Array of hollow fibers and a system and method of manufacturing same

An array of hollow fibers including a plurality of hollow fibers of a predetermined diameter configured to receive a gas having oxygen therein and transfer the oxygen to a fluid and/or transfer carbon dioxide in the fluid to a gas. The array is configured in a predetermined pattern having a predetermined packing density that is a fraction of a total cross-sectional area of the array occupied by the hollow fibers.

FIELD OF THE INVENTION

This invention relates to an improved array of hollow fibers and a system and method for manufacturing same.

BACKGROUND OF THE INVENTION

Conventional hollow fiber oxygenators may be used to oxygenate the blood for patients suffering with diseased or damaged lungs. One conventional oxygenator, often referred to as a wrapped hollow fiber oxygenator, relies on hollow fibers wrapped around a hollow core. The wrapped design often results in a random or irregular spacing of the hollow fibers. Additionally, because the hollow fibers are wrapped about a hollow core, there is a relatively large amount of void space in the oxygenator. Such a design may compromise the efficiency of the oxygenator.

Another conventional oxygenator, often referred to as a bundled oxygenator, relies on an array of hollow fibers bundled together potted in glue at each end. The glue is then cut to form a header on each end of the array. The bundling design of the array typically results in a random arrangement of hollow fiber which prevents the hollow fibers from being packed closely and in a regular pattern which may compromise the efficiency of the oxygenator.

BRIEF SUMMARY OF THE INVENTION

This invention features an array of hollow fibers including a plurality of hollow fibers of a predetermined diameter configured to receive a gas having oxygen therein and transfer the oxygen to a fluid and/or transfer carbon dioxide in the fluid to a gas. The array is configured in a predetermined pattern having a predetermined packing density that is a fraction of a total cross-sectional area of the array occupied by the hollow fibers.

In one embodiment, the array may be configured such that the distance between the hollow fibers is less than or substantially equal to the predetermined diameter. The predetermined packing density of the array may be configured to be a fraction of the total cross-sectional area of the array occupied by the plurality of hollow fibers. The fraction may be in the range of 0.20 to about 0.90. The predetermined diameter may be less than or equal to about 0.2 mm. The plurality of hollow fibers may be configured in a hexagonal arrangement. The plurality of hollow fibers may be configured to be hexagonally closely packed. The array may include a plurality of headers configured to align the plurality of hollow fibers in the predetermined orientation.

This invention features a method for manufacturing an array of hollow fibers, the method includes: a) providing an array manufacturing device including a base defining a bed and an adhesive applicator receivable in the base, b) providing a plurality of shims each configured to fit into the bed, c) providing a plurality of layers of hollow fibers, d) placing the plurality of shims into the bed, e) applying adhesive to the applicator, f) positioning the applicator to contact and distribute the adhesive to a top shim of the plurality of shims in the bed, g) placing a first layer of hollow fibers over the top shim with adhesive thereon, h) rolling the adhesive away from a center portion of the first layer of hollow fibers, i) removing one of the plurality of shims from the bed, j) placing another layer of hollow fibers over the first layer of hollow fibers, k) applying adhesive to the adhesive applicator, l) positioning the applicator to contact and distribute the adhesive to the next layer of hollow fibers, m) rolling the adhesive away from a center portion of the next layer of hollow fibers, and n) repeating at least steps i) through m) until an array having a predetermined number of layers is formed.

In one embodiment, the adhesive applicator may include a plurality of blades and step of applying the adhesive may include applying the adhesive to the blades. Each of the blades may include a contact surface and the step of applying the adhesive may include applying the adhesive to the contact surface. The method may include the step of pivotably attaching the adhesive applicator to the base. The method may include the step of providing a roller to roll the adhesive away from the center portion. The method may include the step of trimming excess adhesive from a completed array of hollow fibers.

This invention also features a method for manufacturing an array of hollow fibers, the method including: a) providing an array manufacturing device including a base defining a bed with opposing sides an adhesive applicator receivable in the base, b) providing a plurality of shims each sized to fit the opposing sides, c) providing a plurality of layers of hollow fibers, d) placing a pair of opposing shims adjacent to the opposing sides, e) placing a layer of hollow fibers between the opposing shims, f) applying adhesive to the opposing shims and the layer of hollow fibers, g) rolling the adhesive away from a center portion of the layer of hollow fibers, and h) repeating at least steps d) through g) until an array having a predetermined number of layers of hollow fibers is formed.

In one embodiment, the method may include the step of pivotably attaching the adhesive applicator to the base.

This invention further features a method of manufacturing an array of fibers, the method including: a) providing a plurality of layers of hollow fibers, b) providing first and second end-headers each including a plurality of recesses on one side configured to fit a layer of the plurality of hollow fibers, c) providing a plurality of mid-headers each including a plurality of recesses on both sides configured to fit a layer of the plurality of hollow fibers, d) applying adhesive to one end-header and one mid-header, e) sandwiching one layer of the plurality of hollow fibers between the end-header and the mid-header, f) applying adhesive to another mid-header, g) sandwiching another layer of hollow fibers between two mid-headers, h) repeating steps f) and g) a predetermined number of times, i) applying adhesive to the second end-header, and j) sandwiching a final layer of hollow fibers between the end-header and a last mid-header.

This invention also features a system for manufacturing an array of hollow fibers. The system includes an array manufacturing device including a base defining a bed and an adhesive applicator receivable in the base, a plurality of shims each configured to fit into the base, a plurality of layers of hollow fibers sized to fit into the base, and a roller.

In one embodiment, the adhesive applicator may include opposing arms and a plurality of blades therebetween. Each of the blades may include an adhesive contact surface. The adhesive applicator may be pivotably attached to the base. The method may include each of the plurality of shims may have a thickness approximately equal to the thickness of one of the plurality of layers of hollow fibers. The plurality of blades may form a predetermined shape. The predetermined shape may include the shape of a lung or a rectangular shape.

This invention also features a system for manufacturing an array of hollow fibers. The system includes an array manufacturing device including a base defining a bed with opposing sides an adhesive applicator receivable in the base, a plurality of layers of hollow fibers, a plurality of shims each sized to fit the opposing sides, and a roller.

In one embodiment, the method may include the step of pivotably attaching the adhesive applicator to the base.

DETAILED DESCRIPTION OF THE INVENTION

There is shown inFIG. 1one example of conventional wrapped oxygenator10which may be used to receive a gas having oxygen therein and transfer the oxygen to a physiological fluid. As discussed in the Background section above, conventional wrapped oxygenator includes hollow fibers12wrapped about hollow core14. However, such a design often results in random or irregular spacing of the hollow fibers and produces a large amount of void space which may compromise the efficiency of oxygenator10.

Conventional bundled oxygenator20,FIG. 2, includes array21of hollow fibers22bundled together in potting glue24. The glue is then cut to form a header on each end of array21. However, the bundling design typically results in a random arrangemert of hollow fibers22, e.g., as indicated at26. This prevents fibers22from being packed closely and in a regular pattern which may compromise the efficiency of oxygenator20.FIG. 3shows a more detailed view of the random or irregular arrangement of hollow fibers22.

Thus, conventional wrapped oxygenator10,FIG. 1, and bundled oxygenator20,FIG. 2, may not provide a sufficient density of hollow fibers to effectively oxygenate blood or similar type physiological fluid.

In contrast, array30,FIG. 4of one embodiment of this invention, includes a plurality of fibers32each having a predetermined diameter, e.g., outer diameter d-48of fiber42and outer diameter d-50of fiber44. Fibers32are each configured to receive a gas, e.g., exemplary gas34, such as ambient air, an oxygen gas, or any gas having oxygen therein, and transfer the oxygen in the gas to a fluid35and/or transfer carbon dioxide in fluid35to gas34. The fluid which may be a physiological fluid, such as blood or plasma or similar type physiological fluid, or it may be an organic or inorganic fluid. Array30is configured in a predetermined pattern with a predetermined packing density. For example, array30may be configured such that the distance between hollow fibers32is less than or substantially equal to the diameter of the hollow fibers32. In one design, distance d-40between hollow fibers42and44is less than the diameter d-48of fiber42and the diameter d-50of hollow fiber44. Hollow fibers32preferably have a diameter of about 0.2 mm, although the diameter may be larger or smaller than 0.2 mm. The result is fibers32of array30provide for an increased packing density of hollow fibers in array30when compared to the conventional oxygenators or similar type arrays of hollow fibers.

In one example, array30includes a plurality of hollow fibers32that are configured to be hexagonally closely packed, e.g., as shown inFIG. 5A. This is often referred to hexagonally closely packed because one can imagine space-filling hexagons overlapping the circular cross-sections of plurality of hollow fibers32with the vertices of hexagons at the center of each of the circular-shaped plurality of fibers, e.g., hexagon55,FIG. 5B. A closer look at a portion of hexagon55,FIG. 5C, shows that there may be triangles, e.g., exemplary triangle57, that are also space filling and can represent a unit-cell in which the area fraction can be calculated using the formula:

In one embodiment, the predetermined packing density of array30,FIGS. 4 and 5, is configured to be a fraction of the total cross-sectional area of array30occupied by the plurality of hollow fibers32. In this example, the fraction is calculated using equation (1) above. As discussed above, array30may be configured such that the distance between hollow fibers32is less than or substantially equal to the diameter of the hollow fibers32. In this case, the calculated fraction using equation (1) above is approximately 0.22. In another example, when the spacing between the plurality of hollow fibers32is approximately one half of the diameter for each of the plurality of hollow fibers, the calculated fraction is about 0.40. In another example, there may be zero spacing between the plurality of hollow fibers, e.g., as shown inFIG. 5, a true hexagonal closely packed arrangement. In this example the calculated fraction is about 0.90.

In another example, the density of hollow fibers32of array30may be greater than or equal to about 7.2 fibers/mm2. In one example, the calculation for a density of 7.2 fibers/mm2is discussed below with reference toFIG. 6. In this design, array of hollow fibers32includes seven fibers,60,62,64,66,68, and70arranged in a hexagonal configuration with fiber72in the center. In one example, the diameter, d, for each of fibers60-72is about 0.2 mm, exemplary indicated by d-74for fiber72. As known by those skilled in the art, the area of hexagon76is computed by the following formula:
A=(1.5√{square root over (3)})*t2(2)
where t is equal to the length of the sides of hexagon76, e.g., indicated by t-78. The length t is equal to twice the diameter, (2d), of a hollow fiber, e.g., indicated at77. Thus, equation (1) now becomes:
A=1.5√{square root over (3)}*(2d)2˜=2.6*(2d)2(3)
which equals:
A=6√{square root over (3)}*(2d)2˜=10.4*d2(4)
As shown inFIG. 6, there are 3 fibers of diameter d in the area79of hexagon76, that are no larger than 10.4d2. That is, each of the six hollow fibers60-70includes ⅓ of the area of a hollow fiber totaling2hollow fibers plus hollow fiber72in the center. This results in a density of no less than:

Density⁢⁢of⁢⁢hollow⁢⁢Fibers⁢⁢of⁢⁢array⁢⁢3⁢⁢⁢⁢3(10.4)*(0.2⁢⁢mm)2⁢⁢fibers⁢/⁢mm2(5)
which equals 7.2 fibers/mm2. The size of hollow fibers32and distance therebetween may be even smaller than 0.2 mm so the density of hollow fibers32of array30may be even higher. The increased density of the hollow fibers of the array of one or more embodiments of this invention provides an approximately hexagonally closely packed arrangement of the hollow fibers. The result is array30more efficiently oxygenates a fluid than the conventional oxygenators or similar type devices.

FIG. 7shows one example of array30having a plurality of fibers32having the increased packing density as discussed above with reference to one or more ofFIGS. 4-6. In this example, array30,FIG. 7, is configured to receive gas flow80, e.g., ambient air, an oxygen gas, or any gas having oxygen therein, and a flow of fluid82, e.g., blood or plasma or similar type physiological fluid, or an organic or inorganic fluid, and is designed to transfer the oxygen in gas80to fluid82and/or transfer carbon dioxide in fluid82to gas80.

In one example, array30,FIG. 8may include end-headers90A,90B, and one or more mid-headers, e.g., mid-headers92A,92B . . .92N, which align hollow fibers32in the closely packed configuration with increased density discussed above with reference toFIG. 4. End-headers90A,90B,FIG. 8, and mid-headers92A,92B . . .92N include recesses94,96, respectively, which preferably align hollow fibers32of array30such that the distance between hollow fibers32is smaller than or equal to the diameter of fibers, as discussed above with reference toFIG. 4.

One method for manufacturing the array30of hollow fibers32uses end-headers90A,90B,FIG. 8, and one or more mid-headers92A,92B . . .92N. In one example, a biocompatible adhesive is dispensed to side95of end-header90A. Layer of hollow fibers32A is then fitted into recesses94. The biocompatible adhesive is then applied to side98of mid-header92A. Recesses96of mid-header92A are fitted over layer of hollow fibers32A already fitted into recesses94of end-header90A. Mid-header92A is then pressed to contact end-header90A and sandwich layer of hollow fibers32A therebetween. Next, adhesive is applied to the side100of mid-header92A and layer of hollow fibers32B is fitted into recesses96. Adhesive is applied to the next mid-header, e.g., side102mid-header92B and it is pressed to contact and mid-header92A and sandwich layer of hollow fibers32B therebetween. Adhesive is applied to side104of mid-header92B and layer of hollow fibers32C and is fitted into the recess96of mid-header92B. The process of adding mid-headers and layers of hollow fibers32is repeated until the desired number of layers of hollow fibers32is achieved, e.g., about twenty-five to thirty-five layers. Then adhesive is applied to end-header90B and it is pressed to contact the last mid-header and sandwich hollow fibers32N therebetween. The adhesive is then allowed to cure to complete the process.

Another method for manufacturing an array30,FIG. 4of hollow fibers32, may include system340,FIG. 9. In this example, the method is semi-automated to allow for repeatable application of a uniform amount of the biocompatible adhesive and alignment each layer of the hollow fibers such that the spacing therebetween remains relatively constant.

System340,FIG. 9, includes array manufacturing device342. Device342includes base or bed344with sides346. Sides346have a height, H-348, which is approximately equal to the final height of the array, typically 8 to 15 mm. H-348is approximately equal to height of about twenty-five to thirty-five stacked layers of hollow fibers32for a typical array being manufactured, e.g., as shown inFIG. 7. System340also includes adhesive applicator356. Applicator356includes opposing arms359with blades362therebetween. Arms369are pivotably attached to sides346of device342, e.g., with hinge355. Blades362,FIG. 10, each preferably include contact surface366.

System340,FIG. 9, also includes a plurality of layers of hollow fibers32, e.g., about twenty-five to thirty-five layers of hollow fibers32, although any number of layers of hollow fibers32may be used depending on the size of the array of hollow fibers needed. Hollow fibers32,FIG. 9, are commercially available from, e.g., Dainippon Ink and Chemical Inc. (DIC), Japan. System340also includes a plurality of shims372. Each of shims372is typically as thick as each layer of hollow fibers32, e.g., about 0.2 mm. Each of shims372is sized to fit into bed344. System340also preferably include smooth roller374.FIG. 11shows are more detailed view of device342with adhesive applicator356, shims372, and one layer of hollow fibers32.

One example of the method of manufacturing an array of hollow fibers in accordance with this invention is discussed below with reference toFIGS. 9-18. In this example, plurality of shims372,FIGS. 9 and 11, are placed into bed344of device342, step380,FIG. 12. Preferably, a sufficient number of shims is used such that top shim386is coplanar with top surface369of sides346. Next, adhesive382, e.g., Silastic® silicone adhesive (Dow Corning), is applied to contact surface366on blades362, step384. Adhesive applicator356is then lowered such that contact surface366with adhesive382thereon contacts top shim386, step390,FIG. 13. This applies adhesive382in the shape of blades to top shim386.

Applicator356is then raised and a layer of hollow fibers32is placed over top shim386, step392,FIG. 14.FIG. 15shows an example of layer of hollow fibers32in place over adhesive382. Adhesive382is then rolled away from the center portion390of hollow fibers32using roller374,FIG. 9, step394,FIG. 15. Step394preferably includes spreading adhesive382outwards and away from center area390, e.g., the direction shown by arrows393,395.

Next, one of the plurality of shims372, e.g., bottom shim400,FIGS. 9 and 15, is removed from bed344,FIG. 9in step402,FIG. 15. This causes the top of array30of hollow fibers32being manufactured to stay at the same height, e.g., H-348,FIG. 9, as each new layer of hollow fibers32is added. Then, adhesive382,FIG. 12, is again applied to contact surface366on blades362. Another layer of hollow fibers32is placed over top shim386. Adhesive applicator356is then lower in position over the next layer of hollow fibers32, step404,FIG. 16. Step394(rolling the adhesive) is then repeated. Steps384and steps392through404are repeated as many times as needed until an array with the desired numbers of layers of hollow fibers is formed, e.g. about twenty-five to thirty-five layers. After the array of hollow fibers is complete, the adhesive is allowed to cure. Excess adhesive406, e.g.,FIGS. 17a-17bis then trimmed, as shown inFIGS. 18a-18b.

Although as discussed above with reference toFIGS. 9-18b, adhesive applicator with blades362has a shape resembling a lung, this is not a necessary limitation of this invention. In other designs, adhesive applicator with blades362may have any shape known to those skilled in the art to form an array of hollow fibers of any various shape.

In another embodiment, system340,FIG. 19includes a plurality of smaller shims420,FIG. 19, having a length L-430approximately equal to length L-342of sides346. In one example, plurality of shims420may be placed in two stacks422and424. Then, one shim from each stack of shims422,424, e.g., top shim430is placed against opposing sides346in bed344, step432,FIG. 20. A layer of hollow fibers is then placed between the opposing shims. Adhesive382,FIG. 12, is applied to contact surface366on blades362, similar to step384,FIG. 12. Applicator356is then lowered over the co-planar layer of opposing shims and layer of hollow fibers32therebetween to apply adhesive382to the shims and layer of hollow fibers. Applicator356is then raised. Adhesive382is then rolled away from the center portion of the layer of hollow fibers using roller374,FIG. 9, similar to step394,FIG. 15. Roller374uniformly distributes the adhesive over the increasing height of the array using the two opposing sets of opposing shims against sides346as support. As the array of hollow fibers32forms with each new layer of fibers, the adding of the opposing layers of shims allows for the rolling height to stay relatively constant. After the array is completed, it is then cut along the adhesive to a desired shape, similar as discussed above with reference toFIGS. 17 and 18.

Although, as discussed above with reference toFIGS. 8-20, the steps of manufacturing various embodiments of array30of hollow fibers32may be depicted in a certain order, this is not a necessary limitation of this invention, as the steps of manufacturing array30may be performed in one or more different orders as known by those skilled in the art. Additionally, the adhesive applicator need not necessarily be pivotably attached to the base. In this design, the adhesive applicator vertically descends and is receivable in the bed or base such that the adhesive applicator with adhesive thereon applies adhesive to the appropriate places to the fibers, similar as discussed above.