WO2009132649A1 - Transducteur à eap comportant un corps poreux susceptible d'être étiré de manière anisotrope - Google Patents

Transducteur à eap comportant un corps poreux susceptible d'être étiré de manière anisotrope Download PDF

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Publication number
WO2009132649A1
WO2009132649A1 PCT/DK2009/000096 DK2009000096W WO2009132649A1 WO 2009132649 A1 WO2009132649 A1 WO 2009132649A1 DK 2009000096 W DK2009000096 W DK 2009000096W WO 2009132649 A1 WO2009132649 A1 WO 2009132649A1
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WO
WIPO (PCT)
Prior art keywords
anisotropic
transducer
layer
transducer according
film
Prior art date
Application number
PCT/DK2009/000096
Other languages
English (en)
Inventor
Michael Tryson
Mohamed Benslimane
Hans-Erik Kiil
Mike Zumbrum
Original Assignee
Danfoss A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Danfoss A/S filed Critical Danfoss A/S
Publication of WO2009132649A1 publication Critical patent/WO2009132649A1/fr

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Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/87—Electrodes or interconnections, e.g. leads or terminals
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • H10N30/206—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators using only longitudinal or thickness displacement, e.g. d33 or d31 type devices

Definitions

  • the invention relates to an elastomer transducer for converting between- mechanical and electrical energies.
  • the invention relates to a transducer comprising a film of an elastomer material arranged between first and second electrically conductive layers and being elastically deflectable in response to repulsion or attraction of the layers.
  • the invention further relates to a composite material for such a transducer and to a method of manufacturing such a composite material.
  • An electrical potential difference between two electrodes located on opposite surfaces of an elastomer body may generate an electric field leading to a force of attraction and thus a deflection of the elastomer body under influence of Coulomb forces between the electrodes.
  • Such transducers are referred to as electroactive polymer transducers (EAP-transducers), or artificial muscles.
  • US 6,376,971 discloses a compliant electrode which is positioned in contact with a polymer in such a way, that when applying a potential difference across the electrodes, the electric field arising between the electrodes contracts the electrodes against each other, thereby deflecting the polymer. Since the electrodes are of a substantially rigid material, they must be made textured in order to make them compliant.
  • US 6,376,971 discloses a planar compliant electrode being structured and providing one-directional compliance, where metal traces are patterned in parallel lines over a charge distribution layer, both of which cover an active area of a polymer.
  • the metal traces and charge distribution layer are applied to opposite surfaces of the polymer.
  • the charge distribution layer facilitates distribution of charge between metal traces and is compliant.
  • the structured electrode allows deflection in a compliant direction perpendicular to the parallel metal traces.
  • the charge distribution layer has a conductance greater than the electroactive polymer but less than the metal traces.
  • EAP transducers are described e.g. in US 2004/0012301 in which a waved section is provided in a body of an elastomer material.
  • the waved shape provides compliance of the transducer in a specific direction.
  • the invention provides a transducer with an anisotropic body formed of a material with a porous structure forming voids whereby the material becomes deformable and the body becomes stretchable in an anisotropic manner.
  • stretchable in an anisotropic manner it is meant that the body has stretching properties that differ according to the direction of measurement. As an example, it may not be possible to stretch the body in one specific direction or it may at least be very difficult to stretch the body in one specific direction relative to other directions.
  • the ability of the body material to deform in specific directions may concentrate the deformation of the film of elastomer material into one or more specific directions. This may improve the performance of the transducer.
  • the film may be fixed to the anisotropic body e.g. adhesively and e.g. by embedding at least a part of the film in the void space of the anisotropic body.
  • the body may comprise a polymer material, e.g. a PTFE material.
  • voids is herein defined as a free space within a body of a material.
  • the free space is formed so that the body becomes porous with empty "bobble- like" spaces in a structure e.g. of a polymeric material.
  • the voids may constitute e.g. between 20 and 80 pet of the volume of the body, and the film could e.g. fill up at least 5 pet or possibly in a range between 10-80 pet of that empty space.
  • the porous structure may e.g. be a polymer structure, e.g. as described in US 6,673,455.
  • Each electrically conductive layer may comprise a layer of a conductive material, e.g. a layer applied to a surface of the anisotropic body.
  • a conductive polymer e.g. such as a polyaniline-based conductive polymer coating could be used, or a layer of a conductive metal could be applied e.g. in an evaporation process.
  • the conductive portion could comprise a metal selected from a group consisting of silver, gold and nickel.
  • the conductive layers may have a thickness in the range of 0.01-0.1 ⁇ m, and the anisotropic body may have a similar thickness.
  • the film may have a thickness between 10 ⁇ m and 200 ⁇ m, such as between 20 ⁇ m and 150 ⁇ m, such as between 30 ⁇ m and 100 ⁇ m, such as between 40 ⁇ m and 80 ⁇ m.
  • Each electrically conductive layer may have a resistivity which is less than 10 "4 ⁇ cm. By providing the conductive layers with a low resistivity, the response time for conversion between mechanical and electrical energy can be maintained at an acceptable level.
  • the elastomer of the film may e.g. have a resistivity which is larger than 10 10
  • the resistivity of the elastomer material is much higher than the resistivity of the conductive layers, preferably at least 10 14 -10 18 times higher.
  • the resistivity of the elastomer may also be higher than that of the anisotropic body.
  • the elastomer may e.g. comprise a material selected from a group consisting of block copolymers and block-selective oligomers.
  • the anisotropic body may comprise a plurality of individual fibers in a woven or a non-woven pattern.
  • the individual fibers may be connected to each other, or they may be unconnected.
  • fibrils describe the bridges between nodes in a porous structure.
  • the compliance may be provided either by the ability of the material to deform into the voids of the porous structure, or by the ability of the fibrils to reorient relative to each other.
  • the fibrils may be allowed to rotate around the nodes.
  • a controlled orientation of the fibrils may provide the anisotropy of the body.
  • the anisotropy may be provided by having a larger fraction of the fibrils being oriented in one common direction, where this direction then becomes less compliant to stretching than other directions.
  • the fibrils may be arranged so that a sum of the lengths of fibrils which extend in one direction is larger than the sum of the lengths of fibrils which extend in other directions.
  • a first group of fibrils are oriented in a first direction
  • a second group of fibrils are oriented in a second direction being non- perpendicular to the first direction.
  • the fibrils overlap each other and compliance and anisotropy is facilitated by allowing one of the groups of fibrils to reorient relative to the other group of fibrils thereby changing the angle between the two groups of fibrils in a direction away from perpendicular.
  • the anisotropy can be also provided by different structures not only of the fibrils but also of the nodes in which the fibrils are joined.
  • the film may substantially encapsulate at least a part, and possibly the entire anisotropic body so that the body becomes located completely within the film, or the film may at least extend from one side of the body, through the body and into the opposite side of the body.
  • the two opposite outer surfaces of the composite material may thus both be formed by the film.
  • a large part of the void space between the fibrils may be filled out by the elastomer material of the film.
  • the transducer may comprise an additional anisotropic body formed similar to the already mentioned anisotropic body.
  • the film could then be arranged between the two anisotropic bodies.
  • the electrically conductive layers may form part of different anisotropic bodies or they may be attached to different anisotropic bodies, e.g. by filling out a part of the voids in those bodies.
  • At least one of the electrically conductive layers may penetrate partly into one of the anisotropic bodies without extending all the way through thickness of the anisotropic body. In one embodiment, one of the conductive layers completely penetrate one of the anisotropic bodies but leaves a certain amount of the void space free so that the film can penetrate into this remaining void space.
  • the elastomer material for the film mentioned throughout this text may e.g. be a silicone material such as a weak adhesive silicone.
  • a suitable elastomer is Elastosil RT 625, manufactured by Wacker-Chemie.
  • Elastosil RT 622 or Elastosil RT 601 also manufactured by Wacker-Chemie may be used.
  • other kinds of polymers may be chosen.
  • the anisotropic body itself is made from an electrically conductive material whereby the anisotropic body itself may form at least a part of one of the electrically conductive layers.
  • At least one of the layers of the transducer may be a plane layer, i.e. relatively flat. In an alternative embodiment, the layers could be tubular.
  • the invention provides a composite material e.g. for a transducer.
  • the composite material comprises a first layer and a second layer, the first layer comprising at least an electrically conductive portion and an anisotropic body formed of a material with a porous structure forming voids whereby the material becomes deformable and the body becomes stretchable in an anisotropic manner.
  • the second layer may comprise an elastomer material which is at least partly embedded in the void space.
  • the composite may have the structure and any of the features mentioned already with respect to the first aspect of the invention.
  • the invention provides a method of making a composite material for an EAP transducer, the method comprising:
  • the anisotropic body is made from a PTFE porous membrane, e.g. an expanded and porous PTFE membrane which forms a backing layer for support of a conductive layer which is applied on one surface of the membrane, and which forms a backing layer for support of the film which is applied to the opposite surface, e.g. in the form of a liquid silicone material which is partly cured or solidified on the surface.
  • a PTFE porous membrane e.g. an expanded and porous PTFE membrane which forms a backing layer for support of a conductive layer which is applied on one surface of the membrane, and which forms a backing layer for support of the film which is applied to the opposite surface, e.g. in the form of a liquid silicone material which is partly cured or solidified on the surface.
  • Fig. 1 illustrates a transducer according to the invention
  • Fig. 2 illustrates a porous structure forming fibrils which are connected in nodes
  • Fig. 3 illustrates an alternative embodiment of a transducer according to the invention
  • Fig. 4 illustrates a composite material for a transducer
  • Fig. 5 illustrates two layers of a composite material arranged in a stack.
  • Fig. 1 illustrates a transducer 1 for converting between electrical energy and mechanical energy.
  • the transducer comprises a body 2, a film 3, and an additional body 4.
  • the bodies 2 and 4 comprise electrically conductive portions and thereby form electrically conductive layers on opposite sides of the film 3.
  • the bodies 2 and 4 each has a structure which renders the layer compliant to stretch in a first direction and less compliant to stretch in a perpendicular direction.
  • the film 3 comprises an elastomer material which is at least partly embedded in the void space in at least one of the first and third layers.
  • the structure of the bodies 2, 4 includes a void space.
  • the void space forms a porous structure with "bobble-like" free spaces within a "sponge-like" or micro-porous structure. Since the voids or bubbles are elongated in one direction, c.f. the void 5 illustrated in cross-section compared to the void 6 illustrated in a perpendicular cross-section, the bodies 2, 4 become more easily stretchable in one direction than in another direction.
  • the film 3 extends into at least a few of those pores which are along the interface between the film and the bodies.
  • Fig. 2 illustrates an embodiment where the porosity forms relatively large voids and where the material of the body therefore forms nodes interconnected by fibrils.
  • Fig. 3 illustrates a transducer for converting between electrical energy and mechanical energy, the transducer comprising a film 7 of an elastomer material arranged between first and second layers 8, 9 of an electrically conductive material and being elastically deflectable in response to repulsion or attraction of the layers.
  • the transducer comprises an anisotropic body 10 formed of a material comprising fibers which are arranged in a predetermined woven or non- woven pattern whereby the material becomes deformable and the body becomes stretchable in an anisotropic manner.
  • the body is arranged inside the film 7.
  • Fig. 4 illustrates a composite material comprising a first layer 11 and a second layer 12, the first layer 11 comprising at least an electrically conductive portion forming an electrode, (not shown) and an anisotropic body formed of a material comprising fibers which are arranged in a predetermined woven or non-woven pattern whereby the material becomes deformable and the body becomes stretchable in an anisotropic manner.
  • the second layer is a film of an elastomer material which is easily deformable relative to the first layer.
  • the first layer is arranged inside the second layer.
  • Fig. 5 illustrates that two or more layers of the composite material illustrated in Fig. 4 may be arranged in a stack so that layers of the film comes between electrodes whereby the film can be deformed when an electrical field is applied between two adjacent electrodes.
  • the stack could e.g. be rolled to form a cylindrical transducer with the film between electrodes.

Abstract

L'invention concerne un transducteur en élastomère destiné à effectuer des conversions entre de l'énergie électrique et de l'énergie mécanique. Le transducteur comprend un matériau composite doté d'un corps et d'un film (3), le corps comprenant au moins une partie conduisant l'électricité et un corps anisotrope (2). Dans ledit corps anisotrope, des vides (5, 6) engendrent une moindre résistance à la flexion et une souplesse anisotrope en vue de l'étirement dans une première direction. Le film comprend un matériau élastomère qui peut être au moins partiellement noyé dans les vides.
PCT/DK2009/000096 2008-04-30 2009-04-30 Transducteur à eap comportant un corps poreux susceptible d'être étiré de manière anisotrope WO2009132649A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DKPA200800624 2008-04-30
DKPA200800624 2008-04-30

Publications (1)

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WO2009132649A1 true WO2009132649A1 (fr) 2009-11-05

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101840991A (zh) * 2010-04-30 2010-09-22 清华大学 电致动结构及电致动元件

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3962153A (en) * 1970-05-21 1976-06-08 W. L. Gore & Associates, Inc. Very highly stretched polytetrafluoroethylene and process therefor
US5358780A (en) * 1992-04-01 1994-10-25 Hoechst Celanese Corp. Breathable water-resistant fabrics
US5977685A (en) * 1996-02-15 1999-11-02 Nitta Corporation Polyurethane elastomer actuator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3962153A (en) * 1970-05-21 1976-06-08 W. L. Gore & Associates, Inc. Very highly stretched polytetrafluoroethylene and process therefor
US5358780A (en) * 1992-04-01 1994-10-25 Hoechst Celanese Corp. Breathable water-resistant fabrics
US5977685A (en) * 1996-02-15 1999-11-02 Nitta Corporation Polyurethane elastomer actuator

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BROOK M G: "RECENT DEVELOPMENTS IN ELECTRO-ACTIVE POLYMERA", PLASTICS AND RUBBER PROCESSING AND APPLICATIONS, APPLIED SCIENCE PUBLISHERS, LONDON, GB, vol. 8, no. 4, 1 January 1987 (1987-01-01), pages 235 - 238, XP009052870, ISSN: 0144-6045 *
JINFENG HUANG ET AL: "Piezoelectrets from laminated sandwiches of porous polytetrafluoroethylene films and nonporous fluoroethylenepropylene films", JOURNAL OF APPLIED PHYSICS AIP USA, vol. 103, no. 8, 15 April 2008 (2008-04-15), pages 084111 - 1, XP002535022, ISSN: 0021-8979 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101840991A (zh) * 2010-04-30 2010-09-22 清华大学 电致动结构及电致动元件

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