Liquid Storage Cavity

Abstract

Embodiments described herein relate to a liquid storage cavity comprising a base, one or more walls extending from the base, the liquid storage cavity having a volume defined by the base and the one or more walls, and a periphery where the one or more walls are joined to the base, at least a portion of the periphery including a peripheral recess defined by the base and at least one of the one or more walls, the peripheral recess configured to accommodate a volume of liquid.

Description

[Technical field]

[0001] The present disclosure relates to a liquid storage cavity, such as a liquid storage capsule or chamber. [Background technology]

[0002] Point-of-care diagnostic devices can include cavities such as chambers and / or capsules for storing liquids used in diagnostic tests. For example, capsules can be used to store reagents used in a particular diagnostic test. As another example, mixing chambers can be implemented to allow mixing of solutions (e.g., dilution of a sample). Such chambers and / or capsules usually include an outlet, allowing the transfer of the liquid to another component of the device. For example, the solution may be transferred to a flow cell, where an electrochemical measurement is performed.

[0003] It is inevitable that the chambers and / or capsules used in diagnostic devices will contain air. Thus, there is a risk that the liquid flowing through the outlet of the chamber / capsule will contain one or more air bubbles. Air bubbles are undesirable in point-of-care diagnostic devices, as they may interfere with measurements made on the solution in the flow cell. For example, if an air bubble is located over one of the electrodes in the flow cell, the electrochemical measurement may provide an erroneous reading.

[0004] Therefore, a need exists for an improved liquid storage cavity that reduces or prevents air bubbles in the liquid exiting the cavity.

[0005] By preventing or reducing air bubbles in the liquid stream, a greater percentage of the liquid in the cavity can be removed before air bubbles form. This means that for a given amount of liquid required, a smaller liquid storage cavity (chamber, capsule, etc.) can be implemented. This is beneficial since the footprint of point-of-care diagnostic devices is often limited. Summary of the Invention

[0006] This Summary introduces concepts that are described in more detail in the Detailed Description, and is not intended to identify essential features of the claimed subject matter, nor should it be used to limit the scope of the claimed subject matter.

[0007] According to one aspect of the disclosure, there is provided a liquid storage cavity comprising a base, one or more walls extending from the base, the liquid storage cavity having a volume defined by the base and the one or more walls, and a periphery where the one or more walls are joined to the base, at least a portion of the periphery including a peripheral recess defined by the base and at least one of the one or more walls, the peripheral recess configured to accommodate a volume of liquid.

[0008] The volume of liquid contained within the elongated peripheral recess provides a continuous fluid path around the periphery of the cavity (or part of it). This means that liquid can be drawn from the elongated peripheral recess to the cavity outlet if a liquid bridge can be provided between the outlet and the elongated peripheral recess. This allows for a continuous flow of liquid out of the cavity outlet without air bubbles being entrained in the liquid flow.

[0009] At least one of the one or more walls may extend outwardly from an interior of the liquid storage cavity to define a peripheral recess. At least one of the one or more walls may comprise a first wall portion and a second wall portion, the first wall portion extending between the base and the second wall portion around a portion of the periphery, and the second wall portion extending from the first wall portion in a direction away from the base.

[0010] The first wall may define a fillet between the second wall and the base. The radius of the fillet defined by the first wall may be between 0.15 mm and 1 mm. A fillet radius in this range is useful for certain liquids by maintaining a continuous supply of liquid in the peripheral recess (without breakage of the liquid in the peripheral recess) without retaining too much liquid in the peripheral recess after the liquid storage cavity is emptied. Preferably, the radius of the fillet defined by the first wall may be between 0.2 mm and 0.6 mm.

[0011] The first wall may extend at an acute angle between the base and the second wall such that the peripheral recess has a triangular cross section. The acute angle between the first wall and the base may be 45 degrees or less. The first wall may extend laterally beyond the junction between the first wall and the second wall a distance of 0.5 mm or less. These boundaries on the angle and distance of the first wall are useful for certain liquids by maintaining a continuous supply of liquid in the peripheral recess (without breakage of the liquid in the peripheral recess) without retaining too much liquid in the peripheral recess after the liquid storage cavity is emptied.

[0012] The first wall may comprise a first portion and a second portion, the first portion of the first wall being joined to the second wall and extending from the interior to the exterior of the liquid storage cavity in a direction substantially parallel to the base, and the second portion of the first wall extending between the first portion and the base such that the elongated recess has a quadrilateral cross section. The first portion of the first wall may have a width of 0.5 mm or less. The second portion of the second wall may have a height of 0.5 mm or less. These boundaries for the angle and distance of the first wall are useful for certain liquids by maintaining a continuous supply of liquid in the peripheral recess (without breakage of the liquid in the peripheral recess) without retaining too much liquid in the peripheral recess after the liquid storage cavity is emptied.

[0013] The liquid storage cavity may be a capsule. The height of the liquid storage cavity may be 5 mm or less. This range of cavity heights provides a liquid column between the upper and lower inner surfaces of the cavity, which increases the volume of bubble-free liquid that can be dispensed from the cavity when the cavity is inverted (i.e., with its outlet at the top surface of the cavity). Preferably, the height of the liquid storage cavity may be 3.5 mm or less.

[0014] The angle between the second wall and the base may be less than 55 degrees. This reduces pooling of liquid and the formation of droplets in the cavity when the cavity is emptied in an upside-down orientation. The second wall may define a top surface of the cavity that is non-parallel to the base. This further reduces the tendency for pooling of liquid or the formation of droplets during upside-down emptying. The width of the cavity may be no greater than 2.5 times the height of the cavity.

[0015] The second wall may extend away from the base in a direction substantially perpendicular to the base, which maximizes the volume of the cavity for a given footprint of the cavity.

[0016] The peripheral recess may extend around the entire periphery of the liquid storage cavity, allowing liquid to be drawn into the peripheral recess around any part of the periphery of the cavity.

[0017] The liquid storage cavity may further comprise an outlet at the base. The outlet may be coincident with a part of the periphery. Providing an outlet that is coincident with the periphery means that no liquid bridge is required between the outlet and the periphery to remove liquid from the chamber.

[0018] According to another aspect of the present disclosure, there is provided a method of removing liquid from a liquid storage cavity comprising providing a liquid storage cavity of the first aspect, providing an inlet to the liquid storage cavity and an outlet from the liquid storage cavity, orienting the liquid storage cavity such that the outlet is located above the liquid storage cavity, and supplying gas through the inlet to expel liquid from the outlet.

[0019] The peripheral recess in the liquid storage cavity allows the liquid storage cavity to be emptied even when the cavity is in an upside down position (ie when the outlet is located on the upper side of the liquid storage cavity).

[0020] Providing an outlet at a base of the liquid storage cavity may comprise providing the liquid storage cavity with an outlet in the base. Alternatively, providing an outlet at a base of the liquid storage cavity may comprise creating an outlet at the base of the liquid storage cavity. [Brief description of the drawings]

[0021] Specific embodiments are now described, by way of example only, and with reference to the accompanying drawings. [Figure 1A] 1 is a schematic cross-sectional view through a liquid storage cavity having a peripheral recess, the liquid storage cavity being in the process of being emptied; [Figure 1B] FIG. 1B is a schematic cross-sectional view through the liquid storage cavity of FIG. 1A after it has been emptied. [Figure 2A] FIG. 2 is an isometric view of a liquid storage capsule. [Figure 2B] FIG. 2B is a top view of the liquid storage capsule shown in FIG. 2A. [Figure 2C] FIG. 2B is a side view of the liquid storage capsule shown in FIG. 2A. [Figure 2D] 2B is a simulation showing the liquid in the liquid storage capsule shown in FIG. 2A. [Figure 3A] 1 is a simulation showing an isometric view of liquid remaining in a liquid storage capsule after a first period of time. [Figure 3B] FIG. 3B is a top view of the simulation shown in FIG. 3A. [Figure 4A] 3B is a simulation showing an isometric view of the liquid remaining in the simulated liquid storage capsule of FIG. 3A after a second period of time. [Figure 4B] FIG. 4B is a top view of the simulation shown in FIG. 4A. [Figure 4C] FIG. 4C is a cross-sectional view taken along line AA in FIG. 4B. [Figure 4D] FIG. 4C is a cross-sectional view taken along line BB in FIG. 4B. [Figure 5A] 3B is a simulation showing an isometric view of the liquid remaining in the simulated liquid storage capsule of FIG. 3A after a third time period. [Figure 5B] FIG. 4C is a cross-sectional view through line AA of FIG. 4B after a third period of time. [Figure 5C] FIG. 4C is a cross-sectional view through line BB of FIG. 4B after a third period of time. [Figure 6A] 1 is a simulation showing an isometric view of the liquid volume in the chamber after a first period of time. [Figure 6B] FIG. 6B is a top view of the simulation shown in FIG. 6A. [Figure 6C] FIG. 6C is a cross-sectional view taken along line AA in FIG. 6B. [Figure 7A] 6B is a simulation showing an isometric view of the liquid volume in the simulated chamber of FIG. 6A after a second period of time. [Figure 7B] FIG. 6C is a cross-sectional view through line AA of FIG. 6B after a second period of time. [Figure 8A] 1 shows a simulation result of a cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a fillet. [Figure 8B] 1 shows a simulation result of a cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a fillet. [Figure 8C] 1 shows a simulation result of a cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a fillet. [Figure 9] FIG. 1 is a cross-sectional view through a liquid storage cavity having a peripheral recess defined by a chamfer. [Figure 10A] 1 shows a simulation of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a chamfer. [Figure 10B] 1 shows a simulation result of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a chamfer. [Figure 10C] 1 shows a simulation result of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a chamfer. [Figure 10D] 1 shows a simulation of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a chamfer. [Figure 10E] 1 shows a simulation of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a chamfer. [Figure 11] FIG. 2 is a cross-sectional view through a liquid storage cavity having a peripheral recess defined by a step. [Figure 12A] 1 shows a simulation of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a step. [Figure 12B] 1 shows a simulation of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a step. [Figure 12C] 1 shows a simulation of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a step. [Figure 12D] 1 shows a simulation of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a step. [Figure 12E] 1 shows a simulation of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a step. [Figure 12F]1 shows a simulation of the cross-sectional area of ​​liquid within a peripheral recess of a liquid storage cavity, the peripheral recess being defined by a step. [Figure 13A] FIG. 1 is a cross-sectional view through a liquid storage cavity having an outlet at the top of the liquid storage cavity. [Figure 13B] FIG. 13 is a cross-sectional view through a further liquid storage cavity having an outlet at the top of the liquid storage cavity. [Figure 14A] 13 shows the results of a simulation of the cross-sectional area of ​​liquid in a peripheral recess of a liquid storage cavity with an outlet at the top of the liquid storage cavity. [Figure 14B] 13 shows the results of a simulation of the cross-sectional area of ​​liquid in a peripheral recess of a liquid storage cavity with an outlet at the top of the liquid storage cavity. [Figure 14C] 13 shows the results of a simulation of the cross-sectional area of ​​liquid in a peripheral recess of a liquid storage cavity with an outlet at the top of the liquid storage cavity. [Figure 15A] FIG. 13 is a side view of a tool used to deform the liquid storage capsule. [Figure 15B] FIG. 15B is a cross-sectional view taken along line AA in FIG. 15A. [Figure 16] FIG. 13 is a flow diagram of a method for removing liquid from a liquid storage cavity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Embodiments of the present disclosure are described below with particular reference to liquid storage cavities such as capsules and chambers. However, it will be understood that the embodiments described herein are applicable to other types of cavities having a base and one or more walls. Although the following examples are described as being particularly useful in point-of-care diagnostic devices (such as microfluidic devices), it will be understood that such examples are not limited to practice in point-of-care diagnostic devices and may be practiced in other applications in which a liquid is stored in a cavity having an outlet.

[0023] FIG. 1A illustrates a liquid storage cavity 10 according to the present disclosure. Generally, the liquid storage cavity 10 has a base 12 and one or more walls 20 (e.g., one wall for a cylindrical cavity, four walls for a cavity having a quadrilateral area, etc.). The one or more walls 20 extend from the base 12. The liquid storage cavity 10 has a volume defined by the base 12 and the one or more walls 20. The liquid storage cavity 10 also has a perimeter 30 defined as a junction between the one or more walls 20 and the base 12. At least a portion of the perimeter 30 (and in some examples, the entirety of the perimeter) includes a peripheral recess 32 defined by the base 12 and at least one of the one or more walls 20. The peripheral recess 32 is configured to accommodate a volume of liquid 34 (e.g., as shown in FIG. 1B).

[0024] In the example shown in FIG. 1A , the wall(s) 20 defining the peripheral recess 32 extend outwardly from the interior 14 of the liquid storage cavity 10, thereby defining a wedge- or groove-shaped peripheral recess 32 extending laterally from the cavity 10.

[0025] To define the peripheral recess 32, the wall 20 of the liquid storage cavity 10 shown in FIG. 1A includes a first wall portion 22 and a second wall portion 24. The dashed line in FIG. 1A indicates the interface between the first wall portion 22 and the second wall portion 24. Specifically, in the example shown in FIG. 1A, the first wall portion 22 has a different curvature than the second wall portion 24. The first wall portion 22 extends between the base 12 and the second wall portion 24 around a portion of the peripheral portion 30 that includes the peripheral recess 32. In the example shown in FIG. 1A, the first wall portion 22 defines a fillet 36 between the second wall portion 24 and the base 12. The second wall portion 24 extends from the first wall portion 22 in a direction away from the base 12.

[0026] The volume of liquid 34 contained within the peripheral recess 32 provides a continuous fluid path around the periphery 30 (or part of) of the cavity 10. This means that liquid can be drawn from the peripheral recess 32 to the outlet 16 of the cavity 10 if a liquid bridge can be provided between the outlet 16 and the peripheral recess 32 (except in the case where the outlet 16 is coincident with the periphery 30, in which case a liquid bridge is not required). Drawing liquid from the peripheral recess 32 to the outlet 16 allows for a continuous flow of liquid out of the cavity outlet 16 without air bubbles being entrained in the liquid flow.

[0027] A continuous fluid path within the peripheral recess 32 is formed as a result of surface tension effects of the solution and the wetted contact angle of the solution with the cavity wall(s) 20 and base 12. As the volume of liquid 34 is drawn into the peripheral recess 32 by capillary action, the free surface energy of the liquid within the cavity 10 is minimized. Specifically, the shape and dimensions of the peripheral recess 32 provide an energetically favorable scenario that balances the liquid-solid and liquid-gas surface energies and allows a continuous liquid "wedge" to form within the peripheral recess 32 (e.g., as shown in FIG. 1B). This effect is observed whether the cavity 10 is oriented with its base facing down (e.g., FIG. 1A) or if the cavity 10 is oriented upside down with its base facing up such that the outlet is at the top of the cavity (e.g., FIG. 13A).

[0028] Importantly, the continuous liquid volume 34 in the peripheral recess 32 is not destroyed during the outflow of liquid from the cavity 10, even if the cavity 10 is only partially filled. This means that the trapped liquid volume 34 in the peripheral recess 32 provides a continuous guide for the outflow of liquid from the cavity 10 while the cavity 10 is emptying. A favorable surface energy balance can be exploited by pressurizing the cavity 10 to continuously outflow liquid from the cavity 10. For example, air can be injected into the cavity 10 through an inlet to the cavity 10 (not shown in FIG. 1A). In such an example, the air cannot escape through the outlet 16 until the outlet 16 is unobstructed by liquid. Thus, a continuous liquid volume can be evacuated from the cavity 10 by injecting a corresponding air volume into the cavity 10.

[0029] When extracting liquid from a nearly empty cavity 10, the flow rate should be controlled to minimize shear effects on the liquid. If the shear forces on the liquid are too great, the volume of liquid 34 in the peripheral recess 32 will collapse, which means that pressurization of the cavity 10 must be stopped in order for the liquid bridge to reform by capillary action. This is only an issue when the cavity 10 is nearly empty, since a liquid bridge is present when the cavity is, for example, half full.

[0030] The peripheral recess 32 can take the form of (i) a fillet 36 (e.g., as shown in FIG. 1A ), (ii) a chamfer providing a peripheral recess with a triangular cross-section (e.g., as shown in FIG. 9 ), (iii) a step providing a peripheral recess with a quadrilateral cross-section (e.g., as shown in FIG. 11 ), or (iv) a combination of the foregoing.

[0031] Parameters for optimizing the size of the peripheral recess 32 are detailed below. In general terms, the peripheral recess 32 is preferably sized so that the steady state cross-sectional shape of the liquid volume 34 in the peripheral recess 32 is (i) large enough to be able to draw liquid from any point along the peripheral recess 32 while maintaining a continuous supply of liquid to the peripheral recess 32 from other liquid volumes in the cavity 10, and (ii) small enough so that the volume of liquid 34 remaining in the peripheral recess 32 after the cavity 10 is emptied is not too large, to minimize liquid waste. Because the liquid volume 34 remains trapped in the peripheral recess 32 after the cavity is emptied, some liquid waste is inevitable. This is illustrated in FIG. 1B, which shows the liquid storage cavity 10 in an emptied state.

[0032] Figures 2A to 2C show a liquid storage cavity in the form of a liquid storage capsule 100 to which the peripheral recess shown in Figure 1A is applied. The liquid storage capsule 100 may be implemented in a point-of-care diagnostic device, such as a microfluidic cartridge, which may be received in an analytical device.

[0033] The liquid storage capsule 100 includes three portions: an inlet chamber 102, a liquid storage chamber 104, and an outlet chamber 106. These portions of the liquid storage capsule 100 are defined by a base 112 (shown in FIG. 2C) and a continuous wall 120 of the liquid storage capsule 120. The junction between the wall 120 and the base 112 defines a perimeter 130 of the liquid storage capsule 100 (also shown in FIG. 2C).

[0034] The upper surfaces of the inlet chamber 102 and the outlet chamber 106 can each be deformed by application of a downward force (e.g., by an actuator of an analytical device in which a microfluidic cartridge comprising the liquid storage capsule 100 is received). Application of the downward force to the inlet chamber 102 and the outlet chamber 106 deforms the material of the inlet chamber 102 and the outlet chamber 106, forcing it into contact with the base 112. Continued application of the downward force breaks the base 112 below the inlet chamber 102 and the outlet chamber 106, thereby forming the inlet 118 and the outlet 116 (as shown in FIG. 2D). It will be appreciated that the inlet 118 and the outlet 116 may be formed in other ways, such as by actuating a piercing element disposed below the inlet chamber 102 and the outlet chamber 106.

[0035] The wall 120 of the liquid storage capsule 100 comprises a first wall portion 122 and a second wall portion 124. The first wall portion 122 extends between the base 112 and the second wall portion 124 around a periphery 130 of the liquid storage capsule 100. The second wall portion 124 extends from the first wall portion 122, away from the base 112. In this example, the second wall portion 124 extends away from the first wall portion 122 and defines an upper surface of the liquid storage capsule 100.

[0036] The first wall 122 provides a fillet 136 between the base 112 and the second wall 124. The fillet 136 thus defines a peripheral recess 132 (best seen in FIG. 2C ) that extends around the periphery 130 of the liquid storage capsule 100 such that peripheral recesses are provided at the bases of the inlet chamber 102, the liquid storage chamber 104, and the outlet chamber 106.

[0037] Liquid is drawn into the peripheral recess by capillary action, thereby forming a ring-shaped volume of liquid 134 around the edges of the inlet chamber 102 and the outlet chamber 106, as shown in Figure 2D. If a liquid bridge is provided between the volume of liquid 134 in the peripheral recess and the outlet 116, for example, the volume of liquid 134 provides a continuous path for fluid to exit the liquid storage capsule 100 via the capsule outlet 116 when air is supplied via the capsule inlet 118.

[0038] Figures 3A and 3B are isometric and top views of a simulated volume of liquid remaining in a liquid storage capsule having a shape similar to that of the liquid storage capsule 100 shown in Figures 2A to 2C. There are slight differences in the shape of the liquid storage capsules shown in Figures 2A to 2C and Figures 3A and 3B (e.g., inlet and outlet chamber recesses), but for convenience, the same reference numbers are used. The simulations in Figures 3A and 3B show the remaining liquid volume after a first period of time while the liquid storage capsule 100 is emptying. Figures 3A and 3B show a liquid bridge 140 extending between the liquid volume 134 in the peripheral recess 132 and the capsule inlet 118 and outlet 116 (centered in the inlet chamber 102 and outlet chamber 106, respectively).

[0039] Figures 4A-4D show the remaining liquid volume after a second period of time (i.e., after during the emptying operation). As shown in Figures 4A-4D, most of the liquid has been expelled from the liquid storage chamber 104. However, the peripheral recess 132 still contains the liquid volume 134, and the liquid bridges 140 between the liquid volume 134 and the inlet 118 and outlet 116 persist (as best shown in Figures 4C and 4D), allowing continued liquid extraction from the liquid storage capsule 100.

[0040] Figures 5A to 5C show the remaining liquid volume after a third period (i.e. further during the emptying operation). As shown in Figures 5A to 5C, most of the liquid has been expelled from the liquid storage capsule 100 as a whole. The liquid bridge 140 between the liquid volume 134 in the peripheral recess 132 and the inlet 118 and outlet 116 has been broken, which means that the continuous outflow of liquid from the liquid storage capsule 100 has ended. That is, no more liquid can be extracted without introducing air bubbles between the already extracted liquid and the remaining liquid. Figures 5A to 5C show that the liquid volume 134 in the peripheral recess 132 remains after the emptying operation has ended.

[0041] 6A-6C show simulated volumes of liquid remaining in alternative liquid storage cavities. In particular, the liquid storage cavity simulated in FIGS. 6A-6C is a cylindrical chamber 200 (shown in outline only), which may be implemented, for example, as a mixing chamber. The chamber 200 comprises a base 212 and a continuous sidewall 220 that join at a periphery 230 of the chamber 200. A second wall 224 of the continuous sidewall 220 extends perpendicular to the base 212, such that the chamber 200 has a vertical wall. A peripheral recess 232 extends around the periphery 230 and is configured to contain a volume of liquid 234.

[0042] The chamber 200 includes an outlet 216 that provides an opening at the periphery 230 of the chamber 200. This means that, unlike the example shown in Figures 2A to 2D, the outlet 216 is coincident with the periphery 230. The coincidence of the outlet 216 with the periphery 230 means that no liquid bridge is required between the outlet and the periphery to remove liquid from the chamber 200. The outlet 216 is connected to a flow path 242. The chamber 200 also includes an inlet (not shown), which may be provided, for example, in the top of the side wall 220.

[0043] 6A to 6C show the remaining liquid volume after a first period of time during emptying of the chamber 200. The liquid volume 234 in the peripheral recess 232 is clearly visible. This volume is connected to the liquid being removed via the outlet 216.

[0044] Figures 7A and 7B show the remaining liquid volume after a second period of time (i.e. after the emptying operation). As shown in Figures 7A-7B, most of the liquid has been expelled from the chamber 200. A volume of air is shown in the flow path 242 connected to the outlet 216, meaning that no more liquid can be extracted without introducing air bubbles between the already extracted liquid and the remaining liquid. Figures 7A and 7B show that a liquid volume 234 remains in the peripheral recess 232 after the emptying operation has ended.

[0045] 8A-8C, parameters that define the shape of the fillet 36 are described. Preferably, the shape of the fillet 36 is optimized such that the cross-sectional shape of the liquid volume 34 in the peripheral recess 32 does not fall below a threshold cross-sectional area. The threshold is implemented to ensure that the liquid volume 34 in the peripheral recess 32 does not break off. Breaking of the liquid volume 34 would result in insufficient liquid volume 34 to draw liquid into the peripheral recess 32. Thus, the threshold ensures that liquid can be drawn from any point along the peripheral recess 32 while maintaining a continuous liquid supply from other liquid volumes in the cavity 10. The threshold cross-sectional area may be determined based on the properties of the liquid, such as viscosity, surface tension, and contact angle.

[0046] As an example applicable to a particular liquid having a viscosity between 0.005 and 0.015 Pa s, a surface tension between 0.01 and 0.06 N / m, and a wetting contact angle with the cavity wall / base between 5 and 40 degrees, the threshold cross-sectional area is 0.06 mm 2 It is 0.06mm 2 To achieve the threshold cross-sectional area, a fillet radius of at least 0.15 mm is required.

[0047] It is also preferable to keep the volume of liquid 34 retained within the peripheral recess 32 below an upper limit, since a volume of liquid 34 is retained within the peripheral recess 32 after the cavity 10 is emptied, which means that the retained liquid volume 34 cannot be removed from the cavity 10. The upper limit will depend on the threshold cross-sectional area of ​​the particular liquid.

[0048] Continuing with the example applicable to a particular liquid having a viscosity of 0.005-0.015 Pa s, a surface tension of 0.01-0.06 N / m, and a wetting contact angle with the cavity wall / base of 5-40 degrees, the fillet radius is preferably 1 mm or less. The preferred range of fillet radius for such liquids is 0.2-0.6 mm.

[0049] Figures 8A to 8C are simulations of the liquid volume retained in the peripheral recess with different fillet radii. The simulations are performed with liquid properties of 0.005 Pa s viscosity, 0.018175 N / m surface tension, and 20 degrees wetting contact angle. Figure 8A is a simulation of a cavity with a 0.6 mm fillet radius. With a 0.6 mm fillet radius, the cross-sectional area of ​​the liquid in the peripheral recess is 0.11 mm 2 Figure 8B shows a simulation of a cavity with a fillet radius of 0.4 mm. With a fillet radius of 0.4 mm, the cross-sectional area of ​​the liquid in the peripheral recess is 0.082 mm. 2 Figure 8C shows a simulation of a cavity with a fillet radius of 0.2 mm. With a fillet radius of 0.2 mm, the cross-sectional area of ​​the liquid in the peripheral recess is 0.063 mm. 2 It was.

[0050] The table in Appendix 1 shows the cross-sectional area of ​​the liquid volume 34 in the peripheral recess 32 for other combinations of liquid properties. These liquid properties include the direction of gravity. This property is taken into consideration because the peripheral recess 32 can facilitate emptying of the cavity "upside down" (i.e., with the outlet 16 at the top of the cavity 10). The volume of bubble-free liquid dispensed from the liquid storage cavity 10 is maximized when the cavity has a sufficiently shallow depth (e.g., 5 mm or less) such that the surface tension of the liquid overcomes the force of gravity on the liquid, resulting in a vertical column of liquid between its upper and lower inner surfaces. In the table in Appendix 1, a gravity direction of "1" indicates that the outlet 16 is at the bottom of the cavity 10, and a gravity direction of "-1" indicates that the outlet 16 is at the top of the cavity 10.

[0051] 9 shows an alternative liquid storage cavity 300 in which the first wall 322 extends at an acute angle between the base 312 and the second wall 324. This means that the first wall 322 provides a chamfer 344 between the base 312 and the second wall 324. The peripheral recess 332 therefore has a triangular cross-section.

[0052] The shape of the chamfer 344 can be defined by two characteristics, the chamfer depth and the chamfer angle, both of which are shown diagrammatically in Figure 9. The chamfer depth is the lateral distance between the junction between the first wall 322 and the second wall 324, and is the maximum lateral outward extension of the chamfer 344 (in other words, how far the chamfer 344 extends laterally from its junction with the second wall 324). The chamfer angle is the angle between the first wall 322 and the base 312.

[0053] The chamfer 344 retains liquid in a manner similar to the fillet 36 described above. If the chamfer 344 is too large, too much of the liquid volume will be retained in the peripheral recess 332, which means that a percentage of the liquid in the cavity 300 will be lost. However, similar to the fillet 36, it is preferred that the cross-sectional area of ​​the liquid volume 334 in the peripheral recess 332 is at least a threshold value.

[0054] For example, the threshold cross-sectional area is 0.06 mm 2 To achieve this threshold, the chamfer depth should be at least 0.2 mm and the chamfer angle should be at least 20 degrees. To prevent significant amounts of liquid from being retained in the elongated peripheral recess 332 after emptying, the chamfer depth should be no more than 0.5 mm and / or the chamfer angle should be no more than 45 degrees.

[0055] 10A-10E are simulations of liquid volumes retained in peripheral recesses with different chamfer geometries. Simulations were performed with properties of dynamic viscosity of 0.01 Pa·s, surface tension of 0.054 N / m, wetting contact angle of 15 degrees, and specific gravity of 1.02. Gravity was in the direction of the arrow shown in FIGS. 10A-10E. Another parameter that was varied in these simulations was the angle of the second wall 322 relative to the base 312. Second wall angles of 90 degrees (FIGS. 10A and 10B), 60 degrees (FIGS. 10C and 10D), and 30 degrees (FIG. 10E) were simulated.

[0056] 10A is a simulation of a cavity having a chamfer depth of 0.25 mm, a chamfer angle of 45 degrees, and a second wall angle of 90 degrees (i.e., such that the second wall 324 extends substantially perpendicular to the base 312). With this cavity and chamfer shape, the cross-sectional area of ​​the liquid in the peripheral recess is 0.220 mm 2 FIG. 10B is a simulation of a cavity with a chamfer depth of 0.75 mm, a chamfer angle of 45 degrees, and a second wall angle of 90 degrees. With this cavity and chamfer shape, the cross-sectional area of ​​the liquid in the peripheral recess was 0.268 mm 2 Figure 10C shows a simulation of a cavity with a chamfer depth of 0.75 mm, a chamfer angle of 30 degrees, and a second wall angle of 60 degrees. With this cavity and chamfer shape, the cross-sectional area of ​​the liquid in the peripheral recess was 0.249 mm 2Figure 10D shows a simulation of a cavity with a chamfer depth of 1.125 mm, a chamfer angle of 30 degrees, and a second wall angle of 60 degrees. With this cavity and chamfer shape, the cross-sectional area of ​​the liquid in the peripheral recess is 0.276 mm 2 Figure 10E shows a simulation of a cavity with a chamfer depth of 0.937 mm, a chamfer angle of 27.5 degrees, and a second wall angle of 30 degrees. With this cavity and chamfer shape, the cross-sectional area of ​​the liquid in the peripheral recess is 0.253 mm 2 It was.

[0057] 11 shows a further alternative liquid storage cavity 400 in which the first wall 422 defines a peripheral recess 432 in the form of a step 446. In particular, the first wall 422 comprises a first portion 426 joined to the second wall 424 and extending outwardly from the second wall 424 (i.e., outwardly from the interior 414 of the liquid storage cavity 400). The first wall 422 also comprises a second portion 428 extending between the first portion 426 and the base 412. This means that the first and second portions 426, 428 of the first wall 422 define a quadrilateral (e.g., square, rectangular, trapezoidal) cross-section of the peripheral recess 432.

[0058] The shape of the step 446 can be defined by two characteristics: the width of the step 446 (i.e., the length of the first portion 426 of the first wall 422) and the height of the step 446 (i.e., the length of the second portion 428 of the first wall 422). Both of these characteristics are shown diagrammatically in FIG.

[0059] The step 446 retains liquid in a manner similar to the fillet 36 and chamfer 334 described above. If the step 446 is too large, too much liquid will be retained in the peripheral recess 432, meaning that a percentage of the liquid in the cavity 400 will be lost. However, similar to the fillet 36, it is preferred that the cross-sectional area of ​​the liquid volume 434 in the peripheral recess 432 is at least a threshold value.

[0060] For example, the threshold cross-sectional area is 0.06 mm 2To achieve this threshold, the step width should be at least 0.2 mm and the step height should be at least 0.2 mm. To prevent significant amounts of liquid from being retained in the elongated peripheral recess 332 after emptying, the step width should be no more than 0.5 mm and / or the step height should be no more than 0.5 mm.

[0061] 12A to 12F are simulations of the liquid volume retained in peripheral recesses with different step shapes. The simulations were performed using properties of dynamic viscosity of 0.01 Pa·s, surface tension of 0.054 N / m, wetting contact angle of 15 degrees, and specific gravity of 1.02. Gravity was in the direction of the arrow shown in FIGS. 12A to 12F. Another parameter that was varied in these simulations was the angle of the second wall 422 relative to the base 412. Second wall angles of 60 degrees (FIGS. 12A to 12E) and 30 degrees (FIG. 12F) were simulated. An additional parameter that was varied in these simulations was the height of the cavity 400. Cavity heights of 2.5 mm (FIGS. 12A to 12D), 3 mm (FIG. 12E), and 2.75 mm (FIG. 12F) were simulated.

[0062] FIG. 12A is a simulation of a cavity with a step height of 0.25 mm, a step width of 0.645 mm, a cavity height of 2.5 mm, and a second wall angle of 60 degrees. With this cavity and step shape, the cross-sectional area of ​​the liquid in the peripheral recess is 0.311 mm 2 FIG. 12B is a simulation of a cavity with a step height of 0.375 mm, a step width of 0.375 mm, a cavity height of 2.5 mm, and a second wall angle of 60 degrees. With this cavity and step shape, the cross-sectional area of ​​the liquid in the peripheral recess was 0.228 mm 2 FIG. 12C is a simulation of a cavity with a step height of 0.25 mm, a step width of 0.39 mm, a cavity height of 2.5 mm, and a second wall angle of 60 degrees. With this cavity and step shape, the cross-sectional area of ​​the liquid in the peripheral recess was 0.250 mm 2FIG. 12D is a simulation of a cavity with a step height of 0.5 mm, a step width of 0.785 mm, a cavity height of 2.5 mm, and a second wall angle of 60 degrees. With this cavity and step shape, the cross-sectional area of ​​the liquid in the peripheral recess is 0.238 mm 2 It was.

[0063] FIG. 12E is a simulation of a cavity with a step height of 0.25 mm, a step width of 0.39 mm, and a second wall angle of 60 degrees (similar to FIG. 12C), except that the cavity height has been increased to 3 mm. With this cavity and step shape, the cross-sectional area of ​​the liquid in the peripheral recess is 0.320 mm 2 FIG. 12F is a simulation of a cavity with a step height of 0.25 mm, a step width of 0.68 mm, a cavity height of 2.75 mm, and a second wall angle of 30 degrees. With this cavity and step shape, the cross-sectional area of ​​the liquid in the peripheral recess is 0.371 mm 2 It was.

[0064] As mentioned above, implementing the peripheral recess 32 allows the cavity (e.g., capsule) to be emptied when the cavity is "upside down" (i.e., with the outlet 16 at the top of the cavity 10). The volume of bubble-free liquid expelled from the liquid storage cavity 10 is maximized when the cavity has a sufficiently shallow depth (e.g., 5 mm or less) such that a vertical column of liquid is established between its upper and lower inner surfaces as a result of the surface tension of the liquid overcoming the force of gravity acting on the liquid.

[0065] Figure 13A is an example of a liquid storage cavity 500 with an outlet 516 at the top of the cavity 500 (i.e., the base 512 is positioned upwards, meaning that the liquid storage cavity 500 is upside down). To ensure that a liquid column is established between the top and bottom surfaces, the cavity height (shown in Figure 13B) should be less than 5mm, preferably less than 3.5mm, and more preferably less than 3mm. Above 5mm, the effect of surface tension is overcome by gravity.

[0066] When the cavity 500 is emptied in this orientation, droplets 548 may form at the bottom of the cavity 500, as shown in Figure 13A for a cavity with a 90 degree second wall angle. Liquid also pools at the bottom of the cavity when the second wall is at 60 degrees, as shown in Figure 13B. To minimize pooling of liquid and the formation of droplets, the second wall angle (shown diagrammatically in Figure 13B) is preferably less than 55 degrees (e.g., as shown in Figure 14C).

[0067] Pooling of liquid and the formation of droplets can also be minimized by avoiding the provision of a flat surface at the bottom of the cavity (e.g., as also shown in FIG. 14C) or by providing a curved surface at the bottom of the cavity (e.g., as shown in FIGS. 2A-2D). In other words, when the second wall 524 defines a top surface of the cavity 500 that is non-parallel to the base, pooling of liquid and the formation of droplets are minimized.

[0068] When the outlet 516 is centered at the top of the cavity 500 (i.e., in the center of the periphery 530 of the cavity 500), the aspect ratio of the cross-sectional width to height should be 5:2 or less (in other words, the cavity width should be 2.5 times the cavity height or less).

[0069] Although Figures 13A and 13B show inverted emptying of a cavity 500 having a peripheral recess 532 with a step shape, it will be appreciated that a cavity having a peripheral recess defined by a chamfer and fillet can also be emptied in this configuration, provided the cavity is shallow enough so that a liquid column forms between the upper and lower surfaces.

[0070] 14A to 14E are simulations of the liquid volume retained in the peripheral recess when the cavity 500 is emptied with an outlet 516 at the top of the cavity. The simulations were performed using properties of dynamic viscosity of 0.01 Pa·s, surface tension of 0.054 N / m, wetting contact angle of 15 degrees, and specific gravity of 1.02. Gravity was in the direction of the arrow shown in FIGS. 14A to 14E. Another parameter that was varied in these simulations was the angle of the second wall 522 relative to the base 512. Second wall angles of 90 degrees (FIG. 14A), 60 degrees (FIG. 14B), and 30 degrees (FIG. 14C) were simulated. An additional parameter that was varied in these simulations was the height of the cavity 500. Cavity heights of 3 mm (FIGS. 14A and 14B) and 2.75 mm (FIG. 14C) were simulated.

[0071] FIG. 14A is a simulation of inverted emptying of a cavity with a step height of 0.25 mm, a step width of 0.25 mm, a cavity height of 3 mm, and a second wall angle of 90 degrees. With this cavity and step shape, the cross-sectional area of ​​the liquid in the peripheral recess is 0.301 mm 2 FIG. 14B shows a simulation of inverted emptying of a cavity with a step height of 0.25 mm, a step width of 0.39 mm, a cavity height of 3 mm, and a second wall angle of 60 degrees. With this cavity and step shape, the cross-sectional area of ​​the liquid in the peripheral recess is 0.314 mm 2 FIG. 14C is a simulation of a cavity with a step height of 0.25 mm, a step width of 0.68 mm, a cavity height of 2.75 mm, and a second wall angle of 30 degrees. With this cavity and step shape, the cross-sectional area of ​​the liquid in the peripheral recess was 0.370 mm 2 It was.

[0072] As mentioned above, a liquid bridge is required between the peripheral recess 32 and the outlet 16 to ensure that liquid is withdrawn from the peripheral recess 32 during emptying of the cavity 10. In the case of a centrally located outlet 16 (i.e. in the centre of the periphery 30), one way to provide a liquid bridge is to deform the cavity 10 such that a saddle 50 is provided between the periphery 30 and the outlet 16 (as shown diagrammatically in FIG. 15A). The saddle 50 provides a path between the periphery 30 and the outlet 16 along which the upper surface of the cavity 10 is recessed such that the distance between the upper and lower surfaces is shorter along the saddle 50 than in other areas of the cavity 10. This provides a path for liquid flow between the periphery 30 and the outlet 16 as the surface tension of the liquid retains the liquid along the path defined by the saddle 50.

[0073] An actuator 52 having ridges 54 may be used to deform the cavity 10 to provide the saddle 50 when deforming the cavity 10 to form the inlet and outlet. The ridges 54 are visible in the cross-sectional view of the actuator 52 shown in Figure 15B. The actuator may be a component of an analytical device in which a microfluidic cartridge with the cavity 10 is received.

[0074] Figure 16 is a flow diagram of a method 60 of removing liquid from a liquid storage cavity. It will be appreciated that the features of method 60 need not be performed in the order depicted in Figure 16, and that certain steps may be performed in different orders. As an example, method feature 66 may be performed before method feature 64. Thus, method 60 is not limited to the particular order depicted in Figure 16 and described below.

[0075] At 62, a liquid storage cavity is provided. The liquid storage cavity may be any of the liquid storage cavities described with reference to Figures 1A to 15A. For example, the liquid storage cavity may be a capsule (e.g., as shown in Figures 2A to 2D), or a chamber (e.g., as shown in Figures 6A to 6C). Other examples (e.g., reservoirs, channels, etc.) are also envisioned.

[0076] At 64, an inlet to and an outlet from the liquid storage cavity are provided. Providing an outlet from the liquid storage cavity may comprise providing the liquid storage cavity with a permanent outlet (e.g., in the case of the chambers shown in Figures 6A to 6C). If the liquid storage cavity has a permanent outlet, providing the outlet may further comprise opening a valve in a liquid processing device in which the liquid storage cavity is implemented. Alternatively, providing an outlet from the liquid storage cavity may comprise creating an outlet from the liquid storage cavity. Creating an outlet may comprise deforming the liquid storage cavity to cause a break in the cavity material (e.g., as described with reference to Figures 2A to 2D), or perforating the cavity using a piercing element.

[0077] Similarly, providing an inlet to the liquid storage cavity may comprise providing the liquid storage cavity with a permanent inlet, or creating an inlet to the liquid storage cavity (e.g., by breaking, perforating, or destroying the cavity material).

[0078] At 66, the liquid storage cavity is oriented such that the outlet is located on an upper side of the liquid storage cavity. As explained above, the liquid storage cavity may be oriented in this manner prior to providing the inlet and outlet to the liquid storage cavity. As an example, the liquid storage cavity may be mounted to a liquid treatment device in this orientation. The liquid treatment device may then be received in an analytical device having an actuable piercing element. The cavity material may then be pierced by the piercing element of the analytical device.

[0079] At 68, gas is supplied via the inlet to expel the liquid from the outlet. The gas may be supplied, for example, via a pneumatic actuator in fluid communication with the inlet. As an example, the inlet to the liquid storage cavity may be in fluid communication with a pneumatic port of a liquid treatment device in which the liquid storage cavity is implemented. The liquid treatment device may then be received in an analytical device having a pneumatic supply system. Air may be supplied to the inlet by the pneumatic supply system of the analytical device via a pneumatic port of the liquid treatment device.

[0080] The gas displaces liquid within the liquid storage cavity, which is drawn into a peripheral recess of the liquid storage cavity by capillary action, and the liquid within the peripheral recess provides a continuous feed path from the remainder of the liquid storage cavity to an outlet, thereby maximizing the amount of bubble-free liquid that is discharged from the liquid storage cavity.

[0081] In some embodiments, the peripheral recess 32 may not extend around the entire circumference of the cavity 10. Additionally, a combination of steps, chamfers, and fillet shapes may be used to define the peripheral recess 32.

[0082] While the above discussion has focused on capsules and chambers as examples of cavities that may include peripheral recesses, peripheral recesses may also be included in other fluidic components, such as channels. When incorporated into a channel, the peripheral recess aids in the flow of liquid through the channel.

[0083] The singular terms "a" and "an" should not be construed to mean "only one." Rather, unless otherwise specified, they should be construed to mean "at least one" or "one or more." "Comprising," including "comprises" and "comprises," and derivatives thereof, includes each of the listed features but does not exclude the inclusion of one or more additional features.

[0084] The above-described embodiments have been described by way of example only, and the described embodiments are to be considered in all respects only as illustrative and not restrictive. It will be understood that modifications may be made to the described embodiments without departing from the scope of the invention. It will also be apparent that there are many variations which have not been described but which are within the scope of the appended claims.

[0085] [Table 1] [Table 2] [Table 3] [Table 4] [Table 5]

Claims

1. A liquid storage cavity, comprising: A base and one or more walls extending from the base, the liquid storage cavity having a volume defined by the base and the one or more walls; a periphery where the one or more walls are joined to the base, at least a portion of the periphery including a peripheral recess defined by the base and at least one of the one or more walls, the peripheral recess configured to accommodate a volume of liquid; A liquid storage cavity comprising:

2. The liquid storage cavity of claim 1 , wherein the at least one of the one or more walls extends outwardly from an interior of the liquid storage cavity to define the peripheral recess.

3. The at least one of the one or more walls a first wall portion and a second wall portion, the first wall portion extending between the base portion and the second wall portion around a portion of the periphery; 3. The liquid storage cavity of claim 1 or claim 2, wherein the second wall extends from the first wall in a direction away from the base.

4. The liquid storage cavity of claim 3 , wherein the first wall defines a fillet between the second wall and the base.

5. The liquid storage cavity of claim 4 , wherein the radius of the fillet defined by the first wall is between 0.15 mm and 1 mm.

6. The liquid storage cavity of claim 5 , wherein the radius of the fillet defined by the first wall is between 0.2 mm and 0.6 mm.

7. The liquid storage cavity of claim 3 , wherein the first wall extends at an acute angle between the base and the second wall such that the peripheral recess has a triangular cross-section.

8. The liquid storage cavity of claim 7 , wherein the acute angle between the first wall and the base is less than or equal to 45 degrees.

9. 8. The liquid storage cavity of claim 7, wherein the first wall extends laterally beyond the junction between the first wall and the second wall a distance of 0.5 mm or less.

10. The first wall portion includes a first portion and a second portion, the first portion of the first wall is joined to the second wall and extends from the interior to the exterior of the liquid storage cavity in a direction substantially parallel to the base; 4. The liquid storage cavity of claim 3, wherein the second portion of the first wall extends between the first portion and the base such that an elongated recess has a quadrilateral cross-section.

11. The liquid storage cavity of claim 10 , wherein the first portion of the first wall has a width of 0.5 mm or less.

12. The liquid storage cavity of claim 10 , wherein the second portion of the second wall has a height of 0.5 mm or less.

13. The liquid storage cavity of claim 3 , wherein the liquid storage cavity is a capsule.

14. 14. The liquid storage cavity of claim 13, wherein the height of the liquid storage cavity is 5 mm or less.

15. 15. The liquid storage cavity of claim 14, wherein the height of the liquid storage cavity is 3.5 mm or less.

16. The liquid storage cavity of claim 3 , wherein the second wall extends away from the base in a direction substantially perpendicular to the base.

17. 3. A liquid storage cavity as claimed in claim 1 or claim 2, wherein the peripheral recess extends around the entire periphery of the liquid storage cavity.

18. The liquid storage cavity of claim 1 or claim 2, further comprising an outlet in the base.

19. The liquid storage cavity of claim 18 , wherein the outlet is coincident with a portion of the periphery.

20. 1. A method of removing liquid from a liquid storage cavity, comprising: Providing a liquid storage cavity according to claim 1 or 2; providing an inlet to and an outlet from said liquid storage cavity; orienting the liquid storage cavity such that the outlet is located above the liquid storage cavity; supplying a gas through the inlet to expel liquid from the outlet; A method comprising:

21. 21. The method of claim 20, wherein providing the outlet from the liquid storage cavity comprises providing a liquid storage cavity according to claim 18.

22. 21. The method of claim 20, wherein providing the outlet from the liquid storage cavity comprises creating the outlet in the base of the liquid storage cavity.

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