Ventilated piston

Abstract

The vent piston is receivable within the fluid conduit and includes a plunger body defining a fluid flow path extending between an upstream end and a downstream end, a fluid check valve disposed across the fluid flow path, the fluid check valve being configurable to restrict passage of gas from the downstream end to the upstream end of the fluid flow path and to restrict passage of liquid from the upstream end to the downstream end of the fluid flow path, and a fluid flow restricting member disposed across the fluid flow path to restrict fluid flow within the fluid flow path, the fluid check valve being axially fixed relative to the plunger body.

Description

[Technical Field]

[0001] This disclosure relates to a venting piston. More particularly, this disclosure relates to a venting piston suitable for use in a syringe or fluid system for venting gas while preventing the escape of liquid. This disclosure also relates to a method for filling and operating a syringe having a venting piston. [Background technology]

[0002] Syringes are commonly used for handling liquids, such as for testing or when administering medication. Air bubbles can be introduced into a syringe during filling. For example, gas can be introduced during withdrawal of a medication from a vial. In many cases, the presence of air bubbles in a syringe can be undesirable. Syringes can also be used in fluid systems, such as microfluidic devices, where removal of air bubbles can be desirable.

[0003] Generally, to expel air bubbles from a syringe, the user must invert the syringe and tap the syringe barrel to dislodge the air bubbles from the base of the plunger. The user then depresses the plunger until all the gas (and often a small amount of liquid) has exited the needle. This process is a. When capillary forces or fluid viscosity make it difficult or impractical to remove air bubbles from the syringe barrel; b. When handling of syringes should be minimized, such as when working with hazardous substances, c. It can be problematic in many scenarios, including but not limited to when the operator is frail or otherwise has difficulty using a regular syringe.

[0004] Furthermore, this gas evacuation procedure may not be possible in some fluid system situations.

[0005] It is therefore desirable to provide a device for more easily expelling air bubbles from a syringe or fluid system.

[0006] Any discussion of documents, acts, materials, devices, articles or the like which has been included in this specification should not be construed as an admission that any or all of such matters existed before the priority date of each of the appended claims and therefore form part of the base of the prior art or were common general knowledge in the art relevant to the present disclosure. Summary of the Invention

[0007] According to one aspect of the present disclosure, there is provided a vent piston receivable within a fluid conduit, the piston comprising: a plunger body defining a fluid flow passage extending between an upstream end and a downstream end; a fluid check valve disposed across the fluid flow path, the fluid check valve being configurable to prevent the passage of gas from the downstream end to the upstream end of the fluid flow path and to prevent the passage of liquid from the upstream end to the downstream end of the fluid flow path; A fluid flow restricting member disposed across the fluid flow path to restrict fluid flow within the fluid flow path is provided.

[0008] According to another aspect of the present disclosure, there is provided a vent piston receivable within a fluid conduit, the piston comprising: a plunger body defining a fluid flow passage extending between an upstream end and a downstream end, the fluid flow passage facilitating venting of fluid from the plunger body; a fluid check valve disposed across the fluid flow path, the fluid check valve being configurable to inhibit the passage of gas from the downstream end to the upstream end of the fluid flow path and to inhibit the passage of liquid from the upstream end to the downstream end of the fluid flow path; A fluid flow restricting member disposed across the fluid flow path to restrict fluid flow within the fluid flow path is provided.

[0009] The fluid check valve may be axially fixed relative to the plunger body.

[0010] According to another aspect of the present disclosure, there is provided a vent piston receivable within a fluid conduit, the piston comprising: a plunger body defining a fluid flow passage extending between an upstream end and a downstream end; a fluid check valve disposed across the fluid flow path, the fluid check valve being configurable to inhibit the passage of gas from the downstream end to the upstream end of the fluid flow path and to inhibit the passage of liquid from the upstream end to the downstream end of the fluid flow path; a fluid flow suppression member disposed across the fluid flow path to suppress fluid flow within the fluid flow path; The fluid check valve is provided with a vented piston that is axially fixed relative to the plunger body.

[0011] The fluid flow passage may facilitate venting of fluid from the plunger body.

[0012] Any of the above aspects may further include one or more of the following features.

[0013] Venting fluid from the plunger body can include allowing fluid to exit the plunger body. The fluid flow path can facilitate venting from the plunger body via a downstream end of the fluid flow path. This can be accomplished, for example, by a plunger body with an open downstream end. The open downstream end can be in fluid communication with the surrounding atmosphere and / or a downstream portion of the fluid conduit.

[0014] The fluid flow restricting member may be axially fixed relative to the plunger body and / or the fluid check valve. The fluid check valve may be axially fixed relative to the plunger body and / or the fluid flow restricting member. In other embodiments, the fluid flow restricting member may be axially movable relative to the plunger body and / or the fluid check valve. In some embodiments, the fluid flow restricting member may be removable from the piston.

[0015] The fluid conduit may include an interior surface, and the piston may form a fluid seal with the interior surface of the fluid conduit. The piston may separate the fluid conduit into an upstream section and a downstream section. A fluid flow passage may extend through the plunger body and fluidly connect the upstream and downstream sections of the fluid conduit.

[0016] The plunger body can be adapted to form a fluid seal with the interior surface of the fluid conduit. In some embodiments, the piston can further include a sealing member for forming a fluid seal between the piston and the interior surface of the fluid conduit. For example, the sealing member can include a stopper at the distal end of the piston. The stopper can include an axial channel in fluid communication with the fluid flow path to fluidly connect the upstream and downstream sections of the fluid conduit. The stopper can be axially secured to one or more of the plunger body, the fluid check valve, and / or the fluid flow restricting member.

[0017] In some embodiments, the plunger can have a sidewall defining an internal lumen that provides a fluid flow path. In some embodiments, the fluid flow path can extend generally along or parallel to the elongation axis of the plunger body. In other embodiments, the fluid flow path can extend transversely to the axis of the plunger body, or can be curved or angled. The lumen can include one or more downstream openings that define a downstream end of the fluid flow path. The openings can include, for example, an open end of the lumen and / or an opening through the sidewall of the plunger.

[0018] The fluid check valve may include a hydrophilic porous material and a hydrophobic porous material. Examples of such fluid check valves are disclosed in applicant's earlier filed patent application PCT specification PCT / AU2020 / 050902, which is incorporated herein by reference in its entirety.

[0019] The hydrophobic porous material may be disposed adjacent to the hydrophilic porous material. One side of the hydrophilic porous material may be in fluid communication with an upstream end of the fluid flow path, and one side of the hydrophobic porous material may be in fluid communication with a downstream end of the fluid flow path. The hydrophilic porous material may be configured to retain liquid from the upstream section to prevent passage of gas from the downstream section to the upstream section, and the hydrophobic porous material may be configured to inhibit passage of liquid from the upstream section to the downstream section.

[0020] The hydrophilic porous material may be positioned upstream of the hydrophobic porous material.

[0021] At least one of the hydrophilic porous material and the hydrophobic porous material may define a plurality of pores, the plurality of pores having a median pore diameter ranging from about 0.003 microns to about 10 microns. In some embodiments, the plurality of pores has a median pore diameter of less than about 1 micron, e.g., about 0.005 microns. The hydrophilic porous material may define a plurality of first pores having a second median pore diameter of less than about 0.5 microns. The hydrophobic porous material may define a plurality of second pores having a second median pore diameter of less than about 0.3 microns.

[0022] In some embodiments, the hydrophobic porous material and the hydrophilic porous material may be in direct contact with each other. In other embodiments, the hydrophobic porous material and the hydrophilic porous material are spaced apart from each other. For example, the hydrophobic porous material and the hydrophilic porous material may be spaced apart from each other by a distance greater than about 0 mm and less than about 2 mm. The hydrophobic porous material and the hydrophilic porous material may be separated by a material or medium that allows fluid passage or transmission. In some embodiments, the hydrophobic porous material and the hydrophilic porous material may be separated by gaps or voids.

[0023] The hydrophilic porous material may comprise a hydrophilic membrane. The hydrophobic porous material may comprise a hydrophobic membrane. In some embodiments, the hydrophobic membrane and / or the hydrophilic membrane comprises a polytetrafluoroethylene substrate. The fluid check valve may be considered to comprise a dual-layer hydrophobic and hydrophilic membrane system.

[0024] The hydrophilic porous material may include a hydrophilic coating. The hydrophobic porous material may include a hydrophobic coating. In some embodiments, the hydrophobic material may include a textured or patterned surface, where the surface texture or pattern inhibits wetting of the surface. In some embodiments, the hydrophilic material may include a textured or patterned surface, where the surface texture or pattern promotes wetting of the surface.

[0025] When the hydrophilic porous material is exposed to a liquid, the fluid check valve may inhibit the passage of gas from the downstream end to the upstream end with a backflow pressure limit of about -80 kPa or about -90 kPa. In other embodiments, the backflow pressure limit may be significantly higher. The combination of membrane material and pore size may be selected to provide the desired backflow pressure limit.

[0026] The hydrophobic porous material can be configured to inhibit the passage of liquid from the upstream end to the downstream end with a leak pressure limit of about 250 kPa or about 400 kPa. In some embodiments, the hydrophobic porous material is configured to inhibit the passage of liquid from the upstream end to the downstream end with a leak pressure limit of about 150 kPa. In some embodiments, the hydrophobic porous material is configured to inhibit the passage of liquid from the upstream end to the downstream end with a leak pressure limit of about 100 kPa. The seal between the hydrophobic material and the plunger body can also be configured to withstand pressures at least up to the leak pressure limit.

[0027] In some embodiments, the fluid check valve may further comprise a retention body. The retention body may define a fluid opening having an upstream side and a downstream side, and the hydrophilic and hydrophobic porous materials are disposed over the fluid opening.

[0028] The retention body may include a coupling member for connecting the retention body to the plunger body such that the fluid opening is in fluid communication with the fluid flow path. For example, the coupling member may include a luer connector.

[0029] The retaining body may further comprise a seat for connection to a sealing member for sealing between the piston and an interior surface of the fluid conduit.

[0030] The retention body may include a first portion and a second portion connectable to one another to cooperatively retain the hydrophilic and hydrophobic porous materials, and the first and second portions may be molded or bonded together to form a friction fit.

[0031] One of the first and second parts can be shaped to define a recess, and a section of the other of the first and second parts can be shaped to fit within the recess so that the first and second parts are joined together. At least a section of each of the hydrophilic and hydrophobic porous materials can be located within the recess. For example, in some embodiments, the first part can include a recess configured to receive the hydrophilic and hydrophobic porous materials, and the second part can include a protrusion receivable within the recess and configured to retain the hydrophilic and hydrophobic porous materials within the recess.

[0032] The fluid flow restricting member may be positioned downstream of the fluid check valve. In other embodiments, the fluid flow restricting member may be positioned upstream of the fluid check valve.

[0033] The fluid flow restricting member may be configurable to selectively restrict fluid flow within the fluid flow path, for example, the fluid flow restricting member may be configurable between an open configuration in which fluid flow is substantially unrestricted and a closed (or sealed) configuration in which fluid flow is restricted.

[0034] The fluid flow restricting member may comprise a releasable or frangible seal. In some embodiments, the fluid flow restricting member may comprise a plug configured to seal the fluid flow passage. That is, the plug may provide a fluid-tight seal within the fluid flow passage and inhibit the passage of fluid therethrough. The plug may be at least partially receivable within the plunger body. For example, the plug may be receivable at a downstream end of the fluid flow passage to seal the fluid flow passage, i.e., inhibit fluid flow along the fluid flow passage. The plug may be removable from the fluid flow passage to allow fluid to flow along the fluid flow passage. In other embodiments, the plug may comprise a pierceable, frangible, or otherwise releasable seal.

[0035] In other embodiments, the fluid flow restricting member may comprise a deformable portion at the downstream end of the plunger body. The deformable portion may include, for example, a flexible wall. The flexible wall may be integral with and / or formed integrally with a sidewall of the plunger body. The flexible wall may be movable between an open position and a closed position, in which the flexible wall at least partially blocks the fluid flow path, thereby restricting fluid flow. The flexible wall may be resiliently biased toward the open position. The flexible wall may be resiliently deformable to the closed position under the application of compressive pressure (e.g., applied by a user's finger).

[0036] The fluid flow suppressing member may comprise a fluid flow control member. That is, the fluid flow suppressing member may be configured to control fluid flow within the fluid flow path. In some embodiments, the fluid flow suppressing member may be configured to promote asymmetric flow within the fluid flow path. That is, the fluid flow suppressing member may be configured to suppress fluid flow in one direction to a greater extent than in the opposite direction. For example, the fluid flow suppressing member may suppress reverse fluid flow in the upstream direction. In some embodiments, the fluid flow suppressing member may allow flow through the fluid flow path in only one direction. The fluid flow suppressing member may selectively seal or block the fluid flow path. The fluid flow suppressing member may be configured to allow fluid flow from the upstream end to the downstream end of the fluid flow path and suppress fluid flow from the downstream end to the upstream end of the fluid flow path. Alternatively, or additionally, the fluid flow suppressing member may be configured to allow fluid flow from the downstream end to the upstream end of the fluid flow path and suppress fluid flow from the upstream end to the downstream end of the fluid flow path.

[0037] The fluid flow restricting member may include a valve. In some embodiments, the fluid flow restricting member may include a passive valve. For example, the fluid flow restricting member may comprise one or more of a diaphragm valve (e.g., a duckbill or slit valve), a swing check valve, a lift check valve, a piston check valve, a ball check valve, a switchable check valve, a spring valve, or other suitable passive valve. In other embodiments, the fluid flow restricting member may include an actuatable valve, such as an adjustable or switching valve (e.g., a screw valve, a butterfly valve, a needle valve, a gate valve). The valve may be configurable between an open configuration and a closed configuration. The valve may allow fluid flow in the fluid flow path while in the open configuration and may restrict fluid flow in the fluid flow path while in the closed configuration.

[0038] In another embodiment, the fluid flow restricting member may comprise an expandable balloon. The fluid flow restricting member may further comprise a mesh that restricts movement of the balloon in the upstream direction but allows the balloon to expand freely. In this embodiment, the balloon may trap gas that passes through the fluid check valve and enters the downstream end of the fluid flow path.

[0039] In yet another embodiment, the fluid flow restricting member may comprise a gas pump or siphon in fluid communication with the fluid flow path.

[0040] In some embodiments, fluid can flow within the fluid flow path while the fluid flow restricting member seals the fluid flow path (e.g., when a plug is inserted into the fluid flow path or a valve disposed across the fluid flow path is closed). In such embodiments, the fluid flow restricting member can be positioned downstream of the fluid check valve and can define a downstream cavity within the fluid flow path between the fluid check valve and the fluid flow restricting member. The downstream cavity can have a volume configured to allow gas to flow from the upstream end of the fluid flow path through the fluid check valve and into the downstream cavity. The volume of the cavity can be selected to be greater than the total volume of gas expelled from the syringe, for example. Gas (or other fluid) can be restricted from flowing past the fluid flow restricting member in either the upstream or downstream direction.

[0041] In some embodiments, the fluid flow restricting member can comprise a closed downstream end of the fluid flow passage. The fluid flow restricting member can be integral with the plunger body. For example, the plunger body can comprise an opening at the upstream end of the fluid flow passage and a blind end at the downstream end of the fluid flow passage. Alternatively, the fluid flow restricting member can comprise a plug or other seal secured across the fluid flow passage.

[0042] In some embodiments, the fluid conduit may be included in a syringe. The syringe may include a syringe barrel defining the fluid conduit and adapted to partially receive a piston. When received within the syringe barrel, the piston may divide the syringe barrel into an upstream section and a downstream section. The syringe barrel may define a fluid opening adjacent the upstream section for fluid inflow and outflow. In such embodiments, the piston may be movable within the syringe barrel to draw fluid into and expel fluid from the syringe. In other embodiments, the fluid conduit may be a pipe, tube, or other passageway for fluid flow.

[0043] According to another aspect of the present disclosure, there is provided a vented syringe including a vented piston according to an embodiment of the present disclosure.

[0044] According to another aspect of the present disclosure, there is provided a method of filling and purging gas from a vented syringe according to an embodiment of the present disclosure, the method comprising: Immersing the fluid opening in a liquid; displacing the piston downstream to draw liquid into the upstream section of the vent syringe; displacing the piston in an upstream direction to cause gas to flow downstream through the fluid flow path.

[0045] The gas may flow downstream through the fluid flow path and out of the syringe (i.e., purging the gas from the syringe through the downstream section). In other embodiments, the gas may be trapped in a downstream cavity in the piston and / or in the downstream section of the syringe.

[0046] The method may include further displacing the piston in an upstream direction to contact the fluid check valve with the liquid. Once the check valve is wetted by the liquid, the check valve is "activated" and inhibits the passage of gas from the downstream end to the upstream end of the fluid flow path and inhibits the passage of liquid from the upstream end to the downstream end of the fluid flow path.

[0047] In some embodiments, the vented syringe can be filled from a vial. In some embodiments, the method can include pressurizing the vial. For example, the method can further include displacing the piston upstream to force gas in the upstream section out of the fluid opening before displacing the piston downstream to draw liquid into the upstream section of the syringe barrel.

[0048] In some embodiments, the method may further include displacing the piston downstream to allow gas to flow from the downstream section into the upstream section before immersing the fluid opening in the liquid source.

[0049] The method may further include, after purging the gas, moving the piston downstream to draw additional liquid into the upstream section of the syringe barrel.

[0050] The method may further include drawing a fluid (e.g., a gas) into the upstream section of the syringe barrel before drawing the liquid into the upstream section of the syringe barrel.

[0051] In some embodiments, the method may further include configuring a fluid flow suppressing member to suppress fluid flow (e.g., gas flow) from the downstream end to the upstream end of the fluid flow path (i.e., in the upstream direction) before displacing the piston in the downstream direction to draw liquid into the upstream section of the syringe barrel.

[0052] In some embodiments, the method may further include configuring a fluid flow inhibiting member to allow fluid flow (e.g., gas flow) from the upstream end to the downstream end of the fluid flow path (i.e., in the downstream direction) before displacing the piston in the upstream direction to cause gas to flow downstream through the fluid flow path.

[0053] Configuring the fluid flow restricting member to restrict fluid flow may include configuring the fluid flow restricting member to form a fluid seal across the fluid flow path. Configuring the fluid flow restricting member to allow fluid flow may include configuring the fluid flow restricting member to break the fluid seal across the fluid flow path. In some embodiments, if the fluid flow restricting member comprises a plug, configuring the fluid flow restricting member to restrict flow in the upstream direction may include inserting the plug to seal the fluid flow path. In some such embodiments, configuring the fluid flow restricting member to allow flow in the upstream direction may include removing, loosening, or otherwise adjusting the plug to break the fluid seal and open the fluid flow path. In other embodiments, configuring the fluid flow restricting member to restrict / allow fluid flow may include actuating a valve of the fluid flow restricting member to open or close the valve, respectively. Actuating the valve may include manual and / or automatic actuation. Other actuation methods may include, but are not limited to, electronic, pneumatic, and / or hydraulic actuation.

[0054] According to another aspect, there is provided a vent piston receivable within a fluid conduit, the piston comprising: a plunger body defining a fluid flow passage extending between an upstream end and a downstream end; a fluid check valve disposed across the fluid flow path, the fluid check valve being configurable to inhibit the passage of gas from the downstream end to the upstream end of the fluid flow path and to inhibit the passage of liquid from the upstream end to the downstream end of the fluid flow path; A vent piston is provided that includes a fluid flow control member disposed across the fluid flow path and configurable to selectively restrict fluid flow within the fluid flow path.

[0055] According to another aspect, there is provided a method of filling a vented syringe according to the present disclosure, the method comprising: connecting the fluid opening to a liquid source; causing liquid to flow into the upstream section of the syringe barrel such that gas in the upstream section of the syringe barrel flows downstream through the fluid flow path.

[0056] The liquid may be forced into the upstream section of the syringe barrel under pressure, for example, from an external pressure source (such as a pump). In some embodiments, the external pressure source provides the autofill pressure.

[0057] The position of the piston within the syringe barrel can be selected to define a fill volume, i.e., the position of the piston can be selected to define the volume of the upstream section of the syringe barrel, and the position of the piston relative to the barrel can be temporarily fixed during filling of the syringe.

[0058] The method may further include, after filling the vented syringe, moving the piston upstream to dispense liquid from the vented syringe through the fluid opening.

[0059] In some embodiments, the fluid conduit may be included in a fluid system, for example, a self-sealing vented fluid system.

[0060] According to another aspect of the present disclosure, a fluid conduit having an interior surface; A fluid system is provided that includes a vented piston according to an embodiment of the present disclosure, the piston being at least partially received within a fluid conduit and forming a fluid seal with an interior surface of the fluid conduit to separate the fluid conduit into an upstream section for containing gas and liquid and a downstream section for receiving gas.

[0061] The fluid system may further include one or more control systems. For example, the fluid system may include a motion control system, such as an automated motion control system, configured to engage with the piston to control movement of the piston. The automated motion control system may be configured to execute a protocol that actuates the piston to move the piston downstream to draw fluid into the fluid conduit, actuates the piston upstream to expel gas from the upstream section of the fluid conduit, actuates the piston downstream to draw additional fluid into the upstream section to obtain a desired fluid volume, and actuates the piston upstream to dispense a controlled volume of fluid. Additionally or alternatively, the fluid system may include a flow control system, such as an automated flow control system, for controlling a fluid flow restricting member. The flow control system may configure the fluid flow restricting member to restrict fluid flow within the fluid flow path or allow fluid flow within the fluid flow path. For example, the fluid system may include a controller for actuating a gate or valve to open or close the gate or valve. The flow control system and the motion control system may form part of a single control system. For example, the fluid system may include a control system configurable as a motion control system and / or a flow control system. Alternatively, the motion control system and the flow control system may be separate control systems. In some embodiments, the fluid system may form part of an automated fluid dispensing device.

[0062] Throughout this specification the word "comprise" or variations such as "comprises" or "comprising" will be understood to mean the inclusion of the stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. [Brief explanation of the drawings]

[0063] Embodiments are described in more detail below, by way of example, with reference to the accompanying drawings, in which:

[0064] [Figure 1A] FIG. 1 is a schematic diagram of a vent piston according to one embodiment of the present disclosure. [Figure 1B] FIG. 1B is an exploded schematic view of the vent piston of FIG. 1A. [Figure 2A] FIG. 10 is a schematic diagram of a vent piston according to another embodiment of the present disclosure. [Figure 2B] FIG. 2C is an exploded schematic view of the vent piston of FIG. 2B. [Figure 3A] 1 shows a series of steps for drawing liquid from a vial using a prior art syringe. [Figure 3B] 2B illustrates a series of steps for drawing up a liquid using a vented syringe according to an embodiment of the present disclosure including the piston of FIG. 2A. [Figure 4A] 1 shows a sequence of steps for automatic filling of a prior art syringe. [Figure 4B] 2B illustrates a sequence of steps for automatic filling of a vented syringe according to an embodiment of the present disclosure including the piston of FIG. 2A. [Figure 5] 10 is a graph illustrating test results of bubble purging at various angles of operation using a vented syringe including a piston according to an embodiment of the present disclosure. [Figure 6] 2B illustrates a series of steps for drawing up liquid from a sealed vial using a vented syringe according to an embodiment of the present disclosure that includes the piston of FIG. 2A. DETAILED DESCRIPTION OF THE INVENTION

[0065] 1A and 1B, an embodiment of a vent piston 100 according to the present disclosure is shown.

[0066] The vented piston 100 includes a plunger body 200, a fluid check valve 300, and a fluid flow restricting member 400. The plunger body 200 defines a fluid flow passage 210 extending between an upstream end 211 and a downstream end 212. The downstream end 212 may be open to the atmosphere. As such, the fluid flow passage 210 allows for venting of gas from the piston 100. "Venting" in this context may be understood to mean allowing leakage of gas from within the fluid conduit and / or the piston 100. The fluid check valve 300 is disposed across the fluid flow passage 210. The fluid check valve 300 may be configured to restrict the passage of gas from the downstream end 212 to the upstream end 211 of the fluid flow passage 210 and to restrict the passage of liquid from the upstream end 211 to the downstream end 212 of the fluid flow passage 210. The fluid flow restricting member 400 is also configured to be disposed across the fluid flow passage 210 to selectively restrict fluid flow within the fluid flow passage 210.

[0067] 1A and 1B, fluid flow restricting member 400 is positioned within plunger body 200 in fluid flow path 210, downstream of fluid check valve 300. In other embodiments, fluid flow restricting member 400 may be positioned elsewhere in fluid communication with fluid flow path 210.

[0068] In the illustrated embodiment, the fluid flow restricting member 400 comprises a valve 400. The valve 400 promotes asymmetric flow within the fluid flow path 210. That is, the valve 400 allows fluid flow from the upstream end 211 to the downstream end 212 of the fluid flow path 210 and restricts fluid flow from the downstream end 212 to the upstream end 211 of the fluid flow path 210. In some embodiments, the restriction may prevent fluid flow from the downstream end 212 to the upstream end 211 of the fluid flow path 210. In other embodiments, the restriction may partially prevent fluid flow from the downstream end 212 to the upstream end 211 of the fluid flow path 210, for example, such that gas flow in the upstream direction experiences greater resistance than flow in the downstream direction. The greater resistance to flow in the upstream direction may provide more efficient evacuation of gas from the upstream section of the fluid conduit.

[0069] The valve 400 is positioned across the fluid flow path 210 such that fluid flowing through the fluid flow path must flow through the valve 400. Thus, when the valve 400 is open, fluid can flow along the fluid flow path 210. Conversely, when the valve 400 is closed, fluid is inhibited from flowing along the fluid flow path 210. In the illustrated embodiment, the valve 400 is a passive valve. That is, the open or closed position of the valve 400 is responsive to the direction of fluid flow. The valve 400 is resiliently biased toward a closed position, inhibiting fluid flow, and remains closed against upstream fluid backpressure. However, downstream fluid pressure opens the valve 400, allowing fluid to flow from the upstream end to the downstream end.

[0070] The fluid flow restricting member 400 may comprise one or more of a diaphragm valve (e.g., a duckbill or slit valve), a swing check valve, a lift check valve, a piston check valve, a ball check valve, a switchable check valve, a spring valve, or other passive valve. In other embodiments, the fluid flow restricting member may include an actuatable valve, such as an adjustable or switching valve (e.g., a screw valve, a butterfly valve, a needle valve, a gate valve).

[0071] In other embodiments, other suitable fluid flow control mechanisms may be used. For example, in some embodiments, the fluid flow restricting member 400 may comprise a releasable seal. In some embodiments, the fluid flow restricting member 400 may comprise a plug configured to seal the fluid flow passage 210. The plug may be at least partially receivable within the plunger body 200. For example, the plug may be receivable at the downstream end of the fluid flow passage 210 to seal the fluid flow passage 210, i.e., to restrict fluid flow along the fluid flow passage 210. The plug may be removable from the fluid flow passage 210, releasable, or otherwise adjustable to allow fluid to flow along the fluid flow passage 210. The plug may include, for example, a rubber stopper. In other embodiments, the fluid flow restricting member 400 may comprise a pierceable, frangible, or otherwise releasable seal, solid or flexible cover, or film to allow fluid to flow along the fluid passage 210. In some embodiments, the piston 100 may be configured to allow a user to seal the downstream end 212 of the fluid flow passage 210. For example, the fluid flow restricting member 400 may be provided with the piston 100, or may be applicable to the piston 100 and / or removable from the piston 100 by a user. It is recognized that in some cases, fluid flow restriction may be achievable in the absence of the fluid flow restricting member 400 by placing the user's thumb across the fluid flow path 210. However, providing the fluid flow restricting member 400 on the piston 100 may advantageously improve the ease of use and / or performance of the piston 100. For example, providing the fluid flow restricting member 400 on the piston 100 may reduce the number of steps performed by a user during operation of the piston 100. Furthermore, providing the fluid flow restricting member 400 on the piston 100 may increase the consistency and / or predictability of the performance of the piston 100, for example, by reducing variability due to user technique. The provision of the fluid flow restricting member 400 may allow for a longer storage time of a medicament in a syringe including the piston 100.Fluid flow restricting member 400 may provide a visual indicator of the status of piston 100 and / or a syringe including piston 100. For example, if fluid flow restricting member 400 includes a plug, a user may be able to determine whether a syringe including piston 100 has been used based on whether the plug has been removed. In yet another embodiment, fluid flow restricting member 400 may be applicable to piston 100 and / or may be detachable from piston 100 by an electronic actuator (e.g., robotically controlled).

[0072] In other embodiments, the fluid flow restricting member 400 may comprise a deformable portion at the downstream end of the plunger body 200. The deformable portion may include, for example, a flexible wall. The flexible wall may be integral with and / or formed integrally with a sidewall of the plunger body 200. The flexible wall may be movable between an open position and a closed position, in which the flexible wall at least partially blocks the fluid flow path 210, thereby restricting fluid flow. The flexible wall may be resiliently biased toward the open position. The flexible wall may be resiliently deformable to the closed position under the application of compressive pressure (e.g., applied by a user's finger).

[0073] In another embodiment, the fluid flow restriction member 400 may comprise an expandable balloon. The fluid flow restriction member 400 may further comprise a mesh that restricts movement of the balloon in the upstream direction but allows the balloon to expand freely. In this manner, the balloon may trap gas that passes through the fluid check valve 300 and enters the downstream end of the fluid flow path 210.

[0074] In yet another embodiment, the fluid flow restricting member 400 may comprise a gas pump or siphon in fluid communication with the fluid flow path 210 .

[0075] In other embodiments, the fluid flow restricting member 400 may be configured to partially restrict fluid flow within the fluid flow path 210. For example, the fluid flow restricting member 400 may not seal the fluid flow path 210, but may provide increased resistance to fluid flow within the fluid flow path 210.

[0076] In other embodiments, the piston 100 may be configured such that fluid can still flow within the fluid flow passage 210 while the fluid flow restricting member 400 seals the fluid flow passage 210. For example, fluid may be allowed to flow within the fluid flow passage 210 when the valve 400 is in a closed configuration, or alternatively, when a plug or other sealing mechanism seals the fluid flow passage 210. In some embodiments, the fluid flow restricting member 400 may provide a substantially permanent fluid seal across the fluid flow passage 210. For example, the fluid flow restricting member 400 may comprise a non-releasable seal or plug secured across the fluid flow passage 210.

[0077] In such an embodiment, the fluid flow restricting member 400 may be positioned downstream of and spaced apart from the fluid check valve 300. A downstream cavity within the fluid flow path 210 may be defined between the fluid check valve 300 and the fluid flow restricting member 400. If the downstream cavity has sufficient volume, gas may flow downstream into the downstream cavity even when the fluid flow path 210 is sealed by the fluid flow restricting member 400.

[0078] In such embodiments, fluid flow restricting member 400 may partially prevent fluid flow within fluid flow channel 210, for example, such that the fluid flow experiences greater resistance than if fluid flow restricting member 400 were not present. This partial restriction of fluid flow may be configured to be sufficient to allow the creation of negative or positive pressure upon displacement of plunger 100 within the fluid conduit, thereby allowing fluid to be displaced within the fluid conduit by piston 100 (e.g., allowing fluid to be drawn into or expelled from the syringe barrel).

[0079] The degree to which fluid flow within the fluid flow passage is restricted by the fluid flow restricting member 400 can be affected by a number of factors, including, but not limited to, the volume of the downstream cavity.

[0080] For example, in the embodiment of FIG. 1A, valve 400 closely abuts fluid check valve 300. Nevertheless, downstream cavity 215 is defined by the volume enclosed between valve 400 and fluid check valve 300. In the embodiment illustrated in FIG. 2A, valve 400′ is positioned further downstream from check valve 300 and defines downstream cavity 215′ within the lumen of hollow plunger shaft 250′. The larger volume of cavity 215′ compared to the volume of cavity 215 reduces the restriction of gas flow in the downstream direction. Thus, in the embodiment of FIG. 2A, valve 400 can be permanently closed (or replaced by a fixed plug or other sealing mechanism) while still allowing gas to pass through fluid check valve 300 and into downstream cavity 215′.

[0081] In some embodiments, the fluid flow restricting member 400 may be axially fixed relative to one or more of the piston 100, the stopper 500, and / or the check valve 300. In other embodiments, the fluid flow restricting member 400 may be axially movable relative to the piston 100, the stopper 500, and / or the check valve 300. For example, if the fluid flow restricting member 400 includes a seal or stopper, the fluid flow restricting member 400 may be movable relative to the piston 100, the stopper 500, and the check valve 300 to insert and / or remove the seal or stopper from the piston.

[0082] In some embodiments, the fluid flow restricting member 400 may be movable within the fluid flow path 210. For example, the fluid flow restricting member 400 may be axially slidable along a portion of the fluid flow path 210 between an upstream position and a downstream position. In some embodiments, the movement of the fluid flow restricting member 400 may be passive, i.e., the fluid flow restricting member 400 may move along the fluid flow path in response to forces imparted by fluid flowing through the fluid flow path 210. In other embodiments, the movement of the fluid flow restricting member 400 may be actuated (or actuable) such that a user may control and / or adjust the movement of the fluid flow restricting member 400.

[0083] In one embodiment, the fluid flow restricting member 400 may be movable in a portion of the fluid flow conduit 210 downstream of the fluid check valve 300 between an upstream position adjacent the fluid check valve 300 and a downstream position further away from the fluid check valve 300. A cavity may be defined between the fluid check valve 300 and the fluid flow restricting member 400, with the volume of the cavity being variable depending on the position of the fluid flow restricting member 400 within the fluid flow path 210. As the piston 100 moves upstream through the fluid conduit, the fluid flow restricting member 400 may be moved toward (or held at) the upstream position adjacent the fluid check valve 300. This positioning of the fluid flow restricting member 400 may minimize the volume of the cavity and the amount of fluid present in the cavity downstream of the fluid check valve, enhancing vacuum generation. As the piston 100 moves downstream, the fluid may exert a force on the fluid flow restricting member 400 to move the fluid flow restricting member 400 downstream toward the downstream position. This may increase the volume of the cavity downstream of the fluid check valve.

[0084] Movement of the fluid flow restricting member 400 within the fluid flow passage 210 as described above may enhance or provide additional flow asymmetry, however, such embodiments may be more complex and / or more expensive to manufacture.

[0085] The fluid check valve 300 includes a hydrophilic porous material 310 and a hydrophobic porous material 320 disposed adjacent to the hydrophilic porous material 310. Examples of such fluid check valves are described in the applicant's previously filed PCT application PCT / AU2020 / 050902. A fluid check valve according to the present disclosure may incorporate one or more features of the fluid check valves described in PCT / AU2020 / 050902. In particular, the hydrophilic porous material 310 and / or the hydrophobic porous material 320 may incorporate one or more features of the hydrophobic and hydrophilic porous materials described in PCT / AU2020 / 050902.

[0086] 1B, the hydrophilic porous material 310 is disposed upstream of the hydrophobic porous material 320. One side of the hydrophilic porous material 310 is in fluid communication with the upstream end 211 of the fluid flow path 210, and one side of the hydrophobic porous material 320 is in fluid communication with the downstream end 212 of the fluid flow path 210.

[0087] The fluidic check valve 300 initially allows the passage of gas in both the upstream and downstream directions. However, when wetted, the fluidic check valve 300 inhibits the passage of gas from the downstream end 212 to the upstream end 211 and inhibits the passage of liquid from the upstream end 211 to the downstream end 212. That is, the hydrophilic porous material 310 is configured to retain liquid from the upstream end 211 to inhibit the passage of gas from the downstream end 212 to the upstream end 211, and the hydrophobic porous material 320 is configured to inhibit the passage of liquid from the upstream end 211 to the downstream end 212.

[0088] 1A and 1B, the fluid check valve 300 is retained within the plunger body 200 at the upstream end of the fluid flow path 210. In other embodiments, the fluid check valve 300 may be positioned elsewhere in fluid connection with the fluid flow path 210. The plunger body 200 includes a retention body 700 for retaining the fluid check valve 300. The plunger further includes a hollow plunger shaft 250. The retention body 700 in this embodiment is integral with the plunger shaft 250. However, in other embodiments (such as those shown in FIGS. 2A and 2B), the retention body 700 and the plunger shaft 250 may be separate components, with the retention body 700 configured to be coupled to the plunger shaft 250 for movement in conjunction with the plunger shaft 250. The fluid flow path 210 extends through the retention body 700 and the plunger shaft 250.

[0089] The hydrophilic porous material 310 and the hydrophobic porous material 320 may be retained within the plunger body 200 by applying pressure, pinching, imprinting and deformation of the material, fusion, ultrasonic welding, heat welding, laser welding, overmolding, etc. Alternatively, the hydrophilic porous material 310 and the hydrophobic porous material 320 may be formed (e.g., injection molded, etched, patterned, or laser formed) directly into the plunger body 200. The seal between the hydrophilic porous material 310 and the plunger body 200 must be able to withstand pressure up to at least the leak pressure.

[0090] When piston 100 is fitted within a fluid conduit (e.g., a syringe barrel, etc.), piston 100 seals with the interior surface of the fluid conduit in a fluid-tight manner. That is, the seal formed between piston 100 and the interior surface prevents fluid from passing through the fluid conduit except through fluid flow path 210 and fluid check valve 300. In this manner, the fluid seal between piston 100 and the interior surface of the fluid conduit separates the fluid conduit into an upstream section and a downstream section.

[0091] 1A , the piston 100 may further include a sealing member, such as a stopper 500. In this embodiment, the stopper 500 is positioned at the upstream end of the plunger body 200 and is configured to engage the inner surface of the fluid conduit to form a seal between the piston 100 and the fluid conduit. The stopper 500 forms a seal against the inner surface of the fluid conduit. In this embodiment, the plunger body 200 includes a connection flange 260 for connecting to the stopper 500. However, in other embodiments, the stopper and plunger body may be connected by other suitable connection mechanisms. The stopper 500 includes an axial channel (not shown) that provides fluid communication with the fluid flow path 210 and the upstream section of the fluid conduit.

[0092] In other embodiments, the piston 100 may include one or more O-rings or other similar sealing components. Such sealing components may be positioned at the distal end of the piston or elsewhere along the piston. Alternatively, one or more components of the piston (e.g., the plunger, check valve, or fluid flow restricting member) may be configured (e.g., sized and / or shaped) to be closely fitting and receivable within a fluid conduit to engage the interior surface of the fluid conduit and seal the fluid conduit (create a fluid seal) without the need for an additional sealing member.

[0093] The plunger 100 can be configured to be displaced along the fluid conduit while maintaining a seal with the fluid conduit. In this manner, the plunger can be actuated to drive liquid within an upstream section of the fluid conduit to move along the fluid conduit. The stopper 500 can be substantially rigidly connected to the plunger body 200 such that displacement of the piston 100 affects a corresponding equal displacement of the stopper 500 within the fluid conduit. In the illustrated embodiment, the piston 100 includes a handle 600 that assists in applying a force to the piston 100 to displace the piston 100 within the fluid conduit.

[0094] In this embodiment, the piston 100, stopper 500, fluid flow restricting member 400, and check valve 300 are configured for assembly together such that they are axially fixed and do not move relative to one another. That is, the piston 100, stopper 500, fluid flow restricting member 400, and check valve 300 are configured for coupled displacement within the fluid conduit. As the piston 100 is driven in an upstream direction B through the fluid conduit, the fluid flow restricting member 400 allows liquid and gas to flow through the fluid flow path 210. The fluid check valve 300 allows any gas in the upstream section of the fluid conduit to pass through the fluid check valve 300 and flow through the fluid flow path 210. As the piston 100 is displaced in a downstream direction A through the fluid conduit, the fluid flow restricting member 400 restricts fluid flow through the fluid flow path 210. Thus, displacement of the piston 100 in the downstream direction A creates a negative pressure relative to atmospheric pressure in the upstream section 921 of the fluid conduit due to the sealing of the stopper 500 to the fluid conduit and the closed position of the fluid flow restricting member 400.

[0095] Once liquid contacts the fluidic check valve 300, the liquid may enter the hydrophilic porous material 310 and be retained by the hydrophilic porous material 310. The hydrophilic porous material 310 with the retained liquid inhibits and / or prevents the passage of gas through the hydrophilic porous material 310. The hydrophilic porous material 310 may have a strong capillary pressure, for example, to help retain high surface tension liquids. In this way, gas is prevented from flowing back to the upstream end of the fluid flow path 210. Liquid is inhibited from passing through the hydrophobic porous material 320. The hydrophobic porous material 320 may have a strong repulsive pressure that inhibits high surface tension liquids from entering its structure. In this way, as the piston 100 is driven downstream, gas is purged from the upstream section of the fluid conduit. Once the fluidic check valve is wetted by liquid from the upstream section, the fluidic check valve is "locked" and does not allow the passage of liquid or gas through the fluidic check valve.

[0096] A vent piston 100' according to another embodiment of the present disclosure is shown in Figures 2A and 2B. In this embodiment, the plunger body 200' comprises a retention body 700' and a hollow plunger shaft 250'. A fluid check valve 300' is retained within the retention body 700'. The retention body 700' defines a fluid opening 710' having an upstream side 711' and a downstream side 712'. The fluid flow path 210' extends through the retention body 700' and through the opening 710'. Hydrophilic and hydrophobic porous materials 310', 320' are disposed to cover the fluid opening 710'.

[0097] The retention body 700' further comprises a coupling member 740' for connecting the retention body 700' to the distal end of the hollow plunger shaft 250'. In the illustrated embodiment, the hollow plunger shaft 250' is hollow, and the fluid flow path 210' extends through a central lumen of the hollow plunger shaft 250'. The coupling member 720' may be a luer connector or other such connector (e.g., threads, press-fit, barbed tip, snap-fit ​​or clip connection, flange, collar, revolute joint, ball joint, universal joint, cotter pin, knuckle joint, or irreversible connection such as friction welding or adhesive) that allows fluid communication along the fluid flow path 210' between the retention body 700' and the hollow plunger shaft 250'. However, in other embodiments, the plunger shaft may be solid. In such embodiments, the fluid flow path 210' may terminate, for example, at a downstream portion of the retention body 700'.

[0098] As shown in FIG. 2B , the retention body includes a first portion 730′ and a second portion 740′ connectable to one another to cooperatively hold the hydrophilic porous material 310′ and the hydrophobic porous material 320′ therebetween. The first portion 730′ includes a recess 731′ configured to receive the hydrophilic porous material 310′ and the hydrophobic porous material 320′, and the second portion 740′ includes a protrusion 741′ configured to be receivable within the recess 731′ and to hold the hydrophilic porous material 310′ and the hydrophobic porous material 320′ therein. The reverse configuration (i.e., a recess in the second portion 740′ and a protrusion in the first portion 730′) is also contemplated. In the illustrated embodiment, the retention body 700′ further includes a connection flange 260′ for connecting to the stopper 500′. However, the stopper may alternatively be connected to the retention body 700′ by other suitable connection means.

[0099] In some embodiments, a friction fit is formed between the first portion 730' and the second portion 740'. The shape of the recess 731' and the first and second portions 730', 740' may assist in forming the friction fit. Additionally or alternatively, the first portion 730' or the second portion 740' may be bonded together by any one of chemical bonding, heat sealing, and adhesive. The first portion 730' or the second portion 740' may be removably or fixably attached to one another.

[0100] In some embodiments, the hydrophilic porous material 310′ and the hydrophobic porous material 320′ may be retained by the retaining body by applying pressure, pinching, imprinting and deforming the material, fusing, ultrasonic welding, heat welding, laser welding, overmolding, etc. Alternatively, the hydrophilic porous material 310′ and the hydrophobic porous material 320′ may be formed (e.g., injection molded, etched, patterned, or laser formed) directly into one or more of the first portion 730′ or the second portion 740′.

[0101] 2A and 2B, plunger body 200′ further comprises housing 270 in which fluid flow restrictor valve 400′ is located. Housing 270 includes a pair of connectors 271 a, 271 b for connecting to hollow plunger shaft 250′ and handle 600′. Connectors 271 a, 271 b may be luer connectors or the like that allow fluid flow therethrough such that fluid flow path 210 extends through housing 270′ and handle 600′.

[0102] The embodiment of Figures 1A and 1B requires significantly fewer component parts than the embodiment of Figures 2A and 2B, and therefore may be easier and / or cheaper to manufacture.

[0103] Syringe In some embodiments, the vent piston 100, 100' may be included in a vent syringe 900. Vented syringes according to embodiments of the present disclosure may be useful in controlled dosing applications (controlled dosing applications are those in which the properties or amount of fluid are defined by the syringe device). Vented syringes according to embodiments of the present disclosure may be used in a variety of applications, including, but not limited to, pharmaceutical syringes and microfluidic devices.

[0104] One example of such a vented syringe 900 is shown in Figures 3B and 4B. The vented syringe 900 incorporates the vented piston 100, but may alternatively include the vented piston 100' or other embodiments of the vented piston described herein.

[0105] Vented syringe 900 includes a barrel 910 defining a fluid conduit 920 having an upstream section 921 and a downstream section 922. A fluid opening is provided in upstream section 921 to allow fluid to enter and exit the vented syringe. Piston 100 is partially received within vented syringe barrel 910 such that stopper 500 forms a fluid seal with the interior surface of barrel 910. Handle 600 facilitates displacement of the piston along vented syringe barrel 910. Piston 100 can be displaced along barrel 910 while maintaining the seal between stopper 500 and the interior surface of barrel 910.

[0106] In this embodiment, piston 100, stopper 500, fluid flow restricting member 400, and check valve 300 are configured to be axially fixed to one another for coupled displacement within barrel 910 of syringe 900. Due to the seal between piston 100 (via stopper 500) and the interior surface of barrel 910, and the coupled movement of piston 100, stopper 500, fluid check valve 300, and valve 400, displacement of piston 100 can result in fluid being drawn into or expelled from fluid opening 923. That is, as piston 100 is displaced in downstream direction A through syringe barrel 910, fluid flow restricting member 400 restricts fluid flow through fluid flow path 210. In this manner, displacement of piston 100 in downstream direction A creates a negative pressure in upstream section 921 of syringe barrel 910 relative to atmospheric pressure due to the sealing of stopper 500 against the interior surface of barrel 910. This negative pressure can be used to draw liquid into the upstream section 921 of the barrel 910. When the check valve 300 is unlocked and the piston 100 is driven in the upstream direction B through the barrel 910, the valve 400 allows gas to flow through the fluid flow path 210. The fluid check valve 300 allows any gas in the upstream section of the fluid conduit 920 to pass through the fluid check valve 300 and flow through the fluid flow path 210. Liquid is allowed to flow through the fluid flow path upstream of the location of the check valve 300, but is inhibited from flowing beyond the location of the check valve 300. Once the liquid contacts the check valve 300, causing it to wet and lock, the piston 100 can be further displaced in the upstream direction B to expel the fluid from the fluid opening 923.

[0107] The steps for drawing up medication from a vial and injecting the medication using a conventional syringe are illustrated in FIG. 3A. In FIG. 3A-1, a volume of air is drawn into the syringe. In FIG. 3A-2, the vial is pierced with the syringe tip, and the vial is pressurized with air. The vial and syringe are then inverted, as shown in FIG. 3A-3. Fluid from the vial is then drawn into the syringe barrel by withdrawing the plunger, as shown in FIG. 3A-4. The plunger is depressed to expel air bubbles and correct the dose, as shown in FIG. 3A-5. FIG. 3A-6 shows the syringe ready to proceed with the injection.

[0108] The four main routes of drug injection are intravenous, intrathecal, intramuscular, and subcutaneous. Injecting gas bubbles can be dangerous in some situations. Air injected directly into a vein can travel to the heart, lungs, or brain, where it can cause heart attack, respiratory failure, or stroke. Air injected into the spinal cord can cause severe headaches. In contrast, gas bubbles injected into intradermal and intramuscular tissues can be harmlessly absorbed (unless the user accidentally punctures a vein).

[0109] The needle's position can be checked by slightly aspirating the fluid from the injection site. If the aspirated fluid is red, the needle has penetrated the vein. If the aspirated fluid is clear or yellowish, the needle tip is subcutaneous or intramuscular. This practice is particularly important when working with potent agents, such as local anesthetics, which can cause cardiac complications in some patients if injected incompletely.

[0110] During medication administration, it is good practice, and often essential, to purge air from the syringe barrel after the medication is drawn, as shown in Figure 3A-5. During purging, a small amount of medication will be expelled from the syringe (if the user correctly draws up the required dose). However, some users may be less skilled and draw significantly more to ensure they can purge the syringe while still having the required dose.

[0111] Incorporating a vent into a syringe can avoid the need for a purge step, which wastes medication. However, including a gas vent in a syringe design can pose risks during normal syringe use. For example, if gas backs up into the syringe during use, there is a risk of injecting air into the patient. Furthermore, if the syringe needs to be aspirated before the injection step, gas can enter the syringe barrel. A vented syringe according to an embodiment of the present disclosure includes a fluid check valve that prevents gas from re-entering the upstream section of the syringe barrel once the fluid check valve is wetted.

[0112] Furthermore, ease of loading a syringe is an important part of making a syringe easy to use. For routine and common applications, a conventional syringe is loaded by a user by immersing the syringe head in a liquid and then manually withdrawing the piston / plunger until the liquid properly fills the barrel. A vented syringe according to embodiments of the present disclosure incorporates a fluid flow restricting member for selectively restricting flow within a fluid flow path to create flow asymmetry. That is, the fluid flow restricting member 400 may restrict flow in one direction along the fluid flow path while allowing flow in the other direction. This allows the syringe to be easily loaded by simple withdrawal of the piston.

[0113] 3B illustrates a method for filling a vented syringe 900 according to an embodiment of the present disclosure. The method illustrated in FIG. 3B may be suitable for filling a syringe from a reservoir of fluid, such as, for example, an unsealed vial.

[0114] 3B-1, gas (e.g., air) 10 is drawn into vented syringe barrel 910 by displacing piston 100 in downstream direction A. During this displacement, fluid flow restricting member 400 remains substantially closed. Thus, displacement of piston 100 creates a negative pressure in upstream section 921 of vented syringe barrel 910, drawing fluid into upstream section 921 through fluid opening 923.

[0115] In FIG. 3B-2, the vented syringe 900 is partially inserted into a source of liquid 20 (e.g., a vial of medication) such that the fluid opening 923 is submerged in the liquid 20. The piston 100 is further displaced in the downstream direction A, as shown by the arrow in FIG. 3B-2, to draw the liquid 20 into the upstream section 921 of the vented syringe 900. In some cases, a gush of liquid 20 may occur as the liquid 20 enters the upstream section 921 of the vented syringe 900. If the gush of liquid 20 contacts the fluid check valve 300, the fluid check valve 300 may lock. To ameliorate the risk of premature locking of the fluid check valve 300, the piston 100 may be moved away from the fluid opening 923 in step 3B-1 a sufficient distance to prevent the gush of fluid 20 from contacting the fluid check valve before drawing the fluid 20 into the upstream section 921.

[0116] 3B-3, piston 100 is then pushed down in upstream direction B. As piston 100 moves along vented syringe barrel 910, positive pressure opens valve 400, allowing gas 10 to flow through fluid check valve 300 and along fluid flow path 210. Gas 10 is vented from syringe 900 through open downstream end 212 of hollow plunger rod of piston 100. This step may substantially eliminate any bubbles of gas 10 from upstream section 921.

[0117] Once the piston reaches the liquid 20, the liquid 20 flows through the fluid flow path 210 until it contacts the fluid check valve 300, wetting the hydrophilic membrane 310. Once the fluid check valve membranes 310, 320 are wet, the fluid check valve may be considered "locked." That is, the fluid check valve inhibits or prevents the liquid 20 from flowing in the downstream direction past the fluid check valve 300 and inhibits or prevents the gas 10 from flowing in the upstream direction B past the fluid check valve. Thus, further displacement of the piston 100 in the upstream direction B forces the liquid 20 out of the fluid opening 923.

[0118] Additional liquid 20 can then be aspirated into the vented syringe 900 by moving the piston 100 in the downstream direction A until a desired amount of liquid 20 enters the upstream section 921, as shown in FIG. 3B-4. Liquid 20 can be dispensed from the vented syringe as needed by depressing the piston 100 to force the liquid 20 out of the fluid opening, as shown in FIG. 3B-5.

[0119] In some embodiments, the vented syringe 900 can be filled from a sealed vial. In some embodiments, the method can include pressurizing the vial. In such embodiments, the method can include displacing the piston 100 in an upstream direction B to force gas 10 in the upstream section 921 out of the fluid opening 923 and into the vial before displacing the piston 100 in a downstream direction A to draw liquid 20 into the upstream section 921 of the syringe barrel 910.

[0120] One exemplary method for filling a vented syringe 900 from a sealed vial is illustrated in FIG. 6. In FIG. 6-1, gas (e.g., air) 10 is drawn into the vented syringe barrel 910 by displacing the piston 100 in a downstream direction A. During this displacement, the fluid flow suppression member 400 remains substantially closed. In this manner, the displacement of the piston 100 creates a negative pressure in the upstream section 921 of the vented syringe barrel 910, drawing the gas into the upstream section 921 through the fluid opening 923. The volume of gas drawn into the upstream section 921 in this step can be configured with respect to the desired volume of liquid 20 to be extracted from the vial. For example, the volume of gas drawn into the upstream section 921 can be at least equal to or greater than the desired volume of liquid 20. Alternatively, the volume of gas drawn into the upstream section 921 can be less than the desired volume of liquid 20.

[0121] 6, syringe 900 may include (or be configured for attachment to) needle cannula 800. Needle cannula 800 may be attached or attachable to the upstream end of syringe 900. Needle cannula 800 may extend fluid flow path 920 to the upstream end 801 of needle cannula 800.

[0122] 6-2 illustrates a step of pressurizing a vial. In this step, needle cannula 800 is partially inserted into a sealed vial, for example, by piercing the seal of the vial so that upstream end 801 of the needle cannula is disposed within the vial and submerged in liquid 20 (e.g., a liquid medicament, etc.) contained in the vial. Piston 100 is then displaced in upstream direction B to force gas 10 in upstream section 921 out of fluid opening 923 and into the vial. It will be appreciated that the greater amount of gas drawn into upstream section 921 of syringe 900 in step 6-1 may result in a correspondingly higher pressure within the vial after pressurization step 6-2.

[0123] In some embodiments, during the vial pressurization step, some gas may also flow through fluid check valve 300 in downstream direction A. One or more components of vent syringe 900 may be configurable to restrict fluid flow in downstream direction A during the vial pressurization step. This may increase the proportion of gas that exits fluid opening 923 during the vial pressurization step. For example, in some embodiments, fluid flow restricting member 400 may be configurable to restrict fluid flow in downstream direction A before performing the vial pressurization step. In other embodiments, fluid flow restricting member 400 may allow fluid flow during the vial pressurization step.

[0124] In some embodiments, fluid flow through the fluid flow path 210 may be restricted by means other than the fluid flow restricting member 400. In some embodiments, the vented syringe 900 may include a secondary fluid flow restricting member. The secondary fluid flow restricting member may be configured or configurable to selectively restrict flow within the fluid flow path 210. For example, if the fluid flow restricting member 400 includes a passive valve, the secondary fluid flow restricting member may be capable of restricting fluid flow within the fluid flow path 210 under conditions under which the fluid flow restricting member 400 would permit fluid flow (e.g., during a vial pressurization step). The secondary fluid flow restricting member may be configured or configurable to seal the fluid flow path. For example, the secondary fluid flow restricting member may be configurable between an open configuration in which fluid flow is substantially unrestricted and a closed (or sealed) configuration in which fluid flow is restricted. The secondary fluid flow restricting member may be positioned or positionable downstream of the fluid flow restricting member 400.

[0125] The secondary fluid flow restricting member may include, for example, a releasable or breakable seal, a plug (such as a rubber stopper or other suitable plug), a flexible wall, a solid or flexible cover. The secondary fluid flow restricting member may be actuatable, for example, electronically actuatable. In other embodiments, the secondary fluid flow restricting member may be configured to be selectively applied and / or actuated by a user.

[0126] In some embodiments, piston 100 may be configured to allow a user to selectively seal downstream end 212 of fluid flow path 210. For example, in the illustrated embodiment, a user's thumb 40 may be positioned across downstream end 212 of fluid flow path 210 to seal fluid flow path 210, thus restricting fluid flow in downstream direction A during the vial pressurization step. User's thumb 40 in this case may be considered to represent a secondary fluid flow restricting member that is selectively applyable by the user.

[0127] In some applications, vial contamination may be a problem due to contaminants in the surrounding air or a lack of sterility. In some such applications, piston 100 may first be displaced in downstream direction A to cause gas 10 to flow through fluid check valve 300 from downstream section 922 to upstream section 921 so that the syringe is pre-primed with sterile air. That is, displacement of piston 100 may draw gas 10 through fluid check valve 300 and into upstream section 921 of vented syringe barrel 910. Fluid opening 923 may then be inserted into the vial, valve 400 may be closed, and plunger 100 may be displaced slightly in upstream direction B. This allows syringe 900 to pressurize the vial with clean air, reducing the possibility of vial contamination.

[0128] After pressurization of the vial, the venting syringe 900 may be configured to allow fluid flow in the downstream direction A. For example, the fluid flow restricting member 400 may be configured to allow fluid flow in the downstream direction A. Alternatively or additionally, the secondary fluid flow restricting member (if present) may be removed or otherwise configured to allow fluid flow in the downstream direction A. In the illustrated embodiment, as shown in FIG. 6-3, the user's thumb is removed from the downstream end 212 of the fluid flow path 210, allowing fluid to flow in the downstream direction A. Under the increased pressure (relative to ambient) introduced into the vial in the step of FIG. 6-2, liquid 20 from the vial may flow into the upstream section 921 of the venting syringe 900.

[0129] As liquid 20 flows into the upstream section 920 of the vent syringe, gas 10 flows from the upstream section 921 along the fluid flow path 210, through the fluid check valve 300, and is vented out the downstream end 212 of the hollow plunger shaft 250 of the piston 100. In some cases, if sufficient pressure is introduced into the vial, the liquid 20 may flow up to the level of the fluid check valve 300 and wet the hydrophilic membrane 310. The hydrophobic membrane 320 inhibits the liquid from passing through the fluid check valve 300. Further flow of liquid 20 into the upstream section 921 of the vent syringe 900 may push the stopper 500 along with the piston 100 in the downstream direction A, as shown, for example, in FIG. 6-4 .

[0130] In some cases, for example, if the fluid has not reached the level of the fluid check valve 300 under pressure from the vial, the piston 100 can be pushed down in the upstream direction B to further remove air bubbles from the upstream section 921 of the vent syringe 900.

[0131] If needed, additional liquid 20 can be aspirated into vent syringe 900 by moving piston 100 in downstream direction A until a desired amount of liquid 20 enters upstream section 921. Vent syringe 900 can then be moved to withdraw needle cannula 800 from the vial. Liquid 20 can be dispensed from the vent syringe as needed by depressing piston 100 to force liquid 20 out of end 801 of the needle cannula (e.g., to inject a liquid medication into a patient's body).

[0132] A vented syringe according to the present disclosure may reduce wastage when administering medication because it allows the user to expel air bubbles while sampling the medication from the vial, rather than after the medication has already been removed.

[0133] Additionally, vented syringes according to embodiments of the present invention can be filled and operated without tilting or inverting the vented syringe, which can minimize the formation of air bubbles and prevent needle stick injuries that can occur when drawing fluid from an inverted vial.

[0134] Figure 5 demonstrates that air bubbles from the upstream section of the syringe barrel can be expelled at a wide variety of operating angles, which may allow the user to adopt a variety of positions when extracting medication and purging gas, enhancing the ergonomic suitability of the vented syringe.

[0135] Pre-filled Syringes Pre-filled syringes are an increasingly popular method for packaging medications. This can be attributed to several factors, including: Pre-filled syringes can be easy and convenient to use. Pre-filled syringes can limit overfilling, reducing medication wastage. Pre-filled syringes can be sold pre-labeled, which reduces wastage and the possibility of administrative errors.

[0136] Minimizing wastage is especially important in the manufacture of expensive pharmaceuticals, such as biologics. Biological drugs, such as monoclonal antibodies, are so expensive that packaging costs are negligible. Thus, even a small reduction in overfilling can result in significant cost savings.

[0137] Pre-filled syringes are typically manufactured by independent companies in a multi-step process: once the piston, piston seal, and syringe barrel are manufactured and sterilized, they are packaged in special tubs and bagged ready for "fill and finish."

[0138] "Fill and finish" is the process by which syringes are filled, assembled, tested, individually labeled, and packaged for shipment to suppliers. FIG. 4A shows a simplified method of the automated filling procedure for a conventional syringe. Generally, a syringe barrel, such as that shown in FIG. 4A-1, is unpackaged and loaded into an automated filling machine. The appropriate amount of medication liquid is then precisely dispensed into the syringe barrel through openings at either end of the syringe, as shown in FIG. 4A-2. A stopper is then loaded into the syringe barrel, as shown in FIG. 4A-3, followed by the piston shaft, as shown in FIG. 4A-4. The complete syringe assembly is then tested and packaged. The prefilled syringe can then be packaged and stored. When needed, medication can be dispensed from the syringe by depressing the plunger rod to drive the stopper along the barrel, forcing the medication out of the fluid opening at the distal end of the syringe, as shown in FIG. 4A-5.

[0139] Drugs can be sensitive to contaminants generated during packaging and syringe manufacturing. This is especially true for biologics such as monoclonal antibodies, which are often prone to aggregation. Protein aggregation alters protein binding kinetics, rendering the drug unsuitable for administration. As a result, a significant amount of testing is performed to ensure that drug packaging and storage does not result in aggregation of most biologics.

[0140] Syringe filling typically requires an inert, sterile surface and precise volumetric dosing. Biological drugs, such as monoclonal antibodies, are highly sensitive to mechanical stress and particle contamination. This is because monoclonal antibodies are typically injected subcutaneously and in high doses. This route of administration requires high concentrations in solution, which poses a significant risk of aggregation. Therefore, it is important that the filling procedure for such drugs avoids mechanical stress and particle contamination, as each of these promotes aggregation.

[0141] Diaphragm, peristaltic, and rotary piston pumps are commonly used to prefill syringes. However, the use of these pumps carries the risk of plastic or metal particle contamination due to mechanical degradation of process components. These issues can alternatively be addressed using pressure / time fillers, which avoid these mechanical stresses and contamination risks but require precise physical characteristics of fluid viscosity to accurately dose each syringe.

[0142] Medications, such as those intended for intravenous injection or those that are oxygen sensitive, cannot be packaged with an air bubble and are stoppered using a vacuum method, however, such methods run the risk of generating particulate contaminants that can damage the syringe barrel and shatter the medication.

[0143] Vented syringes according to embodiments of the present disclosure may ameliorate one or more of the drawbacks associated with conventional pre-filled syringe manufacturing processes. Vented syringes such as those described herein may enable filling techniques that avoid significant sources of contamination and eliminate the complexities associated with syringe stopper plugging. Vented syringes according to embodiments of the present disclosure may enable control of dosage using only the mechanical design and piston position of the vented syringe.

[0144] A method of filling a vented syringe according to an embodiment of the present disclosure is shown in FIG. 4B. In FIG. 4B-1, a vented syringe 900 including a vented piston 100 preloaded in a vented syringe barrel 910 can be unpackaged and loaded into an automated filling machine. Liquid 20 is then dispensed into the vented syringe through fluid opening 923, as shown in FIG. 4B-2. As liquid 20 flows through the vented syringe barrel 910, gas 10 in the upstream section 921 is expelled downstream through the vented piston 100. Once liquid 20 reaches the fluid check valve 300, the wetted fluid check valve "locks." If the piston 100 is temporarily held in a fixed position relative to the vented syringe barrel, further dispensing of liquid 20 into the vented syringe 900 is inhibited. In this manner, the dose of liquid 20 (medication) can be determined by the dimensions of the vented syringe barrel 910 and the position of the piston 100 within the vented syringe barrel 910. Figure 4B-3 then shows the completed pre-filled vented syringe 900, which can undergo quality control testing and be packaged as needed.

[0145] In this manner, vented syringes according to embodiments of the present disclosure may allow accurate fill volumes to be obtained without the use of pumps and without precise models of fluid viscosity. Additionally, vented syringe stopper plugging may be performed by the supplier, meaning that fill and finish operations may be accomplished using potentially simpler (and therefore potentially more reliable) filling machines.

[0146] Once filled, the syringe must retain its contents until dispensing is required. Fluid leakage can lead to inaccurate dosing, wastage, or user exposure to hazardous substances. Vented syringes according to embodiments of the present disclosure prevent fluid loss from the vented syringe due to the strong repellent pressure of the hydrophobic membrane 330. Hydrophilic membranes, by themselves or alternatives such as paper filters, slowly leak liquid due to capillary pressure. However, the liquid breakthrough resistance of hydrophobic membranes is more than an order of magnitude greater than that of hydrophilic membranes. The combination of hydrophilic porous material 310 and hydrophobic porous material 320 used in the vented syringes of the present disclosure inhibits leakage of liquid through the fluid check valve. This allows for easy loading of liquid into the vented syringe and also prevents liquid loss, protecting the user from exposure to toxic fluids.

[0147] Microfluidic Devices The small-scale fluid handling of microfluidic devices presents challenges. Microfluidic applications are particularly sensitive to the presence of air bubbles trapped in solutions, on surfaces, or within channels for a variety of reasons, including: Air bubbles can interfere with accurate dosing of reagents. Air bubbles can severely impede flow. Air bubbles can damage sensitive compounds and interfere with surface interactions.

[0148] Microfluidic devices can be used to measure the rheological properties of blood. The applicant's previously filed patent applications PCT / GB2017 / 053393 and PCT / AU2020 / 050902 disclose examples of such devices. By controlling the flow rate of a sample fluid within a measurement section of the device, viscosity and shear rate can be calculated from an appropriate fluidic device. For example, the fluidic device may include a pumping device for controlling the flow rate of the sample through a measurement unit in which the pressure drop within a channel of defined dimensions is measured. Using a known pressure drop, a known flow rate, and known channel dimensions, viscosity and shear rate can be calculated. The flow rate is controlled via a syringe pump, and the pressure drop across the measurement channel is measured using a differential pressure sensor. To measure the full spectrum of viscosity properties of non-Newtonian fluids (i.e., those that vary with shear rate), such as blood, the flow rate can be gradually varied over time according to a sinusoidal pattern.

[0149] However, if an air bubble is trapped in the fluid system between the syringe and the measurement channel, the bubble will compress and decompress due to the applied flow rate change and the subsequent variable pressure experienced throughout the fluid line. Therefore, the bubble will decrease and increase in volume due to the pressure change. This, in turn, results in a significant difference between the flow rate imposed by the syringe pump's movement and the actual flow rate of the sample passing through the fluid line where the pressure difference is measured. Because the flow rate considered in viscosity calculations is defined solely by the movement of the syringe pump's piston, this flow rate difference between the volume change in the syringe and the flow rate of the liquid in the channel where the pressure is measured creates an unacceptable error in the calculated viscosity. This error therefore invalidates the measurement. Additionally, if an air bubble is trapped within the measurement portion of the channel, less liquid than expected will be measured and / or the effective cross-section of the channel will be reduced. This will result in significant errors in the calculated viscosity and / or invalidate viscosity calculations that use the channel's physical / absolute cross-sectional size. This emphasizes the importance of removing air bubbles from the system.

[0150] The gas venting functionality of a vent syringe according to embodiments of the present disclosure may allow a user to remove air bubbles from a fluid sample before the fluid sample is injected into a microfluidic device, which may be relevant for samples that are hazardous, mechanically sensitive, prone to foaming, or highly viscous.

[0151] Additionally, some protocols may require sample collection from a microfluidic device. A vent syringe according to embodiments of the present disclosure may allow a user to insert the vent syringe into a receiving port with the piston positioned at the desired volume and remove the vent syringe once the appropriate volume is generated.

[0152] Such functionality may be applicable in many scenarios, for example, the administration of sensitive and expensive customized therapeutics, such as microfluidically generated gene therapy. In some scenarios, it is important to exclude gas from the sample, such as when analyzing liquid solutions containing volatile compounds. Thus, vented syringes according to embodiments of the present disclosure may enable simple protocols when working with sensitive applications.

[0153] Vented syringes according to the present disclosure may also have potential applications in the integration of vent closures and pumps into microfluidic chips. Vents integrated into microfluidic chips may allow for changes in pressure, volume, and composition within the chip. For example, vent closures may allow gas-producing reactions to occur "on-chip" without endangering downstream processes. Additionally, vented syringe pistons may allow for volumetric pumping within piston cylinders embedded within the chip material.

[0154] Fluid Dispensing Vented syringes according to embodiments of the present disclosure can be useful in fluid dispensing applications. Automated dispensing of fluid volumes in the sub-10 μL range is complicated by capillary and adhesive forces, which limit accurate volumetric dosing and increase problems caused by air bubbles. As a result, automated fluid handling methods, such as air-displacement pipettes, become increasingly inaccurate as volumes become smaller or more viscous. Low-dead-space syringes and / or positive-displacement pipettes may be preferred for bubble-free, viscous, and small-volume fluid handling applications. However, for high-throughput or time-dependent dosing, these devices may not be suitable because low-dead-space syringes still require priming and positive-displacement pipettes are limited to small total volumes. Therefore, in applications such as high-performance liquid chromatography where fluid lines require priming, vented syringes such as those disclosed herein may provide easier and simpler priming of fluid lines via vacuum.

[0155] Vacuum priming can be performed by applying a vacuum to pull liquid into the fluid line starting at the outlet. Thus, the entire fluid line can be purged of gas from start to finish in a single step. This saves the user time, effort, and materials, and can be a more reliable method than pushing liquid forward through the system.

[0156] Vented pistons according to the present disclosure may also be useful in automated fluid (or fluid) handling. Vented pistons according to embodiments of the present disclosure may be incorporated into syringe pumps to create automated fluid handling devices or robots. Automated fluid handling devices may include one or more control systems for controlling the movement of the piston within the fluid conduit and / or for controlling the configuration of fluid flow restricting members to allow or restrict fluid flow within the fluid flow path. Automated fluid handling devices may also control the positioning of fluid conduits (e.g., syringes) relative to fluid sources (such as vials). Automated fluid handling devices may automatically execute protocols for loading fluid, evacuating air, obtaining a desired fluid volume, moving to an outlet, and dispensing a controlled volume of fluid.

[0157] Vent pistons according to the present disclosure may be relatively simple to manufacture and / or operate due to the small number of individual components and / or the axially fixed arrangement of one or more components, such as the vent plunger shaft, stopper, fluid check valve, and / or fluid flow restrictor, relative to one another.

[0158] It will be understood by those skilled in the art that numerous variations and / or modifications may be made to the above-described embodiments without departing from the broad general scope of the present disclosure, and the present embodiments are therefore considered in all respects to be illustrative and not restrictive. [Prior art documents] [Patent documents]

[0159] [Patent Document 1] PCT / AU2020 / 050902 issue

Claims

1. a vent piston receivable within the fluid conduit, said piston comprising: a plunger body defining a fluid flow passage extending between an upstream end and a downstream end; a fluid check valve disposed across the fluid flow path, the fluid check valve being configurable to inhibit the passage of gas from the downstream end to the upstream end of the fluid flow path and to inhibit the passage of liquid from the upstream end to the downstream end of the fluid flow path; a fluid flow suppressing member disposed across the fluid flow path to suppress fluid flow within the fluid flow path; The fluid check valve is axially fixed relative to the plunger body.

2. The vented piston of claim 1 , wherein the fluid flow restricting member is configurable to selectively restrict fluid flow within the fluid flow passage.

3. 3. The ventilated piston of claim 2, wherein the fluid flow restricting member is configurable to permit fluid flow from the upstream end to the downstream end of the fluid flow path and to restrict fluid flow from the downstream end to the upstream end of the fluid flow path.

4. The vented piston of claim 1 , wherein the fluid flow restricting member is positioned downstream of the fluid check valve.

5. The vented piston of claim 1 , wherein the fluid flow restricting member comprises a valve.

6. The vented piston of claim 5 , wherein the fluid flow restricting member comprises a passive valve.

7. The vented piston of claim 5 , wherein the fluid flow restricting member comprises an actuatable valve.

8. The vented piston of claim 1 , wherein the fluid conduit includes an interior surface, and the piston forms a fluid seal with the interior surface of the fluid conduit.

9. The vented piston of claim 8 , wherein the plunger body is adapted to form a fluid seal with the interior surface of the fluid conduit.

10. 9. The vented piston of claim 8, wherein the piston further comprises a sealing member for forming a fluid seal with the interior surface of the fluid conduit.

11. The vented piston of claim 10 , wherein the sealing member includes a stopper at an upstream end of the piston, the stopper including an axial channel in fluid communication with the fluid flow path.

12. The fluid check valve is a hydrophilic porous material; a hydrophobic porous material disposed adjacent to the hydrophilic porous material; one surface of the hydrophilic porous material is in fluid communication with the upstream end of the fluid flow path, and one surface of the hydrophobic porous material is in fluid communication with the downstream end of the fluid flow path; 2. The vented piston of claim 1, wherein the hydrophilic porous material is configured to retain liquid from the upstream end to inhibit passage of gas from the downstream end to the upstream end, and the hydrophobic porous material is configured to inhibit passage of liquid from the upstream end to the downstream end.

13. 13. The ventilated piston of claim 12, wherein the hydrophilic porous material is disposed upstream of the hydrophobic porous material.

14. 14. A ventilated piston according to claim 12 or 13, wherein the plunger body comprises a retaining body for retaining the hydrophilic material and the hydrophobic porous material within the plunger body, and the fluid flow path extends through the retaining body.

15. 15. The vent piston of claim 14, wherein the retention body comprises a first portion and a second portion connectable to one another to cooperatively retain the hydrophilic porous material and the hydrophobic porous material.

16. 16. The vent piston of claim 15, wherein the first portion comprises recesses configured to receive the hydrophilic porous material and the hydrophobic porous material, and the second portion includes protrusions receivable within the recesses and configured to retain the hydrophilic porous material and the hydrophobic porous material within the recesses.

17. 15. The vented piston of claim 14, wherein the plunger body further comprises a plunger rod, and the retaining body includes a coupling member for coupling the retaining body to the plunger rod.

18. 18. The vented piston of claim 17, wherein the fluid flow passage extends through the plunger rod.

19. 20. The vented piston of claim 18, wherein the coupling member fluidly connects the plunger rod to the retaining body.

20. 15. The vented piston of claim 14, wherein the retaining body is integral with the plunger rod.

21. A ventilated syringe including the ventilated piston described in claim 1.

22. the vented syringe includes a syringe barrel defining the fluid conduit and adapted to at least partially receive the piston; When at least partially received within the syringe barrel, the piston divides the syringe barrel into an upstream section and a downstream section; 22. The vented syringe of claim 21, wherein the syringe barrel defines a fluid opening adjacent the upstream section.

23. 23. A method of filling a vented syringe according to claim 22, said method comprising: immersing the fluid opening in a liquid; displacing the piston downstream to draw liquid into the upstream section of the syringe barrel; and displacing the piston in an upstream direction to cause gas to flow through the fluid flow path in the downstream direction.

24. 24. The method of claim 23, wherein the piston is further displaced in the upstream direction to bring the fluid check valve into contact with liquid.

25. 25. The method of claim 23 or 24, further comprising displacing the piston in an upstream direction to force gas within the upstream section of the syringe barrel out of the fluid opening before displacing the piston in the downstream direction to draw liquid into the upstream section of the syringe barrel.

26. 24. The method of claim 23, further comprising displacing the piston in the downstream direction to allow gas to flow from the downstream section into the upstream section before immersing the fluid opening in a liquid source.

27. 24. The method of claim 23, further comprising displacing the piston downstream to draw additional liquid into the upstream section of the syringe barrel.

28. 24. The method of claim 23, further comprising configuring the fluid flow restricting member to restrict fluid flow from the downstream end to the upstream end of the fluid flow path before displacing the piston downstream to draw liquid into the upstream section of the syringe barrel.

29. 24. The method of claim 23, further comprising configuring the fluid flow restricting member to allow fluid flow from the upstream end to the downstream end of the fluid flow passage before displacing the piston in an upstream direction to allow gas to flow in the downstream direction through the fluid flow passage.

30. 30. The method of claim 29, wherein configuring the fluid flow restricting member to restrict fluid flow comprises configuring the fluid flow restricting member to form a fluid seal across the fluid flow path.

31. 23. A method of filling a vented syringe according to claim 22, said method comprising: connecting the fluid opening to a liquid source; causing the liquid to flow into the upstream section of the syringe barrel such that gas within the upstream section flows downstream through the fluid flow path.

32. 32. The method of claim 31, wherein the position of the piston within the syringe barrel is selected to define a predetermined fill volume.

33. a fluid conduit having an interior surface; 10. The fluid system of claim 1, comprising: a vented piston at least partially received within the fluid conduit and forming a fluid seal with the interior surface of the fluid conduit to separate the fluid conduit into an upstream section for containing gas and liquid and a downstream section for receiving the gas.

34. 34. The fluid system of claim 33, further comprising an automatic motion control system configured to engage the piston to control movement of the piston.

35. The automatic motion control system includes: actuating the piston to move the piston downstream to draw fluid into the fluid conduit; actuating the piston to move the piston in an upstream direction to expel gas from the upstream section of the fluid conduit; actuating the piston to move in the downstream direction to draw more fluid into the upstream section to obtain a desired fluid volume; 35. The fluid system of claim 34, configured to actuate the piston to move it in the upstream direction to dispense a controlled volume of the fluid.

36. 35. The fluid system of claim 33 or 34, further comprising an automatic fill system, wherein the position of the piston within the fluid conduit is selected to define a predetermined fill volume.

37. The vented piston of claim 1 or the vented syringe of claim 21, wherein the fluid flow restrictor is axially fixed to the plunger body.

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