ANALYTE CAPTURING DEVICES WITH FLUIDIC EJECTION DEVICES

BACKGROUND

Analyte concentration is a sample preparation operation used in many chemical analysis operations. For example, concentration of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) is a sample preparation step in nucleic acid testing. Concentrating the analytes enhances the efficacy and accuracy of subsequent analysis operations.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various examples of the principles described herein and are part of the specification. The illustrated examples are given merely for illustration, and do not limit the scope of the claims.

FIGS. 1A-1C are diagrams of an analyte capturing device with fluid ejection devices, according to an example of the principles described herein.

FIG. 2 is a flow chart of a method for analyte capturing with fluid ejection devices, according to an example of the principles described herein.

FIGS. 3A-3C are diagrams of an analyte capturing device with fluid ejection devices, according to another example of the principles described herein.

FIG. 4 is a cross-sectional diagram of an analyte capturing device with fluid ejection devices, according to another example of the principles described herein.

FIG. 5 is a diagram of a method for analyte capturing with the fluid ejection devices, according to another example of the principles described herein.

FIG. 6 is a cross-sectional diagram of an analyte capturing device with fluid ejection devices, according to another example of the principles described herein.

FIG. 7 is a top view of an analyte capturing device with fluid ejection devices, according to another example of the principles described herein.

Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings.

DETAILED DESCRIPTION

Analyte concentration is a sample preparation operation in many chemical analysis operations. For example, concentration of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) is a sample preparation step in nucleic acid testing. Concentrating the analytes enhances the efficacy and accuracy of subsequent analysis operations.

There are various ways to concentrate an analyte. As a specific example, certain materials may have an affinity for an analyte and may therefore attract the analyte. Quantities of this material can be formed into microscopic beads and may be included in a solution to adsorb the analyte to the bead surface.

While using beads in solution is effective at separating the analyte, such systems present certain complications. For example, once drawn to the beads, the beads themselves should be separated from the rest of the solution such that the analyte may be removed. One way to separate the beads is magnetic gathering. In this method, the beads have a paramagnetic core and are pulled from the solution by an external permanent magnet. In another example, the beads are separated from the rest of the solution based on size differences. For example, a size of objects in a biological sample may be between 0.1-1.0 microns whereas the beads may be between 1-10 microns in diameter. Thus, if a mixture with the beads and analyte is passed through a filter with pore sizes of several microns, the beads will be trapped while the rest of the solution will pass through. Since at this stage, the analyte, such as DNA molecules, are still attached to the bead surface, trapping beads in a filter concentrates DNA.

While such operations are effective at concentrating an analyte within a solution, improved operations in this field would increase efficacy and subsequent operation accuracy. Accordingly, the present specification describes a system and method for concentrating analyte using analyte-adsorbing beads, and for separating the analyte-adsorbing beads from the rest of the sample fluid. Specifically, the present specification relies on fluid ejection devices and a mesoscopic fluid delivery chamber to capture the analyte-adsorbing beads.

The fluid ejection devices expel waste carrier fluid while the analyte is retained within a chamber. To eject the fluid, the fluid ejection devices include a number of components. Specifically, the fluid to be ejected is held in an ejection chamber. A fluid actuator operates to dispel the fluid in the ejection chamber through an opening. As the fluid is expelled, a negative capillary pressure within the ejection chamber draws additional fluid into the ejection chamber, and the process repeats. In this example, the ejection chamber has microscale dimensions. Fluid is fed to the ejection chamber via a fluid feed channel, which is larger, for example having mesoscale dimensions.

The chamber of the analyte capturing device has dimensions to accommodate beads having a diameter sufficiently large that they are trapped in the chamber and cannot enter the microfluidic passageways nor the ejection chamber. During operation, as the ejector actuates, the solution is pulled through the chamber where the beads are stored. As such, the analyte adheres to the surface of the beads and the rest of the solution, i.e., a carrier fluid, passes through to the ejection chamber to be expelled. Accordingly, as an entire sample is treated, the carrier fluid is expelled through the fluid ejection device and the analyte is left behind in the chamber. From here, the analyte can be subsequently ejected through the fluid ejection device onto a surface or into a container. In another example, the analyte is routed to another chamber where it can be further analyzed.

Specifically, the present specification describes an analyte capturing device. The analyte capturing device includes a first substrate having microfluidic channels disposed therein and a second substrate disposed on top of the first substrate. In this example, a chamber is disposed through the second substrate to capture beads therein. The beads may adsorb analytes. The device also includes at least one fluid ejection device disposed in the first substrate to draw an analyte-containing solution through the beads disposed within the chamber.

The present specification also describes a method. According to the method, beads that adsorb analytes are captured in a mesofluidic chamber of an analyte capturing device. A microfluidic fluid ejection device is activated to generate a flow through the mesofluidic chamber and a carrier fluid is expelled from the analyte capturing device.

In another example, the analyte capturing device includes a planar microfluidic substrate having microfluidic channels disposed therein and a planar silicon substrate disposed on top of the planar microfluidic substrate. The analyte capturing device also includes at least one mesoscale chamber disposed through the planar silicon substrate to capture beads therein, which beads are to adsorb analytes. The analyte capturing device also includes microscale fluid ejection devices disposed in the planar microfluidic substrate to draw an analyte-containing solution through the beads disposed within the chamber. In this example, each fluidic ejection device includes 1) an ejection chamber to hold a volume of fluid, 2) an opening, and 3) an ejector to eject a portion of the volume of fluid through the opening.

In summary, using such an analyte capturing device 1) enables analyte concentration via analyte-adsorbing beads; 2) enables separation of the beads with adhered analyte thereon from a carrier fluid; 3) includes a mesoscale volume to hold the analyte-adsorbing beads, the larger volume allowing for a greater quantity of analyte-adsorbing beads; and 4) facilitates the user of larger analyte-adsorbing beads, reducing the fluidic resistance of the system and thus enhancing the analyte concentration operation. However, the devices disclosed herein may address other matters and deficiencies in a number of technical areas.

As used in the present specification and in the appended claims, the term “fluid ejection device” refers to an individual component of the analyte capturing device that ejects fluid. The fluid ejection device may be referred to as a nozzle and includes at least an ejection chamber to hold an amount of fluid and an opening through which the fluid is ejected. The fluid ejection device also includes an ejector disposed within the ejection chamber.

Further, as used in the present specification and in the appended claims, the term “meso-” refers to a size scale of 100-1000 microns. For example, a mesofluidic layer may be between 100 and 1000 microns thick.

Further, as used in the present specification and in the appended claims, the term “micro-” refers to a size scale of between 10 and 100 microns. For example, a microfluidic layer may be between 10 and 100 microns thick and a microfluidic channel may have a cross-sectional diameter of between 10 and 100 microns.

Turning now to the figures, FIGS. 1A-1C are diagrams of an analyte capturing device (100) with fluid ejection devices (106), according to an example of the principles described herein. Specifically, FIG. 1A is a top view of the analyte capturing device (100), FIG. 1B is a cross-sectional view of the analyte capturing device (100) without analyte-adsorbing beads disposed therein, and FIG. 1C is a cross-sectional view of a portion of the analyte capturing device (100) with analyte-adsorbing beads disposed therein. While FIGS. 1A-1C depict multiple columns to eject waste fluid, in some examples, the fluid may be passed downstream for further processing as depicted in FIG. 4 through some or all of the columns.

As described above, the analyte capturing device (100) relies on fluid ejection devices (106) for capturing analytes therein. For simplicity in FIG. 1A, just one of the fluid ejection devices (106) is indicated with a reference number. The analyte capturing device (100) also includes a chamber (104). It is in this chamber (104) that analyte-adsorbing beads are captured. That is, a solution including 1) an analyte such as DNA and 2) analyte-adhering beads that attract the analyte are received in the chamber (104). In some examples, the size scale of the chamber (104) and the fluid ejection devices (106) are different. For example, the chamber (104) may be on a mesoscale, meaning it may be formed through a substrate (102) with a thickness between 100 and 775 microns. The fluid ejection devices (106) by comparison are on a microscale, meaning they may be formed in a separate substrate with a thickness of between 10 and 100 microns. In FIG. 1A, the fluid ejection devices (106) are indicated in a dashed line indicating their placement below the substrate (102) in which the mesofluidic bead-capturing chamber (104) is formed.

FIG. 1B is a cross-sectional diagram of the analyte capturing device (100), and more specifically, a cross-sectional diagram taken along the line A-A in FIG. 1A. FIG. 1B clearly shows the first substrate (108) in which the fluid ejection device(s) (106-1, 106-2) are formed. In some examples, the first substrate (108) may be formed of a polymeric material such as SU-8. As described above, the fluid ejection devices (106), and the first substrate (108) in which it is formed, may be microscopic. That is, the first substrate (108) may have a thickness of between 10 and 100 microns. In some examples, the first substrate (108) may be planar and may be referred to as a microfluidic substrate due to its containing microfluidic structures.

To facilitate the ejection of fluid, each fluid ejection device (106) includes various components. For example, fluid ejection devices (106-1, 106-2) include an ejection chamber (112-1, 112-2) to hold an amount of fluid to be ejected, openings (114-1, 114-2) through which the amount of fluid is ejected, and ejectors (110-1, 110-2), disposed within the ejection chambers (112), to eject the amount of fluid through the openings (114-1, 114-2).

Turning to the ejectors (110), the ejector (110) may include a firing resistor or other thermal device, a piezoelectric element, or other mechanism for ejecting fluid from the ejection chamber (112). For example, the ejector (110) may be a firing resistor. The firing resistor heats up in response to an applied current. As the firing resistor heats up, a portion of the fluid in the ejection chamber (110) vaporizes to generate a bubble. This bubble pushes fluid through the opening (114). As the vaporized fluid bubble collapses, fluid is drawn into the ejection chamber (112) from a passage that connects the fluid ejection device (106) to the bead-capturing chamber (104), and the process repeats. In this example, the fluid ejection device (106) may be a thermal inkjet (TIJ) fluid ejection device (106).

In another example, the ejector (110) may be a piezoelectric device. As a voltage is applied, the piezoelectric device changes shape which generates a pressure pulse in the ejection chamber (112) that pushes the fluid out the opening (114). In this example, the fluid ejection device (106) may be a piezoelectric inkjet (PIJ) fluid ejection device (106).

Disposed on top of the first substrate (108) is a second substrate (102). The second substrate (102) may be formed of a different material, such as silicon. The second substrate (102) defines in part the chamber (104) through which the solution is passed and in which the beads are captured. In some examples, the second substrate (102) may be planar and may be referred to as a silicon substrate due to its being formed of a silicon material.

The chamber (104) may take many forms. For example, as depicted in at least FIG. 1B, the chamber (104) may be a slot and may be funnel-shaped. The slot may be fluidly coupled to multiple fluid ejection devices. In another example, as depicted in FIGS. 3A-3C, the bead-capturing chamber (104) may include multiple fluid delivery holes beneath the slot, which holes are coupled to multiple fluid ejection devices (106).

The second substrate (102) and the associated chamber (104) may be on the mesoscale. That is, a thickness of the second substrate (102) may be between 100 and 775 microns thick, and the chamber (104) may have a volume of between 0.01 microliter and 10 microliters, Being on the mesoscale, the chamber (104) can capture larger analyte-adhering beads and can retain a higher quantity of the analyte-adhering beads, both of which increase the efficiency of analyte concentration as described below.

Moreover, the analyte capturing device (100), by using inkjet components such as ejection chambers (112), openings (114), and ejectors (110) disposed within the ejection chambers (112), enables low-volume dispensing of fluids.

FIG. 1C is a cross-sectional diagram of the analyte capturing device (100) taken along the line A-A in FIG. 1A and depicts the flow of an analyte-containing solution through the analyte capturing device (100). As described above, a solution is loaded into the analyte capturing device (100) and fills the chamber (104). The analyte-adhering beads (116) having a diameter greater than the microfluidic channels in the first substrate (108) cannot pass to the microfluidic section and therefore aggregate in the chamber (104).

As described above, the beads (116) are components that draw, or adsorb, the analyte to their surface. For example, the beads (116) may be formed of silica, alumina, a polymer, or other material. The beads (116) may or may not have a surface treatment that draws the analyte. The surface treatment may be specific to the analyte of interest. For example, amino groups could be added to the surface of the beads (116). These amino groups acquire a proton and thereby become positively charged, making them attractive to negatively charged DNA molecules.

In another example, complex proteins may be added to the beads (116) with complementary proteins on the analyte. As such, the proteins will attract one another and the analyte will aggregate on the beads (116). In some examples, the analyte-adhering beads (116) may have a diameter of between 5 and 20 microns, which may be larger than the diameter of the microfluidic channels.

In one example, the activation of the fluid ejection device (106) creates a fluid flow past the analyte-adsorbing beads (116). As the solution passes the beads (116), analyte is captured therein, and the remaining solution may be expelled as waste through the opening (114) of the fluid ejection device (106). In another example, a carrier fluid includes the beads (116). In this example, adsorption of the analyte on the beads (116) occurs upstream. In this example, the beads (116) are captured in the chamber (104), and the fluid ejection devices (106) work to expel waste fluid. That is, in either example, the analytes in the solution are separated from the carrier fluid.

In some examples, the solution may include a lysis buffer which breaks down the cell membrane/walls such that the analyte in the cell can be collected. In this example, the lysis solution forms part of the carrier fluid that is expelled through the fluid ejection device (106).

Once separated from the carrier fluid, the analyte can then be passed downstream. For example, once all the carrier fluid has been removed, an elution buffer can be passed through the chamber (104). The elution buffer works to break down the bonds that adhere the analyte to the beads (116). The fluid ejection device (106) can then be activated again to draw fluid, i.e., the elution buffer with analyte, from the chamber (104) and out the opening (114) onto a desired surface, or into another chamber of a larger system wherein the analyte can be further analyzed.

Accordingly, the present analyte capturing device (100) provides a large volume, i.e., on the order of 0.01 to 10 microliters, where analyte-adhering beads (116) are captured to filter out the analyte from the rest of the solution. Using such a large volume enables the capturing of more beads (116). More captured beads (116) increases the overall ability to capture analytes from the solution. The larger volume also enables the use of larger analyte-adhering beads (116), such as those having a diameter of between 5-20 microns. Larger analyte-adhering beads (116) reduce the fluidic resistance of the system. That is, smaller analyte-adhering beads (116) packed more tightly together increase the fluid resistance such that greater pressures are needed to drive the fluid through the volume. By comparison, larger analyte-adhering beads (116) reduce the fluid resistance, such that less pressure is required to drive the fluid. Using a lower pressure 1) may increase the longevity and throughput of the system, 2) is less complex, and 3) allows the use of smaller, less invasive driving mechanisms.

FIG. 2 is a flow diagram of a method (200) for analyte capturing with the analyte capturing device (FIG. 1A, 100), according to another example of the principles described herein. According to the method, analyte-adsorbing beads (FIG. 1C, 116) are received (block 201) into a mesofluidic bead-capturing chamber (FIG. 1A, 104). That is, as described above an analyte capturing device (FIG. 1A, 100) includes a chamber (FIG. 1A, 104) that is on a mesoscale. As a specific example, the second substrate (FIG. 1, 102) in which the chamber (FIG. 1A, 104) is formed may have a thickness of between 100 and 775 microns. A reservoir of fluid feeds fluid to this chamber (FIG. 1A, 104). The fluid in the reservoir may be a solution that includes an analyte, a carrier fluid, and analyte-adsorbing beads (FIG. 1C, 116) that draw the analyte from the solution.

The microfluidic ejection device (FIG. 1A, 106) is then activated. Doing so generates (block 202) flow through the mesofluidic chamber (FIG. 1A, 104).

With a flow generated (block 202), the carrier fluid can be expelled (block 203). That is, the operation of the microfluidic ejection device (FIG. 1A, 106) expels the waste fluid, i.e., the carrier fluid and extraneous components, out of the analyte capturing device (FIG. 1A, 100). Such expelling may be onto a waste surface or into a waste container.

The method (200) as described herein allows for the separation of analyte from the carrier fluid. Specifically, the carrier fluid is expelled as waste and the analyte is retained by the beads (FIG. 1C, 116). Such a separation increases the concentration of the analyte for further analysis. Accordingly, the analyte capturing device (FIG. 1A, 100) as described herein provides a simple and effective way to separate, and concentrate an analyte within a solution.

FIGS. 3A-3C are diagrams of an analyte capturing device (100) with fluid ejection devices (106), according to another example of the principles described herein. Specifically, FIG. 3A is a top view of the analyte capturing device (100) and FIGS. 3B and 3C are cross-sectional views of the analyte capturing device (100).

In this example, the analyte capturing device (100) includes the second substrate (102) in which a bead-capturing chamber (104) is formed and also includes fluid ejection devices (106). However, in this example, the bead capturing chamber (104) includes multiple bead-capturing holes (318) disposed beneath the chamber (104). For simplicity, a single instance of a bead-capturing hole (318) is indicated with a reference number. The bead-capturing holes (318) serve to capture the analyte-adsorbing beads (FIG. 2, 116) as fluid flows therethrough. The additional material between the holes (318) may add to the mechanical rigidity of the second substrate (102). For example, when the second substrate (102) is thinner, it may be more susceptible to mechanical failure. Accordingly, the material between the holes (318) increase the rigidity of the second substrate (102). In this example, the holes (318) may be any size, for example between tens of microns to a few hundred microns. Moreover, while FIG. 3A depicts a particular orientation of certain holes (318) with a certain diameter. Any number, any orientation, and any-sized holes (318) may be used, in some examples with the holes (318) having different sizes.

FIG. 3B is a cross-section of the analyte capturing device (100) depicted in FIG. 3A. Specifically, FIG. 3B is a cross-sectional diagram taken along the line B-B in FIG. 3A. FIG. 3B clearly depicts the holes (318-1, 318-2) as they feed multiple fluid ejection devices (106-1, 106-2). Feeding multiple fluid ejection devices (106) via mesofluidic holes (318) may allow for faster solution processing, That is, rather than passing fluid to just one fluid ejection device (106), fluid can be passed to multiple fluid ejection devices (106-1, 106-2). While FIG. 3B depicts two holes (318-1, 318-2) passing solution to two fluid ejection devices (106-1, 106-2), each hole (318) may be coupled to any number of fluid ejection devices (106). The holes (318) may be of any size, for example, the holes (318) may have diameters of between 5 and 80 microns. In this example, as has been described above, the beads (116) may be sized such that they cannot pass into the microfluidic structures of the first substrate (108).

FIG. 3C depicts yet another example using holes (318) coupled to the chamber (104). In this example, a thin silicon membrane (320) is placed at the bottom of the chamber (104). This membrane (320) is perforated such that fluid may pass through, but the beads (116) do not on account of their larger diameter. Use of the membrane (320) as described herein maintains the beads (116) further away from the microscopic fluid ejection devices (106) such that they do not impede the flow of fluid into, or through, the microfluidic structures. In some examples, the membrane (320) may be formed of a silicon material or SU8 and may be between 3 and 20 micrometers thick.

FIG. 4 is a cross-sectional diagram of an analyte capturing device (100) with fluid ejection devices (106), according to another example of the principles described herein. As in examples above, the analyte capturing device (100) includes a first substrate (108), a second substrate (104), a bead-capturing chamber (104), and fluid ejection device(s) (106). In this example, the analyte capturing device (100) further includes an analyte channel (422) in the first substrate (108). Through this analyte channel (422), the analyte, following capture, is passed to another component of the fluid analytic system. For example, once the carrier fluid has been expelled, the elution buffer described above is inserted into the bead-capturing chamber (104) to remove the analyte from the analyte-adsorbing beads (116), This may be done by, for example, altering the pH, changing electrical charge, and/or heating the beads (116).

In this example, a driving mechanism can direct the fluid flow through the analyte chamber (422) as opposed to the fluid ejection device (106). For example, a pump may be disposed at some point along the analyte chamber (422), or in some examples, at the end of the analyte chamber (422). At a predetermined time, this pump or other driving mechanism could be activated to draw the analyte and elution buffer through the analyte channel (422) and away from the fluid ejection device (106). In one specific example, the fluid may be drawn to another chamber or component to further analyze and/or process the fluid. Doing so may be beneficial in that it does not expose the analyte to environment conditions, which may tarnish or otherwise contaminate the analyte.

FIG. 5 is a diagram of a method (500) for analyte capturing with the analyte capturing device (FIG. 1A, 100), according to another example of the principles described herein. According to the method (500), analyte-adsorbing beads (FIG. 1C, 116) are received (block 501) in a mesofluidic bead-capturing chamber (FIG. 1A, 104) and a flow generated (block 502). Excess carrier fluid is then expelled (block 503) out of the analyte capturing device (FIG. 1A, 100). These operations may be performed as described above in connection with FIG. 2.

Then, as described above, the analyte may be separated from the analyte-adsorbing beads (FIG. 1C, 116). This may be performed by drawing (block 504) an elution buffer through the analyte-adsorbing beads (FIG. 1C, 116), which at this stage have analytes adhered thereon. As described above, the elution buffer breaks down the bonds that adhere the analyte to the analyte-adsorbing beads (FIG. 1C, 116).

Following removal from the analyte-adsorbing beads (FIG. 1C116), the analyte is then drawn (block 505) from the bead-capturing chamber (FIG. 1A, 104). This may occur in a number of different ways. For example, the fluid ejection device (FIG. 1A, 106) could be activated to expel the analyte and the elution buffer from the analyte capturing device (FIG. 1A, 100) through the opening (FIG. 1B, 114). In this example, such an operation may be conducted after the entirety of the carrier fluid has been expelled. Such an example may allow for the analyte to be deposited on any type of surface or container that is external and separate from the analyte capturing device (FIG. 1A, 100).

In another example, a chamber pump, or some other driving mechanism is activated to draw (block 505) the analyte and elution buffer from the bead-capturing chamber (FIG. 1A, 104) through an analyte channel (FIG. 4, 422). In this example, the analyte may travel to another component of the analyte processing system. Using an analyte channel (FIG. 4, 422) in this fashion, prevents the analyte from contact with the environment or users, which may be undesirable.

FIG. 6 is a cross-sectional diagram of an analyte capturing device (100) with fluidic ejection devices (106), according to another example of the principles described herein. As in other examples, the analyte capturing device (100) includes a first substrate (108) with a fluid ejection device (106) formed therein and a second substrate (102) with a bead-capturing chamber (FIG. 1A, 104) formed therein. In this example, the analyte capturing device (100) includes a third substrate (624) having an opening larger than the bead-capturing chamber (FIG. 1A, 104), This third substrate (624) opening allows for even a greater volume into which analyte-adsorbing beads (116) are collected. That is, the bead-capturing chamber (FIG. 1A, 104) by itself may have a volume of 0.01 to 10 microliters. In this example, the size and shape of the opening in the third substrate (624) may increase the volume to upwards of 100 microliters. The increased volume allows for an even larger quantity of analyte-adsorbing beads (116) to be captured therein and further reduces the fluidic resistance as the beads (116) may be less tightly packed. In some examples, the third substrate (624) may be formed of any material including another silicon layer, a plastic, a ceramic, or a composite layer.

FIG. 7 is a top view of an analyte capturing device (100), according to another example of the principles described herein. To accommodate the capture of more beads (FIG. 1C, 116) thus even further increasing the efficacy of analyte concentration, the analyte capturing device (100) may include multiple bead-capturing chambers (104). While FIG. 7 depicts two bead-capturing chambers (104-1, 104-2), the analyte capturing device (100) may include any number of bead-capturing chambers (104). Using multiple bead-capturing chambers (104) also increases the flow rate of the solution through the analyte capturing device (100), which increased flow rate also decreases processing times.

In some examples, the different chambers (104-1, 104-2) may have different dimensions, shapes, and/or profiles. Using chambers (104-1, 104-2) with different parameters increases the customization available on an analyte capturing device (100). For example, the different chambers (104-1, 104-2) may be used to analyze different solutions. Thus, the present analyte capturing device (100) provides for customized and tailored chemical analysis.

ANALYTE CAPTURING DEVICES WITH FLUIDIC EJECTION DEVICES

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