Patent Description:
The invention relates to fluidics technology, and more particularly to a microfluidic multilayer peristaltic pump for control of fluid flow through microchannels.

Microfluidics systems are of significant value for acquiring and analyzing chemical and biological information using very small volumes of liquid. Use of microfluidic systems can increase the response time of reactions, minimize sample volume, and lower reagent and consumables consumption. When volatile or hazardous materials are used or generated, performing reactions in microfluidic volumes also enhances safety and reduces disposal quantities.

Microfluidic devices have become increasingly important in a wide variety of fields from medical diagnostics and analytical chemistry to genomic and proteomic analysis. They may also be useful in therapeutic contexts, such as mobile low flow rate drug delivery/infusion systems and continuous monitoring systems for animal drug models. For example, a micropump may be used for periodic or continuous administration of fluid to a subject in need thereof or may be used to monitor efficacy of an administered drug over time by taking periodic samples.

<CIT> discloses a microfluidic device comprising an annular body having a top surface, a bottom surface, an inner surface defining an aperture, and a substantially concave wall extending downward from the bottom surface to a base; an elastic collar fixedly attached to the bottom surface of the annular body, the elastic collar comprising a flange disposed around the periphery thereof and a bottom surface fixedly attached to the base of the annular body, wherein the flange is configured to be mated to the bottom surface of the annular body; and a rigid substrate having a top surface, a bottom surface,comprising an inlet and an outlet disposed in the top surface and forming a channel with the elastic collar between the input port and the output port.

<CIT> discloses a membrane pump with an annular cavity-shaped working chamber which is bounded by a fixed working chamber outer wall and by a deformable working chamber inner wall (annular diaphragm), wherein a pressure member provided with an eccentric drive presses the annular diaphragm against the working chamber outer wall in a circumferential sealing region.

<CIT> describes a diaphragm pump having a cylindrical diaphragm fixed at one point on its periphery to a pump body and acted upon by an internal compression member.

However, the micro-components required for these devices are often complex and costly to produce. Thus, a need exists for a low-cost microfluidic device that integrates with a motor to form a micropump for integration into, for example, a mobile infusion device.

A microfluidic pump has been developed in order to provide low cost, high accuracy means for disposable infusion devices and fluidic sampling/monitoring devices. Devices utilizing the microfluidic pump, as well as methods for manufacture and performing a microfluidic process are also provided.

Accordingly, in one aspect, the invention provides a microfluidic device. The microfluidic device includes an annular body having a top surface, a bottom surface, an inner surface defining an aperture, and a substantially concave wall extending downward from the bottom surface to a base, the annular body comprising an input port and an output port disposed therein; an elastic collar fixedly attached to the bottom surface of the annular body, the elastic collar comprising a flange disposed around the periphery thereof and a bottom surface fixedly attached to the base of the annular body, wherein the flange is configured to be mated to the bottom surface of the annular body; and a rigid substrate having a top surface, a bottom surface, and a tapered extension extending downward from the bottom surface, the rigid substrate comprising an inlet and an outlet disposed in the top surface and positioned in alignment with input port and output port of the annular body, wherein the bottom surface of the rigid substrate is fixedly attached to the top surface of the annular body and the tapered extension is sized and shaped to fit within the aperture, thereby forming a channel with the elastic collar between the input port and the output port. In various embodiments, the annular body is bonded to the rigid substrate. In various embodiments, the microfluidic device may further include an inlet connector and an outlet connector disposed on the top surface of the rigid substrate, each being respectively provided in fluid communication with the inlet port and outlet port of the annular body.

The elastic collar of the microfluidic device may include one or more detents formed in an inner surface thereof, each detent being respectively in fluid communication with the inlet and the outlet of the rigid substrate. In various embodiments, an inner surface of the elastic collar is concave to further define the channel. In various embodiments, the flange of the elastic collar is bonded to the bottom surface of the annular body and wherein the bottom surface of the tapered extension of the rigid substrate is bonded to the inner surface of the base. In various embodiments, the tapered extension of the rigid substrate comprises a groove disposed in a surface thereof, the groove being positioned parallel to the top surface of the rigid substrate, wherein the groove is configured to be mated with the elastic collar.

In various embodiments, the elastic collar further comprises a rib disposed along a circumference thereof, the rib being positioned substantially parallel to the flange. In various embodiments, the rigid substrate further comprises an extension extending away from an axis thereof, the extension having disposed therein a microfluidic channel configured to provide fluid communication between the outlet port of the annular body and the outlet of the rigid substrate.

In yet another aspect, the invention provides a pump that includes the microfluidic device as herein described; a rotary actuator removably attached to the base of the microfluidic device, the rotary actuator configured to compress a portion of the elastic collar of the microfluidic device; and a motor coupled to the rotary actuator and configured to rotate the rotary actuator around the periphery of the microfluidic device. In various embodiments, the rotary actuator includes a body having an aperture disposed therein, the aperture being sized and shaped to accept the base and rigid collar of the microfluidic device; and one or more balls fixedly attached to an inner surface of the aperture of the body, the one or more balls being configured to compress a portion of the elastic collar as the rotary actuator rotates. Each of the one or more balls is fixedly attached to the inner surface of the aperture of the rotary actuator by a spring, thereby providing positive engagement between the rotary actuator and the microfluidic device.

In various embodiments, the pump includes reservoir in fluid communication with an inlet connector of the microfluidic device, the reservoir being configured to: (i) contain a fluid to be delivered by the pump or (ii) accept a fluid to be sampled by the pump. In various embodiments, the pump includes a needle in fluid communication with an outlet connector of the microfluidic device, the needle being configured to: (i) administer fluid from the reservoir into a subject in need thereof or (ii) obtain a sample from a subject. In various embodiments, the pump also includes a controller and a power supply, wherein the controller configured to supply voltage from the power supply to the motor to rotate the rotary actuator. In various embodiments, the controller may also be configured to communicate with a hand-held device regarding information selected from the group consisting of amount of fluid being dispensed, time of dispensing, duration of dispensing, amount of fluid remaining in the reservoir, time of sampling, duration of sampling, and amount of volume remaining in the reservoir for further sampling.

A microfluidic pump and device containing the pump have been developed in order to provide low cost, high accuracy, and low flow rate means for disposable infusion devices. Advantageously, the rate of fluid flow within the pump is essentially constant even at very low flow rates.

Before the present compositions and methods are described, it is to be understood that this invention is not limited to particular compositions, methods, and experimental conditions described, as such compositions, methods, and conditions may vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only in the appended claims.

As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, references to "the method" includes one or more methods, and/or steps of the type described herein which will become apparent to those persons skilled in the art upon reading this disclosure and so forth.

The term "comprising," which is used interchangeably with "including," "containing," or "characterized by," is inclusive or open-ended language and does not exclude additional, unrecited elements or method steps. The phrase "consisting of" excludes any element, step, or ingredient not specified in the claim. The phrase "consisting essentially of" limits the scope of a claim to the specified materials or steps and those that do not materially affect the basic and novel characteristics of the claimed invention. The present disclosure contemplates embodiments of the invention devices and methods corresponding to the scope of each of these phrases. Thus, a device or method comprising recited elements or steps contemplates particular embodiments in which the device or method consists essentially of or consists of those elements or steps.

Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods and materials are now described.

With reference now to <FIG>, the invention provides a microfluidic device <NUM> for use in conjunction with a rotary actuator <NUM> to form a microfluidic pump <NUM>. The microfluidic device <NUM> includes an annular body <NUM> having a top surface <NUM>, a bottom surface <NUM>, and an inner surface <NUM> defining an aperture <NUM>. Disposed within the annular body <NUM> are one or more input ports <NUM> and output ports <NUM>. In various embodiments, the one or more input ports <NUM> and output ports <NUM> are disposed along the width (i.e., substantially parallel to axis C) of the annular body <NUM> to provide fluid communication between the top surface <NUM> and the bottom surface <NUM> of the annular body <NUM>. It should be understood that while <FIG> and <FIG> show each of the input port <NUM> and output port <NUM> in cross-sectional format for explanatory purposes only, the input port <NUM> and output port <NUM> extend through the annular body <NUM>. Extending from the bottom surface <NUM> of the annular body <NUM> is a base <NUM>. In various embodiments, base <NUM> is connected to the bottom surface <NUM> of the annular body <NUM> by a substantially concave wall <NUM> running around a portion of the periphery of the annular body <NUM>, leaving a space between the base <NUM> and the bottom surface <NUM> around a majority of the periphery of the annular body <NUM>. Annular body <NUM> may be formed from any non-elastic material such as, but not limited to, metal, plastic, non-elastic polymers, silicon (such as crystalline silicon), or glass. In various embodiments, the material from which the annular body <NUM> is formed is biologically inert and amenable to known sterilization techniques.

The microfluidic device <NUM> further includes an elastic collar <NUM> that is sized and shaped to be fixedly attached to the annular body <NUM>, thereby filling the space between the base <NUM> and the bottom surface <NUM> thereof. Elastic collar <NUM> may include a top surface <NUM>, a bottom surface <NUM>, and a substantially concave wall <NUM> (i.e., protruding inward toward axis C) extending downward from the top surface <NUM>. The concave wall <NUM> may substantially mirror the curvature of the concave wall <NUM> of the annular body <NUM>. In various embodiments, elastic collar <NUM> may include a flange <NUM> disposed around the periphery thereof, the flange <NUM> extending away from the axis C. The flange <NUM> may be sized and shaped to contact the bottom surface <NUM> of the annular body <NUM>. In various embodiments, flange <NUM> may include one or more inlet/outlet detents <NUM> formed in the inner surface <NUM> thereof, wherein each of the inlet/outlet detents <NUM> are disposed in alignment with and in fluid communication with the one or more input ports <NUM> and output ports <NUM> of the annular body <NUM> when mated thereto.

Elastic collar <NUM> may further include a gap <NUM>, such that elastic collar <NUM> is not a continuous ring. The gap <NUM> exposes a portion of the concave wall <NUM> of annular body <NUM> that separates the input port <NUM> and output port <NUM>. As shown in <FIG>, concave wall <NUM> of the elastic collar <NUM> may further include a rib <NUM> disposed along its circumference, the rib <NUM> being positioned substantially parallel to the flange <NUM>. The rib <NUM> provides an increased cross-sectional thickness of the elastic collar <NUM> to increase the compressive strength and engagement of a rotary actuator <NUM> (see <FIG>). One skilled in the art would understand that the rib <NUM> may be formed in any of a number of suitable shapes such as a continuous raised element (as shown) or a series of bumps (not shown). In various embodiment, elastic collar <NUM> may be formed from any deformable and/or compressible material, such as, for example, rubber or an elastomer. In various embodiments, elastic collar <NUM> is formed from thermoplastic elastomers.

As one of skill in the art would understand, annular body <NUM> and elastic collar <NUM> may be formed as individual components, or the components may be joined using a process of two-shot molding or overmolding, in which case first one polymer and then the other is injected into a mold tool to form a singular piece. A variety of techniques may be utilized to fixedly attach the annular body <NUM> to the elastic collar <NUM>, where the flange <NUM> of the elastic collar <NUM> is fixedly attached to the bottom surface <NUM> of annular body <NUM> and the bottom surface <NUM> of the elastic collar <NUM> is fixedly attached to the base <NUM> of the annular body <NUM>.

For example, the parts may be joined together using UV curable adhesive or other adhesives that permit for movement of the two parts relative one another prior to curing of the adhesive/creation of bond. Suitable adhesives include a UV curable adhesive, a heat-cured adhesive, a pressure sensitive adhesive, an oxygen sensitive adhesive, and a double-sided tape adhesive. Alternatively, the parts may be coupled utilizing a welding process, such as, an ultrasonic welding process, a thermal welding process, a laser welding process, and/or a torsional welding process. One of skill in the art will readily appreciate that elastomeric and non-elastomeric polymers can be joined in this way to achieve fluid tight seals between the parts.

Disposed within annular body <NUM> is a substantially rigid substrate <NUM> having a top surface <NUM> and a bottom surface <NUM>, with a tapered extension <NUM> extending from the bottom surface <NUM>. As such, a bottom surface <NUM> of the tapered extension <NUM> seats on the inner surface <NUM> of base <NUM> of the annular body <NUM>, while the top surface <NUM> of the annular body <NUM> abuts to and is attached to the bottom surface <NUM> of the rigid substrate <NUM>. Thus, the rigid substrate <NUM> forms a flange <NUM> covering the annular body <NUM> such that the top surface <NUM> of the annular body <NUM> is mated to the bottom surface <NUM> of the rigid substrate <NUM>. In other words, tapered extension <NUM> of the substantially rigid body <NUM> is sized and shaped to fit within the aperture <NUM> of the annular body <NUM>. In various embodiments, the rigid substrate may include an extension <NUM> extending in a direction away from axis C. Disposed within the extension <NUM> may be a microfluidic channel <NUM> configured to provide fluid communication between the outlet <NUM> of the rigid substrate and the output port <NUM> of the annular body <NUM>.

Accordingly, the inner surface <NUM> of the elastic collar <NUM> forms a fluid-tight channel <NUM> with the tapered extension <NUM> of the rigid substrate <NUM>, where the channel <NUM> provides fluid communication between the input port <NUM> and output port <NUM> of the annular body <NUM> via detents <NUM> of the elastic collar <NUM>. In various embodiments, the inner surface <NUM> of the elastic collar <NUM> may be substantially concave (i.e., protruding away from axis C), thereby further defining the channel <NUM> between the rigid substrate <NUM> and the elastic collar <NUM>. In various embodiments, the tapered extension <NUM> of rigid substrate <NUM> may include a groove <NUM> formed in a portion thereof, wherein the groove <NUM> extends around the periphery thereof and is positioned substantially parallel to the top surface <NUM> of the annular base <NUM>. When so provided, the groove <NUM> serves to further increase the volume capacity of channel <NUM>.

Disposed in the upper surface <NUM> of the rigid substrate <NUM> may be an inlet <NUM> and an outlet <NUM>, both of which may be positioned in alignment with, and therefore in fluid communication with, the one or more input ports <NUM> and output ports <NUM> of the annular body when rigid substrate <NUM> and the annular body <NUM> are attached to each other. As with the annular body <NUM>, rigid substrate <NUM> may be formed from any non-elastic material such as, but not limited to, metal, plastic, non-elastic polymers, silicon (such as crystalline silicon), or glass. In various embodiments, rigid substrate <NUM> is formed from the same material as that of the annular body <NUM> to reduce overall manufacturing costs.

Thus, in this configuration, the microfluidic device <NUM> relies upon forces directed toward the axis C to actuate pumping action. Likewise, the configuration provides the added advantage of reducing manufacturing costs and facilitating assembly thereof. When a force F (see <FIG>), provided for example via a deformation element, such as a ball <NUM> of a rotary actuator <NUM>, is applied to the elastic collar <NUM> and/or to the concave wall <NUM> of the annular body <NUM>, at least a portion of the concave wall <NUM> of the elastic collar <NUM> is compressed into the channel <NUM> formed between elastic collar <NUM> and rigid substrate <NUM>, thereby occluding at least a portion of the channel <NUM> at the site of compression to displace a portion of fluid within channel <NUM>. As the rotary actuator <NUM> rotates, the site of compression translates along concave wall <NUM>, resulting in peristaltic fluid flow within channel <NUM> in the direction of rotation.

In various embodiments, concave wall <NUM> occludes, in the compressed state, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, at least about <NUM>%, or essentially all of the uncompressed cross-sectional area of the channel <NUM> at the site of compression. The compression may create a fluid-tight seal between the elastic collar <NUM> and the tapered extension <NUM> of the rigid substrate within the channel <NUM> at the site of compression. When a fluid-tight seal is formed, fluid, e.g., a liquid or gas, is prevented from passing along the channel <NUM> from one side of the site of compression to the other side of the site of compression. The fluid-tight seal may be transient, e.g., the elastic collar <NUM> may fully or partially relax upon removal of the compression, thereby fully or partially reopening channel <NUM>. The channel <NUM> may have a first cross-sectional area in an uncompressed state and a second cross-sectional area in the compressed state. For example, a ratio of the cross-sectional area at the site of compression in the compressed state to the cross-sectional area at the same site in the uncompressed state may be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or about <NUM>. One skilled in the art would appreciate that the surfaces of the channel <NUM> formed in the microfluidic device <NUM> may be modified, for example, by varying hydrophobicity. For instance, hydrophobicity may be modified by application of hydrophilic materials such as surface-active agents, application of hydrophobic materials, construction from materials having the desired hydrophobicity, ionizing surfaces with energetic beams, and/or the like.

A variety of methods may be utilized to fixedly attach the annular body <NUM> to the rigid substrate <NUM>. For example, the parts may be joined together using UV curable adhesive or other adhesives that permit for movement of the two parts relative one another prior to curing of the adhesive/creation of bond. Suitable adhesives include a UV curable adhesive, a heat-cured adhesive, a pressure sensitive adhesive, an oxygen sensitive adhesive, and a double-sided tape adhesive. Alternatively, the parts may be coupled utilizing a welding process, such as, an ultrasonic welding process, a thermal welding process, and a torsional welding process. In a further alternative, the parts may be joined using a process of two-shot molding or overmolding, in which case first one polymer and then the other is injected into a mold tool to form a singular piece. One of skill in the art will readily appreciate that elastomeric and non-elastomeric polymers can be joined in this way to achieve fluid tight seals between the parts.

Referring now to <FIG>, in another aspect, a microfluidic pump <NUM> is provided, which utilizes the microfluidic device <NUM>, described herein. Thus, the microfluidic pump <NUM> includes a microfluidic device <NUM> and a rotary actuator <NUM> that is removably attached to the base <NUM> of the microfluidic device <NUM>. The rotary actuator <NUM> includes a body <NUM> having an aperture <NUM> disposed therein, where the aperture <NUM> is sized and shaped to accept the annular body <NUM> and the rigid collar <NUM> therein. Fixedly attached to an inner surface <NUM> of the aperture <NUM> of the body <NUM> is one or more balls <NUM> configured to compress a portion of the concave wall <NUM> of elastic collar <NUM> as the rotary actuator <NUM> rotates. In various embodiments, each of the one or more balls <NUM> may be fixedly attached to a spring <NUM> disposed within the body <NUM> to further increase force F applied to the annular elastic body <NUM> of the microfluidic device <NUM>. When so provided, the springs <NUM> and balls <NUM> of the rotary actuator <NUM> work in conjunction to lock over the base <NUM> and onto the concave wall <NUM> and/or the elastic collar <NUM> of the microfluidic device <NUM>, thereby resulting in positive, removable engagement between the rotary actuator <NUM> and the microfluidic device <NUM>.

Mechanical rotation of the one or more balls <NUM> by the rotary actuator <NUM> results in translation of a site of compression along the elastic collar <NUM> of the microfluidic device <NUM>, thereby creating an effective pumping action resulting in the flow of fluid within the channel <NUM> in the direction of rotation of the rotary actuator <NUM>. Thus, the volume to be pumped may be adjusted by varying the number of balls <NUM> within the rotary actuator <NUM>, with the spacing between each ball <NUM> being a fixed amount of volume to be pumped. The flow of fluid may then enter and exit through an appropriate inlet connector <NUM> and outlet connector <NUM> disposed (or formed) on the top surface <NUM> of the rigid substrate <NUM>, where inlet connector <NUM> is provided in fluid communication with the inlet <NUM> and the outlet connector <NUM> is provided in fluid communication with the outlet <NUM>. As should be understood, inlet connector <NUM> may be provided in fluid communication with a reservoir <NUM> containing a fluid to be dispensed, while outlet connector <NUM> may be provided in fluid communication with tubing or a needle for administration of the fluid to a subject. In various embodiments, inlet connector <NUM> and outlet connector <NUM> may be formed as luer locks to provide a fluid-tight fitting.

In various embodiments, mechanical rotation of the rotary actuator <NUM> may be accomplished by an electric motor <NUM> coupled to the rotary actuator <NUM> by a shaft <NUM>. The electric motor <NUM> and rotary actuator <NUM> may be provided in a housing <NUM> together with a power supply <NUM> and a controller <NUM>, such that the rotary actuator <NUM> is configured to radially traverse balls <NUM> along elastic collar <NUM> of the microfluidic device <NUM> when the microfluidic device <NUM> is placed in positive engagement with the rotary actuator <NUM> and voltage <NUM> is directed to the electric motor <NUM>. As will be appreciated by those of skill in the art, the rotational direction of the rotary actuator <NUM> with relation to the microfluidic device <NUM> dictates the direction of flow within the channel <NUM>. As such, one skilled in the art would appreciate that, advantageously, fluid flow through the pump <NUM> may be bidirectional. In addition, since the microfluidic device <NUM> is configured to flow liquids and gases, the flow of gaseous fluid may provide for initial priming liquid fluid within the pump <NUM>.

The rotary actuator <NUM> may therefore be rotated by applying a voltage <NUM> from a power source <NUM>, such as a rechargeable battery, to the electric motor <NUM> controlling movement thereof. As such, the invention further provides a method for performing a microfluidic process which includes applying a voltage <NUM> to a microfluidic pump <NUM> as described herein. The applied voltage <NUM> activates the electric motor <NUM>, which rotates rotary actuator <NUM> attached thereto, thereby resulting in repeated translation of a site of compression along the elastic collar <NUM>.

A wide range of pulses per second may be applied to the electric motor <NUM>, thereby effectuating a wide range of flow rates within the microfluidic device <NUM>. The fluid flow may be essentially constant, with little or no shear force being imposed on the fluid, even at very low flow rates. These characteristics of the pump <NUM> enhance the accuracy of the amount of fluid being delivered (e.g., enabling delivering of micro amounts of infusion fluid), while low flow rates provide for consistent delivery without the effects of a bolus amount. As such, a low, constant pumped flow rate can also be very useful to ensure dosing accuracy.

The following exemplary embodiment describes use of a microfluidic pump <NUM> of the present invention for use in a low cost, disposable device for administering a fluid (e.g., insulin) to a subject. The pump <NUM> may include a reservoir <NUM> containing the fluid (e.g., insulin) to be administered to the subject, where the reservoir <NUM> is in fluid communication with the inlet <NUM> of the microfluidic device <NUM>. The outlet <NUM> of the microfluidic device <NUM> may be connect to tubing (e.g., a catheter) or a needle <NUM> that is inserted into tissue (i.e., subcutaneous fat or muscle) of the subject. The microfluidic pump <NUM> may include a controller <NUM> configured to direct voltage <NUM> from a power supply <NUM> to the motor <NUM>, thereby administering a predetermined amount of fluid to the subject at appropriate times of day or, if appropriate, to provide continuous subcutaneous therapy (e.g., insulin therapy). All of the foregoing components of the device (i.e., the microfluidic device <NUM>, the rotary actuator <NUM>, the motor <NUM>, power supply <NUM>, controller <NUM> and reservoir <NUM>) may be disposed within a single housing <NUM>. Thus, the device may be configured such that the microfluidic device <NUM> and the reservoir <NUM> are disposable, such as being provided on a disposable card that is replaced when all or a majority of the fluid within the reservoir <NUM> has been administered to the subject.

In another exemplary embodiment describing use of the microfluidic pump <NUM> of the present invention, the microfluidic pump <NUM> may be used as a low cost, disposable sampling device for drug testing on an animal model of disease. The pump <NUM> may include a multitude of empty reservoirs <NUM> configured to contain a sample (e.g., blood) from a subject (e.g., animal model), where each reservoir <NUM> is in fluid communication with the inlet <NUM> (which serves as the sample outlet) of the microfluidic device <NUM>. The outlet <NUM> (serving as the sample inlet) of the microfluidic device <NUM> may be connected to tubing (e.g., a catheter) or a needle <NUM> that is inserted into tissue (i.e., subcutaneous fat or muscle) or a vein of the subject. As above, the microfluidic pump <NUM> may include a controller <NUM> configured to direct voltage <NUM> from a power supply <NUM> to the motor <NUM> at specific times of the day and/or days of the week, thereby obtaining periodic samples from the subject. Such periodic sampling may, for example, be used to monitor drug efficacy over time within the subject. Likewise, the device may be used to for sampling of gaseous materials for assays requiring small, accurate amounts of sampled gas (e.g., mass spectrometry).

Claim 1:
A microfluidic (<NUM>) device comprising:
a) an annular body (<NUM>) having a top surface (<NUM>), a bottom surface (<NUM>), an inner surface (<NUM>) defining an aperture (<NUM>), and a substantially concave wall (<NUM>) extending downward from the bottom surface (<NUM>) to a base (<NUM>), the annular body (<NUM>) comprising an input port (<NUM>) and an output port (<NUM>) disposed therein;
b) an elastic collar (<NUM>) fixedly attached to the bottom surface (<NUM>) of the annular body (<NUM>), the elastic collar (<NUM>) comprising a flange (<NUM>) disposed around the periphery thereof and a bottom surface fixedly attached to the base (<NUM>) of the annular body (<NUM>), wherein the flange (<NUM>) is configured to be mated to the bottom surface (<NUM>) of the annular body (<NUM>); and
c) a rigid substrate (<NUM>) having a top surface (<NUM>), a bottom surface (<NUM>), and a tapered extension (<NUM>) extending downward from the bottom surface (<NUM>), the rigid substrate (<NUM>) comprising an inlet (<NUM>) and an outlet (<NUM>) disposed in the top surface (<NUM>) and positioned in alignment with input port (<NUM>) and output port (<NUM>) of the annular body (<NUM>), wherein the bottom surface (<NUM>) of the rigid substrate (<NUM>) is fixedly attached to the top surface (<NUM>) of the annular body (<NUM>) and the tapered extension (<NUM>) is sized and shaped to fit within the aperture (<NUM>), thereby forming a channel (<NUM>) with the elastic collar (<NUM>) between the input port (<NUM>) and the output port (<NUM>).