PERSONAL ELECTRONIC DELIVERY SYSTEM, ATOMIZER ASSEMBLY, USE THEREOF AND CORRESPONDING PRODUCTION METHOD

Abstract

The present invention relates to a personal electronic delivery system and a method for delivering a delivery fluid to a person. The system according to the invention comprises: a housing having a first end with an inlet (12) and a second end with an outlet (38); a fluid path substantially extending between the inlet and the outlet; a buffer (30) for holding a delivery fluid, and connecting means configured to transfer delivery fluid to the fluid path; and a heater (32) that is provided in, at or close to the fluid path configured for heating the delivery fluid such that at least a part of the delivery fluid atomizes and/or vaporizes in the fluid path, and an energy source (18) configured for providing energy to the heater,

Claims

1. A personal electronic delivery system, comprising: a housing having a first end with an inlet and a second end with an outlet; a fluid path substantially extending between the inlet and the outlet; a buffer for holding a delivery fluid, and connecting means configured to transfer delivery fluid to the fluid path; and a heater that is provided in, at or close to the fluid path configured for heating the delivery fluid such that at least a part of the delivery fluid atomises and/or vaporises in the fluid path, and an energy source configured for providing energy to the heater, wherein the heater comprises a metal conductor that is provided with a porous ceramic layer that is configured to control the atomizing and/or vaporization, and wherein the buffer substantially surrounds the heater, wherein the buffer is provided with openings configured for transferring delivery fluid to the heater.

2. The system according to claim 1, wherein the ceramic layer is deposited on or at the conductor with plasma electrolytic oxidation.

3. The system according to claim 1, wherein the ceramic layer has a thickness in the range of 5-300 μm.

4. The system according to claim 1, wherein the heater comprises a valve metal, preferably titanium.

5. The system according to claim 1, wherein the metal conductor of the heater comprises a spiralled metal wire.

6. The system according to claim 5, wherein the spiralled heater has a central axis that is provided substantially in the longitudinal direction of the fluid path.

7. The system according to claim 1, wherein the ceramic layer is provided with a porosity such that the delivery fluid is transferred from the buffer to the vicinity of the conductor by the ceramic layer.

8. The system according to claim 7, wherein the ceramic layer has a porosity in the range of 10-80%.

9. The system according to claim 1, wherein the openings are configured to enable a venturi effect transferring delivery fluid to the heater.

10. The system according to claim 1, wherein the openings are provided adjacent the heater.

11. The system according to claim 9, wherein the openings are provided in a groove.

12. The system according to claim 1, further comprising a power and/or current increasing circuit configured for providing a power and/or current increase when the heater is switched on.

13. The system according to claim 12, wherein the circuit comprises a super-capacitor.

14. The system according to claim 13, wherein the super-capacitor is connected to a charge-connector configured for connecting the super-capacitor to an external power source for charging.

15. The system according to claim 1, wherein the housing comprises a tube having an inner surface that is at least partly provided with a ceramic layer, and wherein the heater at least partly extends into the tube.

16. An atomizer assembly for a personal electronic delivery system, comprising: a housing having a first end with an inlet and a second end with an outlet; a fluid path substantially extending between the inlet and the outlet; a buffer for holding a delivery fluid, and connecting means configured to transfer delivery fluid to the fluid path; and a heater that is provided in, at or close to the fluid path configured for heating the delivery fluid such that at least a part of the delivery fluid atomises and/or vaporises in the fluid path, wherein the heater comprises a conductor and a porous ceramic layer that is configured to control the atomizing and/or vaporization.

17-18. (canceled)

19. A method for producing a personal electronic delivery system, comprising: providing a housing having a first end with an inlet and a second end with an outlet, wherein a fluid path substantially extends between the inlet and the outlet; providing a buffer for holding a delivery fluid, and providing connecting means configured to transfer delivery fluid to the fluid path; providing a heater in, at or close to the fluid path for heating the delivery fluid such that at least a part of the delivery fluid atomises and/or vaporises in the fluid path, and an energy source configured for providing energy to the heater, wherein providing the heater comprises providing a conductor and a porous ceramic layer that is configured to control the atomizing and/or vaporization.

20. The method according to claim 19, further comprising providing an energy source configured for providing energy to the heater.

21. The method according to claim 19, the step of providing the heater comprises providing a conductor having a ceramic layer.

22. The method according to claim 21, wherein depositing the ceramic layer comprises plasma electrolytic oxidation, and after providing the ceramic layer on one side of the conductor, preferably removing at least a part of the conductor material with the use of electrochemical machining.

23. The method according to claim 19, further comprising the step of providing a power and/or current increasing circuit comprising a super-capacitor.

24. The atomizer assembly according to claim 16, wherein the outlet at the second end of the housing is used for inhaling to provide a subnormal pressure in the fluid path such that ambient air is sucked into the inlet and wherein the heater is capable of atomizing and/or vaporizing at least a part of the delivery fluid and delivering at the outlet.

25. The atomizer assembly according to claim 24, wherein the heater in use reaches a temperature in the range of 50-300° C., preferably 100-200° C., more preferably 120-180° C.

26. A system according to claim 1, wherein the ceramic layer is deposited on or at the conductor with plasma electrolytic oxidation, wherein the ceramic layer is provided with a porosity such that the delivery fluid is transferred from the buffer to the vicinity of the conductor by the ceramic layer, wherein the openings are provided adjacent the heater, and wherein the openings are provided in a groove.

27. The system according to claim 10, wherein the openings are provided in a groove.

Description

[0075] Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof wherein reference is made to the accompanying drawings, in which:

[0076] FIG. 1 shows an E-cigarette according to the invention;

[0077] FIG. 2 A-V shows configurations of the heater element according to the invention;

[0078] FIG. 3 A-B shows a setup of a plasma electrolytic oxidation chamber to produce the heater element of FIG. 2; and

[0079] FIG. 4 shows the Voltage as function of time in the manufacturing of the heater element in the chamber of FIG. 3;

[0080] FIG. 5 shows a heater element according to the invention;

[0081] FIG. 6 A-B shows embodiments of a power/current increasing circuit;

[0082] FIG. 7 shows the resistance of electric heater elements in relation to temperature for titanium and NiCr;

[0083] FIG. 8 shows an alternative embodiment of an E-cigarette according to the invention;

[0084] FIGS. 9-10 show a further preferred embodiment according to the invention; and

[0085] FIG. 11 shows a further preferred embodiment of an atomizer assembly according to the invention.

[0086] E-cigarette 2 (FIG. 1) comprises battery assembly 4 and atomizer assembly 6. In the illustrated embodiment atomizer assembly 6 is disposable. It will be understood that the invention can also be applied to systems with other configuration and that the illustrated embodiments is for exemplary purposes only. Details, including connections between components, that are known to the skilled person from conventional E-cigarettes have been omitted from the illustration to reduce the complexity of the drawing.

[0087] Battery assembly 4 comprises housing 8, (LED) indicator 10 with air inlet 12, air flow sensor 14, circuit 16 and battery 18. Air from inlet 12 is provided with air path 20 to sensor 14. Circuit 16 comprises an electronic circuit board that is connected to the relevant components of system 2. Battery 18 can be a rechargeable battery including the required connections to enable recharging. Battery assembly 4 has air inlet 22 and connector 24 to connect battery assembly to atomizer assembly 6.

[0088] Atomizer assembly 6 comprises housing 26 with air path 28 that is surrounded with buffer 30 comprising the E-liquid (for example a mixture of glycerol, propylene glycol, nicotine). Buffer material may include wicking material such as silica, cotton, etc.) or buffer 30 can be provided by other buffer means. In the illustrated embodiment heater element 32 is provided at or around the perimeter of air path 28. In one of the preferred embodiments heater element 32 comprises a wire of metallic titanium core 34 with ceramic titanium oxide layer 36 around metallic core 34. The E-liquid is absorbed and/or adsorbed in the porous ceramic layer. Wire 32 is heated by passing an electric current through metallic titanium core 34. Wire 32 is heated and the E-liquid is evaporated and/or atomized The mixture is provided to outlet 38 of air path 28 at mouth piece 40.

[0089] Heater 32 achieves an improved temperature control and the ability to control the amount of E-liquid evaporating in time by varying the characteristics of the porous ceramic layer 36, such as thickness, size of pores, and porosity.

[0090] When inhaling at outlet 38 an under pressure in air paths 20, 28 is achieved. Air is sucked in through inlets 12, 22. Sensor 14 detects an air flow and circuit board 16 sends an indication signal to indicator 10. Battery 18 provides electricity to heater 32 that heats the E-liquid supplied from buffer 30 and vaporizes and/or atomizes the liquid such that a user may inhale the desired components therein.

[0091] In the illustrated embodiment heater 28 has its longitudinal axis substantially parallel to air path 28. It will be understood that other configurations are also possible according to the invention.

[0092] Optionally, heater 28 is surrounded by buffer 30. The surface area of buffer 30 is preferably provided with (small) openings that are filled with E-liquid from the buffer. Capillary action transfers liquid from the openings to heater element 30. The openings are preferably made in a metal tube-like surface of buffer 30 to prevent burning.

[0093] Several embodiments of a heater element according to the invention will be illustrated. Heater 42 (FIG. 2A) comprises a resistance heating material 44a as conductor and porous ceramic layer 44b. Heater 46 (FIG. 2B) is wound as a solenoid 48 (FIG. 2C) similar to heater 28 as illustrated in FIG. 1. In an alternative configuration heater 50 is configured as a toroid (FIG. 2D), or flat coil 51 (FIG. 2E), or flat spiral 52 (FIG. 2F), for example.

[0094] In the illustrated embodiment of system 2 buffer 30 is provided around air path 28 and heater 32 (see also FIG. 2G). In an alternative embodiment liquid reservoir 54 is provided inside the solenoid of heater 56 (FIG. 2H).

[0095] A further alternative configuration includes heater 58 (FIG. 21) wound as toroid structure with liquid passing through the inside of the toroid structure and air flow passing around the toroid structure. Another alternative configuration includes heater 60 (FIG. 2J) formed as a flat coil. Also, heater 62 (FIG. 2K) may comprise a layer of path of resistance heating material 64 as conductor on coated porous ceramic layer 66, or alternatively heater 68 may comprise a conductor layer 70 with coated porous ceramic elements or spots 72 provided thereon (FIG. 2L). Alternatively, heater 74 comprises conductor layer 76 and ceramic layer 78 (FIG. 2M), and optionally additional ceramic spots 80 (FIG. 2N). Another embodiment comprises porous ceramic layer 82 with conductor 84 wound in a spiral configuration (FIG. 20).

[0096] Other embodiments include conductor tube 86 with static mixing form 86a coated with ceramic layer 88 (FIG. 2P and 2Q). As a further alternative, conductor 90 is a tube (FIG. 2R) with a ceramic layer 92. Tube 90a can be filled with liquid on the inside and having air flow on the outside (FIG. 2S) or tube 90b has air flow on the inside and liquid buffer on the outside (FIG. 2T). Optionally, a ceramic layer is provided on the inside and the outside of tube 90. Also, tube 90 may comprise a number of smaller tubes or wires 94 with resistance heating material and ceramic material (FIG. 2U). A further alternative configuration (FIG. 2V) involves resistance heating metallic foam or sponge 96 coated with porous ceramic material 98.

[0097] The disclosed embodiments for heater 32 provide examples of heaters according to the invention that can be applied to systems 2.

[0098] Heater elements according to the invention are preferably manufactured using plasma electrolytic oxidation. As an example, for illustrative reasons only, below some manufacturing methods for some of the possible configurations for the heater element according to the invention will be disclosed.

[0099] In a first embodiment of the heater element, plasma electrolytic oxidation of titanium wire that is directly connected to an anode is performed.

[0100] For the plasma electrolytic oxidation use is made of a plasma electrolytic chamber 102 (FIG. 3A). Work piece 104 is connected to the anode 106. Work piece 104 is clamped/fixed between two screws or clamps 108 that are connected to the ground/earth (anode 104) of a power supply. In the illustrated embodiment cathode 110 comprises stainless steel honeycomb electrode 112 that, in use, is placed at close distance above work piece 104. Electrolyte 114 flows between electrode 112 and anode 106, and effectively flows upwards through honeycomb electrode 112 together with the produced oxygen and hydrogen. Electrolyte effluent 116, together with the hydrogen and oxygen, is then cooled and optionally returned to chamber 102. In the illustrated embodiment the temperature of electrolyte 114 increases from around 11° C. entering plasma electrolytic oxidation chamber 102 to 25° C. exiting chamber 102 and is then cooled off using a heat exchanger (not shown).

[0101] In the illustrated chamber 102 two power supplies (Munk PSP family) are connected in series: one of 350 Volt and 40 Ampere and a second of 400 Volt and 7 Ampere resulting in a maximum of 750 Volt and 7 Ampere with resulting maximum power of 5.25 kW. The power supplies can be connected directly to anode 106 and cathode 110 resulting in direct current (DC) operation of the plasma. An optionally added switching circuit provides the option to operate the plasma with DC pulses. The frequency of the pulses can be set between DC and 1 kHz and different waveforms can be chosen (block, sine, or triangle). Plasma electrolytic oxidation is preferably performed in a pulsed current mode with a frequency (on-off) of about 1000 Hz, preferably with the current set at a fixed value and the voltage increases in time as a result of growing of the porous oxide layer. Current between 1 and 7 Ampere can be used to produce a ceramic layer.

[0102] To produce a heater element according to the invention, in chamber 102 titanium wire 202 (FIG. 3B) is placed as work piece 104 on top of a titanium plate 204 that is connected to the stainless steel anode. Optionally, the anode is directly connected to wire 202. The electrolyte comprised 8 g/l NaSiO3*5H.sub.2O and 15 g/l (NaPO3).sub.6. Titanium wire is used made from titanium grade 1, with a diameter of 0.5 mm and 60 cm in length. The wire is coiled and connected to the anode. A potential higher than 500 volts is applied between the anode and cathode resulting in micro arc discharges on the surface of the titanium wire. On the surface of the wire, the metallic titanium is oxidized to titanium oxide with addition of silicates and phosphates from the electrolyte. The metallic layer is converted to a porous ceramic layer containing titanium oxides, phosphates and silicates. This results in a heater element 302 (FIG. 5) according to the invention.

[0103] Current increasing circuit 402 (FIG. 6A) comprises battery 404, trafo 406, heater element 408 and (super) capacitor 410. Other components in circuit 402 include diode 412, resistance 414, switch 416 responding to inhaling, transistor 418. It will be understood that components in circuit 402 can be replaced with other components and/or additional components can be applied. For example, alternative circuit 420 (FIG. 6B) comprises battery 422, heater element 424, capacitor 426, switch 428, resistor 430 and diode 432.

[0104] When starting to inhale capacitor 410, 426 supplies additional current to heater element 408, 424 to accelerate the temperature increase of heater element 408, 424 and to start atomizing and/or vaporizing almost immediately. Preferably, the heater element is of a titanium material that exhibits a relatively low resistance at room temperature and a higher resistance at an increased temperature thereby enabling a fast response time to the activation signal.

[0105] In a presently preferred embodiment the conductor of the heater element is made of NiCr and preferably of Titanium. The resistance of Titanium (FIG. 7) increases more rapidly with temperature as compared to NiCr. This is illustrated with the linear relation for NiCr (y=0.0011x+2.164) as compared to the linear relation for Titanium (y=0.0104x+1.5567) defining the linear relation of the measured resistances at specific temperatures.

[0106] In a further embodiment of E-cigarette 502 (FIG. 8) heater 32 is supplied with energy through connector 504 from super capacitor 506. Capacitor 506 is charged via external connector 508. Capacitor 506 can be charged (semi)-directly and/or indirectly. Such indirect charging can be performed in connection with cigarette box 510 having cigarette storage compartment 512 and battery compartment 514 with battery 516. In a charging state charge connector 518 contacts connector 508 and super capacitor 506 is being charged. In the illustrated embodiment battery 516 is rechargeable through connector 520.

[0107] In aforementioned preferred embodiments of the system according to the invention, the electronic cigarette comprises two main parts, a first part with a battery with an airflow switch and electronic control equipment for the correct operation of an electronic cigarette, and a second part with a cartridge capable of containing the e-liquid, heating element and parts for the transportation of e-liquid onto the heating element. Cartridge 602 (FIG. 9-10) comprises metallic tube 604, in the illustrated embodiments of stainless steel, with eight holes 606 of about 0.25 mm diameter situated about 2.75 mm from the beginning A of the tube that in use is closest to the mouth piece of the electronic cigarette. In the illustrated embodiment tube 604 is about 29.1 mm in length with an outer diameter of about 4 mm and wall thickness of about 0.3 mm Ceramic tube 608, preferably of zirconium oxide, is provided inside metallic tube 604 at a position about 2.5 mm from openings with a length of about 22 mm, an outer diameter of about 3.4 mm and a wall thickness of about 0.35 mm.

[0108] Ceramic coated titanium heating element 610 is placed in the metallic tube 604 with holes 606. Heating element 610 is preferably made of a titanium wire (grade 1) coated with a ceramic layer and wound as a solenoid. The diameter of the titanium wire with the ceramic layer is about 0.25 mm, the total length of the wire used in the heating element is about 90 mm having about ten closely spaced windings 612 with a diameter of about 2.2 mm, and a total length of heating element 610 of about 1.4 mm Heating element 610 is placed inside metallic tube 604 such that the first windings are positioned in ceramic tube 608 preventing heating element 610 to contact metallic tube 604.

[0109] Metallic tube 604 with holes 606 is pressed into a screw cap with connector(s) (not shown) and electrical insulator 618 on side A, and into an end cap (not shown) on the other side. Metallic housing 614, preferably a tube of stainless steel, extends between the screw cap and the end cap, with the tube having a length of about 3.8 mm, diameter of about 9.2 mm and wall thickness of about 0.2 mm The space, room or compartment 616 between outer metallic tube 614 and inner metallic tube 604 with holes 606 can be filled with e-liquid. For example, the e-liquid comprises about 60% vegetable glycerin, about 30% propylene glycol and about 10% containing nicotine, flavoring and water. The ratio between nicotine, flavoring and water can be adjusted to the preferred amount.

[0110] The screw cap of cartridge 602 is connected to the battery of the electronic cigarette thereby connecting the positive and negative poles of the battery to the positive and negative connector of heating element 610. This enables an electric current to flow from the positive pole to the negative pole through the titanium wire to increase the temperature of the titanium wire by joule heating. The electric current is controlled by the flow switch that is activated by the user. In use, air flows through metallic tube 604 with holes 606 and e-liquid is transported towards heating element 610. By increasing the temperature of heating element 610, e-liquid evaporates in the air flow and the evaporated e-liquid is transported to the user.

[0111] In an alternative embodiment cartridge 620 (FIG. 10) is provided with similar components with the exception that holes 606 are provided in groove 622.

[0112] It will be understood that components of cartridges 602, 620 can be combined in further embodiments. Cartridges 602, 620 and alternative embodiments can be used in electronic cigarettes 2, 502 and other embodiments thereof.

[0113] Atomizer assembly 702 (FIG. 11) comprises housing 704. At end 706 housing 704 is provided with end ring 708 that is preferably pressed in housing 704, and seal 733. End cap 710 is pressed in ring 708. Housing 704 comprises buffer or reservoir 712 and metal tube 714. Flow path 716 extends through tube 714. Reservoir 712 is positioned around outer surface 718 of tube 714. In the illustrated embodiment inner surface 720 of tube 714 is provided with ceramic layer 722. Tube 714 further comprises heater element 724. Openings 726 in tube 714 enable transport of fluid from reservoir 712 towards heater element 724. In the illustrated embodiment tube 714 has eight openings 726 with a diameter of about 0.2 mm It will be understood that other dimensions and shapes can also be envisaged in accordance with the present invention. At end 728 housing 704 is provided with connector 730. Connector 730 with opening(s) 731 comprises seal 732 and screw thread 734. Edge or stop 736 of connector 730 is used for positioning tube 714. In addition, stop 736 prevents leakage of liquid from reservoir 712. In the illustrated embodiment connector 730 is manufactured from brass material. Optionally, connector 730 comprises (separate) connector part 738 having screw thread 734. Assembly 702 further comprises ring 740 with opening(s) 741. Rubber ring 742 separates connector 730 from metal pin 744. First leg 746 of heater element 724 is connected to pin 744. Second leg 748 of heater element 724 is connected to connector 730 and/or ring 740 thereof.

[0114] It will be understood that other configurations of the legs and/or other components can be envisaged in accordance with the present invention, including combining different elements in a single part and/or separating a part into several sub-parts.

[0115] Three experiments were done: 1) 0.5 Ampere for 15 minutes, 2) 1 Ampere for 15 minutes and 3) 2 Ampere for 15 minutes. The mass and diameter of the wire was measured before and after plasma electrolytic oxidation. The wire was placed in water for 5 minutes and the mass was measured as an indication of the amount of water adsorbed on the wire. The voltage as a function of time of the three different current settings can be seen in FIG. 4, and some further material information before and after oxidation is presented in Table 1.

TABLE-US-00001 TABLE 1 Material information Weight (mg) 1 2 3 Before PEO (mg) 525.49 529.82 After PEO (mg) 528.37 539.42 548.71 After heating (mg) 528.09 539.23 547.67 After 5 min in water (mg) 675.7 692.23 705.42 Thickness (μm) 36 71 113 Volume geads (ml) 0.15 0.15 0.16 Volume oxide layer (ml) 0.45 0.51 0.59 Porosity (%) 32.71 29.87 26.73
Ceramic wires were manufactured at different process conditions, including with 5 Ampere (wire 1) and 1 Ampere (wire 2) for processing time of an hour. The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Thickness of ceramic layer porosity and adsorption of two ceramic titanium wires Time + Ceramic current thickness Porosity Adsorption Resistance Wire 1 1 hr @ 5 A 55 μm 45% 21 μl 1.4 Ω Wire 2 1 hr @ 1 A 30 μm 50% 13 μl 1.3 Ω [0116] Wire 1: Before plasma electrolytic oxidation (PEO) [0117] L=0.5 m, D=0.500 mm, R=1.2Ω, R.sub.calculated=2.44 Ω/m, Adsorption (water)=4 μl [0118] Wire 1: After PEO (5 A for 60 minutes) [0119] L=0.5 m, D=0.610 mm, R=1.3-1.4Ω, Adsorption (water)=21 μl, Porosity=44% [0120] Wire 2: Before PEO: [0121] L=0.5 m, D=0.500 mm, V=9.8 e−8 m.sup.3, m=4.2992 e−4 kg, ρ=4379 kg/m.sup.3 [0122] Wire 2: After PEO (1 A for 60 minutes) [0123] L=0.5 m, D=0.5610 mm, V=1.236 e−8 m.sup.3, m=4.512 e−4 kg, ρ=3650 kg/m.sup.3, m.sub.oxide layer=2.13 e−5 kg, V.sub.oxide layer=2.56 e−8 m.sup.3, M.sub.estimate without porosity=4.452 e−5 kg, Porosity=50%, Calculated adsorption=12.8 μl

[0124] It will be understood that for alternative wires other conditions would apply. For example, for a wire having a diameter of 0.1 mm R.sub.calculated=61 Ω/m. Such wire with a length of 6.5 cm will give a resistance of 4Ω. With an oxide thickness of 100 μm an amount of 1.3 μl is adsorbed. 150 μm gives 3.1 μl and 200 μm gives 5.4 μl.

[0125] The experiments illustrate the manufacturing possibilities of the heater element for the system according to the present invention. Further experiments have been conducted to produce other configurations for the heater. In one such further experiment a metal foil, preferably an aluminium foil, was used as starting material on which a porous metal (aluminium) oxide layer is provided, preferably in a plasma electrolytic chamber that is described earlier. Table 3 shows measured values of plasma electrolytic oxidation with constant current at 5 ampere for 9 minutes. Aluminium foil of 13 μm thickness was oxidized with a resulting thickness of aluminium oxide of 13 μm and Table 4 shows the reproducibility of the process. Both tables show voltage, current, temperature of electrolyte going in the plasma electrolytic oxidation chamber (Tin) and going out the plasma electrolytic oxidation chamber (Teff) for constant current of 5 A.

TABLE-US-00003 TABLE 3 t min. Voltage V Current A Tin ° C Teff ° C. 0.167 434 5 0.5 447 5 1 461 5 2 476 5 10.1 18.8 4 487 5 10.9 20.4 6 499 5 11.3 21.4 9 515 5

TABLE-US-00004 TABLE 4 t min. Voltage V Current A Tin ° C. Teff ° C. 0.167 435 5 0.5 448 5 1 460 5 2 474 5 11.3 19.7 4 488 5 6 495 5 8 505 5
Table 5 shows the voltage and current for plasma electrolytic oxidation of aluminium foil at constant current of 2 A. Result was a 13 μm thick aluminium oxide layer.

TABLE-US-00005 TABLE 5 Voltage and current of plasma electrolytic oxidation with constant current of 2 A. t min. Voltage V Current A 1 380 2 2 415 2 3 429 2 4 437 2 5 443 2 6 448 2 7 452 2
Table 6 shows the voltage and current of the plasma electrolytic oxidation of aluminium foil with pulsed constant current of 1 kHz at 5 Ampere.

TABLE-US-00006 TABLE 6 Voltage and current of pulsed constant current of 1 kHz T min. Voltage V Current A 0.167 470 5 0.5 485 5 1 491 5 2 502 5 4 514 5 6 523 5

[0126] In a further experiment, plasma electrolytic oxidation was used to provide a porous, flexible and elastic ceramic layer of >70 μm on titanium foil. Plasma electrolytic oxidation grows a titanium oxide layer which is known to be ceramic (TiO.sub.2). Electrolyte was used with 8 g/l Na.sub.2SiO.sub.3*5H.sub.2O (Natrium metasilicate pentahydrate) and 15 g/l (NaPO.sub.3).sub.6 (Natrium hexametaphosphate). The electrolyte is pumped into the reaction chamber to act as the electrolyte and as a coolant. Titanium foil was used from titanium grade 2 with a thickness of 124 μm. In the manufacturing process the voltage increases as a function of time. This increase signifies an increased resistance and can possibly be explained by the growth of the titanium oxide (TiOx) layer. A thicker TiOx layer acts like an insulating layer between the metal and electrolyte. The resulting Voltage development in time can be seen in Table 7.

TABLE-US-00007 TABLE 7 Voltage and current as function of time for production of ceramic layer on titanium foil with plasma electrolytic oxidation Time min. Voltage V Current A 0.166667 435 6 0.5 510 6 1 540 6 2 551 6 3 553 6 4 554 6 5 556 6 6 556 6 7 557 6 10 557 6

[0127] The resulting foil structure can be processed further involving electrochemical machining. For example, use can be made of dissolution of Titanium grade 2 to make perfect squared shaped channels. With electrochemical machining (ECM) Titanium grade 2 is locally dissolved in a very controlled manner until the ceramic layer is reached. The finished result has to be well defined channels with squared edges and no residue on top of the ceramic layer. The ECM process is used with a cathode with the inverse shape of the product placed on top of a Titanium plate that serves as the anode. A potential is placed between the cathode and anode causing the anode to dissolve. Electrolyte concentration is 5 M NaNO.sub.3. Current density can be varied from 20-150 A/cm.sup.2. The best results were realized with current densities of >60 A/cm.sup.2. Current is operated in a pulsed mode with the time the current is on and off can be varied. Best results were realized with on/off ratio of 16-80 and pulse on from 0.05 until 10 ms and pulse off from 1 ms until 160 ms. This additional processing step may also be applied to other configurations for the heater.

[0128] In a presently preferred embodiment the heater element is made from a titanium wire, or less preferably from NiCr wire. FIG. 7 shows the resistance of electric heater elements in relation to temperature for both materials. As mentioned earlier the use of titanium for the heater element is beneficial.

[0129] The above described experiments illustrate the possibility to manufacture the different configurations of the heater element and to implement such configuration in an E-cigarette, for example. The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, wherein the scope of which many modifications can be envisaged.