Method and apparatus for microfiber capture

Abstract

A microplastic collection device includes a plurality of branches that are connected to form a spherical cage. Openings are formed in between the plurality of branches, where the openings are sized to receive microfibers such that the microfibers collect within the spherical cage. The device also includes a housing sized to receive the plurality of branches.

Description

METHOD AND APPARATUS FOR MICROFIBER CAPTURECROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the priority benefit of U.S. Provisional Patent App. No. 63 / 570,052 filed on March 26, 2024, the entire disclosure of which is incorporated by reference herein.BACKGROUND

[0002] Microplastics represent a severe pollution hazard to living organisms and the environment. Microfibers are a common type of microplastic. Due to the increased use of synthetic textiles, release of microfibers into the environment has grown exponentially. Primary sources of microfibers to the environment include the textile and tire industries, the fragmentation of large plastics, and the largest source - domestic laundering. It is anticipated that, to date, 1.5 million trillion microfibers are present in the oceans. These microfibers are mistakenly ingested by marine animals and cause hazardous effects to aquatic ecosystems and the food chain. Due to the unique characteristics of these fibers, it is difficult to filter the fibers out of waterways. At the micron scale and in biomedical applications, it is also difficult to filter these fibers out of bodily fluids and pharmaceutical solutions.SUMMARY

[0003] An illustrative microplastic collection device includes a plurality of branches that are connected to form a spherical cage. Openings are formed in between the plurality of branches, where the openings are sized to receive microfibers such that the microfibers collect within the spherical cage. The device also includes a housing sized to receive the plurality of branches.

[0004] In one embodiment, the plurality of branches is connected to one another at a top pole of the device and at a bottom pole of the device. In another embodiment, the device has a center branch that extends at least from the top pole to the bottom pole. In one embodiment, one or more surface textures are formed on each branch in the plurality of branches. In one embodiment, the one or more surface textures comprise conical barbs. In another embodiment, the one or more surface textures comprise bumps or grooves. In some embodiments, the one or more surface textures are positioned internally on the plurality of branches such that the one or more surface textures are within the spherical cage. In otherembodiments, the one or more surface textures are positioned externally on the plurality of branches such that the one or more surface textures are on an outside of the spherical cage. In another embodiment, the one or more surface textures are positioned only on a lower half of the plurality of branches.

[0005] In an illustrative embodiment, the housing has a square, rectangular, circular, or hexagonal cross-section. In another embodiment, a plurality of housings is positioned adjacent to one another, where each housing in the plurality of housings includes one or more microplastic collection devices. In some embodiments, the housing is sized to receive a plurality of microplastic collection devices that are connected to one another. In another embodiment, first ends of the plurality' of branches are connected to one another to form a pole, and second ends of the plurality of branches are spaced apart to form an opening in the microplastic collection device. In another embodiment, the plurality of branches includes a first plurality of branches that forms a bottom of the device and a second plurality of branches that forms a cover of the device such that the cover removably mounts to the bottom of the device.

[0006] An illustrative method of making a microplastic collection device includes connecting a plurality of branches to form a spherical cage by 3D-printing in one embodiment. The plurality of branches is connected such that openings are formed in between the branches, where the openings are sized to receive microfibers such that the microfibers collect within the spherical cage. The method also includes positioning the spherical cage w ithin a housing that is sized to fit the plurality of branches.

[0007] In one embodiment, connecting the plurality of branches includes connecting first ends of the branches to form a top pole of the device and connecting second ends of the branches to form a bottom pole of the device. In another embodiment, the method includes mounting the plurality of branches to a center branch that extends through the spherical cage. In one embodiment, the method includes applying one or more surface textures on each branch in the plurality of branches. The method can also include mounting the housing to a plurality of other housings, where each housing in the plurality of other housings includes one or more microfiber collection devices. In another embodiment, the connecting comprises connecting first ends of the plurality of branches to one another to form a pole, and further including forming an opening in the spherical cage by spacing apart second ends of the plurality' of branches.

[0008] Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Illustrative embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like numerals denote like elements.

[0010] Fig. 1 depicts a microfiber collection device in accordance with an illustrative embodiment.

[0011] Fig. 2A depicts an oblique view of cages with 2 branches, 6 branches, 10 branches, 14 branches, and 18 branches in accordance with an illustrative embodiment.

[0012] Fig. 2B depicts an oblique view of cages with branch diameters of 0.7 millimeters (mm), 1 mm, 1.3 mm, 1.6 mm, and 1.9 mm in accordance with an illustrative embodiment.

[0013] Fig. 2C depicts an oblique view of cages with different outer diameters of 1 centimeter (cm), 1.5 cm, 2 cm. 2.5 cm, and 3 cm in accordance with an illustrative embodiment.

[0014] Fig. 2D depicts an oblique view of cages with special surface textures including bumps mounted on branches internal to the cage, bumps mounted on branches external to the cage, grooves formed on branches internal to the cage, grooves formed on branches external to the cage, bumps mounted on branches external to the cage and grooves formed on branches internal to the cage, and bumps mounted on branches internal to the cage and grooves formed on branches external to the cage in accordance with an illustrative embodiment.

[0015] Fig. 3A depicts a model developed with ANSYS to simulate the flow behavior around and in the basic design of a spherical cage in accordance with an illustrative embodiment.

[0016] Fig. 3B is a cross-sectional view of the simulation model illustrating the mesh structure utilized in the simulation in accordance with an illustrative embodiment.

[0017] Fig. 3C depicts a simulation demonstrated with streamlines indicating a rotationally induced vortex with a downward velocity in accordance with an illustrative embodiment.

[0018] Fig. 3D depicts a map with velocity vectors demonstrating the direction of the different velocities occurring in and around the cage in accordance with an illustrative embodiment.

[0019] Fig. 3E depicts the cage geometry bisected horizontally by a plane 2 that includes an imaginary line 1 (see Fig. 3A) in accordance wi th an illustrative embodiment.

[0020] Fig. 3F depicts the cage geometry bisected horizontally by a plane 3 that includes an imaginary line 2 (see Fig. 3A) in accordance with an illustrative embodiment.

[0021] Fig. 4A depicts collection results of a cage with 6 branches at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment.

[0022] Fig. 4B depicts collection results of a cage with 10 branches at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment.

[0023] Fig. 4C depicts collection results of a cage with 18 branches at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment.

[0024] Fig. 4D depicts collection results of a cage with bumps mounted internal to the cage at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment.

[0025] Fig. 4E depicts collection results of a cage with bumps mounted external to the cage at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment.

[0026] Fig. 4F depicts collection results of a rod without branches at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment.

[0027] Fig. 5A depicts that the microfiber capture efficiency increases over time in accordance with an illustrative embodiment.

[0028] Fig. 5B depicts that the microfiber capture efficiency increases with increasing branch number (of the cage) and peaks at 18 branches in accordance with an illustrative embodiment.

[0029] Fig. 6A depicts that a combination of microfibers and microscale reflective particles were collected using a cage with a higher number of branches in accordance with an illustrative embodiment

[0030] Fig. 6B depicts the use of a cage to collect microplastic beads made from Delrin® acetal resin in accordance with an illustrative embodiment.

[0031] Fig. 6C depicts the use of a cage to collect polydimethylsiloxane (PDMS) cubes in accordance with an illustrative embodiment.

[0032] Fig. 7A depicts cages with an open end (top) at openness angles of 30°, 60°, and 90° relative to a center of the center rod in accordance with an illustrative embodiment.

[0033] Fig. 7B depicts cages with an open end at varying openness angles and also including appropriately sized covers (i.e., corresponding to the vary ing openness angles) that mount to a center rod of the cage in accordance with an illustrative embodiment.

[0034] Fig. 8A depicts microfiber collection results at t = 0.5 minutes, t = 1 minute, t = 5 minutes, and t = 10 minutes for a cage with an open top and also shows use of a tool (e.g., tweezers) to remove accumulated fibers once the cage is removed from the flow in accordance with an illustrative embodiment.

[0035] Fig. 8B depicts microfiber collection results at t = 0.5 minutes, t = 1 minute, t = 5 minutes, and t = 10 minutes for a two-piece cage with an open top and cover and also shows opening of the two-piece cage to facilitate removal of accumulated fibers once the cage is removed from the flow in accordance with an illustrative embodiment.

[0036] Fig. 9A depicts cages chained vertically to form a multi-cage microfiber capture device in accordance with an illustrative embodiment.

[0037] Fig. 9B depicts cages chained horizontally to form a multi-cage microfiber capture device in accordance with an illustrative embodiment.

[0038] Fig. 10A depicts an experimental setup in which the cage is placed in a cubic housing for microfiber collection in accordance with an illustrative embodiment.

[0039] Fig. 10B depicts a cylindrical housing, a honeycomb-shaped (hexagonal cross- sectional prism) housing, and a spherical housing that can be used to house one or more cages in accordance with an illustrative embodiment.

[0040] Fig. 10C depicts various cage / housing designs for a cubic / rectangular housing in accordance with an illustrative embodiment.

[0041] Fig. 10D depicts multi -housing arrangements (rectangular housings and hexagonal housings with various ratios between the height and the length of the bottom edge) in accordance with an illustrative embodiment.

[0042] Fig. 11A includes images of the capturing process of a cage in a cubic container over the span of five minutes, highlighting the capturing ability of the system in accordance with an illustrative embodiment.

[0043] Fig. 1 IB is a plot depicting that more and more fibers are captured over time such that the fiber amount in the liquid flow and rate of fibers collected reduces over time in accordance with an illustrative embodiment.

[0044] Fig. 12A depicts that when multiple cycles of microfiber collection are performed using a cage system, the number of fibers captured each cycle decreases in accordance with an illustrative embodiment.

[0045] Fig. 12B shows that, with multiple microfiber collection cycles, the overall mass of fibers in water decreases sharply over time as compared to use of a single cycle for the same total time in accordance with an illustrative embodiment.

[0046] Fig. 13A (top row) depicts a cage during a microfiber capturing process over a five-minute span (front view) in accordance with an illustrative embodiment.

[0047] Fig. 13B includes top views of the cage to better show the accumulation of fibers and how the mass grows over time into a spider web-like structure in accordance with an illustrative embodiment.

[0048] Fig. 14A depicts results of different overall cage diameters in accordance with an illustrative embodiment.

[0049] Fig. 14B depicts results of using cages with different numbers of branches in accordance with an illustrative embodiment.

[0050] Fig. 14C depicts results of using cages with different branch diameters in accordance with an illustrative embodiment.

[0051] Fig. 15A depicts microfiber collection over 5 minutes with a basic cage design, with a cage design having a 90° region of internal barbs in the lower portion of the cage, and with a cage design having a 180° region of internal barbs in the lower portion of the cage in accordance with an illustrative embodiment.

[0052] Fig. 15B depicts the mass of fibers captured over time were plotted for all three designs of Fig. 15A placed in a cubic container in accordance with an illustrative embodiment.

[0053] Fig. 16A depicts the basic cage tool after five minutes of capture for a range of concentrations of short and long fibers in accordance with an illustrative embodiment.

[0054] Fig. 16B depicts a plot of performance of the cage tool placed in a cubic container for the different concentrations in accordance with an illustrative embodiment.

[0055] Fig. 17A includes images that were taken of the cage over the span of five minutes for several flow speeds in accordance with an illustrative embodiment.

[0056] Fig. 17B is a plot depicting the performance of the cage tool placed in a cubic container for two different total capture times for several different flow speeds in accordance with an illustrative embodiment.

[0057] Fig. 18A is a chart that depicts different boundary conditions that were tested by altering the cubic housing size in accordance with an illustrative embodiment.

[0058] Fig. 18B is a plot depicting the mass of fibers collected for the basic cage tool for different cubic housing sizes in accordance with an illustrative embodiment.

[0059] Fig. 18C is a plot of the capture efficiency for the different cubic housing sizes in accordance with an illustrative embodiment.

[0060] Fig. 19A is an image of the cage tool capturing microfibers and glitter in accordance with an illustrative embodiment.

[0061] Fig. 19B depicts the cage tool capturing only glitter in accordance with an illustrative embodiment.

[0062] Fig. 19C depicts the cage tool capturing microfibers, glitter, and PLA microfibers in accordance with an illustrative embodiment.

[0063] Fig. 19D is a plot depicting the mass of microplastics and microfibers collected in the experiments by the cage tool placed in a cubic container in accordance with an illustrative embodiment.

[0064] Fig. 20A depicts the capturing process of the basic cage tool in brackish water (3.5 wt.% NaCl) in accordance with an illustrative embodiment.

[0065] Fig. 20B depicts that salt (sodium chloride) from the w ater can also be trapped and collected in the fibers upon drying in accordance with an illustrative embodiment.

[0066] Fig. 21A depicts shaking and / or rotation of the cage tool to release collected microplastics from the tool for disposal into a designated wastewater container in accordance with an illustrative embodiment.

[0067] Fig. 2 IB is a plot depicting the releasing time needed for various mass of fibers captured in the cage tool placed in a cubic container in accordance with an illustrative embodiment.DETAILED DESCRIPTION

[0068] Microplastics are every where and are especially present in large bodies of water as a result of waste and the breaking dow n or shedding of larger plastics. Microfibers are a common type of microplastics. Many industries, including synthetic textiles and tires, generate high volumes of microfibers daily. Microfibers are also found in wastewater from homes as a result of washing polyester garments and plastic kitchen essentials. Exposure to these microfibers can be detrimental to the ecosystem and to human health. The buildup of microfibers in humans is associated with a myriad of diseases, and a method to remove these microplastics before consumption (and / or from bodily fluid), may reduce the associated risk.

[0069] There are several methods to capture and remove microfibers from an aqueous environment, however traditional removal methods have disadvantages such as a difficult and time-consuming removal process of the microfibers after capture. Traditional microfiber capture systems also cannot support a wide range of dimensions of microfibers, and are required to be included with fabrics while washing. Human actions can greatly impact the efficacy of these devices, therefore it is important to create a device that is cost-effective and convenient for a consumer to use. The proposed design utilizes a cage-like geometry composed of multiple branches to effectively and efficiently capture microfibers in a rotational or other flow of water. The branches have an increased effective contact area, induced by the geometry, as well as an open middle allowing for fibers to collect, which facilitates the fiber capture process. This system has applications for an improved removal process and scalability to support a wade range of microplastic geometries and materials. The proposed system can be used to generate filters in products like washing machines, w ater tanks, bathtubs, water pipes, and their accessories upon manufacturing.

[0070] As discussed above, the current attempts to remove microfibers from the environment have various disadvantages. For example, the meshes used are frequently clogged, and require energy and funds for maintenance. In traditional systems, membrane filtration is size based, and the microplastics may be on the same scale as or larger than the necessary solutes. Additionally, removal of the fibers after capture is typically cumbersome and time consuming. Therefore, there is a need for an effective and efficient way to capture and remove microfibers. This technology can be used in oceans, lakes, rivers, and wastewater treatment, and can also be used for the filtration of solutions and bodily fluids in biomedical applications.

[0071] Capture of microfibers has been a growing area of research due to the toxic effect they can impose both directly and indirectly to all life forms. Traditionally, methods used to capture these fibers include mesh filters, which typically are clogged as a result of aggregated fibers. Filter replacement cycles are therefore shortened, and more energy and funds must be expended for maintenance. In drum devices (washing machines), external filters are used to collect fibers that shed from fabrics during a wash cycle, but it is difficult to remove the fibers from the filters after collection. Membrane filters are used in most biomedical applications, but the diffusion of microfibers is limited due to their size. Proposed herein is a design using a cage composed of branches. Manipulating the surface characteristics and geometry of the cages via low cost and widely available methods results in a wide array of devices to capture microplastics in aquatic environments.

[0072] In an illustrative embodiment, the proposed system takes advantage of a rotational flow behavior, and a basic design of a spherical cage geometry was designed with branch-like protrusions, referred to as "‘branches.” In some embodiments, first ends of the branches connect to one another to form a top pole of the spherical cage and second ends of the branches connect to one another to form a bottom pole of the spherical cage. In one embodiment, a cage can have n number of branches with a branch diameter d and an overall cage diameter D. Fig. 1 depicts a microfiber collection device in accordance with an illustrative embodiment. In the embodiment of Fig. 1, the cage has 14 branches that connect to one another at both a top pole and a bottom pole of the cage. As discussed below, additional or fewer branches may be used in alternative embodiments.

[0073] The number of branches, branch diameter, and overall cage diameter of the microfiber collection device can all be varied. In some embodiments, surface texture can alsobe added to the branches to increase contact area between the fibers and branches. Fig. 2A depicts an oblique view of cages with 2 branches, 6 branches. 10 branches, 14 branches, and 18 branches in accordance with an illustrative embodiment. Fig. 2B depicts an oblique view of cages with branch diameters of 0.7 millimeters (mm), 1 mm, 1.3 mm, 1.6 mm, and 1.9 mm in accordance with an illustrative embodiment. Fig. 2C depicts an oblique view' of cages with different outer diameters of 1 centimeter (cm), 1.5 cm, 2 cm, 2.5 cm, and 3 cm in accordance with an illustrative embodiment. Fig. 2D depicts an oblique view of cages with special surface textures including bumps mounted on branches internal to the cage, bumps mounted on branches external to the cage, grooves formed on branches internal to the cage, grooves formed on branches external to the cage, bumps mounted on branches external to the cage and grooves formed on branches internal to the cage, and bumps mounted on branches internal to the cage and grooves formed on branches external to the cage in accordance with an illustrative embodiment.

[0074] These surface textures varying in size and spacing can be easily added when designing the cage using computer aided design. Three-dimensional (3D) printing using vat photopolymerization allows for small-scale features, like surface texture, to be reliably printed. It is noted that the method to create these textures are not limited to 3D printing, for example, bumps can also be generated by attaching beads and grooves can be simply cut. The embodiments of Fig. 2 are illustrative, and in alternative embodiments a different number of branches, branch diameter, overall diameter, and position / type of surface texture may be used. In general, more fibers are captured by entering the cage, barring significant obstructions. Since the number of branches, geometry, and surface texture determine the quantity of microfibers captured by the cage, the inventors have compared the effectiveness of various number of branches, diameters for the branches, cage diameter, and branch surface textures.

[0075] Fig. 3A depicts a model developed with ANSYS to simulate the flow behavior around and in the basic design of a spherical cage in accordance with an illustrative embodiment. Fig. 3B is a cross-sectional view- of the simulation model illustrating the mesh structure utilized in the simulation in accordance with an illustrative embodiment. As shown, the cage is positioned within a cylindrical housing though which a liquid flow' can be directed. In alternative embodiments, a different housing shape may be used. Fig. 3C depicts a simulation demonstrated with streamlines indicating a rotationally induced vortex with a downw ard velocity in accordance with an illustrative embodiment. Fig. 3D depicts a mapwith velocity vectors demonstrating the direction of the different velocities occurring in and around the cage in accordance with an illustrative embodiment. To further understand the flow behavior within different planes of the geometry, imaginary lines were created to examine the streamlines of their respective planes. Fig. 3E depicts the cage geometry bisected horizontally by a plane 2 that includes an imaginary line 1 (see Fig. 3 A) in accordance with an illustrative embodiment. Fig. 3F depicts the cage geometry bisected horizontally by a plane 3 that includes an imaginary line 2 (see Fig. 3A) in accordance with an illustrative embodiment. Figs. 3E and 3F include top and front views. As shown in Fig. 3E, streamlines passing through plane 2 show no entrance into the cage implying little to no capture of fibers. However, streamlines passing through plane 3 in Fig. 3F show the flow entering the cage, implying higher capture capabilities due to the potential for greater interaction with the branches and as a result of the flow remaining within the cage for a period of time.

[0076] A capture process experiment was performed using the experimental setup of Fig. 3. Due to the material density of the microfibers, gravitational effects can be ignored because the Bond number, a dimensionless number measuring the importance of gravitational forces compared to surface tension forces for the movement of a liquid front, is much less than one. In one embodiment, the spherical cages described herein can be formed via 3D printing using any appropriate materials such as commercial UV-curable resin. Alternatively, the spherical cages may be molded or formed using a different technique. For example, metal spherical cages can be created by direct metal laser sintering (DLMS). The branches of the plastic spherical cage can be formed from using UV-curable resin and a 3D printer in one embodiment. 3D pnnted spherical cages and 3D printed rods have the ability to collect microfibers, but it was seen from experiments that spherical cages collect significantly larger quantities of microfibers than rods under equivalent conditions. The number of branches were varied for the spherical cages and tested for collection over the duration of five minutes. Texture in the form of bumps were also added during the printing process to the inside or outside of the branches and showed capturing abilities.

[0077] Fig. 4A depicts collection results of a cage with 6 branches at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment. Fig. 4B depicts collection results of a cage with 10 branches at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment. Fig. 4C depicts collection results of a cage with 18 branches at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment. Fig. 4D depicts collection results of a cage with bumps mountedinternal to the cage at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment. Fig. 4E depicts collection results of a cage with bumps mounted external to the cage at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment. Fig. 4F depicts collection results of a rod without branches at t = 0.5 minutes, t = 1 minute, and t = 5 minutes in accordance with an illustrative embodiment.

[0078] Based on the experiments, it was found that the capture efficiency, defined as the mass of captured fibers over the total mass of fibers, increases over time and has a positive trend with increasing branch number. Fig. 5A depicts that the microfiber capture efficiency increases over time in accordance with an illustrative embodiment. Fig. 5B depicts that the microfiber capture efficiency increases with increasing branch number (of the cage) in accordance with an illustrative embodiment. In the embodiments of Figs. 5A and 5B, the cage is placed in a cylindrical container / housing. However, it was found that the capture efficiency peaks at eighteen branches and a negative trend is observed for larger branch numbers. This is related to the openness of the cage, where an optimal number of branches with optimal branch and cage diameters results in the peak capture efficiency.

[0079] Other geometries and plastic materials were collected using the 3D printed spherical cages. Fig. 6A depicts that a combination of microfibers and microscale reflective particles were collected using a cage with a higher number of branches in accordance with an illustrative embodiment. With this same geometry, microplastic beads made from Delrin® acetal resin and poly dimethylsiloxane cubes were also collected. Fig. 6B depicts the use of a cage to collect microplastic beads made from Delrin® acetal resin in accordance with an illustrative embodiment. Fig. 6C depicts the use of a cage to collect poly dimethylsiloxane cubes in accordance with an illustrative embodiment. The 3D printed spherical cages therefore show capabilities for a wide range of microplastic geometries and material capture.

[0080] Upgraded cage designs were also generated with the removal of the microfibers in mind. One of the designs has a center rod, and an open top at varying angles relative to a center of the center rod. In one embodiment, center rods are used in cages that do not have a closed top otherwise, and the rod is attached at the top pole of the cage to aid in mounting of the technology. Fig. 7A depicts cages with an open end (top) at openness angles of 30°, 60°, and 90° relative to a center of the center rod in accordance with an illustrative embodiment. Another design has an open-end (similar to the embodiments of Fig. 7A). but also includes a cover that can attach and detach to a center rod of the cage. Fig. 7B depicts cages with anopen end at varying openness angles and also including appropriately sized covers (i.e., corresponding to the varying openness angles) that mount to a center rod of the cage in accordance with an illustrative embodiment. In one embodiment, the cover includes a central opening that is sized to receive the central rod of the cage such that the cover mounts to the cage. The two halves can simply be attached by press fitting them together. The branches press on the inside of the cover, providing a stable mechanical fit.

[0081] Both of the designs of Fig. 7 (i.e. open top with and without a mountable cover) aid in the removal process by allowing for microfibers to be easily removed by tweezers or one’s own fingers. Fig. 8A depicts microfiber collection results at t = 0.5 minutes, t = 1 minute, t = 5 minutes, and t = 10 minutes for a cage with an open top and also shows use of a tool (e.g., tweezers) to remove accumulated fibers once the cage is removed from the flow in accordance with an illustrative embodiment. As shown, the tweezers are used to remove the collected microfibers though the opening at the top (or bottom) of the cage. Fig. 8B depicts microfiber collection results at t = 0.5 minutes, t = 1 minute, t = 5 minutes, and t = 10 minutes for a two-piece cage with an open top and cover and also shows opening of the two-piece cage to facilitate removal of accumulated fibers once the cage is removed from the flow in accordance with an illustrative embodiment.

[0082] The basic design of the spherical cage can be used as a unit to easily scale up the system. Scalability is necessary for the technology to be used commercially and in households because these are much larger scales than what is done experimentally. The basic cage design can be chained in vertical or horizontal units to form multi-cage microfiber capture devices. This provides different configurations the cages could be used for scaling up to larger container sizes or increase the mass of fibers collected by having more cages able to capture microfibers. Fig. 9A depicts cages chained vertically to form a multi-cage microfiber capture device in accordance with an illustrative embodiment. As shown, the cages are connected at poles (i.e., a bottom pole of the upper cage attaches to the top pole of the lower cage). Multiple cages can be generated by either glueing individual cages together or directly 3D printing several units. Fig. 9B depicts cages placed horizontally to form a multi-cage microfiber capture device in accordance with an illustrative embodiment. While Figs. 9A and 9B depict only 2-3 cages chained together, it is to be understood that additional cages may be used in alternative embodiments, such as 4, 5, 10, 25, etc. Based on experiments, both configurations show collection would occur in all units.

[0083] As shown in Fig. 10, the cage tool described herein can be used in conjunction with different container / housing shapes and sizes (i.e., not just cylindrical). Fig. 10A depicts an experimental setup in which the cage is placed in a cubic housing for microfiber collection in accordance with an illustrative embodiment. The experiments conducted in the cubic housing are similar to those conducted in a cylindrical container, as discussed above. Fig. 10B depicts a cylindrical housing, a honeycomb-shaped (hexagonal cross-sectional prism) housing, and a spherical housing that can be used to house one or more cages in accordance with an illustrative embodiment. In alternative embodiments, other shapes / sizes may be used. Due to the convenience of fabrication of the tool, it can have various geometric parameters depending on those of the container / housing. Fig. 10C depicts various cage / housing designs for a cubic / rectangular housing in accordance with an illustrative embodiment. In an illustrative embodiment, the shortest length of the container / housing (a, b, h) limits the longest length the tool can have (D) in that direction. In another illustrative embodiment, the system can easily be scaled up by using multiple housings, each of which can include or more cages to collect microfibers from a contaminated liquid. Fig. 10D depicts multi-housing arrangements (rectangular housings and hexagonal housings with various ratios between the height and the length of the bottom edge) in accordance with an illustrative embodiment. As discussed, in alternative embodiments, different housing shapes may be used, such as cylindrical, spherical, octagonal, etc. The contaminated liquid can either flow into each container one by one (multi-stage or multi-step treatment), or flow into them at the same time (parallel scaleup), depending on the implementation. Using the embodiment of Fig. 10D, the volume of microfiber contaminated w ater can be scaled up by using larger containers and / or additional containers.

[0084] Fig. 11 depicts the capture process of a spherical cage tool in a cubic container, and indicates that this setup effectively captures microfibers. Fig. 11 A includes images of the capturing process of a cage in a cubic container over the span of five minutes, highlighting the capturing ability of the system in accordance with an illustrative embodiment. Fig. 1 IB is a plot depicting that more and more fibers are captured over time such that the fiber amount in the liquid flow and rate of fibers collected reduces over time in accordance with an illustrative embodiment. In this embodiment, the cage is placed in a cubic container / housing. It is noted that the capture speed decreases over time. In this embodiment, the container size is a = b = h = 9.3 cm and the water volume is 600 mL ( / zwater = 7 cm). The fiber length is about 2 mm, and the diameter is slightly less than 50 pm. The fiber concentration is 0.0083%.The rotational speed of the hot plate is set to 300 rotations per minute (RPM), resulting in the flow entering the tool at a speed of roughly 0. 1 m / s. The outer diameter / ), the branch number M, and the branch diameter d of the cage tool is 20 mm, 18, and 1 mm, respectively. In alternative embodiments, different sizes, rotational speeds, number of branches, etc. may be used. In summary, Fig. 11 shows that over time as more fibers are captured, the amount of fibers in the contaminated water reduces proportionately to what is captured. Additionally, the capture speed decreases over time likely due to the accumulation of more and more fibers on / in the cage.

[0085] The capturing process can be performed in one long cycle, or as multiple short cycles adding up to one long cycle, depending on the implementation. Experiments were performed with the basic design tool and same container size (600 mL). Fig. 12A depicts that when multiple cycles of microfiber collection are performed using a cage system, the number of fibers captured each cycle decreases in accordance with an illustrative embodiment. However, the overall or total amount of fibers captured increases w ith more cycles. Fig. 12B shows that, with multiple microfiber collection cycles, the overall mass of fibers in w ater decreases sharply over time as compared to use of a single cycle for the same total time in accordance with an illustrative embodiment. Therefore, it was found that multiple short cycles remove more fibers in total than a single cycle for the same amount of total time.

[0086] In other words, with multiple cycles the overall number of fibers in the water decreases sharply over time compared to a single cycle for the same total time. For the experiments of Fig. 12, it is noted that the container size is a = b = h = 9.3 cm and the water volume is 600 mL ( / water = 7 cm). The fiber length is about 2 mm, and the diameter is slightly less than 50 pm. The fiber concentration is 0.0083%. The rotational speed of the hot plate is set to 300 RPM, resulting in the flow entering the tool at a speed of roughly 0.1 m / s. The outer diameter D, the branch number n, and the branch diameter d of the cage tool is 20 mm, 18, and 1 mm, respectively. In alternative embodiments, different values may be used for any of the variables in the experiments of Fig. 12.

[0087] The openness of the tool, defined as the space between branches, changes as the capturing process progresses over time. Fig. 13A (top row) depicts a cage during a microfiber capturing process over a five-minute span (front view) in accordance with an illustrative embodiment. Fig. 13A (bottom) shows front views of the empty cage for comparison. As shown, as more microfibers have been captured the openness of the cage decreases. Fig. 13Bincludes top views of the cage to better show the accumulation of fibers and how the mass grows over time into a spider web-like structure in accordance with an illustrative embodiment. The experimental conditions for Fig. 13 are the same as those used (and discussed above) for Fig. 11.

[0088] In an illustrative embodiment, the proposed system (e.g., cage, housing, etc.) can be conveniently designed or redesigned using any computer-aided design software. As such, parameters can be altered to fabricate tools with different geometries. For example, the outer diameter of the tool can be increased or decreased. Fig. 14A depicts results of different overall cage diameters in accordance with an illustrative embodiment. More specifically. Fig. 14A shows the mass of fibers captured for a varying outer diameter of the cage (n = 10 and d = 1 mm). When these cages with different outer diameters were tested, the inventors found an optimal size (40 mm) for a specific cubic container size (inner edge length equals to 9.3 cm and the water volume inside is 600 mL) and fiber length (2 mm) that resulted in optimal fiber capture. Fig. 14B depicts results of using cages with different numbers of branches in accordance with an illustrative embodiment. Specifically, Fig. 14B shows the mass of fibers captured for a given branch number (D = 20 mm and d = 1 mm). The optimal number of branches was found to be n = 18 for a specific container size and fiber length. Fig. 14C depicts results of using cages with different branch diameters in accordance with an illustrative embodiment. In the embodiments of Fig. 14, the cage is placed in a cubic container. As shown, an optimal branch diameter was found to be 1 mm for the same size container and fiber length. The experimental conditions for Fig. 14 are the same as those used (and discussed above) for Fig. 11.

[0089] Using the basic cage design, internal surface texture in the form of barbs were added to the lower pole region of the cage during the 3D printing of the structures. Fig. 15A depicts microfiber collection over 5 minutes with a basic cage design, with a cage design having a 90° region of internal barbs in the lower portion of the cage, and with a cage design having a 180° region of internal barbs in the lower portion of the cage in accordance with an illustrative embodiment. The 90° region is based on a 45° angle that extends downward from a center of the central rod of the cage. Similarly, the 180° region is based on a 90° angle that extends outward from the center of the central rod. As show n, the surface structures are in the shape of cones and have a triangular cross-section. Alternatively, different shapes may be used for the surface structures such as square / cubic. spherical, cylindrical, etc. Additionally, fewer or additional surface structures may be used in alternative embodiments. In oneembodiment, the entire interior and / or exterior of the cage includes surface structures. Fig. 15B depicts the mass of fibers captured over time were plotted for all three designs of Fig. 15A placed in a cubic container in accordance with an illustrative embodiment. The design with more barbs showed higher fiber capture in the initial capturing times. This could be useful if the tool is used for multiple short cycles. The experimental conditions for Fig. 15 are the same as those used (and discussed above) for Fig. 11.

[0090] The concentration of fibers for both short (2 mm) and long (6 mm) fibers were tested using the basic cage design. The cage tool demonstrated that it can be used for a range of microfiber concentrations. Fig. 16A depicts the basic cage tool after five minutes of capture for a range of concentrations of short and long fibers in accordance with an illustrative embodiment. The cage tool being used with short fibers showed an increase in capture as the concentration increased. Fig. 16B depicts a plot of performance of the cage tool placed in a cubic container for the different concentrations in accordance with an illustrative embodiment. For longer fibers, the cage tool showed a relatively constant capture of fibers regardless of the change in concentration. It can also be noted, the capture efficiency decreases as the concentration increases. However, the capture efficiency remains relatively constant for the shorter fibers. The experimental conditions for Fig. 16 are the same as those used (and discussed above) for Fig. 11.

[0091] The proposed cage design can also be used for a range of flow speeds. Fig. 17A includes images that w ere taken of the cage over the span of five minutes for several flow speeds in accordance with an illustrative embodiment. Lower speeds showed caking occurring on the outside of the tool. From this, it was concluded that significant caking occurs at lower flow speeds, while there is significant re-entrainment of the fibers at higher flow speeds. It was also observed that there are higher capture efficiencies as the flow speed increased. This is likely due to increased interaction betw een the cage tool and the fibers. Fig. 17B is a plot depicting the performance of the cage tool placed in a cubic container for two different total capture times for several different flow speeds in accordance with an illustrative embodiment. The expenmental conditions for Fig. 17 are the same as those used (and discussed above) for Fig. 11.

[0092] Using the cage tool in different container / housing shapes and sizes, results in different boundary conditions for the system. For example, using a smaller container relative to the size of the tool, will affect the boundary conditions as the w all of the container willhave more of an effect on the capturing process. Different sizes for a cubic container / housing were tested, although different shapes may be used in alternative embodiments, such as cylindrical, hexagonal, octagonal, etc. More fibers were caught in the larger containers, though this is because there are more fibers in the larger containers in order to have the same concentration amongst all of the containers. In contrast, the capture efficiencies decrease as the container size increases, indicating the boundary conditions influence the performance of the cage tool. Fig. 18A is a chart that depicts different boundary conditions that were tested by altering the cubic housing size in accordance with an illustrative embodiment. Fig. 18B is a plot depicting the mass of fibers collected for the basic cage tool for different cubic housing sizes in accordance with an illustrative embodiment. Fig. 18C is a plot of the capture efficiency for the different cubic housing sizes in accordance with an illustrative embodiment. As discussed above, these results show that as the tank size increases the capture efficiencies decreases. The experimental conditions for Fig. 18 are the same as those used (and discussed above) for Fig. 11.

[0093] The spherical cage design can be used to not only capture fibers but also other types of microplastics. For example, in addition to fibers, the spherical cage was able to catch pieces of glitter and other fibers with different materials (like polylactic acid) and with varying length and width. The cage is also capable of catching pieces of glitter without the presence of fibers in the tool already, but the capture efficiency is low in such a scenario. In one embodiment, the presence of fibers can enhance the capture of other plastics, leading to more than just one specific type of fibers being captured in contaminated aquatic environments. Fig. 19A is an image of the cage tool capturing microfibers and glitter in accordance with an illustrative embodiment. Fig. 19B depicts the cage tool capturing only glitter in accordance with an illustrative embodiment. Fig. 19C depicts the cage tool capturing microfibers, glitter, and PLA microfibers in accordance with an illustrative embodiment. Fig. 19D is a plot depicting the mass of microplastics and microfibers collected in the experiments by the cage tool placed in a cubic container in accordance with an illustrative embodiment. It was found that microfibers can aid in the capture of other contaminants in the aquatic environment, such as other types and sizes of microplastics.

[0094] It is to be understood that the proposed cage tool is not only limited to fresh water like that from rivers and lakes, but it can also be used in brackish water, salt water, biological fluids (e.g.. blood), and other liquids. Experiments were performed in an environment that modeled seawater, and the tool demonstrated good capturing abilities. Salts can remaintrapped and collected in the network of fibers upon drying, indicating the fibers and other soluble containments can be removed from the aquatic environment. Fig. 20 A depicts the capturing process of the basic cage tool in brackish water (3.5 wt.% NaCl) in accordance with an illustrative embodiment. These results indicate that the proposed cage tool can be also applied to a seawater / ocean environment. Fig. 20B depicts that salt from the water can also be trapped and collected in the fibers upon drying in accordance with an illustrative embodiment. The results of Fig. 20B indicate that the fiber together with other soluble contaminants such as inorganic salts, are removed from the aquatic environment.

[0095] Also provided herein are a method and system for removing the fibers from the cage tool for proper disposal. In one embodiment, the cage tool can either be shaken or rotated within an aquatic environment and into a secondary container that collects microplastics released from the device as a result of the shaking / rotation. The time needed to agitate the tool for releasing all of the fibers depends on the mass of fibers collected before renewing. Fig. 21 A depicts shaking and / or rotation of the cage tool to release collected microplastics from the tool for disposal into a designated wastewater container in accordance with an illustrative embodiment. Fig. 21B is a plot depicting the releasing time needed for various mass of fibers captured in the cage tool placed in a cubic container in accordance with an illustrative embodiment. As shown, longer release times may be required for more captured fibers.

[0096] Thus, described herein is a system that utilizes the special geometry of a spherical cage composed of branches to increase the effective contact area between fibers and the capturing tool. In an illustrative embodiment, the proposed tool has an open center for accumulation of fibers after collection. In addition to microfiber collection, this system offers a convenient removal process by allowing fibers to be removed through an open top, or by enabling separation of top and bottom components of the cage such that the microfibers can be directly removed from the center of the device. In summary, the proposed system can capture microplastics of vary ing geometry and material, it is environmentally friendly, low- cost, and easy to manufacture and use. Additionally, microplastics capture performance can be realized independent of the salinity' of the aquatic environments and no external energy is needed to be put into the microplastics capture process.

[0097] The proposed system has a wide range of microplastics capture effect for different geometries and materials. The system also has the advantage of capturing microplasticparticles that may be larger than the size exclusion threshold of traditional membrane filtration systems. In one embodiment, 3D printing can be used to form the system. Three- dimensional printing is an established and commonly-used process in additive manufacturing, resulting in accessible large-scale manufacturing for these cages at lower costs than other methods. The proposed system can be included in a broad range of applications, and can be included in various systems upon manufacturing. For example, the proposed system can be used in home appliances including washing machines and water tanks, plumbing, wastewater treatment facilities, water purifiers for industrial and residential purposes, attachments to faucets for baths and sinks, boats, submarines, ships, etc., hemodialysis treatments, filtering solutions for pharmaceutical development, etc.

[0098] The word "illustrative" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "illustrative" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, "a" or "an" means "one or more.”

[0099] The foregoing description of illustrative embodiments of the invention has been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and as practical applications of the invention to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims

WHAT IS CLAIMED IS:1 . A microplastic collection device comprising: a plurality of branches that are connected to form a spherical cage; openings formed in between the plurality’ of branches, wherein the openings are sized to receive microfibers such that the microfibers collect within the spherical cage; and a housing sized to receive the plurality of branches.

2. The device of claim 1, wherein the plurality of branches is connected to one another at a top pole of the device and at a bottom pole of the device.

3. The device of claim 2, further comprising a center branch that extends at least from the top pole to the bottom pole.

4. The device of claim 1, further comprising one or more surface textures formed on each branch in the plurality’ of branches.

5. The device of claim 4, wherein the one or more surface textures comprise conical barbs.

6. The device of claim 4, wherein the one or more surface textures comprise bumps or grooves.

7. The device of claim 4, wherein the one or more surface textures are positioned internally on the plurality' of branches such that the one or more surface textures are within the spherical cage.

8. The device of claim 4, wherein the one or more surface textures are positioned externally on the plurality of branches such that the one or more surface textures are on an outside of the spherical cage.

9. The device of claim 4, wherein the one or more surface textures are positioned only on a lower half of the plurality’ of branches.

10. The device of claim 1 , wherein the housing has a square, rectangular, or hexagonal cross-section.

11. The device of claim 1 , further comprising a plurality of housings positioned adjacent to one another, wherein each housing in the plurality of housings includes one or more microplastic collection devices.

12. The device of claim 1, wherein the housing is sized to receive a plurality of microplastic collection devices that are connected to one another.

13. The device of claim 1, wherein first ends of the plurality of branches are connected to one another to form a pole, and wherein second ends of the plurality of branches are spaced apart to form an opening in the microplastic collection device.

14. The device of claim 1, wherein the plurality of branches includes a first plurality of branches that forms a bottom of the device and a second plurality7of branches that forms a cover of the device such that the cover removably mounts to the bottom of the device.

15. A method of making a microplastic collection device, the method comprising: connecting a plurality of branches to form a spherical cage; wherein the plurality of branches is connected such that openings are formed in between the branches, wherein the openings are sized to receive microfibers such that the microfibers collect within the spherical cage; and positioning the spherical cage within a housing that is sized to receive the plurality of branches.

16. The method of claim 15, wherein connecting the plurality of branches includes connecting first ends of the branches to form a top pole of the device and connecting second ends of the branches to form a bottom pole of the device.

17. The method of claim 15, further comprising mounting the plurality of branches to a center branch that extends through the spherical cage.

18. The method of claim 15, further comprising applying one or more surface textures on each branch in the plurality of branches.

19. The method of claim 15, further comprising mounting the housing to a plurality7of other housings, wherein each housing in the plurality of other housings includes one or more microplastic collection devices.

20. The method of claim 15, wherein the connecting comprises connecting first ends of the plurality7of branches to one another to form a pole, and further comprising forming an opening in the spherical cage by spacing apart second ends of the plurality of branches.

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