Nanotextured Airflow Passage

Abstract

A texturing of the surface of a post wick air flow passage is employed to create a hydrophobic surface upon which e-liquid droplets can form and be deposited. Due to the hydrophobic nature of the surface, the droplets will not remain or cling to the surface, and will instead either roll or slide to the bottom. This surface texturing is of a fine enough scale to decrease the wettability of the surface and provide the hydrophobicity of the surface. The texturing can be achieved through molding or through a secondary process that introduces the desired texture to an existing post wick air flow passage.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This is the first application for the instant invention.

TECHNICAL FIELD

This application relates generally to a textured element within a pod for use with a vaporizer, and more particularly to a post wick air flow passage for use in conjunction with an electronic cigarette or vaporizer having a textured surface to decrease the wettability of the surface of the post wick air flow passage.

BACKGROUND

Electronic cigarettes and vaporizers are well regarded tools in smoking cessation. In some instances, these devices are also referred to as an electronic nicotine delivery system (ENDS). A nicotine based liquid solution, commonly referred to as e-liquid is atomized in the ENDS for inhalation by a user. In some embodiments, e-liquid is stored in a cartridge or pod, which is a removable assembly having a reservoir from which the e-liquid is drawn towards a heating element by capillary action through a wick. In many such ENDS, the pod is removable, disposable, and is sold pre-filled.

In some ENDS, a refillable tank is provided, and a user can purchase a vaporizable solution with which to fill the tank. This refillable tank is often not removable, and is not intended for replacement. A fillable tank allows the user to control the fill level as desired. Disposable pods are typically designed to carry a fixed amount of vaporizable liquid, and are intended for disposal after consumption of the e-liquid. The ENDS pods, unlike the aforementioned tanks, are not typically designed to be refilled. Each pod stores a predefined quantity of e-liquid, often in the range of 0.5 to 3 ml. In ENDS systems, the e-liquid is typically composed of a combination of any of vegetable glycerine, propylene glycol, nicotine and flavorings. In systems designed for the delivery of other compounds, different compositions may be used.

In the manufacturing of the disposable pods, different techniques are used for different cartridge designs. Typically, the pod is a plastic piece created through injection molding and contains a wick that allows e-liquid to be drawn from the e-liquid reservoir to an atomization chamber. In the atomization chamber, a heating element in communication with the wick is heated to encourage aerosolization of the e-liquid. The aerosolized e-liquid can be drawn through a defined air flow passage towards a user's mouth.

FIGS. 1A, 1B and 1C provide front, side and bottom views of an exemplary pod 50. Pod 50 is composed of a reservoir 52 having a post wick air flow passage 54, and an end cap assembly 56 that is used to seal an open end of the reservoir 52. End cap assembly has wick feed lines 58 which allow e-liquid stored in reservoir 52 to be provided to a wick (not shown in FIG. 1). To ensure that e-liquid stored in reservoir 52 stays in the reservoir and does not seep or leak out, and to ensure that end cap assembly 56 remains in place after assembly, seals 60 can be used to ensure a more secure seating of the end cap assembly 56 in the reservoir 52. In the illustrated embodiment, seals 60 may be implemented through the use of o-rings.

Atop reservoir 52 is a mouthpiece 68. In the space between pod 50 and mouthpiece 68 is a space in which mixing of the vapour and air can take place. As illustrated, post wick air flow passage 54 can widen as it approaches the mouthpiece 68 to create a larger space in which mixing can take place. Within mouthpiece 68 are apertures to allow the air flow to pass from pod 50 to the user's mouth. To assist in the mitigation of spitback (which will be discussed below), a spitback absorption pad 66 can be introduced into the void between the top of reservoir 52 and the mouthpiece 68. Spitback absorption pad 66 allows droplets and condensation to be absorbed to some extent.

As noted above, pod 50 includes a wick that is heated to atomize the e-liquid. To provide power to the wick heater, electrical contacts 62 are placed at the bottom of the pod 50. In the illustrated embodiment, the electrical contacts 62 are illustrated as circular. The particular shape of the electrical contacts 62 should be understood to not necessarily germane to the function of the pod 50.

Because an ENDS device is intended to allow a user to draw or inhale as part of the nicotine delivery path, an air inlet 64 is provided on the bottom of pod 50. Air inlet 64 allows air to flow into a pre-wick air flow passage through end cap assembly 56. The pod 50 has an air flow path that extends through the pre-wick air flow passage, an atomization chamber and then through post wick air flow passage 54.

FIG. 2A illustrates a cross section taken along line A in FIG. 1B. This cross section of the device is shown with a complete (non-sectioned) wick 70 and heater 72. End cap assembly 56 resiliently mounts to an end of post wick air flow passage 54 in a manner that allows an air flow path extending from air inlet 64 into pre-wick air flow passage 76, atomization chamber 74 and post wick air flow passage 54. Within atomization chamber 74 is both wick 70 and heater 72. When power is applied to contacts 62, the temperature of the heater 72 increases and allows for the volatilization of e-liquid that is drawn across wick 70.

Typically the heater 72 reaches temperatures well in excess of the vaporization temperature of the e-liquid. This allows for the rapid creation of a vapor bubble next to the heater 72. As power continues to be applied to heater 72 the vapor bubble increases in size, and reduces the thickness of the bubble wall. At the point at which the vapor pressure exceeds the strength of the surface tension, the bubble will burst and release a mix of the vapor and the e-liquid that formed the wall of the bubble. The e-liquid is released in the form of aerosolized particles and droplets of varying sizes. These particles are drawn into the air flow and into post wick air flow passage 54 and towards the user.

FIG. 2B shows a cross section of pod 50 along section line B as shown in FIG. 2A. Between end cap assembly 56 and reservoir 52 is shown o-ring 60 which provides a seal and prevents removal of the end cap assembly 56. Post-wick air flow passage 54 is centrally located, and flanked on either side by wick feed lines 58.

User experience of an ENDS is related to a number of factors including the delivery of nicotine and the flavor compounds in the e-liquid. The size of the droplets entrained by the airflow is associated with a number of different experiences. Flavor compounds are best experienced by smaller particle sizes. Larger particles are less likely to impart flavour, and are associated with other negative experiences including an effect referred to as spitback.

Spitback is a term used to refer to the result of a large particle being entrained in the air flow and delivered with high velocity to the user. In different applications and different devices, there is a droplet threshold above which droplets are known to be associated with user complaints about spitback. In one example, in an ENDS device, droplets over 5 μm in diameter are typically considered to be the cause of user complaints about spitback. This threshold may vary from device to device. The mitigation of spitback can be achieved through the control of the size of the droplets entrained in the air flow.

In some conventional ENDS, a mouthpiece 68 that sits atop the pod 50 can be used to modify the path of the airflow exiting air flow passage 54. Because the droplets in questions are larger droplets, they tend to have greater momentum than the more desirable droplets. By controlling the placement of apertures in the mouthpiece, larger droplets can be kept from ingestion by the user.

When the user stops drawing on the device, airflow through pod 50 ceases. In embodiments in which heater 72 is controlled through a pressure sensor, power to the heater 72 also stops when the user stops drawing on the device. This leaves aerosol rich air within the post wick air flow passage 54. The e-liquid suspended in the air will begin a condensing process as it moves away from the heat source. To allow for greater differentiation, the term aerosol rich air will be used to connote air that has been filled with aerosols and other droplets before a condensation phase begins. When the condensation phase begins, reference will be made to a vapor rich air, a term that will encompass the droplets of varying sizes, including the aerosol sized droplets, and the vapor itself. Typically, condensation will begin where the vapor is already coldest, which will typically be along the edges of post wick air flow passage 54. The walls of post wick air flow passage 54 are typically cooler than the middle of the passage 54 because on the other side of the wall of the post wick air flow passage 54 is the reservoir full of e-liquid. This relatively large mass of e-liquid has not been subjected to heating during the atomization process and is thus typically at approximately the ambient temperature. Even as e-liquid levels decrease, the portion of the post wick air flow passage 54 that is not in contact with the e-liquid is the furthest portion of the passage from the heater 72.

As condensate forms, it typically takes the form of large droplets on the sidewalls of post wick air flow passage 54. Other large droplets may be deposited on the sidewalls of post wick air flow passage 54 during normal usage of the device as mechanisms to prevent delivery of large droplets will result in the deposition of the large droplets on surfaces like the surface of post wick air flow passage 54. It should be noted that as the various forms of droplets (deposited, formed from condensate, and any other form) accumulate on the surface of post wick air flow passage 54, they are still subject to gravity, and have a tendency to roll down towards wick 70 and atomization chamber 74. This tendency is countered by the static friction and viscous drag forces acting to resist droplets beginning to move, which in effect leads to droplets that either do not move after forming or only move slowly and under particular circumstances. These forces may only be overcome when the size of the droplet exceeds a threshold.

A typical usage pattern of an ENDS involves a user drawing on the device for a period of time, waiting and then drawing again on the device. This cycle may repeat a number of times. This may not give sufficient time for droplets to have cleared post wick air flow passage 54. In some situations, droplets may also be pinned making it unlikely that they will clear the post wick air flow passage 54. The airflow through passage 54 can re-entrain the droplets and increase the likelihood that they will be considered spitback. This effect can also occur when a user stops using the ENDS and picks it up later for use.

To assist in the clearance of droplets from the walls of post wick air flow passage 54, a number of solutions have been suggested. Surface coatings, especially those that would reduce surface friction have been suggested. Hydrophobic coatings such as polytetrafluoroethylene (PTFE) can be used to create a more slick surface which would allow any droplets to run down the surface of post wick air flow passage 54 more quickly than they otherwise would. This solution comes at the cost of a more complex manufacturing process. In many embodiments, pod 50 is a low cost, disposable part. The cost and complexity of coating post wick air flow passage 54 is relatively high due to the small size of the passage (in some embodiments having a diameter of approximately 2 mm).

Another proposed solution is described in U.S. Pat. No. 10,159,284 to Dickens. This patent teaches the application of a surface finish to increase the wettability of the walls of the air channel. Increasing the wettability to a sufficient extent is thought to encourage condensate to coat the surface of the channel, making it difficult for droplets to form and be re-entrained in an airflow. It has been suggested that the increased wettability of the walls with respect to the e-liquid reduces the contact angle of the condensate, which makes any liquid coating the walls to be less likely to detach and become re-entrained in the air flow.

This surface texturing can be explained through what is referred to as the Wenzel model, which defines contact angles for liquids on rough surfaces. FIG. 3A illustrates a droplet 80 resting on an untextured surface 77. The surface tension of the droplet 80 tries to keep the droplet 80 with a minimal surface area. The interface between the droplet 80 and surface 77 is easy to measure as it is a straight line. As shown in FIG. 3B, a textured surface 78 has both high and low points, the high points being separated from each other by low points. Although shown here as a regular repeating pattern, it should be understood that high points need not be either evenly distributed or equally tall. When a liquid droplet 80 is placed on textured surface 78, the surface tension of the liquid is insufficient to hold the droplet shape, and the low points of surface 78 will fill with the liquid from droplet 80. The increased wettability can be understood as the droplet 80 having more contact with surface 78 as the droplet engages the entire textured surface. When force is exerted upon droplet 80, including gravity, it will seek a level and will spread out as shown in FIG. 3C. This leads to a greater portion of the surface 78 being coated with the liquid of droplet 80. Given a sufficiently large surface 78, droplet 80 will spread into a film. This makes re-entrainment of the droplet in an airflow, such as would be experienced in an ENDS pod, more difficult.

FIG. 3D illustrates the placement of droplet 80 on a surface 78 that is textured to increase its wettability, in a vertical orientation. With a vertical surface 78, it is important to understand some of the forces acting upon droplet 80. Gravity, represented by line g acts to pull on the droplet 80. Resisting the gravitational pull is force vector R, representing a sum of a number of other forces including, but not limited to, surface tension of the droplet acting to minimize the surface area (which acts to prevent the droplet from spreading out), friction, and a viscous drag. These forces act to resist distortion or movement of the droplet 80. The force applied by gravity is sufficient to cause a distortion of the droplet 80, as shown in FIG. 3E, while the increased wettability of surface 78 prevents the droplet 80 from rolling down. Instead the droplet 80 expands in length and forms a film on surface 78. Those skilled in the art will appreciate that on an untextured surface, the resistive and gravitational forces can, depending on the material of the wall and the makeup of the e-liquid, be largely matched, resulting in droplets that can form and remain largely unmoving on the surface.

In an ENDS pod such as pod 50, the accumulation of e-liquid within a post wick air flow passage 54 will continue through the life of the pod. As these droplets of e-liquid form a film the surface area of the exposed e-liquid will increase. This increases the exposure of the e-liquid to oxygen and can result in oxidation of the e-liquid which may manifest as a discoloration of the film which provides an aesthetically unpleasant appearance.

Another issue arises with the edges of surfaces that have been textured to increase their wettability. With respect to the pod 50 of FIG. 1, there are two common locations for the surface texturing to end, the first is at the top of end post wick air flow passage 54 and the other is where post wick air flow passage 54 has a more pronounced expansion. In the first scenario, the surface texturing will aid in creating a film of e-liquid that covers the entirety of the surface of interior post wick air flow passage 54. Although this may have an immediate reduction in the production of spitback associated with droplets on the surface of the post wick airflow passage 54, the placement of spitback absorption pad 66 may become an issue. If the pad 66 is sufficiently close to the edge of the textured portion of post wick air flow passage 54, the film of e-liquid may come in contact with spitback absorption pad 66. This will result in absorption pad 66 absorbing the liquid forming the film until it saturates. This reduces the effectiveness of absorption pad 66, and over time will result in absorption pad 66 no longer being able to serve the purpose of absorbing droplets of e-liquid. Thus the mitigation of spitback caused by the texturing of the surface of post wick air flow passage 54 may lead to the reduction of the effectiveness of another spitback mitigation feature.

In the second scenario, only part of post wick air flow passage 54 is textured. The transition between the textured and non-textured regions is of interest. As discussed above, one location for this transition is the “elbow” where the post-wick air flow path 54 begins widening. This transition location has been observed to be prone to the formation or accumulation of droplets. One possible explanation for this phenomenon is that above the elbow, droplets that form have a tendency to roll or slide down the wall, while below the elbow droplets tend not to roll and instead are spread into a film Droplets that move towards the interface are unlikely to keep rolling, and instead will encounter a relatively high barrier to continue rolling. When they do push past the interface, droplets will be drawn into the film, but this is not an instantaneous process. Accordingly, droplets will tend to form at the boundary. These droplets may increase with size to a certain extent as other droplets roll or slide into them. These droplets have the same problem as droplets in the previous examples, in that they can be entrained in the airflow and delivered to the user as spitback.

Each of the spitback mitigation techniques described above may have some effect on the presence of spitback, however none of these techniques have been successful in completely eliminating spitback, which remains a problem to many users.

It would therefore be beneficial to have a mechanism to further mitigate spitback.

SUMMARY

It is an object of aspects of the present invention to obviate or mitigate the problems of the above-discussed prior art.

Surface texturing has been previously employed to increase the wettability of the interior of a post wick air flow passage. This can reduce the availability of droplets on the internal face, or wall, of the post wick air flow passage. However, as discussed above, it may have disadvantages. Surface texturing of the post wick air flow passage can be used to decrease the wettability of the surface of the post wick air flow passage.

In accordance with a first aspect there is provided a pod for use in a vaporizing system, such as an electronic nicotine delivery system. The pod comprises a heater and a post wick air flow passage The heater allows for atomization of an atomizable liquid stored within a reservoir. The post wick air flow passage has a wall, at least a portion of the wall has a surface texture. The surface texture causes a decreased wettability of the textured portion of the wall with respect to the atomizable liquid in comparison to the wettability of the wall without the texture. As a result, at least a portion of the post wick air flow passage has decreased wettability with respect to the atomizable liquid than it would have if it didn't have a texture.

In one embodiment, the atomizable liquid is an e-liquid comprising at least one of propylene glycol, vegetable glycerine, nicotine and a flavoring.

In an embodiment, the heater is located within an atomization chamber in communication with the post wick air flow passage. In an optional embodiment, the pod further comprises a wick within the atomization chamber, in fluid communication with the reservoir and in contact with the heater. The wick draws the atomizable liquid from the reservoir towards the heater.

In some embodiments, the surface texture is a texturing of a material from which the wall is formed. In one optional embodiment, the surface texture is sufficiently fine to result in an interaction between the atomizable liquid and the portion of the wall to be governed by Cassie-Baxter equations.

In another embodiment, the portion of the wall comprises a coating deposited upon a substrate of the wall. In one optional embodiment, the coating has a texture sufficiently fine to result in an interaction between the atomizable liquid and the coating to be governed by Cassie-Baxter equations. Optionally, a surface texturing has been applied to the coating. In another embodiment, the coating is comprised of one of glass and a polymer. In some embodiments, the surface texture is defined by the coating and the substrate. In another embodiment, the coating is one of a plurality of coatings, and the surface texture is defined by the plurality of coatings. The surface texture may be a result of different overlapping coatings, and may be defined by the portions where one of the coatings is not present.

In one embodiment, the surface texture creates a surface that is hydrophobic to the atomizable liquid. In another embodiment, the post wick air flow passage and the reservoir are integrally formed.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments will now be described in detail by way of example only with reference to the following drawings in which like elements are described using like reference numerals to the greatest extent possible:

FIG. 1A is a front view of a pod of the prior art with a partially cutaway mouthpiece;

FIG. 1B is a side view of the pod of FIG. 1A;

FIG. 1C is a bottom view of the pod of FIG. 1A;

FIG. 2A is a cutaway view of the pod of FIG. 1B along section line A, without the mouthpiece;

FIG. 2B is a cutaway view of the pod of FIGS. 1A and 2A along section line B;

FIG. 3A is an illustration of a droplet resting on an untextured surface;

FIG. 3B is an illustration of a droplet on a regularly textured surface;

FIG. 3C is an illustration of the spreading of droplet of FIG. 3B on the regularly textured surface with after force has been applied to the droplet;

FIG. 3D is an illustration of forces acting upon the droplet of FIG. 3B;

FIG. 3E is an illustration of forces acting upon the droplet of FIG. 3C;

FIG. 4 is a cutaway view of a pod according to an embodiment of the present invention;

FIG. 5 is a cutaway view of the pod of FIG. 4 along line B;

FIG. 6 is a cutaway view of an alternate embodiment of a pod having a vortex generator;

FIG. 7 is a cross section view of the pod of FIG. 6 along line C;

FIG. 8A is an illustration of a droplet on a nano-textured surface; and

FIG. 8B is an illustration of the droplet of FIG. 8A on the nanotextured surface after force has been applied to the droplet.

DETAILED DESCRIPTION

In the instant description, and in the accompanying figures, reference to dimensions may be made. These dimensions are provided for the enablement of a single embodiment and should not be considered to be limiting or essential. Disclosure of numerical range should be understood to not be a reference to an absolute value unless otherwise indicated. Use of the terms about or substantively with regard to a number should be understood to be indicative of an acceptable variation of up to ±10% unless otherwise noted.

Although presented below in the context of use in an electronic nicotine delivery system such as an electronic cigarette (e-cig) or a vaporizer (vape) it should be understood that the scope of protection need not be limited to this space, and instead is delimited by the scope of the claims. Embodiments of the present invention are anticipated to be applicable in areas other than ENDS, including (but not limited to) other vaporizing applications.

Creating a surface that is less likely to allow droplets of e-liquid to adhere to the surface addresses many issues associated with spitback caused by the formation or deposition of droplets within the post wick air flow passage. This can be thought of as trying to provide a more slippery surface to the e-liquid droplets. This increased slipperiness allows any droplets on the surface of the post wick air flow passage wall to be quickly shed. This can be achieved by sufficiently reducing the wettability of the post wick air flow passage wall.

FIG. 4 is a cross section of a pod 100 with a post wick air flow passage 104 having a reduced wettability. Pod 100 that is generally similar in structure to the prior art pod discussed above. Pod 100 comprises a reservoir 102 having a post wick air flow passage 104, an end cap 106 and a mouth piece 118. The end cap 106 has wick feed lines 108 allowing e-liquid within the reservoir 102 to be absorbed by wick 120. End cap 106 occludes the open end of reservoir 102 and prevents e-liquid stored in the reservoir 102 from leaking. To prevent leakage, and to hold end cap 106 in reservoir 102, resilient seals 110 (which in some embodiments may be O-rings) can be used. Electrical contacts 112 provide an electrical connection to the ENDS device and provide a connection between the heater 122 and the power source within the ENDS device. Air inlet 114 leads to a pre-wick air flow passage 126, which leads into atomization chamber 124. Within atomization chamber 124 are heater 122 and wick 120.

E-liquid is drawn from reservoir 102 into wick 120. Wick 120, in the illustrated embodiment can draw e-liquid from both its sides, and through capillary action will saturate across its entire length. Heater 122 will, as discussed above, cause vaporization of e-liquid that is on its surface during use. This vaporization will result in a bubble of e-liquid forming and expanding until the vapor pressure inside the bubble exceeds the strength of the surface tension of the bubble, and then the bubble will rupture, releasing e-liquid vapor and droplets of varying sizes. Because the heating of heater 122 is typically activated by the user drawing on the device, the vapour and droplets will be entrained in an airflow that traverses pod 100. In the illustrated embodiment, this will go from air inlet 114 through pre-wick air flow passage 126, atomization chamber 124 and then through post wick air flow passage 104 towards the user. Mouthpiece 118 sits atop reservoir 102, and in the space between them is spitback absorption pad 116.

As discussed above, after use, condensation can occur within the post wick air flow passage 104. But, in contrast to prior art implementations, the surface of post wick air flow passage 104 has a texture designed to decrease the wettability with respect to the e-liquid.

The textured surface can be created through a number of different techniques including use of a mold including a sufficiently fine texture, and the application of a texturing to the existing surface. In other embodiments, a layer of a texturable surface can be applied to the surface of the post wick air flow passage. In one such example, a layer of glass or a layer of a polymer could be deposited within the post wick air flow passage in a first step to a process, and then the deposited layer could then be textured through any of a number of processes including one or more of etching, use of a plasma torch and abrasion. In another embodiment, a layer of a coating, including a layer of some polymers, can be applied that already has sufficient texturing. In other embodiments, the texture can be created through the application of one or more coatings that partially cover the surface of the wall. The areas of coverage adjacent to the areas of no coverage create a change in the topology of the surface wall which can create the required surface texturing.

As an example of one process, to apply a coating that could be used, a thin layer of a nanostructured glass can be applied to the post wick air flow passage 104. To create the nanostructured glass, hardmasks can be applied to the surface of post wick air flow passage 104, and etching can be used (making judicious use of patterned photoresist compounds) to create the texture. One example of such a process is outlined in U.S. Pat. No. 9,120,669 to Choi. In another example, a plasma spraying process could be used to deposit a structure with a nanotextured surface. Those skilled in the art will appreciate that many other such techniques can be used including the application of fluorochemical treatments on structured surfaces. Where the post wick air flow passage 104 is formed of a metal, a texturing process using pulsed lasers can be used to create the textured surface.

In another embodiment, if the pod 100 is created through a process such as injection molding, the mold used to create the pod 100 can have a texture so that the post wick air flow passage 104 has a surface texture that reduces the wettability of the passage 104 in comparison to an untextured post wick air flow passage 104 made of the same material.

While discussions about surface textures previously discussed increasing the wettability of a surface, it has been observed that if a sufficiently fine surface texture is applied the wettability is decreased, and the surface can become hydrophobic. This is similar to the effect of a lotus leaf to droplets of water. Droplets of liquid form to a shape that minimizes their surface area. In a vacuum, droplets will tend to form spherical droplets to minimize the surface area of the droplet. On surfaces, the droplet will form a flattened spheroid. With a nanotextured surface to decrease the wettability, the droplet will tend to be more spherical because of the reduced contact area with the surface. The wetting of a surface that comes into contact with the droplet is a function of the adhesion between the surface and the droplet. Conventional texturing increases the effective surface with which the droplet interacts, and thus increases the adhesion. However, a sufficiently fine structure, herein referred to as a nanotextured surface, will have gaps between high points on the surface sufficiently small that the droplet will not enter the gaps. This reduces the overall surface area that is in contact with the droplet, resulting in an overall reduction in the adhesion between the surface and the droplet. This reduction in adhesion creates a decrease in the wettability of the surface of post wick air flow passage 104.

This decreased wettability encourages droplets to remain as droplets instead of forming a film, and when subject to forces such as gravity, will encourage the droplet to either roll or slide down the surface of post wick air flow passage 104. By rolling or sliding down the surface of post wick airflow passage 104, droplets will clear the post wick air flow passage 104 and either encounter the spitback absorption pad 116 or enter the atomization chamber 124, where it may fall into wick 120.

Because droplets that encounter the nanotextured surface do not form a film, many of the boundary conditions of the surface do not occur or are mitigated. At the boundary between a nanotextured surface and a conventional surface, droplets will form on either side. Droplets that run down from a conventional surface to a nanotextured surface will not necessarily sit at the boundary. Instead, they will run down the nanotextured surface, likely at an increased speed, which may cause them to break into smaller droplets. Droplets running from a nanotextured surface to a conventional surface will simply be deposited on the conventional surface and will move on the surface as they otherwise would. If there is an absorption pad in contact with the nanotextured surface, the pad 116 will absorb droplets it encounters, but will do so on an individual basis instead of as a film that may constantly feed into the pad.

FIG. 5 is a cross section of the pod 100 along line B-B in FIG. 4. Pod 100 comprises the reservoir 102 having post wick air flow passage 104, and end cap 106. Mouthpiece 118 is not shown in this figure for simplicity. Although there is an illustrated gap between end cap 106 and reservoir 102, it should be understood that in addition to a possible tapering of end cap 106, seals 110 would normally block this gap below cut line B-B. Wick feed lines 108 allow for fluid communication between the reservoir and the wick which is below the cut line. Post wick air flow passage 104 is illustrated with an exaggerated surface texturing. Those skilled in the art will appreciate that the sizing of the texturing is a function of the material of the post wick air flow passage 104 and the e-liquid so that the decreased wettability described above is provided.

FIG. 6 is a cross section of an alternate design of a pod for use in an ENDS or other such vaporizer. Pod 200 comprises reservoir 202 having a post-wick air flow passage 204, and an end cap assembly 206. End cap assembly 206 includes wick feed lines 208, electrical contacts 210, an air inlet forming a pre-wick air flow passage 212, an atomization chamber 214 housing wick 216 and heater 218 (which is connected to electrical contacts 210). To seal end cap assembly 206 with reservoir 202, so that e-liquid cannot cannot leak or seep out of reservoir 202, and to keep end cap assembly 206 mounted within reservoir 202, and in place of the previously described O-ring, is a resilient cover or top cap 222. Resilient top cap 222 may be formed of any number of different resilient materials including silicone.

In the currently illustrated embodiment, a vortex generator 220 is introduced into the air flow path, shown here as being formed in top silicone 222 between wick 216 and post-wick air flow passage 204. The geometry of end cap assembly 206 and resilient top cap 222 can be arranged to ensure that the distance between wick 216 and vortex generator 220 is sufficient to allow the air flow to resume its laminar flow before impacting upon vortex generator 220. Those skilled in the art will appreciate that the size, location and orientation of vortex generator 220 can vary.

When a largely laminar air flow enters pod 200, it passes through pre-wick air flow passage 212, atomization chamber 214 and then encounters vortex generator 220 before entry into post wick air flow passage 204. The laminar air flow will be disrupted and will form vortices within post wick air flow passage 204. Because different sized droplets of e-liquid are entrained in the air flow, they will be differentially affected by the generated vortices. Typically, larger droplets will turn along a larger radius of curvature than will smaller droplets within the same vortex. This will result in larger droplets being preferentially pushed into the nanotextured walls of post wick air flow passage 204.

Because of the hydrophobic nature of the nanotextured walls of post wick air flow passage 204, these droplets will roll or slide down the sidewall back towards wick 216. The only force acting on the droplets, other than gravity, would be the airflow itself. Although there is a possibility that the air flow could re-entrain a droplet that had been deposited on the nanotextured surface of post wick air flow passage 204, the re-entrained droplet would still be subject to the vortices caused by vortex generator 220. Re-entrainment of a droplet will likely result in re-deposition of the droplet within post wick air flow passage 204. Because the airflow is only present when the pod 200 is in active use, the droplets deposited on the nanotextured wall of post wick air flow passage 204 will typically have sufficient time to fall into wick 216 or into the atomization chamber 214.

FIG. 7 illustrates a cross section of pod 200 along cut line C-C shown in FIG. 6. Pod 200 comprises reservoir 202, which stores e-liquid, and whose open end is capped with end cap 206. Between reservoir 202 and end cap 206 is resilient top cap 222. Resilient top cap 222 is illustrated in FIGS. 6 and 7 as having ribs used to prevent egress of the e-liquid from a gap between reservoir 202 and end cap 206. Wick feed lines 208 allow the reservoir 202 to be in fluid communication with the wick (which resides below the cut line). Post wick air flow passage 204 is illustrated as having a nanotextured surface (and as with FIG. 5, it should be understood that the surface structure is not necessarily shown to scale). Also present is vortex generator 220 which is, in this embodiment, a feature defined in the resilient top cap 222.

Vortex generator 220 can be used to aid in the removal of droplets entrained in the airflow, physical characteristics of the vortex generator 220, such as the size, shape, location and orientation of the vortex generator 220, help define a threshold size for droplets. Above this threshold, droplets are removed from the air flow by being pushed into the wall of post wick air flow passage 204. The nanotextured surface of post wick air flow passage 204 will aid in having the droplets cleared from the post wick air flow passage 204, which reduces the probability of a re-entrained droplet. As these droplets are already associated with spitback due to their size, the surface texture of post wick air flow passage 204 works cooperatively with the vortex generator to provide an improved usage experience at least through the mitigation of spitback.

With respect to the design of pod 100 and pod 200, it may be necessary to take care with the design of the low end of the post wick air flow passage (the end closest to the wick). As droplets form in the post wick air flow passage and are drawn to the bottom, the droplets will encounter a point at which they will be suspended and can drop into the wick or the atomization chamber. At this location, a droplet may hang from a bend in an injection molded reservoir. Although the post wick air flow passage is hydrophobic, the other side of this bend may not be, and may provide a sufficiently wettable surface to allow the droplets to hang in suspension. A hanging droplet may be entrained by the air flow in use. This may be addressed through the use of spitback mitigation measures such as a vortex generator, as illustrated above, and as described in detail in co-pending U.S. patent application Ser. No. 17/146,884 entitled “Droplet Size Management through Vortex Generation” filed on Jan. 12, 2021. Another measure that can be taken is the application of the nanotexturing to the surfaces adjacent and adjoining the low end of the post wick air flow passage. This will reduce the ability of a droplet to remain hanging to the ends of the post wick air flow passage.

FIGS. 8A and 8B, illustrate a droplet 302 of e-liquid that has been deposited on the nanotextured surface 304 of a post wick air flow passage. Droplet 302 is acted upon by gravity represented by arrow g, which pulls it in a downward direction. The sum of the forces resisting gravity is represented by arrow R which is illustrated as being smaller than force g. This difference in forces is attributable to the slipperiness of surface 304, which results in a hydrophobicity. Gravity exceeding resistive forces will result in the movement of the droplet 302 down the surface 304, as shown by the different locations of droplet 302 with respect to surface 304 in FIGS. 8A and 8B. The actual force applied to droplet 302 will be a function of the particular orientation of the post wick air flow passage, which may not be oriented to be perfectly vertical. In such cases, only a component of the force acting upon droplet 302 will be applied to moving the droplet across surface 304. As shown in this figure, the structure of the surface 304 is shown to be a regular pattern, which is not necessary. Also, the size of the structures of surface 304 are not necessarily to scale, but are illustrated at this size for ease of understanding. Textured surface 304 has both high and low points, the high points being separated from each other by low points. Although shown here as a regular repeating pattern, it should be understood that high points need not be either evenly distributed or equally tall. Where the Wenzel model shown in FIG. 3B has high points in the surface spaced relatively far apart, the tighter spacing of the high points illustrated in FIGS. 8A and 8B, prevents the liquid in droplet 302 from wetting the entirety of the surface 304. The spacing between high points is sufficiently small so that the surface tension of droplet 302 prevents it from entering the gap associated with the low point. The air gap created in the low points of surface 304 reduces the amount of surface 304 with which the droplet 302 is in contact with. Thus the area over which droplet 302 interacts with surface 304 is reduced in comparison to either an untextured surface, or a surface textured to increase wettability. This reduced surface contact results in a reduced wettability, which manifests itself as an increase in the hydrophobic nature of the surface 304. Application of gravity and other such forces will not greatly distort the shape of droplet 302, but instead will aid in the movement of the droplet with respect to the surface 304. Those skilled in the art will appreciate that these interactions may be governed by Cassie-Baxter equations.

Those skilled in the art will appreciate that the drawings of FIGS. 8A and 8B show a two dimensional structure, while in implementation this would be a three dimensional structure. In some embodiments the nanotextured surface may comprise arrays of micropillars. In other embodiments nanotextures can be imprinted upon the surface. The nanotextured surface need not be a regular repeating pattern, and can have a degree of randomness to it. Over the length of the post wick air flow passage, the nanotexturing pattern can vary. In some embodiments the nanotexturing may not cover the entirety of the surface of the post wick air flow passage.

By using a post wick air flow passage, at least a portion of which has a surface texture that is sufficiently fine to decrease the wettability of the surface, droplets forming or being deposited on the post wick air flow passage are able to be removed through the action of gravity. Because of the decreased wettability of the surface of the post wick air flow passage, it will behave as a hydrophobic surface and will allow for the shedding of these droplets when they are acted upon by gravity. This will remove the droplets from the post wick air flow passage where they otherwise would have had a risk of being entrained in the airflow and being delivered to the user as spitback. The size of the texturing, or of the surface features of the texturing, is a function of the material from which such a surface is made, and the characteristics of the particular e-liquid. In embodiments where the surface texturing is created using a coating, or a plurality of coatings, the size of the texturing features required to achieve the desired level of hydrophobicity will be dependant upon the characteristics of the e-liquid as well as the materials from which the coating or coatings are formed. These parameters can be used to determine an appropriate size for the surface texturing so that the interaction between the droplets and post wick air flow passage surface results in the surface being hydrophobic with respect to the e-liquid droplets.

It should be understood that in pods using a wick that is vertically oriented, it may be possible to realise the above described effects through texturing only a portion of the post wick air flow passage.

In the instant description, and in the accompanying figures, reference to dimensions may be made. These dimensions are provided for the enablement of a single embodiment and should not be considered to be limiting or essential. The sizes and dimensions provided in the drawings are provided for exemplary purposes and should not be considered limiting of the scope of the invention, which is defined solely in the claims.

Claims

1. A pod for use in a vaporizing system, the pod comprising:

a heater for atomizing an atomizable liquid stored within a reservoir; and

a post wick air flow passage having a wall, at least a portion of the wall having a surface texture causing a decreased wettability of the portion of the wall with respect to the atomizable liquid in comparison to the wettability of the wall without the texture.

2. The pod of claim 1 wherein the atomizable liquid is an e-liquid comprising at least one of propylene glycol, vegetable glycerine, nicotine and a flavoring.

3. The pod of claim 1 wherein the vaporizing system is an electronic nicotine delivery system.

4. The pod of claim 1 wherein the heater is located within an atomization chamber in communication with the post wick air flow passage.

5. The pod of claim 4 further comprising a wick within the atomization chamber, in fluid communication with the reservoir and in contact with the heater, for drawing the atomizable liquid from the reservoir towards the heater.

6. The pod of claim 1 wherein the surface texture is a texturing of a material from which the wall is formed.

7. The pod of claim 6 wherein the surface texture is sufficiently fine to result in an interaction between the atomizable liquid and the portion of the wall to be governed by Cassie-Baxter equations.

8. The pod of claim 1 wherein the portion of the wall comprises a coating deposited upon a substrate of the wall.

9. The pod of claim 8 wherein the coating has a texture sufficiently fine to result in an interaction between the atomizable liquid and the coating to be governed by Cassie-Baxter equations.

10. The pod of claim 8 wherein a surface texturing has been applied to the coating.

11. The pod of claim 10 wherein the coating is comprised of one of glass and a polymer.

12. The pod of claim 8 wherein the surface texture is defined by the coating and the substrate.

13. The pod of claim 8 wherein the coating is one of a plurality of coatings, and the surface texture is defined by the plurality of coatings.

14. The pod of claim 1 wherein the surface texture creates a surface that is hydrophobic to the atomizable liquid.

15. The pod of claim 1 wherein the post wick air flow passage and the reservoir are integrally formed.