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Simultaneous Smart Actuating-Sensing Devices Based on Conducting Polymers

Written By

José G. Martínez, Joaquín Arias-Pardilla and Toribio F. Otero

Submitted: 24 November 2011 Published: 17 October 2012

DOI: 10.5772/51733

From the Edited Volume

Smart Actuation and Sensing Systems - Recent Advances and Future Challenges

Edited by Giovanni Berselli, Rocco Vertechy and Gabriele Vassura

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1. Introduction

Towards the end of 1970s new artificial organic materials, conducting polymers (CP), were discovered (Chiang et al., 1977; Inzelt, 2011; Shirakawa et al., 1977). Since then, most of the scientists working on CP became interested by the fact that their conductivity can shift, in a reversible way, over several orders of magnitude by oxidation/reduction (also called doping/dedoping) processes. The availability of these new organic semiconductors has opened up possibilities to rebuilt electronics and microelectronics producing flexible devices (Guo et al., 2010; Klauk, 2006; Perepichka & Perepichka, 2009; So, 2010).

Besides conductivity other properties such as stored charge, stored chemicals, volume, porosity or colour also change during doping/dedoping, under electrochemical control, in parallel with the material composition (counterion content) along the redox reactions (Otero, 2008). Any intermediate oxidation state determines a chemical equilibrium characterized by an equilibrium potential. Any physical (temperature, pressure, applied current) or chemical (electrolyte concentration) magnitude affecting the chemical equilibrium modifies the electrical potential of the material that therefore can be used as a sensor of that magnitude (Otero, 2009).

These properties, whose value changes with the material composition, are allowing the development of different devices (Onoda et al., 1999a; Otero et al., 1992a; Otero et al., 1992c; Pei & Inganäs, 1992a). Volume variations driven by oxidation/reduction reactions are being used to generate new electrical motors having different configurations of the polymeric actuators (Alici et al., 2007; Smela et al., 1993; Wu et al., 2005).

We will present devices constructed with conducting polymers based on an electrochemical reaction and working, simultaneously, as an actuator and as several sensors of the surrounding conditions. During the movement they store and release charge working as a battery: they are multifunctional devices.

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2. Electrochemical reactions in conducting polymers

Once generated (chemical or electrochemically), conducting polymers can be considered as both, classical unreactive materials having either a constant composition and a constant value of the magnitude of its physical and chemical properties; or new reactive materials varying their composition (polymeric chains, ions and solvent in different ratios) and properties along several orders of magnitude in a reversible way under electrochemical reaction (Otero, 1999), or promoted by redox agents present in solution (Kuttel et al., 2009).

2.1. p-doping

When the polymer chains are oxidized, consecutive electrons are removed from each chain generating an excess of positive charges (holes) along the chains. This excess of positive charges (lack of electrons) promotes the repulsion between the polymeric chains and the generation of free volume between them. This free space is occupied by anions arriving from the solution to compensate the emerging positive charges (keeping the electroneutrality) and solvent molecules to keep osmotic pressure balance (Huang et al., 1986; Otero, 1999; Tsai et al., 1988).

When the polymer is generated in the presence of small anions, they can be exchanged by other small anions present in solution by electrochemical reactions so a prevailing exchange of anion occurs during reaction:

(Pol0)s+n(A)sol+m(Solv)[(Poln+)s(A)n(Solv)m]gel+n(e)metalE1

where the different subscripts mean: s, solid; sol, in solution; gel indicates that the material is a gel formed by oxidized polymeric chains (Poln+) generated after the extraction of n electrons (e-) through the metal (indicated by subscript metal) from neutral polymer chains (Pol0), n anions (A-) coming from the solution to keep the gel electroneutrality and m molecules of solvent (Solv) required to keep osmotic pressure balance.

When the polymer is generated in the presence of a macroanion, due to its volume and the interaction with polymer chains, this macroanion cannot be exchanged by the electrochemical reaction keeping trapped inside the polymer film. So, in order to keep the electroneutrality, smaller cations are exchanged with the solution during the reaction:

[(Pol0)(MA)n(C+)n(Solv)m]gel[(Poln+)(MA)n]gel+n(C+)sol+m(Solv)+n(e)metalE2

where MA- is the macroanion trapped inside the polymer film and C+ are cations exchanged in order to keep the electroneutrality.

Usually, the real redox process is not as easy as expressed by reactions (1) and (2): anions and cations are exchanged simultaneously (Hillman et al., 1989; Inzelt, 2008). Usually one of the previous interchanges prevails supporting the greater percentage of charge balance (Kim et al., 2010; Lyutov et al., 2011; Orata & Buttry, 1987; Torresi & Maranhao, 1999).

2.2. n-doping

Some CP such as PEDOT (Ahonen et al., 2000), polythiophene (Arbizzani et al., 1995) or polyfluorenes (Ranger & Leclerc, 1998) have an electronic affinity high enough to allow transitions from the neutral state to a reduced state, storing negative charges (by electron injection) on the chains at high cathodic potentials. In this case, very stable solvents and salts are required, as electrolytes, to perform this redox reaction:

(Pol0)s+n(C+)sol+m(Solv)+n(e)metal[(Poln)s(C+)n(Solv)m]gelE3

where Poln- represents the reduced polymer chains after insertion of n electrons. Here, in an analogous way compared to reaction (1), an excess of negatives charges promotes repulsion between polymeric chains generating the free volume that will be occupied by cations (exchanged with solution to keep electroneutrality) and solvent (exchanged with solution to keep pressure and osmotic balance).

2.3. Double doping

Some conducting polymers can be doped both, by p-doping and by n-doping. Thus, from their neutral state they can be reduced (suffering n-doping) or oxidized (suffering p-doping). In those polymers the energy difference between both processes is the electrochemical bandgap (Arias-Pardilla et al., 2010; Otero et al., 2011).

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3. Reversible change of the electrochemical properties

Electrochemical reactions 1, 2 and 3 are reversible reactions moving through n consecutive oxidation states (Otero et al., 2012) having different content of the counterion. The value of the magnitude of those properties being a function of the material composition (electrochemical properties) can also be shifted in a reversible way under faradic control. As previously indicated, conducting polymers can be oxidized and/or reduced from their neutral state, with the entry/exit of ions and solvent. The most studied electrochemical properties of conducting polymers are: volume, colour, stored charge, stored chemicals, porosity or permselectivity, sensing responses or wetability, among others. The progressive and reversible variation of the value of these electrochemical properties allows the development of different devices and products. The change in volume will be reviewed in detail below: this is the most important property of conducting polymers for the development of actuators or artificial muscles.

3.1. Volume variations

A chain of conducting polymer in solution can be considered as an electrochemical molecular motor (Balzani et al., 2005; Davis, 1999; Otero, 2011): movementsare produced by reversible conformational changes in chains originated by oxidation/reduction reactions. The reversible conformational movement from a coil like structure to a rod like structure is produced by extraction (oxidation) or injection (reduction) of n electrons through n consecutive steps of one electron per step, together with movement of balancing counterions. This results in length variation of a free polymer chain in solution but, in polymer films three dimensional changes of volume are observed. The entanglement of the polymer chains in the film gives reversible swelling or shrinking changes of volume under reversible electrochemical stimulation (Fig. 1).

Figure 1.

Schematic representation of the reversible volume change associated with the electrochemical reaction in conducting polymer chains during oxidation/reducction during p-doping exchanging anions.

Some mechanical test machines have been developed following length or thickness variations produced by submitting the film to different potential (Bay et al., 2003; Kiefer et al., 2007; Mazzoldi et al., 1998; Spinks et al., 2002) or current (Otero et al., 2006; Otero et al., 2007c) programs. In situ Atomic Force Microscopy (AFM) technique follows film thickness variation during reverse oxidation/reduction processes (Bieńkowski et al., 2011; Cho et al., 2011; Smela & Gadegaard, 2001). In this way, it has been possible to measure a volume difference between reduced and oxidized state up to 35% (Smela & Gadegaard, 1999). The volume change depends on multiple factors such as type of polymer, synthesis conditions (potential or current applied), electrolyte and solvents used.

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4. Simultaneous sensing and actuating properties in conducting polymers

The driving reversible electrochemical reaction supports the development of simultaneous sensing and actuating properties by conducting polymer materials and by any electrochemical device based on those materials. The electrochemical working device (based on the electrochemical reaction) senses changes of any physical or chemical variable acting on the polymer reaction rate while working. This is the Le Chatelier principle applied outside equilibrium conditions (Smith, 2004). Therefore, for increasing values of the electrolyte concentrations or of the temperature working under flow of a constant current (constant reaction rate), lower values of the device potential are observed (the reaction is easier) during the transition between the same initial and final oxidation states of the materials. When a greater mechanical work is required (moving faster, applying a higher current, or a higher mechanical stress is needed to move the actuator) the reaction gives increasing potential when the device moves between the same initial and final oxidation states.

Those sensing abilities are intrinsic properties of the reaction. They are characteristics of the material reaction and of any device based on this electrochemical reaction. So, the dual and simultaneous sensing-actuation property is expected to be quantified from electrochemical equations.

The evolution of the conducting polymer film potential with time E(t) during the movement from the same initial oxidation/reduction state to the same final oxidation/reduction state driven by flow of a constant anodic current is given by a stair function (Otero et al., 2012).

E(t)=En(t)pn(t)=E1(t)p1(t)+E2(t)p2(t)+...+En(t)pn(t)E4

where:

pn(t)=u(ttn)u(ttn+1)={1,t[tn,tn+1]0,t[tn,tn+1]E4

Being tn the time while the nth electron removed from every polymeric chain and En(t):

En(t)=E0+(n1)ΔE+RT(1α)F{ln(iaFV)dln[A]eln([Pol*]initialiatFV)lnka0}E4

where E0 is the standard potential, ia is the applied current; n is the number of consecutive electrons extracted from a chain; ΔE is the increment observed in the potential when a new electron is extracted from a polymeric chain, R is the universal gas constant (R = 8.314 J K-1 mol-1); α is the symmetry factor; F is the Faraday constant (F=96485 C mol-1); V, the volume of the film; [A-] the concentration of anions (counterion) in solution; t, the time of current flow; T is the experimental temperature; d and e are the reactions orders related with the concentration of anions in solution or to that of the active centres [Pol*] in the film (sites of the polymer where a positive charge will be stored after oxidation) and ka0 is the rate constant or rate coefficient for E=E0.

Therefore, Eqs. 4 and 6 are the sensing equations: the evolution of the device potential during actuation is a function of either, driving (current) and working (temperature, electrolyte concentration and film volume) variables.

Ua(t)=iaE(t)dt=iat{E0+(n1)ΔE}+RTiat(1α)F{ln(iaFV)dln[A]lnka0}+RTVe(1α){ln([Pol*]initialiatFV)1}{[Pol*]iatFV}E4

Being electrical machines, by integration of Eq. 6 the evolution of the electrical energy consumed by the electrochemical device (Ua) during the actuation time is attained:

The consumed energy (Ua) after any constant time (t) of current flow is also a sensing function of the same variables. Fig. 2 shows the good agreement between experimental and theoretical results for the consumption of three different charges (from the same initial oxidation/reduction state, three different final oxidation/reduction states are obtained) at different experimental temperatures by flow of a constant anodic currentfor three different times of current flow.

Figure 2.

a) Anodic and cathodic experimental (full lines) and theoretical (dotted lines) chronopotentiograms obtained by flow of ±0.75 mA through a 1.6 mg pPy film (10.77 mm x 5.09 mm x 19 μm) at different temperatures (black line: 5ºC; red line: 10ºC; green line: 15ºC; blue line: 20ºC and cyan line: 25ºC) in 1 M LiClO4 aqueous solution. b) Achieved potential after different times of anodic (positive) or cathodic (negative) current flow. c) Consumed electrical energy after the same times of current flow. Reproduced from (Otero et al., 2012), with permission of American Chemical Society).

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5. Artificial muscles

In general, artificial muscles are devices attempting to reproduce composition, characteristics and capabilities of natural muscles. Different materials have been used as piezoelectrics (PZT), shape memory alloys (SMA) (Ouyang et al., 2008), carbon based materials as nanotubes (Baughman et al., 1999) or graphene (Huang et al., 2012) and polymeric gels. Also the pneumatic approach has been studied with contractile or extensional devices operated by pressurized air (Daerden & Lefeber, 2002).

Natural muscles transform chemical energy into mechanical energy and heat. Their actuation involves: a) aqueous media, b) an electric pulse arriving from the brain to the muscle through the nervous system, c) liberation of calcium ions inside the sarcomere, d) chemical reactions (ATP hydrolysis), e) conformational changes along natural polymeric chains (actin and myosin) with change of the sarcomere volume and f) water exchange. Among of the above mentioned materials for artificial muscles, conducting polymers are the most similar to natural devices including: electric pulses, polymeric chains, chemical reactions, aqueous solutions (ions and water), volume variations, and strain and stress changes. Two families of electrical polymeric actuators can be differentiated (Otero et al., 2007a; Otero, 2000; Otero, 2007):

  • Electromechanical actuators: the polymer responds to electric fields (E) and the polymer chains do not participate in chemical reactions (the structure of its intramolecular chemical bonds doesn’t change) during actuation. In this type of actuator the dimension variations are proportional to E2 for electrostrictive actuators and to E for electrostatic and electrokinetic (movement of ions and/or solvent molecules) actuators.

  • Electrochemomechanical actuators: the polymer chains respond to electric currents and participate in electrochemical or chemical reactions, changing the structure of its chemical bonds, varying their composition and originating volume changes. In this case dimensional variations are under control of the electrochemical reaction becoming proportional to consumed charge. Conducting polymers can be used for the production of this kind of actuators. Whether carbon nanotubes and graphenes based actuators are electromechanical or electrochemomechanical is still under discussion (Gimenez et al., 2012; Mukai et al., 2011). Any electrochemically reactive material that can be laminated as stable films can be used as part of electrochemomechanical actuators.

From now on we will focus on electrochemomechanical actuators. These actuators have been built using different configurations as discussed below, always containing one or several films of conducting polymers, where reaction 1, 2 or 3 takes place. Volume variations generated by reactions 1, 2 or 3 are almost isotropic, while natural muscles are anisotropic devices. So to produce anisotropy, only volume changes following length variation of the films are used, with the consequent efficiency reduction.

5.1. Bending artificial muscles

Historically the first way to transduce reversible length variations in films of conducting polymers into macroscopic movements was through a bilayer, or bimorph structure, i.e. CP/passive layer (Otero et al., 1992b; Otero et al., 1992a; Otero et al., 1992c; Pei & Inganäs, 1992a) (Fig. 3). The variation of the mechanical stress gradient generated across the bilayer interface by swelling/shrinking processes induced by the electrochemical reactions in the conducting polymer film develops a macroscopic movement of the bilayer free end by the progressive bending of the device. The direction (clockwise or anticlockwise) of the movement depends on the prevalent ionic exchange (anions or cations) of the conducting polymer film. Conducting polymers with a prevalent exchange of anions swell by oxidation, pushing the bilayer free end meanwhile conducting polymers with prevalent cation exchange shrink during oxidation, trailing the device. Different materials have been used as passive layer, for example a tape (Otero et al., 1992b; Otero et al., 1992a; Otero et al., 1992c; Pei & Inganäs, 1992a), a sputtered metal (Jager et al., 2000a; Jager et al., 2000b; Smela et al., 1993), a piece of paper (Deshpande et al., 2005b), a non conducting plastic (Higgins et al., 2003), a solid state electrolyte film (Alici et al., 2011; Baughman, 1996) or a thin film of any flexible material which is metal coated (i.e. by sputtering) (Deshpande et al., 2005a).

In a similar way it is possible to obtain bending movement from asymmetrical monolayers of the same conducting polymer, having an internal asymmetry capable of producing asymmetric swelling or shrinking across the film under the same electrochemical process (Okamoto et al., 2000; Onoda et al., 1999a; Onoda & Tada, 2004; Onoda et al., 1999b; Shakuda et al., 1993; Takashima et al., 2003; Takashima et al., 1997; Wang et al., 2002). Here half of the film has a prevalent anionic exchange, while the second half experiences a prevalent cationic exchange. These asymmetrical monolayers are obtained in two separate stages of electrogeneration using different salts and the same monomer. Other ways are being studied to produce asymmetric monolayers by physical means, for example, by growing the conducting polymer on adsorbed and porous materials (Li et al., 2004), or by electrochemical means generating a film of conducting polymer with a counterion concentration gradient (Okuzaki & Hattori, 2003; Sansiñena et al., 2003), conductivity (Nakano & Okamoto, 2001; Onoda et al., 2005) or morphology gradients (Han & Shi, 2006; Okamoto et al., 2001) by crosslinked networks.

All these bilayer devices require a counter-electrode in order to close the electrical circuit allowing the current flow. In this electrode (usually a metal) different electrochemical reactions as solvent oxidation, must occur during current flow consuming a major fraction of the electrical energy, resulting in pH variations and generating new chemicals, which can deteriorate progressively the bilayer device.

Trying to avoid the counter electrode and its associated problems, a three layer structure was proposed (Otero et al., 1992c). Initially, it was produced by using a central passive film (two sides tape) each side coated with a conducting polymer film (Fig. 3). The triple layer was immersed in an electrolyte allowing the current flow. One of the conducting polymer films acts as the anode while the second film acts as the cathode (Garcia-Cordova et al., 2011; John et al., 2008; Yao et al., 2008). But using this configuration it is also possible to obtain movement outside a liquid electrolyte media using an ionic conducting membrane to separate the two films of conducting polymers. This membrane can be obtained by solvent evaporation and UV irradiation (Blonsky & Meridian, 1997; Heuer et al., 2002; Sansinena et al., 1997; Song et al., 2002), or by formation of interpenetrated networks (Cho et al., 2007; Plesse et al., 2005; Vidal et al., 2009; Vidal et al., 2003). In this case, the two conducting polymer films are generated by chemical polymerization on the external part of the membrane. Using this approach, multilayer devices were constructed and characterized (Ikushima et al., 2009; Zainudeen et al., 2008). The three-layer configuration provides greater efficiencies of the consumed energy: the same current is used two times to produce opposite electrochemical reactions and volume variations in the conducting polymer films; the anode swells and pushes the device and the cathode shrinks and trails the device.

Figure 3.

Bilayer and three layer devices in solution, formed by conducting polymer films and non-conductive films. Described angle is also shown.

5.2. Longitudinal or linear artificial muscles

Freestanding conducting polymer films are the simplest longitudinal actuators (DellaSanta et al., 1997). Its actuation principle is based on longitudinal expansion and contraction of the polymer during ionic exchange, although expansion and contraction occur in all three dimensions, as previously indicated. To improve the performance of these actuators overcoming problems of fragility, multilayered actuators were proposed (Hara et al., 2006; Kaneto et al., 2008; Kaneto et al., 2009), in which several thin conducting polymer films and an electrolyte (ionic liquid-soaked paper) are used to develop a compact and scalable longitudinal actuator with a high work output (Ikushima et al., 2009). Also folded films with Origami shapes provide good linear movements (Okuzaki, 2008).

Fibres of conducting polymer also can be considered as longitudinal actuators. Fibres can be obtained by extrusion (Mazzoldi et al., 1998) or by chemical polymerization over a fibre-shaped substrate (Ismail et al., 2011; Lu et al., 2002), or hollow fibre solid polymer electrolyte (Plesse et al., 2010) making it possible to obtain two concentric CP films separated by the electrolytic medium, allowing its movement in air (Dobbelin et al., 2010; Plesse et al., 2009; Vidal et al., 2010; Vidal et al., 2009). Microrods (Cho et al., 2011) or nanorods (Park et al., 2009; Vlad et al., 2012) of conducting polymers and bundles of films or fibres were investigated to produce vertical displacements of weights (Lu et al., 2002). Also, conducting polymer tubes were generated using springs and helical metallic wires (Ding et al., 2003; Hara et al., 2003; Hara et al., 2005; Spinks et al., 2003b) or zigzag metal wires (Hara et al., 2004; Morita et al., 2010) as substrates, looking for uniform potential and current distribution. When individual fibres, bundles or tubes are used, a counter electrode is necessary, for the same reasons given above in the case of the bilayers.

Finally, it is possible to obtain linear displacement by combination of different bending structures as bilayers (Fuchiwaki et al., 2009; Naka et al., 2010; Otero & Broschart, 2006) or trilayers (Mutlu & Alici, 2010; Otero et al., 2007b) achieving longitudinal displacements over 60% of their original length.

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6. Sensing and tactile muscles

As mentioned above, any reactive (electrochemical) device based on conducting polymers will sense every variable influencing the electrochemical reaction rate during actuation. Following this basic principle of the chemical kinetics sensing and tactile artificial muscles have been developed.

While a current is applied to the artificial muscle, producing a mechanical work, it is possible to follow the potential achieved in the muscle at every time. Under flow of a constant current (constant reaction rate) the achieved potential is lower when a variable which favours the electrochemical reaction increases. This is the case for temperature (Garcia-Cordova et al., 2011; Ismail et al., 2011; Otero & Cortes, 2003b; Valero Conzuelo et al., 2010; Valero et al., 2010) or electrolyte concentration (Arias-Pardilla et al., 2011; Garcia-Cordova et al., 2011; Otero & Cortes, 2003b; Otero et al., 2007b; Valero Conzuelo et al., 2010). On the other hand, the potential shifts to higher values when a variable makes the reaction harder: the muscle moves larger masses (Garcia-Cordova et al., 2011; Otero et al., 2007b; Valero Conzuelo et al., 2010) or moves the mass faster by applying now rising currents (Garcia-Cordova et al., 2011; Ismail et al., 2011; Valero et al., 2011).

Being the potential evolution a sensor of the working variables, the electrical energy (U) consumed by the device during actuation and obtained by integration is also sensor:

U(t)=E(t)IdtE8

Where t is the elapsed time, E(t) is the potential evolution during the actuation time and I is the constant applied current.

When a free muscle moves driven by a constant current finds an obstacle, the potential steps to higher values, trying to produce more energy and to shift the obstacle. The potential increment detects the object and its mechanical resistance to be shifted. Related with this property, artificial muscles with tactile sensitivity have been developed too (Otero & Cortes, 2003a).

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7. Multi-devices: Actuators-sensors-battery-electrochromic

As mentioned above, different properties can be tuned simultaneously and in a reversible way during electrochemical reactions in conducting polymers. Electrochemical devices created with conducting polymers may change several of those properties, such as volume, stored charge or color, at the same time. For example, using the same configuration, changing the quantity of conducting polymer used in the device, it’s possible to obtain different optical or mechanical devices (Vidal et al., 2010).

Also, as the configuration of a three layer is the same of a battery with two conducting polymer films as electrodes, electrical charge is trapped in the actuator during electrochemical reaction. A way to recover that charge may be developed in order to recover that energy, acting now as a battery and moving the actuator in the opposite directionuntil a uniform oxidation state is attained in both polymer films (vertical position in Fig. 3).

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8. Theoretical models

Several models have been proposed to characterize the electrochemomechanical behaviour of artificial muscles. At the moment, there exist different approaches from different fields as mathematics, physics or chemical-physics.

8.1. Faradic control of the movement

As mentioned above, artificial muscles are electrochemomechanical machines controlled by the electrochemical reaction occurring while actuating. As any electrochemical reaction, actuation in conducting polymers is controlled by the charge consumed during actuation. Volume changes are not an exception: according to reactions 1, 2 or 3, volume variations will be given by the number of extracted (or inserted) charges from (or to) the polymeric chains, promoting the swelling/shrinking and the ionic exchange during reaction.

For bending bilayer or trilayer artificial muscles, it has been experimentally proven that the described angle (α in rad) follows a linear relationship with the consumed charge (Q in C):

α(t)=kQ(t)E9

where k is a constant (rad C-1) depending on every actuator system: the device (conducting polymer and isolating tape) and the electrolyte where is moving.

By definition of the angular rate of the movement (ω):

ω(t)=dα(t)dt=kdQ(t)dt=kI(t)E10

This expression confirms the faradic control of the movement: the angular rate of the movement is a linear function of the applied current. Any increment of the current produces (immediately, without any relaxing time) a faster movement of the actuator, by stopping the current flow the movement stops (the driving reaction and the film volume variation stops). Eq. 9 also indicates that the actuator is a positioning device: the same charge produces the same displacement and the charge consumed during description of a movement of one degree (α/Q = k) is constant (independent of the applied current).

The above expressions can be normalized by mass unit of active conducting polymer reacting during actuation. This allows predicting the behaviour of every artificial muscle moving in a known electrolyte made of the same material whatever the geometry of the device is (shape, thickness, surface area, etc.). That means that the same change of the specific composition (according with reactions 1, 2 or 3) per unit time produce the same angular rate in devices having different geometry. This means that experiments from one muscle are only required in order to obtain this faradic characteristic of the CP.

The faradic control of the movement has been checked with different artificial muscles made of different polymers, exchanging both anions (Otero & Cortes, 2004) or cations (Valero et al., 2011).

8.2. Bending beam method

The bending beam method (Gere & Goodno, 2009; Timoshenko, 1925) is based on the analogy existing between a bending artificial muscle and a solid-state bending beam: the study of the forces generated at the interface between the non-conductive layer, keeping its volume constant during actuation, and the conducting polymer film, varying its volume locally.

This mechanical model assumes several characteristics related with the study of traditional mechanical bending beam: (I) the thickness of the beam is small compared to the minimum radius of curvature, (II) a linear relationship exists between stress and strain of the material and (III) the Young’s modulus, Y, and the actuation expansion coefficient of the conducting polymer, α, keep constant: they do not depend on spatial location inside each layer.

The actuator curvature radius (R is the radius at the equilibrium and R0 is the initial radius) is related to either, the Young’s modulus (Y) and the thicknesses (h) of the conducting and non-conductive films (indicated by subscripts 1 and 2 respectively), and to the volume changes locally produced at the interface between both films α(t) (Pei & Inganäs, 1993b; Pei & Inganäs, 1993a; Pei & Inganäs, 1992b):

1R1R0=6α(t)(Y1h12Y2h22)2Y1Y2h1h2(h1+h2)+4(h1+h2)E11

Christophersen et al. (Christophersen et al., 2006) expanded the model by including strain and modulus variations along the direction of film thickness. Actuator’s position, rate of the movement and force generated by the actuator (Alici & Huynh, 2006; Alici et al., 2006b) were simulated and applied to the design of biomimetic device (propulsion fins) (Alici et al., 2007). Du et al. (Du et al., 2010) have developed a general model for a multilayer system (N layers) to link the actuation strain of the actuator to the bending curvature.

8.3. Finite element method

The finite elements methodology is a well know mathematical treatment for engineering designs that can be applied to solve the movement of the artificial muscles too. Alici et al. (Alici et al., 2006a; Metz et al., 2006) developed a model based on a lumped-parameter mathematical model for trilayer actuators employing the analogy between thermal strain and the real strain (due to the insertion/extraction of ions inside the polymeric film) in polypyrrole actuators actuating in air. An optimization of the geometry was required, in order to obtain the greater output properties from a determined input voltage. Shapiro et al. (Shapiro & Smela, 2007) developed a two dimensional model (along a full area) to obtain curvature and angular moment from bilayer and trilayer actuators. Thus, they combined the results from the previous method (bending beam method) with finite element method to attain a solution. Another example of the employment of this method was carried out by Gutta et al. who applied it to the study the movement of a cylindrical ionic-polymer metal composite actuator (Gutta et al., 2011).

8.4. Equivalent transmission line model

Electrochemical systems, as many other systems, can be assimilated to electrical circuits and electrochemomechanical actuators have been treated by the equivalent transmission line method. This resource is a practical tool due to the great number of facilities available to the study of electrical circuits through different steps or modules. Such treatments are employed by engineers and physicists, or electrochemists, in order to explain the claimed capacitive behaviour of CP (Albery & Mount, 1993; Bisquert et al., 2000; Paasch, 2000). Ren et al. (Ren & Pickup, 1995) proposed equivalent electrical circuits to model the electron transport and electron transfer in composite pPy-PSS films based on Albery’s works. Fang et al. (Fang et al., 2008; Yang et al., 2008) have developed a scalable method including dynamic actuation performance under a given voltage input, joining three different modules for different aspects of the actuator: electrochemical dynamics, stress-generation by charge and mechanical dynamics. Shoa et al. (Shoa et al., 2011) developed a dynamic electromechanical method for electrochemically driven conducting polymer actuators based on a 2-D impedance model using an RC transmission line equivalent circuit to predict the charge transfer during actuation. Besides, a mechanical model (based on the bending beam model) is considered after the equivalent circuit that simulates ion “diffusion” through the thickness and electronic resistance along the length (Shoa et al., 2010). If the angular movement is not linear along the full geometry of the actuator, the bending beam method has to be modified, for example for cantilever type conducting polymer actuators (Alici, 2009).

From all these kind of models, it is possible to employ only one or several of them at the same time in order to obtain the best required model (Woosoon et al., 2007).

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9. Actuators applications

The investigation of these devices is mainly performed in academic laboratories. Nevertheless a rising number of applications and products are emerging with pioneering companies that are being incorporated by large multinationals. So Creganna Tactx Medical and Bayer MaterialScience recently acquired a pair of companies working in the field, indicating the potential of these technologies. Also EAMEX from Japan is developing actuators for biomedical and robotic applications. NASA and ESA space agencies consider polymeric actuators as preferential technologies, and the European Scientific Network for Artificial Muscles (ESNAM) has started funded by the European Union. Many different applications can be found in literature. The following is a summary of a few of them, both macroscopic and microscopic.

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10. Published papers and patents evolution

An indication of the initiation and fast growth of the field is given by bibliographic and patents evolution. As can be observed, the literature related to conducting polymers actuators starts from 1990 (Fig. 4.a) reaching a maximum in 2006 with 45 papers, an excellent value for such a specific topic. After that, around 30 papers have been published every year. Fig. 4.b shows exponential evolution of citations with a value of almost 2000 in 2010. A similar evolution is observed in Fig. 4.c for patents, reaching a maximum in 2009 with 180 patents.

Figure 4.

Evolution of a) published papers, b) citations and c) patents for “conducting polymer & actuator”, from the ISI web of Knowledge® and Scopus®.

11. Future and challenges

Although a hard work has been performed, it does not exist yet an uncontroversial model for the description of the new reactive polymers and devices based on these reactive polymer gels whose composition and properties mimic those from artificial organs in mammals. New models should include concepts from very different fields of knowledge as electrochemistry, mechanics, polymer science and thermodynamics. In those systems, electrochemical reactions produce structural (conformational) changes in the polymeric chains and macroscopic volume changes related to the composition change of the material. Those aspects are not considered in the classical chemical kinetic models. Conducting polymer films should be used as models for the study and quantification of chemical kinetics under structural control with the aim to develop a new structural chemical model, able to quantify conformational changes and structural information in conducting polymers and in biological reactions originating life in living cells.

This model will allow the synthesis of new conducting polymers providing a more precise control of structural changes and intermolecular forces (polymer-ion interactions) with the reaction. Those materials should be used in a new generation of polymeric actuators able to overcome current limitations, opening possibilities for new applications.

Other factors, such as configuration, manufacture of the actuators, design of the electric contacts or electrolytic media (solid or liquid) are also very important for the improvement of the electrochemomechanical actuators. This is a multidisciplinary field, a lot of work performed by specialists from different disciplines is required in order to attain a good control and modelling of both, devices and soft robots.

Acknowledgement

Authors acknowledge financial support from Spanish Government (MCINN) Projects MAT2008-06702, MAT2011-24973, Seneca Foundation Project 08684/PI/08 and to the European network for Artificial Muscles ESNAM. Jose G. Martinez acknowledges Spanish Education Ministry for a FPU grant (AP2010-3460).

References

  1. 1. AhonenH. J.LukkariJ.KankareJ.2000n- and p-doped poly(3,4-ethylenedioxythiophene): Two electronically conducting states of the polymer. Macromolecules, 3318678767930024-9297
  2. 2. AlberyW. J.MountA. R.1993Application of A Transmission-Line Model to Impedance Studies on A Poly(Vinylferrocene)-Modified Electrode. J.Chem.Soc.Faraday T., 8923273310956-5000
  3. 3. AliciG.HuynhN. N.2006Predicting force output of trilayer polymer actuatorsSens. Actuat. A-Phys, 13226166250924-4247
  4. 4. AliciG.MetzP.SpinksG. M.2006a). A methodology towards geometry optimization of high performance polypyrrole (PPy) actuators. Smart Mater.Struct., 1522432520964-1726
  5. 5. AliciG.MuiB.CookC.2006bBending modeling and its experimental verification for conducting polymer actuators dedicated to manipulation applicationsSens. Actuat. A-Phys, 12623964040924-4247
  6. 6. AliciG.SpinksG.HuynhN. N.SarmadiL.MinatoR.2007Establishment of a biomimetic device based on tri-layer polymer actuators-propulsion fins.Bioinspir. Biomim., 22S18S301748-3182
  7. 7. AliciG.2009An effective modelling approach to estimate nonlinear bending behaviour of cantilever type conducting polymer actuatorsSens. Actuat. B-Chem, 14112842920925-4005
  8. 8. AliciG.GundersonD.2009A bio-inspired robotic locomotion system based on conducting polymer actuatorsIn: 2009 IEEE/ASME International Conference on Advanced Intelligent Mechatronics9981004IEEE, 978-1-42442-852-6New York.
  9. 9. AliciG.PunningA.SheaH. R.2011Enhancement of actuation ability of ionic-type conducting polymer actuators using metal ion implantationActuat. B-Chem, 157172840925-4005
  10. 10. ArbizzaniC.CatellaniM.MastragostinoM.MingazziniC.1995N-doped and p-doped polydithieno[3,4-b-3’,4’-d] thiophene- a narrow-band gap polymer for redox supercapacitors. Electrochim. Acta, 4012187118760013-4686
  11. 11. Arias-PardillaJ.WalkerW.WudlF.OteroT. F.2010Reduction and Oxidation Doping Kinetics of an Electropolymerized Donor-Acceptor Low-Bandgap Conjugated Copolymer.J. Phys. Chem. B, 1144012777127841520-6106
  12. 12. Arias-PardillaJ.PlesseC.KhaldiA.VidalF.ChevrotC.OteroT. F.2011Self-supported semi-interpenetrating polymer networks as reactive ambient sensorsJ. Electroanal. Chem., 6521-237431572-6657
  13. 13. BalzaniV.CrediA.FerrerB.SilviS.VenturiM.2005Artificial molecular motors and machines: Design principles and prototype systemsSpringer-Verlag, 03401022
  14. 14. BaughmanR. H.1996Conducting polymer artificial musclesSynth. Met., 7833393530379-6779
  15. 15. BaughmanR. H.CuiC. X.ZakhidovA. A.IqbalZ.BarisciJ. N.SpinksG. M.WallaceG. G.MazzoldiA.De RossiD.RinzlerA. G.JaschinskiO.RothS.KerteszM.1999Carbon nanotube actuators. Science, 2845418134013440036-8075
  16. 16. BayL.WestK.Sommer-LarsenP.SkaarupS.BenslimaneM.2003A conducting polymer artificial muscle with 12% linear strain. Adv. Mater., 1543103130935-9648
  17. 17. BieńkowskiK.StrawskiM.SzklarczykM.2011The determination of the thickness of electrodeposited polymeric films by AFM and electrochemical techniques. J. Electroanal. Chem., 66211962031572-6657
  18. 18. BisquertJ.BelmonteG. G.SantiagoF. F.FerriolsN.YamashitaM.PereiraE. C.2000Application of a distributed impedance model in the analysis of conducting polymer filmsElectrochem.Commun., 286016051388-2481
  19. 19. BlonskyP. M.MeridianI.1997Structurally stable gelled electrolytes, US Patent 5648011.
  20. 20. CarpiF.De RossiD.2005Electroactive polymer-based devices for e-textiles in biomedicine.IEEE T. Inf. Technol. B, 932953181089-7771
  21. 21. ChiangC. K.FincherC. R.ParkY. W.HeegerA. J.ShirakawaH.LouisE. J.GauS. C.MacdiarmidA. G.1977Electrical-Conductivity in Doped Polyacetylene. Phys.Rev. Lett., 3917109811010031-9007
  22. 22. ChoM.SeoH.NamJ.ChoiH.KooJ.LeeY.2007High ionic conductivity and mechanical strength of solid polymer electrolytes based on NBr/ionic liquid and its application to an electrochemical actuator. Sens. Actuat. B-Chem, 128170740925-4005
  23. 23. ChoM. S.ChoiJ. J.KimT. S.LeeY.2011In situ three-dimensional analysis of the linear actuation of polypyrrole micro-rod actuators using optical microscopySens. Actuat. B-Chem, 15612182210925-4005
  24. 24. ChristophersenM.ShapiroB.SmelaE.2006Characterization and modeling of PPy bilayer microactuators- Part 1. Curvature. Sens. Actuat. B-Chem, 11525966090925-4005
  25. 25. DaerdenF.LefeberD.2002Pneumatic Artificial Muscles: actuators for robotics and automationEur. J. Mech. Environ. Eng., 47110211371-6980
  26. 26. DavisA. P.1999Nanotechnology- Synthetic molecular motors. Nature, 40167491201210028-0836
  27. 27. De RossiD.CarpiF.GalantiniF.2009Functional Materials for Wearable Sensing, Actuating and Energy HarvestingIn: Biomedical Applications of Smart Materials, Nanotechnology and Micro/Nano Engineering. 247256Trans Tech Publications Ltd, 978-3-90815-823-3Stafa-Zurich.
  28. 28. Della SantaA.MazzoldiA.de RossiD.1996Steerable Microcatheters Actuated by Embedded Conducting Polymer Structures. J. Intel. Mat. Syst. Str., 732923000104-5389X.
  29. 29. Della SantaA.De RossiD.MazzoldiA.1997Performance and work capacity of a polypyrrole conducting polymer linear actuator. Synth. Met., 902931000379-6779
  30. 30. DeshpandeS. D.KimJ.YunS. R.2005aNew electro-active paper actuator using conducting polypyrrole: actuation behaviour in LiClO4 acetonitrile solutionSynth. Met., 149153580379-6779
  31. 31. DeshpandeS. D.KimJ.YunS. R.2005bStudies on conducting polymer electroactive paper actuators: Effect of humidity and electrode thicknessSmart Mater. Struct., 1448768800964-1726
  32. 32. DingJ.LiuL.SpinksG. M.ZhouD.WallaceG. G.GillespieJ.2003High performance conducting polymer actuators utilising a tubular geometry and helical wire interconnectsSynth. Met., 13833913980379-6779
  33. 33. DobbelinM.MarcillaR.Pozo-GonzaloC.MecerreyesD.2010Innovative materials and applications based on poly(3,4-ethylenedioxythiophene) and ionic liquids. J. Mater. Chem., 2036761376220959-9428
  34. 34. DuP.LinX.ZhangX.2010A multilayer bending model for conducting polymer actuatorsSens. Actuat. A-Phys, 16312402460924-4247
  35. 35. FangY.TanX. O.ShenY. T.XiN.AliciG.2008A scalable model for trilayer conjugated polymer actuators and its experimental validationMater. Sci. Eng., C, 2834214280928-4931
  36. 36. FuchiwakiM.TanakaK.KanetoK.2009Planate conducting polymer actuator based on polypyrrole and its applicationSens. Actuat. A-Phys, 15022722760924-4247
  37. 37. Garcia-CordovaF.ValeroL.IsmailY. A.OteroT. F.2011Biomimetic polypyrrole based all three-in-one triple layer sensing actuators exchanging cationsJ. Mater. Chem., 214317265172720959-9428
  38. 38. GereJ. M.GoodnoB. J. (2009). Mechanics of Materials 4th Ed., Cengage Learning, 0-53455-397-4
  39. 39. GimenezP.MukaiK.AsakaK.HataK.OikeH.OteroT. F.2012Capacitive and faradic charge components in high-speed carbon nanotube actuatorElectrochim. Acta, 60177-183177 EOF183 EOF0013-4686
  40. 40. GuoY.YuG.LiuY.2010Functional Organic Field-Effect TransistorsAdv. Mater., 2240442744471521-4095
  41. 41. GurselA.ValerieD.PhilippeR.GeoffS.2009Conducting polymer microactuators operating in airJ. Micromech. Microeng., 1920250170960-1317
  42. 42. GuttaS.RealmutoJ.WoosoonY.KimK. J.2011Dynamic model of a cylindrical ionic polymer-metal composite actuator. Proceedings of 8th International Conference on Ubiquitous Robots and Ambient Intelligence (URAI), Incheon.
  43. 43. HanG.ShiG.2006Electrochemical actuator based on single-layer polypyrrole filmSens. Actuat. B-Chem, 11312592640925-4005
  44. 44. HaraS.ZamaT.SewaS.TakashimaW.KanetoK.2003Polypyrrole-metal coil composites as fibrous artificial musclesChem. Lett., 3298008010366-7022
  45. 45. HaraS.ZamaT.AmetaniA.TakashimaW.KanetoK.2004Enhancement in electrochemical strain of a polypyrrole-metal composite film actuatorJ. Mater. Chem., 1418272427250959-9428
  46. 46. HaraS.ZamaT.TanakaN.TakashimaW.KanetoK.2005Artificial fibular muscles with 20% strain based on polypyrrole-metal coil composites. Chem.Lett., 3467847850366-7022
  47. 47. HaraS.ZamaT.TakashimaW.KanetoK.2006Tris(trifluoromethylsulfonyl)methide-doped polypyrrole as a conducting polymer actuator with large electrochemical strain. Synth.Met., 1562-43513550379-6779
  48. 48. HeX. M.LiC.ChenF. G.ShiG. Q.2007Polypyrrole microtubule actuators for seizing and transferring microparticlesAdv. Funct. Mater., 1715291129170161-6301X.
  49. 49. HeuerH. W.WehrmannR.KirchmeyerS.2002Electrochromic window based on conducting poly (3,4-ethylenedioxythiophene)poly(styrene sulfonate). Adv. Funct. Mater., 12289940161-6301X.
  50. 50. HigginsS. J.LovellK. V.RajapakseR. M. G.WalsbyN. M.2003Grafting and electrochemical characterisation of poly-(3,4-ethylenedioxythiophene) films, on Nafion and on radiation-grafted polystyrenesulfonate-polyvinylidene fluoride composite surfacesJ. Mater. Chem., 1310248524890959-9428
  51. 51. HillmanA. R.LovedayD. C.SwannM. J.EalesR. M.HamnettA.HigginsS. J.BruckensteinS.WildeC. P.1989Charge Transport in Electroactive Polymer-FilmsFaraday Discuss. Chem. Soc., 88151-1630301-7249
  52. 52. HuangW. S.HumphreyB. D.MacDiarmid. A. G.1986Polyaniline, A Novel Conducting Polymer- Morphology and Chemistry of Its Oxidation and Reduction in Aqueous-Electrolytes. J. Chem. Soc., Faraday Trans. I, 822385-24000300-9599
  53. 53. HuangY.LiangJ.ChenY.2012The application of graphene based materials for actuators. J. Mater. Chem., 229367136790959-9428
  54. 54. IkushimaK.JohnS.YokoyamaK.NagamitsuS.2009A practical multilayered conducting polymer actuator with scalable work outputSmart. Mater. Struct., 18990964-1726
  55. 55. InzeltG.2008Redox Transformations and Transport Processes. In: Conducting Polymers, Scholz, F. 169224 , Springer-Verlag Berlin, 978-3-54075-929-4Heidelberg (Germany).
  56. 56. InzeltG.2011Rise and rise of conducting polymersJ. Solid State Electrochem., 157-8171117181432-8488
  57. 57. IsmailY. A.MartínezJ. G.HarrasiA. S. A.KimS. J.OteroT. F.2011Sensing characteristics of a conducting polymer/hydrogel hybrid microfiber artificial muscleActuat. B-Chem, Vol. 0pp. 0925-4005
  58. 58. JagerE. W. H.SmelaE.InganäsO.LundstromI.1999Polypyrrole microactuators. Synth. Met., 1021-3130913100379-6779
  59. 59. JagerE. W. H.InganäsO.LundstromI.2000aMicrorobots for micrometer-size objects in aqueous media: Potential tools for single-cell manipulation.Science, 2885475233523380036-8075
  60. 60. JagerE. W. H.SmelaE.InganäsO.2000bMicrofabricating conjugated polymer actuators.Science, 2905496154015450036-8075
  61. 61. JagerE. W. H.InganäsO.LundstromI.2001Perpendicular actuation with individually controlled polymer microactuators. Adv. Mater., 13176790935-9648
  62. 62. JagerE. W. H.ImmerstrandC.PetersonK. H.MagnussonK.E.LundströmI.InganäsO.2002The Cell Clinic: Closable Microvials for Single Cell Studies.Biomed. Microdev, 431771871387-2176
  63. 63. JamesT.PatrickA.TimothyF.AngelaC.Mike DelZ.IanH.2007The application of conducting polymers to a biorobotic fin propulsorBioinspir. Biomim., 22S61748-3190
  64. 64. JohnS.AliciG.CookC.2008Frequency response of polypyrrole trilayer actuator displacementProceedings of Electroactive Polymer Actuators and Devices (Eapad) 2008, San Diego (USA).
  65. 65. KanetoK.SuematsuH.YamatoK.2008Training effect and fatigue in polypyrrole-based artificial muscles.Bioinspir. Biomim., 330350051748-3182
  66. 66. KanetoK.SuematsuH.YamatoK.2009Conducting Polymer Soft Actuators based on Polypyrrole-Training Effect and Fatigue.In: Artificial Muscle Actuators Using Electroactive Polymers, Vincenzini, P., Bar-Cohen, Y. & Carpi, F. 122130Trans Tech Publications Inc., 16620356Zuerich, Switzerland.
  67. 67. KieferR.ChuS. Y.KilmartinP. A.BowmakerG. A.CooneyR. P.Travas-SejdicJ.2007Mixed-ion linear actuation behaviour of polypyrroleElectrochim. Acta, 527238623910013-4686
  68. 68. KieferR.MandviwallaX.ArcherR.TjahyonoS. S.WangH.MacDonald. B.BowmakerG. A.KilmartinP. A.Travas-SejdicJ.2008The application of polypyrrole trilayer actuators in microfluidics and roboticsProceedings of Electroactive Polymer Actuators and Devices (Eapad).
  69. 69. KimJ. H.LauK. T.ShepherdR.WuY.WallaceG.DiamondD.2008Performance characteristics of a polypyrrole modified polydimethylsiloxane (PDMS) membrane based microfluidic pumpSensors and Actuators A: Physical, 14812392440924-4247
  70. 70. KimL. T. T.SelO.Biemme-ChouvyC.GabrielliC.Laberty-RobertC.PerrotH.SanchezC.2010Proton transport properties in hybrid membranes investigated by ac-electrogravimetryElectrochem.Commun., 128113611391388-2481
  71. 71. KlaukH.Ed2006Organic Electronics: Materials, Manufacturing, and ApplicationsWiley-VCH Verlag, 978-3-52731-264-1Weinheim.
  72. 72. KuttelC.StemmerA.WeiX.2009Strain response of polypyrrole actuators induced by redox agents in solutionSens. Actuat. B-Chem, 14124784840925-4005
  73. 73. LeeK. K. C.MunceN. R.ShoaT.CharronL. G.WrightG. A.MaddenJ. D.YangV. X. D.2009Fabrication and characterization of laser-micromachined polypyrrole-based artificial muscle actuated cathetersSens. Actuat. A-Phys, 15322302360924-4247
  74. 74. LiW. G.JohnsonC. L.WangH. L.2004Preparation and characterization of monolithic polyaniline-graphite composite actuatorsPolymer4514476947750032-3861
  75. 75. LuW.FadeevA. G.QiB. H.SmelaE.MattesB. R.DingJ.SpinksG. M.MazurkiewiczJ.ZhouD. Z.WallaceG. G.MacFarlane. D. R.ForsythS. A.ForsythM.2002Use of ionic liquids for pi-conjugated polymer electrochemical devices.Science, 29755839839870036-8075
  76. 76. LyutovV.TsakovaV.BundA.2011Microgravimetric study on the formation and redox behavior of poly(2-acrylamido-2-methyl-1-propanesulfonate)-doped thin polyaniline layers. Electrochim. Acta, 5613480348110013-4686
  77. 77. MazzoldiA.Degl’InnocentiC.MichelucciM.De RossiD.1998Actuative properties of polyaniline fibers under electrochemical stimulationMater. Sci. Eng., C, 6165720928-4931
  78. 78. Mc GovernS.et al.2009Finding NEMO (novel electromaterial muscle oscillator): a polypyrrole powered robotic fish with real-time wireless speed and directional controlSmart Mater. Struct., 1890950090964-1726
  79. 79. Mc GovernS. T.AbbotM.EmeryR.AliciG.TruongV. T.SpinksG. M.WallaceG. G.2010Evaluation of thrust force generated for a robotic fish propelled with polypyrrole actuatorsPolym. Int., 5933573640959-8103
  80. 80. MetzP.AliciG.SpinksG. M.2006A finite element model for bending behaviour of conducting polymer electromechanical actuatorsSens. Actuat. A-Phys, 1301-110924-4247
  81. 81. MoritaT.ChidaY.HoshinoD.FujiyaT.NishiokaY.Fabrication and characterization of a polypyrrole soft actuator having corrugated structuresMol. Cryst. Liq. Cryst., 519121-127121 EOF127 EOF1542-1406
  82. 82. MoritaT.ChidaY.HoshinoD.FujiyaT.NishiokaY.2010Fabrication and Characterization of a Polypyrrole Soft Actuator Having Corrugated StructuresMol. Cryst. Liq. Cryst., 519121-127121 EOF127 EOF1542-1406
  83. 83. MukaiK.AsakaK.HataK.OteroT. F.OikeH.2011High-Speed Carbon Nanotube Actuators Based on an Oxidation/Reduction Reaction.Chem.-Eur. J., 173910965109711521-3765
  84. 84. MutluR.AliciG.2010A Multistable Linear Actuation Mechanism Based on Artificial MusclesJ. Mech. Des., 132111110011050-0472
  85. 85. NakaY.FuchiwakiM.TanakaK.2010A micropump driven by a polypyrrole-based conducting polymer soft actuatorPolym. Int., 5933523561097-0126
  86. 86. NakanoT.OkamotoY.2001Synthetic Helical Polymers: Conformation and FunctionChem. Rev., 1011240134038ISSN
  87. 87. OkamotoT.TadaK.OnodaM.2000Bending machine using anisotropic polypyrrole filmsJpn. J. Appl. Phys. 1, 395A285428580021-4922
  88. 88. OkamotoT.KatoY.TadaK.OnodaM.2001Actuator based on doping/undoping-induced volume change in anisotropic polypyrrole filmThin Solid Films3931-23833870040-6090
  89. 89. OkuzakiH.HattoriT.2003Electrically induced anisotropic contraction of polypyrrole filmsSynth. Met., 135-13645-460379-6779
  90. 90. OkuzakiH.2008A biomorphic origami actuator fabricated by folding a conducting paper. J. Phys. Conf. Ser., 12710120011742-6596
  91. 91. OnodaM.OkamotoT.TadaK.NakayamaH.1999aPolypyrrole films with anisotropy for artificial muscles and examination of bending behaviorJpn. J. Appl. Phys. 2, 389ABL1070L10720021-4922
  92. 92. OnodaM.TadaK.NakayamaH.1999bPolypyrrole films with anisotropySynth. Met., 1021-3132113220379-6779
  93. 93. OnodaM.TadaK.2004Anisotropic bending machine using conducting polypyrroleIEICE Trans. Electron., E87C21281350916-8524
  94. 94. OnodaM.ShonakaH.TadaK.2005A self-organized bending-beam electrochemical actuatorCurr. Appl. Phys., 521942011567-1739
  95. 95. OrataD.ButtryD. A.1987Determination of ion populations and solvent content as functions of redox state and pH in polyanilineJ. Am. Chem. Soc., 10912357435810000-2786
  96. 96. OteroT.CascalesJ.Fernandez-RomeroA.2007aAttempting a classification for electrical polymeric actuators. Proceedings of Electroactive Polymer Actuators and Devices (EAPAD), San Diego.
  97. 97. OteroT. F.AnguloE.RodriguezJ.SantamariaC.1992aElectrochemomechanical Properties from A Bilayer- Polypyrrole Nonconducting and Flexible Material Artificial Muscle. J. Electroanal. Chem., 3411-23693750022-0728
  98. 98. OteroT. F.AnguloE.RodriguezJ.SantamariaC.1992bDispositivos laminares que emplean polímeros conductores capaces de provocar movimientos mecánicos, ES Patent 2 048 086.
  99. 99. OteroT. F.RodriguezJ.SantamariaC.1992cMúsculos artificiales formados por multicapas: polímeros conductores-no conductores, ES Patent 2 062 930.
  100. 100. OteroT. F.1999Conducting polymers, electrochemistry, and biomimicking processes. In: Modern Aspects of Electrochemistry, Bockris, J.O.M., White, R.E. & Conway, B.E. 307434Kluwer Academic/Plenum Publ, 00769924York.
  101. 101. OteroT. F.2000Biomimicking materials with smart polymers. In: Structural biological materials. Design and structure-properties relationships, Elices, M. & Cahn, R.W. 187220Pergamon Materials Series, 0-08043-416-9The Netherlands).
  102. 102. OteroT. F.CortesM. T.2003aArtificial muscles with tactile sensitivityAdv. Mater., 1542792820935-9648
  103. 103. OteroT. F.CortesM. T.2003bA sensing muscleSens. Actuators, B, 961-21521560925-4005
  104. 104. OteroT. F.CortesM. T.2004Artificial muscle: movement and position controlChem. Commun., Vol. 32842851359-7345
  105. 105. OteroT. F.ArenasG. V.CascalesJ. J. L.2006Effect of the doping ion on the electrical response of a free-standing polypyrrole strip subjected to different preloads: Perspectives and limitations associated with the use of these devices as actuatorsMacromolecules3926955195560024-9297
  106. 106. OteroT. F.BroschartM.2006Polypyrrole artificial muscles: a new rhombic element. Construction and electrochemomechanical characterization. JAppl. Electrochem., 3622052140002-1891X.
  107. 107. OteroT. F.2007Artificial muscles. In: Handbook of Conducting Polymers, Skotheim, T.A., Elsenbaumer, R.L. & Reynolds, J.R. 591623CRC Press, ISBN Boca Raton.
  108. 108. OteroT. F.CortesM. T.ArenasG. V.2007bLinear movements from two bending triple-layersElectrochim. Acta, 533125212580013-4686
  109. 109. OteroT. F.LopezCascales. J. J.VazquezArenas. G.2007cMechanical characterization of free-standing polypyrrole filmMater. Sci. Eng., C, 27118220928-4931
  110. 110. OteroT. F.2008Artificial Muscles, Sensing and Multifunctionality. In: Intelligent Materials, Shahinpoor, M. & Schenider, H.-J. 142190Royal Society of Chemistry, 978-0-85404-335-4Cambridge (U.K.).
  111. 111. OteroT. F.2009Soft, wet, and reactive polymers. Sensing artificial muscles and conformational energy. J. Mater. Chem., 19681-6890959-9428
  112. 112. OteroT. F.2011From Electrochemically-Driven Conformational Polymeric States to Macroscopic Sensing and Tactile Muscles. In: From Non-Covalent Assemblies to Molecular Machines, Sauvage, J.-P. & Gaspard, P. pp. Wiley-VCH Verlag & Co., ISBN Weinheim, Germany.
  113. 113. OteroT. F.Arias-PardillaJ.HerreraH.SeguraJ. L.SeoaneC.2011Electropolymerization of naphthaleneamidinemonoimide-modified poly(thiophene). Phys. Chem. Chem. Phys., 133716513165161463-9076
  114. 114. OteroT. F.SánchezJ. J.MartinezJ. G.2012Biomimetic Dual Sensing-Actuators based on Conducting Polymers. Galvanostatic Theoretical Model for Actuators Sensing TemperatureJ. Phys. Chem. B, 11617527952901089-5647
  115. 115. OuyangP. R.TjiptoprodjoR. C.ZhangW. J.YangG. S.2008Micro-motion devices technology: The state of arts reviewInt. J. Adv. Manuf. Technol., 385-64634780268-3768
  116. 116. PaaschG.2000The transmission line equivalent circuit model in solid-state electrochemistryElectrochem. Commun., 253713751388-2481
  117. 117. ParkS. J.ChoM. S.NamJ. D.KimI. H.ChoiH. R.KooJ. C.LeeY.2009The linear stretching actuation behavior of polypyrrole nanorod in AAO templateSens. Actuat. B-Chem, 13525925960925-4005
  118. 118. PedeD.SmelaE.JohanssonT.JohanssonM.InganäsO.1998A general-purpose conjugated-polymer device array for imagingAdv. Mater., 1032332370935-9648
  119. 119. PeiQ.InganäsO.1993aElectrochemical applications of the bending beam method; a novel way to study ion transport in electroactive polymersSolid State Ionics601-31611660167-2738
  120. 120. PeiQ.InganäsO.1993bElectrochemical applications of the bending beam method. 2. Electroshrinking and slow relaxation in polypyrroleJ. Phys. Chem., 9722603460410022-3654
  121. 121. PeiQ. B.InganäsO.1992aConjugated Polymers and the Bending Cantilever Method- Electrical Muscles and Smart Devices. Adv. Mater., 442772780935-9648
  122. 122. PeiQ. B.InganäsO.1992bElectrochemical Applications of the Bending Beam Method.1. Mass-Transport and Volume Changes in Polypyrrole During Redox. J. Phys. Chem., 962510507105140022-3654
  123. 123. PerepichkaI. F.PerepichkaD. F.Eds2009Handbook of Thiophene-Based Materials: Applications in Organic Electronics and Photonics. John Wiley & Sons Ltd.,978-0-47005-732-2Chichester (UK).
  124. 124. PlesseC.VidalF.RandriamahazakaH.TeyssieD.ChevrotC.2005Synthesis and characterization of conducting interpenetrating polymer networks for new actuatorsPolymer4618777177780032-3861
  125. 125. PlesseC.VidalF.TeyssieD.ChevrotC.2009Conducting IPN Fibers: a new design for linear actuation in open airIn: Artificial Muscle Actuators using Electroactive Polymers Vincenzini, P., Bar-Cohen, Y. & Carpi, F. 5358Trans Tech Publicactions Ltd., 16620356Zurich (Switzerland).
  126. 126. PlesseC.VidalF.TeyssieD.ChevrotC.2010Conducting polymer artificial muscle fibres: toward an open air linear actuationChem. Commun., 4617291029121359-7345
  127. 127. Ramírez-GarcíaS.DiamondD.2007Biomimetic, low power pumps based on soft actuators. Sens. Actuat. A-Phys, 135 1 229235 ,0924-4247
  128. 128. RangerM.LeclercM.1998Optical and electrical properties of fluorene-based pi-conjugated polymers. Can. J. Chem., 7611157115770008-4042
  129. 129. RenX.PickupP. G.1995Impedance measurements of ionic conductivity as a probe of structure in electrochemically deposited polypyrrole filmsJ. Electroanal. Chem., 3961-23593641572-6657
  130. 130. RoemerM.KurzenknabeT.OesterschulzeE.NicolosoN.2002Microactuators based on conducting polymers.Anal. Bioanal. Chem., 37387547571618-2642
  131. 131. SansinenaJ. M.OlazabalV.OteroT. F.daFonseca. C. N. P.De PaoliM. A.1997A solid state artificial muscle based on polypyrrole and a solid polymeric electrolyte working in airChem. Commun., Vol. 22221722181359-7345
  132. 132. SansiñenaJ. M.GaoJ. B.WangH. L.2003High-performance, monolithic polyaniline electrochemical actuators. Adv. Funct. Mater., 1397037090161-6301X.
  133. 133. ShakudaS.MoritaS.KawaiT.YoshinoK.1993Dynamic Characteristics of Bimorph with Conducting Polymer GelJpn. J. Appl. Phys. 1, 3211A514351460021-4922
  134. 134. ShapiroB.SmelaE.2007Bending Actuators with Maximum Curvature and Force and Zero Interfacial StressJ. Intel. Mat. Syst. Str., 1821811860104-5389X.
  135. 135. ShirakawaH.LouisE. J.MacdiarmidA. G.ChiangC. K.HeegerA. J.1977Synthesis of Electrically Conducting Organic Polymers- Halogen Derivatives of Polyacetylene, (Ch)X. J. Chem. Soc., Chem. Commun., Vol. 165785800022-4936
  136. 136. ShoaT.MaddenJ. D.FekriN.MunceN. R.YangV. X. D.2008Conducting polymer based active catheter for minimally invasive interventions inside arteries.Proceedings of 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2008.
  137. 137. ShoaT.MaddenJ. D. W.MunceN. R.YangV.2010Analytical modeling of a conducting polymer-driven catheterPolym.Int., 5933433511097-0126
  138. 138. ShoaT.YooD. S.WalusK.MaddenJ. D. W.2011A Dynamic Electromechanical Model for Electrochemically Driven Conducting Polymer ActuatorsIEEE ASME Trans. Mechatronics, 16142491083-4435
  139. 139. SmelaE.InganäsO.PeiQ. B.LundstromI.1993Electrochemical Muscles- Micromachining Fingers and Corkscrews. Adv. Mater., 596306320935-9648
  140. 140. SmelaE.InganäsO.LundstromI.1995Controlled Folding of Micrometer-Size Structures.Science, 2685218173517380036-8075
  141. 141. SmelaE.1999A microfabricated movable electrochromic "pixel" based on polypyrroleAdv. Mater., 1116134313450935-9648
  142. 142. SmelaE.GadegaardN.1999Surprising volume change in PPy(DBS): An atomic force microscopy study. Adv. Mater., 11119539570935-9648
  143. 143. SmelaE.GadegaardN.2001Volume change in polypyrrole studied by atomic force microscopyJ. Phys. Chem. B, 10539939594051089-5647
  144. 144. SmelaE.ChristophersenM.PrakashS. B.UrdanetaM.DandinM.AbshireP.2007Integrated cell-based sensors and "cell clinics" utilizing conjugatedpolymer actuators. Proceedings of SPIE- The International Society for Optical Engineering.
  145. 145. SmithE. B.2004Basic Chemical ThermodynamicsImperial College Press., 1-86094-445-0
  146. 146. SoF.Ed2010Organic electronics : materials, processing, devices and applicationsCRC Press, 978-1-42007-290-7Boca Raton (USA).
  147. 147. SongM. K.ChoJ. Y.ChoB. W.RheeH. W.2002Characterization of UV-cured gel polymer electrolytes for rechargeable lithium batteriesJ. Power Sources, 11012092150378-7753
  148. 148. SpinksG. M.LiuL.WallaceG. G.ZhouD.2002Strain Response from Polypyrrole Actuators under LoadAdv. Funct. Mater., 126-74374401616-3028
  149. 149. SpinksG. M.WallaceG. G.DingJ.ZhouD.XiB.GillespieJ.2003aIonic liquids and polypyrrole helix tubes: bringing the electronic Braille screen closer to reality. Proceedings of Smart Structures and Materials 2003: Electroactive Polymer Actuators and Devices (EAPAD), San Diego, USA.
  150. 150. SpinksG. M.ZhouD. Z.LiuL.WallaceG. G.2003bThe amounts per cycle of polypyrrole electromechanical actuatorsSmart. Mater. Struct., 1234684720964-1726
  151. 151. TakashimaW.UesugiT.FukuiM.KanekoM.KanetoK.1997Mechanochemoelectrical effect of polyaniline filmSynth. Met., 851-3139513960379-6779
  152. 152. TakashimaW.PandeyS. S.KanetoK.2003Bi-ionic actuator by polypyrrole filmsSynth. Met., 1351-361620379-6779
  153. 153. TimoshenkoS.1925Analysis of bi-metal thermostatsJ. Opt. Soc. Am., 1132332550093-4119
  154. 154. TorresiR. M.MaranhaoS. L. D.1999Anion and solvent exchange as a function of the redox states in polyaniline films. J. Electrochem. Soc., 14611417941820013-4651
  155. 155. TsaiE. W.PajkossyT.RajeshwarK.ReynoldsJ. R.1988Anion-Exchange Behavior of Polypyrrole MembranesJ. Phys. Chem., 9212356035650022-3654
  156. 156. ValeroConzuelo. L.Arias-PardillaJ.Cauigh-RodríguezJ. V.SmitM. A.OteroT. F.2010Sensing and Tactile Artificial Muscles from Reactive MaterialsSensors102638-26742638 EOF2674 EOF1424-8220
  157. 157. ValeroL.Arias-PardillaJ.SmitM.Cauich-RodríguezJ.OteroT. F.2010Polypyrrole Free-Standing electrodes sense temperature or current during reaction. Polym. Int., 59337-3421097-0126
  158. 158. ValeroL.Arias-PardillaJ.Cauich-RodríguezJ.SmitM. A.OteroT. F.2011Characterization of the movement of polypyrrole-dodecylbenzenesulfonate-perchlorate/tape artificial muscles. Faradaic control of reactive artificial molecular motors and musclesElectrochim. Acta, 5610372137260013-4686
  159. 159. VidalF.PoppJ. F.PlesseC.ChevrotC.TeyssieD.2003Feasibility of conducting semi-interpenetrating networks based on a poly(ethylene oxide) network and poly(3,4-ethylenedioxythiophene) in actuator design. J. Appl. Polym. Sci., 9013356935770021-8995
  160. 160. VidalF.PlesseC.PalapratG.JugerJ.CiterinJ.KheddarA.ChevrotC.TeyssieD.2009Synthesis and Characterization of IPNs for Electrochemical ActuatorsIn: Artificial Muscle Actuators Using Electroactive Polymers, Vincenzini, P., BarCohen, Y. & Carpi, F. 817Trans Tech Publications Ltd, 978-3-90815-827-1Stafa-Zurich.
  161. 161. VidalF.PlesseC.AubertP. H.BeouchL.Tran VanF. o.PalapratG.VergeP.YammineP.CiterinJ.KheddarA.SauquesL.ChevrotC.TeyssieD.2010Poly(3,4-ethylenedioxythiophene)-containing semi-interpenetrating polymer networks: a versatile concept for the design of optical or mechanical electroactive devices. Polym. Int., 5933133201097-0126
  162. 162. VladA.DutuC. A.JedrasikP.SodervallU.GohyJ. F.MelinteS.2012Vertical single nanowire devices based on conducting polymers.Nanotechnology23250957-4484
  163. 163. WallaceG.CampbellT.InnisP.2007Putting function into fashion: Organic conducting polymer fibres and textilesFiber. Polym., 821351421229-9197
  164. 164. WangH. L.GaoJ. B.SansiñenaJ. M.Mc CarthyP.2002Fabrication and characterization of polyaniline monolithic actuators based on a novel configuration: Integrally skinned asymmetric membrane. Chem. Mater., 146254625520897-4756
  165. 165. WilsonS. A.JourdainR. P. J.ZhangQ.DoreyR. A.BowenC. R.WillanderM.WahabQ. U.Al-hilliS. M.NurO.QuandtE.JohanssonC.PagounisE.KohlM.MatovicJ.SamelB.van der WijngaartW.JagerE. W. H.CarlssonD.DjinovicZ.WegenerM.MoldovanC.IosubR.AbadE.WendlandtM.RusuC.PerssonK.2007New materials for micro-scale sensors and actuators: An engineering review. Mat. Sci. Eng. R, 561-611290092-7796X.
  166. 166. WoosoonY.JoonsooL.KwangJ. K.2007An artificial muscle actuator for biomimetic underwater propulsorsBioinspir. Biomim., 22S311748-3190
  167. 167. WuY.ZhouD.SpinksG. M.InnisP. C.MegillW. M.WallaceG. G.2005TITAN: a conducting polymer based microfluidic pumpSmart. Mater. Struct., 146151115160964-1726
  168. 168. YangF.XiaoboT.AliciG.2008Robust Adaptive Control of Conjugated Polymer ActuatorsIEEE Trans. Control Syst. Technol., 1646006121063-6536
  169. 169. YaoQ.AliciG.SpinksG. A.2008Feedback control of tri-layer polymer actuators to improve their positioning ability and speed of responseSens. Actuat. A-Phys, 14411761840924-4247
  170. 170. ZainudeenU. L.CareemM. A.SkaarupS.2008PEDOT and PPy conducting polymer bilayer and trilayer actuatorsSens. Actuat. B-Chem, 13424674700925-4005

Written By

José G. Martínez, Joaquín Arias-Pardilla and Toribio F. Otero

Submitted: 24 November 2011 Published: 17 October 2012