WO2022180578A1 - Capillary valved vaporizer pod - Google Patents

Abstract

Pressure regulation in a reservoir or pod for use in an electronic nicotine delivery system is provided through the use of a capillary valve having internal and external overflow reservoirs connected by a capillary channel. The channel is filled with a liquid held in place through surface tension. Sufficient excess pressure allows for a portion of the liquid to be vented into the overflow reservoir, allowing gas to escape and for the pressure to be regulated. Protective hydrophobic membranes can be used to cover the overflow reservoirs, and sizing of the reservoirs can be controlled to allow for the valve to be set up as a one way valve.

Description

Capillary Valved Vaporizer Pod

Cross Reference to Related Applications

[0001] This application claims the benefit of priority to US Patent Application Number 17/185,452 filed February 25, 2021 and entitled “Capillary Valved Vaporizer Pod” the contents of which are incorporated herein by reference.

Technical Field

[0002] This application relates generally to a capillary valve, and more particularly to a capillary valve for use in conjunction with an electronic cigarette or vaporizer.

Background

[0003] In the field of electronic cigarettes and vaporizers, disposable pods are sold to consumers in a filled state. In some situations, the pod is not completely filled, resulting in an air bubble in the pod. Additionally, whether the pod is filled completely or not, as the e-liquid within the pod is consumed, an air bubble develops within the rigid walled pod.

[0004] Figure 1 illustrates an example of one such pod 50. Pod 50 is formed from a reservoir 52, which typically has rigid walls and defines a post-wick air flow passage 54 in its interior, and an end cap 56. Post-wick air flow passage 54 terminates at one end of the reservoir 52 (illustrated in Figure 1 as the top of the pod 50) and opens to the interior of the reservoir 52 at the opposing end. It will be understood that reservoir 52 has an internal surface and an external surface. The internal surface of reservoir 52 being adjacent to the interior of reservoir 52, and the external surface of reservoir 52 being adjacent to the exterior of reservoir 52. The end of reservoir 52 opposite the post-wick air flow passage terminating end, is designed to be open so that the pod can be filled. The open end of reservoir 52 is sealed, after filling, through the insertion of end cap 56. End cap 56 engages with the post-wick air flow passage 54 to prevent undesired flow of the e-liquid into internal structures of the end cap 56. End cap 56 will typically have an aerosolization chamber and connections to a vaporization device which will supply power to a heater within the aerosolization chamber. In many embodiments a wick is used to draw e-liquid into the aerosolization chamber through feed ports 58 in the end cap.

[0005] Either at the time of filling, or during use, reservoir 52 includes an air bubble 60 and e-liquid 62. This can lead to a problem, as air bubble 60 and e-liquid 62 will respond to both temperature and pressure changes differently. It should be understood that pod 50 is not a closed system. There is a path that leads from the interior of reservoir 52, through the end cap 56 into the atomization chamber and out through the post-wick air flow passage 54. There may also be an airflow aperture within end cap 56 (typically at the base of end cap 56 in line with post-wick air flow passage 54) to allow for air flow to pass through the atomization chamber during operation of the vaporizer. An increase in the temperature of the pod can cause the air bubble to expand, resulting in e-liquid being pushed into the atomization chamber. Similarly, a reduction in the air pressure outside the pod, such as may occur if a pod is put in the cargo hold of a plane, will result in the air bubble 60 pushing e-liquid 62 into the atomization chamber so as to equalize the pressure between the interior and exterior of the pod 50.

[0006] When e-liquid 62 is pushed into the atomization chamber it can either leak from the bottom of the pod or it can be forced into post-wick air flow passage 54. Because end cap 56 is friction fit into reservoir 52, it is also possible for the expansion of air bubble 60 to push e-liquid 62 out past any seals that may surround the end cap 56.

[0007] In general having a mechanism that would allow for pressure equalization between the inside and outside of the reservoir would allow for mitigation of any leaking or oozing of e-liquid during shipping or storage. Such a pressure equalization mechanism would aid in mitigating the unintended loss of e-liquid.

[0008] It would therefore be beneficial to have a mechanism to allow for equalizing the pressure between the interior and exterior of an e-liquid pod.

Summary

[0009] It is an object of the aspects of the present invention to obviate or mitigate the problems of the above-discussed prior art.

[0010] In a first aspect, there is provided a pod, for storing an e-liquid and for use with an electronic vaporizer. The pod has a capillary valve within the wall of a reservoir. The valve comprises a first overflow reservoir, a second overflow reservoir and capillary channel connecting the first and second overflow reservoirs. The first overflow reservoir has a volume and is defined on an external surface of the reservoir wall. The second overflow reservoir has a volume and is defined on an internal surface of the reservoir wall. The capillary channel connects the first overflow reservoir and the second overflow reservoir and stores a volume of liquid that is held in the capillary channel by surface tension. The width of the capillary channel can be determined in accordance with the surface tension and a defined cracking pressure of the valve.

[0011] In an embodiment of the first aspect, the valve comprises a hydrophobic membrane that is impermeable to liquid but is permeable to a gas. In some embodiments this membrane seals the first overflow reservoir, while in others it seals the second overflow reservoir. In some embodiments both the first and second overflow reservoirs are covered by a permeable membrane. In further embodiments, the volume of the first overflow reservoir is greater than the volume of liquid held in the capillary channel. In further embodiments, the volume volume of the second overflow reservoir is less than the volume of liquid held in the capillary channel, when the second overflow reservoir is sized in this fashion and is covered by the hydrophobic membrane, the capillary valve is unidirectional and cannot vent gas into the reservoir.

[0012] In another embodiment, there are a plurality of capillary channels. Each of the plurality of capillary channels connects the first overflow reservoir and the second overflow reservoir. Each of the plurality of capillary channels stores a volume of liquid held in the capillary channel by surface tension. As before, the width of each capillary channel is determined in accordance with the surface tension and a defined cracking pressure of the valve. In some embodiments, each of the capillary channels has the same dimensions, while in others, at least one capillary channel in the plurality is differently sized than another capillary channel in the plurality. Each of the capillary channels can hold the same volume of liquid in some embodiments, while in other different channels can hold different volumes of liquid. The liquid held in each channel can differ for at least one of the channels in some embodiments.

[0013] In some embodiments the first and second overflow reservoirs can differ in size, so that in one embodiment the volume of the first overflow reservoir exceeds the volume of the second overflow reservoir. In some embodiments, the defined volume of the first overflow reservoir is less than the volume of the liquid held in the capillary channel. In some embodiments, the defined volume of the second overflow reservoir is less than the volume of the liquid held in the capillary channel.

[0014] In other embodiments at least one of the first overflow reservoir and the second overflow reservoir has a base and a sidewall defined within the reservoir wall. In some embodiments the base and sidewall meet at a 90° angle. In other embodiments the base and the capillary channel meet at a 90° angle.

[0015] Such a capillary valve provides a mechanism for pressure regulation, and in some cases equalization, between an internal space within a pod or other such container and the external environment. By allowing a degree of pressure equalization through the venting of excess pressure through the capillary tube, the contents of a pod can be protected and leaking can be mitigated. The valve can be designed as a unidirectional valve through sizing of the corresponding overflow reservoir. By sealing one of the overflow reservoirs and designing the volume of the reservoir to be less than the volume of the liquid within the capillary tube, the valve cannot open under non-failure conditions. The shaping of the overflow reservoirs and the capillary tube can be varied to accommodate different manufacturing or machining techniques.

[0016] In a different aspect, the valve is provided through a stacking of fabrics and membranes. At least one of the fabrics in the stack can be wetted, and different porosity characteristics for each layer can be specified. This can result in a wetted fabric having narrow pores being able to have the wetting agent pushed into larger pores in an adjacent layer. In this fashion, the narrow pored fabric functions like the capillary tube, and the pores of the larger fabric act as overflow reservoirs. By selecting different numbers and arrangements of layers, both unidirectional and bidirectional valves can be designed. This capillary valve fabric can be encapsulated within a hydrophobic membrane and then applied to the surface of a packaging. In one such example, a capillary valve fabric patch can be applied to the surface of a pod containing an e-liquid to cover a vent hole in the reservoir wall.

Brief Description of the Drawings

[0017] Figure 1 illustrates a cross section of a prior art e-liquid pod;

[0018] Figure 2 illustrates a cross section of a capillary valve;

[0019] Figure 3 illustrates a cross section of an embodiment of a capillary valve with a hydrophobic layer;

[0020] Figure 4 illustrates a cross section of the capillary valve of Figure 3 under activation pressure; [0021] Figure 5 illustrates a cross section of a capillary valve according to an embodiment of the present invention;

[0022] Figure 6 illustrates a cross section of the capillary valve of Figure 5 under external pressure;

[0023] Figure 7 illustrates a cross section of a capillary valve according to an embodiment of the present invention;

[0024] Figure 8A illustrates a top view of a capillary valve according to an embodiment of the present invention;

[0025] Figure 8B illustrates a cross section of the capillary valve of Figure 8 A along section line A;

[0026] Figure 9 illustrates a cross section of a one way valve of the present invention; and [0027] Figure 10 illustrates a cross section of a bi-directional valve of the present invention.

Detailed Description

[0028] 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 a 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.

[0029] Although presented below in the context of use in 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.

[0030] As noted above, the mechanism to equalize pressures between the inside and outside of a pod can allow for pressure equalization without forcing e-liquid out of the reservoir. Conventionally, the reservoir and end cap are both made from molded plastics, or other rigid materials. This allows for a low cost and structurally solid pod. The use of active components is made difficult by the design of most pods in the field. Furthemore, adding in moving elements to create an active component, such as a valve, would greatly increase the cost of manufacturing, and would introduce components whose failure could result in the very leakage of e-liquid that the component was introduced to prevent. [0031] Capillary valves are known structures that act as passive valves without discrete moving parts. A liquid is kept within a channel between solid walls as a result of surface tension. The maximum distance between the walls (which may be manifested as the maximum diameter of a capillary channel) is a function of the strength of the surface tension that the liquid has with the material from which the walls are constructed. The strength of the surface tension also establishes a cracking pressure for the valve. As a pressure imbalance grows on one side of the valve, the pressure is applied to the liquid seal. At the cracking pressure, the sealing liquid is pushed out of the valve, and the pressure is equalized.

[0032] Figure 2A is a top view of a capillary valve 100, while Figure 2B is a cross section of the capillary valve of Figure 2A taken along section line A. Capillary valve 100 can be integrated into the wall of reservoir 52. Valve 100 can be formed in the walls of reservoir 52, which is shown as sidewalls 102 and 104 (which as shown in Figure 2Ais a single surface). At the external side, an overflow reservoir 106 is formed, and at the internal side an overflow reservoir 108 is formed. As illustrated, a base of the overflow reservoir 106 meets a sidewall at a 90° angle, while the base and capillary channel also meet at a 90° angle. Those skilled in the art will appreciate the sidewall can meet the base at other angles. As illustrated, the sidewall is a circular wall within the reservoir wall. These overflow reservoirs 106, 108 can be formed as voids in the surface of the reservoir, connected by a capillary channel 110. The channel is filled with liquid 112. The dimensions of the capillary channel 110 will define the breaking pressure of the valve. The surface tension between the liquid 112 and the material of the sidewalls 102 and 104 define both the maximum diameter of the capillary channel 112, and the mass of the liquid 112 that can be held in the channel 112. The mass of liquid 112, given a constant density, will define the volume of liquid 112 within the capillary channel 110. The weight of the liquid 112 can be reduced by shortening the length of the channel 110 or by decreasing the width of the channel 110.

[0033] With liquid 112 in the column, valve 100 is effectively closed, any fluid seeking to move through the valve would either have to exert sufficient pressure to crack the valve, or would be kept out. The overflow reservoirs 106 and 108 can be sized to allow some or all of the liquid 112 to be stored when the valve cracks. When the pressure equalizes, and surface tension pulls the liquid 112 back into column 110 the valve can then re-seal. Those skilled in the art will appreciate that overflow reservoirs 106 and 108 are illustrated in this figure as being both rectangular and of effectively the same size. This is done for illustrative purposes and should not be considered limiting.

[0034] Figure 3 illustrates an embodiment of valve 100 as shown in Figures 2A and 2B, in section. In the embodiment of Figure 3, a hydrophobic membrane 116i is shown on the internal side of the valve 100. Hydrophobic membrane 116i prevents liquid 112 from escaping towards the interior of the pod. Hydrophobic membrane 116i does not prevent air or other gasses from passing through. This layer can be used to prevent liquid inside the reservoir from interacting with, and possibly contaminating the liquid 112 in column 110. [0035] Figure 4 illustrates the embodiment of valve 100 of Figure 3, when pressure on the interior side exceeds the pressure on the exterior side by a sufficient amount. When sufficient pressure builds, gas is able to pass through hydrophobic membrane 116i, and push liquid 112 through the column 110. With the reduction of the volume of liquid 112 in the column (as liquid exiting the column will enter reservoir 106) the pressure will allow the liquid 112 to separate to form an annular shape. The void in the middle of liquid 112 creates a clear path in channel 110 to allow venting of the excess pressure. Those skilled in the art will appreciate that in some embodiments, the entire channel 110 may not be clear at a single time, and the air passage may release a bubble that is not the full length of the channel. In such situations, liquid 112 may not fully separate into the annular shape, but it will still allow discharge of gas to equalize the pressure as bubbles.

[0036] In Figure 5, an alternate embodiment of the valve is illustrated. Valve 122 differs from the previous embodiment of valve 100. While the embodiment of of Figures 3 and 4 made use of a single hydrophobic membrane 116i on the internal surface of the valve, valve 122 makes use of both hydrophobic membrane 116i on the internal surface of the valve 122, but also a hydrophobic membrane 116e on the external surface of valve 122. This use of two hydrophobic membranes 166i and 116e both seals the liquid 112 into valve 122, and also protects it from contamination. In operation, an excess pressure on the internal side will displace liquid 112 towards reservoir 106, and the valve will crack as previously illustrated. [0037] Furthermore, where previously reservoirs 106 and 108 were somewhat equivalently sized, the reservoir 124 on the internal side of the valve 122 is smaller in size. Reservoir 124 is sized to be smaller in volume than the volume of liquid 112. Operation of this valve 122 in the face of a sufficiently high external pressure will be discussed with respect to Figure 6. [0038] Figure 6 makes use of a reservoir 124a, which is similarly sized as reservoir 124, but is illustrated to show that the reservoirs do not need to be constructed with only right angles. The base of reservoir 124a meets with the capillary channel 110 at an obtuse angle, and it meets with the sidewall at another obtuse angle. When the pressure outside the valve 122 sufficiently exceeds the pressure inside, air will be forced past hydrophobic membrane 116e and into column 110. Because the volume of liquid 112 exceeds that of reservoir 124a the excess pressure will force liquid 112 into reservoir 124a with some remaining in column 110. The hydrophobic membrane 116i prevents the expulsion of liquid 112 from the valve 122, and prevents the valve 122 from opening. It will be understood by those skilled in the art that different hydrophobic membranes can be used, and different hydrophobic membranes will have different properties, including pressures at which seepage or other forms of failure will occur. With this arrangement of a reservoir smaller in volume than the volume of liquid 112, and a hydrophobic membrane 116i that prevents complete expulsion of liquid 112 from column 110, it is not possible to vent air from outside the reservoir into the reservoir. As such, in the embodiments of Figures 5 and 6, valve 122 is a one way valve that allows excess pressure to be vented from the reservoir, but not into the reservoir. Those skilled in the art will appreciate that while shown being a one way valve that allows air to vent from the reservoir, a reversal of the reservoirs 106 and 124a would result in a valve that allows venting into the reservoir while preventing venting from the reservoir.

[0039] Figure 7 illustrates another alternate embodiment of the capillary valve 126. Valve 126 has sidewalls 102 and 104 that may be a part of an e-liquid pod. Reservoirs 128 and 130 are formed in the void between sidewalls 102 and 104. Capillary column 110 is less defined than in previous embodiments, but by having the sidewalls taper towards each other, a capillary channel 110 is still created that is able to hold liquid 112.

[0040] The modifications illustrated in earlier embodiments can further be applied to this embodiment by altering the sizes of the reservoirs 128 and 130, allowing for the creation of a one way valve. Furthermore, the use of a single hydrophobic layer instead of both hydrophobic layers 116e and 116i allow for protection of the liquid 112 from contamination. [0041] Figures 8 A and 8B illustrate another embodiment of a capillary valve. Capillary valve 132 is formed within a surface 134 of an object such as the reservoir of a pod for an electronic nicotine delivery system (ENDS), such as an e-cigarette or vaporizer. As with previous embodiments, overflow reservoirs 136 and 138 are formed at the external and internal surfaces of the valve 132 respectively. Connecting reservoirs 136 and 138 are a plurality of capillary channels 140 each filled with a liquid 142. Those skilled in the art will appreciate in some embodiment hydrophobic membranes may be applied to seal across one or both of reservoirs 136 and 138. The operation of valve 132 is similar to the above described embodiments, When sufficient pressure builds up on one side of the valve, liquid 142 will be pushed out of its capillary column 140, and will allow for a channel to form in liquid 142. This channel allows for the venting of gas and equalization of pressure. It should be understood that in different embodiments, reservoirs 136 and 138 can be differently shaped and sized, the number of capillary channels 140 can vary and there is no requirement for each of the channels 140 to be the same size. In some embodiments at least one of the capillary channels 140 can make use of a different liquid 142 than another capillary channel. [0042] The concept of a capillary valve using a reservoir at the end of a capillary channel, and hydrophobic layers protecting the other components of the valve can have many different embodiments and applications.

[0043] Figure 9 illustrates one such embodiment of a one way valve 150. Hydrophobic layers 152 and 154 prevent liquid from passing through the layers in either direction. Two fabric layers 156 and 160 are used. Layer 160 is wetted so that its pores 162 are at least partially filled. It should be understood that the fabric layers may, in some embodiments, be synthetic fabrics or synthetic layers. The pores 162 in fabric layer 160 are smaller than the pores 158 in fabric layer 156. The pores 162 operate as the equivalent to the capillary channel of the previously illustrated embodiment. By wetting the fabric 160, pores 162 will be at least partially filled. Fabric layer 156 would be unwetted, allowing its larger pores 158 to act as the analog to the external side reservoir in the previous embodiments. The hydrophobic layers 152 and 154 prevent loss of the wetting liquid, and prevent additional liquid from entering the valve 150. In the illustrated embodiment, an excess of pressure from the side shown as the bottom would allow a gas to enter valve 150 through hydrophobic layer 154, and put pressure on the liquid within the pores 162 of wetted layer 160. This will push liquid within pores 162 into pores 158 of unwetted layer 156. Because pores 158 are larger than pores 162, they can act like the overflow reservoirs of the previous embodiments. This allows for either a separation of the liquid within pores 162, or for the liquid to completely transfer to pores 158, where the liquid can separate and allow the gas to pass through and exit valve 150 through hydrophobic layer 152. When the pressure is equalized on either side of valve 150, the liquid will return to pores 162 completing the seal. This may only require a partial re-wetting of the fabric 160 to create a sufficient seal to close the valve.

[0044] When pressure at the top of the illustrated valve 150 exceeds the pressure below, the gas may enter through hydrophobic layer 152. Any liquid in pores 158 will be driven into the pores 162 of layer 160. Because of the narrower profile of pores 162, liquid driven downwards in pores 162 will not separate and allow the valve to break. Instead, the liquid will encounter hydrophobic layer 154 before it would separate to allow gas to pass through. This effectively creates the same effect shown in Figure 6. Accordingly, valve 150 only allows pressure equalization to occur in a single direction, thus creating a one-way valve. [0045] So long as layer 160 is more hydrophilic than layer 156, in the absence of external pressures, the liquid will be preferentially drawn into the lower layer 160. This is not a requirement for operation, as the pressures on either side of the valve 150 will push the liquid seal to the layers as required. The preferential hydrophilicity of the layers can aid in the operation of the valve regardless of orientation.

[0046] Although shown here as a cross section of a segment, it should be understood that valve 150 can be made as a sandwich of different layers of fabrics and the hydrophobic layers (which may be embodied as a membrane that can be fused to the resective fabric layers). This would allow production of a sheet of the sandwiched fabrics and membranes, from which valves of different sizes and shapes can be cut.

[0047] There may be a need for a bidirectional valve made from the fabric and membranes discussed above. Figure 10 illustrates an embodiment of such a valve 165. Bidirectional valve 165 is comprised of hydrophobic layers 152 and 154 as before. These hydrophobic layers 152 and 154 can be implemented as membranes that can be laminated to the underlying fabric layers in some embodiments.

[0048] Where the unidirectional valve 150 of Figure 8 was made of two layers, the bidirectional valve 165 is shown as made with three internal layers. Layer 160 with narrow pore 162 is sandwiched between two layers 156 having larger pores 158. Again, layer 160 is wetted. In some embodiments layer 160 is more hydrophilic than layers 156 which allows pores 162 to draw the liquid back into the middle layer when pressure has been equalized. When pressure on either side of the valve 165 exceeds the pressure on the other side by a margin in excess of the cracking pressure of the valve 165, the gas pushes through hydrophobic layer 152 or 154 as appropriate. The gas passes through the pores 158 of layer 156, and enters the wetted layer 160. The gas pushes the liquid in layer 160 out of pores 162 and into pores 158 of the second layer 156. Because pores 158 are wider than pores 162, it allows a cracking of the valve 165 much as is shown for valve 100 in Figure 4, with pores 158 of the second layer 156 acting as the reservoir 106. The symmetric structure of valve 165 means that the valve 165 can operate as a bi-directional valve, as pressure on either side of the valve can be vented.

[0049] In the above discussions, both unidirectional and bidirectional valves are disclosed.

As applied to an ENDS or other vaporizer pod, these valves provide a pressure regulation mechanism that can operate without use of a number of moving parts. The pressure regulation can be used to prevent an excess of pressure which results in the expansion of an air bubble in the pod pushing e-liquid out of the pod, either through flooding a wick, or by encouraging the seepage or leaking of the e-liquid from the reservoir through any interface between the reservoir and the end cap assembly. This can be achieved through the use of either a unidirectional valve allowing gas to leave the reservoir or a suitably designed bi-directional valve.

[0050] As the liquid drains from the pod, a reduced pressure may result. This reduced pressure, also considered to be a weak vacuum, helps slow the rate at which the liquid migrates into the wick, and prevents flooding of the wick and the air flow paths. In some embodiments of the present invention, in order to preserve this low pressure in the reservoir, any capillary valve allowing air to enter the pod should be designed to limit the ingress of air to preserve this effect. A unidirectional capillary valve allowing egress of air from the pod, or a bidirectional capillary valve tuned to have a very high breaking pressure for ingress of air into the pod, would allow for both the mitigation of the effects of an expanding air bubble, and for helping maintain the suitable partial vacuum as e-liquid is consumed.

[0051] As noted above, the sizes 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 an electronic vaporizer and for storing e-liquid, the pod comprising a reservoir formed from a reservoir wall having a capillary valve, the valve comprising: a first overflow reservoir defined on an external surface of the reservoir and having a defined volume; a second overflow reservoir defined on an internal surface of the reservoir and having a defined volume; a capillary channel connecting the first overflow reservoir and the second overflow reservoir, storing a volume of liquid held in the capillary channel by surface tension, the width of the capillary channel determined in accordance with the surface tension and a defined cracking pressure of the valve.

2. The pod of claim 1 wherein the valve further comprises a hydrophobic membrane sealing the first overflow reservoir, the hydrophobic membrane being impermeable to liquid but permeable to a gas.

3. The pod of claim 2 wherein the defined volume of the first overflow reservoir is greater than the volume of liquid held in the capillary channel.

4. The pod of any one of claims 1 to 3 wherein the valve further comprises a hydrophobic membrane sealing the second overflow reservoir, the hydrophobic membrane being impermeable to liquid but permeable to a gas.

5. The pod of claim 4 wherein the defined volume of the second overflow reservoir is less than the volume of liquid held in the capillary channel.

6. The pod of any one of claims 1 to 5 wherein the capillary channel is one of a plurality of capillary channels, each capillary channel in the plurality connecting the first overflow reservoir and the second overflow reservoir, storing a volume of liquid held in the respective capillary channel by surface tension, the width of each capillary channel determined in accordance with the surface tension and a defined cracking pressure of the valve.

7. The pod of claim 6 wherein at least one capillary channel in the plurality is differently sized than another capillary channel in the plurality.

8. The pod of any one of claims 6 and 7 wherein at least one capillary channel stores a liquid different from the liquid stored in at least one other capillary channel in the plurality.

9. The pod of any one of claims 1 to 8 wherein the defined volume of the first overflow reservoir is different from the defined volume of the second overflow reservoir.

10. The pod of claim 9 wherein the defined volume of the first overflow reservoir is larger than the defined volume of the second overflow reservoir.

11. The pod of any one of claims 2 to 10 wherein the defined volume of the first overflow reservoir is less than the volume of the liquid held in the capillary channel.

12. The pod of any one of claims 4 and 5 wherein the defined volume of the second overflow reservoir is less than the volume of the liquid held in the capillary channel.

13. The pod of any one of claims 1 to 12 wherein at least one of the first overflow reservoir and the second overflow reservoir has a base and a sidewall defined within the reservoir wall.

14. The pod of claim 13 wherein the base and sidewall meet at a 90° angle.

15. The pod of any one of claims 13 and 14 wherein the base and the capillary channel meet at a 90° angle.