Patent Publication Number: US-2023157372-A1

Title: Nicotine electronic vaping device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of U.S. application Ser. No. 16/929,590, filed on Jul. 15, 2020, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Field 
     The present disclosure relates to a nicotine electronic vaping or e-vaping device. 
     Description of Related Art 
     A nicotine electronic vaping or e-vaping device includes a heating element that vaporizes a nicotine pre-vapor formulation to produce a nicotine vapor. 
     A nicotine e-vaping device includes a power supply, such as a rechargeable battery, arranged in the device. The power supply is electrically connected to the heater. The power supply provides power to the heater such that the heater heats to a temperature sufficient to convert the nicotine pre-vapor formulation to a nicotine vapor. The nicotine vapor exits the nicotine e-vaping device through a mouthpiece including at least one outlet. 
     SUMMARY 
     At least one example embodiment provides a nicotine e-vaping device comprising: a nicotine reservoir configured to hold nicotine pre-vapor formulation; a wick configured to draw nicotine pre-vapor formulation from the nicotine reservoir; a heating element configured to heat the nicotine pre-vapor formulation drawn from the nicotine reservoir; a probe wire along a length of the wick, the probe wire being separated from the heating element by the wick; a saturation sensor; and control circuitry. The saturation sensor is configured to: measure at least one electrical characteristic of the wick between the heating element and the probe wire at a first time, the at least one electrical characteristic including a resistance, a capacitance, or both a resistance and a capacitance; and measure the at least one electrical characteristic of the wick between the heating element and the probe wire at a second time, the second time being subsequent to the first time. The control circuitry is configured to cause the nicotine e-vaping device to: calculate a refill rate at which the nicotine pre-vapor formulation flows onto the wick based on the at least one electrical characteristic at the first time and the at least one electrical characteristic at the second time; determine that the refill rate is less than a threshold refill rate; and output a low nicotine pre-vapor formulation alert in response to determining that the refill rate is less than the threshold refill rate. 
     According to at least some example embodiments, the control circuitry may be configured to cause the nicotine e-vaping device to calculate the refill rate based on a difference between the at least one electrical characteristic at the first time and the at least one electrical characteristic at the second time. 
     The control circuitry may be configured to cause the nicotine e-vaping device to: compute a first impedance based on the at least one electrical characteristic at the first time; compute a second impedance based on the at least one electrical characteristic at the second time; and calculate the refill rate based on a difference between the first impedance and the second impedance. 
     The control circuitry may be configured to cause the nicotine e-vaping device to: measure the at least one electrical characteristic of the wick between the heating element and the probe wire at a third time; determine that the at least one electrical characteristic at the third time is greater than or equal to a threshold value; and disable vaping at the nicotine e-vaping device in response to determining that the at least one electrical characteristic at the third time is greater than or equal to the threshold value. 
     The control circuitry may be configured to cause the nicotine e-vaping device to: measure the at least one electrical characteristic of the wick between the heating element and the probe wire at a third time; determine that the at least one electrical characteristic at the third time is greater than or equal to a threshold value; and output a low nicotine pre-vapor formulation alert in response to determining that the at least one electrical characteristic at the third time is greater than or equal to the threshold value. 
     The control circuitry may be configured to cause the nicotine e-vaping device to: measure the at least one electrical characteristic of the wick between the heating element and the probe wire at a third time; compute an impedance of the wick based on the at least one electrical characteristic at the third time; determine that the impedance is greater than or equal to a threshold value; and disable vaping at the nicotine e-vaping device in response to determining that the impedance is greater than or equal to the threshold value. 
     The control circuitry may be configured to cause the nicotine e-vaping device to: measure the at least one electrical characteristic of the wick between the heating element and the probe wire at a third time; compute an impedance of the wick based on the at least one electrical characteristic at the third time; determine that the impedance is greater than or equal to a threshold value; and output a low nicotine pre-vapor formulation alert in response to determining that the impedance is greater than or equal to the threshold value. 
     The nicotine e-vaping device may further include a power supply configured to provide power to the nicotine e-vaping device. 
     The probe wire may be a stainless steel wire. 
     At least one other example embodiment provides a nicotine e-vaping device comprising: an outer housing; an inner tube coaxially positioned within the outer housing; a nicotine reservoir configured to hold a nicotine pre-vapor formulation, the nicotine reservoir positioned between the inner tube and the outer housing; a wick configured to draw nicotine pre-vapor formulation from the nicotine reservoir; a heating element configured to heat the nicotine pre-vapor formulation drawn from the nicotine reservoir; a saturation sensor assembly; and control circuitry. The saturation sensor assembly is configured to measure at least one electrical characteristic between the outer housing and the inner tube at a first time and a second time, the second time being subsequent to the first time. The control circuitry is configured to cause the nicotine e-vaping device to: calculate a refill rate at which the nicotine pre-vapor formulation flows onto the wick based on the at least one electrical characteristic at the first time and the at least one electrical characteristic at the second time; determine that the refill rate is less than a threshold refill rate; and output a low nicotine pre-vapor formulation alert in response to determining that the refill rate is less than the threshold refill rate. 
     The nicotine e-vaping device may further include a probe wire around the outer perimeter of the inner tube, wherein the saturation sensor assembly may be configured to measure the at least one electrical characteristic between the outer housing and the inner tube by measuring the at least one electrical characteristic between the outer housing and the probe wire around the outer perimeter of the inner tube. The probe wire may be a stainless steel wire. 
     The control circuitry may be configured to cause the nicotine e-vaping device to calculate the refill rate based on a difference between the at least one electrical characteristic at the first time and the at least one electrical characteristic at the second time. 
     The control circuitry may be configured to cause the nicotine e-vaping device to: compute a first impedance based on the electrical characteristic at the first time; compute a second impedance based on the electrical characteristic at the second time; and calculate the refill rate based on a difference between the first impedance and the second impedance. 
     The control circuitry may be configured to cause the nicotine e-vaping device to: measure the at least one electrical characteristic of the wick between the heating element and the inner tube at a third time; determine that the at least one electrical characteristic at the third time is greater than or equal to a threshold value; and disable vaping at the nicotine e-vaping device in response to determining that the at least one electrical characteristic at the third time is greater than or equal to the threshold value. 
     The control circuitry may be configured to cause the nicotine e-vaping device to: measure the at least one electrical characteristic of the wick between the heating element and the inner tube at a third time; determine that the at least one electrical characteristic at the third time is greater than or equal to a threshold value; and output a low nicotine pre-vapor formulation alert in response to determining that the at least one electrical characteristic at the third time is greater than or equal to the threshold value. 
     The control circuitry is configured to cause the nicotine e-vaping device to: measure the at least one electrical characteristic of the wick between the heating element and the inner tube at a third time; compute an impedance of the wick based on the at least one electrical characteristic at the third time; determine that the impedance is greater than or equal to a threshold value; and disable vaping at the nicotine e-vaping device in response to determining that the impedance is greater than or equal to the threshold value. 
     The control circuitry may be configured to cause the nicotine e-vaping device to: measure the at least one electrical characteristic of the wick between the heating element and the inner tube at a third time; compute an impedance of the wick based on the at least one electrical characteristic at the third time; determine that the impedance is greater than or equal to a threshold value; and output a low nicotine pre-vapor formulation alert in response to determining that the impedance is greater than or equal to the threshold value. 
     At least one other example embodiment provides a method for detecting depletion of nicotine pre-vapor formulation in a nicotine reservoir of a nicotine e-vaping device, the method comprising: measuring at least one electrical characteristic of a wick between a heating element and a probe wire at a first time, the at least one electrical characteristic including a resistance, a capacitance, or both a resistance and a capacitance; measuring the at least one electrical characteristic of the wick between the heating element and the probe wire at a second time, the second time being subsequent to the first time; calculating a refill rate at which nicotine pre-vapor formulation flows onto the wick based on the at least one electrical characteristic at the first time and the at least one electrical characteristic at the second time; determining that the refill rate is less than a threshold refill rate; and outputting a low nicotine pre-vapor formulation alert in response to determining that the refill rate is less than the threshold refill rate. 
     According to at least some example embodiments the method may further include: measuring the at least one electrical characteristic of the wick between the heating element and the probe wire at a third time; determining that the at least one electrical characteristic at the third time is greater than or equal to a threshold value; and disabling vaping at the nicotine e-vaping device in response to determining that the at least one electrical characteristic at the third time is greater than or equal to the threshold value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various features and advantages of the non-limiting embodiments herein may become more apparent upon review of the detailed description in conjunction with the accompanying drawings. The accompanying drawings are merely provided for illustrative purposes and should not be interpreted to limit the scope of the claims. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. For purposes of clarity, various dimensions of the drawings may have been exaggerated. 
         FIG.  1    is a side view of a nicotine electronic vaping or e-vaping device according to at least one example embodiment. 
         FIG.  2    is a cross-sectional view of an example embodiment of the first section of the nicotine e-vaping device shown in  FIG.  1    along line II-II′. 
         FIG.  3    is an exploded view of an example embodiment of the first section shown in  FIG.  2   . 
         FIG.  4    is a cross-sectional view of an example embodiment of a second section of the electronic vaping device shown in  FIG.  1    along line II-II′. 
         FIG.  5    is an exploded view of an example embodiment of the second section shown in  FIG.  4   . 
         FIG.  6    is a cross-sectional view of an example embodiment of the nicotine e-vaping device shown in  FIG.  1    along line II-II. 
         FIG.  7    is a cross-sectional view of an example embodiment of a saturation circuit assembly. 
         FIG.  8    is a cross-sectional view of another example embodiment of a saturation circuit assembly. 
         FIG.  9    is a cross-sectional view of another example embodiment of a saturation circuit assembly. 
         FIG.  10    is a block diagram of saturation determination circuit arrangement. 
         FIG.  11    is a flow diagram of a method for nicotine pre-vapor formulation depletion detection according to example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Some detailed example embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the example embodiments set forth herein. 
     Accordingly, while example embodiments are capable of various modifications and alternative forms, example embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments. Like numbers refer to like elements throughout the description of the figures. 
       FIG.  1    is a side view of a nicotine e-vaping device according to at least one example embodiment. 
     Referring to  FIG.  1   , in at least one example embodiment, a nicotine electronic vaping device (e-vaping device)  10  includes a replaceable cartridge (or first section)  105  and a reusable battery section (or second section)  110 . The first section  105  and the second section  110  may be coupled together at a connector assembly  115 . 
     In at least one example embodiment, the connector assembly  115  may be a connector as described in U.S. application Ser. No. 15/154,439, filed May 13, 2016, the entire contents of which are incorporated herein by reference thereto. As described in U.S. application Ser. No. 15/154,439, the connector assembly  115  may be formed by a deep drawn process. 
     In the example embodiment shown in  FIG.  1   , the first section  105  includes a first housing  120  and the second section  110  includes a second housing  120 ′. The nicotine e-vaping device  10  includes a mouthpiece  125  at a first end  130 , and an end cap  135  at a second end  140 . 
     According to at least one example embodiment, the first housing  120  and the second housing  120 ′ may have a generally cylindrical cross-section. In other example embodiments, the housings  120  and  120 ′ may have a generally triangular, rectangular, oval, square, or polygonal cross-section along one or more of the first section  105  and the second section  110 . Furthermore, the housings  120  and  120 ′ may have the same or different cross-section shape, or the same or different size. As discussed herein, the housings  120 ,  120 ′ may also be referred to as outer or main housings. 
     Although example embodiments may be described in some instances with regard to the first section  105  coupled to the second section  110 , example embodiments should not be limited to these examples. 
       FIG.  2    is a cross-sectional view of the first section  105  of the nicotine e-vaping device  10  along line II-II in  FIG.  1   .  FIG.  3    is an exploded view of an example embodiment of the first section  105  shown in  FIG.  2   . 
     Referring to  FIGS.  2  and  3   , the first housing  120  extends in a longitudinal direction and an air tube  202  (or chimney) is coaxially positioned within the first housing  120 . 
     A first end portion (e.g., upstream with respect to air flow during vaping) of the air tube  202 , a first nose portion  204  of a first gasket  206  (or seal) is fitted into the air tube  202 . An outer perimeter of the first gasket  206  may provide a seal with an interior surface of the first housing  120 . The first gasket  206  includes a central, longitudinal air passage  208  in fluid communication with the air tube  202  to define an inner passage (also referred to as a central channel or central inner passage)  210 . A transverse channel  212  at a backside portion of the first gasket  206  intersects and communicates with the air passage  208  of the first gasket  206 . The transverse channel  212  enables fluid communication between the air passage  208  and a central air passage  214 , which is discussed in more detail later. 
     A first connector piece  216  is fitted into a first end of the first housing  120 . The first connector piece  216  is part of the connector assembly  115 . 
     The first connector piece  216  is a hollow cylinder with female threads on a portion of the outer lateral surface. The first connector piece  216  is conductive, and may be formed of, or coated with, a conductive material. The female threads (or female threaded section) may be mated with male threads (or a male threaded section) of the second section  110  to connect the first section  105  and the second section  110 . However, example embodiments are not limited to this example embodiment. Rather, the connectors may be, for example, snug-fit connectors, detent connectors, clamp connectors, clasp connectors, or the like. Moreover, the positioning of the male and female connectors may be reversed as desired such that the male connector is part of the first section  105 . 
     A conductive post  218  nests within the hollow portion of the first connector piece  216 , and is electrically insulated from the first connector piece  216  by a gasket insulator  220 . The conductive post  218  may be formed of a conductive material (e.g., stainless steel, copper, or the like) and may serve as an anode portion of the first connector piece  216 . 
     The conductive post  218  defines the central air passage  214 . The central air passage  214  is in fluid communication with the air passage  208  via the transverse channel  212 . The gasket insulator  220  holds the conductive post  218  within the first connector piece  216 . The gasket insulator  220  also electrically insulates the conductive post  218  from an outer portion  222  of the first connector piece  216 . 
     The outer portion  222  of the first connector piece  216  serves as the cathode connector of the first connector piece  216 , and the outer portion  222  is electrically insulated from the conductive post  218  by the gasket insulator  220 . The outer portion  222  may sometimes be referred to herein as a cathode connector or cathode portion. The outer portion  222  may be formed of a conductive material (e.g., stainless steel, copper, or the like). 
     Still referring to the example embodiment shown in  FIGS.  2  and  3   , a second nose portion  224  of a second gasket  226  may be fitted into a second end portion  250  of the air tube  202 . An outer perimeter of the second gasket  226  may also provide a substantially tight seal with an interior surface of the first housing  120 . The second gasket  226  may include a central passage  228  (or channel) disposed between the inner passage  210  of the air tube  202  and the interior of the mouthpiece  125 . Nicotine vapor may flow from the inner passage  210  into a cavity within the mouthpiece  125  through the central passage  228 . 
     The mouthpiece  125  includes at least two outlets  230 , which may be located off-axis from the longitudinal axis of the nicotine e-vaping device  10 . The outlets  230  may be recessed or non-recessed and angled outwardly in relation to the longitudinal axis of the nicotine e-vaping device  10 . The outlets  230  may be substantially uniformly distributed about the perimeter of the mouthpiece  125  so as to substantially uniformly distribute nicotine vapor. 
     The first section  105  further includes a nicotine reservoir  232  configured to store a nicotine pre-vapor formulation and a vaporizer  234 . The vaporizer  234  includes a heating element  236  and a wick  238 . The vaporizer  234  is configured to vaporize nicotine pre-vapor formulation drawn from the nicotine reservoir  232 . In the example embodiment shown in  FIGS.  2  and  3   , the confines of the nicotine reservoir  232  are defined between the first gasket  206 , the second gasket  226 , the first housing  120 , and the air tube  202 . However, example embodiments should not be limited by this example. The nicotine reservoir  232  may contain a nicotine pre-vapor formulation, and optionally a storage medium  232 LD,  232 HD configured to store the nicotine pre-vapor formulation therein. 
     In at least one example embodiment, the storage medium may be a fibrous material including at least one of cotton (e.g., a winding of cotton gauze), polyethylene, polyester, rayon, combinations thereof, or the like. As shown in  FIGS.  2  and  3   , the storage medium  232 LD,  232 HD may include two layers of fibrous material. Each layer may have a different density. The fibers may have a diameter ranging in size from about 6 microns to about 15 microns (e.g., about 8 microns to about 12 microns or about 9 microns to about 11 microns). The storage medium may be a sintered, porous or foamed material. Also, the fibers may be sized to be irrespirable and may have a cross-section which has a Y-shape, cross shape, clover shape or any other suitable shape. In the example embodiment shown in  FIG.  3   , the storage medium includes a low density gauze  232 LD surrounding a high density gauze  232 HD. The high density gauze  232 HD may be positioned between the low density gauze  232 LD and the air tube  202  so that the nicotine pre-vapor formulation is drawn toward the wick  238 . 
     In at least one other example embodiment, the nicotine reservoir  232  may include a filled tank lacking any storage medium and containing only nicotine pre-vapor formulation. 
     In at least one example embodiment, the nicotine reservoir  232  may at least partially surround the inner passage  210  and the air tube  202 . The heating element  236  may extend transversely across the inner passage  210  between opposing portions of the nicotine reservoir  232 . In at least some example embodiments, the heating element  236  may extend parallel to a longitudinal axis of the inner passage  210 . 
     The nicotine reservoir  232  may be sized and configured to hold enough nicotine pre-vapor formulation such that the nicotine e-vaping device  10  may be configured for vaping for at least about 200 seconds. Moreover, the nicotine e-vaping device  10  may be configured to allow each puff to last a maximum of about 5 seconds. 
     As mentioned above, the vaporizer  234  incudes the heating element  236  and the wick  238 . The wick  238  may include at least a first end portion and a second end portion, which may extend into opposite sides of the nicotine reservoir  232 . The heating element  236  may at least partially surround a central portion of the wick  238 . 
     The wick  238  may draw the nicotine pre-vapor formulation from the nicotine reservoir  232  (e.g., via capillary action), and the heating element  236  may heat the nicotine pre-vapor formulation in the central portion of the wick  238  to a temperature sufficient to vaporize the nicotine pre-vapor formulation thereby generating a “vapor.” As referred to herein, a “vapor” is any matter generated or outputted from any nicotine e-vaping device according to any of the example embodiments disclosed herein. 
     In addition to the features discussed herein, in at least one example embodiment of the nicotine e-vaping device  10  may include the features set forth in U.S. Patent Application Publication No. 2013/0192623 to Tucker et al. filed Jan. 31, 2013 and/or features set forth in U.S. patent application Ser. No. 15/135,930 to Holtz et al. filed Apr. 22, 2016, the entire contents of each of which are incorporated herein by reference thereto. In at least one other example embodiment, the nicotine e-vaping device may include the features set forth in U.S. patent application Ser. No. 15/135,923 filed Apr. 22, 2016, and/or U.S. Pat. No. 9,289,014 issued Mar. 22, 2016, the entire contents of each of which are incorporated herein by this reference thereto. 
     In at least one example embodiment, the nicotine pre-vapor formulation is a material or combination of materials that may be transformed into a nicotine vapor. For example, the nicotine pre-vapor formulation may be a liquid, solid and/or gel formulation including, but not limited to, water, beads, solvents, active ingredients, ethanol, plant extracts, natural or artificial flavors, and/or nicotine vapor formers such as glycerin and propylene glycol. In some example embodiments, the nicotine pre-vapor formulation may include tobacco and/or other plant material, which may or may not be mixed with flavorants, nicotine vapor formers, fillers, binders, and/or polymers. The tobacco and/or other plant material may be in the form of leaves, shreds, films, bits, particles, powders, beads, and combinations of these. 
     In at least one example embodiment, the wick  238  may include filaments (or threads) having a capacity to draw the nicotine pre-vapor formulation. For example, the wick  238  may be a bundle of glass (or ceramic) filaments, a bundle including a group of windings of glass filaments, or the like, all of which arrangements may be capable of drawing nicotine pre-vapor formulation via capillary action by interstitial spacing between the filaments. The filaments may be generally aligned in a direction perpendicular (transverse) to the longitudinal direction of the nicotine e-vaping device  10 . In at least one example embodiment, the wick  238  may include one to eight filament strands, each strand comprising a plurality of glass filaments twisted together. The end portions of the wick  238  may be flexible and foldable into the confines of the nicotine reservoir  232 . The filaments may have a cross-section that is generally cross-shaped, clover-shaped, Y-shaped, or in any other suitable shape. 
     In at least one example embodiment, the wick  238  may include any suitable material or combination of materials. Examples of suitable materials may be, but not limited to, glass, ceramic- or graphite-based materials. The wick  238  may have any suitable capillarity drawing action to accommodate nicotine pre-vapor formulations having different physical properties such as density, viscosity, surface tension and vapor pressure. The wick  238  may be non-conductive. 
     In at least one example embodiment, the heating element  236  may include a coil of wire (a heater coil) which at least partially surrounds the wick  238 . The wire used to form the coil of wire may be metal. The heating element  236  may extend fully or partially along the length of the wick  238 . The heating element  236  may further extend fully or partially around the circumference of the wick  238 . In some example embodiments, the heating element  236  may or may not be in contact (or direct contact) with the wick  238 . 
     In the example embodiment shown in  FIGS.  2  and  3   , the heating element  236  is electrically connected to the conductive post  218  via a first electrical lead  240 , and to the outer portion  222  via a second electrical lead  240 ′. Accordingly, the outer portion  222  and the conductive post  218  form respective external electrical connection to the heating element  236 . 
     In at least some other example embodiments, the heating element  236  may be in the form of a planar body, a ceramic body, a single wire, a mesh, a cage of resistive wire or any other suitable form. More generally, the heating element  236  may be any heater that is configured to vaporize the nicotine pre-vapor formulation. 
     In at least one example embodiment, the heating element  236  may be formed of any suitable electrically resistive materials. Examples of suitable electrically resistive materials may include, but not limited to, copper, titanium, zirconium, tantalum and metals from the platinum group. Examples of suitable metal alloys include, but not limited to, stainless steel, nickel, cobalt, chromium, aluminum-titanium-zirconium, hafnium, niobium, molybdenum, tantalum, tungsten, tin, gallium, manganese and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel. For example, the heating element  236  may be formed of nickel aluminide, a material with a layer of alumina on the surface, iron aluminide and other composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required. The heating element  236  may include at least one material selected from the group consisting of stainless steel, copper, copper alloys, nickel-chromium alloys, super alloys and combinations thereof. In an example embodiment, the heating element  236  may be formed of nickel-chromium alloys or iron-chromium alloys. In another example embodiment, the heating element  236  may be a ceramic heater having an electrically resistive layer on an outside surface thereof. 
     Still referring to  FIGS.  2  and  3   , the air tube  202  may include a pair of opposing slots  242 , such that the wick  238  and the first and second electrical leads  240  and  240 ′ or ends of the heating element  236  may extend out from the respective opposing slots  242 . The provision of the opposing slots  242  in the air tube  202  may facilitate placement of the heating element  236  and the wick  238  into position within the air tube  202  without impacting edges of the opposing slots  242  and the coiled section of the heating element  236 . Accordingly, edges of the opposing slots  242  may not be allowed to impact and alter the coil spacing of the heating element  236 , which would otherwise create potential sources of hotspots. In at least one example embodiment, the air tube  202  may have a diameter of about 4 mm and each of the opposing slots may have major and minor dimensions of about 2 mm by about 4 mm. 
     In at least one example embodiment, the heating element  236  may heat nicotine pre-vapor formulation in the wick  238  by thermal conduction. Alternatively, heat from the heating element  236  may be conducted to the nicotine pre-vapor formulation by means of a heat conductive element or the heating element  236  may transfer heat to the incoming ambient air that is drawn through the nicotine e-vaping device  10  during vaping, which in turn heats the nicotine pre-vapor formulation by convection. 
     As shown in  FIG.  3   , the first section  105  may further include a cover tube  244 , a spacer tube  246  and an inner tube  248 . Although not shown in  FIG.  2   , the cover tube  244  may be arranged to surround the portion of the air tube  202  between the heating element  236  and the second nose portion  224 . As with the air tube  202 , the cover tube  244  may extend in the longitudinal direction and may be coaxially positioned within the first housing  120 . The cover tube  244  may cover a portion of each of the opposing slots  242 . 
     The spacer tube  246  may extend in the longitudinal direction and be coaxially positioned within the air tube  202  between the heating element  236  and the conductive post  218 . The inner tube  248  may extend in the longitudinal direction and be coaxially positioned within the spacer tube  246 . Although the cover tube  244 , the spacer tube  246  and the inner tube  248  are shown in  FIG.  3   , one or more of these tubes (e.g., the inner tube  248 ) may be omitted. 
       FIG.  4    is a cross-sectional view of a second section of an example embodiment of the nicotine e-vaping device  10  along line II-II′ of  FIG.  1   .  FIG.  5    is an exploded view of an example embodiment of the second section  110  shown in  FIG.  4   . 
     The second section  110  may be a reusable section of the nicotine e-vaping device  10 , wherein the reusable section may be capable of being recharged by an external charging device. Alternatively, the second section  110  may be disposable. In this example, the second section  110  may be used until the energy from a power supply  402  (described below) is depleted (e.g., the energy fails below a threshold level). 
     Referring to  FIGS.  4  and  5   , according to at least this example embodiment, the power supply  402  includes an anode connection  404  and a cathode connection  406 . Each of the anode connection  404  and the cathode connection  406  may be in the form of one or more electrical leads or wires. The power supply  402  may be a battery. For example, the power supply  402  may be a Lithium-ion battery, or a variant of a Lithium-ion battery, such as a Lithium-ion polymer battery. The battery may either be disposable or rechargeable. 
     The second section  110  further includes a connector piece  408  at a first end of the second section  110 . In the example embodiment shown in  FIG.  4   , the connector piece  408  is a male connector configured to connect to the female first connector piece  216  of the first section  105 . Alternatively, the connector piece  408  may be a female connector configured to connect to a male connector of the first section  105 . 
     In the example embodiment shown in  FIG.  4   , the connector piece  408  includes threads  410  configured to mate with corresponding threads on the first connector piece  216  of the first section  105 . Although illustrated as a threaded connection, according to at least some other example embodiments, the connector piece  408  may be, for example, snug-fit connectors, detent connectors, clamp connectors, clasp connectors, or the like. 
     The cathode connection (connector piece  408 ) of the power supply  402  terminates at, and is electrically connected to, a sensor assembly  424  positioned proximate to a second end of the second section  110 . The sensor assembly  424  will be discussed in more detail later. 
     The anode connection  404  terminates at, and is electrically connected to, a conductive post  412 . The conductive post  412  may serve as the anode portion of the connector piece  408 . The conductive post  412  defines a central passage  414 , which is in fluid communication with one or more side vents  416 . The side vents  416  may be holes bored into the conductive post  412 . The central passage  414  and the one or more side vents  416  allow for puff detection by the sensor assembly (e.g., a puff sensor assembly)  424  resulting from changes in pressure when air is drawn in through air inlets  145 . 
     Although only two side vents  416  and two air inlets  145  are shown in  FIG.  4   , example embodiments should not be limited to this example. Rather, the conductive post  412  may include any number of side vents  416 , and the connector piece  408  may include any number of air inlets  145 . For example, the conductive post  412  may include 4 side vents  416  spaced apart at equal distances around the conductive post  412 . Similarly, the connector piece  408  may include 4 air inlets  145  spaced apart at equal distances around the connector piece  408 . 
     The conductive post  412  further includes an upper portion  418  having an indentation allowing air drawn through the air inlets  145  to flow and/or communicate through the end of the second section  110  into the first section  105  when connected to the second section  110 . 
     The conductive post  412  may be formed of a conductive material (e.g., stainless steel, copper, or the like), and nested within the hollow portion of the connector piece  408 . When the connector piece  408  of the second section  110  is coupled to the first connector piece  216  of the first section  105 , the upper portion  418  (and the conductive post  412 ) physically and electrically connects to the conductive post  218  to allow flow of electrical current from the power supply  402  to the heating element  236 . The electrical connection also allows for electrical signaling between the first section  105  and the second section  110 . 
     Still referring to  FIGS.  4  and  5   , a gasket insulator  420  holds the conductive post  412  within the connector piece  408 . The gasket insulator  420  also electrically insulates the conductive post  412  from an outer portion  422  of the connector piece  408 . The outer portion  422  may be formed of a conductive material (e.g., stainless steel, copper, or the like) and may serve as a cathode portion of the connector piece  408 . 
     As mentioned above, the connector piece  408  includes one or more air inlets  145  configured to communicate ambient air into the connector piece  408 . The air inlets  145  may also be sometimes referred to as vents or air vents. 
     The ambient air drawn into the connector piece  408  may combine and/or mix with air flowing out of the one or more side vents  416  and flow into the first section  105 , when the first section  105  is coupled to the second section  110 . In at least one example embodiment, the air inlets  145  may be bored into the connector piece  408  just below the threads  410  at an angle perpendicular or substantially perpendicular to the longitudinal centerline of the connector piece  408 . 
     The sidewalls of the air inlets  145  may be beveled in order to cause the sidewalls to slope inwards (e.g., to “countersink” the sidewalls at the rim of the air inlets  145 ). By beveling the sidewalls at the rim of the air inlets  145  (as opposed to using relatively sharp edges at the rim of the air inlets  145 ), the air inlets  145  may be less likely to become clogged or partially blocked (due to a reduction in the effective cross-sectional area of the air inlets  145  near the rim of the air inlets  145 ). In at least one example embodiment, the sidewalls of the rim of the air inlets  145  may be beveled (inclined) to be about 38 degrees relative to a longitudinal length (or the longitudinal centerline) of the connector piece  408  and the second housing  120 ′ of the second section  110 . 
     In at least one example embodiment, the air inlets  145  may be sized and configured such that the nicotine e-vaping device  10  has a resistance-to-draw (RTD) in the range of from about 60 mm H 2 O to about 150 mm H 2 O. 
     Referring still to  FIGS.  4  and  5   , as mentioned above, the second section  110  includes a sensor assembly (e.g., a puff sensor assembly)  424 . 
     As shown in  FIG.  4   , for example, the sensor assembly  424  is electrically connected and powered by the power supply  402 . In at least this example embodiment, the sensor assembly  424  includes a sensor (e.g., a puff sensor)  426 , a saturation sensor  427 , and control circuitry  428 . 
     The control circuitry  428  is configured to provide an electrical current and/or electrical signaling to the first section  105 . To this end, the control circuitry  428  is electrically connected to the conductive post  412  (anode portion of the connector piece  408 ) via control circuitry wiring (or lead)  430 , and to the outer (cathode) portion  422  of the connector piece  408  via control circuitry wiring (or lead)  432 . In at least this example, the control circuitry wiring  432  acts as a cathode for the electrical circuit including the sensor assembly  424 . 
     The sensor  426  may be a capacitive sensor capable of sensing an internal pressure drop within the second section  110 . The sensor  426  and the control circuitry  428  may function together to open and close a heater control circuit (not shown) between the power supply  402  and the heating element  236  of the first section  105  when coupled to the second section  110 . In at least one example embodiment, the sensor  426  is configured to generate an output indicative of a magnitude and direction of airflow through the nicotine e-vaping device  10 . In this example, the control circuitry  428  receives the output of the sensor  426 , and determines if (1) the direction of the airflow indicates an application of negative pressure to (e.g., draw on) the mouthpiece  125  (versus positive pressure or blowing) and (2) the magnitude of the application of negative pressure exceeds a threshold level. If these vaping conditions are met, then the control circuitry  428  electrically connects the power supply  402  to the heating element  236  to activate the heating element  236 . 
     In one example, the heater control circuit may include a heater power control transistor (not shown). The control circuitry  428  may electrically connect the power supply  402  to the heating element  236  by activating the heater power control transistor. In at least one example, the heater power control transistor (or heater control circuit) may form part of the control circuitry  428 . 
     According to at least one example embodiment, the sensor assembly  424  may include one or more features set forth in U.S. Pat. No. 9,072,321 to Loi Ling Liu and/or U.S. Patent Application Publication No. 2015/0305410 to Loi Ling Liu, the entire contents of each of which are incorporated herein by reference. However, example embodiments should not be limited to this example. Rather, the control circuitry  428  and the sensor  426  may be separate elements arranged on a printed circuit board, and connected via electrical contacts. Additionally, although discussed herein with regard to a capacitive sensor, the sensor  426  may be any suitable pressure sensor, for example, a Microelectromechanical system (MEMS) including a piezo-resistive or other pressure sensor. 
     As is described in further detail in  FIGS.  7 - 11   , the saturation sensor  427  is connected to the power supply  402  via cathode connection  406  and electrical lead  430  and to the first section  105  via electrical lead  432 . The saturation sensor  427  may be configured to measure one or more electrical characteristics of a saturation circuit included in the first section  105 . According to one or more example embodiments, the saturation sensor  427  may measure a resistance and/or a capacitance of the saturation circuit. From the resistance and/or capacitance, the control circuitry  428  may calculate the impedance of the saturation circuit. In one example, based on the resistance, capacitance and/or impedance, the control circuitry  428  may detect when the nicotine pre-vapor formulation in the nicotine reservoir  232  is becoming depleted (e.g., the amount of nicotine pre-vapor formulation in the nicotine reservoir falls below a first minimum threshold level) and generate an alert accordingly. In another example, the control circuitry  428  may cause the nicotine e-vaping device  10  to disable vaping and/or power off when depletion of the nicotine pre-vapor formulation in the nicotine reservoir is detected (e.g., the amount of nicotine pre-vapor formulation in the nicotine reservoir falls below a second minimum threshold level, which is less than the first minimum threshold level). 
     The control circuitry  428  may include, among other things, a controller. According to one or more example embodiments, the controller may be implemented using hardware, a combination of hardware and software, or storage media storing software. Hardware may be implemented using processing or control circuitry such as, but not limited to, one or more processors, one or more Central Processing Units (CPUs), one or more microcontrollers, one or more arithmetic logic units (ALUs), one or more digital signal processors (DSPs), one or more microcomputers, one or more field programmable gate arrays (FPGAs), one or more System-on-Chips (SoCs), one or more programmable logic units (PLUs), one or more microprocessors, one or more Application Specific Integrated Circuits (ASICs), or any other device or devices capable of responding to and executing instructions in a defined manner 
     In another example embodiment, the control circuitry  428  may include a manually operable switch for an adult vaper to supply power to the heating element  236 . 
     In at least one example embodiment, the control circuitry  428  may limit the time period during which electrical current is continuously supplied to the heating element  236 . The time period may be set or pre-set depending on the amount of nicotine pre-vapor formulation desired to be vaporized. In one example, the time period for continuous application of electrical current to the heating element  236  may be limited such that the heating element  236  heats a portion of the wick  238  for less than about 10 seconds. In another example, the time period for continuous application of electrical current to the heating element  236  may be limited such that the heating element  236  heats a portion of the wick  238  for about 5 seconds. 
     Still referring to  FIGS.  4  and  5   , the sensor assembly  424  is cradled within a sensor holder  434  at the second end of the second section  110 . In at least one example embodiment, the sensor holder  434  may be part of a silicon or rubber gasket. However, example embodiments should not be limited to this example. 
     A heat activation light  436  may also be arranged to the second end of the second section  110 . In the example embodiment shown in  FIG.  4   , the heat activation light  436  may be arranged within the end cap  135 . The heat activation light  436  may include one or more light-emitting diodes (LEDs). The LEDs may include one or more colors (e.g., white, yellow, red, green, blue, or the like). Moreover, the heat activation light  436  may be visible to an adult vaper during vaping, and configured to glow when the power supply  402  supplies electrical current to the heating element  236 . The heat activation light  436  may be utilized for the nicotine e-vaping system diagnostics or to indicate that recharging of the power supply  402  is in progress. The heat activation light  436  may also be configured such that the adult vaper may activate or deactivate the heat activation light  436  for privacy. The heat activation light  436  may be part of, or electrically connected to, the sensor assembly  424  as described in U.S. Pat. No. 9,072,321 to Loi Ling Liu and/or U.S. Patent Application Publication No. 2015/0305410 to Loi Ling Liu. 
       FIG.  6    is a cross-sectional view of an example embodiment of the nicotine e-vaping device shown in  FIG.  1    along line II-II′. 
     In  FIG.  6   , the first section  105  is shown coupled to the second section  110 . The arrows in  FIG.  6    indicate example air flow through the nicotine e-vaping device  10 . 
     Operation of the nicotine e-vaping device  10  to create a nicotine vapor when the first section  105  is coupled to the second section  110  will now be described with regard to  FIG.  6   . 
     Referring to  FIG.  6   , air is drawn primarily into the first section  105  through the at least one of the air inlets  145  in response to application of negative pressure to the mouthpiece  125 . 
     If the control circuitry  428  detects the vaping conditions discussed above, then the control circuitry  428  initiates supply of power to the heating element  236 , such that the heating element  236  heats nicotine pre-vapor formulation on the wick  238  to generate nicotine vapor. 
     The air drawn through the air inlets  145  enters the cavity within the connector piece  408  and passes through the indentation in the upper portion  418  into the central air passage  214 . From the central air passage  214 , air flows through the transverse channel  212 , through the air passage  208 , and then through the inner passage  210 . 
     The air flowing through the inner passage  210  combines and/or mixes with the nicotine vapor generated by the heating element  236 , and the air-nicotine vapor mixture passes from the inner passage  210  into the central passage  228  and then into the cavity within the mouthpiece  125 . From the cavity in the mouthpiece  125 , the air-nicotine vapor mixture flows out of the outlets  230 . 
       FIG.  7    is a cross-sectional view of an example embodiment of a saturation circuit assembly  700 .  FIG.  7    depicts a portion of the first section  105  of the nicotine e-vaping device  10 , enhancing the view of the heating element  236 . In at least an example embodiment, the saturation circuit assembly  700  includes a probe wire  705  extending along the length of the wick  238 , but separate from (not in contact with) the heating element  236 . In various example embodiments, the wick  238  and the probe wire  705  may be shorter or longer than that shown in  FIG.  7   . The probe wire  705  is connected to the first electrical lead  240  via a first probe lead  710 . When the first section  105  is engaged with the second section  110 , the first probe lead  710  electrically connects the probe wire  705  to the power supply  402  in the second section  110 . 
     As mentioned previously and described in more detail below, the saturation sensor  427  may measure at least one electrical characteristic or determine an impedance across at least a portion of the first section  105 . More specifically, for example, the saturation sensor  427  may measure at least one electrical characteristic or determine an impedance across the saturation circuit assembly  700 , connecting the probe wire  705  and the heating element  236  to the first electrical lead  240  and the second electrical lead  240 ′. In various example embodiments, the at least one electrical characteristic may include, but should not be limited to, a resistance, a capacitance, or both. 
     The control circuitry  428  in the second section  140 ′ may determine an impedance associated with the heating element  236  and the probe wire  705  based on the measured electrical characteristic(s), for example, resistance, measured by the saturation sensor  427 . In various example embodiments, the control circuitry  428  may determine a saturation level of the wick  238  based on the impedance or the at least one electrical characteristic. 
     As the electrical characteristic(s) and resulting impedance are indicative (e.g., directly indicative) of the saturation level of the wick  238 , the electrical characteristics and/or impedance may be used to detect depletion of the nicotine pre-vapor formulation in the nicotine reservoir  232  so that undesired nicotine vapor elements will not be generated. In other words, for example, the saturation sensor  427  and measured electrical characteristics may enable detecting of dry wick conditions (also referred to as dry puff conditions), and in turn, depletion of the nicotine pre-vapor formulation in the nicotine reservoir. 
     The probe wire  705  may be made of stainless steel; however, any other conductive metal acceptable to product safety may be used. The saturation sensor  427  may implement any suitable method for determining impedance between the heating element  236  and the probe wire  705 , such as based on a measured resistance, a measured capacitance, or a measured combination of resistance and capacitance. 
     As described below, the saturation circuit assembly  700  is sensitive to both the presence and the amount of nicotine pre-vapor formulation in the wick  238 . For example, when the wick  238  is initially dry, the impedance may have a resistive measurement in excess of about 10 MΩ and a capacitance of about 2 pf. However, once (e.g., within a few seconds) a drop of nicotine pre-vapor formulation (e.g., about 5 mg) is placed on one end of the wick  238 , the resistive measurement may be about 2 MΩ and the capacitance may be about 200 pf. As further nicotine pre-vapor formulation is added, the impedance continues to change, until the wick  238  is saturated. When fully saturated, the wick  238  may have a resistance of about 45 KΩ and a capacitance of about 2200 pf. 
     According to one or more example embodiments, in response to a resistance greater than or equal to about 10 MΩ and/or a capacitance of less than or equal to about 2 pf, the control circuitry  428  may power off or disable vaping at the nicotine e-vaping device  10  by cutting off supply of power to the heating element  236 . Additionally or alternatively, the control circuitry  428  may generate and display a dry wick alert, by illuminating an indicator light on the nicotine e-vaping device  10 . The indicator light may be the heat activation light  436  and may illuminate a particular color or flash when the dry wick alert is generated. In various example embodiments, a separate indicator light may be included on the first housing  120  of the nicotine e-vaping device  10 . 
     One or more example embodiments may provide more accurate resistance and/or capacitance measurements because the saturation circuit assembly  700  is more directly influenced by the amount of nicotine pre-vapor formulation saturating the wick  238  since the wick  238  is in contact with the probe wire  705  and the heating element  236 . 
     Additionally, nicotine pre-vapor formulations include glycerin, propylene glycol, and water, while other constituents are present in smaller quantities. Therefore, the nicotine pre-vapor formulation acts as an electrolyte in the capacitor formed between the heating element  236  and the probe wire  705  (or the first housing  120 , as shown in  FIGS.  8  and  9   ). Therefore, the amount of nicotine pre-vapor formulation present more directly influences the capacitance of the saturation sensor  427 . 
     Since the nicotine pre-vapor formulation is not an insulator, the nicotine pre-vapor formulation allows the passage of electrical current, which can be measured readily to determine a resistance. Both the capacitance and the resistance vary directly with the amount of nicotine pre-vapor formulation on (also referred to as saturation level of) the wick  238 . Either or both may be measured to determine that the amount of nicotine pre-vapor formulation on the wick  238  is decreasing (or has decreased) below a minimum threshold level (e.g., the wick  238  is beginning to dry). The combination of resistance and capacitance may be used to determine the electrical impedance of the wick  238 . 
     When nicotine pre-vapor formulation is heated to generate nicotine vapor, the saturation level of the wick  238  decreases, and additional nicotine pre-vapor formulation flows into the wick  238  from the nicotine reservoir (e.g., via capillary action) to replenish the wick  238 . As a result, a flow rate at which the saturation level of the wick  238  is replenished may be determined. 
     The control circuitry  428  may compare the flow or refill rate with a minimum flow rate threshold to determine whether the nicotine pre-vapor formulation in the nicotine reservoir is becoming depleted. If the flow rate is below the minimum flow rate threshold, the control circuitry  428  determines that the nicotine pre-vapor formulation in the nicotine reservoir is becoming depleted, and may output a corresponding indication or alert to the adult vaper. The indication or alert may be illuminating an indicator light (simply powering on the light or performing a flashing pattern). 
     Calculation of a flow or refill rate for the wick  238  will be discussed in more detail below with regard to  FIG.  11   . 
     Moreover, the electrical characteristics measurements may be performed while the nicotine e-vaping device  10  is operational (e.g., during a puff when power is applied to the heating element  236 ) and may be performed using the first electrical lead  240  and the second electrical lead  240 ′, without the need for an additional third electrical lead from the first section  105  to the second section  110 . 
     While being described within the nicotine e-vaping device  10 , the saturation sensor  427  and the saturation circuit assembly  700  may be implemented on a wick included in paint or ink systems, food systems implementing a wicking of flavoring or other ingredients, a feedback system to increase a wicking refill rate, medical systems to detect saturation of a bandage, etc. Because the saturation sensor  427  and the saturation circuit assembly  700  are sensitive, the described system could be used to detect an increase of a liquid presence or level before the liquid begins to accumulate in a protected area, increasing the various applications of the system. 
       FIG.  8    is a cross-sectional view of another example embodiment of a saturation circuit assembly  800 .  FIG.  8    depicts a portion of the first section  105  of the nicotine e-vaping device  10 , enhancing the view of the heating element  236 . The saturation circuit assembly  800  of  FIG.  8    is similar to the example embodiment shown in  FIG.  7    except that the saturation circuit assembly  800  includes a probe wire  805  around the air tube  202  that is connected to the first electrical lead  240 . In various example embodiments, the probe wire  805  may be connected to the second electrical lead  240 ′. 
     A first probe lead  810  connects one end of the probe wire  805  to the first electrical lead  240 . Additionally, the first housing  120  is connected to the first electrical lead  240  via a first housing lead  820 . The saturation sensor  427  measures a resistance and/or a capacitance between the probe wire  805  and the first housing  120  to determine the amount of nicotine pre-vapor formulation in the nicotine reservoir  232 . Then, as described above, the control circuitry  428  disables the nicotine e-vaping device  10  and/or outputs an alert of an empty, low, or near depleted nicotine reservoir  232  accordingly. In various example embodiments, the saturation circuit assembly  800  may exclude the first housing lead  820  and instead measure the resistance and/or capacitance across the probe wire  805  and the heating element  236 . As mentioned similarly above, the probe wire  805  is configured to circumscribe the air tube  202 . 
       FIG.  9    is a cross-sectional view of another example embodiment of a saturation circuit assembly  900 .  FIG.  9    depicts a portion of the first section  105  of the nicotine e-vaping device  10 , enhancing the view of the heating element  236 . The saturation circuit assembly  900  of  FIG.  9    is similar to the example embodiment shown in  FIG.  8    except that the saturation circuit assembly  900  excludes the probe wire  805 . Instead, the saturation sensor  427  measures a resistance and/or a capacitance across the heating element  236  and the first housing  120  to determine a saturation level of the wick  238 . 
       FIG.  10    is a block diagram of an example embodiment of a saturation determination circuit arrangement. The saturation circuit assembly  700  of  FIG.  7    is electrically coupled to the power supply  402 , the sensor assembly  424 , the saturation sensor  427 , and the control circuitry  428  via various electrical leads (the first electrical lead  240 , the second electrical lead  240 ′, the anode connection  404 , the cathode connection  406 , control circuitry wiring  430  and  432 ), and conductive posts  218  and  418 . The saturation sensor  427  measures a resistance and/or a capacitance across the saturation circuit assembly  700 . The same saturation determination circuit arrangement may be used with the saturation circuit assembly  800  of  FIG.  8    and the saturation circuit assembly  900  of  FIG.  9   . 
     The control circuitry  428  may include a non-volatile memory (not shown) storing impedance thresholds, resistance thresholds, capacitance thresholds, flow or refill rate thresholds, etc. 
       FIG.  11    is a flow diagram illustrating a method for nicotine pre-vapor formulation depletion detection. 
     For example purposes, the example embodiment shown in  FIG.  11    will be discussed with regard to resistance and with regard to the example embodiment shown in  FIG.  7   . However, example embodiments should not be limited to this example. Rather, the control circuitry  428  may perform the method shown in  FIG.  11    based on measured capacitance or impedance of the wick  238 . In one example, the control circuitry  428  may measure capacitance of the wick  238 , which may then be utilized in place of resistance in the method shown in  FIG.  11   . In another example, the control circuitry  428  may measure resistance and capacitance of the wick  238 , which may then be utilized to compute and/or determine an impedance of the wick  238 . The impedance of the wick  238  may then be utilized in place of the resistance in the method shown in  FIG.  11   . Moreover, the control circuitry  428  may perform a similar method based on information obtained from the example embodiments of the saturation circuit assembly shown in  FIGS.  8  and  9   . 
     Referring to  FIG.  11   , at  1000  the control circuitry  428  determines whether vaping conditions exist at the nicotine e-vaping device  10 . According to at least one example embodiment, the control circuitry  428  may determine whether vaping conditions exist at the nicotine e-vaping device  10  based on output from the sensor assembly  424 . In one example, if the output from the sensor assembly  424  indicates application of negative pressure above a threshold at the mouthpiece  125  of the nicotine e-vaping device  10 , then the control circuitry  428  determines that vaping conditions exist at the nicotine e-vaping device  10 . 
     If the control circuitry  428  determines that vaping conditions exist, then at  1100  the control circuitry  428  measures (or causes the saturation circuit assembly  700  to measure) the resistance of the wick  238 . As mentioned above, although the example embodiment shown in  FIG.  11    is discussed with regard to resistance, the control circuitry  428  may measure and/or determine at least one electrical characteristic of the wick  238 , wherein the at least one electrical characteristic may include a resistance and/or a capacitance of the wick  238 , or an impedance of the wick  238 , which is determined based on the resistance and/or capacitance. 
     At  1105 , the control circuitry  428  determines whether the measured resistance of the wick  238  is greater than or equal to a first threshold (e.g., about 10 MΩ). 
     If the measured resistance of the wick  238  is greater than or equal to the first threshold, then at  1110  the control circuitry  428  disables the nicotine e-vaping device  10 . In at least one example embodiment, disabling of the nicotine e-vaping device  10  may include disabling vaping function by cutting off power to the heating element  236  or causing the nicotine e-vaping device  10  to power off (or enter a low power state). The process then terminates. Although not shown, at  1110  the control circuitry  428  may also cause the heat activation light  436  to illuminate in a particular color indicating that the wick  238  is dry and/or the nicotine reservoir  232  is depleted. 
     Returning to  1105 , if the control circuitry  428  determines that the measured resistance is less than the first threshold, then at  1115  the control circuitry  428  determines whether the measured resistance is above a second threshold (e.g., about 2 MΩ). 
     If the measured resistance is above the second threshold (and thus, between about 10 MΩ and about 2 MΩ), then at  1120  the control circuitry  428  generates and displays a nicotine pre-vapor formulation low alert, such as by illuminating the heat activation light  436 . 
     At  1145 , the control circuitry  428  determines whether vaping conditions still exist in the same or substantially the same manner as discussed above with regard to  1000 . 
     If vaping conditions still exist, then the process returns to  1100  and continues as discussed herein. 
     Returning to  1145 , if vaping conditions no longer exist (e.g., the puff has ended), then the process terminates. 
     Returning to  1115 , if the measured resistance is less than the second threshold, then at  1117  the control circuitry  428  determines whether vaping conditions still exist (whether the current puff has ended) in the same or substantially the same manner as discussed above with regard to  1000 . 
     If vaping conditions no longer exist, then at  1130  the control circuitry  428  measures the resistance of the wick  238  at the time when the vaping conditions ceased and again at the end of a threshold time period (e.g., 0.5, 1, or 2 seconds). 
     At  1135 , the control circuitry  428  calculates a refill rate or a flow rate based on the difference between the saturation level (indicated by resistance measurement) at the end of the puff and the saturation level (indicated by resistance measurement) at the end of the threshold time period. In this case, the saturation level may be indicated by the measured resistance level R 0  of the wick  238  at the end of the puff (first time) and the measured resistance level R 1  of the wick  238  at the end of the threshold time period after the puff has ended (second time). In one example, the control circuitry  428  may compute the refill rate as the change in resistance level divided by the length of the threshold time period t TH    
     
       
         
           
             
               ( 
               
                 REFILL_RATE 
                 = 
                 
                   
                     
                       R 
                       0 
                     
                     - 
                     
                       R 
                       1 
                     
                   
                   
                     t 
                     
                       T 
                       ⁢ 
                       H 
                     
                   
                 
               
               ) 
             
             . 
           
         
       
     
     In another example in which impedance is used, the refill rate may be computed as the change in impedance level divided by the length of the threshold time period; that is, 
     
       
         
           
             
               ( 
               
                 REFILL_RATE 
                 = 
                 
                   
                     
                       Z 
                       0 
                     
                     - 
                     
                       Z 
                       1 
                     
                   
                   
                     t 
                     
                       T 
                       ⁢ 
                       H 
                     
                   
                 
               
               ) 
             
             , 
           
         
       
     
     where Z 0  is the impedance of the wick  238  at the end of the puff, and Z 1  is the impedance of the wick at the end of the threshold time period after the end of the puff. 
     In at least one other example embodiment, the control circuitry  428  may calculate the flow or refill rate by monitoring the resistance, capacitance and/or impedance of the wick  238  during a puff to determine a minimum saturation level (e.g., maximum resistance or impedance value) and then when the wick  238  becomes re-saturated (reaches its initial resistance or impedance level). The control circuitry  428  may then compute the flow rate as the amount of re-saturation (difference between the impedance at depletion and re-saturation, which may be indicated by resistance measurements) over the time between when the wick  238  is at the minimum saturation level and when the wick  238  is re-saturated. 
     At  1140 , the control circuitry  428  compares the refill rate computed at  1135  with a minimum refill rate threshold to determine whether the refill rate is less than the minimum refill rate threshold. 
     As the amount of nicotine pre-vapor formulation in the nicotine reservoir  232  decreases, the refill rate for the wick  238  decreases. Thus, the control circuitry  428  may determine that the nicotine pre-vapor formulation in the nicotine reservoir  232  is becoming depleted (falls below a minimum threshold) when the refill rate for the wick falls below a minimum threshold level. 
     If the control circuitry  428  determines that the refill rate is below the minimum threshold at  1140 , then the control circuitry  428  determines that the nicotine pre-vapor formulation in the nicotine reservoir  232  is becoming depleted (is low). Accordingly, the process proceeds to  1120  and continues as discussed herein. 
     Returning to  1140 , if the refill rate is greater than the minimum refill rate threshold, then the process returns to  1100  and continues as discussed herein. 
     Returning to  1117 , if the control circuitry  428  determines that vaping conditions still exist, then the control circuitry  428  continues to monitor output of the sensor assembly  424  to determine when the vaping conditions cease (the puff has ended). Once vaping conditions are no longer present, the process proceeds to  1130  and continues as discussed above. 
     Returning now to  1000  in  FIG.  11   , if the control circuitry  428  determines that vaping conditions are not yet present, then the control circuitry  428  continues to monitor output of the sensor assembly  424  for vaping conditions. Once vaping conditions are detected, the process proceeds to  1100  and continues as discussed above. 
     It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It should be understood that, although the terms first, second, third, or the like, may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. 
     Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing various example embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     The nicotine pre-vapor formulation includes nicotine. In an example embodiment, a flavoring (at least one flavorant) is included in the nicotine pre-vapor formulation. In an example embodiment, the nicotine pre-vapor formulation is a liquid, solid and/or gel formulation including, but not limited to, water, beads, solvents, active ingredients, ethanol, plant extracts, natural or artificial flavors, and/or at least one nicotine vapor former such as glycerin and propylene glycol. 
     In an example embodiment, the at least one nicotine vapor former of the nicotine pre-vapor formulation includes diols (such as propylene glycol and/or 1,3-propanediol), glycerin and combinations, or sub-combinations, thereof. Various amounts of nicotine vapor former may be used. For example, in some example embodiments, the at least one nicotine vapor former is included in an amount ranging from about 20% by weight based on the weight of the nicotine pre-vapor formulation to about 90% by weight based on the weight of the nicotine pre-vapor formulation (for example, the nicotine vapor former is in the range of about 50% to about 80%, or about 55% to 75%, or about 60% to 70%), etc. As another example, in an example embodiment, the nicotine pre-vapor formulation includes a weight ratio of the diol to glycerin that ranges from about 1:4 to 4:1, where the diol is propylene glycol, or 1,3-propanediol, or combinations thereof. In an example embodiment, this ratio is about 3:2. Other amounts or ranges may be used. 
     In an example embodiment, the nicotine pre-vapor formulation includes water. Various amounts of water may be used. For example, in some example embodiments, water may be included in an amount ranging from about 5% by weight based on the weight of the nicotine pre-vapor formulation to about 40% by weight based on the weight of the nicotine pre-vapor formulation, or in an amount ranging from about 10% by weight based on the weight of the nicotine pre-vapor formulation to about 15% by weight based on the weight of the nicotine pre-vapor formulation. Other amounts or percentages may be used. For example, in an example embodiment, the remaining portion of the nicotine pre-vapor formulation that is not water (and not nicotine and/or flavorants), is the nicotine vapor former (described above), where the nicotine vapor former is between 30% by weight and 70% by weight propylene glycol, and the balance of the nicotine vapor former is glycerin. Other amounts or percentages may be used. 
     In an example embodiment, the nicotine pre-vapor formulation includes at least one flavorant in an amount ranging from about 0.2% to about 15% by weight (for instance, the flavorant may be in the range of about 1% to 12%, or about 2% to 10%, or about 5% to 8%). In an example embodiment, the at least one flavorant may be at least one of a natural flavorant, an artificial flavorant, or a combination of a natural flavorant and an artificial flavorant. For instance, the at least one flavorant may include menthol, etc. 
     In an example embodiment, the nicotine pre-vapor formulation includes nicotine in an amount ranging from about 1% by weight to about 10% by weight. For instance, nicotine is in the range of about 2% to 9%, or about 2% to 8%, or about 2% to 6%. In an example embodiment, the portion of the nicotine pre-vapor formulation that is not nicotine and/or the flavorant, includes 10-15% by weight water, where the remaining portion of the nicotine pre-vapor formulation is a mixture of propylene glycol and a nicotine vapor former, where the mixture is in a ratio that ranges between about 60:40 and 40:60 by weight. Other combinations, amounts or ranges may be used. 
     Example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.