Capillary action-driven microfluidic filter system for body fluid analysis

Abstract

A capillary action-driven microfluidic system for body fluid analysis may include a microneedle device comprising: a microfluidic substrate comprising: an inlet channel configured to drive capillary movement of a fluid across the inlet channel, an outlet channel configured to drive capillary movement of the fluid across the outlet channel; and a crossflow filtration chamber having a crossflow filtration channel in fluidic communication with the inlet channel and the outlet channel, the crossflow filtration chamber configured to drive capillary movement of the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber.

Description

CAPILLARY ACTION-DRIVEN MICROFLUIDIC FILTER SYSTEM FOR BODY FLUID ANALYSISRELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 602,171, filed November 22, 2024, entitled “CAPILLARY-DRIVEN MICROFLUIDIC FILTER SYSTEM FOR BODY FLUID ANALYSIS,” the contents of which is incorporated herein by reference in its entirety.FIELD

[0002] The present application is directed to a capillary action-driven microfluidic filter system for body fluid analysis, e.g., capillary action driven microfluidic platform for simultaneous manipulation and analysis of bodily fluids.BACKGROUND

[0003] Personalized medicine aspires to deliver individualized care to patients by leveraging their genetic, molecular, and clinical data to customize treatment plans, medications, and interventions. As the paradigm shift towards personalized medicine becomes increasingly prominent, individualized diagnostic testing will play an increasingly significant role in alleviating the laborious logistical challenges associated with conventional approaches to collecting and analyzing health care data.

[0004] Particularly, routine blood tests, such as those that perform complete blood counts and metabolic analysis, are central diagnostic testing in the clinical setting. For example, providing a complete blood count, including the number of cells of each type and subtype, facilitates the diagnosis of disorders such as anemia, leukemia, and acute infection, which cause deviations in cell counts from the normal. Likewise, biochemical tests performed on blood plasma have diagnostic utility in the assessment of metabolic disorders, cancer, organ function, nutrition, and more. However, generating personalized data quickly, accurately, and affordably remains a significant hurdle to realizing such possibilities.

[0005] Existing diagnostic platforms fail to reliably collect body fluids, lack sufficient sensitivity to detect target analytes, or require costly peripheral equipment inappropriate for point-of-care use. Therefore, a need exists for an accurate, low-cost, and robust point-of-care platform for the collection of body fluids, such as capillary blood, and the reliable quantization of cells and analytes therein.SUMMARY

[0006] This disclosure is generally directed to a microfluidic filter platform for collecting, filtering, and directing body fluids through microfluidic patterns by capillary action-driven movement so that constituents of the body fluid may be examined. In some implementations, a microneedle may supply the body fluid to the microfluidic pattern, such as through a patch.

[0007] The provided systems and methods are particularly advantageous for blood testing applications. For instance, the microneedle or cartridge may deliver whole blood from a patient to the microfluidic pattern, which in turn directs the flow by capillary action-driven movement. The microfluidic pattern includes a crossflow filtration chamber that may be structured to filter the whole blood on the basis of cellular or biomarker composition, e.g., to separate plasma from red and white blood cells or red and white blood cells from each other. Following the crossflow filtration of the body fluid, cells, biomarkers, and other analytes therewithin may be detected and analyzed.

[0008] In an aspect, the system described herein relates to a microneedle device (e.g., “a bioresorbable thermoplastic microneedle platform"), including a microfluidic substrate. The microfluidic substrate may include an inlet channel, an outlet channel, and a crossflow filtration chamber. The inlet channel may be configured to drive the capillary movement of a fluid (e.g., a body fluid such as blood or environmental fluid) across the inlet channel. The outlet channel may be configured to drive capillary movement of the fluid across the outlet channel. The crossflow filtration chamber may include a crossflow filtration channel in fluidic communication (directly or indirectly) with the inlet channel and the outlet channel and be configured to drive capillary movement of the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber. A collection of structures and channels comprising at least an inlet channel, a crossflow filtration chamber, and an outlet channel may be collectively referred to as a testing channel.

[0009] In some implementations, the microneedle device further includes a microneedle assembly (e.g., having 1 or multiples of microneedles) coupled to the inlet channel, the microneedle assembly having a first hollow microneedle configured to excise the fluid from a tissue once placed at a collection site on a person.

[0010] In some implementations, the microstructure pattern includes spaced-apart filtration structures adjacent to the crossflow filtration channel. Spacings between the filtrationstructures may be smaller than the size of blood cells in the fluid, thereby resisting the capillary movement of the blood cells across the filtration boundary.

[0011] In some implementations, the microstructure pattern further includes spaced-apart capillary pillars, wherein the capillary pillars may be configured to aid the capillary movement of the fluid through the microstructure pattern.

[0012] In some implementations, the microstructure pattern further includes a stop valve. The stop valve includes at least two triangular constrictions configured to urge fluid out of the stop valve.

[0013] In some implementations, the crossflow filtration channel borders the filtration boundary of the crossflow filtration chamber and is configured to prevent cells in the fluid from aggregating at said filtration boundary.

[0014] In some implementations, the filtration boundary borders the interior volume of the crossflow filtration chamber for a portion of the perimeter of the interior volume. The filtration boundary may have one or more gaps to allow a portion of cells in the fluid to enter the interior volume (e.g., for counting of cells in the interior volume, differential analysis of different blood cell types such as red blood cells, white blood cells and platelets or morphological analysis of the collected cells electrically and / or optically).

[0015] In some implementations, the crossflow filtration channel directs the fluid around the micro structure pattern and toward the outlet channel (directly or indirectly through other channels or structures).

[0016] In some implementations, the microneedle device further includes peripheral channels in fluidic communication (directly or indirectly) with the inlet channel and the outlet channel. The peripheral channels may be configured to receive fluid from the inlet channel (directly or indirectly through other channels or structures, e.g., the crossflow filtration chamber), retain the fluid (e.g., forming a serpentine reservoir), and direct the fluid towards the outlet channel (directly or indirectly through other channels or structures).

[0017] In some implementations, the microneedle device further includes a cell analysis chamber (e.g., a red blood cell and / or white blood cell testing chamber, a cell testing chamber) in fluidic communication (direct or indirectly) with the inlet channel, the crossflow filtration chamber, and the outlet channel. The cell analysis chambers may be configured to receive a controlled portion of cells in the fluid exited from the crossflow filtration channel for analysis of cellular biomarkers (e.g., complete blood counts optically or electrically, morphological analysis of blood cells through image processing).

[0018] In some implementations, the cell analysis chambers are further configured to receive a controlled portion of fluid filtered through the microstructure pattern of the crossflow filtration chamber and mix the filtered fluid with the controlled portion of cells.

[0019] In some implementations, the cell analysis chambers include an interior volume defined by cell analysis chamber microstructures spaced to control the mixing of the filtered fluid and cells so as to achieve an intentional dilution.

[0020] In some implementations, the microneedle device further includes an analyte analysis chamber (e.g., a biomarker analysis chamber) in fluidic communication (directly or indirectly) with the interior volume of the crossflow filtration chamber. The analyte analysis chamber may be configured to receive (e.g., acting as a reservoir) a portion of the fluid excised from the crossflow filtration channel for analysis of analyte biomarkers (e.g., optical or electrochemical).

[0021] In some implementations, the analyte analysis chamber includes a reagent (e.g., colorimetric protein assays, antibody-conjugated gold nanoparticles, antibody-conjugated fluorescent probes).

[0022] In some implementations, the analyte analysis chamber includes a microstructure pattern that may be configured to spatially control the deposition of the reagent and prevent unintended movement of the reagent out of the analyte analysis chamber.

[0023] In some implementations, the analyte analysis chamber is configured to receive fluid filtered through the microstructure pattern of the crossflow filtration chamber.

[0024] In some implementations, the microneedle device further includes a reagent chamber configured to deliver a reagent (e.g., colorimetric protein assays, antibody- conjugated gold nanoparticles, antibody-conjugated fluorescent probes) to the analyte analysis chamber.

[0025] In some implementations, the reagent chamber may be configured to deliver a reagent (e.g., cell staining solution, colorimetric protein assays, antibody conjugated gold nanoparticles, antibody conjugated fluorescent probes) to the cell analysis chamber (e.g., for differential cell analysis, e.g., 3- or 5-part differential white blood cells counts or easier differentiation of red blood cells from white blood cells).

[0026] In some implementations, the crossflow filtration chamber further includes a chemical agent detector paper, a glucose test paper, and / or a litmus test paper.

[0027] In some implementations, the microfluidic substrate further includes a second inlet channel, a second outlet channel, and a second crossflow filtration chamber. The second inletchannel may be configured to drive the capillary movement of a second portion of the fluid across the second inlet channel. The second outlet channel may be configured to drive capillary movement of the second portion of the fluid across the second outlet channel. The second crossflow filtration chamber may include a second crossflow filtration channel in fluidic communication (directly or indirectly) with the second inlet channel and the second outlet channel and be configured to drive capillary movement of the second portion of the fluid across a second filtration boundary formed between the second crossflow filtration channel and a second interior volume defined by a second microstructure pattern of the second crossflow filtration chamber.

[0028] In some implementations, the second crossflow filtration channel directs the second portion of the fluid around the second microstructure pattern and toward the second outlet channel (directly or indirectly through other channels or structures).

[0029] In some implementations, the inlet channel, outlet channel, and crossflow filtration channel collectively have a first path length, and the second inlet channel, second outlet channel, and second crossflow filtration channel collectively have a second path length. In some implementations, the first path length and the second path length are the same. In other implementations, the first path length and the second path length are different.

[0030] In some implementations, the microfluidic substrate includes 1 testing channel. In other implementations, the microfluidic substrate includes 2, 3, 4, 5, 6, 7, or 8 testing channels. Some testing channels may be configured to test the same or different analytes, biomarkers, or cell characteristics relative to other testing channels.

[0031] In some implementations, a portion of the microfluidic substrate is transparent for a colorimetric test to be performed by the microneedle device.

[0032] In some implementations, the microfluidic substrate is configured to couple to a handheld test system (e.g., to test blood plasma enzymes, metabolites, proteins, exosomes, and hormones).

[0033] In some implementations, the microfluidic substrate is configured to couple to a portable test system (e.g., to perform cellular biomarker analysis such as complete blood counts, cell morphology tests or malaria detection).

[0034] In some implementations, the microfluidic substrate is configured to couple to a bench-top test system (e.g., to test for rare blood biomarkers such as cell-free cancer DNA, plasma toxins or heavy metals).

[0035] In some implementations, the microneedle device further includes one or more electrodes integrated into the microfluidic substrate. In some implementations, the one or more electrodes are disposed over at least one of the crossflow filtration chamber, the analyte analysis chamber, the cell analysis chamber, and the outlet channel. In some implementations, the one or more electrodes are interdigitated electrodes.

[0036] In some implementations, the microfluidic substrate further includes one or more buffer channels configured to direct buffer solution into the inlet channel, thereby diluting fluid contained within the inlet channel. In some implementations, the one or more buffer channels include a plurality of buffer channels disposed on opposite sides of the inlet channel orthogonal to the inlet channel. In some implementations, the microfluidic substrate further includes a cell counting channel disposed subsequent to the one or more buffer channels. In some implementations, a plurality of parallel plate electrodes are disposed on opposite sides of the cell counting channel, wherein the parallel plate electrodes are configured to count a portion of cells in the fluid.

[0037] In another aspect, the system described herein relates to a cartridge device, including a microfluidic substrate including, an inlet channel, an outlet channel, and a crossflow filtration channel. The inlet channel may be configured to drive the capillary movement of a fluid (e.g., a body fluid such as a blood or environmental fluid) across the inlet channel. The outlet channel may be configured to drive capillary movement of the fluid across the outlet channel. The crossflow filtration chamber may have a crossflow filtration channel in fluidic communication (directly or indirectly) with the inlet channel and the outlet channel and be configured to drive capillary movement of the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber. The cartridge device may further include a testing channel, which comprises a collection of structures and channels, including at least an inlet channel, a crossflow filtration chamber, and an outlet channel.

[0038] In some implementations, the crossflow filtration channel directs the fluid around the micro structure pattern and toward the outlet channel (directly or indirectly through other channels or structures).

[0039] In some implementations, the inlet channel is configured to receive the fluid from a pipette.

[0040] In some implementations, the cartridge device may include features of any of the other implementations.

[0041] In another aspect, the system described herein relates to a microneedle device or cartridge device according to any of the other implementations and an analysis system having a plurality of sensors that is configured to interrogate the crossflow filtration chamber, the outlet channel, or a channel therebetween.

[0042] In another aspect, a method of filtering a fluid is disclosed. The method includes: (i) driving by capillary movement a fluid (e.g., a body fluid such as a blood or environmental fluid) across an inlet channel; (ii) driving by capillary movement the fluid into a crossflow filtration chamber having a crossflow filtration channel in fluidic communication (directly or indirectly) with the inlet channel and an outlet channel; (iii) driving by capillary movement the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber; and (iv) driving by capillary movement the fluid across the outlet channel.

[0043] Additional features will be set forth in part in the description, which follows or may be learned by practice. The features will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive, as claimed.BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1A - ID show block diagrams of exemplary capillary action-driven microneedle systems for excising blood and directing said blood through a microfluidic pattern on a microfluidic substrate via capillary movement, wherein the blood is filtered and analyzed, in accordance with an illustrative embodiment.

[0045] FIG. IE - 1H show block diagrams of an exemplary capillary action-driven system like those of FIGS. 1 A- ID, but wherein a microneedle assembly is not necessarily required, in accordance with various illustrative embodiments.

[0046] FIG. II shows a block diagram of an exemplary capillary action-driven system like that of FIGS. 1H, but wherein an electrode is integrated into the microfluidic substrate, in accordance with various illustrative embodiments.

[0047] FIG. 1 J shows a block diagram of an exemplary capillary action-driven system like those of FIGS. FIGS. 1 A- ID, but wherein the blood is diluted with a flow of buffer before advancing toward a cell counting channel, in accordance with various illustrative embodiments.

[0048] FIGS. 2A - 2J show diagrams of exemplary crossflow filtration chambers of a capillary action-driven microneedle or cartridge system and the subcomponents thereof, in accordance with various illustrative embodiments.

[0049] FIG. 3 A - 3C show exemplary methods of using a capillary action-driven microneedle system, wherein blood excised by the microneedle is driven through the crossflow filtration chamber of the microfluidic substrate so as to filter out cells, thereby directing purified plasma to regions of the microfluidic substrate containing a reagent, in accordance with an illustrative embodiment.

[0050] FIGS. 4A - 4D show exemplary methods of fabricating and functionalizing a capillary action-driven microneedle or cartridge system, in accordance with an illustrative embodiment.

[0051] FIG. 5 A - 5B shows an exemplary capillary action-driven microneedle system incorporated into a disposable patch device, in accordance with an illustrative embodiment.

[0052] FIGS. 6 shows an exemplary capillary action-driven microneedle system, in accordance with an illustrative embodiment.

[0053] FIGS. 7A - 7B show exemplary topologies of the microfluidic substrate in exemplary capillary action-driven microneedle or cartridge systems, in accordance with an illustrative embodiment.

[0054] FIGS. 8A - 8B show blood moving through the crossflow filtration chamber in an exemplary capillary action-driven microneedle or cartridge system.

[0055] FIG. 8C shows a block diagram of an exemplary capillary action-driven microneedle system configured to partially filter blood.

[0056] FIG. 8D shows a block diagram of an exemplary capillary action-driven microneedle system for achieving a proportional mixing between purified plasma and filtered-out cells for analysis.

[0057] FIG. 9 shows crossflow filtration of blood cells from plasma and experimental results of colorimetric pH testing of the plasma within the interior volume of the crossflow filtration chamber in an exemplary capillary action-driven microneedle or cartridge system.

[0058] FIGS. 10A - 10B show an exemplary capillary action-driven microneedle system that includes integrated electrodes for electronic biosensing, in accordance with an illustrative embodiment.

[0059] FIG. 11 A - 1 ID show an exemplary capillary action -driven microneedle system that is configured to dilute blood with a buffer to facilitate cell counting within cell counting channels, in accordance with an illustrative embodiment.

[0060] Various objects, aspects, features, and advantages of the disclosure will become more apparent and better understood by referring to the detailed description taken in conjunction with the accompanying drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements.DETAILED DESCRIPTION

[0061] Some references, which may include various patents, patent applications, and publications, are cited in a reference list and discussed in the disclosure provided herein. The citation and / or discussion of such references is provided merely to clarify the description of the present disclosure and is not an admission that any such reference is “prior art” to any aspects of the present disclosure described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference.

[0062] Example System

[0063] Described herein is a complete platform for collection and microfiltration of capillary blood and on-chip analysis of blood biomarkers for point-of-care diagnostics.

[0064] Referring generally to the figures, FIG. 1 A - FIG. IF show exemplary capillary action-driven microfluidic filter systems for body fluid analysis, according to various implementations.

[0065] FIG. 1 A - FIG. ID show an exemplary capillary action-driven microfluidic filter system, including a microneedle device 100 (shown as 100a) and a microfluidic substrate 101 (shown as 101a). As shown in FIG. 1 A, the microfluidic substrate 101 includes an inlet channel 102 (shown as 102a), an outlet channel 104 (shown as 104a), and a crossflow filtration chamber 106 (also referred to herein as plasma collection spots) (shown as 104a and also referred to herein as a microfluidic filter). The inlet channel 102 is configured to drive capillary movement of a fluid across the inlet channel 102. As shown in FIG. 1A, the fluid is blood (e.g., whole blood). In some implementations, the fluid may be capillary blood or another body fluid, such as interstitial fluid. In some implementations, the fluid may be an environmental fluid. The outlet channel 104 is configured to drive capillary movement of blood across the outlet channel 104. The device further includes a cover 162 (shown as 162a)disposed opposite the microfluidic substrate 101 such that microfluidic channels are formed in the gap between the microfluidic substrate 101 and cover 162.

[0066] Filtration Structures

[0067] As shown in FIG. 1 A, the crossflow filtration chamber 106 includes a crossflow filtration channel 108 (also referred to herein as crossflow blood channel, crossflow filtration channel, and / or capture trench) (shown as 108a) in direct fluidic communication with the inlet channel 102 and in indirect fluidic communication with the outlet channel 104. In some implementations, the crossflow filtration channel 108 may be in direct or indirect fluidic communication with the inlet channel 102 and / or the outlet channel 104.

[0068] As shown in FIG. 1 A, the crossflow filtration channel 108 is configured to drive capillary movement of blood across a filtration boundary 110 formed by filtration structures (shown as 114a) formed between the crossflow filtration channel 108 and an interior volume 116 (shown as 116a) of the crossflow filtration chamber 106. The crossflow filtration chamber interior volume 116 is defined by a microstructure pattern 112 (shown as 112a) of the crossflow filtration chamber 106.

[0069] Various implementations of the crossflow filtration channel 108, filtration boundary 110, and microstructure pattern 112 are also shown, for example, in FIG. 2A - FIG. 2J. As shown in FIG. 1 A and FIG. 2 A, the microstructure pattern 112 (shown as 112a and 212a, respectively) includes spaced apart filtration structures 114 (shown as 114a and 214a, respectively) adjacent the crossflow filtration channel 108. As best shown in FIG. 2B, spacings between the filtration structures 114 are smaller than the size of blood cells in the fluid, thereby resisting capillary movement of the blood cells across the filtration boundary 110 formed by filtration structures (shown as 114a and 214a, respectively). FIG. 2A - FIG. 2B show the microstructure pattern 112 (shown as 212a) further including spaced-apart capillary pillars 213 (e.g., capillary buffer pillars), wherein the capillary pillars 213 are configured to aid the capillary movement of the fluid through the microstructure pattern 112, thereby controlling a rate of capillary movement of the fluid from the crossflow filtration channel 108 (shown as 208a) toward the interior volume 116 (shown as 216a) of the crossflow filtration chamber 106 (shown as 206a). Furthermore, FIG. 2A shows a microstructure pattern 112 having capillary couplers 217. The capillary couplers can allow the passage of the filtered plasma from the filtration structures 114a to the collection reservoir 116a, e.g., serving like an elevator, taking the plasma from the shallow filtration zone to the deeper pool.

[0070] Additional filtration structures are shown in FIG. 3B and FIG. 4D. Specifically, FIG. 3B and 4D show stop valves 315, which are configured to resist the flow of liquid from leaking to other channels or structures. In some implementations, the stop valves 315 operate by an abrupt expansion in the crossflow filtration channel 108 in the centrally outward direction, which results in positive capillary pressure, thereby pinning liquid in the interior volume 116 within the triangular constrictions shown. In order to achieve improved reliability, a secondary stop valve 315 may be included to follow the first. The secondary stop valve 315 may have the same or different dimensions relative to the first stop valve 315.

[0071] In some embodiments, the filtration structures 114a can also be used as capillary stop valves in the reverse flow during reagent deposition. The abrupt deepening of the flow channel from the shallow filtration zone to the crossflow filtration channels (108a) can pin the liquid at the filtration boundary. This reverse operation and stopping is depicted in Fig. 4C.

[0072] FIG. 1 A and FIG. 2A show that the crossflow filtration channel 108 also directs blood around the microstructure pattern 112 of the crossflow filtration chamber 106 such that it remains unfiltered whole blood. As shown in FIG. 2 A, the crossflow filtration channel 108 surrounds the filtration boundary 110 of the filtration chamber 106 and is configured to prevent cells in the blood from aggregating at said filtration boundary filtration boundary 110.

[0073] Specifically, FIG. 1 A shows the crossflow filtration channel 108 directing whole blood around the microstructure pattern 112 that filters the blood and towards the cell analysis chamber 130 before eventually (e.g., indirectly) flowing towards the outlet channel 104. In other implementations, the crossflow filtration channel 108 may direct unfiltered fluid, such as whole blood, toward the crossflow filtration chamber 106 indirectly through other channels or structures. In some implementations, the crossflow filtration channel 108 may partially pass whole blood from the inlet channel 102 through a portion of the microstructure pattern 112 so as to partially filter the blood. In some implementations, this partially filtered blood is then directed from the crossflow filtration chamber 106 towards the outlet channel 104 either directly or indirectly through other structures or channels. For example, FIG. 8C shows blood being directed from the inlet channel 102 (shown as 802a) to both peripheral buffer channels 132 (shown as 832a) and the crossflow filtration chamber 106 (shown as 806a). Within the crossflow filtration chamber 106, the blood is partially filtered and then directed to a cell analysis chamber 130 (shown as 830a).

[0074] Additional illustrations of the crossflow filtration channel 108 directing blood around the microstructure pattern 112 and filtration boundary 110 are shown, for example, in the implementation shown in FIG. 3A and FIG. 3B. In such exemplary implementations, the crossflow filtration channel 108 surrounds the filtration boundary 110, which in turn surrounds the interior volume 116 for a portion of a perimeter of the interior volume 116.

[0075] In other implementations, the crossflow filtration channel 108 may be disposed interior to the filtration boundary 110, which in turn may be disposed interior to the interior volume 116 such that fluid is filtered from the crossflow filtration channel 108 radially outward across the filtration boundary 110 and into the interior volume 116. In such implementation, the filtration boundary 110 may border an interior portion of a perimeter of the interior volume 116.

[0076] The filtration boundary 110 may have one or more gaps to allow a portion of cells in the fluid to enter the interior volume 116 (e.g., for counting of cells in the interior volume, differential analysis of different blood cell types such as red blood cells, white blood cells and platelets or morphological analysis of the collected cells electrically and / or optically). Such implementations may permit unfiltered fluid to enter a portion of the interior volume 116 or may include multiple stages of filtration structures 114 so as to control the degree of filtration of a portion of the fluid within the crossflow filtration chamber 106.

[0077] For example, the implementation shown in FIG. 3B, FIG. 4D, FIG. 7B, FIG. 8A, and FIG. 8B includes a crossflow filtration chamber 106 (shown as 106a’) having two stages of crossflow filtration channels 108a’ and 308 defined by the microstructure pattern 112 (shown as 112a’). As shown, whole blood is delivered to the first crossflow filtration channel 108a’ from the inlet channel 102a’. A portion of the whole blood passes through the filtration boundary 110a’ created by the filtration structures 114a’ and toward the inner volume 116a’. This portion of partially-filtered blood is then delivered to the second crossflow filtration channel 308. A portion of the partially-filtered blood passes through the second filtration boundary 310 created by the filtration structures 114a’ and further toward the inner volume 116a’. At each stage, the whole blood delivered from the inlet channel 102a’ may be increasingly filtered, and the portion that does not pass through the boundary of a respective stage may pass through crossflow filtration channels 108a’ and 308, respectively, and toward other channels or microstructures. Other implementations may include additional stages of filtration structures and corresponding crossflow filtration channels 108.

[0078] Peripheral Channels

[0079] As shown in FIG. 1 A, microneedle device 100 further includes peripheral channels 132 (e.g., serpentine channels, peripheral buffer channels, or capillary buffer channels) (shown as 132a) in indirect fluidic communication with the inlet channel 102 and in direct fluidic communication with the outlet channel 104. In some implementations, the peripheral channels 132 may be in direct or indirect fluidic communication with either the inlet channel 102 and / or the outlet channel 104. In some implementations, the peripheral channels 132 may be configured to receive blood from the inlet channel 102 indirectly through other channels or structures, such as the crossflow filtration chamber 106. As shown, for example, in FIG. 2F - FIG. 2 J, the peripheral channels 132 (shown as 132f, 132g, 132h, and 132i) may receive whole blood from the crossflow filtration channel 108 of the crossflow filtration chamber 106 that has not been filtered through the filtration structures 114.

[0080] As shown in FIG. 1 A and FIG. 2C - FIG. 2E, the peripheral channels 132 (shown as 232c, 232d, and 232e) are configured to receive whole blood from a cell analysis chamber 130 (shown as 230c, 230d, and 230e), retain the blood (e.g., forming a serpentine reservoir), and direct the blood towards the outer channel 104 (shown as 204c, 204d, and 204e). In other implementations, the peripheral channels 132 may indirectly direct fluid towards the outlet channel 104 through other channels or structures, such as a cell analysis chamber 130 that is disposed between the peripheral channels 132 and the outlet channel 104. In other implementations, the peripheral channels 132 may receive whole or partially filtered blood from structures other than the cell analysis chambers 130.

[0081] In some implementations, as shown in FIG. 1C, the inlet channel 102 (shown as 102c) bifurcates so as to direct the flow of blood to the peripheral channels 132 (shown as 132c) and the crossflow filtration channel 108 of the crossflow filtration chamber 106 (shown as 106c) separately. Thus, in this example, the flow of blood exiting the inlet channel 102 is only partially subjected to crossflow filtration in the crossflow filtration chamber 106 such that the peripheral channels 132 receive blood from the inlet channel 102 that has not been filtered by the crossflow filtration chamber 106 (e.g., whole blood).

[0082] As described herein, the inlet channel 102, crossflow filtration channel 108, peripheral channels 132, outlet channel 104 and / or any other channel on the microfluidic substrate 101 may be referred to generally as microfluidic channels or microfluidic capillary channels.

[0083] Crossflow Geometries

[0084] FIG. 2C - FIG. 2J show various exemplary geometries of the crossflow filtration chamber 106 and the substructures therewithin, according to some implementations.

[0085] FIG. 2C shows the crossflow filtration chamber 106 (shown as 206c) having a circular-shaped configuration. FIG. 2D shows the crossflow filtration chamber 106 (shown as 206d) having an angled configuration. Some such implementations may be rectangular or diamond-shaped. FIG. 2E shows the crossflow filtration chamber 106 (shown as 206e) having an oval or elliptical-shaped configuration.

[0086] FIG. 2F shows a microfluidic substrate 101 (shown as 20 If) having an inlet channel 102 (shown as 202f) that delivers blood to a singular circle-shaped crossflow filtration chamber 106 (shown as 206f). The crossflow filtration chamber 106 has a crossflow filtration channel 108 (shown as 208f) bifurcates so as to surround the filtration boundary 110 (shown as 21 Of , which in turn surrounds the filtration structures 114 (shown as 214f). The interior volume 116 (shown as 216f) adjacent the filtration boundary 110 is in direct fluidic communication with a reagent chamber 126 (shown as 226f). Furthermore, in this implementation, a portion of the blood may enter the peripheral channels 132 (shown as 232f) without passing through the filtration structures 114.

[0087] FIG. 2G shows a microfluidic substrate 101 (shown as 201g) having a crossflow filtration chamber 106 (shown as 206g) that includes a plurality of radially-projecting looped structures, wherein the crossflow filtration channel 108 (shown as 208g) follows a path along the outside of the looped structures toward the peripheral channels 132 (shown as 232g) and surrounds the filtration boundary 110 (shown as 210g). Each looped structure comprises its own portion of the crossflow filtration channel 108, filtration boundary 110, interior volume 116 (shown as 216g), and filtration structures 114 (shown as 214g). In some implementations, the looped structures may include other subcomponents of the microstructure pattern 112 (shown as 112g), which may be similar to or different from the subcomponents of the other looped structures. The respective crossflow filtration channel portions 108 of the looped structures direct blood into the adjacent looped structure. The respective interior volume portions 116 adjacent to the several filtration boundaries 110 are in direct fluidic communication with a reagent chamber 126 (shown as 226g). A portion of the blood may enter the peripheral channels 132 (shown as 232g) without passing through the filtration structures 114.

[0088] FIG. 2H shows a microfluidic substrate 101 (shown as 201 h) having a crossflow filtration chamber 106 (shown as 206h) that includes a plurality of radially-projecting circularstructures, wherein each circular structure comprises its own portion of the crossflow filtration channel 108 (shown as 208h), filtration boundary 110 (shown as 21 Oh), interior volume 116 (shown as 216h), and filtration structures 114 (shown as 214h). In some implementations, the circular structures may include other subcomponents of the microstructure pattern 112 (shown as 212h), which may be similar to or different from the subcomponents of the other circular structures. The respective crossflow filtration channel portions 108 of the radially-projecting circular structures direct blood into the adjacent radially-projecting circular structure. The respective interior volume portions 116 adjacent to the several filtration boundaries 110 are in indirect fluidic communication with the reagent chamber 126 (shown as 226h). Each respective interior volume portion 116 filters blood into an inwardly directed microfluidic channel. The several inwardly directed microfluidic channels connect in a central region of the crossflow filtration chamber 106 and connect to an additional microfluidic channel that extends from the crossflow filtration chamber 106 into the reagent chamber 126. A portion of the blood may enter the peripheral channels 132 (shown as 232h) without passing through the filtration structures 114.

[0089] FIG. 21 shows a microfluidic substrate 101 (shown as 20 li) having a crossflow filtration chamber, crossflow filtration chamber 106 (shown as 206i) that includes radially- projecting looped structures. In this exemplary implementation, the respective interior volume portions 116 (shown as 216i) adjacent to the several filtration boundaries 110 (shown as 21 Oi) are in indirect fluidic communication with the reagent chamber 126 (shown as 226i). Each respective interior volume portion 116 filters blood into an inwardly directed microfluidic channel. The several inwardly directed microfluidic channels connect in a central region of the crossflow filtration chamber 106 and connect to an additional microfluidic channel that extends from the crossflow filtration chamber 106 into a reagent chamber 126. A portion of the blood may enter the peripheral channels 132 (shown as 232i) without passing through the filtration structures 114 (shown as 214i).

[0090] FIG. 2J shows a microfluidic substrate 101 (shown as 20 Ij) having a crossflow filtration chamber crossflow filtration chamber 106 (shown as 206j) having an internal detection chamber that is filled with antibody conjugated microspheres, and the reagent chamber is filled with antibody conjugated gold nanoparticles. This configuration illustrates a serial order between the crossflow filtration chamber / module followed by the reagent (in this case antibody conjugated gold nanoparticles) deposition chamber that is followed by an antibody-conjugated microsphere reservoir / chamber. The device is configured to operatesimilarly to a lateral flow assay in which the filtered plasma first picks up the gold nanoparticles and reacts with it. The nanoparticles that are bound to a target in the plasma get captured by the microspheres and generates a bright red color in this blue zone.

[0091] Microneedle Assembly

[0092] As shown in FIG. 1A, the microneedle device 100 also includes a microneedle assembly 134 (shown as 134a) coupled to the inlet channel 102. As shown, the microneedle assembly has a first hollow microneedle 136 (shown as 136a) configured to excise the fluid from a tissue once placed at a collection site on a person and direct the fluid to the inlet channel 102. In other implementations, the microneedle assembly may include multiple hollow microneedles. In some implementations, the blood may be directed from the first hollow microneedle 136 to a reservoir 138 (e.g., central blood reservoir) (shown as 138a) of the microneedle assembly 134 that is configured to retain the blood before it is directed to the inlet channel 102.

[0093] Cell Analysis Chamber

[0094] As shown in FIG. 1 A, the microneedle device 100 further includes a cell analysis chamber 130 (e.g., cell testing chamber, red blood cell testing region) (shown as 130a) in indirect fluidic communication with the inlet channel 102, direct fluidic communication with the crossflow filtration chamber 106, and indirect fluidic communication with the outlet channel 104. In some implementations, the cell analysis chamber 130 may be in direct or indirect fluidic communication with the inlet channel 102, the crossflow filtration chamber 106, and / or the outlet channel 104. For example, the cell analysis chamber 130 may receive the fluid directly after having been filtered or purified by the crossflow filtration chamber 106, may receive the fluid following filtration after it has been directed through other intervening channels or structures, or may receive the fluid directly from the inlet channel 102 or crossflow filtration channel 108 without it having passed through the filtration structures 114 of the crossflow filtration chamber 106.

[0095] The cell analysis chamber 130 shown in FIG. 1 A is configured to receive a controlled portion of cells in the fluid exited from the crossflow filtration channel 108 for analysis of cellular biomarkers. In some implementations, biomarker analysis may include obtaining complete blood counts optically or electrically and / or morphological analysis of blood cells through image processing. As shown in FIG. 1 A, the cell analysis chamber 130 contains and is configured to test red blood cells collected from the blood. In some implementations, the cell analysis chamber 130 may be used to test other cell types, such aswhite blood cells. In the implementation shown in FIG. 1 A, the cell analysis chamber 130 directs the flow of blood toward the peripheral channels 132, which receive blood from the cell analysis chambers 130. However, in other implementations, the blood may be directed to the peripheral channels 132 before it enters the cell analysis chamber 130 such that the cell analysis chamber 130 receives blood from the peripheral channels 132.

[0096] In some implementations, the cell analysis chamber 130 may be disposed in a central region of the crossflow filtration chamber 106 itself. In such implementations, fluidcontaining cells may exit the crossflow filtration channel 108 through gaps in the filtration boundary 110 and be directed into the interiorly disposed cell analysis chambers 130. In some implementations, additional channels exist to direct the flow of fluid-containing cells out of the crossflow filtration chamber 106 toward additional cell analysis chambers 130.

[0097] Analyte Chamber

[0098] In some implementations, the microneedle device 100 may further include an analyte analysis chamber 120 (e.g., a biomarker analysis chamber, plasma testing region) in direct or indirect fluidic communication with the interior volume 116 of the crossflow filtration chamber 106 (e.g., as shown in Fig. 1 A). As shown in the example in Fig. 1 A, the analyte analysis chamber 120 is located within interior volume 116 of the crossflow filtration chamber 106 to provide an area of detection of analytes.

[0099] As shown in FIG. 1 A, the analyte analysis chamber 120 is integrated into the crossflow filtration chamber 106 itself. In some implementations, the analyte analysis chamber 120 may be integrated into another microfluidic channel. The analyte analysis chamber 120 includes a reagent 122. In some implementations, the reagent 122 may include colorimetric protein assays, antibody-conjugated gold nanoparticles, and / or antibody- conjugated fluorescent probes. In some implementations, the analyte analysis chamber 120 further includes a chemical agent detector paper, a glucose test paper, and / or a litmus test paper. In some implementations, a portion of the microfluidic substrate 101 is transparent so that a colorimetric test performed by the microneedle device 100 may be visualized. In some implementations, one or more testing channels 118 of microneedle device 100 may include multiple analyte analysis chambers 120 that include one or more different reagents 122.

[0100] In some implementations, the analyte analysis chamber 120 may include a microstructure pattern 124 that can be configured to spatially control the deposition of the reagent 122 and prevent unintended movement of the reagent 122 out of the analyte analysis chamber 120. For example, FIG. 1 A shows an analyte analysis chamber 120 integrated intothe crossflow filtration chamber 106, such that the microstructure pattern 112 includes a microstructure pattern 124. In this implementation, the analyte analysis chamber 120 is configured to receive blood filtered through the microstructure pattern 112 and the microstructure pattern 124 is also configured to prevent unintended movement of the reagent 122 out of the crossflow filtration chamber 106. In other implementations, the analyte analysis chamber 120 may be disposed within the crossflow filtration chamber 106 such that microstructure pattern 124 is a separate structure from the microstructure pattern 112 of the crossflow filtration chamber 106.

[0101] In other examples, e.g., as shown in Fig. 1G, the analyte analysis chamber 120 (shown as 120g) is configured as an external chamber that receives fluid directly from the crossflow filtration chamber 106 (or other structures such as the inlet channel 102 or other intervening channel or structure). For example, the analyte analysis chamber 120 may be configured to receive (e.g., acting as a reservoir) a portion of the fluid excised from the crossflow filtration channel 108 for analysis of analyte biomarkers. Such analyses may include, for example, optical and / or electrochemical analyses. In some implementations, as described further below, analyses of analyte biomarkers may be performed using an electrode-based biosensing mechanism.

[0102] In yet further implementations, the microneedle device 100 may further include one or more additional analyte analysis chambers 120’. For example, FIG. 1H shows an example microneedle device 100 (shown as lOOh) having an analyte analysis chamber 120 (shown as 120h) configured to receive fluid excised directly from the crossflow filtration chamber 106 and a second analyte analysis chamber 120’ (shown as 120h’) configured to receive a portion of the fluid excised from the crossflow filtration channel 108 (shown as 108h).

[0103] Reagent Chamber

[0104] Additionally, as shown in FIG. 1 A, the microneedle device 100 includes a reagent chamber 126 (shown as 126a) configured to deliver the reagent 122 to the analyte analysis chamber 120. In some implementations, the reagent chamber 126 may be configured to deliver the reagent 122 to the cell analysis chamber (e.g., for differential cell analysis, e.g., 3- or 5-part differential white blood cells counts or easier differentiation of red blood cells from white blood cells). In some implementations, the microneedle device 100 may include multiple reagent chambers 126 that are configured to deliver one or more different reagents 122.

[0105] However, in some implementations, as shown, for example, in FIG. IB, the microneedle device 100 may not include a reagent chamber 126 in direct or indirect fluidic communication with the crossflow filtration chamber 106 (shown as 106b), analyte analysis chamber 120 (shown as 120b), and / or cell analysis chambers 130 (shown as 130b).

[0106] Multiple Testing Channels

[0107] The capillary action-driven microfluidic filter system includes a testing channel 118, which is a collection of structures and channels comprising at least an inlet channel 102, a crossflow filtration chamber 106, and an outlet channel 104. For example, implementations shown in FIG. 1 A, FIG. IB, and FIG. 1C include a microneedle device (shown as 100a, 100b, and 100c respectively) having 1 testing channel 118 (shown as 118a, 118b, and 118c respectively). However, in other implementations, the microfluidic substrate 101 may include 2, 3, 4, 5, 6, 7, or 8 testing channels.

[0108] For example, FIG. ID shows a microneedle device 100 having at least 2 testing channels 118 (shown as 118d and 118d’, respectively). Some testing channels 118 may be configured to test the same or different analytes, biomarkers, or cell characteristics relative to other testing channels.

[0109] Accordingly, some implementations have multiples of the structures and channels previously described, such as multiple inlet channels 102, outlet channels 104, crossflow filtration chambers 106, peripheral channels 132, cell analysis chambers 130, analyte analysis chambers 120, reagent chambers 126, and the subcomponents thereof. As shown in FIG. ID, the microneedle device lOOd further includes a second inlet channel 102d’, a second outlet channel 104d’, and a second crossflow filtration chamber 106d’, so as to form a second testing channel 118d’. The second inlet channel 102d’ is configured to receive a second portion of blood from the first inlet channel 102d and drive capillary movement of the second portion of blood across the second inlet channel 102d’. The second outlet channel 104d’ is configured to drive capillary movement of the second portion of blood across the second outlet channel 104d’. The second crossflow filtration chamber 106d’ includes a second crossflow filtration channel 108d’ in direct fluidic communication with the second inlet channel 102d’ and in indirect fluidic communication with the second outlet channel 104d’. In some implementations, the additional crossflow filtration chambers 106 may be in direct or indirect fluidic communication with the additional inlet channels 102 and / or the additional outlet channels 104.

[0110] As shown in FIG. ID, the second crossflow filtration channel 108d’ is configured to drive capillary movement of the second portion of blood through the second crossflow filtration chamber 106d’. As shown, the second crossflow filtration channel 108d’ directs the second portion of the fluid indirectly toward the second outlet channel 104d’. In other implementations, the second crossflow filtration channel 108d’ directs the second portion of blood towards the second outlet channel 104d’ directly or indirectly through other channels or structures.[OHl] The inlet channel 102, outlet channel 104, and crossflow filtration channel 106 collectively, which together form a testing channel 118, has a first path length.Implementation that includes multiple testing channels 118 may define testing channels 118 having additional path lengths, such as a second path length. As shown in FIG. ID, the first path length and the second path length are the same. However, in other implementations, the first path length and the second path length are different. Such implementations may differ in respective counts of inlet channels 102, outlet channels 104, crossflow filtration chambers 106, peripheral channels 132, cell analysis chambers 130, analyte analysis chambers 120, reagent chambers 126, and the subcomponents thereof.

[0112] As described herein, in some implementations, a single microfluidic substrate 101 can include multiple testing channels 118. For instance, testing channels may be arranged such that a single inlet channel 102 and directs fluid to two or more crossflow filtration chambers 106 and / or two or more outlet channels 104. For example, FIG. 2A shows a single microfluidic substrate 101 (shown as 201a) having several pairs of testing channels. For instance, testing channels 218a and 218a’ share a common inlet 202a and crossflow filtration chamber 206a, but lead to two different outlet channels 204a and 204a’. In fact, the substrate 201a includes a total of 4 pairs of testing channels (testing channels 218b and 218b’ serve as another example, but additional pairs are apparent in FIG. 2A).

[0113] Mixing of Filtered and Unfdtered Fluid

[0114] As best shown in FIG. 8D, the cell analysis chamber 830b is further configured to receive a controlled portion of purified plasma filtered through the crossflow filtration chamber 806b (e.g., blood subjected to complete crossflow filtration) and mix the purified plasma with a controlled portion of blood received from the crossflow filtration channel 808 that contains cells so as to achieve a proportional mixing. In some implementations, the cell analysis chamber 830b may include an interior volume defined by cell testing chambermicrostructures spaced to control the mixing of the purified plasma and cells so as to achieve an intentional dilution.

[0115] Cartridge or Pipette

[0116] FIG. IE and FIG. IF, show an exemplary capillary action-driven microfluidic filter system, including a cartridge device 139 (shown as 139e and 139f, respectively) and a microfluidic substrate 101. The cartridge device 139 shown in FIG. IE includes structures and channels analogous to those in the microneedle device 100a shown in FIG. 1 A but does not include a microneedle assembly 134. Rather, blood is delivered to the cartridge device 139 via an inlet. As shown in FIG. IE and FIG. IF, the inlet is configured to receive blood from a pipette. In other implementations, the inlet may receive fluid, such as blood, from another source, such as a cartridge. In some implementations, the cartridge device 139 may include features of any of the other implementations of the capillary action-driven microfluidic filter system. For instance, FIG. IF shows a cartridge device 139 analogous to the microneedle device lOOd shown in FIG. ID but does not include a microneedle assembly 134.

[0117] Coupling to Other Systems

[0118] In some implementations, the microfluidic substrate 101 is configured to couple to a handheld test system (e.g., to test blood plasma enzymes, metabolites, proteins, exosomes, and hormones). In some implementations, the microfluidic substrate 101 is configured to couple to a portable test system (e.g., to perform cellular biomarker analysis such as complete blood counts, cell morphology tests, or malaria detection). In some implementations, the microfluidic substrate 101 is configured to couple to a bench-top test system (e.g., to test for rare blood biomarkers such as cell-free cancer DNA, plasma toxins, or heavy metals).

[0119] Sensing Instrument

[0120] In another aspect, the system described herein is directed to a microneedle device 100 or cartridge device 139 according to any of the other implementations, further comprising a sensing instrument 140 that may have one or more sensors configured to interrogate the crossflow filtration chamber 106, the outlet channel 104, and / or any structure and / or any channel therebetween. For example, FIG. 1 A shows a sensing instrument 140 (shown as 140a) having a sensor 142 (shown as 142a) configured to interrogate the crossflow filtration chamber 106a, a sensor 142a’ configured to interrogate the cell analysis chamber 130a, and a sensor 142a” configured to interrogate the peripheral channels 132a. In otherembodiments, the sensing instrument 140 may include various other counts and combinations of sensors 142.

[0121] Integrated Electrodes

[0122] In yet further implementations, the microneedle device 100 or cartridge device 139 may further include one or more electrodes 141 integrated into the microfluidic substrate 101. For example, the one or more electrodes 141 can operate according to the principles of electrochemical impedance. Accordingly, the one or more electrodes 141 can be interdigitated electrodes 141 deposited over any of the various chambers and / or channels described herein. FIG. II shows an exemplary capillary action-driven microfluidic filter system, including microneedle device 100 (shown as lOOi) including various electrodes 141 (shown as electrodes 141, 141’, 141”, 141’”, and 141ilv, respectively) integrated into the microfluidic substrate 101. As shown in FIG. IE, the electrode 14 li is deposited over the crossflow filtration 106i. FIG. IE further shows an electrode 141i’ deposited over the analyte analysis chamber 120, an electrode 141i” deposited over the second analyte analysis chamber 120i’, an electrode 141i’ ” deposited over the cell analysis chamber 130i, and an electrode 14 lilvdeposited over the cell outlet channel 104i .

[0123] In some implementations, the one or more electrodes 141 include interdigitated gold electrodes, wherein fingers of the one or more electrodes 141 form capacitors. The fingers of the one or more electrodes 141 can be functionalized with antibodies or aptamers through a thiol -based linker. In some examples, target molecules (e.g., antigens) in the plasma can diffuse through the medium (e.g., cell plasma) and absorb onto a surface of the electrode, thereby effecting a change in the relative permittivity of the local electrode surface that in turn results in a shift in the capacitance of the electrode. The change in capacitance is proportional to the concentration of the target molecules in the plasma. Accordingly, the one or more electrodes 141 facilitate operation of an electronic biosensing mechanism as the sensing instrument 140 that can perform such analyses non-optically.

[0124] In some examples, the electrodes 141 can be integrated into the microfluidic substrate 101 using fabrication techniques such as stencil lithography. In such examples, a “shadow mask” that has the pattern of the one or more electrodes 141 is made on a silicon wafer through deep reactive ion etching. The mask can then be used during physical vapor deposition of the electrode material (e.g., gold stacked on titanium). This allows resist-free and scalable manufacturing of a capillary action-driven microfluidic filter system having a thermoplastic microfluidic substrates 101 with integrated biosensors.

[0125] Cell Counting

[0126] In yet further implementations, the microneedle device 100 or cartridge device 139 can include microfluidic structures to facilitate the counting of cells, such as blood cells. FIG. 1 J shows an exemplary microneedle device 100 (shown as 1 OQj) that is configured to dilute a sample of whole blood such that the number of blood cells can be counted. Specifically, the microneedle device lOOj includes one or more buffer channels 160 (shown as 160j) that direct buffer solution 161 (shown as 16 Ij ) into a portion of the microfluidic capillary channels carrying blood. In the illustrated example, the microneedle device 100 includes two buffer channels 160 positioned on opposite sides of the inlet channel 102 (shown as 102j) that carries whole blood from the microneedle assembly 134 (shown as 134j). The two buffer channels 160 are oriented orthogonal relative to the inlet channel 102.

[0127] As shown in FIG. 1 J, buffer solution 161 flows through the buffer channels 160 toward a merger point where the buffer channels 160 intersect the inlet channel 102, at which the buffer solution 161 and the whole blood are mixed as they flow together through a common microfluidic channel (e.g. a mixing channel). In some examples, the buffer solution 161 self-stops at the merger point until exposed to a flow of whole blood through the inlet channel 102. As with other flow within the microfluidic substrate 101, flow of the buffer solution 161 is driven by capillary pressure within the various microfluidic channels and chambers of the microfluidic substrate 101. In some examples, the buffer channels 160 are more resistive than the inlet channel 102. For example, a resistance in the buffer channels 160 can be 50 times less than a resistance in inlet channel 102. In some examples, the resistiveness of the microfluidic channels, such as the buffer channels 160 or inlet channel 102 can be controlled by adjusting the length and / or geometry of the channel. Despite application of the same or similar capillary pressures to the whole blood flowing from the inlet channel 102 and the buffer solution 161 from the buffer channels 160, differences in resistance between the inlet channel 102 and buffer channels 160, in combination with viscosity differences between the whole blood and buffer solution 161, cause the whole blood and buffer solution 161 to move at significantly different flow rates. Thus, the whole blood can be diluted by at least 100 times, thereby facilitating isolation of individual blood cells for counting in the one or more cell counting channels, as described below.

[0128] As further shown in FIG. 1 J, the mixture of blood and buffer solution 161 are driven toward a cell counting channel 131 (shown as 13 Ij) that is integrated into the microfluidic substrate 101. In some examples, the cell counting channel 131 is shallower than the channelin which the blood and buffer solution 161 are mixed, thus further narrowing the flow of diluted blood. As shown in the illustrated example, parallel plate electrodes 164 are positioned on opposite sides of the cell counting channel 131, the parallel plate electrodes 164 being defined by microfluidic channels oriented orthogonally relative to the cell counting channel 131. In some examples, the parallel plate electrodes 164 (shown as 164j) are formed by filling these microfluidic channels with a conductive ink (e.g., silver nanoparticle or carbon nanotube ink) via capillary action. These parallel plate electrodes 164 can subsequently be used to perform electrical counting of the passing diluted blood cells via the Coulter Principle. As shown in FIG. 1 J, the diluted blood can then be driven toward a peripheral channel 132 (shown as 132j), such as a serpentine channel, which acts as a waste reservoir and capillary pump for the various microstructures of the microneedle device 100. In some examples, the peripheral channels 132 can further lead to an outlet channel 104 (shown in FIG. 1 J as 104j).

[0129] In some examples, including the example illustrated in FIG. 1 J, the microneedle device 100 can include an additional cell counting channel 131’ (shown as 13 lj’) subsequent to the first cell counting channel 131 (shown as 13 lj). At least because the additional cell counting channel 131’ is reduced in size relative to first cell counting channel 131, the resistance in the buffer channels 160 can be 100 times less than a resistance in inlet channel 102. This allows for improved measuring of the dilution ratio of the diluted blood, which in turn can be used to estimate the original cell count of the whole blood sample.

[0130] By comparing the counted cell numbers in the cell counting channel to the counted cell numbers in the additional cell counting channel 131’, a true dilution ratio can be determined. This dilution ratio in turn facilitates estimation of the viscosity of the whole and / or diluted blood, because the difference between measured and calculated dilution ratios is related to the viscosity difference between the whole blood and the buffer solution 161, given that the viscosity of the buffer solution 161 is known.

[0131] It is contemplated herein that the one or more buffer channels 160 can merge with blood flow at any position along the various channels and chambers described herein. For example, the buffer channels 160 can deliver buffer solution 161 to a testing channel 118 at a mixing point located before or after a crossflow filtration chamber 106, analyte testing chamber 120 and / or cell analysis chamber 130. Accordingly, the buffer solution 161 may be mixed with either whole blood or blood that has already been filtered.

[0132] It is further contemplated herein, that various implementations of the capillary action-driven microfluidic system can include a microneedle device 100 that facilitates cell counting but does not necessarily include cell filtration microstructures. For example, the microneedle device 100 can include any of the above-referenced microfluidic structures for cell counting with or without filtration microstructures such as the crossflow filtration chamber 106.

[0133] Furthermore, the above-described cell counting structures and techniques can be implemented in a cartridge device 139, in which whole blood is introduced into an inlet channel 102 via a dedicated inlet (e.g., from a pipette).

[0134] Example Method of Use

[0135] In another aspect, this disclosure relates to a method of filtering a fluid. The method includes: (i) driving by capillary movement a fluid across an inlet channel 102; (ii) driving by capillary movement the fluid into a crossflow filtration chamber 106 having a crossflow filtration channel 108 in fluidic communication (directly or indirectly through other channels or structures) with the inlet channel 102 and an outlet channel 104; (iii) driving by capillary movement the fluid across a filtration boundary 110 formed between the crossflow filtration channel 108 and an interior volume 116 defined by a microstructure pattern 112 of the crossflow filtration chamber 106; and (iv) driving by capillary movement the fluid across the outlet channel 104.

[0136] As shown in FIG. 3 A, whole blood introduced into the inlet channel 102 (shown as 102a) is directed into the crossflow filtration chamber 106 (shown as 106a) and into the crossflow filtration channels 108 (shown as 108a). The whole blood engages with filtration structures 114 (shown as 114a) at a filtration boundary 110 (shown as 110a) defined by a microstructure pattern 112 (shown as 112a). Capillary effect draws the blood into the filtration structures towards the interior volume 116 (shown as 116a) of the crossflow filtration chamber 106, as shown in FIG. 7A. As shown in FIG. 3 A and 7A, filtration of the whole blood occurs as plasma is permitted to pass through the filtration structures 114 while relatively larger blood cells are impeded at the filtration boundary 110. As shown in FIG. 3 A, the crossflow filtration channels 108 includes triangular coupler structures that move the plasma into the interior volume 116 (acting as a reservoir). As shown in FIG. 7 A, the portion of the blood that does not pass through the filtration structures 114 into the interior volume 116 (i.e., the portion of the blood that contains cells), is directed through the crossflow filtration channels 108 and out of the crossflow filtration chamber 106. A constructed modelshows that capillary effect directs the whole blood through the crossflow filtration channels 108. This same effect draws blood toward the filtration structures 114 of the microstructure pattern 112.

[0137] Also described herein is a method of detecting the presence of molecular or cellular analytes using a capillary action-driven microfluidic filter system. As shown in FIG. 3C, whole blood may be directed through microstructure pattern filtration structures 112 (shown as 112a) and into an interior volume 116 (shown as 116a) of a crossflow filtration chamber 106. The purified blood may then be directed to an analyte analysis chamber 120 containing an assay reagent 122 that is chemically reactive with the fluid delivered into the analyte analysis chamber 120. As shown in FIG. 3C, the assay reagent forms a dried layer within the interior volume 116. As the capillary effect draws blood through the microstructure pattern filtration structures 112, purified blood enters the interior volume 116 and interacts with the dried assay reagent 122. As shown in FIG. 3C, the assay reagent 122 may be a colorimetric protein assay such that a color change occurs when the assay reagent 122 reacts with target analytes in the purified blood. In some implementations, the reagent 122 may include colorimetric protein assays, antibody-conjugated gold nanoparticles, and / or antibody- conjugated fluorescent probes. In some implementations, the analyte analysis chamber 120 further includes a chemical agent detector paper, a glucose test paper, and / or a litmus test paper.

[0138] In some implementations, a portion of the microfluidic substrate 101 is transparent so that a colorimetric test performed by the microneedle device 100 may be visualized. In some implementations, one or more testing channels 118 of microneedle device 100 may include multiple analyte analysis chambers 120 that include one or more different reagents 122.

[0139] In some embodiments, the microneedle device may be configured for lateral flow detection in which the detection chamber is filled with antibody-conjugated microspheres and the reagent chamber is filled with antibody-conjugated gold nanoparticles (see Fig. 2 J).

[0140] Example Method of Fabrication

[0141] Molding

[0142] Provided herein is a method of fabricating a microneedle device 100 having a microfluidic substrate 101 as an example of a capillary action -driven microfluidic system. Specifically, FIG. 4A and 4B provide a method 400 for the fabrication of a capillary action- driven microfluidic filter device 100a having a microneedle assembly 134a. As shown inFIG. 4A, a primer (e.g., hexamethyldisilazane (HMDS)) was applied to a silicone wafer 402 using spin coating at 3500rpm for 45 seconds. Then, the photoresist 404 (e.g., Microposit S 1813) was spin-coated at 2500rpm for 60 seconds. The photoresist 404 was then baked for 1 minute at 115°C. Then, the photoresist 404 was patterned by exposing it using a maskless alignment system (e.g., MLA 150, Heidelberg Instruments) with a dose of 150mj / cmA2 for the creation of the 1.5um deep filtration microstructure channels. The exposed resist was then developed (e.g., using Mf-319) for 1 minute. After development, the wafer 402 was subjected to a deep reactive ion etching (DRIE) chamber and vertically etched 1.57um. Then, the existing photoresist 404 layer was removed with acetone before again spinning the wafer 402 with the photoresist 404 (e.g., using SPR-220) at 2500rpm for 40 seconds. The wafer 402 was pre-baked for 3 minutes at 115°C. Using the same maskless alignment system, the mask was patterned by exposing it to a dose of 400mj / cmA2 for the creation of the deeper whole blood and plasma reservoir structures. Then, the exposed mask was developed in Mf-319 for 3 minutes. Upon completion, wafer 402 was placed in the DRIE chamber and etched 48 um deep. Lastly, the photoresist 404 was sonicated in acetone for removal of photoresist 404 material and was further cleaned with oxygen plasma in a reactive ion etching chamber for 3 minutes. This process produced a silicon master mold, which was vapor coated with lH,lH,2H,2H-Perfluorooctyl-trichlorosilane in a desiccator for 8 hours and baked at 120°C for 5 minutes to fully immobilize the coating. Following this, an inverse PDMS replica 406 was cured on the silicon master mold and peeled off for stamping by inverse molding.

[0143] Moreover, a method for making a microneedle assembly is shown in FIG. 4B. As shown, a 28-gauge hypodermic needle 408 (360um outer diameter, 180um inner diameter) was cut 4mm 17 below the needle tip with the aid of a 3D printed piece for quick and accurate cuts each time. The cut needle 408 was placed into and supported by another circular 3D printed guide piece 410 that was 25mm in diameter, 2mm thick, and had a 450 mm wide hole at its center. This printed guide piece 410 served to guide the needle 408 and keep it vertically oriented. The 2mm thickness ensured that the needle 408 would not tilt at an angle exceeding 2.5 degrees when the needle 408 was tilted within the hollow core. After the cut hypodermic needle 408 was placed in the center of the printed guide piece 410, a PTFE- coated steel wire 412 (diameter 152um) was guided through the needle hollow core. This wire 412 allowed for maintaining a hollow core during the molding of the polymer microneedles. After assembly of the needle 408, printed guide piece 410, and wire 412, thecomponents were taped to the bottom of a petri dish 414, and a PDMS inverse replica 416 of the microneedle structure was cured.

[0144] Then, the same PTFE-coated wire 412 is placed in the center of the top PDMS stamp 416 and fixed in place using epoxy. Using the wire guide opening at the center of the bottom mold, the two PDMS structures 406 and 416 were attached and aligned with the help of the wire 412. Then, PLA pellets (e.g., Ingeo, Biopolymer 4043D) are added into the space formed between the PDMS pieces 406 and 416. PLA was selected as a material after consideration of two primary performance criteria: biocompatibility and mechanical properties. Regarding biocompatibility, polylactic Acid (PLA) was selected because it is a bioresorbable polymer (i.e., it can be absorbed in vivo within the skin tissue). This property may be advantageous in the event that the microneedle breaks inside the patient during use and cannot be retrieved. Secondly, PLA has advantageous mechanical properties. According to manufacturers, PLA has a yield strength of 60MPa, which is well above the required mechanical strength needed to perform the present method.

[0145] The PLA pellets 418 were then melted to form the capillary action-driven microfluidic filter device 100a. The melting temperature of the pellets 418 was approximately 150°C, and the temperature tolerance of the PTFE coating and PDMS molds 406 and 416 was around 250°C, meaning the molds 406 and 416 were suitable for the melt process. The molds 406 and 416 and the stamps were placed in an oven that was set to 160°C, and the pellets 418 were melted for 45 minutes. Using a temperature higher than this results in the boiling of the molten PLA and introduces defects to the structure. Before the mold was removed from the oven, a hot stamping machine (e.g., Carver) was preheated to 190°C. This temperature was within the tolerance of the mold materials and did not start boiling the molten PLA as there was a temperature gradient from the PDMS to the PLA, and the exposure time was less than a minute. The stamp was placed on top of the liquid PLA- containing mold, and the assembly was placed on the heated plates. The plates of the stamping machine were slowly brought together to apply a gentle force on the PDMS pieces 406 and 416 until the molten PLA 418, which was visually inspected, had filled the gap between them. This process produced the needle-shaped trench on the bottom mold while also stamping the back-end pattern into the material. After that, the part was taken out of the machine to cool and solidify.

[0146] The same process was repeated for the top part of the cover 162a, except this time, the bottom PDMS mold structure was only a thin PDMS film attached to a lin2glass slide.The cover 162a and capillary action-driven microfluidic filter device 100a are shown in FIG. 4B.

[0147] The capillary action-driven microfluidic filter device 100a and cover 162a must then be bonded together and surface functionalized to seal the microfluidic channels and provide the hydrophilicity required to produce the desired capillary effect.

[0148] For the bonding, there are many options provided in the literature, but such methods are targeted at larger and deeper microfluidic channels that can tolerate a fair degree of deformation. However, because the present disclosure relates to micropatterned structures with 1.5um depth and 5um pitch, it would the techniques described herein require a much smaller deformation tolerance. A preferred bonding method is one that is very uniform and deformation-free while also providing sufficient bonding strength to allow a certain degree of flexibility required by the techniques described herein. Considering all these factors, a custom adhesive bonding process was developed to satisfy the present requirements.

[0149] To begin, %1 Polyvinyl Acetate (PVAc) was dissolved in a solvent mixture of 1 :7 w / w Acetone / Ethanol. The significance of this solvent mixture was in the tuning of Hansen solubility parameters. Acetone was selected as a preferred solvent because it is a good solvent for both PLA and PVAc. It showed an immediate effect in contact with these polymers. Conversely, Ethanol is a weak solvent of PVAc but not a solvent of PLA. By the empirical rules of Hansen solubility parameters, a solvent mixture will have a superposition of the individual parameters of the constituents. Therefore, the 1 :7 w / w Acetone / Ethanol mixture still had good solvent power for PVAc but not for PLA, thus providing a significant selectivity. PVAc was selected because it has a glass transition temperature between 30- 40°C, whereas PLA has a Tg of 60°C. Therefore, the PVAc reflows and bonds the parts together at 40°C without causing any visible damage to the PLA parts.

[0150] After treating both parts with oxygen plasma for 1 minute at 250W of power, the solution was then spin-coated on the cover 162a at 3500rpm for 30 seconds. The tuned mixture showed no deformation of the structures on the PLA substrate during the process. This resulted in a 50nm thick PVAc film on the PLA surface. Following the PVAc coating, the two parts were clamped together using a c-clamp with a PDMS piece at the bottom to protect the needle. The clamped parts were placed in the oven at 40°C for 30 minutes and allowed to cool down and solidify at room temperature.

[0151] In further examples, use of PLA as described anywhere herein may be substituted for polycarbonate (PC), which can offer improved resistance to higher temperatures (e.g., such as may occur during the sputtering of electrodes 141).

[0152] Functionalization

[0153] The final part of the patch fabrication is the functionalization of the analyte analysis chamber 120 (e.g., detection spot). As shown in FIG. 4B, the capillary action-driven microfluidic filter device 100 (shown as 100a) may be functionalized by treatment with one or more assay reagents 122 (shown as 122a).

[0154] In the study, a colorimetric detection method was configured to introduce colorchanging assay reagents into respective reagent chambers 126 and direct the solutions through the reagent inlet channel 128 toward the analyte analysis chamber 120 by capillary action. As shown in FIG. 4D, capillary stop valves 315 in the analyte analysis chambers 120 resist the liquid from leaking to other channels or structures. Lastly, the formation of engineered capillary buffer pillars 213 (shown as 113a’) in the analyte analysis chamber 120 helps control the drying of supplied assay reagent solutions. Through the application of these structures, solid material within the assay solution forms deposits in a controlled fashion within the analyte analysis chamber 120 such that the flow of plasma within the analyte analysis chamber 120 is not obstructed. Likewise, these structures' advantageous allow for the uniform dissolution of chemicals back into the plasma during operation.

[0155] An example functionalization procedure is shown in FIG. 4C. As shown, liquid assay reagent 122 (shown as 122a) flows into the reagent chamber 126 (shown as 126a).

[0156] FIG. 4D further shows the assay reagent 122a’ flowing from the reagent chamber 126a’, through the reagent inlet channel 128 (shown as 128a’), and toward the interior volume 116 (shown as 116a’). In some implementations, such as in FIG. 4C, the reagent chamber 126 is in fluid communication with the analyte analysis chamber — the chamber in which purified blood plasma collects after passing through the filtration boundary 110 formed by the filtration structures 114 (shown as 114a). As shown in both FIG. 4C and FIG. 4D, the assay reagent (shown as 122a and 122a’, respectively) is then allowed to dry so as to form a layer or coating on the surface of the micropattemed surfaces it flowed over. As shown in FIG. 4C and FIG. 4D, the interior volume 116 includes dried essay reagent 122. Accordingly, a microfluidic substrate 101 (shown as 101a) of the microneedle device 100 was formed.

[0157] Additional Example Method of Fabrication

[0158] As described above, the present disclosure relates to methods of fabricating a microneedle device 100 having a microfluidic substrate 101 as an example of a capillary action-driven microfluidic system. In some examples, the method includes fabrication of a master mold for the microfluidic structures (e.g., chambers and / or channels) of the microfluidic substrate 101. For example, the master mold can be fabricated using techniques such as 3-dimensional (“3D”) printing; silicon micromachining (e.g., additive via deposition or substrative via wet or dry etching); and / or laser ablation of a substrate (e.g., metal, polymer, glass, silicon, etc.).

[0159] The master mold can then be used to fabricate the microfluidic structures using techniques such as hot embossing, injection molding, and / or soft lithography.

[0160] In further examples, the microfluidic structures can be fabricated directly on the final microfluidic substrate 101 (e.g., metal, thermoplastic, or other polymeric substrate) via laser or mechanical machining processes (e.g., CNC, EDM, etc.) without requiring a master mold.

[0161] The microfluidic structures can then be sealed. For example, an adhesive tape can be placed over the microfluidic structures. In further examples, another thermoplastic substrate can be used to seal the microfluidic structures via thermal fusion bonding. In yet further examples, any flat substrate can be used to seal the microfluidic structures in conjunction with an adhesive (e.g., thermal or UV curing, etc.).

[0162] As described herein, the materials used for forming the microfluidic substrate 101 can include metals or polymers, including thermoplastics. As described herein, polymeric microfluidic substrates 101 can be chosen from materials including PLA and PC. In some examples, the microfluidic substrate 101 can itself be hydrophilic. This promotes capillary action. However, in further examples, the microfluidic substrate 101 can be made hydrophilic using any one or more of: plasma or corona treatment; grafting of hydrophilic polymers onto the surface of the microfluidic substrate 101; layer-by-layer assembly of a hydrophilic thin film; and / or applying a thin hydrophobic film to the microfluidic substrate 101 using dipping, spinning, and / or spraying techniques.

[0163] Furthermore, the microneedle assembly 134 described herein can be fabricated by any one or more of: injection molding or hot embossing using a master mold structure; direct machining on the final substrate by laser or mechanical techniques; and / or 3D printing.

[0164] Experimental Results and Additional Examples

[0165] Additional Examples

[0166] In some implementations, the capillary action-driven microfluidic filter system may be incorporated into a patch that contacts the tissue of a person. As shown in FIG. 5A - FIG. 5B, an example patch 500 (e.g. disposable polymeric patch) includes the microneedle device 100 (shown as 100a) as described herein.

[0167] The example patch 500 shown in FIG. 5A includes a capillary action-driven microfluidic filter device 100 (shown as 100a) having a disposable microfluidic substrate 101 (e.g., a reusable polymeric chip) (shown as 101a) that is coupled to a small reusable sensing instrument 140 (e.g., a read-out system) (shown as 140a). FIG. 5 A shows an exploded view of the patch 500 and its subcomponents. The sensing instrument 140 (shown as 140a) is disposed adjacent (e.g., in a stacked relationship) to the capillary action-driven microfluidic filter device 100 on an opposite side relative to the microneedle assembly 134 (shown as 134a). In some implementations, the patch 500 can further include a transmitter that is configured to wirelessly transmit data obtained from the sensing instrument 140 to an external processor or display. The sensing instrument 140 is operatively connected to an energy source 152 (e.g., a battery) (shown as 152a). The energy source 152 is operatively connected to an inductive charging coil 502. A plastic enclosure 504 is disposed of over the other components of the patch 500.

[0168] In some implementations, as shown in FIG. 5B, the end user assembles the components of the patch 500 and applies the patch 500 onto the skin using a small manual force. The small size of the microneedle assembly 134 allows painless insertion with sufficient skin penetration force. These parameters dependent strongly on needle tip diameter, which was measured to be around 0.8 IN for the beveled hypodermic needles. As shown in FIG. 5B, following insertion, capillary blood from the dermis was sampled with a single hollow polymeric microneedle assembly 134 (shown as 134a). The assay read-out was done through the microfluidic substrate 101 that is attached to the disposable polymeric patch 500. Depending on the assay, the microfluidic substrate 101 (shown as 101a) can contain a transimpedance amplifier topology for electrochemical assays, an LED and a photodiode for gold nanoparticle-based absorbance assays or a miniature camera for cellular assays.

[0169] Blood collection and sample transport within the microfluidic substrate 101 are both performed passively through the capillary effect. The polymeric microfluidic substrate 101 and cover 162 were patterned via hot embossing for the creation of the microneedle as well as the microfluidic channels during the fabrication. The disclosed manufacturing method can be easily converted to microinjection molding for mass production.

[0170] Blood initially collected in the central reservoir moves through the channels and the cells are progressively filtered or sorted by size. The microfluidic structures on the microfluidic substrate 101 are configurable to measure molecular biomarkers from plasma or for complete blood cell counts from whole blood.

[0171] Precision micromachining of the functional compartments and optical transparency of the materials implemented allow for convenient monolithic integration of sophisticated sensing modalities such as nanohole arrays or nanowire sensors.

[0172] An additional example of a capillary action-driven microfluidic filter device 100 (shown as 600) according to some implementations is shown in FIG. 6. The implementation shown includes structures and channels analogous to those in the microneedle device 100a shown in FIG. 1 A. Furthermore, the capillary action-driven microfluidic filter device 600 also includes features analogous to those shown in FIG. 2A respecting a microfluidic substrate 101 (shown as 601) having multiple pairs of testing channels.

[0173] Operation of the capillary action-driven microfluidic filter device 600 is based on the principle of crossflow filtration of whole blood such that red blood cells are unable to pass through filtration microstructures, but plasma passes into the interior volume 616 of the crossflow filtration chamber 606. In this implementation, the filtration structures 114 are 1.5um deep and the interior volume 116 of the crossflow filtration chamber 106 is 45um deep. In other implementations, as shown in FIG. 2B, the filtration structures 114 are 1.4um deep. The red blood cells become stuck at the shallow and / or narrow filtration structures, but blood plasma is allowed to pass into the interior volume 616. The trapped red blood cells then further enhance the filtration effect and nearly perfect plasma purification is achieved.

[0174] As shown in FIG. 6, the PLA microfluidic substrate 601 includes a microneedle assembly 634 in the center and microfluidic channels patterned on its surface. The PLA cover 662 with central pillars is shown. These pillars aid in moving the vertically collected blood from the needle assembly 638 to the rest of the microfluidic substrate 601. The cover 662 also contains an adhesive coating and seals the capillary microfluidic channels after bonding. After bonding of the microfluidic substrate 601 cover 662 is complete, the ends of the microfluidic channels therebetween remain open, thereby permitting the venting of air during passive fluid filling.

[0175] Experimental Results

[0176] In a specific implementation, Fig. 4D shows the self-limiting functionalization of the analyte analysis chamber 120 in the capillary action-driven microfluidic filter device 100a’,In this example, the analyte analysis chamber 120 was also the interior volume 116a’ of the crossflow filtration chamber 106a’. In this example, the color-changing chemical reagent 122a’, a universal pH indicator, was introduced into the reagent chamber 126a’. The reagent solution 122a’ moved through the reagent inlet channel 128a’ and filled the analyte analysis chamber 120 (here, the interior volume 116a’). As explained before, due to the abrupt expansion of the fluidic structure at the stop valves 115a’, the liquid reagent 122a’ stopped before reaching the blood filtration boundary 110a’ to prevent the deposition of solid material there. After around 6 hours, the solid content in the solution preferentially accumulated between the capillary buffer pillars 113a’ in the spot, as these areas are where the capillary pressure is the highest. The fully dried and functionalized analyte analysis chamber 120 (here, the interior volume 116a’) is also shown in FIG. 4D. The controlled deposition of assay reagent formed connections between capillary buffer pillars 113a’. This effect aided the flow of plasma towards the interior volume 116a’ and allowed quick re-dissolution as the plasma kept filling the interior volume 116a’.

[0177] In another specific implementation, FIG. 8A shows an example of the shallow filtration structures of a capillary action-driven microfluidic filter device 100a’ after bonding. As shown, illumination under a microscope shows the color red in the crossflow filtration channels 108a’ and 308 (e.g., shallow trenches), as these structures act like an optical cavity. These results demonstrate that these filtration structures formed effective filtration boundaries 110a’ and 310. Furthermore, these results indicate that the filtration boundaries 110a’ and 310 were free of deformation during the bonding such that the 1 ,5um filter depth was preserved. As shown, the first crossflow filtration channel 108a’ directed the flow of whole blood around the interior volume 116a’, thereby trapping the red blood cells. As shown, however, as the blood kept flowing, some red blood cells deformed and became captured between the filtration structures 112a’, resulting in a tight packing of red blood cells. This tight packing acted like a secondary filter for plasma. As shown in FIG. 8A, trapped cells occasionally leaked into the second capture trench created by the second crossflow filtration channel 308. This second crossflow filtration channel 308 was purposefully placed to capture the passing cells and a secondary filtering area having a second filtration boundary 310 follows it before the interior volume 116a’. As shown in FIG. 8B, the plasma in the innermost portion of the inner volume 116a’ was therefore pure of any cells or solid particulates.

[0178] FIG. 8B shows the plasma filing in the analyte analysis chamber 120 (here, the interior volume 116a’) of the capillary action-driven microfluidic filter device 100a’ at various time intervals. In this example, the overall filling time was around 10 minutes. However, this filling time can be optimized further to shorten the time. As the plasma filled the analyte analysis chamber 120, the red chemical pigments of the assay reagent 122a’ dissolved in the plasma and turned purple, reflective of the natural blood pH of around 7.4. The simultaneous filling and dissolution of the assay reagents resulted in uniform color throughout the analyte analysis chamber 120. Because the analyte analysis chamber 120 was 1.5mm in diameter, it could be conveniently coupled with a smartphone camera for detection. In some implementations, an integrated reader will be included for real-time data analysis during device operation.

[0179] FIG. 9 shows various color changes in response to blood samples of varying pH levels. As shown, a visible color change was observed that is significant enough for naked- eye detection. Nonetheless, to ensure quantitative measurements, a MATLAB script has been written to apply image corrections. This program automatically detected the circular pillar at the center of the analyte analysis chamber 120 (here, the interior volume 116a’) as shown by the blue circle around the masked files on the bottom row. After detecting the center of the analyte analysis chamber 120, a circular mask was applied to the whole image to consider only the pixels within the analyte analysis chamber 120. Then, a basic threshold filter was applied that removed the pixels with colors close to white (sum of RGB values higher than 600 for an image with 8-bit pixel depth) together with the fabrication artifacts (sum of RGB values less than 300, which are dark colored defects in the image). Although the fabrication artifacts in these pictures are not common and would be eliminated in a sterile manufacturing facility, having the capability to easily handle these defects in post-processing is useful as dust particles may land between the microfluidic substrate 101a’ and the camera in point-of- care use cases. Having removed these pixels, those that remain are shown with white in the binary image for each analyte analysis chamber 120. The R, G, and B channel values were then normalized and averaged for all these pixels, and the results were displayed next to each masked figure. The results indicate that there was a readily quantifiable pixel value change between responses relative to varying pH values.

[0180] In another specific implementation, FIGS. 10A - 10B show an example of the capillary action-driven microfluidic filter device 1000. In this example, each testing channel 1018 includes two electrodes 1041, which are positioned on opposite sides of cell analysischamber 1030. Specifically, the electrodes 1041 shown in FIG. 10A are sputtered gold electrodes. Blood delivered to the inlet channel 1002 is directed to the cell analysis chamber 1030, where it is analyzed by the electrodes 1041. Thereafter, the blood is directed into the peripheral channels 1032, which act as waste channels for the analyzed blood. In the illustrated example, the analyzed blood is ultimately directed toward an outlet channel 1004.

[0181] FIG. 10B shows an enlarged view of the electrodes 1041. Specifically, FIG. 10B shows interdigitations of the electrodes 1041 on either side of a cell analysis chamber 1030, which is configured as a channel-like microstructure. As shown, blood (e.g., blood plasma) is directed through the interdigitation of the electrodes 1041 and into the peripheral channels 1032, which serve to collect the blood following analysis.

[0182] In yet another specific implementation, FIG. 11 A - 1 ID show an example of the capillary action-driven microfluidic filter device 1100. As shown in FIG. 11 A, buffer solution 161 is introduced via two buffer channels 1160 on opposite sides of an inlet channel 1102. In the illustrated example, the buffer solution 1161 is retained within the buffer channels 1160 via a 3D capillary stop valve such that buffer solution 1161 is not released into the inlet channel 1102 until a flow of whole blood is supplied. When whole blood is directed through the inlet channel 1102, buffer solution 1161 flows from the buffer channels 1160 at a merger point where the buffer channels 1160 intersect orthogonally with the inlet channel 1102. The whole blood and buffer solution 1161 then flows toward a mixing channel, wherein the blood and buffer solution 1161 are mixed, thereby diluting the blood to facilitate counting. As shown, the microfluidic channel carrying the diluted blood can narrow toward the mixing channel so as to improve countability of cells within the blood.

[0183] As shown in FIG. 1 IB, the diluted blood is directed through the mixing channel toward a cell counting channel 1131. In the illustrated example, the cell counting channel 1131 is further narrowed relative to the mixing channel. Specifically, in the illustrated example shows the cell counting channel 1131 having a narrowed width configured to direct individual blood cells to proceed through the cell counting channel 1131 single-file. As described herein, reduced channel width / shallowing of the channel can improve the accuracy of cell counting techniques by isolating individual blood cells within the cell counting channel 1131.

[0184] FIG. 11C shows an enlarged view of a cell counting channel 1131. As shown, parallel plate electrodes 1164 are positioned on opposite sides of the cell counting channel 1131. Specifically, the microfluidic channels that define the parallel plate electrodes 1164 areshown positioned orthogonal to the cell counting channel 1131, the microfluidic channels of the parallel plate electrodes 1164 containing a conductive ink. FIG. 1 ID shows a further enlarged view of the parallel plate electrodes 1164 positioned on opposite sides of the cell counting channel 1131. As described herein, these parallel plate electrodes 1164 are subsequently used to perform electrical counting of the passing diluted blood cells via the Coulter Principle.

[0185] Configuration of Certain Implementations

[0186] The construction and arrangement of the systems and methods, as shown in the various implementations, are illustrative only. Although only a few implementations have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative implementations. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the implementations without departing from the scope of the present disclosure.

[0187] The present disclosure contemplates methods, systems, and program products on any machine-readable media for accomplishing various operations. The implementations of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Implementations within the scope of the present disclosure include program products, including machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine- readable media can be any available media that can be accessed by a general-purpose or special-purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machineexecutable instructions or data structures, and which can be accessed by a general purpose or special purpose computer or other machine with a processor.

[0188] When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general-purpose computer, special-purpose computer, or special purpose processing machines to perform a certain function or group of functions.

[0189] Although the figures show a specific order of method steps, the order of the steps may differ from what is depicted. Also, two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on the designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.

[0190] It is to be understood that the methods and systems are not limited to specific synthetic methods, specific components, or to particular compositions. It is also to be understood that the terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting.

[0191] As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another implementation includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another implementation. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0192] “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0193] Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises,” means “including but notlimited to,” and is not intended to exclude, for example, other additives, components, integers or steps. “Exemplary” means “an example of’ and is not intended to convey an indication of a preferred or ideal implementation. “Such as” is not used in a restrictive sense but for explanatory purposes.

[0194] Disclosed are components that can be used to perform the disclosed methods and systems. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed that, while specific reference of each various individual and collective combinations and permutation of these may not be explicitly disclosed, each is specifically contemplated and described herein, for all methods and systems. This applies to all aspects of this application, including, but not limited to, steps in disclosed methods. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific implementation or combination of implementations of the disclosed methods. Exemplary Aspects

[0195] In view of the described processes and compositions, hereinbelow are described certain more particularly described aspects of the disclosures. These particularly recited aspects should not, however, be interpreted to have any limiting effect on any different claims containing different or more general teachings described herein, or that the “particular” aspects are somehow limited in some way other than the inherent meanings of the language and formulas literally used therein.

[0196] Example 1 : A microneedle device comprising: a microfluidic substrate comprising: an inlet channel configured to drive capillary movement of a fluid across the inlet channel; an outlet channel configured to drive capillary movement of the fluid across the outlet channel; and a crossflow filtration chamber having a crossflow filtration channel in fluidic communication with the inlet channel and the outlet channel, the crossflow filtration chamber configured to drive capillary movement of the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber.

[0197] Example 2: A microneedle device according to any example herein, particularly example 1 further comprising: a microneedle assembly coupled to the inlet channel, the microneedle assembly having a first hollow microneedle configured to excise the fluid from a tissue once placed at a collection site on a person.

[0198] Example 3: A microneedle device according to any example herein, particularly examples 1-2, wherein the microstructure pattern comprises spaced-apart filtration structures adjacent the crossflow filtration channel, wherein spacings between the filtration structures are smaller than the size of blood cells in the fluid, thereby resisting capillary movement of the blood cells across the filtration boundary.

[0199] Example 4: A microneedle device according to any example herein, particularly examples 1-3, wherein the microstructure pattern further comprises spaced-apart capillary pillars, wherein the capillary pillars are configured to urge capillary movement of the fluid through the microstructure pattern.

[0200] Example 5: A microneedle device according to any example herein, particularly examples 1-4, wherein the microstructure pattern further comprises a stop valve, the stop valve comprising at least two triangular constrictions configured to urge fluid out of the stop valve.

[0201] Example 6: A microneedle device according to any example herein, particularly examples 1-5, wherein the crossflow filtration channel borders the filtration boundary of the crossflow filtration chamber and is configured to prevent cells in the fluid from aggregating at said filtration boundary.

[0202] Example 7: A microneedle device according to any example herein, particularly examples 1-6, wherein the filtration boundary borders the interior volume of the crossflow filtration chamber for a portion of a perimeter of the interior volume, the filtration boundary having one or more gaps to allow a portion of cells in the fluid to enter the interior volume, differential analysis of different blood cell types such as red blood cells, white blood cells and platelets or morphological analysis of the collected cells electrically and / or optically).

[0203] Example 8: A microneedle device according to any example herein, particularly examples 1-7, wherein the crossflow filtration channel directs the fluid around the microstructure pattern and toward the outlet channel.

[0204] Example 9: A microneedle device according to any example herein, particularly examples 1-8 further comprising peripheral channels in fluidic communication with the inlet channel and the outlet channel, the peripheral channels configured to receive fluid from the inlet channel, retain the fluid, and direct the fluid towards the outlet channel.

[0205] Example 10: A microneedle device according to any example herein, particularly examples 1-9 further comprising: a cell analysis chambers in fluidic communication with the inlet channel, the crossflow filtration chamber, and the outlet channel, the cell analysischambers configured to receive a controlled portion of cells in the fluid exited from the crossflow filtration channel for analysis of cellular biomarkers.

[0206] Example 11 : A microneedle device according to any example herein, particularly example 10, wherein the cell analysis chambers is further configured to receive a controlled portion of fluid filtered through the microstructure pattern of the crossflow filtration chamber and mix the filtered fluid with the controlled portion of cells.

[0207] Example 12: A microneedle device according to any example herein, particularly example 10-11, wherein the cell analysis chambers includes an interior volume defined by cell analysis chamber microstructures spaced to control the mixing of the filtered fluid and cells so as to achieve an intentional dilution.

[0208] Example 13: A microneedle device according to any example herein, particularly examples 1-12 further comprising: an analyte analysis chamber in fluidic communication with the interior volume of the crossflow filtration chamber, the analyte analysis chamber configured to receive a portion of the fluid excised from the crossflow filtration channel for analysis of analyte biomarkers.

[0209] Example 14: A microneedle device according to any example herein, particularly example 13, wherein the analyte analysis chamber includes a reagent.

[0210] Example 15: A microneedle device according to any example herein, particularly example 14, wherein the analyte analysis chamber includes a microstructure pattern configured to spatially control the deposition of the reagent and prevent unintended movement of the reagent out of the analyte analysis chamber.

[0211] Example 16: A microneedle device according to any example herein, particularly example 15, wherein the analyte analysis chamber is configured to receive fluid filtered through the microstructure pattern of the crossflow filtration chamber.

[0212] Example 17: A microneedle device according to any example herein, particularly examples 13-16, further comprising a reagent chamber configured to deliver a reagent to the analyte analysis chamber.

[0213] Example 18: A microneedle device according to any example herein, particularly examples 10-17, further comprising a reagent chamber configured to deliver a reagent to the cell analysis chambers.

[0214] Example 19: A microneedle device according to any example herein, particularly examples 13-18, wherein the analyte analysis chamber further includes a chemical agent detector paper, a glucose test paper, microbeads, and / or a litmus test paper.

[0215] Example 20: A microneedle device according to any example herein, particularly examples 1-19, wherein the microfluidic substrate further includes: a second inlet channel configured to drive capillary movement of a second portion of the fluid across the second inlet channel; a second outlet channel configured to drive capillary movement of the second portion of the fluid across the second outlet channel; and a second crossflow filtration chamber having a second crossflow filtration channel in fluidic communication with the second inlet channel and the second outlet channel, the second crossflow filtration chamber configured to drive capillary movement of the second portion of the fluid across a second filtration boundary formed between the second crossflow filtration channel and a second interior volume defined by a second microstructure pattern of the second crossflow filtration chamber.

[0216] Example 21 : A microneedle device according to any example herein, particularly example 20, wherein the second crossflow filtration channel directs the second portion of the fluid around the second microstructure pattern and toward the second outlet channel.

[0217] Example 22: A microneedle device according to any example herein, particularly examples 20-21, wherein the inlet channel, outlet channel, and crossflow filtration channel collectively has a first path length, wherein the second inlet channel, second outlet channel, and second crossflow filtration channel collectively has a second path length, the first path length and the second path length being the same.

[0218] Example 23: A microneedle device according to any example herein, particularly examples 20-21, wherein the inlet channel, outlet channel, and crossflow filtration channel collectively has a first path length, wherein the second inlet channel, second outlet channel, and second crossflow filtration channel collectively has a second path length, the first path length and the second path length being different.

[0219] Example 24: A microneedle device according to any example herein, particularly examples 1-23, wherein the microfluidic substrate includes 1 testing channel, the testing channel comprising at least an inlet channel, a crossflow filtration chamber, and an outlet channel.

[0220] Example 25: A microneedle device according to any example herein, particularly examples 1-23, wherein the microfluidic substrate includes 2, 3, 4, 5, 6, 7, or 8 testing channels.

[0221] Example 26: A microneedle device according to any example herein, particularly examples 1-25, wherein a portion of the microfluidic substrate is transparent for a colorimetric test to be performed by the microneedle device.

[0222] Example 27: A microneedle device according to any example herein, particularly examples 1-26, wherein the microfluidic substrate is configured to couple to a handheld test system.

[0223] Example 28: A microneedle device according to any example herein, particularly examples 1-26, wherein the microfluidic substrate is configured to couple to a portable test system (500).

[0224] Example 29: A microneedle device according to any example herein, particularly examples 1-26, wherein the microfluidic substrate is configured to couple to a bench-top test system.

[0225] Example 30: A microneedle device according to any example herein, particularly examples 1-29, further comprising one or more electrodes integrated into the microfluidic substrate.

[0226] Example 31 : A microneedle device according to any example herein, particularly example 30, wherein the one or more electrodes are disposed over at least one of the crossflow filtration chamber, the analyte analysis chamber, the cell analysis chamber, and the outlet channel.

[0227] Example 32: A microneedle device according to any example herein, particularly examples 30-31, wherein the one or more electrodes are interdigitated electrodes.

[0228] Example 33: A microneedle device according to any example herein, particularly examples 1-32, wherein the microfluidic substrate further comprises one or more buffer channels configured to direct buffer solution into the inlet channel, thereby diluting fluid contained within the inlet channel.

[0229] Example 34: A microneedle device according to any example herein, particularly example 33, wherein the one or more buffer channels comprise a plurality of buffer channels disposed on opposite sides of the inlet channel orthogonal to the inlet channel.

[0230] Example 35: A microneedle device according to any example herein, particularly examples 33-34, wherein the microfluidic substrate further comprises a cell counting channel disposed subsequent to the one or more buffer channels.

[0231] Example 36: A microneedle device according to any example herein, particularly example 35, wherein a plurality of parallel plate electrodes are disposed on opposite sides ofthe cell counting channel, wherein the parallel plate electrodes are configured to count a portion of cells in the fluid.

[0232] Example 37: A cartridge device comprising: a microfluidic substrate comprising: an inlet channel configured to drive capillary movement of a fluid across the inlet channel; an outlet channel configured to drive capillary movement of the fluid across the outlet channel; and a crossflow filtration chamber having a crossflow filtration channel in fluidic communication with the inlet channel and the outlet channel, the crossflow filtration chamber configured to drive capillary movement of the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber.

[0233] Example 38: A cartridge device according to any example herein, particularly example 37, wherein the crossflow filtration channel directs the fluid around the microstructure pattern and toward the outlet channel.

[0234] Example 39: A cartridge device according to any example herein, particularly examples 30-38, wherein the inlet channel is configured to receive the fluid from a pipette.

[0235] Example 40: A cartridge device according to any example herein, particularly examples 37-39 having the features of the microneedle device described in any example herein, particularly examples 3-36.

[0236] Example 41 : A system comprising: the microneedle device or the cartridge device of any example herein, particularly examples 1-40; and an analysis system having a plurality of sensors that is configured to interrogate the crossflow filtration chamber, the outlet channel, or a channel therebetween.

[0237] Example 42: A method of filtering a fluid comprising: driving by capillary movement a fluid across an inlet channel; driving by capillary movement the fluid into a crossflow filtration chamber having a crossflow filtration channel in fluidic communication with the inlet channel and an outlet channel; driving by capillary movement the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber; and driving by capillary movement the fluid across the outlet channel.

[0238] In view of the many possible aspects to which the principles of the disclosed disclosure can be applied, it should be recognized that the illustrated aspects are only preferred examples of the disclosure and should not be taken as limiting the scope of thedisclosure. Rather, the scope of the disclosure is defined by the following claims. We, therefore, claim as our disclosure all that comes within the scope and spirit of these claims.

Claims

CLAIMSWhat is claimed is:

1. A microneedle device comprising: a microfluidic substrate comprising: an inlet channel configured to drive capillary movement of a fluid across the inlet channel; an outlet channel configured to drive capillary movement of the fluid across the outlet channel; and a crossflow filtration chamber having a crossflow filtration channel in fluidic communication with the inlet channel and the outlet channel, the crossflow filtration chamber configured to drive capillary movement of the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber.

2. The microneedle device of claim 1 further comprising: a microneedle assembly coupled to the inlet channel, the microneedle assembly having a first hollow microneedle configured to excise the fluid from a tissue once placed at a collection site on a person.

3. The microneedle device of any one of claims 1-2, wherein the microstructure pattern comprises spaced-apart filtration structures adjacent the crossflow filtration channel, wherein spacings between the filtration structures are smaller than the size of blood cells in the fluid, thereby resisting capillary movement of the blood cells across the filtration boundary.

4. The microneedle device of any one of claims 1-3, wherein the microstructure pattern further comprises spaced-apart capillary pillars, wherein the capillary pillars are configured to urge capillary movement of the fluid through the microstructure pattern.

5. The microneedle device of any one of claims 1-4, wherein the microstructure pattern further comprises a stop valve, the stop valve comprising at least two triangular constrictions configured to urge fluid out of the stop valve.

6. The microneedle device of any one of claims 1-5, wherein the crossflow filtration channel borders the filtration boundary of the crossflow filtration chamber and is configured to prevent cells in the fluid from aggregating at said filtration boundary.

7. The microneedle device of any one of claims 1-6, wherein the filtration boundary borders the interior volume of the crossflow filtration chamber for a portion of a perimeter of the interior volume, the filtration boundary having one or more gaps to allow a portion of cells in the fluid to enter the interior volume, differential analysis of different blood cell types such as red blood cells, white blood cells and platelets or morphological analysis of the collected cells electrically and / or optically.

8. The microneedle device of any one of claims 1-7, wherein the crossflow filtration channel directs the fluid around the microstructure pattern and toward the outlet channel.

9. The microneedle device of any one of claims 1-8 further comprising peripheral channels in fluidic communication with the inlet channel and the outlet channel, the peripheral channels configured to receive fluid from the inlet channel, retain the fluid, and direct the fluid towards the outlet channel.

10. The microneedle device of any one of claims 1-9 further comprising: a cell analysis chambers in fluidic communication with the inlet channel, the crossflow filtration chamber, and the outlet channel, the cell analysis chambers configured to receive a controlled portion of cells in the fluid exited from the crossflow filtration channel for analysis of cellular biomarkers.

11. The microneedle device of claim 10, wherein the cell analysis chambers is further configured to receive a controlled portion of fluid filtered through the microstructure pattern of the crossflow filtration chamber and mix the filtered fluid with the controlled portion of cells.

12. The microneedle device of claim 10-11, wherein the cell analysis chambers includes an interior volume defined by cell analysis chamber microstructures spaced to control the mixing of the filtered fluid and cells so as to achieve an intentional dilution.

13. The microneedle device of any one of claims 1-12 further comprising: an analyte analysis chamber in fluidic communication with the interior volume of the crossflow filtration chamber, the analyte analysis chamber configured to receive a portion of the fluid excised from the crossflow filtration channel for analysis of analyte biomarkers.

14. The microneedle device of claim 13, wherein the analyte analysis chamber includes a reagent.

15. The microneedle device of claim 14, wherein the analyte analysis chamber includes a microstructure pattern configured to spatially control the deposition of the reagent and prevent unintended movement of the reagent out of the analyte analysis chamber.

16. The microneedle device of claim 15, wherein the analyte analysis chamber is configured to receive fluid filtered through the microstructure pattern of the crossflow filtration chamber.

17. The microneedle device of any one of claims 13-16, further comprising a reagent chamber configured to deliver a reagent to the analyte analysis chamber.

18. The microneedle device of any one of claims 10-17, further comprising a reagent chamber configured to deliver a reagent to the cell analysis chambers.

19. The microneedle device of any one of claims 13-18, wherein the analyte analysis chamber further includes a chemical agent detector paper, a glucose test paper, microbeads, and / or a litmus test paper.

20. The microneedle device of any one of claims 1-19, wherein the microfluidic substrate further includes: a second inlet channel configured to drive capillary movement of a second portion of the fluid across the second inlet channel; a second outlet channel configured to drive capillary movement of the second portion of the fluid across the second outlet channel; and a second crossflow filtration chamber having a second crossflow filtration channel in fluidic communication with the second inlet channel and the second outlet channel, the second crossflow filtration chamber configured to drive capillary movement of the second portion of the fluid across a second filtration boundary formed between the second crossflow filtration channel nd a second interior volume defined by a second microstructure pattern of the second crossflow filtration chamber.

21. The microneedle device of claim 20, wherein the second crossflow filtration channel directs the second portion of the fluid around the second microstructure pattern and toward the second outlet channel.

22. The microneedle device of any one of claims 20-21, wherein the inlet channel, outlet channel, and crossflow filtration channel collectively has a first path length, wherein the second inlet channel, second outlet channel, and second crossflow filtration channel collectively has a second path length, the first path length and the second path length being the same.

23. The microneedle device of any one of claims 20-21, wherein the inlet channel, outlet channel, and crossflow filtration channel collectively has a first path length, wherein the second inlet channel, second outlet channel, and second crossflow filtration channel collectively has a second path length, the first path length and the second path length being different.

24. The microneedle device of any one of claims 1-23, wherein the microfluidic substrate includes 1 testing channel, the testing channel comprising at least an inlet channel, a crossflow filtration chamber, and an outlet channel.

25. The microneedle device of any one of claims 1-23, wherein the microfluidic substrate includes 2, 3, 4, 5, 6, 7, or 8 testing channels.

26. The microneedle device of any one of claims 1-25, wherein a portion of the microfluidic substrate is transparent for a colorimetric test to be performed by the microneedle device.

27. The microneedle device of any one of claims 1-26, wherein the microfluidic substrate is configured to couple to a handheld test system.

28. The microneedle device of any one of claims 1-26, wherein the microfluidic substrate is configured to couple to a portable test system.

29. The microneedle device of any one of claims 1-26, wherein the microfluidic substrate is configured to couple to a bench-top test system.

30. The microneedle device of any one of claims 1-29, further comprising one or more electrodes integrated into the microfluidic substrate.

31. The microneedle device of claim 30, wherein the one or more electrodes are disposed over at least one of the crossflow filtration chamber, the analyte analysis chamber, the cell analysis chamber, and the outlet channel.

32. The microneedle device of any one of claims 30-31, wherein the one or more electrodes are interdigitated electrodes.

33. The microneedle device of any one of claims 1-32, wherein the microfluidic substrate further comprises one or more buffer channels configured to direct buffer solution into the inlet channel, thereby diluting fluid contained within the inlet channel.

34. The microneedle device of claim 33, wherein the one or more buffer channels comprise a plurality of buffer channels disposed on opposite sides of the inlet channel orthogonal to the inlet channel.

35. The microneedle device of any one of claims 33-34, wherein the microfluidic substrate further comprises a cell counting channel disposed subsequent to the one or more buffer channels.

36. The microneedle device of claim 35, wherein a plurality of parallel plate electrodes are disposed on opposite sides of the cell counting channel, wherein the parallel plate electrodes are configured to count a portion of cells in the fluid.

37. A cartridge device comprising: a microfluidic substrate comprising: an inlet channel configured to drive capillary movement of a fluid across the inlet channel; an outlet channel configured to drive capillary movement of the fluid across the outlet channel; and a crossflow filtration chamber having a crossflow filtration channel in fluidic communication with the inlet channel and the outlet channel, the crossflow filtration chamber configured to drive capillary movement of the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber.

38. The cartridge device of claim 37, wherein the crossflow filtration channel directs the fluid around the microstructure pattern and toward the outlet channel.

39. The cartridge device of any one of claims 30-38, wherein the inlet channel is configured to receive the fluid from a pipette.

40. The cartridge device of any one of claims 37-39 having the features of any one of claims 3-36.

41. A system comprising: the microneedle device or the cartridge device of any one of claims 1-40; andan analysis system having a plurality of sensors that is configured to interrogate the crossflow filtration chamber, the outlet channel, or a channel therebetween.

42. A method of filtering a fluid comprising: driving by capillary movement a fluid across an inlet channel; driving by capillary movement the fluid into a crossflow filtration chamber having a crossflow filtration channel in fluidic communication with the inlet channel and an outlet channel; driving by capillary movement the fluid across a filtration boundary formed between the crossflow filtration channel and an interior volume defined by a microstructure pattern of the crossflow filtration chamber; and driving by capillary movement the fluid across the outlet channel.

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