Abstract:
Implementations of the present invention relate to apparatuses, systems, and methods for harvesting mechanical energy from micro-energy sources and converting that energy into electrical energy. Such mechanical energy sources may be from common motions or processes such as the movement of cars or people. A device for the harvesting of such excess energy may utilize a circulation channel in which magnets may induce currents in coils as the magnets follow a continuous path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/002,066, filed May 22, 2014, and entitled “MICRO-ENERGY HARVESTING DEVICE FOR SPACE-LIMITED APPLICATIONS,” and to U.S. Provisional Patent Application No. 61/909,269, filed Nov. 26, 2013, and entitled “FLEXIBLE DEVICES, SYSTEMS, AND METHODS OF HARVESTING ENERGY,” both of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE DISCLOSURE 
       [0002]    1. The Field of the Invention 
         [0003]    Generally, this disclosure relates to converting mechanical energy into electrical energy. More specifically, the present disclosure relates to the harvesting of mechanical energy from common motions or processes by capturing energy normally lost to the surrounding environment. 
         [0004]    2. Background and Relevant Art 
         [0005]    Energy production is relevant to many applications. Many devices in daily life demand electrical energy to operate. Such devices may receive energy from a centralized energy source (i.e. an electrical grid provided by a power company) or from a portable, localized energy source (i.e. a battery, generator, etc.). For example, a portable electronic device, such as a cellular telephone, may utilize a portable energy storage source to provide a remote supply of energy that stores energy from a centralized energy source to provide energy when connected thereto, but the provides electricity to the device as needed when not connected to the centralized energy source. A portable energy storage source may be more compact and therefore more suitable to certain applications. Typically, these portable energy storage sources must be periodically connected to a centralized energy source in order to recharge them and continue supplying energy to electrical devices. 
         [0006]    There are many individual energy sources that could provide the requisite energy to operate such portable electronic devices or to provide energy to recharge such portable energy storage sources. However, many such individual energy sources are not currently utilized for power generation due to the small scale and/or production capacity of the energy source. These individual “micro-energy” sources are commonly mechanical energy sources. For example, such micro-energy sources may be a person walking or running that will generate mechanical energy that is dissipated against the ground, or the movement of automobiles along a road surface that produces repeated mechanical energy that is dissipated in the road. In each case, the energy is produced for a primary purpose of movement, but excess energy is lost to the environment. 
         [0007]    The mechanical energy of such mechanical power sources may be harvested by converting the mechanical energy to electrical energy by means of micro-energy harvesting. For example, the mechanical energy may be converted to electrical energy through electromagnetic conversion. The mechanical energy may be used to move a magnet through the interior of a wire coil and thereby induce a current in a wire. Such an electromagnetic conversion may be applied in a linear motion to create an oscillating magnet and, therefore, magnetic field to charge a battery or supply electricity to operate an electronic device. The oscillating magnet however, is limited by the scale of the source of mechanical energy or scale of the channel in which the magnet may oscillate. For example, to harvest the excess energy of a person walking, the linear motion of the magnet would be limited to a size that could be unobtrusively affixed to the person. While the energy harvesting could be increased to an extent by increasing the power of the magnet, that would typically require increasing the size of the magnet and the size of the wire (to increase the associated magnetic capacity of the coil), and therefore would increase the overall mass of the energy harvesting device and begin to affect movement of person. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0008]    The present disclosure may address one or more of the foregoing or other problems in the art with devices, systems, and methods for manufacturing, installing and using micro-energy harvesting devices. A micro-energy harvesting device according to the present disclosure may include a plurality of chambers and plurality of channels configured to circulate a fluid therebetween. At least one of the channels may be in fluid communication with a circulation channel. The movement of the fluid through the circulation channel may move a plurality of magnetic components interspersed with non-magnetic components. The movement of the plurality of magnetic components past a plurality of conductive coils may convert the mechanical movement into electrical energy. Additionally, the conductive coils may be connected to an energy storage device. 
         [0009]    In other implementations, a micro-energy harvesting device may include a channel configured to be pressurized and a fluid contained with the channel. The channel may be in fluid communication with a chamber that contains a compressible fluid. The fluid may also be configured to move a plurality of magnetic elements through a plurality of electrically conductive coils. The plurality of magnetic components may be spaced apart from each other by a plurality of nonmagnetic components such that the magnetic and nonmagnetic components form an alternating series of magnetic and nonmagnetic components. Additionally, the chamber containing the compressible fluid may be a spiral, or similarly shaped, channel. 
         [0010]    In another implementation, a method for harvesting micro-energy is provided. The method may include providing a micro-energy harvesting device and using that device to receive an input force with the first chamber. The force may then be transmitted to the fluid disposed in the first chamber. The fluid may move from the first chamber through the circulation channel and into the second chamber. When the fluid moves from the first chamber through the circulation channel and into the second chamber, the movement of the fluid may move the plurality of magnetic components. The device may then convert the movement of the plurality of magnetic components into electrical energy. 
         [0011]    Additional features and advantages of exemplary implementations of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of such exemplary implementations. The features and advantages of such implementations may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or may be learned by the practice of such exemplary implementations as set forth hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    In order to describe the manner in which the above-recited and other advantages and features of the invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. For better understanding, the like elements have been designated by like reference numbers throughout the various accompanying figures. While some of the drawings may be schematic representations, at least some of the drawings may be drawn to scale. Understanding that these drawings depict only typical embodiments of the disclosure and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
           [0013]      FIG. 1  illustrates a schematic representation of a microfluidic device for harvesting energy in accordance with at least one embodiment of the present disclosure; 
           [0014]      FIG. 2A  illustrates a schematic representation of a state in a sequence of a magnetic element passing through a coil of a microfluidic device for harvesting energy in accordance with at least one embodiment of the present disclosure; 
           [0015]      FIG. 2B  illustrates a schematic representation of another state in a sequence of a magnetic element passing through a coil of a microfluidic device for harvesting energy in accordance with at least one embodiment of the present disclosure; 
           [0016]      FIG. 2C  illustrates a schematic representation of yet another state in a sequence of a magnetic element passing through a coil of a microfluidic device for harvesting energy in accordance with at least one embodiment of the present disclosure; 
           [0017]      FIG. 2D  illustrates a schematic representation of one other state in a sequence of a magnetic element passing through a coil of a microfluidic device for harvesting energy in accordance with at least one embodiment of the present disclosure; 
           [0018]      FIG. 2E  illustrates a schematic representation of still another state in a sequence of a magnetic element passing through a coil of a microfluidic device for harvesting energy in accordance with at least one embodiment of the present disclosure; 
           [0019]      FIG. 3  illustrates a graph of voltage as a function of time, representative of the voltage generated by the magnetic element passing through the coil at each stage illustrated in the  FIGS. 2A-2E ; 
           [0020]      FIG. 4A  illustrates a top view of a schematic representation of a microfluidic device for harvesting energy in accordance with at least one embodiment of the present disclosure in a state of operation; 
           [0021]      FIG. 4B  illustrates a top view of a schematic representation of the microfluidic device for harvesting energy of  FIG. 4A  in another state of operation; 
           [0022]      FIG. 4C  illustrates a top view of a schematic representation of the microfluidic device for harvesting energy with a self-recovering chamber; 
           [0023]      FIG. 5  illustrates a top view of a schematic representation of the microfluidic device for harvesting energy with a circulation channel for the conversion of mechanical energy to electrical energy; 
           [0024]      FIG. 6  illustrates a top view of a schematic representation of a microfluidic device for harvesting energy with a paddlewheel for the conversion of mechanical energy to electrical energy; 
           [0025]      FIG. 7  illustrates perspective view of a flywheel connected to the microfluidic device of  FIG. 6 ; and 
           [0026]      FIG. 8  illustrates an embodiment of a micro-energy harvesting device having a self-flow-stop mechanism. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    One or more implementations of the present disclosure relate to systems, methods, and devices for harvesting energy by converting mechanical energy into electrical energy. In particular, the mechanical energy can be harvested by converting the movement or operation of another system or object into electrical energy. In some embodiments, the mechanical energy can be harvested from energy expended during the normal motion or operation of devices such as cars, bicycles, or doors, or during activities such as simply walking. In addition, energy can be harvested from the surface over which these objects move, such as roads, sidewalks, or railroad tracks. In other embodiments, energy can be harvested from non-mechanical systems such as tides, waves, or oscillations of structures due to the wind. In still other embodiments, the energy harvesting system can be adapted to accept various forms mechanical energy such as compression or other applications of force. 
         [0028]    In some embodiments, the energy harvesting system converts movements of an object into electrical energy. In particular, the system may be able to transform pressure applied to one section of the system into electrical energy. For example, the system may be able to receive input forces and use them to move magnets or magnetic components through or past a series of coils and induce a current therein. As will be used herein, the term “coil” refers to a plurality of loops of wire or other electrically conductive material. 
         [0029]    In one embodiment, the system may receive forces and transmit those forces to the magnetic components by way of a fluid. Unless otherwise specified, the term “fluid” as used herein refers to a compressible or incompressible fluid that may be in the form of a liquid, semi-liquid, gas, or combinations thereof. As a first chamber compresses, it may force the fluid through a channel, and the fluid may move a magnetic component past or through a coil. The fluid may act on the magnetic components either by a direct pressure, such as when the magnetic component is approximately the same size as the channel through which the fluid is following; through a mechanical linkage, such as fluid rotating an axle, which then moves a magnetic component outside the channel; by another force such as friction, such as when the magnetic component is smaller than the channel through which the fluid flows and is simply carried along by the flow of fluid; or by a combination thereof. 
         [0030]    In some embodiments, the system may be able to amplify or de-amplify the force applied to the system when the force is subsequently applied to the magnetic components. For example, in an embodiment that de-amplifies the force applied to the system, the channel containing the fluid may be connected to a first chamber and the first chamber may be significantly larger than the diameter of the channel. This may allow the system to accept very large input forces and to reduce the pressure from the force when applied to the magnetic components so to not rupture the channels. In addition, such an embodiment would also allow a large chamber to compress very slightly and still move magnets within the channels a significant amount. This may enable several advantages such as moving many magnetic components through or past a coil and inducing a larger current or simply requiring very little compression of the first chamber and thereby rendering the system largely transparent to users, such as when the device is stored within the sole of a shoe. 
         [0031]    However, in such an embodiment, the distance the magnetic components may move through the channel may be limited by the size of the device. For example, in the above described embodiment, the maximum size of the device may be limited by the sole of the shoe. In order to overcome this limitation, a circulation chamber may be used to allow circular motion of the magnetic components such that the magnetic components may continue to move to the full extent the energy from the input force may move them despite the compact size of the device. 
         [0032]    As depicted in  FIG. 1 , an embodiment of a micro-energy harvesting device  100   a  may comprise a channel  110  providing fluid communication between a first chamber  120  and a second chamber  130 . A series of a plurality of magnetic components  140  spaced apart from one another by a plurality of nonmagnetic components  150  may be disposed within the channel  110 . In some embodiments, the magnetic components  140  may comprise rare earth magnets. In other embodiments, the magnetic components  140  may comprise neodymium. The alternating magnetic and nonmagnetic components  140 ,  150  may induce a current as they pass through or near a one or more coils  160 , wherein at least one of the one or more coils may have a first lead  161  and a second lead  162  and may be disposed around an outer surface  163  of the channel  110 . For example, when an input force F 1  is applied to the first chamber  120 , an upper surface of the first chamber  190  may move, increasing the pressure within the first chamber  120  and applying the force F 1  to a fluid  170  and forcing the fluid  170  toward the second chamber  130  via the channel  110 . An upper surface of the second chamber  200  may then rise in accordance with an increase in the volume of the second chamber  130 . 
         [0033]    When the fluid  170  flows through the channel  110 , it may apply a force to the magnetic components  140  and nonmagnetic components  150 . The resulting movement of the magnetic components  140  and nonmagnetic components  150  through the channel  110  may induce a current in the coils  160 , which may flow between the first and second leads  161 ,  162  to provide electrical energy either to power a device or to charge an electrical energy storage source such as a battery by an electrical connection between the first and second leads  161 ,  162  and the terminals of the electrical energy storage device. As mentioned earlier, the force on the magnetic components  140  and nonmagnetic components  150  may be a direct force applied by the fluid  170  on a cross-sectional surface of the magnetic components  140  and nonmagnetic components  150 , or it may be due to friction of the fluid  170  on the magnetic components  140  and nonmagnetic components  150  as the fluid moves past in an annular space  180  within the channel  110 . The magnetic components  140  may have a diameter approximately equal to a diameter of the channel  110 . In another embodiment, the magnetic components  140  and/or nonmagnetic components  150  may have a diameter about 70% of the diameter of the channel  110 . In yet other embodiments, the magnetic components  140  and/or nonmagnetic components  150  may have a diameter between 70% and 100% of the diameter of the channel  110 . 
         [0034]    As described herein, the magnetic components  140  can induce current in the coils  160  as the magnetic components  140  move along the channel  110 . More specifically, as illustrated in  FIGS. 2A-2E  and  3 , the magnetic components  140  can move in the first direction together with the nonmagnetic spacers  150 . As each of the magnetic components  140  passes through a corresponding coil  160 , the movement of the magnetic components  140  inside such coils  160  can induce current in each of such coils  160 .  FIG. 3  illustrates the change in voltage with respect to time, as the magnetic components  140  move through the coil  160 . Particularly, points A, B, C, D, and E illustrate voltage produced by the magnetic components  140  at the different positions along the coils  160 , illustrated in corresponding  FIGS. 2A-2E . 
         [0035]    The power output of the coils  160  can vary depending on the number of windings as well as on the diameter of wire used in the coils  160 . Particularly, as the diameter of the wire is increased, the resistance will increase proportionately and will reduce the overall amount of power output. For example, a 150 μm diameter wire can be used for the coils  160 . Other diameters, which may be greater or smaller than 150 μm, can be used for the coils  160 . Furthermore, the coils  160  may have one or more layers. In some embodiments, a single layer of windings may form the coils  160 . In other embodiments, however, the coils  160  can be formed from multiple layers of windings, which may improve the performance (i.e., increase the power output) of the energy harvesting device. 
         [0036]    Movement of the magnetic components  140  and nonmagnetic components  150  of FIGS.  1  and  2 A-E may be limited by the length of the channel  110  in which they are contained. Furthermore, their motion will be indirectly inhibited because the flow of the fluid  170  is inhibited by the linear nature of the channel  110  providing the fluid communication between the first chamber  120  and the second chamber  130 . 
         [0037]    Referring now to  FIGS. 4A-B , a first chamber  210  and a second chamber  220  may be in fluid communication with one another by a delivery channel  230  and a return channel  240 . It should be noted that the designations of the “first” and “second” chambers are intended for the purposes of illustrating the various embodiments described herein and are not meant to be limiting. Accordingly, as used herein, the terms “first” and “second” chambers are entirely interchangeable. Likewise, the designations of “delivery” and “return” channels are merely illustrative of fluid motion relative to the first and second chambers. As the device is intended to produce a circular behavior, it will be appreciated that the embodiment described herein is symmetrical and functionality is irrespective of a particular orientation. 
         [0038]    The delivery channel  230  may have one or more delivery microvalves  250  disposed therein and configured to allow flow through the delivery channel  230  from the first chamber  210  to the second chamber  220 . The return channel  240  may have one or more return microvalves  260  disposed therein and configured to allow flow through the return channel  240  from the second chamber  220  to the first chamber  210 . The one or more microvalves  250 ,  260  may allow substantially unidirectional flow of a fluid  170  disposed in the system. 
         [0039]    The first chamber  210  and the second chamber  220  may be configured to change volume. For example, a chamber may reduce in volume as force is applied and/or fluid  170  exits the chamber. In another example, a chamber may increase in volume as force is removed and/or fluid  170  enters into the chamber. For example, as shown in  FIG. 4A , when the first chamber  210  is compressed by a first compression force F 1 , fluid  170  moves from the first chamber  210  through the delivery channel  230  into the second chamber  220 , causing the second chamber  220  to increase volume. When the first compression force F 1  on the first chamber  210  is removed, the fluid  170  displaced from the first chamber  210  into the second chamber  220  via the delivery channel  230  may be then motivated from the second chamber  220  back to the first chamber  210  via the return channel  240  by a second compression force F 2  the second chamber  220 , as shown in  FIG. 4B . 
         [0040]    Additionally, the first and second chambers  210 ,  220  may be resilient such that when the first chamber  210  is compressed and the second chamber  220  increases in volume, a removal of the first compression force F 1  from the first chamber  210  may cause the now-distended second chamber  220  to apply a second compressive force F 2  to the fluid  170  contained therein and force the fluid  170  to flow through the return channel  240  and back into the first chamber  210 . Similarly, the first chamber  210  will be compressed until the force upon it is removed. After removal of the first compression force F 1 , the first chamber  210  may expand due to its resiliency, and the expansion may create a region of low pressure within the first chamber  210  and draw fluid  170  in, thereby creating a fully cyclic flow from a single compression of the first chamber. 
         [0041]    The second chamber  130 ,  220  in a micro-energy harvesting device may comprise a self-recovering chamber, such as the spiral chamber  270  shown in  FIG. 4C  with a spring fluid  280  disposed therein. In another embodiment, the self-recovering chamber may comprise an extended channel in a shape other than a spiral. In yet another embodiment, the self-recovering chamber may comprise a spring. 
         [0042]    The spring fluid  280  may be more compressible than the fluid  170  such that when a force is applied to the first chamber  120 ,  210  the reduction in volume of the first chamber  120 ,  210  causes the fluid  170  to flow into the spiral chamber  270  and preferentially compress the spring fluid  280 . In an embodiment, the spring fluid  280  may comprise a compressible liquid. In another embodiment, the spring fluid  280  may comprise a gas. In yet another embodiment, the spring fluid  280  may compress substantially according to Hooke&#39;s Law and spiral chamber  270  may, therefore, substantially behave as a coil spring with respect to the fluid  170  flowing into the spiral chamber  270 . Such spiral chamber  270  and spring fluid  280  may provide greater compliance and durability than a piston- or diaphragm-type chamber, which rely upon the deformation or movement of the structure of the chamber itself. Furthermore, a self-recovering chamber may reduce or eliminate the need for a reciprocal pressure on the second chamber  130 ,  220  in order to return the fluid  170  to the first chamber  120 ,  210 , rendering the energy harvesting device suitable for additional applications. 
         [0043]    A device  100   b  such as depicted in  FIGS. 4A-4C  may only create a cyclic pulse of the fluid  170  through the device  100   b . The device  100   b  will return to an equilibrium point after a net force is applied to either chamber relative to the other. Unfortunately, this device still incorporates the limitations of the embodiment depicted in  FIG. 1 , because the fluid  170  still merely cycles between a first chamber  120 ,  210  and a second chamber  130 ,  220  regardless whether a single channel  110  or a pair of channels (delivery  230  and return  240 ) provide the fluid communication between the chambers. However, by utilizing the delivery channel  230  and the return channel  240  in tandem to motivate a plurality of magnetic components  140  spaced apart from one another by a plurality of nonmagnetic components  150  through a plurality of coils  160 , a more efficient conversion of mechanical energy may be realized. 
         [0044]    As shown in  FIG. 5 , in some embodiments, a circulation channel  290  containing a plurality of magnetic components  140  spaced apart from one another by a plurality of nonmagnetic components  150  may be disposed in fluid communication with the delivery channel  230  and the return channel  240 . In an embodiment, the fluid communication between the flow direction of the fluid  170  in the circulation channel  290  and the fluid  170  in the delivery channel  230  may be substantially tangential. A path of travel for magnetic components  140  and nonmagnetic components  150  disposed within this circulation channel  290  or motivated by the fluid  170  moving therethrough is not limited to the length of the circulation channel  290 , but enables multiple circulations creating an effectively infinite travel path. The delivery channel  230 , return channel  240 , and circulation channel  290  may have a circular cross-section, an ellipsoid cross-section, a rectangular cross-section, any other suitable polygonal cross-section, or combinations thereof. The delivery channel  230 , return channel  240 , and circulation channel  290  may have a cross-section suitable to de-amplify the input force applied to the first chamber  210  or second chamber  220 . In an embodiment, the delivery channel  230 , return channel  240 , and the circulation channel  290  may have cross-sectional dimensions of about 4.5 mm by 4.5 mm. For example, the delivery channel  230 , return channel  240 , and the circulation channel  290  may have a diameter of about 4.5 mm. As mentioned earlier, the magnetic components  140  may have cross-sectional dimensions approximately equal to the cross-sectional dimensions of the delivery channel  230 , return channel  240 , and/or circulation channel  290 . In another embodiment, the magnetic components  140  may have a diameter about 70% of a cross-sectional dimension of the delivery channel  230 , return channel  240 , and/or circulation channel  290 . In yet another embodiment, the magnetic components  140  may have a cross-sectional dimension between 70% and 100% of the diameter of the delivery channel  230 , return channel  240 , and/or circulation channel  290 . 
         [0045]    When the delivery channel  230  is in fluid communication with the circulation channel  290 , the flow of fluid  170  through the delivery channel  230  when the first chamber  210  is compressed may provide an impulse to the magnetic components  140  and nonmagnetic components  150 . As depicted in  FIG. 5 , the magnetic components  140  and nonmagnetic components  150  may be disposed within the circulation channel  290 . The motion of the magnetic components  140  past the coils  160  may induce a current therein, which may be harvested from the device  100   c . In other embodiments, the magnetic components  140 , nonmagnetic components  150 , and coils  160  may be disposed outside the circulation channel  290 , and the magnetic and nonmagnetic components  140 ,  150  may be motivated by the fluid movement within the circulation channel  290 . When the flow of the fluid  170  through the delivery channel  230  stops, the inertia of the magnetic components  140  and nonmagnetic components  150  may cause the magnetic components  140  and nonmagnetic components  150  to continue moving and inducing further current in the coils  160 . 
         [0046]      FIGS. 6 and 7  depict a micro-energy harvesting device  100   d  in which the plurality of magnetic components  140  and nonmagnetic components  150  are disposed outside of the circulation channel  290 . The embodiment may be functionally similar to the micro-energy harvesting device  100   c  depicted in  FIG. 5 , but the fluid  170  acts upon the plurality of magnetic components  140  and nonmagnetic components  150  indirectly. The circulation channel  290  may include a paddlewheel  300  or similar device that may rotate when acted upon by the movement of the fluid  170  through the delivery channel  230  and/or return channel  240 . The cyclic flow from the first chamber  210  to the second chamber  220  and from the second chamber  220  to the first chamber  210  may occur similarly to any of the previously described embodiments. Similar to the magnetic components  140  disposed within the circulation channel  290 , the paddlewheel  300  may have a cross-sectional height approximately equal to the cross sectional area of the circulation channel  290 . In another embodiment, the paddlewheel  300  may have a cross-sectional height approximately 70% of a cross sectional height of the circulation channel  290 . In yet another embodiment, the paddlewheel  300  may have a cross-sectional height between 70% and 100% of a cross sectional height of the circulation channel  290 . 
         [0047]    The substantially unidirectional flow may rotate the paddlewheel  300  that acts upon external magnetic components  310  and external nonmagnetic components  320 . The external magnetic components  310  and external nonmagnetic components  320  may alternate in a similar fashion to the magnetic components  140  and nonmagnetic components  150  described in relation to  FIGS. 1 through 5 . As shown in  FIG. 7 , the external magnetic components  310  and external nonmagnetic components  320  are disposed on a flywheel  330  that is connected to the paddlewheel  300  by an axle  340 . In some embodiments, the axle  340  may include a unidirectional hub (not shown) allowing force to be applied by the paddlewheel  300  to the flywheel  330 , which may continue to rotate freely. In other embodiments, the flywheel  330  may be connected to the paddlewheel  300  through other mechanisms, such as a chain drive, a screw drive, non-mechanical forces such as a magnetic force, or combinations thereof. The flywheel  330  may rotate, and, as it does, move the external magnetic components  310  and external nonmagnetic components  320  past one or more coils (not shown) inducing a current therethrough. 
         [0048]    As shown in  FIG. 7 , the flywheel  330  may comprise alternating sectors of external magnetic components  310  and external nonmagnetic components  320 . In other embodiments, the flywheel  330  may be an external nonmagnetic component  320  with external magnetic components  310  disposed therein. In yet other embodiments, the flywheel  330  may be a ring having external magnetic components  310  and external nonmagnetic components  320  disposed around the perimeter of the ring in an alternating fashion. 
         [0049]    As mentioned earlier, a micro-energy harvest device in accordance with the present disclosure may be functionally symmetrical. Therefore, an equivalent process may occur during compression of the first chamber  210  and a resulting flow of fluid  170  through the delivery channel  230  or the second chamber  220  and a resulting flow of fluid  170  through the return channel  240 . By allowing for a functionally infinite travel path for the magnetic components  140  or external magnetic components  310  in which to induce current in the coils  160 , a circulatory energy harvesting device  100   c ,  100   d  may harvest energy more efficiently and completely than a linear energy harvesting device  100   a  such as shown in  FIG. 1 . 
         [0050]    In addition to a device having first and second chambers such as that described in relation to  FIGS. 1 through 7 , a device may include a self-flow-stop in a channel to prevent over pressurization of the channels.  FIG. 8  depicts a micro-energy harvesting device  100   e  having a self-flow-stop mechanism. A self-flow-stop microvalve  350 , for example, includes a self-flow-stop, such that the self-flow-stop microvalve  350  opens under pressure, but excessive pressure or flowrate closes the microvalve  350 , as illustrated in  FIG. 8 . The closure of the microvalve under excessive pressure or flowrate may prevent damage to the smaller volume channels and localize the high pressure to the chambers which may be more robust in construction. In another embodiment, the flow-stop may occur when the magnetic components  140  have completed a power generation cycle. 
         [0051]    In some embodiments, the self-flow-stop microvalve  350  may include a plurality of members positioned approximately 90° from one another. A first member  360  may be urged into an open position at the fluid  170  moves from the first chamber  210  toward the second chamber  220 . When the first member  360  is urged into a fully open position by high fluid pressures, a second member  370  of the self-flow-stop microvalve  350  may be simultaneously urged into a closed position to limit or prevent over-pressuring of the delivery channel  230 , return channel  240 , and/or circulation channel  290 . In other embodiments, the self-flow-stop microvalve  350  may include a plurality of members positioned greater than 90° from one another. The first member  360  and/or the second member  370  may be resilient. The self-flow-stop microvalve  350  may obstruct but not prevent the flow of fluid  170  when the first member  360  is urged into a fully open position and the second member  370  is, thereby, urged near the delivery channel  230 , return channel  240 , and/or circulation channel  290 . During higher flow rates, the fluid  170  may flex the resilient second member  370  to obstruct the flow more greatly or substantially prevent flow of the fluid  170 . In other embodiments, the first member  360  and second member  370  may have a resilient connection therebetween. A resilient connection may allow the first member  360  and second member  370  to move relative to one another irrespective of the rigidity of the first member  360  and/or second member  370 . 
         [0052]    For example, a self-flow-stop microvalve  350  in the example of a shoe bed, as described herein, may allow the movement of fluid  170  when a user applies a low force during walking activities. The self-flow-stop microvalve  350  may at least partially limit the movement of fluid  170  when the user applies a medium force during running activities. The self-flow-stop microvalve  350  may substantially prevent the movement of fluid  170  when a user applies a high force while jumping or performing other actions that result in high forces to the sole. 
         [0053]    Additionally, a device  100   e  may include a third chamber or channel to relieve pressure in the system. The third chamber may be a self-recovering chamber, such as an extended channel, a spring, or a spiral chamber  270  similar to that described in relation to  FIG. 4C . The spiral chamber  270  may include a spring fluid  280  therein that may substantially behave as a coil spring with respect to the fluid  170  flowing into the spiral chamber  270 . The spring fluid  280  may dissipate energy from over-pressurization with less deformation to the structure of the device  100   e . Lessening deformation of the device  100   e  may reduce wear on the device  100   e  and/or increase operational lifetime. 
         [0054]    For example, a self-recovering chamber may facilitate dissipation of large input forces over a longer channel and, therefore, surface area. The larger surface area may reduce the pressure in the device sufficiently to prevent rupturing of the channel or of a chamber. A self-recovering chamber disposed in fluid communication with the device but in addition to the first and second chambers may operate as a pressure-release channel, allowing flow into the self-recovering chamber when a pressure in the device exceeds a predetermined amount based on the volume, thickness, and material of the device. 
         [0055]    The articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements in the preceding descriptions. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. For example, any element described in relation to an embodiment herein may be combinable with any element of any other embodiment described herein. Numbers, percentages, ratios, or other values stated herein are intended to include that value, and also other values that are “about” or “approximately” the stated value, as would be appreciated by one of ordinary skill in the art encompassed by embodiments of the present disclosure. A stated value should therefore be interpreted broadly enough to encompass values that are at least close enough to the stated value to perform a desired function or achieve a desired result. The stated values include at least the variation to be expected in a suitable manufacturing or production process, and may include values that are within 5%, within 1%, within 0.1%, or within 0.01% of a stated value. 
         [0056]    A person having ordinary skill in the art should realize in view of the present disclosure that equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations may be made to embodiments disclosed herein without departing from the spirit and scope of the present disclosure. Equivalent constructions, including functional “means-plus-function” clauses are intended to cover the structures described herein as performing the recited function, including both structural equivalents that operate in the same manner, and equivalent structures that provide the same function. It is the express intention of the applicant not to invoke means-plus-function or other functional claiming for any claim except for those in which the words ‘means for’ appear together with an associated function. Each addition, deletion, and modification to the embodiments that falls within the meaning and scope of the claims is to be embraced by the claims. 
         [0057]    The terms “approximately,” “about,” and “substantially” as used herein represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” and “substantially” may refer to an amount that is within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of a stated amount. Further, it should be understood that any directions or reference frames in the preceding description are merely relative directions or movements. 
         [0058]    The present disclosure may be embodied in other specific forms without departing from its spirit or characteristics. The described embodiments are to be considered as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. Changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.