. Preliminary experiments were conducted for selected approaches
in order to basically verify their principle of operation and to quantify their active out-of-plane deformation potential.
These experiments showed that the so-called agonist-antagonist configuration, where pre-strained DE films are attached
on both sides of a hinged backbone structure, holds good performance in terms of active out-of-plane deflections and
forces.
Piezoelectric polymers actuators for precise shape control of large scale space antennas
Show abstract
Extremely large, lightweight, in-space deployable active and passive microwave antennas are demanded by future
space missions. This paper investigates the development of PVDF based piezopolymer actuators for controlling the
surface accuracy of a membrane reflector. Uniaxially stretched PVDF films were poled using an electrodeless
method which yielded high quality poled piezofilms required for this applications. To further improve the
piezoperformance of piezopolymers, several PVDF based copolymers were examined. It was found that one of
them exhibits nearly three times improvement in the in-plane piezoresponse compared with PVDF and P(VDF-TrFE)
piezopolymers. Preliminary experimental results indicate that these flexible actuators are very promising in
controlling precisely the shape of the space reflectors. To evaluate quantitatively the effectiveness of these PVDF
based piezopolymer actuators for space reflector applications, an analytical approach has been established to study
the performance of the coupled actuator-reflector-control system. This approach includes the integration of a
membrane reflector model, PVDF piezopolymer actuator model, solution method, and shape control law. The reflective Newton method was employed to determine the optimal electric field for a given actuator configuration and loading/shape error.
Electro-active polymers as a novel actuator technology for lighter-than-air vehicles
Show abstract
In this paper the worldwide first EAP actuated blimp will be presented. It consists of a slightly pressurized Helium filled
body of a biologically inspired form with Dielectric Elastomer (DE) actuators driving a classical cross tail with two
vertical and horizontal rudders for flight control. Two versions of actuators will be discussed: The first version consisted
of "spring-roll" type of cylindrical actuators placed together with the electrical supply and control unit in the pay load
gondola. The second version consisted of a configuration, where the actuators are placed between the control surfaces
and the rudders. This novel type of EAP actuator named "active hinge" was developed and characterized first in the
laboratory and afterwards optimized for minimum weight and finally integrated in the blimp structure. In the design
phase a numerical simulation tool for the prediction of the DE actuators was developed based on a material model
calibrated with the test results from cylindrical actuators. The electrical supply and control system was developed and
optimized for minimum of weight. Special attention was paid to the electromagnetic systems compatibility of the high
voltage electrical supply system of the DE actuators and the radio flight control system. The design and production of
this 3.5 meter long Lighter-than-Air vehicle was collaboration between Empa Duebendorf Switzerland and the Technical
University of Berlin. The first version of this EAP blimp first flew at an RC airship regatta hold on 24th of June 2006 in
Dresden Germany, while the second version had his maiden flight on 8th of January 2007 in Duebendorf Switzerland. In
both cases satisfactory flight control performances were demonstrated.
Poster Session
The mechanical properties of ionic polymer-metal composites
Show abstract
In this study, we investigated the mechanical properties of various type ionic polymer-metal composites (IPMCs) and Pt,
Au, Pd, and Pt electroded ionic liquid (IL-Pt) IPMCs, by testing tensile modulus and dynamic mechanical behavior. The
SEM was utilized to investigate the characteristics of the doped electroding layer, and the DSC was probed in order to
look into the thermal behavior of various types of IPMCs. Au IPMCs, having a 5~7 &mgr;m doped layer and nano-sized Au
particles (ca. 10 nm), showed the highest tensile strength (56 MPa) and modulus (602 MPa) in a dried condition. In a
thermal behavior, Au IPMC has the highest Tg (153°C) and Tm (263°C) in both the DMA and DSC results. The fracture
behavior of various types IPMCs followed base material's behavior, NafionTM, which is represented as the
semicrystalline polymer characteristic.
Thermomechanical characterization of shape memory polymers
Show abstract
Data from comprehensive thermomechanical tests of shape memory polymers are reported, with specimens tested up to
75% strain and between 30-120°C temperatures. The data is analyzed and key observations are drawn. The stress/strain
behavior during loading at temperatures above glass transition for the Veriflex shape memory polymer tested was
linear and did not show much variation with the actual temperature. When the polymer is cooled with end constraints,
thermally induced tensile stresses developed, but only after the temperature reduced below glass transition and the
material stiffened. When the constraints were then released, 97-98% of the original strain was locked in. Reheating the
shape memory polymer beyond the glass transition temperature resulted in shape recovery (shape memory effect). When
the polymer was reheated while constraining the strain, the full recovery stress developed was about the stress the
polymer was initially loaded to during deformation at high temperature. Examining the Young's modulus at elevated
temperature and low temperature showed that Veriflex softened by around 40-60 times when heated through glass
transition.
EAP hydrogels for pulse-actuated cell system (PACS) architectures
Show abstract
Electroactuated polymer (EAP) hydrogels based on JEFFAMINE® T-403 and ethylene glycol glycidyl ether (EGDGE)
are used in an infusion pump based on the proprietary Pulse Actuated Cell System (PACS) architecture in development
at Medipacs LLC. We report here significant progress in optimizing the formulation of the EAP hydrogels to
dramatically increase hydrolytic stability and reproducibility of actuation response. By adjusting the mole fraction of
reactive components of the formulation and substituting higher molecular weight monomers, we eliminated a large
degree of the hydrolytic instability of the hydrogels, decreased the brittleness of the gel, and increased the equilibrium
swelling ratio. The combination of these two modifications to the formulation resulted in hydrogels that exhibited
reproducible swelling and deswelling in response to pH for a total period of 10-15 hours.
IPMC-assisted miniature disposable infusion pumps with embedded computer control
Show abstract
For military applications, the availability of safe, disposable, and robust infusion pumps for intravenous fluid and drug
delivery would provide a significant improvement in combat healthcare. To meet these needs, we have developed a
miniature infusion prototype pump for safe and accurate fluid and drug delivery that is programmable, lightweight, and
disposable. In this paper we present techniques regarding inter-digitated IPMCs and a scaleable IPMC that exhibits
significantly improved force performance over the conventional IPMCs. The results of this project will be a low cost
accurate infusion device that can be scaled from a disposable small volume liquid drug delivery patch to disposable large
volume fluid resuscitation infusion pumps for trauma victims in both the government and private sectors of the health
industry.
Development of dielectric elastomer driven micro-optical zoom lens system
Show abstract
Normally, various micro-scale devices adopt electromechanical actuators for their basic mechanical functions.
Those types of actuators require a complicated power transfer system even for generating a tiny scale motion.
Since the mechanical power transfer system for the micro-scale motion may require many components, the
system design to fit those components into a small space is always challenging. Micro-optical zoom lens systems
are recently popularly used for many portable IT devices such as digital cameras, camcorder, and cell phones,
Noting the advantages of EAP actuators over the conventional electromechanical counterparts in terms of simple
actuator mechanisms, a micro-optic device that is driven with the EAP actuator is introduced in the present
work. EAP material selection, device design and fabrication will be also delineated.
Modeling a dielectric elastomer actuator based on the McKibben muscle
Show abstract
Our work focuses on a contractile dielectric elastomer actuator (DEA) based on the McKibben pneumatic muscle
concept. A coupled-field ABAQUS (Hibbit, Karlsson & Sorensen, Inc., USA) FEA model has been developed where
the constraints of the orthotropic fibre weave and end caps of this actuator design are included. The implementation of
the Maxwell pressure model that couples electrical inputs to mechanical loads using the ABAQUS user subroutine
DLOAD is the focus of this paper. Our model was used to perform a study of actuator design parameters including the
fibre weave angle, dielectric thickness, and the DEA's length. At a fibre angle of 45° relative to the longitudinal axis, no
axial deformation was predicted by our model. A weave angle above this resulted in an axial expansion during
actuation, whereas axial compression occurred if the fibre angle was less than 45°. For instance, at a fibre angle of 30°
with respect to the longitudinal axis, this model predicted a compressive axial strain of 4.5% before mechanical failure
for an actuator with an outer radius of 2mm, wall thickness of 0.5mm, and length of 20mm.
Characterization of direct and converse piezoelectricity of cellulose-based electro-active paper
Show abstract
In-plane piezoelectric charge constant of Electro-Active paper (EAPap) was investigated based on direct and converse
piezoelectric effects. EAPap samples were made with cellulose film with very thin gold electrode coated on both sides of
the film. To characterize direct piezoelectricity of EAPap, induced charge was measured when mechanical stress was
applied to EAPap. In-plane piezoelectric charge constant was extracted from the relation between induced charge and
applied in-plane normal stress. To investigate converse piezoelectricity, induced in-plane strain was measured when
electric field was applied to EAPap. Piezoelectric charge constant was also extracted from the relation of induced inplane
strain and applied electric field. Piezoelectric charge constants obtained from direct and converse piezoelectricity
are 31 pC/N and 178 x 10-12m/V for 45 degree sample, respectively. Measured piezoelectric charge constants of EAPap
provide promising potential as a piezoelectric material.
Improvement of viscoelastic effects of dielectric elastomer actuator and its application for valve devices
You-Yuan Jhong,
Chih-Ming Huang,
Chin-Chei Hsieh,
et al.
Show abstract
In this paper we investigated the actuation behavior of the antagonistically driven Dielectric Elastomer Actuators (DEAs).
The motivation is to improve the viscoelastic creeping behavior that intrinsically exists within most DEAs, since
creeping behavior may cause some unwanted effects to the performance of DEAs, especially when we apply the DEAs
to some mechanical devices which need to operate stably for a long time. Our experimental results showed that the
actuator can generate very stable displacement, make the pattern of actuator's movement more regular and take
advantage of mechanical energy in a more efficient way by coating two dielectric elastomers with different area ratios
and applying DC voltage to both of them at the same time.
An experimental study on the dynamic response of dielectric elastomer membranes
Show abstract
Dielectric Elastomer Actuators (DEAs) have received considerable attention recently due to their large strains, over
100% in some cases, when subject to an electric field. Previous research yielded a large deformation quasi-static model
that describes the out of plane deflections of clamped diaphragms. The numerical modeling results compare well with
experimental results for the same configuration. A theoretical dynamic model has also been developed for the dynamic
inflation of a spherical DEA membrane. With relevance to dynamic applications, the time varying response of dielectric
elastomer membranes configured for out-of-plane deflections has not been reported until now. In this paper, an
experimental investigation and analysis of the dynamic response of a dielectric elastomer membrane is reported. The
experiments were conducted with DEAs fabricated from VHB 4905 films and carbon grease electrodes. The
experiments covered the electromechanical spectrum by investigating membrane behavior due to (i) a voltage time varying
input and (ii) a mechanical time varying input, resulting in a combined electromechanical loading state during
the experiments. The results reveal that the response of the membrane is a departure from the classical dynamic
response of continuum membrane structures. As a result of this work, we have identified which typical modeling
assumptions are valid and hence can authentically be used to develop new dynamic predictive modeling tools.
Nanoporous carbon nanotube electrode for stable polypyrrole actuator
Show abstract
Electrochemical actuators were fabricated based on conducting polypyrrole (PPy) and acrylic elastomer substrate. An
ultrathin layer of single-wall carbon nanotubes (SWNT) was employed as the electrode for the electrochemical
deposition of PPy onto the substrate. The permeability of the nanoporous SWNT layer enabled the electrolyte solution to
penetrate the electrode and the polymerization of pyrrole both on the surface and at the interior of the substrate surface.
The resulting PPy was intimately attached to the substrate. The two materials could not be detached by any physical
means. Reversible and stable actuation has been demonstrated from the new PPy/SWNT/acrylic/SWNT/PPy bimorph structure.
Polypyrrole operating voltage limits in aqueous sodium hexafluorophosphate
Show abstract
Actuation of polypyrrole in aqueous sodium hexafluorophosphate solution has been shown to produce relatively large
strains. However little has been published on appropriate potential range of actuation in this electrolyte. This information
is clearly crucial for applications. Our particular interest is in disposable applications where a relatively small number of
cycles are needed, and maximum strain is desired. The electrochemical degradation as a function of voltage is
investigated by cycling the film between fixed voltages and measuring the charge transfer. The experiment was done on
a glassy carbon substrate in order to reduce effects of change in resistance with oxidation state, preventing actuation. The
dependence of charging on voltage and the rate of reduction in the extent of charging are measured. The voltage range
for effective operation of the device was found to be -0.4 V to 0.8 V versus a Ag/AgCl reference electrode in order to
achieve stable performance over at least 30 minutes. The mechanisms of degradation at potentials beyond 0.8 V appear
to be the substitution of hydroxyl ions in the polymer backbone, as suggested in reports on degradation of polypyrrole in
other electrolytes. An observed reduction in charge transfer rate at potentials lower than -0.4 V is consistent with a
reduction in ionic conductivity at highly reduced states, as has also been suggested in the literature.
Electrically driven mechanochemical artificial muscle: for smooth 3D movement in robotics and prosthetics
Show abstract
Ras Labs, L.L.C., is committed to producing a variety of electroresponsive smart materials that are strong,
resilient, and respond quickly and repeatedly to electrical stimuli. By effectively combining the synthetic
expertise of Ras Labs with the plasma expertise of the Princeton University Plasma Physics Laboratory
(PPPL), Ras Labs, L.L.C., is committed to producing superior electroresponsive materials and actuators.
One of the biggest challenges in developing these actuators was the interface between the embedded
electric electrodes and the electroresponsive materal because of the pronounced movement of the
electroresponsive material. Preliminary experiments explored the bonding between these electroresponsive
materials with plasma treated metals provided by PPPL. The results were encouraging, with much better
bond strengths in the plasma treated metals compared to the untreated control. Ras Labs is expanding upon
improving the attachment of the embedded electric leads to the electroresponsive materials in these
actuators using plasma treatment and other treatments to non-corrosive metal leads. Coating or
encapsulating the smart material in an elastomeric material, which acts as a "skin," can allow for the
actuator, even when removed from an electrolytic bath, to be fully operational. Strong, encapsulated,
electroresponsive smart materials will have a profound impact on prosthetics, valves, and automated
systems, particularly robotics, allowing for revolutionary designs that can move smoothly and seamlessly in
three dimensions with superb control, dexterity, and durability.
Extending applications of dielectric elastomer artificial muscle
Show abstract
Dielectric elastomers have demonstrated high energy density and high strains as well as high electromechanical
efficiency and fast speeds of response. These properties, combined with their projected low cost make them attractive for
a variety of actuator applications including linear actuators, diaphragm pumps, rotary motors, and haptic displays.
Dielectric elastomers have also been shown to offer high energy density, high efficiency, and large strains when operated
as generators. Dielectric elastomers have reached a stage of development where standardized products can be applied to
new applications. In some cases, dielectric elastomer devices are improvements over existing devices. In other cases,
however, dielectric elastomers can enable new types of devices that cannot be made with existing technologies, such as
new types of loudspeakers and power generating devices. A new dipole loudspeaker system was developed using a
commercially available push-pull diaphragm configuration. This same transducer configuration was used to develop a
new power generating system. This generator system enables a power generation of 0.06 to 0.12 W by manually displacing the device by 5 to 6 mm once a second. By introducing a voltage step-down conversion circuit, the device was able to power wireless communications, allowing the control of devices separated by a distance of a few meters. These two devices are examples of the new applications that are enabled as the dielectric elastomer technology commercially emerges. Future improvements to dielectric elastomers could enable new capabilities in clean electrical power generation from ocean waves, for example.