Patent Abstract:
A flexible thermoelectric circuit is disclosed. Thermoelectric circuits have traditionally been of the rigid or substantially rigid form. Several different embodiments of thermoelectric circuits are disclosed which permit flexion in one or more directions to permit applications where flexible thermoelectric circuits are advantageous.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The description below relates to flexible thermoelectric circuits. 
     2. Description of the Related Art 
     Present Thermoelectric Modules (TEMs) use substrates to form the electrical paths to connect individual Thermoelectric Elements (TEEs). Generally, the connections are made so that one surface of an array of TEEs is heated and the opposite surface is cooled when current is passed through the array in a specified direction. Most TEMs have ceramic substrates with copper circuits to connect individual TEEs. The TEEs are soldered to the copper circuits. Other systems use printed and fired conductive ink circuits, and still others use circuits fabricated within the substrate structure itself and have the circuit pattern formed into a monolithic substrate/conductor structure. 
     In certain TEMs, Kapton or other high temperature organic substrates are used in combination with laminated or deposited copper circuit material. Such assemblies are processed using printed circuit technology to form the circuit pattern and electrically connect the TEEs. The substrate construction produces TEMs that are essentially rigid. 
     In TEM designs the substrates are on opposite sides of the TEEs forming a sandwich with the TEEs between the substrates. Because of this geometry, present substrates, even those that are polymer based, do not allow the TEM to flex to the degree needed. Furthermore, when such assemblies are bent forcefully, high shear forces are produced on individual TEEs which cause immediate failure or reduced life. In applications that involve exposure to thermal cycling, variable mechanical loadings, shock or vibration, bending and shear forces can occur repeatedly so the systems tend to have short life and can thereby make the use of TEMS impractical 
     SUMMARY OF THE INVENTION 
     Certain recent applications for TEMs benefit from the use of flexible TEMs that can be shaped to meet the geometrical constraints imposed by the optimized cooling and heating system performance. By employing such flexible TE systems, costs, size and complexity can be reduced and system capability improved. 
     Substrates are designed and constructed so that they can flex in one or more directions; the construction of such substrates follows certain design guidelines that are described in text and figures that follow. Several variations are described that can meet specific design needs such as (1) flexure in one and more than one direction; (2) designs for TEMs that flex and have zones that heat and others that cool on the same substrate surface; (3) systems that provide thermal isolation in accordance with co-pending U.S. patent application Ser. No. 09/844,818 entitled Improved Efficiency Thermoelectrics Utilizing Thermal Isolation; and (4) systems that are cascades or multi-layered. 
     Several embodiments and examples of thermoelectrics are described. A first embodiment involves a flexible thermoelectric that has a plurality of thermoelectric elements and first and second substrates. The substrates sandwich the plurality of thermoelectric elements and have electrical conductors that interconnect ones of the plurality of thermoelectric elements. At least one of the first and second substrates is constructed of a substantially rigid material, and the substrates are configured to flex in at least one direction. 
     For example, at least one substrate may be weakened, have cuts, be formed in sections, be shaped, be constructed of a material, or be modified in order to permit flexing. The flexible thermoelectric, in one embodiment, is for use with a fluid flow, and the sections or cuts are formed in a manner to improve thermal isolation from section to section in at least the direction of fluid flow. Other features may be provided to provide thermal isolation in the direction of fluid flow. 
     In one embodiment, the thermoelectric flexes in at least two directions. In another embodiment, the thermoelectric is constructed with a single layer of thermoelectric elements, and cools on a first side and heats on a second side, in response to an electrical current. Alternatively, or in addition, at least portions of the thermoelectric may have multiple layers of thermoelectric elements. In this manner, a first plurality of thermoelectric elements may be positioned along a first side of a central substrate and a second plurality of thermoelectric elements may be positioned along an opposing side of the central substrate. The first plurality of thermoelectric elements are sandwiched between the first substrate and the central substrate, and the second plurality of thermoelectric elements are sandwiched between said second substrate and the central substrate. In this embodiment, the flexible thermoelectric may be configured to provide both heating and cooling on one side of the thermoelectric, in response to a current flow. 
     In one embodiment, the flexible thermoelectric further has at least a first thermal conductor configured to provide heat flow to and/or from the thermoelectric. In addition, the thermal conductor strengthens the thermoelectric. 
     Another example of a flexible thermoelectric has a plurality of thermoelectric elements, and first and second substrates sandwiching the plurality of thermoelectric elements, wherein at least one of the first and second substrates is constructed in sections in a manner to permit flex of the thermoelectric in at least one direction. 
     At least one of the substrates may be weakened, formed in sections, have cuts, be of a material selected, or be shaped, to permit flexing. As with the previous embodiment, the flexible thermoelectric may be for use with a fluid flow, and the cuts may be formed in a manner to improve thermal isolation from section to section in at least the direction of fluid flow. In one advantageous embodiment, the flexible thermoelectric flexes in at least two directions. 
     Again, the flexible thermoelectric may also be constructed with a single layer of thermoelectric elements, or multiple layers of thermoelectric elements. The flexible thermoelectric may be configured to cool on a first side and heat on a second side, or to both cool and heat on the same side. For example, a first plurality of thermoelectric elements may be positioned along a first side of a central substrate and a second plurality of thermoelectric elements may be positioned along an opposing side of the central substrate, where the first plurality of thermoelectric elements are sandwiched between the first substrate and the central substrate, and the second plurality of thermoelectric elements are sandwiched between said second substrate and the central substrate. A thermal conductor may be provided for heat flow to and/or from the thermoelectric. In addition, a thermal conductor may be used to strengthen the thermoelectric. 
     In another embodiment, a flexible thermoelectric has a plurality of thermoelectric elements, and first and second substrates sandwiching the plurality of thermoelectric elements. In this embodiment, preferably, at least one of the first and second substrates is constructed in a non-uniform manner to permit flex of the thermoelectric in at least one direction. For example, at least one substrate is weakened in places, is formed in sections, has cuts in a plurality of locations, is shaped non-uniformly, or is formed of a material in certain locations in order to permit flexing. Where the thermoelectric is for use with a fluid flow, the cuts or sections or non-uniformities are preferably formed in a manner to improve thermal isolation in at least the direction of fluid flow. In one embodiment, the thermoelectric flexes in at least two directions. 
     The thermoelectric may be constructed with a single layer of thermoelectric elements, or with multiple layers of thermoelectrics. In this manner, the thermoelectric may be configured to cool on a first side and heat on a second side, and/or provide both heating and cooling on the same side. For example, a first plurality of thermoelectric elements may be positioned along a first side of a central substrate and a second plurality of thermoelectric elements may be positioned along an opposing side of the central substrate, the first plurality of thermoelectric elements sandwiched between the first substrate and the central substrate, and the second plurality of thermoelectric elements sandwiched between said second substrate and the central substrate. 
     A method of constructing a flexible thermoelectric is also disclosed, involving the steps of providing a plurality of thermoelectric elements, and positioning or forming the thermoelectric elements between first and second substrates, wherein at least one of the substrates is constructed of a substantially rigid material, and configured to permit flexing of the thermoelectric. 
     In accordance with the method, the substrates may be formed in sections, may be weakened in locations, may have cuts, may be shaped, and/or may be formed of material selected to permit flexing in one or more directions. Where the resulting thermoelectric is for use with a fluid flow, the method involves making the thermoelectric in a manner to improve thermal isolation in at least the direction of fluid flow. 
     The method may involve forming a single layer of thermoelectric elements, or multiple layers of thermoelectric elements. In this manner, the thermoelectric may be configured to provide heating on one side and cooling on another, and/or both heating and cooling on the same side. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a conventional TEM with a ceramic substrate. 
     FIG. 2 depicts a typical circuit pattern for a conventional TEM. 
     FIG. 3 depicts a substrate for flexible TEMs. 
     FIG. 4 depicts a TEM flexible in one direction. 
     FIG. 5 depicts a TEM flexible in two directions. 
     FIG. 6 depicts a TEM flexible in multiple directions. 
     FIG. 7 depicts a flexible TEM with heating and cooling in separate zones of the same substrate. 
     FIG. 8 depicts a multi-layer flexible substrate. 
     FIG. 9 depicts representative patterns for flexible conductors in a flexible TEM. 
     FIG. 10 depicts a TEM with enhanced heat transfer produced by secondary thermally conductive members. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1A depicts a conventional TEM  100  with substantially rigid first and second substrates  101 ,  102 . Power supply  103  provides current to the TEM  100 . FIG. 1B depicts details of the TEM&#39;s  100  internal circuitry. P-type  104  and N-type  105  TEEs alternate and are electrically connected in series through circuits  106  and  107 . The circuits  106  and  107  are attached to the substrates  101  and  102 , respectively. 
     When the TEM  100  is connected to the power supply  103 , the electrons flow in the direction indicated by arrows  108 . All of the electrons flow from P-type TEEs  104  to a circuit  106  to N-type TEEs  105  on the first substrate  101  side. On the second substrate  102  side, exactly the opposite occurs. Electrons always flow from the N-type TEEs  105  through circuits  107  to P-type TEEs  104 . Under these circumstances, the flow of heat is shown by the arrows, with q c  indicating cooling at substrate  101  and q h  indicating heating at substrate  102 . The power in is denoted by q in . T c  indicates the temperature of the first substrate  101 , and T h  indicates the temperature of the second substrate  102 . 
     FIG. 2 depicts in more detail a typical circuit pattern for the principal components of the TEM of FIG. 1. A first upper substrate  201  consists of a series of electrically conductive circuits  203  to which are soldered or otherwise uniformly and electrically connected TEEs  204 ,  205 ,  206 ,  207 ,  208  and  209 . In this configuration, every circuit  203  has two TEEs, one N-type and one P-type, attached. A corresponding second or lower substrate  202  has electrically conductive circuits  203  attached. The lower substrate  202  also has two electrical wires  210  and  212  electrically attached to two of the circuits  203 , the wires  210  and  212  are shown sheathed in insulation  211  and  213 , respectively. 
     When assembled, the upper substrate  201  is positioned with respect to the lower substrate  202  so that the two ends of the TEE  204  engage circuits  203 . Similarly, TEEs  205 ,  206 ,  207 ,  208  and  209  ends are engaged as shown. Current enters through the wire  210  and passes upward from the lower substrate  202  to the upper substrate  203  through the TEE  205 . It then passes along the circuit  203  to the TEE  206 , and so on, as was illustrated in FIG.  1 . This pattern continues through TEE  208  where the circuit  203  connects to TEE  209  on the lower substrate  202 . The current passes through  209  to the upper substrate  201 , and along the second set of circuits  203  which are interconnected through TEEs (not shown). The current continues to pass through circuits  203  and TEEs until it reaches TEE  204  and circuit  203 . From there the current exits the TEM through wire  212 . 
     Current is directed along the desired paths by electrically isolating the separate circuits  203  by electrically insulative areas  214 . 
     Generally, it is desirable that the upper and lower substrates  201  and  202  are constructed of electrical nonconductive materials such as alumina ceramic or the like. Preferably, the substrate materials have as high a thermal conductivity as possible perpendicular to the plane of FIG. 2 so that heat can be transported through the substrates to the outer faces of the assembled TEM with as little temperature change as possible. The circuit material and the circuit  203  design should maximize electrical conductivity between adjacent TEEs. This combination of design and material properties held minimize thermal and electrical losses in the TEM. 
     FIG. 3A depicts an example of a substrate system  300  wherein at least one of the substrates is constructed of a substantially rigid material in one preferred embodiment. The upper substrate  301  is made from a high thermal conductivity flexible material preferably such as Kapton polyamide film, very thin fiberglass, or any other flexible material. Circuits  303  are on the upper substrate in a pattern. Similarly, a lower substrate  302 , which is preferably, but not necessarily, of a substantially rigid material, has circuits  315  arranged in a pattern on it. TEEs  304 ,  305 ,  306  and  307  are some of the TEEs in the TEM. Wires  309  and  311  each attach to a circuit. Insulation  310  and  312  sheathe the wire. 
     The upper circuit  301  is connected to the lower circuit  302  so that the respective ends of the TEEs  304 ,  305 ,  306  and  307  mate at the positions indicated in FIG.  3 A. The TEEs are of N-type and P-type and are arrayed with the circuits  303  and  315  so that current flows alternately through each type of material. The pattern is such that current flows from one wire  309  through the TEM  300  to the other wire  311 , as was described in detail in FIG.  2 . 
     Preferably, after assembly of the TEM, slots are cut into the lower substrate at positions  313  so as to separate the lower substrate  302  into segments. The upper substrate  301  can flex in the areas  308  if the circuits  303  can flex so as to not degrade the TEE circuit  303  electrical connection. By separating the substrate  302  at several locations, the TEM can be flexed in a concave direction with respect to the outer surface of the TEM upper substrate  301 . Furthermore, if a cut  314  is made in the upper substrate  301  at several locations, and the cuts  316  are made in the lower substrate  302 , the TEM can be twisted about its length as well as bent. In addition, if slots are made in the lower substrate  302  so as to remove material as shown at  313 , the TEM can flex in both directions. 
     The general description of FIG. 3A holds for an even number of TEEs in a horizontal row. For larger number of TEEs, there will be one circuit  315  for every two TEEs added in each row of the lower substrate  302 . One circuit  317  is added for each circuit  315  added. 
     FIG. 3B depicts a configuration  320  with an odd number of TEEs (for example,  325 ,  326  and  327 ) in each horizontal row. For the geometry, both the upper substrate  321  and the lower substrate  322  have both horizontal and vertical circuits  323  and  324 . As in FIG. 2, the assembly consists of N and P-type TEEs, and circuits arranged as described therein. Wire assemblies  333  and  334  are attached at the ends. Cuts  329  and  330  are made respectively in the upper substrate  321  and the lower substrate  322  at the locations shown. 
     When the TEM is assembled, for example, current enters through wire assembly  333  and into TEE  325  and so on until it exits at the wire assembly  324 , after passing through the TEE  335 . Again, the TEEs are alternately P and N-types so that as current passes, one side is heated and the other cooled. The cuts  329  and  330  allow the assembled TEM to flex in two directions if the circuits  323  and  324  can flex or bend at  331  and  332 . If the cuts  329  and  330  are formed as slots with the removal of substrate material, the corresponding flexure points can bend in both directions. Finally, if cuts  336  and  337  are incorporated, the assembled TEM can twist about its length. 
     In FIGS. 3A and 3B TEMs  300  and  320  form separate arrays. As a part of the present invention, part of a TEM can be of one type and other parts of the other type. 
     FIG. 4 depicts a TEM  400  with an upper substrate  401  and cut lower substrate  402 . Again, in this embodiment, the lower substrate material is substantially rigid, but is modified or configured in a manner to be flexible. In this configuration, dividing the substrate into sections permits the flexibility. Wire assemblies  406  and  407  are attached at each end. In accordance with the geometry of FIG. 3A, each row has an even number of TEEs  405  and  408 . The TEEs are connected via circuits (not shown) as in FIG.  3 A. The circuits, in practice, generally are very thin, such as printed circuit traces. Therefore, the circuits are often not shown in the Figures herein, except to illustrate the manner in which the circuits connect the individual TEEs. 
     The TEM has been bent in the principal direction indicated in the description of FIG.  3 A. Spaces  403  develop because of the flexure. For descriptive purposes, the lower substrate  402  has not been cut at location  404  and therefore, that segment does not have a bend to it. 
     FIG. 5 depicts a TEM  500  formed according to FIG.  3 B. It consists of a lower substrate  501 , preferably but not necessarily constructed from substantially rigid material with cuts  505  and  506  to permit flexing and an upper substrate  502  with cuts  503  and  504 . TEEs and electrical paths are connected as discussed in FIGS. 2 and 3B. 
     The TEM  500  is shown flexed in two directions. The cuts  503  are spread open and form gaps in the upper substrate  502  where TEM  500  is flexed in one direction while other cuts  504  are not open where TEM  500  is flexed in the opposite direction. Similarly, in lower substrate  501 , cuts  505  are closed while cuts  506  are open. 
     As noted in the discussion of FIGS. 3A and 3B, where material is removed (as an example, regions at slots  504  and  505 ) such locations contribute to flexure since the substrates  501  and  502  are able to flex at those locations as well. 
     FIG. 6 depicts a TEM  600  of the type described in FIG.  3 A. Wire assemblies  608  and  609  are attached to the lower substrate  601 . Upper substrate  602  and TEEs  603  are connected with circuits (not shown) as discussed in FIG.  3 A. Slots  606  are in the upper substrate  602 . Opposite the slots  606  are partial cuts not visible in FIG. 6, but of the type shown as slot  314  of the upper substrate  301  in FIG.  3 A. 
     The TEM  600  is depicted as twisted about its length so that the upper substrate  602  is vertical at location  607  and horizontal at the opposite end  610 . The two adjacent circuits at  604  and the two adjacent circuits at  605  act as rigid units since there is no twist in the TEM  600  at these points. Twisting occurs at slots  606  in the upper substrate  602  and the partial slots (not shown) at the corresponding location in lower substrate  601 . TEEs  603  are connected via a circuit (not shown) that is adjacent to a partial slot in the lower substrate  601 . Current can pass through the TEM  600  via wire assemblies  608  and  609 . 
     FIG. 7 depicts a TEM  700  with the upper substrate  701 ,  703  and  705  and a lower substrate  702 ,  704  and  706 , circuits (not shown), and TEEs  712 ,  713 ,  715  and  716 . The upper substrate  701  is folded upon itself at fold  708 . Grease  707 , solder or other high thermal conductivity material fills the space between the two segments of the upper substrate  703  and  705 . A circuit as described in FIG. 2 (not shown), connects TEE  712  to TEE  713 . The circuit pattern is either that of FIG. 3A or  3 B. At the fold  708 , the TEEs  712  and  713  are both of the same type. All other TEEs are alternately N-type and P-type and are connected as described in FIG.  2 . 
     As an example, during operation, current enters at wire assembly  713  and passes through an N-type TEE  715  and on through the first of the TEM  700  and exits through TEE  716  at wire assembly  714 . With this as an example, the lower substrate surface  706  is cooled and the upper substrate surface  705  is heated. The heat generated is conducted to the upper substrate surface  703  by the grease  707 . Since the two connecting TEEs  712  and  713  are of the same type and all others are electrically connected in series and of alternating type, the upper substrate surfaces  701  and  703  are cooled and the lower substrate surfaces  702  and  704  are heated. The upper substrate surface  703  removes the heat generated at the upper substrate surface  705  and cools that surface, so that the lower substrate surface  706  is significantly colder than the portion of the upper substrate surface  701 , not contact with substrate surface  705 . Thus, a typical TEM cascade is formed in the region of the contact zone  707 , and a single stage TEM is formed elsewhere. With this geometry, design of the TEEs in the regions between substrate surfaces  705  and  706  and also between  702  and  703 , can be of a form well known to the art. 
     It is clear that other levels could be added to the cascade region of TEM  700 , and that multiple separate cascades could be fabricated by one or more flexible TEMs employing the above concepts and simple extensions thereof. 
     FIG. 8 depicts another variation of a TEM  800 . Herein, a backbone substrate  801  has circuits on each side preferably of the type of upper substrate  301  of FIG.  3 A. The TEM  800  has two additional substrates, an upper substrate  802  and a lower substrate  804 . Each has slots  807  formed by removing substrate material. Between the upper substrate  802  and the backbone substrate  801  are TEEs  803  and between the backbone substrate  801  and the lower substrate  804  are TEEs  805 . The TEEs  803  and  805  are alternately N-type and P-type and are connected by circuits, as in FIG. 3A (not shown). In this example, the components are electrically connected so that the portion above the insulation layer in the backbone substrate  301  forms one TEM circuit with wire connections  808  and  809  and the portion below forms a separate TEM circuit with wire connections  810  and  811 . 
     The TEM  800  operates by passing current from, for example,  808  to  809  and a separate current from  810  to  811 . In this example, the current flows so that the upper substrate  802  is cooled and hence the upper surface of the backbone substrate  801  is heated. Heat passes through to the lower surface of the backbone substrate  801 , which is the cooled side of the lower portion. The lower substrate  804  is therefore heated. Thus, in this example, the TEM  800  is a cascade system. Alternately, the backbone substrate  801  could be wider, thermal energy transferred through the added width, and the currents could flow so that the backbone substrate  801  was heated or cooled by both the upper and lower TEMs. 
     Currents, TEE materials, number of TEEs and TEE dimensions can differ anywhere within the TEM  800  to achieve specific design and performance objectives. Also, the upper substrate  802  and the lower substrate  804  need not be the same dimensions or exact shape, thus, for example, a portion  812  of the lower substrate  804  need not have a corresponding part of the upper substrate  802 , directly in thermal contact with it. As additional examples, the upper substrate  802  could be of the type shown in FIG.  3 B and the lower substrate  804  of the type shown in FIG.  3 A. Or, the upper substrate  302  could have fewer TEEs in each row compared to the lower substrate  804  and the total number of TEEs could differ among rows. Also, the electrical connections could be modified to pass current from the upper circuits of TEM  800  to the lower circuits so that two of the wires, for example,  809  and  811 , would be eliminated. Other connection changes could be made to modify performance at certain locations, or to achieve other purposes. 
     The flexible TEMs described herein will often have improved thermal isolation as explained in co-pending U.S. patent application Ser. No. 09/844,818 entitled Improved Efficiency Thermoelectrics Utilizing Thermal Isolation, filed Apr. 27, 2001. As explained in that application, when the thermoelectric is utilized for heating or cooling of a flowing fluid, thermal isolation in the direction of flow improves the efficiency of the thermoelectric. Therefore, as an example, the cuts in FIGS. 4,  5  and  8 , or sections of substrates may be made to correspond, where practical, to provide improved thermal isolation between sections separated by the cuts, in order to improve overall efficiency of the flexible thermoelectric. 
     FIG. 9 depicts a portion of a substrate  900  that consists of flexible substrate material  901 , circuits  902  and  903 , solder mask  904 , TEEs  905  and slot  906 . In this design, the assembly incorporates substrate  900  to mechanically connect parts. 
     The circuit  902  is of the form previously discussed in FIGS. 3A and 3B. Circuit  903  depicts a method for allowing that circuit to flex in the region between TEEs  905 . In this configuration, solder mask  904  covers a portion of the circuit  903  so as to prevent solder from accumulating where it is so covered. If the substrate  901  is flexed, bending will occur preferentially in the solder mask  904  region, since the circuit  903  does not have solder build up there and hence, is thinnest and most easily flexed there. Such preferential bending reduces mechanical stress at the interface of the TEE  905  and circuit  903 . 
     FIG. 9B depicts another geometry  920  which achieves flexure. Flexible substrate material  921  has circuits  922  and  923  attached, TEEs  924  and an elongated slot  926 . Sections  925  of the circuit  923  have been omitted. 
     The geometry  920  is known to the flexible circuit industry as a design that allows severe or repeated flexure with good stability. Further, by proper design, known to the art, solder accumulation in the flexure can be either prevented or reduced to acceptable levels and shear stresses induced during flexure (at the circuit  923  and substrate  921  interface) can be reduced. 
     Other designs for electrically conductive flexures, such as circuits that incorporate components not attached to the substrate (e.g., shunt wires and strips, electrically conductive hinges, and the like) can be employed to allow needed movement and are the subject of this invention. 
     FIG. 10 depicts a portion  1000  of a TEM of the present invention. It consists of an upper substrate  1001  with circuits  1002  and upper thermal conductors  1003  attached. A lower substrate  1005  has circuit  1006  and thermal conductor  1007  attached. TEEs  1004  are electrically connected to the circuits. Slots or cuts  1008  are in the upper substrate  1001  to allow flexure. 
     The thermal conductors  1003  and  1007  are designed to increase and distribute heat flow to and from the TEM. The conductors  1003  and  1007  are useful in high-power TEMs since typical substrate materials have relatively low thermal conductivity, and thereby reduce TEM performance. Performance can be improved by utilizing thermal conductors to increase thermal energy transport across the substrate and also mechanically strengthen the TEM. These improvements can be done by (1) maximizing the surface area of the circuit substrate and thermal conductor interface, (2) minimizing thermal resistance across the interfaces by selecting materials or material composites that minimize interfacial thermal resistance, or (3) utilizing the thermal conductors as structural members so that the substrate can be thinner, weaker or otherwise allow selection from a broader class of electrical insulators. These provide examples of designs that achieve enhanced performance, cost reduction, improved durability, size reduction and other benefits by utilizing additional componentry with the substrate. The above are presented as examples, and they do not cover all variations or otherwise restrict the scope of the invention. 
     In the discussion of FIGS. 3 through 10, it was stated that the substrate could have cuts, slots and sections removed to achieve flexure and bending. The same effect can be achieved by utilizing substrates that are mechanically weak. For example, the substrate could be made of a soft or weak material such as Teflon TFE, a silicone rubber, or the like; it could be made very thin; it could be mechanically weakened by incorporating holes, porosity, and making it from felt or the like; could be chemically weakened, treated to have its flexibility increased in selected areas, etched or the like; it could be fabricated with areas weakened, omitted, treated or otherwise modified, made thinner, slotted or the like that frees adjacent TEEs to move toward or away from one another so as to allow flexure and/or twisting within the TEM. The substrate could be completely omitted from the TEM so that unconstrained circuits would connect TEEs. Upon installation (and after flexure), the circuits could be attached to a structural material wherein the bonding agent or the structural material serves the function of a substrate within the system. 
     Although several examples and embodiments of flexible thermoelectric modules have been described above in various configurations, any flexible thermoelectric module and any variations of those embodiments described above are contemplated. Accordingly, the scope of the present invention is defined by the claims and not by any particular example. The examples above are meant to be illustrative and not in any way restrictive. In addition, the language of the claims is intended in its ordinary and accustomed meaning, without reference or special definition to any of the terms or limitation to the embodiments of those terms in the specification.

Technology Classification (CPC): 7