151
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Stenull O, Lubensky TC. Unconventional elasticity in smectic-A elastomers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:011706. [PMID: 17677470 DOI: 10.1103/physreve.76.011706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 04/30/2007] [Indexed: 05/16/2023]
Abstract
We study two aspects of the elasticity of smectic- A elastomers that make these materials genuinely and qualitatively different from conventional uniaxial rubbers. Under strain applied parallel to the layer normal, monodomain smectic- A elastomers exhibit a drastic change in Young's modulus above a threshold strain value of about 3%, as has been measured in experiments by [Nishikawa and Finkelmann, Macromol. Chem. Phys. 200, 312 (1999)]. Our theory predicts that such strains induce a transition to a smectic-C-like state and that it is this transition that causes the change in elastic modulus. We calculate the stress-strain behavior as well as the tilt of the smectic layers and the molecular orientation for strain along the layer normal, and we compare our findings with the experimental data. We also study the electroclinic effect in chiral smectic-A* elastomers. According to experiments by [Lehmann, Nature (London) 410, 447 (2001)] and [Köhler, Appl. Phys. A 80, 381 (2003)], this effect leads in smectic-A* elastomers to a giant or, respectively, at least very large lateral electrostriction. Incorporating polarization into our theory, we calculate the height change of smectic-A* elastomer films in response to a lateral external electric field, and we compare this result to the experimental findings.
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Affiliation(s)
- Olaf Stenull
- Fachbereich Physik, Universität Duisburg-Essen, Campus Duisburg, 47048 Duisburg, Germany
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152
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Gorkunov MV, Giesselmann F, Lagerwall JPF, Sluckin TJ, Osipov MA. Molecular model for de Vries type smectic- A -smectic- C phase transition in liquid crystals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:060701. [PMID: 17677211 DOI: 10.1103/physreve.75.060701] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Indexed: 05/16/2023]
Abstract
We develop both phenomenological and molecular-statistical theory of smectic- A -smectic- C phase transition with anomalously weak smectic layer contraction. Using a general mean-field molecular model, we demonstrate that a relatively simple interaction potential suffices to describe the transition both in conventional and de Vries type smectics. The theoretical results are in excellent agreement with experimental data. The approach can be used to describe tilting transitions in other soft matter systems.
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Affiliation(s)
- M V Gorkunov
- Department of Mathematics, University of Strathclyde, Glasgow G1 1XH, United Kingdom
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153
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Stenull O. Smectic elastomer membranes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:051702. [PMID: 17677079 DOI: 10.1103/physreve.75.051702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2007] [Indexed: 05/16/2023]
Abstract
We present a model for smectic elastomer membranes which includes elastic and liquid-crystalline degrees of freedom. Based on our model, we determined the qualitative phase diagram of a smectic elastomer membrane using mean-field theory. This phase diagram is found to comprise five phases, viz., smectic- A -flat, smectic- A -crumpled, smectic- C -flat, smectic- C -crumpled, and smectic- C -tubule phases, where in the latter phase, the membrane is flat in the direction of mesogenic tilt and crumpled in the perpendicular direction. The transitions between adjacent phases are second-order phase transitions. We study in some detail the elasticity of the smectic- C -flat and the smectic- C -tubule phases which are associated with a spontaneous breaking of in-plane rotational symmetry. As a consequence of the Goldstone theorem, these phases exhibit soft elasticity characterized by the vanishing of in-plane shear moduli.
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Affiliation(s)
- Olaf Stenull
- Fachbereich Physik, Universität Duisburg-Essen, Campus Duisburg, Duisburg, Germany
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154
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Ikeda T, Mamiya JI, Yu Y. Photomechanics of liquid-crystalline elastomers and other polymers. Angew Chem Int Ed Engl 2007; 46:506-28. [PMID: 17212377 DOI: 10.1002/anie.200602372] [Citation(s) in RCA: 842] [Impact Index Per Article: 49.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Muscle is a transducer that can convert chemical energy into mechanical motion. To construct artificial muscles, it is desirable to use soft materials with high mechanical flexibility and durability rather than hard materials such as metals. For effective muscle-like actuation, materials with stratified structures and high molecular orders are necessary. Liquid-crystalline elastomers (LCEs) are superior soft materials that possess both the order of liquid crystals and the elasticity of elastomers (as they contain polymer networks). With the aid of LCEs, it is possible to convert small amounts of external energy into macroscopic amounts of mechanical energy. In this Review, we focus on light as an energy source and describe the recent progress in the area of soft materials that can convert light energy into mechanical energy directly (photomechanical effect), especially the photomechanical effects of LCEs with a view to applications for light-driven LCE actuators.
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Affiliation(s)
- Tomiki Ikeda
- Chemical Resources Laboratory, Tokyo Institute of Technology, R1-11, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
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155
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Affiliation(s)
- Kenji Urayama
- Department of Materials Chemistry, Kyoto University, Kyoto 615-8510, Japan
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156
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Kushibe Y, Matsuyama A. Tricritical point induced by smectic ordering of a nematic gel. J Chem Phys 2007; 126:034901. [PMID: 17249897 DOI: 10.1063/1.2429661] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The authors study volume phase transitions of a nematic gel immersed in a liquid crystal (LC) solvent, which shows a second-order nematic-smectic A phase transition (NST). Combining Flory's elastic energy [Principles of Polymer Chemistry (Cornell University Press, Ithaca, 1953)] for a swelling of the gel with the McMillan model [Phys. Rev. A 4, 1238 (1971)] for smectic ordering, the authors calculate the equilibrium swelling of the gel and smectic order parameters as a function of temperature. The authors take into account an attractive interaction parameter c between the gel and LC solvents. On increasing the value of the coupling constant c, a second-order NST of the gel is changed to a first-order one and a continuous volume phase transition of the gel is changed to a discontinuous one. The authors find a tricritical point of the gel induced by smectic ordering.
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Affiliation(s)
- Yoshinari Kushibe
- Department of Bioscience and Bioinformatics, Faculty of Computer Science and System Engineering, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka 820-8502, Japan
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157
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Ikeda T, Mamiya JI, Yu Y. Photomechanik flüssigkristalliner Elastomere und anderer Polymere. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200602372] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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158
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159
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Abstract
The ability of polymers to move actively in response to an external stimulus such as heat or light is of high scientific and technological significance. In any instance stimuli-responsive effects on the molecular level are converted into macroscopic movement, whereby generally two different moving behaviors have to be differentiated for polymer-based materials: the shape-memory effect and the shape-changing capability. Basic concepts for the molecular design of suitable polymer architectures for shape-memory polymers as well as tailored programming processes are presented. The thermally-induced shape-memory effect of polymers is described as well as the extension of this concept to other stimuli than heat. Indirect actuation of the thermally-induced effect by IR-irradiation, electric current, humidity or alternating magnetic fields are outlined as well as recent work on light-induced shape-memory polymers. For shape-changing polymers, two basic concepts are presented: shape changes occurring during phase orientation of liquid crystal elastomers (LCE) and the photomechanical effect based on photoisomerization of moieties, such as azo-groups incorporated in suitable polymer systems.
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Affiliation(s)
- Marc Behl
- Center for Biomaterial Development, Institute of Polymer Research, GKSS Research Center Geesthacht, Kantstr. 55, D-14513 Teltow, Germany.
| | - Andreas Lendlein
- Center for Biomaterial Development, Institute of Polymer Research, GKSS Research Center Geesthacht, Kantstr. 55, D-14513 Teltow, Germany.
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160
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Stenull O, Lubensky TC. Soft elasticity in biaxial smectic and smectic-C elastomers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 74:051709. [PMID: 17279928 DOI: 10.1103/physreve.74.051709] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Revised: 09/05/2006] [Indexed: 05/13/2023]
Abstract
Ideal (monodomain) smectic-A elastomers cross-linked in the smectic-A phase are simply uniaxial rubbers, provided deformations are small. From these materials smectic-C elastomers are produced by a cooling through the smectic-A to smectic-C phase transition. At least in principle, biaxial smectic elastomers could also be produced via cooling from the smectic-A to a biaxial smectic phase. These phase transitions, respectively, from Dinfinityh to C2h and from Dinfinityh to D2h symmetry, spontaneously break the rotational symmetry in the smectic planes. We study the above transitions and the elasticity of the smectic-C and biaxial phases in three different but related models: Landau-like phenomenological models as functions of the Cauchy-Saint-Laurent strain tensor for both the biaxial and the smectic-C phases and a detailed model, including contributions from the elastic network, smectic layer compression, and smectic-C tilt for the smectic-C phase as a function of both strain and the c-director. We show that the emergent phases exhibit soft elasticity characterized by the vanishing of certain elastic moduli. We analyze in some detail the role of spontaneous symmetry breaking as the origin of soft elasticity and we discuss different manifestations of softness like the absence of restoring forces under certain shears and extensional strains.
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Affiliation(s)
- Olaf Stenull
- Fachbereich Physik, Universität Duisburg-Essen, Campus Essen, 45117 Essen, Germany
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161
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Li MH, Keller P. Artificial muscles based on liquid crystal elastomers. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2006; 364:2763-77. [PMID: 16973488 DOI: 10.1098/rsta.2006.1853] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
This paper presents our results on liquid crystal (LC) elastomers as artificial muscle, based on the ideas proposed by de Gennes. In the theoretical model, the material consists of a repeated series of main-chain nematic LC polymer blocks, N, and conventional rubber blocks, R, based on the lamellar phase of a triblock copolymer RNR. The motor for the contraction is the reversible macromolecular shape change of the chain, from stretched to spherical, that occurs at the nematic-to-isotropic phase transition in the main-chain nematic LC polymers. We first developed a new kind of muscle-like material based on a network of side-on nematic LC homopolymers. Side-on LC polymers were used instead of main-chain LC polymers for synthetic reasons. The first example of these materials was thermo-responsive, with a typical contraction of around 35-45% and a generated force of around 210 kPa. Subsequently, a photo-responsive material was developed, with a fast photochemically induced contraction of around 20%, triggered by UV light. We then succeeded in preparing a thermo-responsive artificial muscle, RNR, with lamellar structure, using a side-on nematic LC polymer as N block.Micrometre-sized artificial muscles were also prepared. This paper illustrates the bottom-up design of stimuli-responsive materials, in which the overall material response reflects the individual macromolecular response, using LC polymer as building block.
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Affiliation(s)
- Min-Hui Li
- Institut Curie, CNRS UMR168, 26 Rue d'Ulm, 75248 Paris Cedex 05, France.
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162
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163
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Affiliation(s)
- Yanlei Yu
- Department of Materials Science, Fudan University, 220 Handan Road, Shanghai 200433, China.
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164
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Schmidt AM. Electromagnetic Activation of Shape Memory Polymer Networks Containing Magnetic Nanoparticles. Macromol Rapid Commun 2006. [DOI: 10.1002/marc.200600225] [Citation(s) in RCA: 394] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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165
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Gabert AJ, Verploegen E, Hammond PT, Schrock RR. Synthesis and Characterization of ABA Triblock Copolymers Containing Smectic C* Liquid Crystal Side Chains via Ring-Opening Metathesis Polymerization Using a Bimetallic Molybdenum Initiator. Macromolecules 2006. [DOI: 10.1021/ma060243x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrea J. Gabert
- Department of Chemistry, Rm 6-331, Department of Materials Science and Engineering, and Department of Chemical Engineering, Rm 66-550, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
| | - Eric Verploegen
- Department of Chemistry, Rm 6-331, Department of Materials Science and Engineering, and Department of Chemical Engineering, Rm 66-550, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
| | - Paula T. Hammond
- Department of Chemistry, Rm 6-331, Department of Materials Science and Engineering, and Department of Chemical Engineering, Rm 66-550, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
| | - Richard R. Schrock
- Department of Chemistry, Rm 6-331, Department of Materials Science and Engineering, and Department of Chemical Engineering, Rm 66-550, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
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166
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Farrell B, Do Shope C, Brownell WE. Voltage-dependent capacitance of human embryonic kidney cells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:041930. [PMID: 16711859 PMCID: PMC2778024 DOI: 10.1103/physreve.73.041930] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2004] [Revised: 07/26/2005] [Indexed: 05/09/2023]
Abstract
We determine membrane capacitance, C as a function of dc voltage for the human embryonic kidney (HEK) cell. C was calculated from the admittance, Y, obtained during a voltage ramp when the HEK cell was held in whole-cell patch-clamp configuration. Y was determined at frequencies of 390.625 and from the measured current, i obtained with a dual-sinusoidal stimulus. We find that the fractional increase in the capacitance, C is small ( < 1%) and grows with the square of the voltage, Psi. C can be described by: C=C(0)(1+alpha(Psi+psi(s))2)[where C(0): Capacitance at 0 volts, psi(s): Difference in surface potential between cytoplasmic and extracellular leaflets and alpha: Proportionality constant]. We find that alpha and psi(s) are 0.120 (+/- 0.01) V(-2) and -0.073 (+/-0.017 V in solutions that contain ion channel blockers and 0.108 (+/- 0.29) V(-2) and -0.023 (+/- 0.009) V when 10 mM sodium salicylate was added to the extracellular solution. This suggests that salicylate does not affect the rate at which C grows with Psi, but reduces the charge asymmetry of the membrane. We also observe an additional linear differential capacitance of about (-46 fFV(-1)) in about 60% of the cells, this additional component acts simultaneously with the quadratic component and was not observed when salicylate was added to the solution. We suggest that the voltage dependent capacitance originates from electromechanical coupling either by electrostriction and/or Maxwell stress effects and estimate that a small electromechanical force (approximately equal to 1 pN) acts at physiological potentials. These results are relevant to understand the electromechanical coupling in outer hair cells (OHCs) of the mammalian cochlea, where an asymmetric bell-shaped C versus Psi relationship is observed upon application of a similar field. Prestin, a membrane protein expressed in OHCs is required to observe this function. When we compare the total charge contributions from HEK cell membrane (7 x 10(4) electrons, 10 pF cell) with that determined for prestin transfected cells (up to 5 x 10(6) electrons) we conclude that the charge contributions from the collective motion of membrane proteins and lipids in the field is dwarfed relative to that when prestin is present. We suggest that the capacitance-voltage relationships should be similar to that observed for HEK cells for OHCs that do not express prestin in their membranes.
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Affiliation(s)
- Brenda Farrell
- Department of Otolaryngology and Head and Neck Surgery, Baylor College of Medicine, Houston, TX 77030, USA.
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167
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Stannarius R, Aksenov V, Bläsing J, Krost A, Rössle M, Zentel R. Mechanical manipulation of molecular lattice parameters in smectic elastomers. Phys Chem Chem Phys 2006; 8:2293-8. [PMID: 16688312 DOI: 10.1039/b600839a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Smectic liquid crystalline elastomers (SLCE) represent unique materials that combine a 1-D molecular lattice arrangement and orientational order with rubber-elasticity mediated by a polymer network. Such materials may exhibit large thermo-mechanical, opto-mechanical and electro-mechanical effects, due to the coupling of macroscopic sample geometry and microscopic structural features. It is shown that the molecular layer dimensions in the smectic phases can be influenced reversibly by macroscopic strain of the material. We present a microscopic model on the basis of experimental results obtained by mechanical dilatation measurements, optical interferometry, X-ray scattering, (13)C NMR, FTIR and polarizing microscopy data. The model gives an explanation of the controversial results obtained in different types of smectic elastomers.
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Affiliation(s)
- R Stannarius
- Otto-von-Guericke-Universität Magdeburg, Institut für Experimentelle Physik, Germany.
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168
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Kato T, Nakamura T, Agari Y, Ochi M. Relation between thermal conductivity and network formation with polymerizable liquid crystals. J Appl Polym Sci 2006. [DOI: 10.1002/app.25470] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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169
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Deindörfer P, Geiger T, Schollmeyer D, Ye JH, Zentel R. Semicarbazides as gel forming agents for common solvents and liquid crystals. ACTA ACUST UNITED AC 2006. [DOI: 10.1039/b510474b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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170
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171
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Abstract
This paper describes the early conception and latest developments of electroactive polymer (EAP)-based sensors, actuators, electronic components, and power sources, implemented as wearable devices for smart electronic textiles (e-textiles). Such textiles, functioning as multifunctional wearable human interfaces, are today considered relevant promoters of progress and useful tools in several biomedical fields, such as biomonitoring, rehabilitation, and telemedicine. After a brief outline on ongoing research and the first products on e-textiles under commercial development, this paper presents the most highly performing EAP-based devices developed by our lab and other research groups for sensing, actuation, electronics, and energy generation/storage, with reference to their already demonstrated or potential applicability to electronic textiles.
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Affiliation(s)
- Federico Carpi
- Interdepartmental Research Centre E. Piaggio, University of Pisa, 56126 Pisa, Italy.
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172
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Harris KD, Bastiaansen CWM, Lub J, Broer DJ. Self-assembled polymer films for controlled agent-driven motion. NANO LETTERS 2005; 5:1857-60. [PMID: 16159238 DOI: 10.1021/nl0514590] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Reliable stimuli-responsive materials make up a vital part of molecular medicine and on-chip diagnostics. Here, we describe such a material which exhibits rapid, large-amplitude, reversible deformations and which is formed in a simple, one-material, one-step, self-assembly process. The material is a polymer network comprised of discrete molecular actuators which anisotropically expand in response to their driving stimuli. Tuning the relative orientation of the actuators with respect to one another creates expansion variations throughout a sample, and this is exploited to induce macroscopic motion. The deformation directions are pre-engineered by the molecular positioning, and extremely fast response times and high sensitivity are observed. We describe water- and pH-controlled motion, and we anticipate that the techniques are extendable to other biologically or industrially relevant agents.
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Affiliation(s)
- Kenneth D Harris
- Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands.
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173
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174
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Hiraoka K, Sagano W, Nose T, Finkelmann H. Biaxial Shape Memory Effect Exhibited by Monodomain Chiral Smectic C Elastomers. Macromolecules 2005. [DOI: 10.1021/ma050642c] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kazuyuki Hiraoka
- Center for Nano Science and Technology, Department of Nanochemistry, Tokyo Polytechnic University, 1583 Iiyama, Atsugi-shi 243-0297, Japan, and Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 31, D-79104 Freiburg i. Br., Germany
| | - Wataru Sagano
- Center for Nano Science and Technology, Department of Nanochemistry, Tokyo Polytechnic University, 1583 Iiyama, Atsugi-shi 243-0297, Japan, and Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 31, D-79104 Freiburg i. Br., Germany
| | - Takuhei Nose
- Center for Nano Science and Technology, Department of Nanochemistry, Tokyo Polytechnic University, 1583 Iiyama, Atsugi-shi 243-0297, Japan, and Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 31, D-79104 Freiburg i. Br., Germany
| | - Heino Finkelmann
- Center for Nano Science and Technology, Department of Nanochemistry, Tokyo Polytechnic University, 1583 Iiyama, Atsugi-shi 243-0297, Japan, and Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Str. 31, D-79104 Freiburg i. Br., Germany
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175
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Adams JM, Warner M. Soft elasticity in smectic elastomers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:011703. [PMID: 16089983 DOI: 10.1103/physreve.72.011703] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Indexed: 05/03/2023]
Abstract
We investigate the soft elastic modes of smectic elastomers, that is shape change without energy cost. We use a microscopic model for their nonlinear elasticity, similar to those used for nematic elastomers. We consider two different phases of smectic elastomer; the biaxial smectic A for a simple illustration, and smectic C phases which are of great practical significance. We show that only one nontrivial trajectory of the director gives soft deformations. We give a geometrical interpretation of this soft elastic mode and give an explicit example.
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Affiliation(s)
- J M Adams
- Cavendish Laboratory, University of Cambridge, UK
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176
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177
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Urayama K, Kondo H, Arai YO, Takigawa T. Electrically driven deformations of nematic gels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:051713. [PMID: 16089557 DOI: 10.1103/physreve.71.051713] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2005] [Indexed: 05/03/2023]
Abstract
The electrically driven deformations of side chain nematic networks swollen by nematic solvents (nematic gels) have been investigated. The strains of freely suspended gels between electrodes were measured as a function of field strength (E) . The deformation of the gels composed of a network and solvent with identical signs of dielectric anisotropy (Delta epsilon) is dominated by the electrically induced alignment of the nematogens. As a result, the stretching direction is variable according to the sign of Delta epsilon: The gel with positive or negative Delta epsilon is elongated parallel or normal to the field axis, respectively. The maximum strain among the samples examined is as large as 20% at E approximately equal to 0.5 MV/m. The gels composed of a network and solvent with opposite signs of Delta epsilon are compressed along the field axis since the electrostrictive effect becomes dominant because of a large reduction in the mesogen alignment effect due to the discord in the director directions of the constituent nematogens. The gels in the isotropic phase show compressive strains along the field direction in proportion to E2 purely originating from electrostriction, independently of the sign of Delta epsilon. The nematic gels are quickly deformed within a second upon field application, while the shape recovery after field removal requires a finite time on the order of 10(3) s, which reflects the structural relaxation in the polydomain texture from the oriented to the random state. The influences of elastic modulus as well as network nematicity on the electrical deformation are also examined.
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Affiliation(s)
- Kenji Urayama
- Department of Material Chemistry, Kyoto University, Kyoto 615-8510, Japan.
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178
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Xie P, Zhang R. Liquid crystal elastomers, networks and gels: advanced smart materials. ACTA ACUST UNITED AC 2005. [DOI: 10.1039/b413835j] [Citation(s) in RCA: 162] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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179
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Kim G. Electroactive polymer composites as a tactile sensor for biomedical applications. Macromol Res 2004. [DOI: 10.1007/bf03218445] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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180
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Huang JP. New nonlinear dielectric materials: linear electrorheological fluids under the influence of electrostriction. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:042501. [PMID: 15600441 DOI: 10.1103/physreve.70.042501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2004] [Indexed: 05/24/2023]
Abstract
The usual approach to the development of new nonlinear dielectric materials focuses on the search for materials in which the components possess an inherently large nonlinear dielectric response. In contrast, based on thermodynamics, we have presented a first-principles approach to obtain the electrostriction-induced effective third-order nonlinear susceptibility for electrorheological (ER) fluids in which the components have inherent linear, rather than nonlinear, responses. In detail, this kind of nonlinear susceptibility is in general of about the same order of magnitude as the compressibility of the linear ER fluid at constant pressure. Moreover, our approach has been demonstrated to be in excellent agreement with a different statistical method. Thus, such linear ER fluids can serve as a new nonlinear dielectric material.
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Affiliation(s)
- J P Huang
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
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181
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Kaneko T, Yamaoka K, Osada Y, Gong JP. Thermoresponsive Shrinkage Triggered by Mesophase Transition in Liquid Crystalline Physical Hydrogels. Macromolecules 2004. [DOI: 10.1021/ma049096y] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tatsuo Kaneko
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, North 10, West 8, Kita-ku, Sapporo 060-0810, Japan, and Presto, JST
| | - Kanji Yamaoka
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, North 10, West 8, Kita-ku, Sapporo 060-0810, Japan, and Presto, JST
| | - Yoshihito Osada
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, North 10, West 8, Kita-ku, Sapporo 060-0810, Japan, and Presto, JST
| | - Jian Ping Gong
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, North 10, West 8, Kita-ku, Sapporo 060-0810, Japan, and Presto, JST
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182
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Palffy-Muhoray P, Meyer RB. Bridging the experiment-theory gap. NATURE MATERIALS 2004; 3:139-140. [PMID: 14991011 DOI: 10.1038/nmat1083] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
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183
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Watanabe M, Hirai T. Space charge distribution in bending-electrostrictive polyurethane films doped with salts. ACTA ACUST UNITED AC 2004. [DOI: 10.1002/polb.10728] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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184
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Sumana G, Raina K. Influence of polymer viscosity on the morphological and opto-electronic behavior of polysiloxane dispersed ferroelectric liquid crystal composite thin films. J Appl Polym Sci 2004. [DOI: 10.1002/app.20835] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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185
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Urayama K, Okuno Y, Kohjiya S. Volume Transition of Liquid Crystalline Gels in Isotropic Solvents. Macromolecules 2003. [DOI: 10.1021/ma034574a] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Kenji Urayama
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011, Japan
| | - Yuko Okuno
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011, Japan
| | - Shinzo Kohjiya
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan, and Institute for Chemical Research, Kyoto University, Uji, Kyoto-fu 611-0011, Japan
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186
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Zhang QM, Li H, Poh M, Xia F, Cheng ZY, Xu H, Huang C. An all-organic composite actuator material with a high dielectric constant. Nature 2002; 419:284-7. [PMID: 12239563 DOI: 10.1038/nature01021] [Citation(s) in RCA: 334] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Electroactive polymers (EAPs) can behave as actuators, changing their shape in response to electrical stimulation. EAPs that are controlled by external electric fields--referred to here as field-type EAPs--include ferroelectric polymers, electrostrictive polymers, dielectric elastomers and liquid crystal polymers. Field-type EAPs can exhibit fast response speeds, low hysteresis and strain levels far above those of traditional piezoelectric materials, with elastic energy densities even higher than those of piezoceramics. However, these polymers also require a high field (>70 V micro m(-1)) to generate such high elastic energy densities (>0.1 J cm(-3); refs 4, 5, 9, 10). Here we report a new class of all-organic field-type EAP composites, which can exhibit high elastic energy densities induced by an electric field of only 13 V micro m(-1). The composites are fabricated from an organic filler material possessing very high dielectric constant dispersed in an electrostrictive polymer matrix. The composites can exhibit high net dielectric constants while retaining the flexibility of the matrix. These all-organic actuators could find applications as artificial muscles, 'smart skins' for drag reduction, and in microfluidic systems for drug delivery.
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Affiliation(s)
- Q M Zhang
- Materials Research Institute and Electrical Engineering Department, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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187
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Kihara H, Miura T, Kishi R. Morphological studies of LC polymer networks prepared by photopolymerization of (LC monomer/LC) blends. POLYMER 2002. [DOI: 10.1016/s0032-3861(02)00292-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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188
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Stannarius R, Köhler R, Dietrich U, Lösche M, Tolksdorf C, Zentel R. Structure and elastic properties of smectic liquid crystalline elastomer films. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 65:041707. [PMID: 12005846 DOI: 10.1103/physreve.65.041707] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2001] [Indexed: 05/23/2023]
Abstract
Mechanical measurements, x-ray investigations, and optical microscopy are employed to characterize the interplay of chemical composition, network topology, and elastic response of smectic liquid crystalline elastomers (LCEs) in various mesophases. Macroscopically ordered elastomer films of submicrometer thicknesses were prepared by cross linking freely suspended smectic polymer films. The cross-linked material preserves the mesomorphism and phase transitions of the precursor polymer. The elastic response of the smectic LCE is entropic, and the corresponding elastic moduli are of the order of MPa. In the tilted ferroelectric smectic-C* phase, the network structure plays an important role. Due to the coupling of elastic network deformations to the orientation of the mesogenic groups in interlayer cross-linked materials (mesogenic cross-linker units), the stress-strain characteristics is found to differ qualitatively from that in the other phases.
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Affiliation(s)
- R Stannarius
- Institut für Experimentalphysik I, Universität Leipzig, Linnéstrasse 5, D-04103 Leipzig, Germany
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