Description of the Background A shape memory alloy (SMA) is a material which has the ability to transition from a deformed state to a predetermined, or memory, shape when heated. When an SMA is cold, that is, when the SMA is below its phase transition temperature, it has a very low yield strength and can be deformed into a new shape, which the SMA will retain when below the phase transition temperature. When, however, the material is heated through its phase transition temperature, it undergoes a change in crystal structure which causes it to revert forcefully to its original shape imposed on it during annealing.

SMA materials are advantageous for use in micromachined actuators, also called microactuators, for several reasons. First, SMA actuating devices can provide an energy density much greater than other actuating mechanisms. That is, SMA actuators provide a relatively large force in a relatively small three-dimensional space.

Second, SMA microactuators provide the potential to be fabricated using microelectromechanical systems (MEMS) fabrication techniques, such as photolithography and selective etching, as well as according to conventional microelectronic and laminate-based fabrication methods. Third, SMA actuators may

be incorporated on a substrate with electronic circuitry to share the same power supply as the circuitry.

Relevant art SMA microactuators typically use electrical current or heat resistors to heat the SMA above its phase transition temperature. Typical relevant art SMA microactuators employ a biasing spring to bias the SMA in its deformed shape when the SMA is below it phase transition temperature. The relevant art also discloses the use of a pressurized fluid at a static pressure to exert a biasing force on the SMA. These biasing methods are not, however, ideal for batch fabrication of MEMS devices. Rather, the biasing springs and fluids must be incorporated into the microactuators on an individual basis, thereby increasing overall fabrication costs of the devices.

Accordingly, there exists a need in the relevant art for a SMA microactuator in which the biasing member of the microactuator is capable of fabrication using batch fabrication techniques.

SUMMARY OF THE INVENTION The present invention is directed to an actuator. The actuator includes an SMA member, a magnetic material portion connected to the SMA member, and a first magnet in magnetic communication with the magnetic material portion. According to another embodiment of the present invention, the actuator includes a second magnet in magnetic communication with the magnetic material portion.

In another embodiment, the present invention is directed to a relay. The relay includes a substrate, a fixed contact connected to the substrate, a magnetically-assisted SMA actuator connected to the substrate, and a moving contact connected to the

magnetically-assisted SMA actuator and coupled to the fixed contact when the magnetically-assisted SMA actuator is in one of an actuated position and a non- actuated position and not coupled to the fixed contact when the magnetically-assisted SMA actuator is in another of the actuated position and the non-actuated position.

In another embodiment, the present invention is directed to a valve. The valve includes a surface defining an opening therethrough and a magnetically-assisted SMA actuator connected to the surface and having a portion engaged with the surface and covering the opening when the magnetically-assisted SMA actuator is in one of an actuated position and a non-actuated position and not engaged with the surface and not covering the opening when the magnetically-assisted SMA actuator is in another of the actuated position and the non-actuated position.

In another embodiment, the present invention is directed to a method of biasing an SMA actuator. The method includes cooling the SMA member to a martensitic phase and exerting a magnetic force on a magnetic material portion connected to the SMA member.

In another embodiment, the present invention is directed to a method of switching a relay having a first contact and a second contact. The method includes connecting the first contact to an SMA member, transitioning the SMA member between a martensitic phase and a parent austenitic phase, and biasing the SMA member with a magnetic force when the SMA member is in the martensitic phase such that the first contact engages the second contact when the SMA member is in one of the martensitic phase and the parent austenitic phase and does not engage the second contact when the SMA member is in another of the martensitic phase and the parent austenitic phase.

In another embodiment, the present invention is directed to a method of operating a valve having an opening defined by a surface. The method includes transitioning an SMA member between a martensitic phase and a parent austenitic phase, and biasing the SMA member with a magnetic force when the SMA member is in the martensitic phase such that the SMA member engages the surface and covers the opening when the SMA member is in one of the martensitic phase and the parent austenitic phase and does not engage the surface and does not cover the opening when the SMA member is in another of the martensitic phase and the parent austenitic phase.

The present invention represents an advancement over relevant actuators in that an actuator according to the present invention may be formed using batch fabrication techniques. These and other advantages and benefits of the present invention will become apparent from the Detailed Description of the Invention hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS For the present invention to be clearly understood and readily practiced, the present invention will be described in conjunction with the following figures, wherein: Fig. 1 is a combination cross-sectional side-view and block diagram illustrating a microactuator in the"OFF"position according to the present invention; Fig. 2 is a combination cross-sectional side-view and block diagram illustrating the microactuator of Fig. 1 in the"ON"position;

Fig. 3 is a cross-sectional side-view of a microactuator according to another embodiment of the present invention in the"OFF"position; Fig. 4 is a cross-sectional side-view of the microactuator of Fig. 3 in the"ON" position; Fig. 5 is a combination cross-sectional side-view and block diagram illustrating a microactuator according to another embodiment of the present invention in the"OFF"position; Fig. 6 is a combination cross-sectional side-view and block diagram illustrating the microactuator of Fig. 5 in the"ON"position; Fig. 7 is a cross-sectional side-view of a microrelay according to the present invention in the"CLOSED"position; Fig. 8 is a cross-sectional side-view of the microrelay of Fig. 7 in the"OPEN" position; Fig. 9 is a cross-sectional side-view of a microrelay according to another embodiment of the present invention in the"CLOSED"position; Fig. 10 is a cross-sectional side-view of the microrelay of Fig. 9 in the "OPEN"position; Fig. 11 is a cross-sectional side-view of a microrelay according to another embodiment of the present invention in the"CLOSED"position; Fig. 12 is a cross-sectional side-view of the microrelay of Fig. 11 in the "OPEN"position; Fig. 13 is a cross-sectional side-view of a microvalve according to the present invention in the"CLOSED"position;

Fig. 14 is a cross-sectional side-view of the microvalve of Fig. 13 in the "OPEN"position; Fig. 15 is a cross-sectional side-view of a microvalve according to another embodiment of the present invention in the"CLOSED"position; Fig. 16 is a cross-sectional side-view of the microvalve of Fig. 15 in the "OPEN"position; Fig. 17 is a cross-sectional side-view of a microvalve according to another embodiment of the present invention in the"OPEN"position; and Fig. 18 is a top-view of the microvalve of Fig. 17.

DETAILED DESCRIPTION OF THE INVENTION It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, other elements found in a typical actuator. Those of ordinary skill in the art will recognize that other elements may be desirable. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein.

Figs. 1 and 2 illustrate a microactuator 10 according to the present invention in the"OFF" (or non-actuated) and the"ON" (or actuated) positions, respectively. The microactuator 10 includes a member 12, a magnetic material portion 14, a first magnet 16, a power control 18, a power source 20, and a switch 22. In the"OFF"position, the magnetic material portion 14 is separated from the first magnet 16 by a distance dl, and in the"ON"position the distance between the magnetic material portion 14

and the first magnet 16 is increased to a distance represented by d2. The microactuator 10 transitions from the"OFF"position to the"ON"position by heating the member 12. The microactuator 10 of the present invention may be used in any device requiring remote actuation, such as, for example, relays, valves, and pumps. The present invention will be described herein for use in a microactuator, although the benefits of the present invention may be realized in other applications, such as macroscale actuators.

The member 12 is constructed of a shape memory alloy (SMA) such as, for example, titanium nickel (TiNi) or any other joule-effect alloy. A shape memory alloy material undergoes a thermoelastic phase transformation in passing from a martensitic phase when at a temperature below the material's phase change temperature to a parent austenitic phase in a memory shape when heated through its phase change temperature range. To realize a mechanical translation of such a phase transformation, a particular mechanical configuration, or memory shape, may be imposed on a SMA at an annealing temperature, Ta. Below some lower temperature, To, the alloy possesses a particular crystalline structure, which allows the material to be easily deformed into an arbitrary shape. The SMA material remains deformed until heated above a temperature Te, where To < Te < Ta, at which point the SMA undergoes a change in crystalline structure, and the material forcefully reverts to the memory shape imposed on it during annealing. The phase change temperature range over which the phase transition occurs is defined as being To to Te.

To achieve remote actuation using an SMA, the SMA member 12 is deformed when in its martensitic phase by a biasing force, and then heated through its phase

change temperature range to its parent austenitic phase, causing the SMA member 12 to revert to its memory shape. According to one embodiment of the present invention, the SMA member 12 is biased in its deformed shape by the magnetic attraction between the magnetic material portion 14 and the first magnet 16. The magnetic material portion 14 is attached to a surface of the SMA member 12, and may be, for example, a"soft"magnetic material such as, for example, nickel iron, nickel, or nickel iron molybdenum. For an embodiment in which the magnetic material portion 14 is a soft magnetic material, the magnetic material portion 14 may also be soft ferrites such as, for example, nickel-zinc or manganese-zinc ferrites. As described hereinbelow in conjunction with other embodiments of the present invention, the magnetic material portion 14 may also be a"hard", or permanent, magnetic material such as, for example, AlNiCo, NdFeB, SmCo, hard ferrites such as, for example, strontium ferrite, or hard magnetic polymer composites. According other embodiments of the present invention, the magnetic material portion 14 may also include an electromagnet. In yet other embodiments of the present invention, if the SMA member 12 is formed from a magnetic material, the SMA member 12 and the magnetic portion 14 may be integrated.

According to one embodiment of the present invention, the first magnet 16 and magnetic material portion 14 are oppositely polarized, and the first magnet 16 is located relative to the magnetic material portion 14 such that there exists a magnetic attraction between the magnetic material portion 14 and the first magnet 16. The first magnet 16 may be, for example, a hard, or permanent, magnet or an electromagnet.

For an embodiment in which the first magnet 16 is a permanent magnet, the first

magnet 16 may be constructed of, for example, AlNiCo, NdFeB, SmCo, hard ferrites such as, for example, strontium ferrite, or hard magnetic polymer composites.

The SMA member 12 may be heated, for example, using electrical current or resistive heaters. Figs. land 2 illustrate an embodiment of the present invention using electrical current to heat the SMA member 12. The power control 18 modulates the current flow from the power source 20 to control the heating rate of the SMA member 12, and may be connected to a processor or other control circuit (not shown). The switch 22 controls whether electrical power is supplied to the SMA member 12. The switch 22 may be eliminated if its function is, for example, performed by the power controller 18.

Figs. 3 and 4 illustrate another embodiment of the present invention in which the SMA member 12 is heated by resistive heaters 24. According to one embodiment of the present invention, the microactuator 10 illustrated in Figs. 3 and 4 are in the "OFF" (i. e., non-actuated) and the"ON" (i. e., actuated) positions, respectively. That is, in Fig. 3 the SMA member 12 is in its martensitic phase and in its deformed shape, and in Fig. 4 the SMA member 12 is in its parent austenitic phase and in its memory shape. The illustrated embodiment includes an insulating layer 26 constructed of, for example, polymers, such as polyimide. The resistive heaters 24 may be patterned on the insulating layer 26 using, for example, conventional microfabrication techniques, such as photolithography and selective etching. In an alternative embodiment, the heaters 24 may be patterned directly on to the SMA member 12. In addition, the illustrated embodiment includes two resistive heaters 24, although more or less resistive heaters 24 may also be employed.

The operation of the microactuator 10 will now be described with reference to Figs. 1 and 2. In Fig. 1, the switch 22 is open, causing no electrical power to be supplied to the SMA member 12, causing the SMA member 12 to be at an ambient temperature below its phase change transition temperature. In the martensitic phase, the SMA member 12 is biased into its deformed state by the magnetic attraction between the magnetic material portion 14 and the first magnet 16, which are separated by distance d This corresponds to the"OFF"or non-actuated position of the microactuator 10. Subsequently, the switch 22 is closed, as illustrated in Fig. 2, causing electrical current to flow through the SMA member 12 and heat the SMA member 12 through it phase change temperature range, causing the SMA member 12 to revert to its memory shape with a force great enough to overcome the attractive force of the first magnet 16, thereby pulling the magnetic material portion 14 away from the first magnet 16 to the distance d2. This corresponds to the"ON"or actuated position of the microactuator 10. When the switch 22 is re-opened, the SMA member 12 cools below its phase change temperature, and in its martensitic phase is again biased into its deformed shape by first magnet 16 as illustrated in Fig. 1.

In another embodiment of the present invention, the SMA member 12 is annealed such that its memory shape is that illustrated in Fig. 1, in which case Fig. 1 represents the"ON"position and Fig. 2 illustrates the"OFF"position. (Note that for such an embodiment, the switch 22 is closed in Fig. 1 and open in Fig. 2.) According to such an embodiment, the SMA member 12 assumes the memory shape illustrated in Fig. 1 when it is heated above its phase change temperature range, i. e., when the switch 22 is closed. For this embodiment, the magnetic material portion 14 and the first magnet 16 are both hard magnetic materials and like polarized such that a

repulsive force exists between the two. Once the power is removed from the SMA member 12 and it cools below its phase change temperature, it is biased into its deformed shape, as illustrated in Fig. 2, by the repulsive force between the first magnet 16 and magnetic material portion 14.

Utilizing a magnetic biasing force permits the microactuator 10 of the present invention to be batch fabricated using conventional MEMS fabrication techniques, such as photolithography, selective etching, and screen printing. The present invention may be fabricated by forming thin films on a substrate using conventional microfabrication techniques, including sputtering of an SMA film to form the SMA member 12. In the present invention, the first magnet 16 may also be formed using conventional MEMS fabrication techniques, such as photolithography, selective etching, and screen printing. Thus, the microactuator 10 according to the present invention may be fabricated using exclusively batch fabrication techniques. In addition, the microactuator 10 of the present invention may be formed using, for example, conventional microelectronic fabrication techniques and laminate-based fabrication techniques.

The operation of the microactuator 10 using resistive heaters 24 to heat the SMA member 12, as illustrated in Figs. 3 and 4, is analogous to the operation described hereinabove with respect to Figs. 1 and 2. Using resistive heaters 24, when power is supplied to the heaters 24, the SMA member 12 is heated by the resistive heaters 24 through its phase change temperature range into its memory shape, as illustrated in Fig. 4, corresponding to the"ON"or actuated position. When no power is supplied to the heaters 24, the SMA member 12 cools, and the magnetic attraction between the first magnet 16 and the magnetic material portion 14 biases the SMA

member 12 to its deformed shape as illustrated in Fig. 3, which corresponds to the "OFF"or non-actuated position.

In an alternative embodiment of the present invention, the SMA member 12 is annealed such that its deformed shape is that illustrated in Fig. 4. The SMA member 12 is biased to the deformed shape illustrated in Fig. 4 by a repulsive force between the magnetic material portion 14 and the first magnet 16. A repulsive force between the magnetic material portion 14 and the first magnet 16 may be realized where the two are like polarized, as discussed hereinbefore. According to this embodiment, the "ON"position is illustrated in Fig. 3 and the"OFF"position is illustrated in Fig. 4.

Figs. 5 and 6 illustrate the microactuator 10 in the"OFF" (i. e., non-actuated) and"ON" (i. e., actuated) positions respectively according to another embodiment of the present invention. The microactuator 10 illustrated in Figs. 5 and 6 includes a second magnet 28, which may be, for example, an electromagnet, such as an electromagnetic coil. For the illustrated embodiment, the second magnet 28 is located below the first magnet 16 in relation to the position of the SMA member 12.

Alternatively, the first magnet 16 may be below the second magnet 28 or interleaved with the electromagnetic coil comprising the second magnet 28. The second magnet 28 may be formed using, for example, conventional MEMS batch fabrication techniques, microelectronic fabrication techniques, or laminate-based fabrication techniques.

The magnetic flux force of the second magnet 28 may be oriented to aid or oppose the magnetic force of the first magnet 16. For example, if the distance d2 in Fig. 6 is so great that the magnetic attraction between the magnetic material portion 14 and the first magnet 16 is not sufficient to deform the SMA member 12 when the

member 12 is in its martensitic phase, the magnetic force of second magnet 28 may be oriented to aid the magnetic force of the first magnet 16. In combination, the net flux forces of the first magnet 16 and the second magnet 28 attract the magnetic material portion 14, thereby biasing the SMA member 12 in its deformed shape. Thereafter, the second magnet 28 may be turned off if the attractive force of the first magnet 16 is sufficiently strong to hold the SMA member 12 at the distance dl. Alternatively, if the attractive force of the first magnet 16 is so great that the SMA member 12 cannot overcome the force of the first magnet 16 to revert to its memory shape when heated above its phase change temperature range, the magnetic force of the second magnet 28 may be oriented to oppose the magnetic force of the first magnet 16. In this embodiment, when the second magnet 28 is energized the attractive force of the first magnet 16 may be effectively canceled, thereby allowing the SMA member 12 to revert to its memory shape. Thereafter, the second magnet 28 may be turned off.

In another embodiment of the microactuator 10 of the present invention, Fig. 5 illustrates the"ON" (i. e., actuated) position and Fig. 6 illustrates the"OFF" (i. e., non- actuated) position. According to this embodiment, as discussed hereinbefore, the first magnet 16 and magnetic material portion 14 are like polarized such that a repulsive magnetic force exists between the two.

The present invention is also directed to a microrelay employing a magnetically-assisted SMA microactuator. Figs. 7 and 8 illustrate a microrelay 40 according to one embodiment the present invention in"CLOSED"and"OPEN" states respectively. The microrelay 40 is formed on a substrate 42. The substrate 42, which is the lowest layer of material and any additional or intervening layers or structures formed thereon, may be of any material on which the microrelay 40 is

constructed. The substrate 42 may include a semiconductor material such as, for example, silicon, GaAs, or SiGe, or a non-conducting material such as, for example, ceramic, glass, printed circuit board, alumina, or other materials, such as may be used for silicon-on-insulator semiconductor devices. The actuating components of the microrelay 40 include the SMA member 12, the magnetic material portion 14, and the first magnet 16. The microrelay 40 includes a moving contact 44 and a pair of fixed contacts 46. The contacts 44,46 may be any conducting material which ensures reliable switching such as, for example, plated or sputtered gold metal alloy, silver, platinum, ruthenium, rhodium, or combinations thereof. An insulator 48 may be provided between the first magnet 16 and the fixed contacts 46. The insulator 48 may be, for example, silicon nitride, silicon dioxide, glass, air, or polymers such as, for example, polyimide. The microrelay 40 further includes a support 50 to support the SMA member 12. The support 50 is of sufficient mechanical structure to support the SMA member 12, and may be constructed of, for example, metal, ceramic, or polymer. The microrelay 40 may be constructed using, for example, conventional microfabrication techniques, conventional microelectronic fabrication techniques, and laminate-based fabrication techniques.

According to one embodiment of the present invention, in operation, when the SMA member 12 is in its martensitic phase, the attractive magnetic force between the first magnet 16 and the magnetic material portion 14 biases the SMA member 12 into its deformed shape, thereby causing the moving contact 44 to be in electrical contact with the fixed contacts 46, as illustrated in Fig. 7, allowing electrical current to flow between the fixed contacts 46 via the moving contact 44. When the SMA member 12 is heated to its parent austenitic phase, the member 12 forcefully reverts to its memory

shape, as illustrated in Fig. 8, thereby pulling the moving contact 44 away from the fixed contacts 46 and breaking the electrical connection between the contacts 44,46.

The SMA member 12 may be heated by, for example, electrical current flowing through the member 12 or resistive heaters in close proximity to the member 12, as described hereinbefore with respect to Figs. 1-4.

In another embodiment of the present invention, the SMA member 12 illustrated in Fig. 7 is in its parent austenitic phase and in its martensitic phase in Fig.

8. According to this embodiment, as described hereinbefore, the SMA member 12 is biased by a repulsive magnetic force between the magnetic material portion 14 and the first magnet 16. For such an embodiment, the magnetic material portion 14 may be fabricated as a hard magnetic material on a first substrate and the first magnet 16 as a hard magnet on a second substrate, wherein the two are like polarized. Thereafter, the first and second substrates may be bonded together using conventional wafer bonding techniques to form the microrelay 40.

Figs. 9 and 10 illustrate another embodiment of a microrelay 40 according to the present invention. The microrelay 40 illustrated in Figs. 9 and 10 includes a microactuator as described with respect to Figs. 5 and 6, having a second magnet 28 such as, for example, an electromagnet. The first magnet 16 may be positioned, for example, above the second magnet 28 in relation to the position of the SMA member 12, as illustrated in Figs. 9 and 10. Alternatively, the first magnet 16 may be below the second magnet 28 or interleaved with the second magnet 28. The magnetic force of the second magnet 28 may be oriented to aid or oppose the magnetic force of the first magnet 16, as described hereinbefore. The second magnet 28 may be formed on the substrate 42 using, for example, conventional MEMS fabrication techniques,

conventional microelectronic fabrication techniques, or laminate-based fabrication techniques.

In another embodiment of the present invention, the SMA member 12 illustrated in Fig. 9 is in its parent austenitic phase and in its martensitic phase in Fig.

10. According to this embodiment, as described hereinbefore, the SMA member 12 is biased by a repulsive magnetic force between the magnetic material portion 14 and the first magnet 16.

In another embodiment of the present invention, as illustrated in Figs. 11 and 12, an upper moving contact 52 is provided on the upper surface of the SMA member 12, and two upper fixed contacts 54 are provided above the SMA member 12. For this embodiment, the upper moving contact 52 is in contact with the upper fixed contacts 54 when the SMA member 12 is heated above its phase change temperature range to its memory shape.

In another embodiment of the microrelay 40 according to the present invention, the SMA member 12 illustrated in Fig. 11 is in its austenitic phase, and in Fig. 12 it is in its martensitic phase. According to this embodiment, as described hereinbefore, the SMA member 12 is biased by a repulsive force between the first magnet 16 and magnetic material portion 14.

In other embodiments of the microrelay 40 according to the present invention, various numbers of moving contacts 44 and fixed contacts 46 may be employed such as, for example, one moving contact 44 and one fixed contact 46. In addition, alternative embodiments of the present invention contemplate the use of various numbers of upper contacts 52,54, such as, for example, one upper moving contact 52

and one upper fixed contact 54. In further embodiments of the present invention, the moving contacts may be integrated with the SMA member 12.

The present invention is also directed to a microvalve 60 employing a magnetically-assisted SMA microactuator. According to one embodiment of the present invention, Figs. 13 and 14 illustrate a microvalve 60 in the"CLOSED"and "OPEN"positions respectively. The microvalve 60 is formed on the substrate 42.

The microvalve 60 includes a number of ports 62,63 defining openings in the substrate through which gas or fluid may enter and exit the microvalve 60. For example, in the illustrated embodiment, fluid or gas may enter the microvalve 60 through opening 62 and exit via opening 63. The openings 62 and 63 may be formed using, for example, conventional MEMS fabrication techniques including, for example, anisotropic etching of a silicon substrate, etching of a glass substrate, and pre-formed holes cast in an alumina substrate. The microvalve 60 may further include a seal 64, to better prevent gases and fluids from entering when the microvalve 60 is closed. The seal 64 may be constructed of, for example, metal or polymer such as, for example, polyimide. The first magnet 16 may include, for example, a ring of permanent magnet material around the opening 62, as illustrated in Figs. 13 and 14.

In an alternative embodiment of the present invention illustrated in Figs. 15 and 16, the first magnet 16 comprises a number of small bar magnets 66 oriented around the opening 62. The microvalve 60 may be formed on the substrate 42 using, for example, conventional microfabrication techniques, conventional microelectronic fabrication techniques, or laminate-based fabrication techniques.

According to one embodiment of the present invention, in operation, when the SMA member 12 is in its martensitic phase, the first magnet 16 biases the SMA

member 12 to its deformed state, thereby causing the SMA member 12 to engage the seal 64 and cover the opening 62, as illustrated in Fig. 13. When the SMA member 12 is heated through its phase change temperature range by, for example, passing electrical current through the SMA member 12 or heating the SMA member 12 with resistive heaters, as described hereinbefore with respect to Figs. 1-4, the SMA member transitions to its parent austenitic phase and forcefully reverts to its memory shape, thereby opening the microvalve 60, as illustrated in Fig. 14. Once the heat is removed, the SMA member 12 cools, allowing it to be biased by the magnetic attraction between the first magnet 16 and the magnetic material portion 14. An advantage of this type of microvalve 60 is that if the fluid flow is too great when the valve is in the open position, the fluid may cool the SMA member 12 below its phase change transition temperature range, thereby causing the SMA member 12 to be biased in its deformed state and closing the valve 60. In an alternative embodiment, the SMA member 12 is biased by a repulsive force between the magnetic material portion 14 and the first magnet 16, as described hereinbefore, such that the SMA member 12 illustrated in Fig. 13 is in its austenitic phase and in its martensitic phase in Fig. 14.

Figs. 17 and 18 illustrate a microvalve 60 according to another embodiment of the present invention. According to the embodiment illustrated in Figs. 17 and 18, the microvalve 60 includes one opening 62. The SMA member 12 is patterned to include a number of arms 70 supported by the support 50. The microvalve 60 illustrated in Figs. 17 and 18 includes four arms 70, although in other embodiments of the present invention a different number of arms 70 may be employed. According to this embodiment, when the SMA member 12 is not engaged with the seal 64, gas may

enter the microvalve 60 through the opening 62 and flow, as illustrated by arrow A and A'in Fig. 17, around the arms 70 of the SMA member 12 to exit the microvalve 60 at the top. For the illustrated embodiment of Figs. 17 and 18, the first magnet 16 includes a ring of magnetic material oriented around the opening 62. In another embodiments, the first magnet may include, for example, a number of bar magnets oriented around the opening 62, as described hereinbefore with respect to Figs. 15 and 16.

Those of ordinary skill in the art will recognize that many modifications and variations of the present invention may be implemented. For example, other materials and processes may also be used to make devices embodying the present invention.

Furthermore, the materials and processes disclosed are illustrative, but are not exhaustive. In addition, the described sequences of operating and manufacturing the devices described herein may also be varied. The foregoing description and the following claims are intended to cover all such modifications and variations.