Patent Publication Number: US-2021162149-A1

Title: Electronic cigarette with coil-less atomizer

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/304,821, filed on Oct. 17, 2016 and now pending, which is a U.S. National Phase under 35 U.S.C. § 371 of International Patent Application No. PCT/CN2014/076018, filed on Apr. 23, 2014, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The field of the invention is electronic cigarettes. 
     BACKGROUND OF THE INVENTION 
     Electronic cigarettes generally have an atomizer that vaporizes liquid with an electrically heated wire coil. Although heating coil atomizers have achieved significant success, they have several disadvantages. For example, a coil may not be a beneficial geometry for a heating element in certain designs. In addition, coils may be time consuming to assemble into the atomizer, especially smaller size coils. Engineering challenges accordingly remain in providing improved atomizers for electronic cigarettes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, the same element number indicates the same element, in each of the views. 
         FIG. 1  illustrates a prior art atomizer having a coil heating element  100  and a wicking element  200 . 
         FIG. 2  is a top view of a coil-less heating element. 
         FIG. 3  is a top view of a coil-less heating element having coated conductive fibers. 
         FIGS. 4 a  and 4 b    are top views of a coil-less heating element shaped to have different areas of electrical resistance. 
         FIGS. 5 a -5 d    illustrate a different shapes the fiber material felt  2  may adopt in a coil-less heating element. 
         FIGS. 6 a -6 d    illustrate a method of coating conductive fibers to make the coil-less heating element shown in  FIG. 2 . 
         FIGS. 7 a -7 f    illustrate a preparation process of the coil-less heating element shown in  FIG. 4   a.    
         FIG. 8  illustrates a process of modifying the electrical resistance of a coil-less heating element to a desired range. 
         FIG. 9  shows an electronic cigarette having the coil-less heating element of  FIG. 2, 3 , or  4 . 
         FIG. 10( a )  is an enlarged side view of the coil-less heating element of  FIG. 2  in contact with a liquid supplying unit. 
         FIG. 10( b )  is an enlarged side view of the coil-less heating element of  FIG. 3 or 4  in contact with a liquid supplying unit. 
         FIG. 10( c )  is a top cross-sectional view of the coil-less heating element of  FIG. 3  in contact with a liquid supplying unit  16 . 
         FIG. 11( a )  is a side view of a wick winding around a coil-less heating element. 
         FIG. 11( b )  is a side view of a wick winding around a coil-less heating element without contacting the heating section. 
     
    
    
     DETAILED DESCRIPTION 
     In one aspect, a coil-less atomizer has a heating element made of conductive fiber materials. A section of the conductive fibers may be coated with a conductive material to reduce the electrical resistance of the fibers. The conductive fiber material may be shaped to have areas of lesser and greater resistance. The coil-less atomizer need not have a separate wicking element to deliver liquid to the heating element. The coil-less atomizers disclosed can be miniaturized relative to conventional coil atomizers for electronic cigarettes, to provide more compact designs for electronic cigarettes. The reduced size of the atomizer may allow more space in the electronic cigarette for other components. 
     In another aspect, an electronic cigarette includes a coil-less atomizer having a heating element with a first lead, a second lead, and one or more conductive fibers electrically connected to the first and second leads. A section of the fibers forms a heating section. The conductive fibers may further comprise a first and a second conductive sections. The first and the second conductive sections are proximal to the first and second leads, respectively. The first and second conductive sections may have low electrical resistances (e.g., about 1Ω or less) relative to the electrical resistance of the heating section which has a higher electrical resistance (e.g., about 3Ω to about 5Ω, or about 1Ω to about 7Ω). The heating element may be designed to have a desired total electrical resistance of about 3Ω to about 6Ω, or about 1Ω to about 8Ω. When the e-cigarette is switched on, electricity flows between the electrodes through the conductive sections and the heating section. Electric current flowing through the heating element generates heat at the heating section, due to the higher resistance of the heating section. 
       FIG. 2  shows a heating element  4  with the fibers  2  of the heating element mounted on a board  1  between two leads  3  and  3 ′. The board maybe a printed circuit board (PCB) with other electrical components, or it may be a board where the only electrical component is the heating element  4 . The board may be an insulating material that provides sufficient support for the heating element, for example fiberglass. The fibers between the two leads  3  and  3 ′ form the heating section  6 . The board  1  may have a through hole  1 ′ at least partially overlapping with part of the heating section  6  (e.g. overlapping with about 30% to about 100%, about 50% to about 100%, about 90% to about 100%, or about 100% of the heating section). The leads  3  and  3 ′ may be made of any conductive materials. The leads may optionally also be made of conductive material that can transport liquid to the fibers  2 . The fibers  2  may or may not extend laterally beyond the leads  3  and  3 ′. The fibers  2  may be positioned substantially parallel to each other between the leads  3  and  3 ′, wherein the largest angle between a fiber and a line connecting the leads  3  and  3 ′ is about 0 to about 10°, about 0 to about 5°, or about 0 to about 2°. 
     The conductive material used to make leads  3  and  3 ′, which can transport liquid, may be porous electrode materials, including, conductive ceramics (e.g. conductive porous ceramics and conductive foamed ceramics), foamed metals (e.g. Au, Pt, Ag, Pd, Ni, Ti, Pb, Ba, W, Re, Os, Cu, Ir, Pt, Mo, Mu, W, Zn, Nb, Ta, Ru, Zr, Pd, Fe, Co, V, Rh, Cr, Li, Na, TI, Sr, Mn, and any alloys thereof), porous conductive carbon materials (e.g. graphite, graphene and/or nanoporous carbon-based materials), stainless steel fiber felt, and any composites thereof. Conductive ceramics may comprise one or more components selected from the group consisting of oxides (e.g. ZrO 2 , TrO 2 , SiO 2 , Al 3 O 2 , etc.), carbides (e.g. SiC, B 4 C), nitrides (e.g. AlN), any of the metals listed above, carbon (e.g. graphite, graphene, and carbon-based materials), Si, and any combinations and/or composites of these materials. The term “composite” of two or more components means a material obtained from at least one processing of the two or more components, e.g. by sintering and/or depositing. 
     For clarity of illustration,  FIG. 2  schematically shows only a few spaced apart fibers. However, the individual fibers shown may also be fibers in contact. The individual fibers may also be provided in the form of a fabric, where the fibers are in contact with each other to provide transport of liquid by capillary action. The diameters of the fibers may be about 40 μm to about 180 μm, or about 10 μm to about 200 μm. The fibers may have substantially similar or different diameters. The fibers may allow liquid to flow along or though the fibers by capillary action. The fiber materials may be organic fibers and/or inorganic fibers. Examples of inorganic fibers include carbon fibers, SiO 2  fibers, TiO 2  fibers, ZrO 2  fibers, Al 2 O 3  fibers, Li 4 Ti 5 O 12  fibers, LiN fibers, Fe—Cr—Al fibers, NiCr fibers, ceramic fibers, conductive ceramic fibers, and modified fibers thereof. Examples of organic fibers include polymer fibers (e.g. polyaniline fibers, and aramid fibers), organometallic fibers and modifications of these types of fibers. 
     Fibers may be modified to improved surface properties (e.g. better hydrophilic properties to enhance wicking abilities) by exposure/coating/adhering the fibers to compounds having hydrophilic groups (e.g. hydroxide groups). 
     Fiber materials may also be modified to have desired electrical properties. For example the electrical conductivity of the fiber material may be changed by applying one or more modifying materials onto fiber material. The modifying materials may include SnCl 2 , carbon (e.g. graphite, graphene and/or nanoporous carbon-based materials), any of the metals listed above, and/or alloys of them, to increase the electrical conductivity of the fibers, or the fiber material. Certain salts may be used as the modifying material to provide for lower conductivities. The modifying material may be applied to the fibers or fiber material by coating, adhering, sputtering, plating, or otherwise depositing the modifying material onto the fibers or fiber material. 
     In e-cigarette operation using the heating element shown in  FIG. 2 , liquid from a liquid storage component is provided onto the heating section through the leads. As the user inhales on the e-cigarette, vaporized liquid mixes with air flowing through the hole  1 ′ which at least partially overlaps with part of the heating section  6  (e.g. overlapping with about 30% to about 100%, about 50% to about 100%, about 90% to about 100%, or about 100% of the heating section). In an alternative design, liquid may be provided directly onto the heating section via a wick or porous component, rather than through the leads. 
       FIG. 3  illustrates another heating element  4  where the fibers  2  are mounted on a board  1  between two leads  3  and  3 ′. The leads  3  and  3 ′ may or may not be made of a conductive material capable of allowing liquid to reach the fiber materials  2 , as described above relative to  FIG. 2 . The fibers may, or may not, extend laterally beyond the leads. The fibers between the leads  3 , and  3 ′ have a first conductive section  5  electrically connected to a first lead  3 , a second conductive section  5 ′ electrically connected to a second lead  3 ′, and a heating section  6  between the first conductive section  5  and the second conductive section  5 ′. The conductive sections  5  and  5 ′ have lower electrical resistance relative to the heating section  6 . The heating section  6  and leads may have electrical resistances selected so that the total electrical resistance of the heating element  4  is suitable for the operation of an electric cigarette typically operating with DC battery voltage of from about 3 to 5 volts. In this case the heating element  4  may have a resistance of about 3˜5Ω, or about 3.8Ω at room temperature. 
     Electrical resistance of a conductor can be calculated by the following formula: 
     
       
         
           
             
               R 
               = 
               
                 ρ 
                  
                 
                    
                   A 
                 
               
             
             , 
           
         
       
     
     where R is electrical resistance (Ω), I is the length of the conductor, A is the cross-sectional area of the conductor (m 2 ), and ρ is the electrical resistivity of the material (Ωm). 
     The areas of the fibers in relation to the current may not be significantly different between the conductive sections  5  and  5 ′ (A 5 , A 5 ′) and the heating section  6  (A 6 ). However, the electrical resistance of the conductive sections should be lower than the heating section. This may be achieved by selectively modifying the fibers, as described above, to reduce to resistance of the conductive sections, and/or to increase the resistance of the heating section. 
     In  FIG. 3 , the conductive sections  5  and  5 ′ have lengths of L 5  and L 6 . The distance between the leads  3  and  3 ′ is L 4 . Dimensions L 4 , L 5 , L 5 ′, L 6 , L 4 , A 4 , A 5 , A 5 ′, and A 6  can be adjusted along with the selection of the one or more fibers, to achieve a specified electrical resistance. For example, for a heating element with an electrical resistance of about 3˜5Ω, or about 3.8Ω, and L 6  may be about 3 to about 4 mm. L 4 , L 5 , L 5 ′, L 6 , L 4 , A 4 , A 5 , A 5 ′, and A 6  can also be selected according to the size of the electronic cigarette in which the atomizer is to be used. For example, the heating element  6  may be used in an electronic cigarette having a diameter of about 5 mm to about 10 mm. 
     In another embodiment, the different electrical resistances between the conductive and heating sections of the coil-less heating element are achieved by shaping the sections to have different cross-section with the current, as shown in  FIG. 4 . 
       FIG. 4 a    shows a coil-less heating element  4  having a pad of one or more fiber materials  2  electrically connected with two leads  3  and  3 ′ on a board  1 . The fiber material pad  2  has a first conductive sections  5  with an area of A 5 , a second conductive sections  5 ′ with an area of A 5 ′, and a heating section  6  with an area of A 6 . The surfaces of the board  1  that contact the pad  2  may be conductive and electrically connected to the leads  3  and  3 ′. Alternatively, at least a significant portion (e.g. about 70% to about 99.9%, about 80% to about 99.9%, or about 90% to about 99.9%) of the surface of board  1  that contacts the conductive sections  5  and  5 ′ of the pad  2  may be conductive and electrically connected to the leads  3  and  3 ′. Therefore, the areas of the conductive sections A 5  and A 5 ′ may be considered as the cross-section area of the conductive section, and the area of the heating section A 6  may be considered as the cross-section area of the heating section. 
     A 5  and A 5 ′ are significantly larger than A 6  (e.g. 3, 4, 5 or 10 to 20 times larger), so that the heating section  6  has higher electrical resistance than the conductive sections  5  and  5 ′. Although the thickness of the fiber material pad  2  may vary through the same pad, the depth differences have insignificant impact on the conductivities when compared to the area differences between the conductive sections  5  and  5 ′ (A 5 , A 5 ′, respectively) and the heating section  6  (A 6 ). 
     The fiber material pad  2  may adopt any shape having two wider parts linked by a narrow part. For example, the fiber material pad  2  may have a shape of a bow-tie or a dumb-bell (e.g., see.  FIG. 5 a   ). The wider end sections of the bow-tie or dumb-bell form the conductive sections. The narrow middle section of the bow-tie or dumb-bell form the heating section  6 . In another example, the wider parts may be square (e.g., see.  FIG. 5 b   ), rectangle (e.g., see.  FIG. 5 c   ), triangle (e.g., see.  FIG. 5 d   ), or round shape (e.g., see.  FIG. 5 a   ). In certain embodiments, the fiber pad  2  may be a circular felt having a diameter of about 8 mm (L 2 ), and a thickness of about 1 mm. The length of the heating section  6  (L 6 ) may be about 3 to about 4 mm. The width of the heating section  6  (W 6 ) may be about 1 mm. The arc length of the conductive section (I 5 ) may be about 10 mm. The area of the conductive sections (A 5  and A 5 ′) may be about 12 to about 20 mm 2 , respectively. The area of the heating section (A 6 ) may be about 3 to about 4 mm 2 . The area ratio between the conductive section and the heating section is about (A 5 :A 6 ) is about 3, 4, 5 or 10 to 20. 
     The diameters of the fibers of the pad may be about 40 μm to about 180 μm, or about 10 μm to about 200 μm, and the thickness of the fiber pad may be 0.5 to 2 mm or about 1 mm. The fiber materials and modifications described above may also be used on the pad of this embodiment. 
     Referring to  FIGS. 4( a ) and 4( b ) , the leads  3  and  3 ′ may or may not be in contact with the fiber materials  2  at any position outside of the heating section, e.g. at the ends of the fiber materials  2 . The conductive sections  5  and  5 ′ may have an electric resistance of about 0 to about 1Ω; and the heating section  6  may have an electrical resistance of about 3Ω to about 5Ω such that the heating element has an electrical resistance of about 3Ω to about 6Ω. 
       FIGS. 6( a )-6( d )  show a manufacturing process of the coil-less heating element shown in  FIG. 2 , which may include the following steps: 
     a) installing one or more fibers  2  on a board  1  between a first lead  3  and a second lead  3 ′ ( FIG. 6 a   ). The board  1  has a through hole  1 ′ between the first and second leads  3  and  3 ′. 
     b) covering a portion of the fibers between the first lead  3  and the second lead  3 ′ with a mask  8  to provide a masked portion of the fibers  10  and unmasked portions of the fibers  9  and  9 ′ ( FIG. 6 b   ). The through hole  1 ′ at least partially overlaps with part of the masked portion of the fibers  10 . 
     c) sputtering or otherwise applying at least part of the unmasked portions of the fibers  9  and  9 ′ with a modifying agent  7  as described above, with the modifying agent  7  having a lower electrical resistance than the fibers before sputtering ( FIG. 6 c   ). 
     d) removing the mask  8  to provide a heating element as illustrated in  FIG. 2 . 
       FIGS. 7( a )-7( c )  show a manufacturing process of the coil-less heating element shown in  FIG. 4 , which may include the following steps: 
     I) shaping a pad of one or more fiber materials  2  ( FIG. 7 a   ) to a shape having a first section  12 , a second section  12 ′, and a third section  11  ( FIG. 7 b   ) between the first and second sections  12  and  12 ′ ( FIG. 7 b   ), wherein the first and second sections  12  and  12 ′ have areas (A 5 , A 5 ′), respectively larger than that of the third section  11  (A 6 ,  FIG. 7 b   ); and 
     II) installing the shaped pad  2  obtained from step I) on a board  1  between a first lead  3  and a second lead  3 ′ ( FIG. 7 c   ). The narrow section  11  ( FIG. 7 b   ) becomes the heating section  6  ( FIG. 7 c   ); the first and second wider sections  12  and  12 ′ ( FIG. 7 b   ) become the first and second conducting sections  5  and  5 ′ ( FIG. 7 c   ), respectively. 
       FIGS. 7( d )-7( f )  show optional processes that can be further carried out after Step (II), using the following steps: 
     III) covering a portion or all of the heating section  6  with a mask  8  to provide a masked portion of the fibers  10  and unmasked portions of the fibers  9  and  9 ′ ( FIG. 7 d   ). 
     IV) applying at least part of the unmasked portions of the fibers  9  and  9 ′ with a modifying agent  7  as described above, while leaving the masked portion of the fibers untreated, with the modifying agent  7  having a lower electrical resistance than the fibers before sputtering ( FIG. 7 e   ). 
     V) removing the mask  8  to provide a coil-less heating element. 
     The processes as discussed above may be adjusted to provide a heating element with an initial electrical resistance of about lower than desired. The heating element may then be further processed via sintering with the following steps to provide a final electrical resistance of ±0.1Ω of the desired electrical resistance ( FIG. 8 ) via the following steps: 
     i) applying a known voltage (V) to the first lead  3  and the second lead  3 ′, optionally the fiber  2  of the heating element  4  is coated or otherwise treated with a sintering material. As the heating element heats up, the resistance of the fiber  2  and/or the sintering material permanently changes. 
     ii) monitoring the current (I) through the electrical heating element  4 .
         iii) switching the voltage off when the measured current (I) reaches to a current corresponding to the desired electrical resistance of the heating element  4 .       

     The sintering process may be applied in ambient air. Alternatively, the sintering process may be accelerated by adding oxygen to the process. 
       FIG. 9  shows an electronic cigarette  13  having a coil-less atomizer  14  and a liquid supply unit  16 . The coil-less atomizer  14  includes a coil-less heating element  4  as illustrated in  FIG. 2, 3 , or  4 , and an air flow passage  15  through at least part of the atomizer. The heating element  4  has a board  1  having a through hole  1 ′. The electronic cigarette  13  may further include a power source  300 , such as battery or an electrical connector to a power source, a mouth piece  400 , one or more LEDs  500  which light up in operation, and a sensor  600  within a housing  700 . 
     In certain embodiments, the coil-less atomizer  14  may be wickless. The wickless and coil-less atomizer need not include a separate wicking element for conducting a liquid from the liquid supplying unit  16  to the coil-less heating element  4 . Rather, liquid may flow directly from the liquid supplying unit to the fibers, fiber materials or the leads and then to the heating section of the fibers. 
       FIGS. 10( a )-10( c )  illustrate several configurations for a coil-less heating element without a separate wicking element.  FIG. 10 a    shows a side view of a wickless and coil-less atomizer  14 . The coil-less heating element  4  has leads  3  and  3 ′ that conduct liquid to the heating section  6 . The materials of leads  3  and  3 ′ can be conductive materials that can transport liquid, e.g. the porous electrode materials as set forth above, such as porous metals, foam nickel, porous conductive porcelain, stainless steel, and fiber felt. Said materials may be conductive electrodes and transport liquid. The liquid supplying unit  16  is in contact with the leads  3  and  3 ′, which may conduct liquid through pores in the lead material, or via capillary action. No separate wicking element is needed. Although conductive sections are not required for the coil-less heating element  4  to function, the coil-less heating element  4  may include conductive sections as described above. 
       FIG. 10( b )  shows a side view of another wickless and coil-less atomizer  14 . The coil-less heating element  4  has conductive sections (e.g. the one shown in  FIG. 3 ). The liquid supplying unit  16  is in contact with the coil-less heating element  4  on the conducting sections  5  and  5 ′. As the conducting sections  5  and  5 ′ are capable of conducting liquid to the heating section  6 , no wick is required.  FIG. 10( c )  shows a top view of such coil-less and wickless atomizer  14 , wherein the liquid supplying unit  16  adopts a cylindrical shape. However, the liquid supplying unit  16  may have any shape capable of providing contact with one or both of the conducting sections  5  and  5 ′ to supply the liquid flow.  FIGS. 10( b ) and 10( c )  illustrate an embodiment wherein the coil-less heating element  4  has conductive sections as illustrated in  FIG. 3 . A coil-less heating element  4  without conductive sections may also be suitable for the configurations of  FIGS. 10( b ) and 10( c ) , if heating the part of the liquid supply unit  16  that contacts the heating element  4  is acceptable. The wickless configurations of  FIGS. 10( a ) and 10( b )  may also be used with the coil-less heating element shown in  FIGS. 4( a ) and 4( b ) . 
     The coil-less atomizer  14  may also operate using a wick for moving liquid from a liquid source to the coil-less heating element. The wick can be any material that is capable of transporting liquid, such as ceramic fiber, quartz fiber, glass fiber, aramid fiber, common fiber, paper, cotton, porous ceramic, hemp, bamboo yarn, oxidized stainless steel mesh, wire mesh or braid and fabric or non-woven fabric materials. Optionally, zeolite particles may be further included in the wick to facilitate smooth vaporization. 
       FIG. 11( a )  illustrates a side view of a coil-less atomizer using a wick. The coil-less heating element  4  may or may not have a conductive section, and its leads  3  and  3 ′ may or may not be capable of transporting liquid to the heating section  6 . The wick  17  may contact the coil-less heating element  4  at any part, e.g. the heating section  6 , the lead  3  and  3 ′ if applicable, and any combinations thereof. The wick may wind around the heating section and/or the leads  3  and/or  3 ′, or adopt any suitable configuration. 
     For coil-less heating element  4  with conductive sections, the wick  17  may contact the coil-less heating element  4  at any part that can transport liquid to the heating section, e.g. the heating section  6 , the conductive section  5 , the conductive section  5 ′, the leads  3  and  3 ′ when applicable, and any combinations thereof, as shown in  FIG. 11( a ) . Alternatively, the wick  17  may be configured to avoid the heating section  6 , as shown in  FIG. 11( b ) . 
       FIG. 11( b )  shows a design where the coil-less heating element  4  has two conductive sections  5  and  5 ′. The wick may contact the coil-less heating element  4  at one or more parts except the heating section  6 . Thus, the wick may contact the conductive section  5 , the conductive section  5 ′, the leads  3  and  3 ′ when applicable, and any combinations thereof. 
     The heating elements described can be efficiently and conveniently produced in mass production, at low cost. They can also be manufactured with precise control of electrical resistance, leading to better performance when used in an electronic cigarette. The heating elements described may also be made in small sizes providing greater versatility for use in electronic cigarettes. 
     The coil-less atomizer described above may alternatively be described as an electrically conductive liquid wick having leads and a heating section. The heating section may be defined by an area of the wick having higher electrical resistance than the leads, so that electrical current passing through the wick heats the heating section to a high temperature, such as 100 to 350° C., while the leads, which are in contact with a bulk liquid source, remain relatively unheated. The wick, as a single element, heats liquid to generate vapor, and also conveys liquid from the bulk liquid source to the heating location. The electrically conductive liquid wick may be made of fibers, fabric, felt or porous matrix that can conduct both electrical current and liquid through the wick material, and with the electrical resistance of the wick non-uniform to provide a distinct heating section. The heating section and the leads may be integrally formed of the same underlying material, before treating the material to create different electrical resistances between the leads and the heating section. Generally the wick has a single heating section and two leads. 
     The wick may be flat, for example like fabric. The wick may be largely impermeable to air flow. The heating section of the wick may be oriented perpendicular to air flow within an electronic cigarette, with air flowing around the wick, rather than through the wick. Within the atomizing chamber or space, the wick may be perpendicular to the air flow and not loop back on itself, and also not extend longitudinally or parallel to the direction of air flow. In an electronic cigarette having dimensions comparable to a conventional tobacco cigarette (5-10 or 12 mm in diameter and 80-120 mm long), the bulk liquid source contains enough liquid for at least 100 puffs and up to 500 puffs (typically 0.1 to 2 mL). 
     Prophetic Example 1 
     A coil-less atomizer as shown in  FIG. 3 , prepared according to the process illustrated in  FIGS. 6 and 8 . 
     I) Installation and Sputtering ( FIG. 6 ) 
     A plurality of SiO 2  fibers  2  were installed to a circular PCB  1  between two metal leads  3  and  3 ′. The board had a through hole  1 ′ between the two leads  3  and  3 ′. A mask  8  was placed to cover a portion (about 3 to about 4 mm lateral) of the fibers between the leads  3  and  3 ′ to provide a masked portion of the fibers  10  and unmasked portions of the fibers  9  and  9 ′. The through hole  1 ′ overlapped with the masked portion of the fibers  10 . The unmasked portions of the fibers  9  and  9 ′ were sputtered with Cr. The mask  8  was removed to provide a heating element  4  as illustrated in  FIG. 2 . 
     II) Sintering ( FIG. 8 ) 
     The electrical resistance of the heating element  4  is about 2.8 to about 3.2Ω. A voltage of 3.8 V was applied to the leads  3  and  3 ′, and the current (I) through the electrical heating element  4  was monitored. The voltage was switched off when the measured current (I) reached to 1 A, meaning that the electrical resistance of the heating element  4  was 3.8Ω. 
     The sintering process was applied in ambient air, and took about 1 minute. 
     The sintering process may be speeded up by adding oxygen air. 
     III) Coil-Less Atomizer without a Wicking Element ( FIGS. 10 b  and 10 c   ) 
     The coil-less heating element  4  with a desired resistance was prepared as described above. A liquid supply element may contact the conductive sections  5  and  5 ′ and/or the heating section  6  of the heating element  4 . 
     IV) Coil-Less Atomizer with a Wicking Element ( FIGS. 11 a  and 11 b   ) 
     Optionally, a wicking element  17  may be wound around the fibers of the heating element  4  to facilitate liquid flow from the liquid supply element to the heating element  4 . 
     Prophetic Example 2 
     A coil-less atomizer as shown in  FIG. 4 , prepared according to the process illustrated in  FIGS. 7 and 8 . 
     I) Installation and Optional Sputtering ( FIG. 7 ) 
     A carbon fiber felt  2  is shaped by laser cutting or die punching process to provide a shape having two end sections and a middle section. The diameter of the carbon fiber felt  2  is about 8 mm. The thickness of the carbon fiber felt  2  is about 1 mm. The middle section has a length of about 3 to about 4 mm, and a width of about 1 mm. The end sections have an area of more than three or five times of the area of the middle section. The shaped carbon fiber felt  2  is installed on a circular PCB  1  between two metal leads  3  and  3 ′. The board  1  has a through hole  1 ′ between the two leads  3  and  3 ′. The middle section of the carbon fiber felt  2  overlaps with the through hole  1 ′. The component obtained may be used as a heating element in a coil-less atomizer in an electronic cigarette. 
     A second sample heating element is further processed to lower the electrical resistance of the two end sections. As shown in  FIG. 7 , a mask  8  is placed over a portion of the middle section. The through hole  1 ′ overlaps with the masked portion of the fibers  10 . The unmasked portions of the fibers  9  and  9 ′ are sputtered with Cr ++ . The mask  8  is removed to provide a heating element  4  as illustrated in  FIG. 3 . 
     II) Sintering ( FIG. 8 ) 
     The electrical resistance of the heating element  4  is about 2.8 to about 3.2Ω. A voltage of 3.8 V is applied to the leads  3  and  3 ′, and the current (I) through the electrical heating element  4  is monitored. The voltage is switched off when the measured current (I) reached 1 A, meaning that the electrical resistance of the heating element  4  was 3.8Ω. 
     The sintering process is applied in ambient air, and may take about 1 minute. 
     III) Coil-Less Atomizer without a Wicking Element ( FIGS. 10 b  and 10 c   ) 
     The coil-less heating element  4  with a desired resistance is prepared as described above. A liquid supply element may contact the conductive sections  5  and  5 ′ and/or the heating section  6  of the heating element  4 . 
     IV) Coil-Less Atomizer with a Wicking Element ( FIGS. 11 a  and 11 b   ) 
     A wicking element  17  may be wound around the fibers of the heating element  4  to facilitate liquid flow from the liquid supply element to the heating element  4 . 
     As used herein, “about” when used in front of a number means±10% of that number. Reference to fibers includes fiber material (woven or non-woven). Reference to liquid here means liquids used in electronic cigarettes, generally a solution of propylene glycol, vegetable glycerin, and/or polyethylene glycol  400  mixed with concentrated flavors and/or nicotine, and equivalents. References here to fiber materials and capillary action include porous materials, where liquid moves internally through a solid porous matrix. Each of the elements in any of the embodiments described may of course also be used in combination with any other embodiment. Reference to electronic cigarette includes electronic cigars and pipes, as well as components of them, such as cartomizers. 
     The examples and embodiments described herein are intended to illustrate various embodiments of the invention. As such, the specific embodiments discussed are not to be construed as limitations on the scope of the invention. It will be apparent to one skilled in the art that various equivalents, changes, and modifications may be made without departing from the scope of invention, and it is understood that such equivalent embodiments are to be included herein.