WO1999015281A9

WO1999015281A9 - Multilayer magnetostrictive transducer and magnetostrictive composite material for same

Info

Publication number: WO1999015281A9
Application number: PCT/US1998/019442
Authority: WO
Inventors: Alan E Di Crawford; Gerard N Weisensel
Original assignee: Etrema Products Inc; Gerard N Weisensel
Priority date: 1997-09-19
Filing date: 1998-09-16
Publication date: 1999-06-10
Also published as: AU9570398A; WO1999015281A2; WO1999015281A3; WO1999015281A8

Abstract

A multilayer magnetorestrictive transducer (29) comprising a first layer (32) made at least partially of a magnetic material and a second layer (37) made at least partially of a magnetorestrictive material disposed on the first layer (32). The first layer (32) magnetically biases the magnetorestrictive material of the second layer (37). The transducer (29) includes a magnetic field generator (41) for producing a magnetic field that extends through at least a portion of the second layer (37) to change the shape of the second layer (37) and thus exert a force on the first layer (32).

Claims

MULTILAYER MAGNETOSTRICTIVE TRANSDUCER AND MAGNETOSTRICTIVE COMPOSITE MATERIAL FOR SAME

This invention pertains to transducers using active materials and, more particularly, to transducers using rare earth-iron magnetostrictive materials.

Multilayer transducers have heretofore been provided using piezoelectric materials. Such piezoelectric materials however suffer from a number of disadvantages. There is therefore a need for an improved multilayer transducer which overcomes these disadvantages.

In general, it is an object of the present invention to provide a multilayer transducer which utilizes a magnetostrictive material.

Another object of the invention is to provide a multilayer transducer of the above character having an integral magnetic layer for biasing the magnetostrictive material. Another object of the invention is to provide a multilayer transducer of the above character having a layer of magnetostrictive material which elongates in the presence of a magnetic field and a layer of a magnetic material which shortens in die presence of a magnetic field.

Another object of the invention is to provide a multilayer transducer of the above character which can be used for sensing and/or actuation. Another object of the invention is to provide a multilayer transducer of the above character which utilizes a magnetostrictive composite material having high-performance thermoplastic resins such as LaRC™-SI or PETI-5 as a binder for magnetostrictive particles.

Another object of the invention is to provide a multilayer transducer of the above character in which a drive coil is embedded in a composite material of the multilayer transducer. Additional objects and features of the invention will appear from the following description from which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.

FIG. 1 is an isometric view of a multilayer magnetostrictive transducer of the present invention.

FIG. 2 is a side view of the multilayer magnetostrictive transducer of FIG. 1 mounted in a cantilever position and surrounded by an energizable solenoid coil. FIG. 3 is a side view of the multilayer magnetostrictive transducer of FIG. 1 mounted in a cantilever position near an energizable pancake coil.

FIG. 4 is a side view of the multilayer magnetostrictive transducer of FIG. 1 mounted in a cantilever position and movable between first and second positions.

FIG. 5 is a side view of the multilayer magnetostrictive transducer of FIG. 1 supported at each end and movable between first and second positions.

FIG. 6 is a side view of the multilayer magnetostrictive transducer of FIG. 1 clamped at each end and movable between first and second positions.

FIG. 7 is an isometric view of another embodiment of a multilayer magnetostrictive transducer of the present invention. FIG. 8 is an isometric view of a further embodiment of a multilayer magnetostrictive transducer of the present invention. FIG. 9 is a cross-sectional view of yet another embodiment of a multilayer magnetostrictive transducer of the present invention.

FIG. 10 is a top plan view of the multilayer magnetostrictive transducer of FIG. 9 taken along the line 10-10 of FIG. 9. FIG. 11 is an isometric view of a multilayer magnetostrictive transducer of the present invention embedded in a panel. FIG. 12 is a schematic view of a long stroke actuator incorporating the multilayer magnetostrictive transducer of the present invention. -2-

FIG. 13 is a schematic view of a stepper motor incorporating the multilayer magnetostrictive transducer of the present invention.

FIG. 14 is a schematic view of a fluid changeover valve incorporating the multilayer magnetostrictive transducer of the present invention. FIG. 15 is a schematic view of a fuel injector incorporating the multilayer magnetostrictive transducer of the present invention.

FIG. 16 is a schematic view of a fiber optic changeover switch incorporating the multilayer magnetostrictive transducer of the present invention.

FIG. 17 is a schematic view of a fiber optic chopper incorporating the multilayer magnetostrictive transducer of the present invention. FIG. 18 is a schematic view of a fluid pump incorporating the multilayer magnetostrictive transducer of the present invention.

FIG. 19 is a schematic view of another embodiment of a fluid pump incorporating the multilayer magnetostrictive transducer of the present invention.

FIG. 20 is a cross-sectional view of an actuator incorporating the magnetostrictive composite material of the present invention.

FIG. 21 is an isometric view of another embodiment of a multilayer magnetostrictive transducer of the present invention. In general, a multilayer magnetostrictive transducer comprising a first layer made at least partially of a magnetic material and a second layer made at least partially of a magnetostrictive material disposed on the first layer is provided. The first layer magnetically biases the magnetostrictive material of the second layer. The transducer includes means for producing a magnetic field which extends through at least a portion of the second layer to change the shape of the second layer and thus exert a force on the first layer. More in particular, the multilayer magnetostrictive transducer of the present invention is a thin structure which can have any shape, including the shape of a plate, a disk or a strip. The multilayer transducer is preferably planar, but can alternatively be other than planar. The transducer can be either flexible or rigid. The thin transducers described herein are variously known as unimorphs, bimorphs and multi-morphs. Multilayer magnetostrictive transducer 29 shown in FIG. 1 is strip-like in configuration and is formed from a strip 31 having first and second spaced-apart end portions 31a and 31b. The strip 31 has a first layer 32 which can optionally serve as a substrate. First layer 32 can be made from any suitable material and is preferably made at least partially of a magnetic material. First layer or metal substrate 32 can be a strip, sheet or foil of permanent magnetic material such as cobalt steel or a magnetic ferrite composition. The first layer 32 can also be a thin film produced by any suitable vacuum deposition method or can be a composite material. Metal substrate 32 has first and second opposite planar surfaces 33 and 34.

A second layer 37 made at least partially of a magnetostrictive material is disposed on first surface 33 of the metal substrate 32. Second layer 37 can be a rectangular strip of material exhibiting magnetostrictive properties and, as such, is changeable between a first or shortened shape when in the absence of a magnetic field and a second or elongated shape when in the presence of a magnetic field. More generally, the second layer 37 is made from any suitable active or smart material which changes shape when energized by being placed in a magnetic field. The suitable active materials for second layer 37 include nickel but preferably comprise a giant magnetostrictive material because giant magnetostrictive materials can tolerate high mechanical stress so as to have a relatively high energy density. High energy density enables more mechanical power output from a given electrical power input and volume of smart material which thus reduces the size and weight of second layer 37. Preferred giant magnetostrictive materials are rare earth materials, rare earth-transition metal materials and compositions having rare earth materials, transition metals and other elements.

Preferred rare earth materials for operating temperatures ranging from 0° to 200° K are rare earth binary alloys such as TbJDy,.,, where x ranges from 0 to 1. Other rare earth elements can be added or substituted for either terbium or dysprosium in this base alloy. For example, holmium, erbium or gadolinium can be used in place of either terbium or dysprosium. Other preferred rare earth materials for operating temperatures ranging from 0° to 200° K are body centered cubic intermetallic compounds such as

where x ranges from 0 to 1 , y ranges from 0 to 1 and x + y = 1. Other rare earth elements, such -3 - as holmium, erbium or gadolinium, can be added or substituted for either terbium or dysprosium in these body centered cubic lntermetallic compounds.

Preferred rare earth-transition metal mateπals are rare earth-iron mateπals such as TERFENOL based alloys. These alloys are suited for operating temperatures ranging from 0° to 700° K. One of these alloys is TbFe.. Particularly preferred rare earth-iron materials for operating in the 0° to 700° K operating range are disclosed in U.S. Patent Nos. 4,308,474; 4,609,402; 4,770,704; 4,849,034 or 4,818,304, the entire contents of which are incorporated herein by this reference, and include the material known as TERFENOL-D sold by ETREMA Products, Inc. of Ames, Iowa. TERFENOL-D is a metal alloy formed from the elements terbium, dysprosium and iron and has the formula of Tb Dy, .Fe.^, where x ranges from 0 to 1 and w ranges from 0 to 1. A preferred formula for TERFENOL-D is TbTJy, ,Fe, _n , „, where x ranges from 0.25 to 1.0. The particularly preferred formula for the TERFENOL-D material of second layer 37 is Tb _jDy ,Fe, „. Other rare earth mateπals, such as lanthanum, cerium, praseodymium, neodymium, samaπum, gadolinium, holmium, erbium or yttrium, can be added or substituted for terbium or dysprosium for property enhancement purposes For example, a giant magnetostπctive mateπal having the rare earth materials R'_xl, R² _C, R',₃ ... R",. can be provided where R', R², R³ . R" constitute rare earth mateπals and xl + x2 + x3 ... + xn = 1. Other transition metals, such as manganese, cobalt or nickel, can be added or substituted for iron as disclosed m U S. Patent No 5,110,376, the entire contents of which are incorporated herein by this reference Elements which are not transition metals, such as aluminum or silicon, can also be added or substituted for iron For example, a giant magnetostπctive mateπal having the elements T'_y„ T²^, T³^ .. T can be provided where T\ T\ T⁵ ...T constitute transition metals or elements such as aluminum or silicon and yl + y2 + y3 ... + yn = 2-w. Alternatively, an lntermetallic compound can be provided having combinations or variations of TERFENOL-D, such as (Tb_xl,Dy_l2,R³ _iϋ,R ₁< ... R"J(Fe_yl,T^a _r-,T^J._} ... T_y„)_2^ where xl + x2 + x3 ... + xn = 1 , yl + y2 + y3 .. + yn = 2-w, and w ranges from 0 to 1.

Giant magnetostπctive mateπals which shorten and thus exhibit negative magnetostπction when placed in a magnetic field can be used for the mateπal of second layer 37 and be within the scope of the present invenϋon. These negative magnetostrictive materials have formulations similar to the giant magnetostπctive mateπals descnbed above except that they include die rare earth element samanum Preferred negative magnetostπctive materials for operating temperatures ranging from 0° to 700° are SAMFENOL based alloys such as SmFe- A particularly preferred SAMFENOL based alloy is SAMFENOL-D, which is also disclosed ui U S Patent Nos. 4,308,474, ₄,609,402, 4,770,704, 4,849,034 or 4,818,304 and has the formula Sm_xDy, .Fe^, where x ranges from 0 to 1 and w ranges from 0 to 1 Other rare earth mateπals, such as lanthanum, ceπum, praseodymium, neodymium, gadolinium, holmium, erbium or yttπum, can be added or substituted for samaπum or dysprosium in the same manner as discussed above with respect to TERFENOL based alloys In addition, other transition metals, such as manganese, cobalt or nickel, and elements which are not transition metals, such as aluminum and silicon, can be added or substituted for iron in the same manner as also discussed above

Specifically, second layer 37 is formed entirely of a magnetostπctive mateπal In one embodiment, the layer 37 can be preformed and secured to metal substrate 32 by any suitable means such as an adhesive Alternatively, second layer 37 can be deposited in the form of a thin layer onto metal substrate 32 by any suitable vacuum deposition method such as electronic sputtering or evaporation During the sputteπng process, the permanent magnetic field from metal substrate 32 may assist in the crystal domain alignment of the deposited magnetostrictive material.

As a further alternative, the magnetostπctive material of second layer 37 can be part of a dispersion bound together by a matrix mateπal such as a polymer or other suitable resin. Such a dispersion or magnetostπctive composite mateπal can be consolidated by heating or polymeπzation When feasible, such a dispersion layer 37 can be cut or rolled in the form of a thin sheet and secured to metal substrate 32 by any suitable means such as an adhesive. The shape of second layer 37 when viewed in plan need not follow the outline of the metal substrate 32. For example, the configuration of the second layer 37 can be determined by masking when the second layer is formed by a vacuum deposition process. As another example, a magnetostπctive powder dispersed in a suitable binder can be brushed onto the metal substrate in a manner similar to an ink or paint. -4-

The thicknesses of the multilayer transducers herein and the layers thereof are dependent on several factors, including the intended application and whether the transducer is to be mounted to another structure or used as a stand-alone element. When the transducer is to be used as a stand-alone element, the first layer 32 can serve as a rigid support for the magnetostrictive second layer 37. Specifically, the multilayer transducers can have thicknesses on the order of millimeters or less. Multilayer transducer 29 includes means for producing an electromagnetic field which extends through at least a portion of second layer 37. Such means or magnetic field generator 41 can be of any suitable type and is disposed in close proximity to the second layer 37. For example, a conventional coil made from any suitable electrically conductive material such as fine magnet wire of copper, aluminum, niobium titanium or silver can be utilized for producing the magnetic field to drive second layer 37. Drive coil 42 shown in FIG. 2 is tubular in conformation and is concentrically disposed about transducer 29. Drive or solenoid coil 42 is formed from electrically conductive wire (not shown) wound into the shape of the coil 42. A conventional controller and power supply 43 provides the drive signal to energize coil 42 and is electrically coupled to the coil 42. The magnetic field generator 41 has a form suited to the application and can alternatively be a planar or flat coil 46 of the type shown in FIG.

3. The flat or pancake coil 46 is also made of an electrically conductive material. Pancake coil 46 is disposed adjacent strip 31 and is preferably disposed adjacent second layer 37 of the strip 31. Although the pancake coil 46 is shown in a spaced-apart position from the strip 31, it should be appreciated that the pancake coil can be mounted in juxtaposition to the strip 31. Pancake coil 46 is coupled to controller and power supply 43.

Metal substrate 32 is included within the magnetic means of transducer 29 for continuously biasing second layer 37. Specifically, the metal substrate 32 is sized to produce a uniform DC magnetic field through the second layer 37.

Strip 31 of multilayer transducer 29 can be disposed in a variety of configurations for operation. Strip 31 is shown in FIGS. 2-4 as being mounted in a cantilever position from a support 51. Specifically, first end portion 3 la of the strip 31 is clamped within support 51 so that second end portion 31b of the strip 31 is free to move upwardly and downwardly relative to the support 51. The strip 31 has a first or home or bowed position, shown by a phantom line and identified by reference number 31 ' in FIG.

4, when in an unenergized state. When energized by magnetic field generator 41, the strip 31 moves to a second or planar position, shown in solid lines and identified by reference numeral 31 in FIG. 4, and thereafter to a third or fully deflected position, shown by a phantom line and identified reference numeral 31 " in FIG. 4. As can be appreciated, the energization of second layer 37 causes layer 37 to elongate and thus exert a bending moment on metal substrate 32 which first moves the substrate to its linear position and thereafter moves the substrate to its fully deflected position, which is symmetrically opposite the first or home position when viewed relative to the second or planar position. Second end portion 31b can thus be moved upwardly and downwardly between two extreme or bowed positions by controller and power supply 43 and magnetic field generator 41. The electric drive signal from controller 43 is usually time varying and can be an alternating current. For a desired frequency of operation of the magnetostrictive layer 37, the electric drive frequency can be at half that frequency because energizing at each half cycle will produce a full cycle of strain. This reduces the effective power. Such frequency doubling effect can be prevented by magnetically biasing the second layer 37. Generally, for best operation the biasing flux density will be approximately 60% of the saturation value. In another method of operation, strip 31 can be end supported on first and second spaced-apart pedestals 52 (see FIG.

5). Specifically, first and second end portions 31a and 31b are each placed on a pedestal 52. Such nodal support of end portions 31a and 31b permits the strip 31 to pivot about the respective pedestal 52. When energized by magnetic field generator 41, strip 31 moves from a first or home or bowed position, shown by a single phantom line and identified by reference numeral 31' in FIG. 5, to a second or planar position, shown in solid lines and identified by reference numeral 31 in FIG. 5, and then to a third or fully deflected position, shown by a single phantom line and identified by reference numeral 31 " in FIG. 5. Second position

31" is symmetrically opposite first or home position 31' when viewed relative to the second or planar position of strip 31 in FIG. 5. -5-

In a third method for operating strip 31, first and second end portions 31a and 31b are end clamped to respective first and second supports 53 and 54, each substantially similar to support 51 (see FIG. 6). Strip 31 extends between the supports 53 and 54. When the strip 31 is energized by magnetic field generator 41, the strip performs similar to the strip 31 shown in FIG.

5. Specifically, strip 31 moves from a first or home or bowed position, shown by a single phantom line and identified by reference numeral 31' in FIG. 6, to a second or planar position, shown by solid lines and identified by reference numeral 31 in FIG. 6, and then to a third or fully deflected position, shown by a single phantom line and identified by reference numeral 31" in FIG.

6. The third or fully deflected position 31" is symmetrically opposite the home position 31' relative to the intermediate or planar position of strip 31.

Strip 31 can be referred to as a flexure element when mounted as shown in FIGS. 4-6. Such flexure elements have very low resonant frequencies and large out-of-plane motion relative to in-plane motion, while still retaining a compact physical form.

It should be appreciated that strip 31 can be constructed so as to be in a planar position when in a non-energized state.

As such, the strip 31 would deflect in only a single direction from its planar position. For example, the strip 31 would have a home or planar position shown by the solid lines in FIGS . 4-6 and upon energization would move to one of the bowed positions shown by phantom lines in FIG. 4-6. The amount of such deflection from the linear position to the fully deflected or bowed position would be approximately twice the deflection shown in FIGS. 4-6 with respect to strips 31 shown therein.

The multilayer strip of the present invention can have other constructions. A strip 61 substantially similar to strip 31 is shown in FIG. 7. Like reference numerals have been used to describe like components of strips 31 and 61. Strip 61 includes a first layer or metal substrate 62 substantially similar to metal substrate 32. Metal substrate 62 is provided with first and second spaced-apart end caps or magnetic pole pieces 63 which extend upwardly from first surface 33 of the substrate 62. End caps 63 form a recess 64 therebetween into which second layer 37 is disposed. As such, second layer 37 is seated flush with the end caps 63. The magnetic pole pieces enhance the distribution of magnetic flux in second layer 37.

In a further embodiment, a strip 71 is provided having first and second spaced-apart layers which are each made at least partially of a magnetostrictive material. Strip 71 , shown in FIG. 8, is substantially similar to strip 31 and like references have been used to describe like components of the strips 31 and 71. Third layer 72 of the strip 71 is secured to second surface 34 of metal substrate 32 so that the metal substrate 32 is sandwiched between second layer 37 and third layer 62. Third layer 72 is made at least partially of a magnetostrictive material and is preferably substantially similar to second layer 37. In the preferred embodiment of strip 71, second layer 37 is preferably made from a magnetostrictive material which is changeable between a first or shortened shape when in the absence of a magnetic field and a second or elongated shape when in the presence of a magnetic field and third layer 72 is made from a magnetostrictive material changeable between a first or elongated shape when in the absence of a magnetic field and a second or shortened shape when in the presence of a magnetic field. The trilaminar construction of strip 71 utilizing a magnetostrictive material which elongates when energized and a second magnetostrictive material which shortens when energized provides for increased deflection for a given field. Specifically, the elongation of second layer 37 and the shortening of third layer 72 increases the amount which strip 71 can bend when energized by a magnetic field generator 41.

It should be appreciated that both strips 61 and 71 can be positioned for operation in the same manner that strip 31 is positioned in FIGS. 4-6. In addition, strip 71 can be constructed to bend in two opposite directions from a home position, such as the planar home position shown in solid lines in FIGS. 4-6 with respect to strip 31, when properly biased magnetically and driven by first and second magnetic field generators 41.

As stated above, the multilayer transducer 29 can have a variety of shapes. For example, multilayer transducer 81 shown in FIGS. 9-10 has a disk 82 which changes shape when in the presence of a magnetic field. Disk or bimorph 82 is constructed similar to strip 31 and has a first layer or metal substrate 83 substantially similar to metal substrate 32 and a second layer 84 substantially similar to second layer 37. In one method of operating the multilayer transducer 81, disk 82 is circumferentially clamped or restrained by a tubular support 87 having a bore 88 extending longitudinally therethrough. Disk 82 extends perpendicularly of the longitudinal axis of support 87 across bore 88. In operation, a pancake coil 46 can be placed adjacent -6- disk 82 for causing the multilayer transducer 81 to mechanically deform in an umbrella mode with the largest deflection occurring at the center of disk 82. Specifically, disk 82 deflects from a first or home planar position, shown in solid lines in FIG. 9, to a second or bowed position, shown by a single phantom line and identified by reference numeral 82' in FIG. 9.

The multilayer transducers of the present invention can be used for sensing as well as dnving. In a sensing mode for stπp 31, second layer 37 produces an electπcal signal in response to a change in shape of the second layer. As a sensor, the transducers herein can be used for structural analyses such as predicting the life of structural components via fatigue failures, stress concentration and lamination failures in composites. In one such application, a multilayer transducer 96 can be embedded into a structure such as a panel 98 of an aircraft (see FIG. 11). Transducer 96 can have any of the shapes and constructions described above and is shown in FIG. 11 as being a stπp 99 substantially similar to stπp 31. Panel 98 has an outer surface 101. A pancake coil 102 substantially similar to pancake coil 46 is loosely positioned on surface 101 adjacent stπp or bimorph 99 for serving as an energizing and pickup coil. The coil 102 is electrically coupled to controller and power supply 43.

In operation and use, vibrations of panel 98 cause the magnetostπctive mateπal in the second layer 37 of strip 99 to deform and thus produce a magnetic field which extends through part or all of pancake coil 102. An electrical signal or current with a magnitude proportional to such vibration is generated by coil 102 and transmitted to controller 43 A suitable algoπthm is included in controller 43 for analyzing the vibration signal and determining the appropπate cancellation response required by strip 99.

A responsive electπcal signal is generated by controller 43 and transmitted to coil 102. The magnetic field created about coil

102 by such signal extends through stπp 99 causing the stπp to deflect and thus cancel or reduce the vibration in the panel 98.

Additional applications for the multilayer transducers herein are shown in FIGS. 12-19 Specifically, a long stroke actuator

106 is shown in FIG. 12. Actuator 106 utilizes a multilayer transducer 107 substantially similar to transducer 29. Transducer 107 has a stπp or bimorph 108 substantially similar to stπp 31. The stπp 108 includes first and second end portions 108a and 108b. First end portion 108a is cantilever mounted to a support structure 111 in substantially the same manner as strip 31 is mounted to support 51 in FIG. 4 An energizing coil 112 substantially similar to dπve coil 42 is concentrically disposed about strip 108. Energizing coil 112 is electπcally coupled to a controller and power supply of the type described above. A drive member 113 is secured to stnp second end portion 108b and moves upwardly and downwardly in FIG 12 in response to upward and downward bending of stπp 108 relative to support structure 111 As can be appreciated, dπve member 113 can be used in a vaπety of applications to dπve or actuate other devices.

A stepper motor 116 is shown in FIG. 13 Motor 116 has a multilayer transducer 117 which is substantially similar to transducer 29 and is provided with a stπp or bimorph 118 having first and second end portions 118a and 118b. First end portion 118a of the stπp 118 is ngidly secured to a support structure 119 so that the stπp 118 is cantilevered from the support structure 119. An energizing or dπve coil 122 substantially similar to dπve coil 42 is concentπcally disposed about stπp 118 for causing second end portion 118b to pivot upwardly and downwardly relative to first end portion 118a Dπve coil 122 is electrically coupled to a controller and power supply of the type descnbed above A toothed ratchet wheel 123 is mounted to support structure 119 for rotation about a pivot pin 124 Second end portion 118b of stπp 118 engages the teeth of ratchet wheel 123 and serves as a pawl which, when energized by transducer 117, causes ratchet wheel 123 to rotate a specified amount about pivot pin 124. The selective rotation of ratchet wheel 123 can be used to drive or actuate other devices.

A fluid changeover valve 131 is shown in FIG. 14. A multilayer transducer 132 substantially similar to transducer 29 is included in changeover valve 131. Transducer 132 includes a stπp or bimorph 133 which is substantially similar to stπp 31 and has first and second end portions 133a and 133b. Transducer 132 is disposed within a chamber 136 of a vessel 137. Strip first end portion 133a is ngidly mounted to the inside wall of vessel 137 so that stπp second end portion 133b is pivotable upwardly and downwardly relative to first end portion 133b Vessel 137 is provided with a fluid mlet port 138 and first and second outlet ports 141 and 142. Stπp second end portion 133b extends between first and second linearly aligned outlet ports 141 and 142 and has first and second valve caps 143 and 144 mounted on opposite sides diereof for respective engagement with first and second outlet ports 141 and 142 A magnetic field generator in the form of a dπve coil 146 substantially similar to dπve coil 42 is -7- concentπcally mounted about strip 133. Dπve cod 146 is electncally coupled to a controller and power supply of the type described above.

In operation and use, dπve coil 146 causes stπp 133 to move between a first position in which first valve cap 143 engages first outlet port 141 so as to preclude fluid flow through the outlet port 142 and a second position in which second valve cap 144 engages second outlet port 142 so as to preclude fluid flow through the outlet port 142. Changeover valve 131 and transducer 132 thereof thus direct fluid flow from inlet port 138 through either first outlet port 141 or second outlet port 142.

A fuel injector 151 is shown in FIG. 15. Injector 151 has a multilayer transducer 152 which is substantially similar to multilayer transducer 81 and is provided with a disk or bimorph 153 substantially simtiar to disk 82. Fuel injector 151 is formed from a support structure or housing 156 having a fluid passageway 157 in communication with a valve seat 158. Disk 153 is circumferentially mounted to housing 156 in the same manner as disk 82 is mounted to tubular support 87. A valve stem 161 extends from the center of disk 153 through fluid passageway 157. Stem 161 has a valve head 162 formed at the end thereof for cooperaUve engagement with valve seat 158. An O-πng 163 or other suitable sealing means is concentrically disposed about valve stem 161 for engaging housing 156 and precluding fluid in passageway 157 from escaping to disk 153. A magnetic field generator m the form of a pancake coil 166 substantially similar to pancake coil 102 is disposed adjacent disk 153 for moving the disk 153 in first and second opposite directions from its planar position shown in solid lines in FIG 15 to respective first and second bowed or umbrella-like positions (not shown) Pancake cod 166 is electncally coupled to a controller and power supply of the type descπbed above.

In operation and use, movement of disk to its upper deflected or umbrella-like position causes stem 161 to engage valve seat 158 and preclude fluid flow through passageway 157. Movement of the disk 153 to its lower deflected or umbrella-like position fully opens the valve stem 161 thus permitting fluid from passageway 157 to flow through the valve.

A fiber optic changeover switch 171 is shown in FIG 16. Switch 171 has a multilayer transducer 172 substantially similar to transducer 29. The transducer 172 includes a stπp or bimorph 173 which is substantially similar to stπp 31 and has first and second end portions 173a and 173b. First end portion 173a of the stπp 173 is ngidly mounted to a support structure 176 in the same manner that stπp 31 is mounted to supports 51. A magnetic field generator in the form of a dπve coil 177 substantially similar to dnve coil 42 is concentπcally disposed about stπp 173 for pivoting second end portion 173b upwardly and downwardly relative to the fixed first end portion 173a Dπve coil 177 is electncally coupled to a controller and power supply of the type descπbed above. An output fiber opuc cable 181 is provided and has a severed end portion 181a mounted to second end portion 173b of the transducer 172 Fust and second output fiber optic cables 182 and 183 are mounted on support structure 176. End portion 181a of the input fiber opϋc cable 181 is movable by stnp 173 between a first or upper position in which the end portion 181a is aligned with the end of first output fiber optic cable 182 so that light transmitted by input fiber optic cable 181 is directed into first output fiber optic cable 182 and a second position in which the end portion 181a is aligned with the end of second output fiber optic cable 183 so that the hght transmitted by input cable 181 is directed into the second output cable 183.

A fiber opuc chopper 191 is shown in FIG 17 Chopper 191 includes a multUayer transducer 192 substantially similar to transducer 29. Transducer 192 has a stnp or bimorph 193 which is substantially similar to stnp 31 and has first and second end portions 193a and 193b. First end portion 193a is ngidly mounted to a support structure 196 in the same manner that stnp

31 is mounted to support 51. Second end portion 193b is pivotable upwardly and downwardly relative to the fixed first end portion 193a. A magnetic field generator in the form of a dπve coil 197 substantially similar to dπve coil is concentrically disposed about strip 193 for causing such upward and downward movement of stπp second end portion 193b. A first fiber optic cable 201 having an end portion 201a and a second fiber optic cable 202 having an end portion 202a are secured to support structure 196. End portions 201a and 202a are spaced-apart by a space 203 which is small enough to permit hght from input cable 201 to travel through the space 203 to output cable 202. An optically opaque plate 206 is mounted to second end portion 193b of stπp 193 for movement between a first position in which the plate is disposed in space 203 so as to preclude light from traveling between cables 201 and -8-

202 and a second position out of space 203 so as to permit light to travel between cables 201 and 202. Chopper 191 can thus be used to regulate the travel of light between first and second fiber optic cables 201 and 202.

A fluid pump 211 is shown in FIG. 18. Pump 211 is formed by a support structure or vessel 212 having a circular opening 213 formed in the top wall thereof which communicates with an internal chamber 214. A multilayer transducer 216 substantially similar to multilayer transducer 81 is mounted atop vessel 212. Transducer 216 has a disk or bimorph 217 which is substantially similar to disk 82 and is circumferentially mounted in a fluid-tight manner to vessel 212 so as to extend over opening 213. A magnetic field generator in the form of a pancake coil 218 substantially similar to pancake coil 102 is positioned atop multilayer transducer 216 for moving disk 217 upwardly and downwardly between first and second bowed or umbrella-like positions. Vessel 212 is further provided with an inlet port 221 and an output port 222 governed by respective input and output valves 223 and 224.

In operation and use, movement of disk 217 by pancake coil 218 to an upward or outwardly-bowed position causes input valve 223 to open and fluid to be drawn into input port 221. Movement of the disk to its lower or downwardly-bowed position causes output valve 224 to open and fluid within the chamber 214 of vessel 212 to be pumped out of output port 222.

Another embodiment of a fluid pump incorporating the multilayer transducers of the present invention is shown in FIG. 19. Fluid pump 231 shown dierein includes a substantially planar body 232 formed with an annular recess 233 in the top surface thereof. The body 232 is formed from any suitable material such as metal or ceramic. A circular-shaped diaphragm 236 made from any suitable flexible material such as metal or elastomers is mounted to the top of body 232 so as to overlie recess 233 and, as such, form a fluid-tight pumping chamber 237. Body 232 is formed with a central upstanding portion which extends up into the center of chamber 237 to engage the bottom of diaphragm 236 when the diaphragm is in its relaxed or planar home position shown in FIG. 19.

Fluid pump 231 is provided with at least first and second ports. A central or inner port 241 extends upwardly through the center of body 232 and opens at the center of portion 238. An outer port 242 spaced radially outwardly from inner port 241 extends upwardly through body 232 into the pumping chamber 237.

Fluid pump 231 includes a multilayer transducer 246 substantially similar to transducer 29. Transducer 246 has a strip or bimorph 247 which is substantially similar to strip 31 and has first and second end portions 247a and 247b. First end portion 247a is secured to body 232 by any suitable means such as an adhesive 248. Second end portion 247b of the strip is secured to the center of diaphragm 236 by any suitable means such as the adhesive 248. A magnetic field generator in the form of a pancake coil 251 substantially similar to pancake coil 102 is disposed adjacent the top of strip 247. Pancake coil 241 is electrically coupled to a controller and power supply of the type described above. The second end portion 247b of the strip 247 pivots upwardly and downwardly relative to first end portion 247a under the influence of pancake coil 251 to move the center of diaphragm 236 upwardly and downwardly.

As more fully described in the article entitled Micro Device Both Pumps and Controls published in the August 1997 issue of Eureka, the entire contents of which are incorporated herein by this reference, the operation of fluid pump 231 depends upon the pulse rate at which strip 247 moves diaphragm 236 upwardly and downwardly relative to body 232. At a slow pulse rate, the outer parts of the diaphragm lag behind the motion of the inner portion such that the diaphragm lifts clear of the inner port 241 before it lifts clear of the outer port 242 and thus sucks more fluid from the inner port 241 than from the outer port 242. On the reverse stroke, the diaphragm impacts on the inner port 241 and seals it before it closes the outer port 242. The fluid pump 231 therefore pumps from the inner port 241 to the outer port 242.

If the pump works at a fast pulse rate, the diaphragm does not have time to deform. Accordingly, during the upward suction stroke, the diaphragm is initially closer to the raised inner port 241 and more fluid is sucked from the outer port 242.

On the downward pumping stroke, more fluid passes out through the inner port 241 because it is the most accessible to the area of fluid underneath the circular diaphragm 236. The pump then pumps fluid from the outer port 242 to the inner port 241. -9-

Medicai applications for fluid pump 231 include the controlled administration of drugs. Other applications include introducing anti-odor, anti-bacterial and anti-fungal agents into air conditioning and ventilation systems.

The applications for the multilayer magnetostrictive transducers herein, which can be characterized as thin film-like transducers, are many. The major increase in sensitivity and mechanical response found with giant magnetostrictive elements enables many applications to be undertaken that require power levels not possible with similar piezoelectric devices. Under both static and resonant conditions, the very large movements allow simple actuators with long strokes to be built. As the mechanical element is entirely isolated from the electrical energizing coil, there is no danger from electric shock when the device is used in medical and surgical applications.

As an example of another application of a sensor, a bimorph can be used as an accelerometer when it is cantilever mounted and a small mass placed on the free end. As discussed above, the transducers can be used as vibration detectors and surface wave generators. In addition, the transducers can be used as record pick-ups and strain gauges. For example, the detection of stress in a structure such as a building or a bridge can be carried out by installing the transducer in a permanent position and then using a mobile search coil to determine changes in the magnetic properties of the transducer, such as permeability. The large deformations can be used to generate high amplitude shock waves for surgical use, structural testing or seismic work. The restrained disk described above is suitable for such applications and provides a robust assembly for field work. In a shock wave generator, the transducer disk can be initially edge-stressed to near a snapover level such that the additional magnetostrictive stress would trigger the movement to an instantaneous cusp form. In another application, the thin multilayer transducers described herein can be used in flat panel loudspeakers of die type described in die article entitled the Art of Noise published in the September 22, 1997 issue of Electronic Times, the entire contents of which are incorporated herein by this reference. As can be seen, the multilayer transducers of the present invention can be embedded in panels, human bodies or other inaccessible areas. Once so positioned, such a transducer can be remotely driven by a drive coil or other magnetic field generator positioned in close proximity to the transducer. Such an inaccessible transducer can be utilized as a sensor. An electrical coil or similar apparatus which generates an electrical current in response to a magnetic field experienced thereby can be used for remotely detecting deformations in the sensor. Other magnetostrictive composite materials can be used for forming second or magnetostrictive layer 37 in the multilayer transducers of the present invention. Other preferred magnetostrictive composite materials utilize advanced polyimides, such as the type developed by the NASA Langley Research Center, as a binder for the magnetostrictive particles in the magnetostrictive layer of the transducers. One of such advanced polyimides. developed for high temperature applications, is PETI-5, which is an abbreviation for phenylethynyl terminated imide oligomer. PETI-5 is a commercially available pseudo-thermosetting polyimide prepared from 3, 3', 4, 4' - biphenyltetracarboxylic dianhydride (BPDA), 3,4' - oxydianiline (ODA), and 1,3- bis (3-aminophenoxy) benzene (3-APB) with an endcapping reagent of 4-phenylethynlphthalic anhydride (PEPA). PETI-5 exhibits exceptional adhesive properties and thus provides a strong high temperature resin system for composite applications. Since PETI-5 can be solution cast, the material will readily accept paniculate fillers. Typical processing temperatures range between 310°C and 375°C with pressures as low as 25 psi. Another such advanced polymer is LaRC™-SI, which is an abbreviation for Langley Research Center - Soluble Imide.

LaRC™-SI is commercially available and synthesized using equimolar amounts of the dianhydrides 4, 4'-oxydiphthalic anhydride (ODPA) and 3, 3', 4, 4' - biphenyltetracarboxylic dianhydride (BPDA) with endcapping reagents 3, 4' - oxydianiline (ODA) and phthalic anhydride (PA) added to offset the stoichiometry of the material. Adding LaRC™-SI in weight percents ranging from 1.5 to 10, then post-processing the material, affords fully consolidated pieces capable of machining or direct use. LaRC™-SI and PETI-5 are high-performance thermoplastic resins with unique combinations of physical, mechanical and adhesive properties. Some of the attractive properties include large toughness and fracture resistance (e.g., G,,. and K_fc values of 4.6 kJ/m² and 4.4 MN/ra^!a, respectively, for LaRC™-SI). LaRC™-SI also provides high lap shear strengths when used as an adhesive. -10-

The magnetostπctive composite mateπals descπbed herem can be manufactured in any suitable manner such as injection molding processes. A desired magnetic bias can be applied to the magnetostnctive particles, for example by the metal substrate 32 or other DC magnets, to align the particles into continuous chains along die flux lines of the applied magnetic field prior to the curing of the polymer resin. Uniaxial compressive stresses due to curing automatically apply a preload and align the domains in the magnetostπctive particles to maximize response of the magnetostrictive matenal. The magnetostπctive composite materials described herein can be tailored to surpass the polycrystalline monolithic mateπal in specific properties. For example, by embedding the magnetostrictive material in a 1-3 arrangement, the hydrostatic component can be optimized.

The new magnetostπctive composite materials descπbed herein can be used in a vaπety of applications, including actuators of all types, pumps, valves, active flow control systems, vibration dampers, structural health monitoring systems, scanner motors, micro-electromechanical systems (MEMS), thin films and sensors. By taking advantage of the broad thermal capabilities of the novel constituent matenals, these products can be designed for use in temperatures ranging from cryogenics to over 200°C. Such actuators can be used in mirror and other optics positioning, deployment of structures, powering remote vehicle manipulators, locking and latching mechanisms for docking and other low frequency applications or other applications which require a position and hold capability with high stiffness Medium frequency applications include pumps, valves and both active and passive structural vibration dampers. High frequency applications include such things as instrument scanner motors and generating ultrasonic acoustic streaming for moving liquids wrthout pressure buildup and heating In connection with the foregoing, the magnetostπctive composite matenals descπbed herein can be used to create complex 3-D structures.

The new magnetostπctive composite mateπals provide a high performance smart mateπal with structural capabilities, excellent durability and high temperature capability, while overcoming the electncal connectivity problems associated with piezoceramic composites. The embedding of particles of a magnetostπctive mateπal into a polymer resin increases the fracture toughness of the mateπal. The embedding of the magnetostπctive particulate into a polymer also provides increased mechanical compliance, substantially larger hydrostatic coefficients, larger figures of ment, lower acoustic impedance and lower transverse electromechanical coupling coefficients Activating and sensing of magnetostπctive mateπals can be achieved in a non-contact manner by means of a magnetic field. Control over alignment and distπbution of the magnetostπctive particles within the polymer resin is also permitted. In addition, composites made with electncally insulating matπx mateπals eliminate eddy current losses and offer the potential for even higher frequency operation due to the small particle size Potential size and weight reduction associated with these new composites are also advantageous Production costs for making structures from these magnetostrictive composite matenals are less than the costs for making similar structures from monolithic magnetostnctive matenals. In addition, scrap mateπal can be recycled into such magnetostπctive composite mateπals The new magnetostπctive composite matenals utilizing PETI-5 or LaRC™-SI as a binder can be used in other than a thin multilayer transducer. For example, a magnetostπctive actuator 261 utilizing such magnetostnctive composite mateπals is shown in FIG. 20. Actuator 261 has an active element or dπve rod 262 made from a magnetostπctive composite material of the type descπbed above. Specifically, the dπve rod 262 is compπsed of PETI-5 or LaRC™-SI and magnetostπctive particles or powder made from any of the magnetostnctive mateπals descπbed above with respect to second layer 37 of multilayer transducer 29. The PETI-5 or LaRC™-SI serve as a binder for the magnetostπctive particles. Elongate dπve rod 262 has first and second end portions 262a and 262b and extends along a longitudinal axis 263. The drive rod 262 can be of any suitable shape and, as shown, is cylindrical in shape. More specifically, the drive rod 262 has a circular cross-section.

Dynamic magnetic field generation means is provided in actuator 261 for producing an electromagnetic field which extends through at least a portion of dπve rod 262 to change the shape of the dπve rod 262. In this regard, an elongate tubular means or coil 266 made of an electrically conductive mateπal is concentπcally disposed about dπve rod 262 and is included within the means of actuator 261 for producing a magnetic field through the entire dπve rod 262. Excitation or dπve coil 266 has first and second end portions 266a and 266b and is circular in cross section. The dπve coil 266 has a length approximating the length of dπve rod 262 and as shown is slightly longer than the length of dπve rod 262. The dπve coil 266 is made from any suitable -11- conductive material such as fine magnet wire of copper, aluminum, niobium titanium or silver for producing a magnetic field having a flux which extends through the drive rod 262. Means for providing an electrical signal to excitation coil or wire solenoid 266 includes a controller and power supply 267 substantially similar to controller and power supply 43. Controller 267 is electrically coupled to the coil 266 by means of lead means or wires. Magnetic means or tubular bias magnetic means in the form of tubular bias magnet 271 is provided in actuator 261 for continuously biasing drive rod 262. The bias magnet 271 is concentrically disposed about drive coil 266 and has a length approximating the length of drive rod 262. Specifically, bias magnet 271 has a length equal to the length of drive rod 262 and slight shorter than the length of drive coil 266. Bias magnet 271 is made from a hard magnetic material of any suitable type such as many of the different grades of neodymium iron boron. Alternatively, magnet 271 can be made from materials such as samarium cobalt or aluminum nickel cobalt. The bias magnet 271 is shaped and sized to produce a uniform DC magnetic field through drive rod 262.

First and second flux return means or elements 272 and 273 are included within actuator 261 for capturing the DC magnetic field created by bias magnet 271 and directing this DC field through drive rod 262. The first and second flux return elements also capture the AC magnetic field generated by drive coil 266 and channel this AC field into drive rod 262. The first and second flux return elements are shaped as disks and are concentrically centered on longitudinal axis 263. The elements 272 and 273 are disposed on the opposite end surfaces of drive rod 262 and tubular bias magnet 271. First and second flux return elements 272 and 273 each have an outer diameter approximately equal to the outer diameter of the bias magnet 271.

Fust and second flux return elements 272 and 273 are each made from any suitable ferromagnetic or soft magnetic material having a relatively low electrical conductivity and a relatively high electrical resistivity. The flux return elements 272 and 273 also have a relatively high magnetic saturation flux density. It is preferred that the material of elements 272 and 273 has an electrical resistivity greater than 1000 ohm-cm, although a more practical electrical resistivity range is between 0.01 to 1000 ohm-cm. It is preferable that the magnetic saturation flux density be greater than 8,000 gauss, more preferably greater than 12,000 gauss and most preferably greater than 20,000 gauss. A suitable material for elements 272 and 273 is the material marketed under the trade name High Flux by Arnold Engineering of Marengo, Illinois and by Magnetics of Butler, Pennsylvania. High Flux is a nickel and iron alloy having the composition of .5 nickel and the balance iron. The nickel and iron elements of the High Flux material are ground into micron and sub-micron particle sizes. A dielectric is sprayed on the particles to electrically insulate them and that powder mix is compressed at roughly 200 tons per square inch to make a solid component. Another suitable material is iron powder marketed by MMG-North America of Paterson, New Jersey. The iron powder has a composition of greater than 95% iron. The iron powder is produced in a manner similar to the method described above for producing High Flux. Briefly, the iron elements are ground into micron and sub-micron particle sizes. A dielectric is sprayed on the particles to electrically insulate them and that powder mix is compressed to make a solid component which is the equivalent of a sandstone structure. Each of these materials has an electrical resistivity ranging from 0.01 to 50 ohm-cm and a magnetic saturation flux density ranging from 12,000 to 15,000 gauss. High Flux has a high relative permeability which makes it a good magnetic flux conductor.

Drive rod 261, drive coil 266, bias magnet 271 and first and second flux return elements 272 and 273 are disposed in a tubular housing 276 made from steel or any other suitable material. First and second disk-shaped end caps 277 and 278 made from steel or any other suitable material are rigidly secured within the first and second open ends of the housing 276 to seal the housing. A cylindrical push rod 281 centered on longitudinal axis 263 is provided at die second end of housing 276. Push rod 281 has a disk-shaped base 281a which rests against second flux return element 273 and an elongate piston 281b which extends through a central opening provided in the second end cap 278. A bushing 282 is disposed in the opening and mounted about piston 281b for facilitating reciprocation of the piston 281b relative to the end cap 278.

In addition to the prestressing from curing of the magnetostrictive composite materials of drive rod 262, means is optionally included within actuator 261 for imparting a preload on the drive rod 262 and includes a Belleville spring 286 concentrically disposed around output piston 281b. The spring 286 is centered on longitudinal axis 263, with one end supported by the inner surface -12 - of second end cap 278 and the other end pressed against push rod base 281a. The Belleville spring 286 is placed in compression between end cap 278 and base 281a to impart a longitudinal force on base 281a which is transmitted through second flux return element 273 to drive rod 261.

In operation and use, actuator 261 is driven by an alternating signal provided by the controller and power supply 267. As more fully described in U.S. patent application Serial No. 08/855,228 filed May 13, 1997 (A-64718), the electrical input signal causes drive rod 262 to longitudinally extend and retract at the frequency of the electrical input signal. In general, the electrical input signal from the controller and power supply 267 causes drive coil 266 to generate a magnetic field about the drive coil having a strength, phase and rate of change of polarity corresponding to the amplitude, phase and frequency of the electrical input signal. Drive coil 266 is sized and shaped and positioned relative to the drive rod 262 so that the magnetic field generated thereby preferably extends through the entire drive rod 262. The magnetic field causes the magnetostrictive drive rod 262 to change shape or strain. More specifically, the magnetic moments in the magnetostrictive material of the drive rod align with longitudinal axis 263 when a magnetic field parallel to axis 263 is applied to drive rod 262. The changing magnetic field produced by drive coil 266 causes the drive rod 36 to dynamically expand from a first or statically biased or home position to a second or elongated position and relax back to its home position at the frequency of the electrical input signal. Belleville spring 286 serves to create a longitudinal preload on drive rod 262 which remains constant throughout the actuation and deactuation of the drive rod 262. The preload externally causes die magnetic moments in the magnetostrictive composite material of the drive rod 262 to be more perfecdy oriented perpendicular to longitudinal axis 267. The uniformity of the magnetic bias through drive rod 262 is enhanced by the use of flux return elements 272 and 273, which also serve to capture the AC magnetic field created by drive coil 266 and channel that field through the drive rod 262 so as to increase the AC magnetic field intensity in the drive rod and thus enhance the performance of actuator 261. The extension and retraction of drive rod 262 causes push rod 281 to reciprocate longitudinally along axis 263.

In another embodiment of the magnetostrictive transducer of the present invention, a multilayer magnetostrictive transducer 291 substantially similar to transducer 29 is shown in FIG. 21. The transducer 291 comprises a strip 292 substantially similar to strip 31 and like reference numerals are used to describe like components of strips 31 and 291. The strip 292 has a first layer in the form of metal substrate 32 and a second layer 293 at least partially made of a magnetostrictive material. Specifically, the second layer 293 is made of from any suitable magnetostrictive composite material such as the magnetostπctive composite materials described above with respect to drive rod 262.

Dynamic magnetic field generation means is provided in multilayer transducer 291 for producing an electromagnetic field which extends through at least a portion of second layer 293 to change the shape of the strip 292. In this regard, a coil 294 made from any suitable electrically conductive material is embedded in die magnetostrictive composite material of the second layer

293. T e drive coil 294 is electrically coupled to controller and power supply 43.

In operation and use, transducer 291 can be operated as a driver or a sensor in the same manner as the multilayer transducers described above. When utilized as an actuator, the drive signal to coil 294 results in a magnetic field which extends through the second layer 293 and causes the magnetostrictive material in the second layer 293 to change shape. • It should be appreciated that a coil similar to coil 294 can be embedded in the first layer 32 for serving as an alternate or additional magnetic field generator 41. In addition, a single layer transducer can be provided in which the drive and/or sensing coil is embedded the layer formed from a magnetostrictive composite material.

From the foregoing, it can be seen that a multilayer transducer which utilizes a magnetostrictive material has been provided. The multilayer transducer can optionally have an integral magnetic layer for biasing the magnetostrictive material. The multilayer transducer can optionally have a layer of magnetostrictive material which enlarges in the presence of a magnetic field and a layer of a magnetic material which shortens in the presence of a magnetic field. The multilayer transducer can be used for sensing and/or actuation. A magnetostrictive composite material having high-performance thermoplastic resins such as LaRC™-SI or -13 -

PEΗ-5 can be used as a binder for magnetostrictive particles in the transducer. In addition, die drive and/or sensing coil can be embedded in a composite material of the multilayer transducer.

-14 - What is claimed is:

1. A multilayer magnetostrictive transducer comprising a first layer made at least partially of a magnetic material, a second layer made at least partially of a magnetostrictive material disposed on the first layer whereby the first layer magnetically biases the magnetostrictive material of the second layer and means for producing a magnetic field which extends through at least a portion of the second layer to change the shape of the second layer and thus exert a force on the first layer.

2. A transducer as in Claim 1 wherein the first layer has first and second opposite surfaces, the second layer being disposed on the first surface, a third layer made at least partially of a magnetostrictive material disposed on the second surface of the first layer whereby the first layer is disposed between the second and third layers.

3. A transducer as in Claim 2 wherein the first layer is made at least partially of a magnetostrictive material which elongates when in the presence of a magnetic field and the tiiird layer is made at least partially of a magnetostrictive material which contracts when in the presence of a magnetic field.

4. A transducer as in Claim 1 wherein the second layer is a vacuumed-deposited layer of a magnetostrictive material.

5. A transducer as in Claim 1 wherein the first and second layers are each thin films.

6. A transducer as in Claim 1 wherein the magnetostrictive material is a rare earth-iron magnetostrictive material.

7. A transducer as in Claim 6 wherein the rare earth-iron magnetostrictive material is TERFENOL-D.

8. A transducer as in Claim 1 wherein the means for producing a magnetic field which extends through at least a portion of the second layer is a conductive coil which extends around the first and second layers.

9. A transducer as in Claim 1 wherein the means for producing a magnetic field which extends through at least a portion of the second layer is a planar coil disposed adjacent one of the first and second layers.

10. A transducer as in Claim 1 wherein die second layer is formed from particles of a magnetostrictive material embedded in a resin selected from the group consisting of PETI-5 and LaRC™-SI.

11. A transducer as in Claim 1 wherein the second layer is formed of a magnetostrictive composite material and the means for producing a magnetic field which extends through at least a portion of the second layer is a coil embedded in the magnestostrictive composite material.

12. A multilayer magnetostrictive transducer comprising a first layer made at least partially of a magnetostrictive material, a second layer made at least partially of a magnetic material disposed on the first layer for magnetically biasing the magnetostrictive material of the first layer and a coil of an electrically conductive material in close proximity to the first layer for producing a magnetic field which extends dirough at least a portion of the first layer to change the shape of the first layer or to produce an electrical signal in response to a change in shape of the first layer. -15 -

13. A transducer as in Claim 12 wherein the first layer is made at least partially of a magnetostrictive material which enlarges when in the presence of a magnetic field, a tiiiid layer made at least partially of a magnetostrictive material which contracts when in the presence of a magnetic field disposed on the second layer whereby the second layer is disposed between the first and third layers.

14. A transducer as in Claim 13 wherein the first and second layers are each thin films.

15. A transducer as in Claim 12 wherein the first layer is formed from particles of a magnetostrictive material embedded in a resin selected from the group consisting of PETI-5 and LaRC™-SI.

16. A multilayer magnetostrictive transducer comprising a first layer, a second layer made of a magnetostrictive composite material disposed on the first layer and a coil for producing a magnetic field which extends through at least a portion of the second layer to change the shape of the second layer at least partially embedded in the magnetostrictive composite material of the first layer.

17. A transducer as in Claim 16 wherein the magnetostrictive composite material is formed from particles of a magnetostrictive material embedded in a resin selected from the group consisting of PETI-5 and LaRC™-SI.

18. A magnetostrictive actuator comprising an active element made from particles of a magnetostrictive material embedded in a resin selected from die group consisting of PETI-5 and LaRC™-SI and being changeable from a first shape to a second shape in the presence of a magnetic field and a coil of an electrically conductive material for producing a magnetic field which extends through at least a portion of the active element.

19. An actuator as in Claim 18 further comprising a permanent magnet in the vicinity of the active element for providing a DC magnetic bias to the active element.

20. An actuator as in Claim 18 wherein die active element has first and second ends, first and second flux return elements adjacent die first and second ends of the magnetostrictive element for capturing magnetic flux produced by said coil and directing the magnetic flux through the active element.