Actuator properties

As is the case for smart materials, intelligent textiles have the property to respond to their environment, sometimes in a clearly perceptible way, but sometimes at the molecular level, completely invisible to the observer. They cover a wide range of technologies, from materials with shape-memory properties or sensing and actuating properties, to entire systems based on information technology5. 

The main electroactive polymers, known for their actuating properties, are listed below ... 

The hydrogel of perfluorosulphonate ionomer is also an effective electroactive material. This material already shows actuating properties as a film of 0.2mm in a DC field, with application of only 3 V16. The principle of the deforming mechanism is similar to that for other polyelectrolyte gels. The response time and durability are much better than for... 

We will now discuss in detail the sensing and actuating properties of these waves. 

Sugino T, Kiyohara K, Takeuchi I et al (2009) Actuator properties of the complexes composed by carbon nanotube and ionic liquid the effects of additives. Sensor Actuat B Chem 141 179-186... 

The sensor-actuator properties of hydrogels can also be used to generate a liquid flow or a pressure. Adapting the fundamental principle of the osmotic pump of Theeuwes and Yum (Theeuwes and Yum 1976) so far two types of pumps are described. 

Temperature-sensitive hydrogels with actuator properties show aLCST behaviour. They are swollen at low temperatures and shrink by exceeding of the volume phase transition temperature T. The best known hydrogel with LCST behaviour is PNIPAAm (Fig. 9). 

Today the number of electroactive polymers has grown substantially. There currently exists a wide variety of such materials, ranging from rigid carbon-nanotubes to soft dielectric elastomers. A number of reviews and overviews have been prepared on these and other materials for use as artificial muscles and other applications [1, 2, 7, 10, 11, 13-28]. The next section will provide a survey of the most common electrically activated EAP technologies and provide some pertinent performance values. The remainder of the paper will focus specifically on dielectric elastomers. Several actuation properties for these materials are summarized in Table 1.1 along with other actuation technologies including mammalian muscle. It is important to note that data was recorded for different materials under different conditions so the information provided in the table should only be used as a qualitative comparison tool. 

These materials have shown piezoelectric responses after appropriate poling [18]. Their piezoelectric actuation properties are typically worse than ceramic piezoelectric crystals however, they have the advantages of being lightweight, flexible, easily formed, and not brittle. Additionally, while ceramics are limited to strains on the order of 0.1%, ferroelectric polymers are capable of strains of 10% [91] and very high electromechanical coupling efficiencies [93]. 

PTBA also exhibits excellent strain fixity (ability to retain its actuated shape upon cooling) and strain recovery. In its softened state PTBA also possesses excellent actuation properties with a breakdown field strength in excess of 250 MV/m, a maximum strain of 335% in area, a maximum actuation stress of 3.2 MPa and an energy density of 1.2 J cm , values that rival even the best of the conventional dielectric elastomer materials. The BSEP is the first active material that possesses bistable actuation with high strain and specific power density. 

A number of approaches have been explored for increasing the dielectric constant of elastomers for DEs. The most common approach involves the addition of high dielectric constant filler materials to an elastomer host. Silicone is of particular interest for this type of approach as it possesses good actuation properties to begin with, is readily available in gel form, and has a low dielectric constant. Results thus far do not appear particularly promising increases in dielectric constant have been met with concomitant increases in dielectric loss and reductions in dielectric breakdown strength [184—186]. It has also been shown that the elastic modulus is affected by the addition of filler [187]. 

Mazzoldi A, Della Santa A, De Rossi D (1999) Conducting polymer actuators properties and modeling. In Osada Y, De Rossi D (eds) Polymer sensors and actuators. Springer, Heidelberg, pp 207-244... 

The actuation properties of IPMC are presented in. [6—10] By applying a voltage of 0.2-3 V on an IPMC film, bending towards the anode occurred. An increase in voltage level (up to 6 or 7 V) causes larger bending displacement along with nonlinear saturation in displacement. IPMCs also work very well in water or blood environments. 

Different modeling approaches have been introduced, Shahinpoor et al. [6—11]. Fig. 2.7 shows the step response of a 20 x 5 x 0.2 mm IPMC cantilever strip which is actuated by a 1.5 input volt. Two types of IPMCs, PVP (polyvinyl pyrolidone) treated and PVP non-treated, are compared with each other in terms of maximum deflection and settling time. The steady state deflection achieved for the PVP treated sample is about 40% higher than the non-treated sample, and the settling time is reduced significantly, showing fast actuation properties. 

Kofod G, McCarthy DN, Stoyanov H, Kollosche M, Risse S, Ragusch H, Rychkov D, Dansachmuller M, Wache R (2010) Materials science on the nano-scale for improvements in actuation properties of dielectric elastomer actuators. Proc SPIE 7642 764201. doi 10.1117/ 12.847281... 

In this section, consideration will be given to research in which conducting polymers have been combined with other materials to create a composite with improved actuation properties. This might involve the incorporation of a stiffer material (e.g. carbon nanotubes) to improve the stresses produced, or the inclusion of a gel to increase the amount of strain generated, albeit in a weaker actuator. 

Risse, S., Kussmaul, B., Kr Ger, H., Kofod, G., 2012. Synergistic improvement of actuation properties with compatibilized high permittivity filler. Adv. Eunct. Mater. 22,3958-3962. 

It is obvious that certain actuating properties of transducer materials are far beyond the ones of conventional actuating principles. This enables to use them in special application areas such as lightweight construction, active vibration control, or the development of highly dynamic systems for instance. 

The use of this helical interconnect results in improvements in electrochemical efficiency (percentage of polymer actually oxidized or reduced). It has recently been shown that incorporation of carbon nanotubes into polyaniline fibers [145] results in materials with improved actuation properties. 

Hannaford, B., and Winters, J. (1990). Actuator properties and movement control biological and technological models. In J. M. Winters and S. L-Y. Woo, (eds.). Multiple Muscle Systems Biomechanics and Movement Organization, Springer-Verlag, Berlin, pp. 101-120. 

To study the actuation properties of Ni-doped MFR IPMCs, first the current and displacement in response to an applied voltage were measured in range from —3V to 3V. Due to the oxidation of Ni, the charging process starts at 0.8 V and electric breakdown takes place at 1.8 V. However, after the first cycle of operation, the cmrent density and the displacement remained rather imchanged (see Fig. 3.5). The actuation performance is shown in Fig. 3.6. The displacement of Ni-doped MFR IPMCs was mea-smed when a square pulse was applied using chrono-potentiometry with 2 s pulse dmation and controlled current. The results indicate that the actua-... 

Due to the superior actuator properties and the commercial impact of NiTi alloys, the following discussions will focus on these alloys. NiTi- and NiTiCu-based wires are commercially available with a range of transformation temperatures and in all diameters down to 25 pm. The same alloys are also... 

The shape that the SM actuator recovers to when heated is imprinted into the alloy by an annealing process. For instance, to fabricate a coil spring a SM wire is wound around a mandrel and annealed for 1... 2 hours at 350. .. 500 °C. Annealing temperature and duration have a strong influence on the actuators properties, such as the trainable two-way effect, the effect stability, and the hysteresis behavior. 

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