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WO2001016484A9 - A magnetically-assisted shape memory alloy actuator - Google Patents

A magnetically-assisted shape memory alloy actuator

Info

Publication number
WO2001016484A9
WO2001016484A9 PCT/IB2000/001729 IB0001729W WO0116484A9 WO 2001016484 A9 WO2001016484 A9 WO 2001016484A9 IB 0001729 W IB0001729 W IB 0001729W WO 0116484 A9 WO0116484 A9 WO 0116484A9
Authority
WO
WIPO (PCT)
Prior art keywords
sma
sma member
magnet
actuator
magnetically
Prior art date
Application number
PCT/IB2000/001729
Other languages
French (fr)
Other versions
WO2001016484A2 (en
WO2001016484A3 (en
Inventor
William P Taylor
Original Assignee
Teledyne Tech Inc
William P Taylor
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Teledyne Tech Inc, William P Taylor filed Critical Teledyne Tech Inc
Priority to AU22109/01A priority Critical patent/AU2210901A/en
Publication of WO2001016484A2 publication Critical patent/WO2001016484A2/en
Publication of WO2001016484A3 publication Critical patent/WO2001016484A3/en
Publication of WO2001016484A9 publication Critical patent/WO2001016484A9/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/0036—Switches making use of microelectromechanical systems [MEMS]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
    • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
    • F03G7/061—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element
    • F03G7/0614—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element using shape memory elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
    • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
    • F03G7/061—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element
    • F03G7/0614—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element using shape memory elements
    • F03G7/06147—Magnetic shape memory alloys, e.g. ferro-magnetic alloys
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
    • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
    • F03G7/062—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the activation arrangement
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
    • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
    • F03G7/061—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element
    • F03G7/0616—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element characterised by the material or the manufacturing process, e.g. the assembly

Definitions

  • the present invention is directed to an actuator and, more particularly, to a
  • a shape memory alloy is a material which has the ability to transition
  • SMA is cold, that is, when the SMA is below its phase transition temperature, it has a
  • SMA materials are advantageous for use in micromachined actuators, also
  • SMA actuating devices can provide
  • actuators provide a relatively large force in a relatively small three-dimensional space.
  • SMA microactuators provide the potential to be fabricated using
  • MEMS microelectromechanical systems
  • SMA actuators may be incorporated on a substrate with electronic circuitry to share the same power supply
  • SMA microactuators typically use electrical current or heat
  • SMA microactuators employ a biasing spring to bias the SMA in its deformed shape
  • microactuators on an individual basis, thereby increasing overall fabrication costs of
  • the present invention is directed to an actuator.
  • the actuator includes an
  • the actuator includes a second magnet
  • the present invention is directed to a relay.
  • the relay
  • 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-
  • SMA actuator is in another of the actuated position and the non-actuated position.
  • the present invention is directed to a valve.
  • the present invention is directed to a method of
  • the method includes cooling the SMA member to a
  • the present invention is directed to a method of
  • the method includes
  • the present invention is directed to a method of
  • the method includes
  • the SMA member is in another of the martensitic phase and the parent austenitic
  • the present invention represents an advancement over relevant actuators in
  • an actuator according to the present invention may be formed using batch
  • Fig. 1 is a combination cross-sectional side-view and block diagram
  • Fig. 2 is a combination cross-sectional side-view and block diagram
  • FIG. 3 is a cross-sectional side-view of a microactuator according to another
  • Fig. 4 is a cross-sectional side-view of the microactuator of Fig. 3 in the "ON"
  • Fig. 5 is a combination cross-sectional side-view and block diagram
  • Fig. 6 is a combination cross-sectional side-view and block diagram
  • Fig. 7 is a cross-sectional side-view of a microrelay according to the present
  • Fig. 8 is a cross-sectional side-view of the microrelay of Fig. 7 in the "OPEN"
  • Fig. 9 is a cross-sectional side-view of a microrelay according to another
  • Fig. 10 is a cross-sectional side-view of the microrelay of Fig. 9 in the
  • Fig. 11 is a cross-sectional side-view of a microrelay according to another
  • Fig. 12 is a cross-sectional side-view of the microrelay of Fig. 11 in the
  • Fig. 13 is a cross-sectional side-view of a microvalve according to the present
  • Fig. 14 is a cross-sectional side-view of the microvalve of Fig. 13 in the
  • Fig. 15 is a cross-sectional side-view of a microvalve according to another
  • Fig. 16 is a cross-sectional side-view of the microvalve of Fig. 15 in the
  • Fig. 17 is a cross-sectional side-view of a microvalve according to another
  • Fig. 18 is a top-view of the microvalve of Fig. 17.
  • Figs. 1 and 2 illustrate a microactuator 10 according to the present invention in
  • microactuator 10 includes a member 12, a magnetic material portion 14, a first magnet
  • the magnetic material portion 14 is separated from the first magnet 16 by a distance
  • microactuator 10 of the present invention may be used in any device
  • remote actuation such as, for example, relays, valves, and pumps.
  • the member 12 is constructed of a shape memory alloy (SMA) such as, for
  • TiNi titanium nickel
  • alloy material undergoes a thermoelastic phase transformation in passing from a
  • phase change temperature range To realize a mechanical translation of such a phase
  • the alloy possesses a particular crystalline structure, which allows the material to
  • the SMA material remains deformed until
  • the SMA member 12 is biased in its deformed shape by the magnetic attraction
  • material portion 14 is attached to a surface of the SMA member 12, and may be, for
  • a "soft" magnetic material such as, for example, nickel iron, nickel, or nickel
  • the magnetic material portion 14 is a
  • the magnetic material portion 14 may also be soft ferrites such
  • nickel-zinc or manganese-zinc ferrites As described hereinbelow in
  • portion 14 may also be a "hard”, or permanent, magnetic material such as, for
  • the magnetic material portion 14 may also include an electromagnet.
  • the magnetic material portion 14 may also include an electromagnet.
  • the SMA member 12 is formed from a
  • the SMA member 12 and the magnetic portion 14 may be
  • the first magnet 16 and the first magnet 16 are identical to one embodiment of the present invention.
  • magnet 16 may be, for example, a hard, or permanent, magnet or an electromagnet.
  • the first magnet 16 is a permanent magnet
  • the first magnet 16 may be constructed of, for example, AlNiCo, NdFeB, SmCo, hard ferrites
  • the SMA member 12 may be heated, for example, using electrical current or
  • Figs, land 2 illustrate an embodiment of the present invention using
  • the power control 18 modulates the
  • switch 22 controls whether electrical power is supplied to the SMA member 12.
  • switch 22 may be eliminated if its function is, for example, performed by the power
  • 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
  • microactuator 10 illustrated in Figs. 3 and 4 are in the
  • the SMA member 12 is in its parent austenitic phase and in its memory
  • the illustrated embodiment includes an insulating layer 26 constructed of, for
  • the resistive heaters 24 may be patterned on
  • the insulating layer 26 using, for example, conventional microfabrication techniques,
  • heaters 24 may be patterned directly on to the SMA member 12.
  • the SMA member 12 may be patterned directly on to the SMA member 12.
  • 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
  • the SMA member 12 is biased into its deformed state by the magnetic attraction
  • first magnet 16 biased into its deformed shape by first magnet 16 as illustrated in Fig. 1.
  • the SMA member 12 is
  • the switch 22 is closed in Fig. 1 and open in Fig. 2.
  • the SMA member 12 assumes the memory shape illustrated
  • first magnet 16 are both hard magnetic materials and like polarized such that a repulsive force exists between the two.
  • inventions may be fabricated by forming thin films on a substrate using conventional
  • microfabrication techniques including sputtering of an SMA film to form the SMA
  • the first magnet 16 may also be formed using
  • microactuator 10 according to the present invention
  • inventions may be fabricated using exclusively batch fabrication techniques.
  • microactuator 10 of the present invention may be formed using, for example
  • the SMA member 12 is
  • the magnetic material portion 14 and the first magnet 16 may be realized where the
  • Figs. 5 and 6 illustrate the microactuator 10 in the "OFF" (i.e., non-actuated)
  • the microactuator 10 illustrated in Figs. 5 and 6 includes a
  • second magnet 28 which may be, for example, an electromagnet, such as an electromagnet
  • the second magnet 28 is located
  • first magnet 16 may be below the second magnet 28 or interleaved
  • the magnetic flux force of the second magnet 28 may be oriented to aid or
  • the magnetic force of second magnet 28 may be
  • the second magnet 28 may be turned off if the attractive force of the first magnet 16 is
  • the second magnet 28 may be turned off.
  • Fig. 5 In another embodiment of the microactuator 10 of the present invention, Fig. 5
  • Fig. 6 illustrates the "OFF" (i.e., non-
  • magnet 16 and magnetic material portion 14 are like polarized such that a repulsive
  • the present invention is also directed to a microrelay employing a
  • FIGs. 7 and 8 illustrate a microrelay 40
  • the microrelay 40 is formed on a substrate 42.
  • the substrate 42 is formed on a substrate 42.
  • the substrate 42 may include a semiconductor material such as, for
  • silicon GaAs, or SiGe
  • a non-conducting material such as, for example, silicon, GaAs, or SiGe
  • microrelay 40 include the SMA member 12, the magnetic material portion 14, and the
  • the microrelay 40 includes a moving contact 44 and a pair of fixed
  • the contacts 44, 46 may be any conducting material which ensures
  • An insulator 48 may be
  • the insulator 48 may
  • silicon nitride silicon dioxide
  • glass glass
  • air or polymers such as, for
  • the microrelay 40 further includes a support 50 to support the
  • the support 50 is of sufficient mechanical structure to support the
  • SMA member 12 may be constructed of, for example, metal, ceramic, or
  • the microrelay 40 may be constructed using, for example, conventional
  • SMA member 12 is in its martensitic phase, the attractive magnetic force between the
  • the SMA member 12 may be heated by, for example, electrical current flowing
  • the SMA member 12 in another embodiment of the present invention, the SMA member 12
  • Fig. 7 is in its parent austenitic phase and in its martensitic phase in Fig.
  • the SMA member 12 is
  • the magnetic material portion 14 may be
  • first and second substrates may be bonded together using conventional wafer bonding
  • Figs. 9 and 10 illustrate another embodiment of a microrelay 40 according to
  • 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
  • the first magnet 16 may be positioned, for example,
  • the first magnet 16 may be below
  • the of the second magnet 28 may be oriented to aid or oppose the magnetic force of the
  • 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
  • the SMA member 12 in another embodiment of the present invention, the SMA member 12
  • Fig. 9 is in its parent austenitic phase and in its martensitic phase in Fig.
  • the SMA member 12 is
  • an upper moving contact 52 is provided on the upper surface of the SMA member
  • the upper moving contact 52 is in contact with the upper fixed
  • 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
  • the SMA member 12 is biased by a repulsive force between the first
  • microrelay 40 In other embodiments of the microrelay 40 according to the present invention,
  • moving contacts may be integrated with the SMA member 12.
  • the present invention is also directed to a microvalve 60 employing a
  • FIGs. 13 and 14 illustrate a microvalve 60 in the "CLOSED"
  • the microvalve 60 is formed on the substrate 42.
  • the microvalve 60 includes a number of ports 62, 63 defining openings in the
  • fluid or gas may enter the microvalve 60
  • openings 62 and 63 may be formed
  • anisotropic etching of a silicon substrate etching of a glass substrate
  • the microvalve 60 may further include
  • the seal 64 may be constructed of, for example, metal or polymer such as, for
  • the first magnet 16 may include, for example, a ring of
  • the first magnet 16 comprises a number of small bar magnets 66 oriented around the
  • the microvalve 60 may be formed on the substrate 42 using, for example
  • the first magnet 16 biases the SMA member 12 to its deformed state, thereby causing the SMA member 12 to engage the
  • the SMA member 12 cools, allowing it to be biased by the magnetic
  • the SMA member 12 is biased by a repulsive force between the magnetic material
  • member 12 illustrated in Fig. 13 is in its austenitic phase and in its martensitic phase
  • Figs. 17 and 18 illustrate a microvalve 60 according to another embodiment of
  • microvalve 60 includes one opening 62.
  • the SMA member 12 is patterned to include
  • Figs. 17 and 18 includes four arms 70, although in other embodiments of the present
  • gas 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
  • the first magnet may include, for example, a number of bar magnets

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Micromachines (AREA)
  • Reciprocating, Oscillating Or Vibrating Motors (AREA)

Abstract

An actuator (10) including an SMA member (12), a magnetic material portion (14) connected to the SMA member, and a first magnet (16) in magnetic communication with the magnetic material portion.

Description

A MAGNETICALLY-ASSISTED SHAPE MEMORY ALLOY ACTUATOR
BACKGROUND OF INVENTION
Field of Invention
The present invention is directed to an actuator and, more particularly, to a
magnetically-assisted shape memory alloy actuator.
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
dl5 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 dj. 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 d^ 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.

Claims

CLAIMSWhat is claimed is:
1. An actuator, comprising
an SMA member;
a magnetic material portion connected to the SMA member; and
a first magnet in magnetic communication with the magnetic material portion.
2. The actuator of claim 1 , wherein the magnetic material portion is
selected from the group consisting of soft magnetic material and hard magnetic
material.
3. The actuator of claim 1 , wherein the magnetic material portion
includes an electromagnet.
4. The actuator of claim 1, wherein the first magnet is selected from the
group consisting of a permanent magnet and an electromagnet.
5. The actuator of claim 1, wherein the magnetic material portion and the
first magnet are like polarized.
6. The actuator of claim 1 , wherein the magnetic material portion and the
first magnet are oppositely polarized.
7. The actuator of claim 1 , further comprising a second magnet in
magnetic commumcation with the magnetic material portion.
8. The actuator of claim 7, wherein the first magnet is selected from the
group consisting of a permanent magnet and an electromagnet and the second magnet
is an electromagnet.
9. The actuator of claim 7, wherein a magnetic force of the first magnet
and a magnetic force of the second magnet are oriented in a same direction.
10. The actuator of claim 7, wherein a magnetic force of the first magnet
and a magnetic force of the second magnet are oriented in an opposite direction.
11. The actuator of claim 1 , wherein the SMA member includes nickel
titanium.
12. An actuator, comprising:
an SMA member; and
means for biasing the SMA member with a magnetic force when the SMA
member is in a martensitic phase.
13. The actuator of claim 12, further comprising means for transitioning
the SMA member between the martensitic phase and a parent austenitic phase.
14. A relay, comprising:
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.
15. The relay of claim 14, wherein the moving contact is coupled to the
fixed contact when the magnetically-assisted SMA actuator is in the non-actuated
position and not coupled to the fixed contact when the magnetically-assisted SMA
actuator is in the actuated position.
16. The relay of the claim 14, wherein the moving contact is coupled to
the fixed contact when the magnetically-assisted SMA actuator is in the actuated
position and not coupled to the fixed contact when the magnetically-assisted SMA
actuator is in the non-actuated position.
17. The relay of claim 14, wherein the moving contact includes at least one
moving contact connected to the magnetically-assisted SMA actuator.
18. The relay of claim 17, wherein the fixed contact includes at least one
fixed contact connected to the substrate.
19. The relay of claim 14, wherein the magnetically-assisted SMA 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.
20. The relay of claim 19, wherein the first magnet is connected to the
substrate.
21. The relay of claim 19, wherein the magnetically-assisted SMA actuator
further comprises a second magnet in magnetic communication with the magnetic
material portion.
22. The relay of claim 21 , wherein the second magnet is an electromagnet.
23. The relay of claim 21 , wherein the first magnet and the second magnet
are connected to the substrate.
24. The relay of claim 14, further comprising: an upper moving contact connected to the magnetically-assisted SMA
actuator; and
an upper fixed coupled to the upper moving contact when the magnetically-
assisted SMA actuator is in one of the actuated position and the non-actuated position
and not coupled to the upper moving contact when the magnetically-assisted SMA
actuator is in another of the actuated position and the non-actuated position.
25. A valve, comprising:
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 not covering the opening when the magnetically-
assisted SMA actuator is in another of the actuated position and non-actuated position.
26. The valve of claim 25, wherein the portion of the magnetically-assisted
SMA actuator is engaged with the surface and covering the opening when the
magnetically-assisted SMA actuator is in the non-actuated position and not engaged
with the surface and not covering the opening when the magnetically-assisted SMA
actuator is in the actuated position.
27. The valve of claim 25, wherein the portion of the magnetically-assisted
SMA actuator is engaged with the surface and covering the opening when the magnetically-assisted SMA actuator is in the actuated position and not engaged with
the surface and not covering the opening when the magnetically-assisted SMA
actuator is in the non-actuated position.
28. The valve of claim 25, wherein the surface includes a substrate and a
seal connected to the substrate around the opening.
29. The valve of claim 25, wherein the magnetically-assisted SMA
actuator comprises:
an SMA member;
a magnetic material portion connected to the SMA member; and
a first magnet connected in magnetic communication with the magnetic
material portion.
30. The valve of claim 25, wherein the first magnet is connected to the
surface.
31. The valve of claim 29, wherein the portion of the magnetically-assisted
SMA actuator engaged with the surface and covering the opening when the
magnetically-assisted SMA actuator is in one of the actuated position and the non-
actuated position includes the SMA member.
32. The valve of claim 29, wherein the first magnet includes a magnetic
ring around the opening.
33. The valve of claim 29, wherein the first magnet includes a plurality of
magnets oriented around the opening.
34. A method of biasing an SMA member, comprising:
cooling the SMA member to a martensitic phase; and
exerting a magnetic force on a magnetic material portion connected to the
SMA member.
35. The method of claim 34, wherein exerting a magnetic force includes
exerting an attractive magnetic force on the magnetic material portion connected to
the SMA member.
36. The method of claim 34, wherein exerting a magnetic force includes
exerting a repulsive magnetic force on the magnetic material portion connected to the
SMA member.
37. The method of claim 34, further comprising heating the SMA member
to a parent austenitic phase.
38. The method of claim 37, wherein heating the SMA member includes
conducting electric current in the SMA member.
39. The method of claim 37, wherein heating the SMA member includes
heating a device in thermal communication with the SMA member.
40. A method of switching a relay having a first contact and a second
contact, comprising:
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.
41. The method of claim 40, wherein biasing the SMA member includes
biasing the SMA member with a magnetic force such that the first contact engages the
second contact when the SMA member is in the martensitic phase and does not
engage the second contact when the SMA member is in the parent austenitic phase.
42. The method of claim 40, wherein biasing the SMA member includes
biasing the SMA member with a magnetic force such that the first contact engages the
second contact when the SMA member is in the parent austenitic phase and does not
engage the second contact when the SMA member is in the martensitic phase.
43. The method of claim 40, wherein biasing the SMA member with a
magnetic force includes biasing the SMA member with a magnet having an attractive
magnetic force between the magnet and a magnetic material portion connected to the
SMA member.
44. The method of claim 40, wherein biasing the SMA member with a
magnetic force includes biasing the SMA member with a magnet having a repulsive
magnetic force between the magnet and a magnetic material portion connected to the
SMA member.
45. A method of operating a valve having an opening defined by a surface,
comprising:
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.
46. The method of claim 45, wherein biasing the SMA member includes
biasing the SMA member such that the SMA member engages the surface and covers
the opening when the SMA member is in the martensitic phase and does not engage
the surface and does not cover the opening when the SMA member is in the parent
austenitic phase.
47. The method of claim 45, wherein biasing the SMA member includes
biasing the SMA member such that the SMA member engages the surface and covers
the opening when the SMA member is in the parent austenitic phase and does not
engage the surface and does not cover the opening when the SMA member is in the
martensitic phase.
PCT/IB2000/001729 1999-09-02 2000-08-30 A magnetically-assisted shape memory alloy actuator WO2001016484A2 (en)

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Applications Claiming Priority (2)

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US09/389,274 1999-09-02

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