Patent Publication Number: US-11044789-B2

Title: Three dimensionally printed heated positive temperature coefficient tubes

Description:
BACKGROUND 
     This application relates generally to positive temperature coefficient heater elements, and specifically to additively manufactured positive temperature coefficient heater elements. 
     Heated tubes or tubes are used in a variety of industries to heat fluid passing through such a vessel and prevent unwanted freezing. In prior art, resistor heaters that are spiral wound around the core of the tube or tube are used to provide heat. Alternatively, heater tapes are wrapped around the core of the tube or tube. These types of heating elements require sensors or thermostats to prevent overheating, or the use of positive temperature coefficient of resistance (PTC) heating material to limit overheating. These types of heating elements can be bulky and require excess space around the tubes, in addition to requiring external control. 
     SUMMARY 
     In a first embodiment, a heater tube assembly includes a tube, a bus bar network on the tube, a positive temperature coefficient heater on the tube, a closeout adhesive securing the bus bar network and the positive temperature coefficient heater to the tube, and an outer dielectric layer overlaying the bus bar network and the positive temperature coefficient heater. The bus bar network includes one or more layers of a first additively manufactured conductive ink. The positive temperature coefficient heater comprising one or more layers of a second additively manufactured conductive ink. The positive temperature coefficient heater is electrically connected to the bus bar network. 
     In a second embodiment, a heater tube assembly includes a tube, a bus bar network including at least one hot bus bar and at least one neutral bus bar on the tube, a heater on the tube having a thickness between 0.0001 and 0.010 inches, a closeout adhesive securing the bus bar network and the heater to the tube, and an outer dielectric layer overlaying the bus bar network and the heater. The bus bar network is made of one or more layers of a first additively manufactured conductive ink, and the bus bar network is a geometric pattern selected from the group consisting of a spiraled pattern, a redundant dual-circuit pattern, a crisscross pattern, or combinations thereof. The heater includes a plurality of layers of a second additively manufactured conductive ink, each of the plurality of layers has a thickness of between 1 and 100 microns, and the heater is electrically connected to the bus bar network. 
     In a third embodiment, a method of making a heater tube assembly includes additively manufacturing one or more layers of a first conductive ink on a tube to create a bus bar, additively manufacturing one or more layers of a second conductive ink on a tube to create a positive temperature coefficient heater overlapping with the bus bar, closing out the bus bar and the positive temperature coefficient heater with an adhesive, and encapsulating the bus bar and the positive temperature coefficient heater with an outer dielectric layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1B  are perspective views of a prior art heater wire tube configuration. 
         FIG. 2  is a cross-section view of a printed heater tube with a conductive tube. 
         FIG. 3  is a cross-section view of a printed heater tube with a non-conductive tube. 
         FIGS. 4-6  are perspective views of a printed heater tube with printed bus bars in various patterns. 
         FIGS. 7-10  are perspective views of a printed heater tube with printed PTC heaters. 
         FIGS. 11-15  are perspective views of printed bus bar connections and heaters on heater tube. 
         FIG. 16  is a perspective view of printed bus bars and heater allowing for constant power. 
         FIGS. 17A-17B  are a perspective view and cross-sectional view of a printed PTC heater and bus bars allowing for constant voltage across the length of the tube. 
         FIGS. 18-23  are cross-sectional views of printed bus bar electrical connections. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed are flexible printed heating elements made via additive manufacturing with conductive inks. A flexible substrate is used so that the printed heating element can conform to the shape of the component surface to which it is applied. A self-limiting positive temperature coefficient (PTC) heating material is used. 
       FIGS. 1A-1B  are views of prior art heater wired tube  10 .  FIG. 1A  shows a perspective, cut-away view of tube  10 , while  FIG. 1B  shows a side view schematic of one wall of tube  10 .  FIGS. 1A and 1B  will be discussed together. Tube  10  includes PFA liner  12 ; heater wires  14 , stainless steel braid  16 , and aramid fiber braid  18 . 
     PFA liner  12  is a perfluoroalkoxy alkane liner inside tube  10 . PFA liner is an insulating material inside tube  10  that separates heater wires  14  from fluid passing through tube  10 . PFA liner  12  electrically and chemically insulates fluid passing through tube  10  from heater wires  14  and braids  16 ,  18 . 
     Heater wires  14  provide heat to tube  10 , and are spiral wound around tube  10 . Heater wires  14  can be, for example polyimide-insulated nichrome. Heater wires  14  may also be embedded in a silicone material. Heater wires  14  are joined at the end of tube  10  to allow for electrical connection to both positive (+) and negative (−) wires at that end. In the case of dual element tubes, there can be two sets of wires wound together. Stainless steel braid  16  and aramid fiber braid  18  provide structural support and protection of heater wires  14 . The prior art configuration of tube  10  is bulky due to multiple layers of protection and support in the form or braids  16 ,  18 , and the winding of wires  14  around a core material. 
       FIG. 2  is a cross-section view of printed heater tube  20 A with conductive tube  24 A. From inside to outside, printed heater tube  20 A includes liner  22 , conductive tube  24 A, inner dielectric  26 , PTC heater  28 , bus bar  30 , closeout adhesive  32 , outer dielectric  34 , and protection layer  36 . 
     Liner  22  rests inside tube  20 A for chemical compatibility with the fluid flowing through tube  20 A. In some cases, liner  22  is made of a material to allow water potability. Liner  22  can be, for example, a fluoropolymer material (such as polytetrafluoroethylene (PTFE) or perfluoroalkoxy (PFA)), a fluoroelastomer, a silicone, a polyolefin (such as polyethylene or polypropylene), acrylonitrile butadiene rubbers (such as nitrile or NBR), ethylene propylene diene monomer rubbers (such as EPDM), polyurethane (PU), or combinations thereof. 
     Conductive tube  24 A is the structural part of tube  20 A through which fluid flows. Conductive tube materials include metals such as stainless steel or titanium. Other types of conductive tube materials include carbon-filled plastics, such as polyetherimide (PEI), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyimide (PI), ethylene tetrafluoroethylene (ETFE), polyvinylchloride (PVC), or polyvinylidene difluoride (PVDF) filled with carbon such as carbon black, carbon nanotubes, or carbon fibers. 
     Inner dielectric  26  isolates conductive tube  24 A from bus bar  30  and PTC heater  28 . Inner dielectric  26  can be polyimide, polyurethane, silicone, or other materials deemed suitable by a person of skill in the art. If conductive tube  24 A is a carbon-filled plastic, then inner dielectric  26  can be the same plastic but un-filled, or glass-filled. 
     PTC heater  28  is the heating element of heater tube  20 . PTC heater  28  is an additively manufactured PTC ink on the surface of inner dielectric  26 . PTC heaters are self-regulating heaters that run open loop without any external diagnostic controls. Positive temperature coefficient heaters come to full power and heat up quickly to optimum temperature, but as heat increases, power consumption drops. This dynamic type of heater is effective and time and energy efficient. Thus, PTC heater  28  made with PTC ink does not require an outside temperature control. Examples of PTC inks include DuPont® 7292 from DuPont USA or Henkel® EC1 8060 from Henkel. 
     The PTC ink of PTC heater  28  is formulated to allow highly detailed precision printing, and maintain a high resistance without bleeding between adjacent additively manufactured lines. The PTC ink is additively manufactured onto inner dielectric  26  through a printing process such as ink-jet, aerosol-jet printing, or other suitable processes. 
     Typically, ink-jet or aerosol-jet printing can be used to additively manufacture PTC heater  28 , depending on the type of PTC ink chosen, desired layer thickness, and dimensions of PTC heater  28 . Printing PTC ink may require dilution of the ink to allow precision and prevent print-head clogging. Depending on the specific PTC ink used, the ink may need to be diluted from 1% to 50% with appropriate solvents. 
     For ink-jet and aerosol-jet methods, the print head should be moveable at least on (x, y, z) axes and programmable with the geometric pattern specific to the component on which PTC heater  28  will be applied. The specific print heat and additively manufacturing method will be dependent on the exact PTC ink formulations and requirements set forth by the manufacturer of the PTC ink. Ink-jet and aerosol-jet printers and printing heads can also be utilized for two dimensional applications, such as printing on a dielectric layer of a non-conductive tube, but ideally can be adapted to enable three dimensional (three dimensional) printing capabilities by attaching the printing heads onto a numerically controlled robotic arm. For example, three dimensional ink-jet and aerosol-jet printing equipment developed by Ultimaker® (three-dimensional ink-jet equipment) or Optomec® (three-dimensional aerosol-jet equipment) can be used. For ink-jet or aerosol-jet methods, the printing head temperatures, flow rates, nozzle sizes are also selected based on the PTC ink being printed, required conductive ink thickness, and substrate to be additive manufactured on. Alternatively, the PTC ink can be deposited or direct printed with extruded ink on the tube using micro-dispensing pumps such as those made by nScrypt®. 
     The printing is accomplished in an additive manner, meaning the print head takes one or more passes before a desired element resistance is reached in the desired geometric pattern and desired dimensions, which matches the curvature of the component. Depending on the application, two or more, three or more, four or more, or additional passes may be appropriate. 
     The PTC ink of additively manufactured PTC heater  28  should have a thickness of approximately between 0.0001″-0.010″. Multiple passes are done by the print head when applying the conductive ink. Each layer deposited through individual passes of the print head should have a thickness of approximately 1-100 microns. Multiple passes allows for slow buildup of the PTC ink to the correct resistance and geometric pattern. Additionally, multiple passes allows for tailoring of the PTC ink on certain portions of the component surface. For instance, PTC ink with a lower resistance (e.g., with a higher number of layers) and a greater thickness may be additively manufactured on a first portion of the component compared to a second portion of the component. 
     After additively manufacturing PTC heater  28 , the PTC ink is cured. The curing process of additively manufactured PTC heater  28  depends on the type of PTC ink used. In some instances, the PTC ink will air dry. In other instances, heat, infrared exposure, UV exposure, chemical, or other methods can be used to cure the PTC ink. The PTC ink can be cured (partially or fully) during the printing process, to avoid dripping or smearing of the ink during processing. 
     Bus bar  30  is also additively manufactured onto the surface of inner dielectric  26 . Bus bar  30 , made of a conductive ink, provide electrical connection from PTC heater  28  to an outside controller (not pictured). Bus bar  30  can be made of a conductive carbon filled or silver filled ink, such as DuPont® 5205 available from DuPont USA or Henkel® EC1 1010 available from Henkel. 
     Bus bar  30  is additively manufactured in a similar method to that described with reference to PTC heater  28 . Generally, bus bar  30  is additively manufactured on top of and overlapping with portions of PTC heater  28  to create an electrical connection between PTC heater  28  and bus bar  30 . Specific geometries of bus bar  30  and PTC heater  28  are discussed with reference to  FIGS. 4-15  below. 
     Closeout adhesive  32  seals and encapsulates PTC heater  28  and bus bar  30 . Closeout adhesive  32  is applied on top of both PTC heater  28  and bus bar  30  to secure and protect these components, separating them from the external environment. Closeout adhesive  32  can be, for example, an acrylic or rubber pressure sensitive adhesive, or ethylene-vinyl acetate. 
     Outer dielectric  34  is applied to printed heater tube  20 A after closeout adhesive  32  is cured or dried. Outer dielectric  34  electrically insulates bus bar  30  from the external environment, preventing shorting. Outer dielectric  34  can be made of the same or a different dielectric material than inner dielectric  26 . Outer dielectric  34  can be, for example, a polyimide, polyurethane, or silicone. If conductive tube  24 A is a carbon-filled plastic, then outer dielectric  34  can be made of the same plastic that is unfilled or filled with glass fiber. 
     Protection layer  36  is an optional external layer of printed heater tube  20 A that adds extra protection to PTC heater  28 . Protection layer  36  can defend against handling and abrasion damage, and can add pressure strength to the assembly. Protection layer  36  can optionally be conductive for both static discharge and lightning protection. Protection layer  36  can be, for example, a braided metallic wire such as stainless steel or titanium, braided aramid, or braided dry fiberglass. If conductive tube  24 A is a rigid tube, then protection layer  36  can alternatively be a carbon fiber or fiberglass composite made with epoxy, phenolic, or benzoxazine resin. Such a carbon fiber or fiberglass composite would be braided or spiral-wound for further strength. Protection layer  36  can alternatively be made of multiple sub-layers. 
       FIG. 3  is a cross-section view of printed heater tube  20 B with non-conductive tube  24 B. For inside to outside, printed heater tube  20 B includes liner  22 , non-conductive tube  24 B, PTC heater  28 , bus bar  30 , closeout adhesive  32 , outer dielectric  34 , and protection layer  36 . The components of printed heater tube  20 B are the same as tube in printed heater tube  20 A except where otherwise noted. 
     Specifically, non-conductive tube  24 B differs from tube  24 A of  FIG. 2  in that non-conductive tube  24 B is made of a material that is not conductive. Tube  24 B can be, for example, non-filled or glass-filled plastics such as polyetherimide (PEI), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyimide (PI), ethylene tetrafluoroethylene (ETFE), polyvinylchloride (PVC), or polyvinylidene difluoride (PVDF). If non-conductive tube  24 B is filled with glass, it can be in the form of spheres, hollow spheres, or fibers. 
     The use of a non-conductive tube  24 B in printed heater tube  20 B eliminated the need for inner dielectric  26 , as there is no electrical insulation needed between tube  24 B and PTC heater  28  (or bus bar  30 ). For this reason, PTC heater  28  and bus bar  30  can be additively manufactured directly onto the surface of nonconductive tube  24 B. 
       FIGS. 4-6  are perspective views of a printed heater tube with printed bus bars in various patterns. Generally, bus bar  30  of  FIGS. 2, 3 , can be printed as both hot bus bars and neutral bus bars on the surface of the tube to provide appropriate electrical connection to PTC heater  28 . 
       FIG. 4  shows printed heater tube  40  with hot bus bar  42  and neutral bus bar  44  that are in parallel along the length of heater tube  40 . Hot bus bar  42  and neutral bus bar  44  are both made of conductive ink, as discussed in reference to  FIG. 2 , and establishing opposing charges across tube  40 . Hot bus bar  42  and neutral bust bar  44  provide an electrical connection to an accompanying PTC heater along the length of tube  40 . The accompanying PTC heater (not shown) can be printed across heater tube  40  so that it overlaps with both hot bus bar  42  and neutral bus bar  44 . 
       FIG. 5  shows printed heater tube  46  with hot bus bar  48  and neutral bus bar  50 , which function in the same manner as the bus bars of  FIG. 4 . In tube  46 , bus bars  48 ,  50  are in a spiral pattern around the surface of tube  46 , allowing for additional electrical connection to a PTC heater (not shown) printed over bus bars  48 ,  50 . 
       FIG. 6  shows printed heater tube  52  with two hot bus bars  54  and two neutral bus bars  56 , which function in the same manner as the bus bars of  FIG. 4 . Bus bars  54 ,  56  are in a redundant dual circuit pattern. Bus bars  54 ,  56  can alternatively be spiraled similar to bus bars  46 ,  48  in  FIG. 5 . The varying geometric patterns of bus bars in  FIGS. 4-6  can be selected depending on the desired PTC heater pattern, desired heater resistance range, heating consistency, and other factors affecting required heating of fluid running through the printed heater tubes. 
       FIGS. 7-10  are perspective views of printed heater tubes with printed PTC heaters in a variety of geometric patterns. PTC ink can be applied to the entire tube, with the exception of the ends of the tubes. The PTC ink in  FIGS. 7-10  can be manufactured as discussed with reference to  FIG. 2 . 
       FIGS. 7-8  show only PTC ink on printed heater tubes.  FIG. 7  shows printed heater tube  58  with PTC ink  60  printed in distinct, equal bands patterns along the length of tube  58 . This allows for even distribution of PTC ink  60  across tube  58 , and measured heating of fluid flowing through tube  58  when that fluid passes through the bands of PTC ink  60 . 
       FIG. 8  shows printed heater tube  62  with PTC ink  64 , where PTC ink  64  is a monolithic structure that acts as a sleeve around tube  62 . In this embodiment, PTC ink  64  consistently heats fluid flowing through tube  62  along the length of one  62 . Other geometric patterns of PTC ink can be used as desired for heating needs. 
     As shown in  FIGS. 9-10 , the conductive ink for the bus bars can be printed on top of the PTC ink.  FIG. 9  shows printed heater tube  66  with PTC ink  68 , hot bus bar  70  and neutral bus bar  72 . Bus bars  70  and  72  are arranged similarly to the bus bars in  FIG. 4 . PTC ink  68 , which is printed on top of bus bars  70  and  72 , is spiral wound in the reversed direction of bus bars  70 ,  72  made of conductive ink to create the necessary electrical connections where PTC ink  68  overlaps with bus bars  70 ,  72 . 
       FIG. 10  shows printed heater tube  74  with PTC ink  76 , hot bus bar  78  and neutral bus bar  80  with electrical connections  78 A and  80 A, respectively. In the pattern of  FIG. 10 , bus bars  78 ,  80  with connections  78 A,  80 A are only at the ends of the tube. This works where PTC ink  76  is in a solid sleeve pattern as discussed with reference to  FIG. 8 , as electrical connections are maintained between PTC ink  76  and bus bars  78 ,  80 . 
       FIGS. 11-12  are perspective views of printed bus bar connections on heater tube. In  FIG. 11 , printed heater tube  82  contains hot bus bar  84  (with connection  84 A) and neutral bus bar  86  (with connection  86 A). Both bus bars  84 ,  86 , have connections ( 84 A,  86 A) aligned at a single end of tube  82 . In this case, a large patch of conductive ink can be printed over connections  84 A,  86 A, at the ends of bus bars  84 ,  86 , for soldering or conductive adhesive to electrical wiring that provides power to bus bars  84 ,  86 . The voltage from bus bar to bus bar near the bus bar connections will be higher than the voltage at the opposite end of tube  82  due to the location of connections  84 A,  86 A and the resistance of the bus bar conductive ink. 
     In  FIG. 12 , printed heater tube  88  has hot bus bar  90  (with connection  90 A) and neutral bus bar  92  (with connection  92 A). Here, connections  90 A,  92 A, to bus bars  90 ,  92  are at opposite ends of tube  88 . This allows for constant voltage from one bus bar  90  to the other bus bar  92  along the length of tube  88 . 
       FIGS. 13-15  are perspective views of printed bus bars on heater tubes in heater tube assemblies printed without PTC ink. These types of assemblies do not have self-limiting properties, but can have higher power densities than assemblies with PTC ink. 
     In  FIG. 13 , printed heater tube  93  has conductive ink  94 , hot bus bar  95  with connection  95 A, and cold bus bar  96  with connection  96 A. Here, connections  95 A,  96 A to bus bars  95 ,  96 , are at opposite ends of tube  93 , but connected through PTC heater  94 . Conductive ink  94  is typically made of the same material as bus bars  95 ,  96 , but may be printed thinner. 
       FIG. 14  shows printed heater tube  97  with hot bus bar  98  and cold bus bar  99 . In this case, cold bus bar  99  is printed on one side of printed heater tube  97  and hot bus bar  98  is printed on the other side of printed heater tube  97 . Bus bars  98 ,  99  have holes to lower the power density and add flexibility to printed heater tube  97 . The density of bus bars  98 ,  99 , can be varied by adjusting the hole size, shape, and pattern to adjust the power density down the length of printed heater tube  97 . 
     Similarly, in  FIG. 15  printed heater tube  100  has hot bus bar  102  (with connection  102 A) on one side and cold bus bar  104  (with connection  104 A) on the other, however, bus bars  102 ,  104 , are in a snaking line across those surfaces instead of a straight pattern with lines. 
       FIG. 16  is a perspective view of printed heater tube  106  with hot bus bar  108 , neutral bus bar  110 , and PTC ink  112 . Bus bars  108 ,  110  run the length of heater tube  106  and terminate at the same end like the bus bars of  FIG. 11 . PTC ink  112  is separated into bands (similar to  FIG. 7 ); however, the width of the bands of PTC ink  112  gradually decreases from the first end of tube  106  to the second end. Varying the width of the PTC ink bands along the length of the tube allows for constant power down the length of tube  106  despite both bus bars  108 ,  110  terminating at the same end. 
       FIGS. 17A and 17B  show printed heater tube  114  with hot bus bar  116 , neutral bus bar  118 , and PTC ink  120 . In heater tube  114 , hot bus bar  116  runs along one side of tube  114 , while neutral bus bar  118  contains three strands running in parallel and meeting at the opposite end of tube  114  from the connector. PTC ink  120  on tube  114  is a sheet along the length of tube  114 . This configuration keeps the voltage across PTC ink  120  constant down the length of tube  114  while still having both bus bar  116 ,  118 , connections at the same end of tube  114 . PTC ink  120  does not go all the way around tube  114  (see  FIG. 15B ). These geometric patterns for bus bars and PTC ink can be varied as needed. 
       FIGS. 18-23  show printed bus bar connections on PTC heater tubes.  FIG. 18  shows printed heater tube  122  with hot bus bar  124 , cold bus bar  126  (with connection  126 A), printed PTC heaters  128 , and insulating layer  130 . In printed heater tube  122 , cold bus bar  126  connection  126 A occurs under the printed ink of PTC heater  128 , with insulator layer  130  preventing electrical shorting where cold bus bar  124  is electrically connected. In  FIG. 13 , connections are additively manufactured around the full circumference of heater tube  122 . Bus bar  126  is shorter than bus bar  124  to keep the bus bar electrical connections separate. Insulating layer  130  is added locally on top of longer bus bar  124  to electrically isolate the bus bar connection  126 A from bus bar  126 . 
       FIGS. 19-23  shows an alternative embodiment of making bus bar connections compared to connections in  FIGS. 11-16 .  FIGS. 19-21  show mechanical connections, while  FIGS. 22 and 23  show alternative methods of connections.  FIG. 19  shows a cross-section of printed heater tube  132  with bus bar  134 , connector  136 , and insulating layer  138 . Connector  136  (such as a nut) is embedded in the wall of tube  132 , and is a threaded fastener. Connector  136  can be, for example, copper, aluminum, stainless steel, titanium, silver, or other appropriate metal. Bus bar  134  is printed over connector  136 . Electrical terminals can be fastened to connector  136  while making contact with bus bar  134 . 
       FIG. 20  shows a cross-section of printed heater tube  140  with bus bar  142 , connector  144 , and insulator  146 .  FIG. 20  shows connector  144  (a stud) running through the wall of tube  140 , and is a removable threaded fastener. Connector  144  can be, for example, copper, aluminum, stainless steel, titanium, silver, or other appropriate metal. Bus bar  142  is printed around connector  144 . Electrical terminals can be fastened to connector  144  while making contact with bus bar  142 . Insulator  146  (a liner) must cover the head of the connector  144  to ensure electrical and chemical isolation of the fluid. 
       FIG. 21  shows a cross-section of printed heater tube  148  with insulator  150  on surface  152 , bus bar  154 , terminal  156 , and rivet  158 . Rivet  158  is a mechanical attachment that is non-removable and allows for electrical connection of bus bar  154 . Rivet  158  can be, for example, copper, aluminum, stainless steel, titanium, silver, or other appropriate metal. Bus bar  154  overlays rivet  158  at terminal  156 . Insulator  150  on surface  152  prevents rivet from electrically shorting. 
       FIG. 22  shows a cross-section of printed heater tube  160  with surface  162 , bus bar  164 , conductive adhesive  166 , and metal foil  168 . Metal foil  168  is attached to bus bar  164  by conductive adhesive  166 . Metal foil  168  can be, for example, copper, aluminum, stainless steel, titanium, silver, or other appropriate metal. Conductive adhesive  166  is electrically conductive to provide electrical connection between bus bar  164  and metal foil  168 , for example, a conductive epoxy such as MG Chemicals  8331  can be used. 
       FIG. 23  shows a cross-section of printed heater tube  170  with surface  172 , bus bar  174  and solder paste  176 . Bus bar  174  is printed on surface  172  of tube  170 . Solder paste  176  is applied onto bus bar  174  to provide an electrical connection. Solder paste  176  is solder paste suitable for soldering wires such as MG Chemicals  4900 P, and can be made of tin and silver mixed into a flux paste. 
     The disclosed printed heater tubes with PTC heaters are self-limiting heated components that are lightweight and compact on the surface of tubes transporting fluid. 
     Discussion of Possible Embodiments 
     The following are non-exclusive descriptions of possible embodiments of the present invention. 
     A heater tube assembly includes a tube, a bus bar network on the tube, a positive temperature coefficient heater on the tube, a closeout adhesive securing the bus bar network and the positive temperature coefficient heater to the tube, and an outer dielectric layer overlaying the bus bar network and the positive temperature coefficient heater. The bus bar network includes one or more layers of a first additively manufactured conductive ink. The positive temperature coefficient heater comprising one or more layers of a second additively manufactured conductive ink. The positive temperature coefficient heater is electrically connected to the bus bar network. 
     The assembly of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     The tube is a conductive material selected from the group consisting of stainless steel and titanium. 
     The assembly includes an inner dielectric layer separating the bus bar network and the positive temperature from the tube. 
     The tube is a non-conductive material selected from the group consisting of polyetherimide, polyetheretherketone, polyphenylene sulfide, polyimide, ethylene tetrafluoroethylene, polyvinylchloride, polyvinylidene difluoride, and combinations thereof. 
     The tube includes glass fibers, glass spheres, glass hollow spheres, carbon black, carbon nanotubes, or carbon fibers. 
     The assembly includes a liner comprising a material selected from the group consisting of fluoropolymers, fluoroelastomers, silicone, polyolefin, acrylonitrile butadiene rubbers, ethylene propylene diene monomer rubbers, polyurethane, and combinations thereof. 
     The bus bar network comprises at least one hot bus bar and at least one neutral bus bar. 
     The bus bar network comprises a geometric pattern selected from the group consisting of a spiraled pattern, a redundant dual-circuit pattern, a crisscross pattern, or combinations thereof. 
     The first additively manufactured conductive ink is a silver-filled ink. 
     The positive temperature coefficient heater comprises a sheet covering at least a portion of the tube. 
     The positive temperature coefficient heater comprises a single sheet spiraled around the tube. 
     The positive temperature coefficient heater comprises a plurality of bands around the tube in parallel. 
     The width of each of the plurality of bands increases from a first end of the tube to a second end of the tube. 
     The second additively manufactured conductive ink is a positive temperature coefficient ink. 
     The closeout adhesive is a pressure sensitive adhesive or ethylene-vinyl acetate. 
     The outer dielectric layer comprises a material selected from the group consisting of braided stainless steel wire, braided titanium wire, braided aramid, braided dry fiberglass, carbon fiber composites, fiberglass composites, and combinations thereof. 
     The assembly includes one or more protection layers overlaying the outer dielectric layer. 
     A heater tube assembly includes a tube, a bus bar network including at least one hot bus bar and at least one neutral bus bar on the tube, a heater on the tube having a thickness between 0.0001 and 0.010 inches, a closeout adhesive securing the bus bar network and the heater to the tube, and an outer dielectric layer overlaying the bus bar network and the heater. The bus bar network is made of one or more layers of a first additively manufactured conductive ink, and the bus bar network is a geometric pattern selected from the group consisting of a spiraled pattern, a redundant dual-circuit pattern, a crisscross pattern, or combinations thereof. The heater includes a plurality of layers of a second additively manufactured conductive ink, each of the plurality of layers has a thickness of between 1 and 100 microns, and the heater is electrically connected to the bus bar network. 
     A method of making a heater tube assembly includes additively manufacturing one or more layers of a first conductive ink on a tube to create a bus bar, additively manufacturing one or more layers of a second conductive ink on a tube to create a positive temperature coefficient heater overlapping with the bus bar, closing out the bus bar and the positive temperature coefficient heater with an adhesive, and encapsulating the bus bar and the positive temperature coefficient heater with an outer dielectric layer. 
     The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     Additively manufacturing is done with direct printing with extruded ink by micro-dispensing pumps, inkjet printing, or aerosol-gel printing. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by one skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.