CN1348597A - Bistable micro switch and manufacturing method thereof - Google Patents

Abstract

The present invention provides a bistable switch using a shape memory alloy, and a method for manufacturing the same. More specifically, the bistable switch includes a substrate having at least one power source, a flexible sheet having a first distal end secured to the substrate, a bridge contact formed at a second and opposite distal end of the flexible sheet, and at least one thermally actuated element coupled to a first surface of the flexible sheet and between the second distal end and the power source. During operation, current from the power source through the thermally actuated element indirectly bends the flexible sheet and shorts the signal contact on the substrate with a sustainable force.

Description

Bistable micro switch and manufacturing method thereof

The present invention relates generally to a microswitch, and more particularly to a micromachined bistable switch using a shape memory alloy.

The first electromechanical and solid-state snap switches were developed in the late 1940s. Since then, the electronics industry has pushed the limits of manufacturing and functionality used to produce such switches. In particular, current electromechanical microswitches present technical deficiencies in size, cost, functionality, durability, and connection techniques for high frequency applications. Also, solid state switches exhibit an exceptionally high off-state to on-state impedance ratio and, for many purposes, undesirably high on-state "contact" resistance values in the off-state coupling capacitance. Accordingly, the electronics industry is currently searching for new and innovative ways of making switches that are smaller, more reliable, durable, versatile, and cost effective.

In a variety of current and projected circuit applications, there is a need for low cost, miniaturized switching devices that are constructed on conventional hybrid circuit substrates or boards and that have bistable capability. In addition, the fabrication processes used for these devices should be compatible with conventional solid state techniques, such as thin film deposition and patterning processes used to form conductive paths, contact pads, and passive circuit elements included in such circuits.

A shape memory alloy ("SMA") is a known material capable of undergoing plastic deformation from a "deformed" shape to a "memory" shape when heated. If the SMA material is then allowed to cool, it partially returns to its deformed shape, and can return completely. In other words, SMA materials undergo a reversible transformation from the austenitic state to the martensite state as a function of temperature.

The research and development company has only scratched the surface of how this controllably shape-deformable material could be used in switch structures. For example, conventional electromechanical switches have used SMA wires as the rotary actuator and bent SMA pieces to form a valve. The wire is twisted or twisted about its longitudinal axis, and the ends of the wire are then restrained from movement. The blade actuator is mechanically coupled to one or more movable elements such that temperature-induced deformation of the actuator exerts a force, or produces movement of the mechanical element.

Problems associated with these and similar SMA switch configurations and fabrication techniques are similar to those described above for conventional electromechanical switches. In particular, size, reliability, durability, functionality, and cost constraints limit the usefulness of prior art SMA switches.

When closed, conventional switches and relays, with or without shape memory alloys, are typically large, heavy, or too fragile for industrial purposes or mass production. Accordingly, it would be advantageous to develop a switch or relay that would benefit from the properties of shape memory alloys and would eliminate the above-listed problems of current switch technologies, which may or may not use shape memory alloys.

It is an object of the present invention to overcome or at least reduce the effects of one or more of the above mentioned problems.

In one embodiment, the present invention provides a bistable switch. The switch includes the following elements: a substrate with at least one power source; a flexible piece with a first distal end fixed to the substrate; a bridge contact formed on a second and opposite end of the flexible piece. at the distal end; and at least one thermally actuated element connected to a first surface of the bendable sheet and between the second distal end and a power supply, wherein current from the power supply through the thermally actuated element indirectly bends the bendable sheet, And short-circuit the signal contacts on the substrate by means of a sustainable force.

Another embodiment of the present invention provides a process for fabricating a bistable switch for a substrate with signal line contacts and a power supply. Specifically, the process includes providing a bendable sheet; connecting at least one thermally actuable element between a first distal end of the bendable sheet and a power source; forming a conductive bridge at the first distal end of the bendable sheet contacts; and mounting a second and opposite distal end of the flexible sheet to the substrate, wherein current from the power source through the thermally actuated element indirectly bends the flexible sheet and shorts the signal contacts on the substrate.

The inventive structure provides a simpler and cheaper method of producing bistable switches with performance values not achievable by means of current solid state methods using standard semiconductor building blocks - transistors. This new and innovative microfabrication method of constructing microswitches enables users to build systems capable of carrying very high voltage, current and frequency signals. This is possible because a microswitch is conceptually equivalent to a tiny relay. In fact, the microswitch is a mechanical microstructure that moves to connect or disconnect conductive contacts. Additionally, this structure and method is compatible with standard silicon processing, allowing mass production at reasonable cost.

Other aspects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the accompanying drawings, in which:

Fig. 1 shows the perspective view of a kind of bistable switch according to one embodiment of the present invention;

Figure 2 shows the general schematic layout of the inventive bistable switch of Figure 1;

3A and 3B-5A and 5B illustrate a process for making the bistable switch of FIG. 1;

Figures 6A and 6B illustrate an arm portion used to manufacture the bistable switch of Figure 1 to include a crimp;

Figures 7A and 7B show the bistable switch of Figure 6A mounted and actuated to indicate a first and a second switch position;

Figure 8 illustrates an alternative embodiment of the bistable switch of Figure 1 comprising a plurality of bridge contacts; and

9A and 9B illustrate yet another embodiment of the inventive bistable switch.

While the invention is susceptible to various modifications in alternative forms, specific embodiments thereof have been shown by way of example in the drawings and described in detail herein. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, Equivalents, and Alternative Examples.

The present invention exploits the properties of shape memory alloys by means of recent advances in micromachining to develop a highly efficient, effective and highly reliable microswitch. The use of SMAs in micro switches increases the performance of switches or relays by orders of magnitude. Specifically, this is achieved because the stress and strain of the shape memory effect can be very large, providing a significant work output per unit volume. Therefore, micromechanical switches using SMA as the actuating mechanism can apply stresses of several hundred megapascals; tolerate strains greater than three percent; operate at common TTL voltages that are much lower than electrostatic or PZO requirements; The electrical leads on the power supply are directly powered; and can withstand millions of cycles without fatigue.

Shape memory alloys undergo a temperature-dependent phase transition initiated at temperatures above _TA , which is characterized by the ability of the alloy to recover any initial shape when the alloy is heated above temperature _TA and below _TH , whereas at temperatures below The mechanical deformation exerted on the alloy at the temperature T _A is irrelevant. In operation, when the SMA material is at a temperature _{TL lower than the temperature TA ,} the SMA possesses a specific crystal structure whereby the material is ductile and can be deformed relatively easily into arbitrary shapes. When the SMA is heated to a temperature _TH higher than the temperature _TA , the crystal structure changes to restore the SMA to its original undeformed shape, restoring the original given shape, thereby representing the onset of recovery stress. Therefore, the transition temperature range of the shape memory alloy on which the phase transformation occurs is defined to be between _TH and _TA . The SMA optimally deforms between 2 and 8% at temperatures below _TA , which deformation fully recovers when the SMA is heated to between _TA and _TH . An optimum deformation is 4%.

These memory materials have been mainly produced in bulk form in the shape of wires, rods, and plates. The most common and readily available shape memory alloy is Nitinol (nickel-titanium intermetallic compound) - an alloy of nickel and titanium. However, other SMAs include copper zinc aluminum, or copper aluminum nickel. For temperature changes as small as 18°C, Nitinol is able to pass through its phase transition and exert a very large force while exerting resistance against changing its shape. As discussed earlier, conventional switches and relays using shape memory alloys generally operate on the principle of deforming the shape of the shape memory alloy while it is below the phase transition humidity range. Heating the deformed alloy above its transformation humidity range restores all or part of the deformation, and movement of the alloy moves the necessary mechanical elements.

Turning now to the drawings, Figure 1 illustrates a thermally actuated bistable micromechanical switch 10 in accordance with one embodiment of the present invention. The actuator arm 12 of the switch 10 is micromachined and secured to an upper substrate surface 14 . Substrate 14 can comprise a silicon-on-insulator or gallium arsenide substrate, a printed _circuit board, a flat plate of ceramic material such as high-density alumina ( _Al2O3 ) or beryllium oxide (BeO), or a substrate such as Glass materials such as fused silica. However, one of ordinary skill in the art will recognize that the switch of the present invention is not so limited, and thus can be mounted to almost any stable structure to provide the desired cantilevered bistable switch.

The upper surface 14 provides control contacts 16 a , 16 b and a ground contact 18 for reliable interconnection to corresponding control and ground contacts of the arm 12 . In addition, upper substrate surface 14 provides signal contacts 20 a and 20 b that are bridged or shorted by conductive bridge contacts 22 of arms 12 . Signal contacts 20a and 20b may transmit or support any electrical signal, including, for example, conventional analog or digital data, or audio signals.

Top and bottom conductive path elements 24a and 24b are coupled to arm 12 by conventional techniques, and two SMA elements 26a and 26b are mounted between contacts and ground vias on the top and bottom center beams of arm 12 . In one embodiment, SMA elements 26a and 26b are made of titanium nickel alloy wire having a diameter between about 25 and 125 microns.

During operation, the above inventive switch provides the basic circuit structure illustrated in FIG. 2 . Specifically, when relay 30a is closed and relay 30b is open, current flow through the top conductive horseshoe path formed by elements 16a, 24a, 26a, and 18 will move arm 12 upward. Conversely, when relay 30a is open and relay 30b is closed, current flow through the bottom conductive horseshoe path formed by elements 16b, 24b, 26b, and 18 will move arm 12 downward. The forces present during the thermal cooling phase are much smaller than those present when heating the SMA element. In other words, the conductive means described in detail below transfers the necessary power from either control contact 16a or 16b to ground contact element 18 via conductive path element 24a or 24b and SMA element 26a or 26b respectively. For the following embodiments, the SMA element 26a or 26b preferably has a diameter between about 25 and 125 microns and is capable of supplying 40 to 160 mA during operation.

Referring now to Figures 3A-3B to 6A-6B, the fabrication process used to construct the bistable switch according to the present invention is as follows. Specifically, Figures 3A, 4A, 5A and 6A illustrate the bottom surface of switch 10, while Figures 3B, 4B, 5B and 6B illustrate side views of the same figures.

3A and 3B illustrate a stabilizing material 50 coated with a layer 52 of patterned photoresist. In this particular embodiment, stabilizing material 50 is a beryllium copper alloy fabricated from rolled sheet stock, having a thickness between about 12 to 50 microns and a width between about 300 to 1,200 microns. However, other materials that provide the desired elastic or bendable properties and thicknesses may be used. For example, a material selected from the group consisting of polymeric resins, plastics, wood composites, silicon, silicone, and various alloy materials such as stainless steel alloys may be used.

In an optimal microfabrication process, a conventional photolithographic technique is used to define the desired pattern on the surface of the stabilizing material 50 (the pattern indicated by the dashed line). Specifically, patterned photoresist 52 defines a three-beam structure having a tail 54 and a head 56, contact vias 58a and 58c, and beams defining beams 62a, 62b, and 62c. Two slots 60a and 60b. A conventional etching technique removes the stabilizing material 50 unprotected by the patterned photoresist 52 to form the triple beam structure 12 illustrated in FIG. 4A.

Those skilled in the art will recognize that it is desirable that the pattern can be formed by other conventional methods. For example, the stabilizing material 50 can be patterned by a conventional stamping or embossing process if the desired switch size is large enough to avoid micromachining techniques.

Next, a non-conductive insulating layer 64 is coated on the top and bottom surfaces of structure 12, as illustrated in FIGS. 4A and 4B. The electrical insulator is preferably a paralene layer. In alternative embodiments, insulating material 64 can be selected from the group consisting of silicon dioxide, polyimide, wet oxide, and silicon nitride layers. These alternatives will provide similar structures with similar operating characteristics. Those skilled in the art will recognize that insulating layer 64 can be eliminated if stabilizing material 50 is a non-conductive material.

On each side of the coated structure 12, a conductive material such as gold is deposited and patterned to create a portion of the desired horseshoe-shaped path. More specifically, the top surface of coating structure 12 (see FIG. 1 ) provides an L-shaped conductive path 24a coupled between control via 58a and the top contact pad. In addition, the same conductive material forms the ground via hole 58c. On the opposite or bottom side of structure 12, coated structure 12 provides another L-shaped conductive path 24b coupled between control contact 68b and bottom contact pad 58b, as illustrated in FIG. 4A. Additionally, the same material forms the control contact 68a, the ground contact 70, and the bridge contact 22. Those skilled in the art will recognize that for conductive paths 24a and 24b, control contacts 68a and 68b, ground contact 70, ground and control vias 58a and 58c, top and bottom contact pads 58b, and bridge contacts The conductive material of 22 can be selected from the group of gold, copper, palladium gold alloy, nickel, silver, aluminum, and various other conductive materials available in the prior art.

Referring to Figures 5A and 5B, an actuator element 26a and 26b is securely coupled to the top and bottom surfaces of the arm 12 between each contact pad and ground via 58c. If desired, an adhesive material (not shown) can be used to couple the actuator elements 26a and 26b to the respective top and bottom arm surfaces. The adhesive material can be from the group consisting of cement, epoxy, lock-on-chip tape, solder, embedding material, polyimide, and mechanical fasteners such as buckles or clips choose. This connection positions each actuator element 26a and 26b on a central portion of the top and bottom surfaces of the intermediate beam 62B to complete the conductive horseshoe-shaped path. Actuator elements 26a and 26b are preferably nickel titanium SMA provided in sheet, ribbon, or wire form. For the above embodiments, SMA elements 26a and 26b preferably have a diameter between about 25 and 125 microns.

As disclosed earlier, SMA elements 26A and 26B extend or contact after an electrical current through the materials reaches a pre-established phase transition temperature. For this particular example, the phase change process will typically occur by one of two methods. A first phase change technique reduces the overall volume of the actuation material and, as a result, the length of the shape memory alloy decreases contacting the stabilization material 12 . In a second phase change technique, the SMA stretches no more than a percentage of 8% before and/or after it is mounted on the stabilizing structure 12 . Upon phase transition, the SMA's length decreases, returning to its original length even more, up to 8 percent, before contacting the stabilizing material12 layer. Depending on the requirements for displacement, contact force, number of cycles, and manufacturing process of the head 12a, the shape memory alloy can be stretched or not stretched.

The final steps of the desirably process include crimping and installing the above structure. Without the crimping step, the above structure can be mounted on a desired substrate to form a reliable microfabricated bistable switch with a cantilever structure as shown in FIG. Likewise, the switch cannot continuously short the signal contacts unless power is active to generate the necessary current and transitions within the desired SMA element. Thus, this final embossing or crimping step will allow the movable device to maintain a contact position even after power-off. This embossing or supercorrugation thus provides the arm with a snap action function which holds the arm in a given position unless one of the SMA elements snaps the arm back into the opposite position.

Referring to Figures 6A and 6B, desired embossing or crimping elements 80A and 80B are shown. This snap action structure can be formed using conventional stamping or dyeing methods. More specifically, the central portions of the left and right beams 62A and 62C are crimped to form a wave-like deformation or a shoe shape. To those skilled in the art, such crimped regions 80A and 80B will generate a sustained force as the actuator elements 26a and 26b transition to move the arm tip 12a upward or downward. Likewise, crimped regions 80A and 80B allow bridge contact 22 to remain in contact with or separate from signal contacts 20a and 20b even after a source coupled to switch 10 is deactivated. In other words, by forming creases 80A and 80B, once arm 12 is positioned up or down, current must be passed through the appropriate SMA elements to bend arm 12 down or up, respectively, to another position. Otherwise, the switch 10 is always positioned up or down unless it is actually moved by the user.

With or without corrugated elements formed on the first and third beams 62A and 62C, the resulting structure must be secured to the substrate 14 as illustrated in FIGS. 7A and 7B or FIG. 1 . Specifically, cantilever switch 10 is attached to substrate surface 14 by conventional adhesive methods. Specifically, solder or pressure grooves of the printed circuit board are used to attach or secure the power and ground contacts 16 a , 16 b , and 18 to the substrate surface 14 of the switch 10 . Thus, when actuating element 26b is heated by the bottom horseshoe-shaped conductive path, the resulting structure will bend downward to couple bridge contact 22 with signal contacts 20a and 20b. Likewise, when actuating element 26A is heated by the top horseshoe-shaped conductive path, the connection between bridge contact 22 and signal contacts 20a and 20b will be broken.

Another embodiment of the present invention includes placing an auxiliary contact 22' on the top surface of end 12a to short circuit auxiliary signal contacts 20a', 20b' on a multilayer substrate. For the example illustrated in FIG. 8, if the top SMA element 26a is heated by current through the top horseshoe-shaped conductive path, the structure will move upwards to align the top bridge contact 22' with the top signal contacts 20a', 20b'. connect. On the other hand, if actuator element 26B is heated by current through bottom horseshoe shaped conductive paths 24b and 26b, the structure will move downwards to couple bridge contact 22 with signal contacts 20a and 20b. For this particular embodiment, the arms 12 are not crimped. Thus, the bridge contacts 22 or 22' can only continuously short-circuit the signal contacts 20a, 20b or 20a', 20b' while heating the respective SMA 26a or 26b to move the tip 12a up or down. However, those skilled in the art will recognize that crimping can be used to maintain arm 12 in contact with one or the other of contacts 20a and 20b or 20a' and 20b'.

Figures 9A and 9B illustrate another embodiment of the above inventive switch. In this embodiment, the sheet 50 is patterned and etched or stamped to form the desired arm 12, as described above with reference to Figure 3B, and the bridge contact 22 is formed (as described above) on the arm end 12a. Second, the central portion of the actuator element 60 is looped or secured to the arm 12 at a location adjacent the end 12a and is electrically separated from the bridge contact 22 . Finally, the tail portion 54 of the arm 12 is secured to the substrate surface 14, and the ends 62a and 62b of the actuator element 60 extend in horizontally opposite directions adjacent the length of the arm 12 so as to be parallel to the same substrate surface 14. An adjacent power supply 64 is connected. In other words, the conductive L-shaped path and contacts previously disposed on arm 12 to provide the necessary circuitry to actuate the SMA element (see FIG. 1 ) have been moved to a position away from switch arm 12 to provide power 64 .

Referring now to FIG. 9B, during operation, current supplied to SMA 60 by source 62 contacts SMA 60 to move arm 12 downward and short circuit signal contacts 20a and 20b to bridge contact 22. As described in the above disclosure, with power supply 62 de-energized, SMA 60 will return to a position that separates bridge contact 22 from signal contacts 20a and 20b. Those skilled in the art will recognize that another SMA (not shown) may be secured to arm 12 in a similar manner, but on the opposite side to SMA 60, and supplied with current by a similar power supply. Likewise, the arms 12 can be crimped to form a device that functions as described above with reference to Figures 7A and 7B, and the arms 12 can be formed into patterns with or without multiple parallel beams. For this particular embodiment, if there is no beam on the arm 12 and an additional SMA element is secured to or wrapped around the other side of the arm 12, a single embossment or full surface crimp can be used.

With respect to the above embodiments, those skilled in the art will recognize that the arms 12 can be patterned to form a multi-beam structure with any desired SMA elements necessary to hold them. Likewise, the arms 12 can be patterned to form only rectangular structures without beams. With similar cues, the thickness and number of SMA elements 26a and 26b can be increased or decreased to accommodate the desired arm configuration and the forces necessary to move it when heated. Additionally, the number of creases formed on the bendable arm 12 will depend on the shape and functional characteristics of the resulting switch.

In summary, the present invention provides a simpler and less expensive method of producing microswitches and relays. This new and innovative micromachining method of constructing microswitches and relays enables users to build systems capable of transmitting very high voltage, current, and frequency signals. Additionally, the inventive process can conceptually be designed to be compatible with standard silicon processing and allow devices to be mass-produced at very reasonable cost. Thus, the inventive structure provides a small bistable snap action electromechanical switch that can be actuated from a shape memory alloy possessing a unique ability for increased velocity actuation and force relative to any prior art switch mechanism. move. In addition, because of advances in micromachining, the structure can be produced to have a length similar to that between 500-3,000 microns, a width between about 200-1,200 microns, and a thickness between about 25-36 microns, which is smaller than in any competing bistable switch on the market today. Those skilled in the art will recognize that these dimensions can be varied to obtain the desired dimensions and functional properties for the inventive switch.

Other design changes that still fall within the scope of the inventive concepts claimed herein will be apparent to those skilled in the art. For example, the illustrative embodiments described herein use the SMA elements 26a and 26b as portions of the conductive path used to heat the SMA elements for the same purpose. For example, SMA elements could be coupled to separate conductive elements, or they could be coupled to an entirely different kind of heating element (eg, non-electrical).

Illustrative embodiments of the present invention are described above. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be understood that in the development of any such actual embodiment, various implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which vary from implementation to implementation. Moreover, it will be recognized that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those skilled in the art having the benefit of this disclosure.

Claims (32)

1. A process for fabricating a bistable switch comprising: Provide a bendable sheet; patterning the sheet to define a beam structure having an end region and an aft region and a front side and a rear side; forming a first control contact adjacent to said flexible sheet tail region; coupling an actuator element to the front side of the beam; forming a conductive path between said control contact and a first end of said actuator element adjacent to said end region of said bendable sheet; forming a second control contact at a second end of said actuator element adjacent said flexible sheet tail region; forming a bridge contact at the first distal end of the flexible sheet end region; and Mounting a portion of the flexible sheet tail region to a substrate to couple the first and second control contacts to a power supply of the substrate, the bridge contact being connected to at least one signal contact Adjacent and separated from it. 2. The process of claim 1, further comprising crimping the beam structure to statically bias the bridge contact to maintain its position relative to the at least one signal contact. 3. The process of claim 1, wherein coupling further comprises bonding said actuator element first and second ends between said first and second control contacts. 4. The process of claim 1, further comprising applying an insulating layer to said flexible sheet after said patterning step. 5. The process of claim 4, wherein the insulating layer is selected from the group consisting of polyimide, silicon dioxide, silicon nitride, wet oxide, and paralene. 6. The process of claim 1, wherein the bendable sheet is selected from the group consisting of polymeric resin, plastic, wood composite, silicon, silicone, stainless steel, and beryllium copper. 7. The process of claim 1, wherein forming a pattern further comprises: applying a photolithographic mask to the sheet; and The mask sheet is etched to define the multiple parallel beam structure. 8. The process of claim 7, wherein etching further comprises etching the flexible sheet to define vias in a central portion of the control and ground contacts. 9. The process of claim 1, wherein forming a pattern further comprises stamping or embossing the bendable sheet to define the multiple parallel beam structure. 10. The process of claim 1, wherein coupling further comprises depositing an adhesive material between the actuator element and the sheet. 11. The process of claim 10, wherein the adhesive material is selected from the group consisting of polyimide, lock-on-chip tape, cement, solder, epoxy, and mechanical attachment group selection. 12. The process of claim 1, wherein the actuator material is a shape memory alloy. 13. The process of claim 12, wherein the shape memory alloy is selected from the group consisting of nickel titanium, copper zinc aluminum, and copper aluminum nickel. 14. The process of claim 1, wherein the conductive path, bridge contacts, and control contacts are selected from the group consisting of gold, copper, palladium-gold alloy, nickel, silver, and aluminum. material. 15. The process of claim 12, wherein the shape memory alloy is a wire having a diameter between about 25 and 125 microns. 16. The process of claim 1, wherein the mounting defines a cantilever bistable switch structure. 17. The process of claim 1, further comprising: forming auxiliary control contacts on the rear side of the beam structure; coupling a second actuation element to the rear side of the beam; and A conductive path is formed between the auxiliary control contact and the second actuator on the rear side of the beam structure. 18. The process of claim 17, further comprising forming at least one via electrically connecting corresponding control contacts on opposite sides of the bendable pattern sheet. 19. The process of claim 1, wherein the substrate further comprises a silicon-on-insulator or gallium arsenide substrate, a printed circuit board, a material such as high-density aluminum oxide (Al ₂ O ₃ ) or beryllium oxide (BeO ), or a structure selected from the group consisting of a flat plate of ceramic material such as fused silica. 20. A process for fabricating a bistable switch for a substrate with signal contacts and a power supply, comprising: Provide a bendable sheet; connecting at least one thermally actuated element between a first distal end of said flexible sheet and a power source; forming a conductive bridge contact at said first distal end of said bendable sheet; and A second and opposite distal end of the bendable sheet is mounted to the substrate, wherein current from a power source through the thermally actuated element indirectly bends the bendable sheet and shorts signal contacts on the substrate. 21. The process of claim 20, wherein providing a bendable sheet further comprises forming at least three parallel beams within the bendable sheet contained by the bridge contacts and the second distal end. 22. The process of claim 21, further comprising crimping the bendable sheet to define a first and second distance between the bridge contact and a power source. 23. The process of claim 21 , further comprising forming a contact pad on said flexible sheet adjacent to or laterally spaced from said bridge contact for connecting said at least one thermally actuated element, The contact pad is adjacent to a central beam of the at least three parallel beams. 24. A bistable switch comprising: a substrate with at least one power supply; a bendable sheet with a first distal end secured to said substrate; a bridge contact formed at a second and opposite distal end of said flexible sheet; and at least one thermally actuated element attached to a first surface of the bendable sheet and between the second distal end and the power source, wherein current from the power source through the thermally actuated element indirectly bends the said flexible sheet and short-circuits said signal contacts on said substrate by means of a sustainable force. 25. The bistable switch of claim 24, wherein the power supply supplies a current of between about 40 and 160 milliamperes. 26. The bistable switch of claim 24, further comprising a crimp positioned at a central region of said bendable sheet. 27. The bistable switch of claim 26, wherein said buckling allows said sustainable force to be maintained even after said power source is de-energized. 28. The bistable switch of claim 24, wherein the thickness of the bendable sheet is between about 12 and 50 microns. 29. The bistable switch of claim 24, further comprising a second end connected to a second and opposite surface of said flexible sheet and between said second distal end and a second power source. A thermally actuated element wherein current from a power source through said thermally actuated element indirectly bends said bendable sheet and short-circuits said signal contacts on said substrate by means of a sustainable force. 30. The bistable switch of claim 24, further comprising a crimp positioned at a central region of said bendable sheet. 31. The bistable switch of claim 30, said crimp allowing said sustainable force to be maintained even after said power source is de-energized, or until said second thermally actuated element is actuated. 32. A process for fabricating a bistable switch comprising: Provide a bendable sheet; forming at least one control contact adjacent a first distal end portion of the sheet; forming a bridge contact adjacent a second and opposite distal end portion of the sheet; forming a fixed contact adjacent to and laterally spaced from said second distal portion; coupling an actuator material between said at least one control contact and said stationary element; and The first distal portion is mounted to a substrate with a power and signal contact, wherein the bridge contact is adjacent to and laterally spaced from the signal contact.

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