Abstract:
A micro assembly having a substrate and an operating plane coupled to the substrate. The operating plane is movable from an in-plane position to an out-of-plane position. One or more electric connections provide electric power from the substrate to the operating plane in the out-of-plane position. A tool is coupled to the operating plane. The tool is operable to receive electric power from the operating plane to perform work.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims priority under 35 USC §119(e) to U.S. patent application Ser. No. 13/406,454, filed on Feb. 27, 2012, and to be issued as U.S. Pat. No. 8,689,899; which claims priority under 35 USC §119(e) to Ser. No. 12/470,471, filed on May 21, 2019, and now issued as U.S. Pat. No. 8,122,973 on Feb. 28, 2012; which claims priority under 35 USC §119(e) to 61/055,038, filed on May 21, 2009, the entire contents of all and which are hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to Micro Electro Mechanical Systems (MEMS), and more particularly to a three dimensional (3D) MEMS arm and system. 
       BACKGROUND 
       [0003]    Micro ElectroMechanical Systems (MEMS) integrate mechanical elements, sensors, actuators, and/or electronics on a common silicon substrate through micro fabrication technology. The electronics are often fabricated using integrated circuit (IC) process sequences. The micromechanical components are often fabricated using compatible micromachining processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices. 
         [0004]    MEMS devices generally range in size from a micrometer (a millionth of a meter) to a millimeter (thousandth of a meter). Common applications include: inkjet printers that use piezoelectrics or bubble ejection to deposit ink on paper, accelerometers in cars for airbag deployment in collisions, gyroscopes in cars to detect yaw and deploy a roll over bar or trigger dynamic stability control, pressure sensors for car tire pressure, disposable blood pressure sensors, displays based on digital light processing (DLP) technology that has on a chip surface several hundred thousand micro mirrors and optical switching technology for data communications. 
       SUMMARY 
       [0005]    A micro assembly have a substrate and an operating plane coupled to the substrate. The operating arm is movable from an in-plane position to an out-of-plane position. One or more electric connections provide electric power from the substrate to the operating plane in the out-of-plane position. A tool is coupled to the operating plane. The tool is operable to receive electric power from the operating plane to perform work. 
         [0006]    The tool may be, for example, pliers, cutting tool. extension device, hot knife, magnetic bead implanter gun, and biopsy tool. Thus, the micro assembly may perform specific functions in three dimensions, such as reaching above and beyond the plane of the chip in order to do work or to obtain and retrieve tangible objects for analysis. 
         [0007]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  illustrates one embodiment of a MEMS device in accordance with the present disclosure; 
           [0009]      FIGS. 2A-F  illustrate force information for the MEMS device; 
           [0010]      FIG. 3  illustrates one embodiment of an electrical wire in the MEMS device; 
           [0011]      FIG. 4  illustrates one embodiment of rotation geometry; 
           [0012]      FIG. 5  illustrates further details of the bond pads in accordance with one embodiment; 
           [0013]      FIGS. 6A-C  illustrate one embodiment of the shark-jaws; 
           [0014]      FIGS. 7A-C  illustrate one embodiment of a magnetic bead implanter gun and cell breaking points; 
           [0015]      FIG. 8  illustrates one embodiment of micropliers; 
           [0016]      FIG. 9  illustrates one embodiment of a cutting tool; 
           [0017]      FIG. 10  illustrates one embodiment of a biopsy tool; 
           [0018]      FIGS. 11A-D  illustrate a cauterizing tool; and 
           [0019]      FIGS. 12-49  illustrate further details of the MEMS device, including various tools and applications, and fabrication of the device. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  illustrates one embodiment of 3D MEMS device that operates at significant elevation levels (greater than lmm) and performs activities. The device contains an arm that raises into a position orthogonal to the chip, allowing one of several different tools to come into contact with the space above the chip. Potential tools operated by the device could include one of any number of different mechanical devices: measuring tools, tools suitable for medical applications such as biopsies, etc. 
         [0021]    The device has three major components. First, using on-chip actuation, this design automatically rotates a structure with sizable length (e.g., mm) to a vertical position that is orthogonal to the plane of the chip. Second, the device is designed to provide electrical power (insulated hot and ground leads) to the top of the vertical structure once it is upright. Third, at the top of the vertical structure which rises significantly above the substrate, it provides real estate space for micro-tools that move and perform work. The micro-tool has a telescopic accordion-like arm with the ability to reach up and grab something over 300 μm above the top of the elevated structure which is about 1.5 mm above the substrate of the chip. In summary, the device is the realization of several features including, for example, automatic 90 degrees rotation of released MEMS structures into vertical orientations, electrical power supplied up through the elevated structure, and micro-tool work and movement at the top of the elevated structure. Applications include nanotechnology, biomedical, micro-manufacturing, micro-fluidics, and micro-sensors. Applications include reaching up above chip to perform tasks, reaching out off chip to perform tasks and providing power and/or power leads out of plane. Other applications include medical applications including: micro-surgery, cut or grab a micro-hunk of tissue, micro-surgical tool, monitoring of bodily functions from inside the body on the micro scale, collecting data or samples on the micro scale, fertilized egg turner. Micro-tooling applications include micro-sensing, measuring micro distances, using MEMS robot to construct other micro-structures, and using MEMS robot to repair objects on the micro scale grabber, extension arm, micro cutter and micro activator. 
         [0022]    The device contains an arm that raises into a position orthogonal to the chip, allowing one of several different tools to come into contact with the space above the chip. Electrical contacts may extend between the out-of-plane platforms and the in-plane platform. The different tools allow the device to become one of any number of different mechanical devices: a measuring tool, a cutter, a grabber, a manipulator, or a specialized tool designed to complete a specific task. 
         [0023]    The geometry of MEMS devices creates a product that is, in effect, a two and half dimensional object. Therefore, having the ability to raise part of the device and interact in the third dimension will give MEMS devices new and progressive 3-D abilities. There are numerous potential applications, including interaction with a second chip in a flip-chip or other system or allowing the raised chip to interact on a new level within its working environment. While structure can be raised up manually (e.g., probe tip actuation), the device, using on-chip actuation, will erect itself into a vertical orientation using its own means. In addition, electrical power will run up the vertical structure in order to run the micro-tools at the end of the operating plane. The 3-D micro-robot may perform micro-tasks in the 1 mm to 2 mm range distances above the surface of the chip. The 3-D micro-robot may perform micro-tasks in the 1 mm to 2 mm range distances off the edge of the chip. The 3-D micro-robot may perform micro-tasks using electrical energy in the 3 to 50 volts range with current less than 1.0 milliamp. Designs may fit within the standard 2820μ×6340μ module chip size. 
         [0024]    Referring to  FIG. 1 , the device includes ground lead  1 , provides a ground for the tools on the top of the operating plane. Hot lead  2  includes three hot leads. One hot lead is provided for every thermal actuator required to do a function (i.e. extend the arm, close the grabber, etc.). These leads connect into the encased oxide (garage) portions of the operating plane. Thermal actuators with jacking system  3  uses teeth to incrementally move the jacking system forward. Pin and cross system  4  uses a set of angled cross bars that when drawn forward, apply a force on a set of pins orthogonally attached to the axle of the operating place. This results in a torque on the axle which causes the operating plane to rate 90°. There are three cross members on each side of the rotating axle with 15° between the two cross members. Thermal actuators and latches  5  keep the operating plane secure while it is not being elevated. Operating plane  6  is the main body that is being elevated. The circles are the pores in the operating place. They allow etching trough to the substrate layer which will release the operating plane  6  from the surface of the chip. In operating plane  6  contains a series of structures of encased oxide (garages) that will allow P 3  to be insulated and serve as the hot lead for the tool  9  . Tool connection  7  connects to the tool  9  to provide rigidity, and this is also where the thermal actuator connects for its ground. Thermal actuator for tool  8  may be a smaller thermal actuator than the others, so it can fit on the top of the operating plane. It contains a jacking system to allow the tool to reach its full extension. Tool  9  may be the scissor action extension arm or other tool option. 
         [0025]    In regard to the thermally actuated jack lift system  3 , the operating plane  6  is to be raised 90 degrees by the thermally actuated jacking system  3 . The jack itself is simply a thermal actuator with a ratcheting centerpiece designed to incrementally drive a series of cross member components. Each actuation motion travels about 10 μm, and the ratchet teeth are each separated by 4 μm. This means that each actuation pushes the cross members two teeth, or 8 μm. 
         [0026]    The cross member components are designed to translate the force provided by the thermal actuators in order to put a torque on the operating plane pivot axle. Pins that are fixed perpendicularly to the axle are guided by the cross members along a path that is 15 degrees off of the axis. This allows the torque to incrementally raise the operating plane  6  to a position orthogonal to the MEMS chip. The total distance that the cross member components need to travel is 18 μm. This means that 2.25 actuations are required to reach 90 degrees. There are a total of 6 cross member components; a larger number of cross members reduces the force required for the thermal actuators to achieve plane rotation. Mathematical proofs of  FIG. 2  illustrate the key force information for the MEMS system. 
         [0027]    In regard to the operating plane latch system  5 , during the release phase of the SUMMiT V fabrication process, there are turbulent forces that can potentially damage a design if the device is not properly secured to the chip. To minimize the potential for damage, a set of thermally actuated latches will he utilized to safeguard the device. Located on either side of the operating plane (i.e. the plane to be raised), the latches will secure the plane to the chip face until it is time to raise the plane. At such time, the latches will be released by activating the thermal actuators, which in turn will free the operating plane from the face of the chip. 
         [0028]    In regard to the operating plane  6 , the operating plane provides stability, electrical current, and be the proper size to give height off the face of the chip. To do this a 1.4795×0.8mm plane designed that is electrically charged and fastened at its base to a torsional lift axle. The plane may have the capacity for up to 6 separate circuits, though the main design requires only 2. The interior of the operating plane  6  is perforated by release pores, to ensure separation of the 3 structural polysilicon layers from the substrate material of the chip. Also on the interior are the ‘hot’ sides of the electrical tool circuits. To do this, polysilicon layer  3  is encapsulated in segmented shafts that run the length of the plane. The shafts are long shells constructed using polysilicon layers  1 ,  2 ,  3 , and  4  (also referred to as P 1 , polyl, etc.). Layers  1 l and  2  serve as the bottom faces of the shell, layer  4  serves as the top face, and layer  3  serves as the side rails. A single strand of polysilicon layer  3  is separated from the shell by the encased oxide and will run the length of the shaft. In effect, electrical ‘wires’ have been created that enable current to be carried to the tool mounted at the top of the operating plane. See  FIG. 3 . Along the side edges of the operating plane  6  run segments that act as grounds for the electrical circuits. 
         [0029]    In regard to leads  1  and  2 , the purpose of the leads is to bring power to the plate when it is raised to 90 degrees. To accomplish this, 3 hot leads and three ground leads are provided that, when the plate is in place, will connect to the leads which run through the core of the plate. Before the plate can be raised these leads need to be pulled out of the way to clear the path of motion. The geometry for this rotation is illustrated in  FIG. 4 . 
         [0030]    Electrostatic forces are used to accomplish this. By running a lead along the base plate that is next to, but not directly beneath, the main leads, a conductor can be used on top of each beam to pull it down without letting it touch the conductor. This prevents a short circuit that would cause the beam to release back to its original position. During the raising of the plate both the ground and hot leads will be bent out of the way to allow the plate to pass. Once the plate passes, the leads will be released and allowed to contact the bottom of the elevated plan thus completing the circuit. This is will provide power to the top of the plate. To ensure this component will work properly it is necessary to calculate the force developed by the charge field below the beam, so that the proper voltage is passed through the conducting plate. These calculations allow the actual tip displacement of the beam to be estimated using beam theory. From the calculation for one beam, the force needed to lower the beam a distance of 2 μm is 2.241 μN. To generate this force it is necessary to have a charge difference of approximately 35 volts between the plates. This voltage must be somewhat higher in practice due to the number of arms to be lowered and because it is not an ideal situation. After examining the geometry of the plate bottom and its rotation, the minimum amount the leads can be lowered to allow for clearance is 1.89 μm. In order to allow for the plate to shift it is advisable to lower it as far as possible, which will be 2 μm. 
         [0031]    One major area of concern in the original design of the lifting mechanism for the plate was running power up to the top. In fact this was one of our main design objectives. One of the challenges facing the design team was to be able to raise the plate and then connect the power in such a way that the power lines did not interfere with the plate on its way up. To accomplish this the leads were designed as cantilever beams that could be stressed out of the way and allowed to snap back in to position after the plate was raised to its full height. For this application the team chose to use an electrostatic pull down effect on the beams to bend them low enough to gain the clearance required. Using the formulas for beam bending and electromagnetic attraction force between parallel plates, the team was able to derive a method to not only determine the voltage required to “snap down” our current design, but how a redesign could be done to reduce the voltage required and to prevent arcing between the charged plate and the beam being pulled. 
         [0032]    Part of the design takes into account the possibility of a short circuit; this involved placing the actual beam having the electrostatic force applied in the layer above the beam that needed to be cleared of the plate. Thus, the team assured that the beam would not touch any layers. This change in design had major effects on the math model for the electrostatic snap down, because the force that was being applied over an area was being transferred to a non-central non-end point on a different beam. This required the use of the parallel plate force equation and the non-central point beam deflection equation, each using the size and shape of the respective beam. Basic assumption could be made: the beam would act linearly in bending, the cross section would remain uniform, and the electromagnetic field produced by the base charging plate would be uniform. For simplicity sake the force on the beam due to gravitational acceleration was ignored as well. With these assumptions in place the entire equation became a simple algebraic expression with either data values that the design team could set or change as needed, or material constants. From this simple equation the team was able to derive an expression for the voltage required to move the beam a certain maximum distance. Once the maximum distance that the beam can moved has been obtained, work can go into determining the actual distance it would have to travel to clear the rotation of the operating plane. Then those beams could snap back in to place and link up for the required 
         [0033]    In regards to the scissor action extension gripper or other tool  9 , the scissor action extension gripper is located at the end of the operating plane and provides the ability to extend a tool beyond the plane surface. Two gripping jaws, named shark jaws, are attached to the end of the extension system, allowing the device to grasp three-dimensional objects as the system extends. There are a multitude of micro tools  9  that can be affixed to the gripper system (wrenches, sensors, cutters, etc.). 
         [0034]    The scissor action extension gripper is powered by a single thermal actuator, which is connected to a bearing on the jack system  3 . As the thermal actuator is charged and displacement occurs, the bearing is pulled by the thermal actuator. The bearing is connected to a stationary bearing on the jacking system  3  through a series of bearings and beams. The stationary bearing has two functions as the pivot point for the jacking system  3  and as the connection for the struts that hold the jack system  3  in place. To the right of the stationary bearing lies the device that performs the action of extension. It is essentially 3 rows of 5 bearings per row, each connected by a simple beam. As the thermal actuator pulls on the bearing, the angles of the beams decrease, thus causing the beams to extend in the opposite direction of the thermal actuator&#39;s pull. The decreasing angle of the beams thus causes the shark jaws to clasp towards each other. 
         [0035]    The shark jaws have serrated edges in order to minimize the surface contact between the jaws and the object to be grasped. As the contact area between the two surfaces is decreased, the magnitude of Van der Waal&#39;s and stictional forces is decreased, facilitating the release of the object. 
         [0036]    Regarding the bond pads,  FIG. 5  provides details of the bond pads and their applications. 
         [0037]    The device, in the SUMMiTV application, relies on being able to use the interaction of the cross-members in P 1 , P 2 , and P 4  with the bar in P 3  to create rotational movement. Additionally the gripper system uses P 1 , P 2 , and P 4  to make two separate bars with hinge pins that are comprised of P 1 , P 2 , P 3  and P 4 , allowing the bars to rotate and the scissor-jack to expand and contract. 
         [0038]    The Sandia Ultra-planar, Multi-level MEMS Technology 5 (SUMMiT V™) Fabrication Process is a five-layer polycrystalline silicon surface micromachining process (one ground plane/electrical interconnect layer and four mechanical layers). It is a batch fabrication process using conventional IC processing tools. Using this technology, high volume, low-cost production can be achieved. The processing challenges, including topography and film stress, are overcome using methods similar to those used in the SUMMiT V™ Process: topography issues are mitigated by using Chemical-Mechanical Polishing (CMP) to achieve planarization, and stress is maintain at low levels using a propriety process. 
         [0039]    MEMS are also produced in the SUMMiT V™ Fabrication Process by alternately depositing a film, photolithographically patterning the film, and then performing chemical etching. By repeating this process with layers of silicon dioxide and polycrystalline silicon, extremely complex, inter-connected three-dimensional shapes can be formed. The photolithographic patterning is achieved with a series of two-dimensional “masks” that define the patterns to be etched. The SUMMiT V™ process uses 14 individual masks in the process. 
         [0040]    The functionality of the micro-robotic arm lies in its ability to accommodate a wide assortment of tools for a variety of purposes. The tools  9  are detailed below. 
         [0041]      FIG. 6A  illustrates the scissor action extension gripper  20 . It is located at the end of the operating plane and provides the ability to extend a tool beyond the plane surface. Two gripping jaws, named shark jaws, are attached to the end of the extension system, allowing the device to grasp three-dimensional objects as the system extends. There are a multitude of micro tools that can be affixed to the gripper system (wrenches, sensors, cutters, etc.). 
         [0042]    The scissor action extension gripper is powered by a single thermal actuator, which is connected to a bearing on the jack system. As the thermal actuator is charged and displacement occurs, the bearing is pulled by the thermal actuator. The bearing is connected to a stationary bearing on the jacking system through a series of bearings and beams. The stationary bearing has two functions as the pivot point for the jacking system and as the connection for the struts that hold the jack system in place. To the right of the stationary bearing lies the device that performs the action of extension. It is essentially 3 rows of 5 bearings per row, each connected by a simple beam. As the thermal actuator pulls on the bearing, the angles of the beams decrease, thus causing the beams to extend in the opposite direction of the thermal actuator&#39;s pull. The decreasing angle of the beams thus causes the shark jaws to clasp towards each other. 
         [0043]    The shark jaws have serrated edges in order to minimize the surface contact between the jaws and the object to be grasped. As the contact area between the two surfaces is decreased, the magnitude of Van der Waal&#39;s and stictional forces is decreased, facilitating the release of the object. 
         [0044]    The extension distance of the gripper is a function of the thermal actuator&#39;s displacement. A maximum thermal actuator displacement of 15 μm results in a reach distance of 319.41 μm. There is a linear relationship between the displacement of the thermal actuator and how far the gripper reaches into space (see  FIG. 6B ). The relationship can be expressed as: 
         [0000]      Extension=(δ TA )*21.214
 
         [0045]    Where: δ TA —Displacement of the thermal actuator 
         [0046]    The force exerted by the teeth of the shark jaws is dependent on two parameters: the displacement of the thermal actuator, and the location of the contact point between the jaws and the object to be grasped. An object near the end of the shark jaws&#39; grasp will not receive as much force as an object near the joint, or pivot point, of the jaws. This force is dependent on the moment at the pivot point for the jaws. 
         [0000]    
       
         
           
             M 
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         [0047]    Where: δ v —Vertical displacement of the bearings attached to the thermal actuator F TA —Force exerted by the thermal actuator, which is 612.5 μN 
         [0048]    The linear relationship between the displacement of the thermal actuator (δ TA ), and δ v  can be expressed as: δ v =0.1963δ TA +59.611 (see  FIG. 3 ). Using this relationship, the force exerted at the contact point on the jaws can be expressed as: 
         [0000]    
       
         
           
             
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         [0049]    Where: x 0 —Distance from the joint of the jaws to the contact point. 
         [0050]      FIG. 7A and 7B  illustrates a magnetic bead implanter gun  30 . The problem with current magnetic bead technologies is the failure to specifically target an individual cell for sorting purposed. In order to affix magnetic beads to a certain type of cell, the beads are put into solution with the cells and then randomly attract to one another. This can be problematic If the researcher only wants to collect a unique cell out of a group. The magnetic bead implanter gun (MBIG) solves this problem by shooting a single bead into an individual cell, breaking the membrane and becoming Immersed m the cell&#39;s cytoplasmic fluid. 
         [0051]    The magnetic bead is fit into the two circular holes at the end of the MBIG. The holes serve the purpose of holding the magnetic bead in place because the magnetic bead&#39;s diameter is much greater than the holes&#39; diameter. 
         [0052]    Cold finger technology is used in the MBIG to secure the magnetic bead while the operating plane rotates into an orthogonal position. The P 2  and P 4  layers actually hold onto the magnetic bead while the P 3  layer provides the thermal expansion necessary for the MBIG&#39;s deformation. The P 3  layer is attached to the P 4  layer via a small square of Sac-Ox near the end of the gun, and as a current is applied to the P 3  layer it expands and consequentially raises the P 4  layer a distance of several microns. Once expanded, a magnetic bead can be placed between the layers. 
         [0053]    The bead is shot from the MBIG via a ramming rod that is connected to a thermal actuator. When the thermal actuator is activated and physically displaced, this drives the ramming rod into the bead. The ramming rod is in P 3 , so it is necessary for the P 3  layer attached to the body of the gun to thermally expand and rise out of the way so the layers will not collide upon impact. 
         [0054]    The MBIG is designed so that a bead can successfully puncture a cell&#39;s exterior membrane.  FIG. 7C  shows several varieties of single celled organisms and their corresponding pressures needed to break the cell membrane. The salmonella cell has the largest measured breaking pressure with 10.13 MPa, so the MBIG should deliver a bead at a relatively higher pressure. The pressure exerted on the bead can be calculated by dividing the thermal actuator&#39;s exerted force by the area of the ramming rod that impacts the bead, or: 
         [0000]    
       
         
           
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                     612.5 
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                   19.44 
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                   MPa 
                 
               
             
           
         
       
     
         [0055]    Thus, the MBIG delivers an appropriate pressure to break the membrane of a cell. It should also be noted that the cell will not be permanently damaged by this process. Due to the elastic properties of cells, they will actually expand in order to accommodate the newly acquired magnetic bead. Once the magnetic bead is inside the cell, it will be manipulated with an electromagnetic field in order to maneuver the cell-bead pair to a desired location. 
         [0056]      FIG. 8  illustrates micropliers  40 . Due to an enlarged contact surface area, the micropliers are an ideal tool for holding onto large objects. The pliers are driven by a thermal actuator that pulls on a bearing that is connected to a stationary bearing through a series of beams. The stationary bearing serves as the pivot point for the pliers and as the connection for the struts. 
         [0057]      FIG. 9  illustrates cutting tool  50 . The cutting tool was designed to cut an object with its sharp edges. Driven by the same mechanism as the micropliers, the two heads of the tool pull together and pinch a very small contact area. The elongated beams of the cutting tool allow for a greater moment to occur at the pivot point, resulting in a higher force exerted at the contact point. 
         [0058]      FIG. 10  illustrates biopsy tool  60 . The tool was based on the shark jaws tool and thus is very similar in shape and operation. Calculations for extension are the same as those for the shark-jaws tool because it uses an identical scissor jack, thus the maximum thermal actuator displacement of 15 μm results in a reach distance of 319 μm. Although the scissor jack system is the same, the end of the tool operates differently. The basic shape is similar to the shark jaws in order to best fit the compacted scissor jack shape. However instead of a curved meeting of teeth, the biopsy tool  60  features straight edges that come together at one time, instead of rotating through each other. The plates that make up the head of the tool are replaced by a similarly shaped retaining device. This tool head is made by constructing a half-garage for each side of the head, using P 2 , P 3 , P 4 , and the Sac-Ox layers for the walls on three sides, but leaving out the P 3  layer on the interior side so that material can enter into the space between the P 2  and P 4  layers as the two half-garages come together. This material can then be retrieved and examined. 
         [0059]      FIGS. 11A-11D  illustrate the cauterizing tool  70 . There are many aspects of medicine that can benefit from micro scale tools and procedures, for the simple reason that the area of interest is almost always crowded by other sensitive organs and tissue. In order to cause the least amount of damage while affecting repairs it would seem prudent to have the least invasive tool that is capable of doing the job. Preventative care is a particular case that a tool should be able to address. The heart is the center of everything that keeps the human body functioning, and excess protein in the body can and will build up not only In veins and arteries but also on the valves of the heart. Like any well running machine these foreign inclusions will cause wear and tear. These build ups on the heart valves lead to the most frequent cause of strokes to date, the fat on the valves can break off and get pumped through that heart at a high rate of speed then jam itself up in a capillary. The back up pressure caused by this blockage can lead to a stroke. Current procedures to remove the blockages are messy, invasive, and not very reliable. Open heart surgeries, and valve replacement, are the best solutions to remove these fatty deposits. Any procedure that involves cutting the heart open and replacing a piece of it with something artificial is going to be traumatizing, and there is also a fear of the body rejecting the new part. To avoid this type of complication new methods must be developed to battle the unwanted deposits in both the arteries and veins of the body. 
         [0060]    The MEMS micro torch is one such device that addresses the aforementioned problems. For most current high precision cutting operations doctors have used lasers. 
         [0061]    The applications of lasers in the field of medicine have aided the doctors to no end in performing precise surgical cuts and operations, but they still do not address how one reaches inside the heart without resulting in damage. With a MEMS device this could change drastically. Because of its small size and power requirements, a MEMS device would be ideal for mounting onto the front an arthroscope to give surgeons a means of interacting with and manipulating an object in teal time. Aside from the obvious advantage of causing less damage to the patient, this tool would allow for surgery to be performed in areas that are dangerous to reach. For this to be useful a precision device that could reach out above itself and do work is necessary. The same device should also be able to retract and reapproach, giving it the ability to make multiple passes and do many tasks. Because the device is small and batch fabricated, sterilization would not be necessary, simply replacing the tip of the arthroscope with a clean one is sufficient. 
         [0062]    A tool that makes precise, measured cuts is needed for the aforementioned MEMS application. Cuts are normally made with surgical knives, but more recently the cuts are being made by either lasers or heated cutters. Heating something on this scale has proven to be both simple and reliable as evidenced by the thermal actuators. The ability to heat a rod or beam coupled with the ability to reach above the plane results in the building blocks for a micro scale precision cutting torch, but the design needs a way to retract. 
         [0063]    To retract the jacking mechanism once it is elevated a few things must be done. First the teeth that enable the jacking system to work must be released. To accomplish this, an interlinked system involving a thermal actuator and mechanical linkages have been designed. This apparatus did require that the interim of the jacking system in both the actuator and the stationary ratcheting device be redesigned to allow for release of the teeth. Once the redesign was complete the teeth could be pulled back with a single power source, in essence giving the thermally actuated jacking system a reset button. Enabling the system to retract was the first hurdle of the design. To add reliability to the retraction and make it uniform, a spring is attached to the rear of the rod that is being extended, which will apply a spring force and retract the rod more rapidly than simply releasing the ratcheting mechanism. This was added because the device is expected to act not only in a fluid medium, but in any direction necessary, and gravity could not be relied upon to retract the rod. 
         [0064]    For the issue of bring heat to the target area, the decision was made to utilize the same system as the beams in the thermal actuators. Since the desire is for simple heat and not a forced translation, only two side beams are truly needed. But a problem arose in the area of powering these beams. They would be moving out and back many times in even the most rudimentary surgery, and the beams themselves would be stressed constantly. To avoid excess stress on the jacking system and the beams possibly snapping under the cycling stress, the design was modified so that the beams were curved. The curved shapes acts much the same as pre-stressing on a spring, it affords the rod more length to extend without having to actually stretch the beams that are built across it. This will also reduce the required amount of force to extend the base rod in comparison to if the side beams were originally straight. 
         [0065]      FIGS. 12-49  illustrate further information for the MEMS device. 
         [0066]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.