BACKGROUND

[0001] Analytic chemistry is a field of chemistry that uses instruments to separate, identify, and quantify matter. In analytic chemistry, the fluid to be analyzed, or components therein are measured, chemically processed, and/or physically manipulated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] 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.

[0003] Fig. 1 is a flow chart of a method of forming fluid structures via removing sacrificial structures, according to an example of the principles described herein.

[0004] Figs. 2A-2H depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. [0005] Figs. 3A and 3B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein.

[0006] Figs. 4A and 4B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. [0007] Figs. 5A and 5B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein.

[0008] Figs. 6A and 6B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein.

[0009] Figs. 7A and 7B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein.

[0010] Figs. 8A and 8B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein.

[0011] Figs. 9A and 9B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein.

[0012] Fig. 10 is a flow chart of a method of forming fluid structures via removing sacrificial structures, according to an example of the principles described herein.

[0013] Fig. 11 is a block diagram of a multi-layered fluid analysis device, according to an example of the principles described herein.

[0014] Fig. 12 depicts a multi-layered fluid analysis device, according to an example of the principles described herein.

[0015] Fig. 13 depicts a multi-layered fluid analysis device, according to an example of the principles described herein.

[0016] Fig. 14 depicts a multi-layered fluid analysis device, according to an example of the principles described herein.

[0017] Fig. 15 depicts a polymerase chain reaction (PCR) chamber fluid structure, according to an example of the principles described herein.

[0018] Fig. 16 depicts an electrophoresis chamber fluid structure, according to an example of the principles described herein.

[0019] Fig. 17 depicts a droplet forming chamber fluid structure, according to an example of the principles described herein. [0020] Fig. 18 depicts a lysis chamber fluid structure, according to an example of the principles described herein.

[0021] Fig. 19 depicts a dry reagent storage chamber fluid structure, according to an example of the principles described herein.

[0022] 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

[0023] In analytic chemistry, fluid and its constituent components are transported and acted upon in a variety of ways. According to the present specification, these processes can be performed on devices such as a lab-on-a- chip device. In some examples, these lab-on-a-chip devices are microfluidic, meaning they transport micro-quantities of fluid.

[0024] In some examples, microfluidic chips may be made with injection molded thermoplastic materials such as cyclic olefin copolymer (COC) or polycarbonate (PC) materials. However, the microfluidic structures may 1) be two dimensions in nature, 2) be bulky, and 3) not include any electrical connections. Accordingly, to form the electrical interconnects, a single metal layer may be added on top of the COC substrate, or metal leads can be insert- molded into the COC substrate. However, such operations are complex, costly, and may be structurally unsound. In addition, injection molded lead frames lend themselves to low lead count and relatively larger minimum feature sizes of greater than 100 micrometers for molded features and greater than 200 micrometers for lead wire pitch.

[0025] Accordingly, the present specification describes the formation of microfluidic structures in a microfluidic analysis device using sacrificial copper. Using this method, electrical connections may be integrated into the device during formation. In some examples a sensor die may be embedded in the fluid analysis device. Using the method of the present specification, fluid structures on multiple layers may be aligned to form three-dimensional fluid structures. [0026] According to such a method, sacrificial copper may be used to define the fluid structures or other microfluidic components (such as reaction chamber, filter, mixer, through mold via, I/O port, and so on). The sacrificial copper is etched away to form fine-pitch microfluidic channels or structures. As described above, multiple layers may be stacked and sensor die may be embedded between the layers. A glass or plastic lid can be attached to the device to form a sealed package.

[0027] Specifically, the present specification describes a method of forming a fluid analysis device. According to the method, sacrificial structures that define fluid structures to be formed on the fluid analysis device and interconnect structures that define electrical interconnects to be formed on the fluid analysis device are formed on a surface. The structures are embedded in a plastic compound and multiple layers of plastic compound embedded with structures are stacked. The fluid structures are formed by removing the sacrificial structures.

[0028] In one example, a mask is placed over the interconnect structures. Removing the sacrificial structures may include wet etching the sacrificial structures.

[0029] In an example, forming structures on a surface and positioning a plastic compound over the structures are performed in a layer-wise fashion. In an example, the method includes embedding a sensor die between adjacent layers of plastic compound embedded with structures.

[0030] In an example, forming sacrificial structures and interconnect structures includes patterning a plating resist layer on a surface. Removed portions of the plating resist layer correspond to sacrificial structures and interconnect structures. Copper is plated in the patterns formed by the plating resist and the plating resist material is removed. In some examples, the sacrificial structures and interconnect structures are formed simultaneously with a same compound. [0031] The present specification also describes a multi-layered fluid analysis device. The fluid analysis device includes multiple layers of a plastic compound and a number of fluid structures sacrificially-formed in the multiple layers. At least one fluid structure spans across at least two layers. The multi-layered fluid analysis device includes a sensor die embedded between adjacent layers. [0032] In an example, the substrate is a molded interconnect substrate. In an example, fluid structures are formed on both surfaces of the multi-layered fluid analysis device. At least one fluid structure is a fluid channel which exposes the sensor die to a fluid introduced to the fluid analysis device.

[0033] The multi-layered fluid analysis device may include an electrical trace embedded in a layer to electrically couple the sensor die to a surface of the multi-layered fluid analysis device.

[0034] The number of fluid structures may be selected from the group consisting of: channels, embedded channels, post filters, mechanical filters, through holes, reservoirs, fluid ports, rupture devices, crossing channels, embedded crossing channels, a sensor die recess, a PCR chamber, an electrophoresis chamber, a lysis chamber, a droplet-forming chamber, and a dry reagent storage chamber.

[0035] According to another method, multiple layers of plastic compound embedded with structures are stacked. The structures include sacrificial structures that define fluid structures to be formed on the fluid analysis device and interconnect structures that define electrical interconnects to be formed on the fluid analysis device. At least one sacrificial structure spans at least two layers of molded plastic. A sensor die is embedded between adjacent layers of plastic compound. A mask is placed over the interconnect structures and the sacrificial structures are etched away to form a multi-layer fluid routing path. [0036] In an example, sacrificial structures of multiple layers are simultaneously etched. In an example, the method further includes, for each layer, simultaneously forming the sacrificial structures and interconnect structures in a layer-wise fashion.

[0037] The present method, instead of using an injection molded COC microfluidic substrate, starts with a substrate such as a molded interconnect substrate (MIS). In addition to the electrical routing, copper may be used as a sacrificial material to define the fluid channels, I/O, reaction chambers, and other microfluidic components. As described above, the sacrificial copper is later removed with photolithography and etching. Using such a method, a highly-precise microfluidic substrate with fully-integrated micro fluid channels and electrical routing can be formed. The precision and narrow pitch capability of the fluid channels afforded by this method is greater than what can be achieved with an injection molded substrate.

[0038] Moreover, the current method supports multi-layer complex electrical routing and offers high precision electrodes to perform various microfluidic operations, such as digital microfluidic (DMF) analysis, electrophoresis, capacitance sensing, etc. That is, the present methods and device are three- dimensional (3D) in nature and enable multi-layer fluid routing. In other words, the present systems and methods provide fluidic routing along a third axis, i.e. , a z-axis, as compared with injection molded part.

[0039] The systems and methods of the present specification 1) provide high precision and fine pitch fluidic routing capability; 2) support multi-layer fluidic routing layers; 3) are compatible with IC packaging technologies; 4) provide a system-in-package platform for life sciences application; 5) allow for creation of complex electrical routings; 6) are low cost and have a fast turnaround; and 7) support a variety of microfluidic functions.

[0040] Turning now to the figures, Fig. 1 is a flow chart of a method (100) of forming fluid structures via removing sacrificial structures, according to an example of the principles described herein. That is, electrical interconnects, which may be formed out of a metallic material such as copper, and fluid structures may be formed at the same time. This may be done by forming interconnect structures, which form the electrical connections, and sacrificial structures, which will be etched away to form the fluid channels. In some examples, both structures, i.e., the interconnect structures and the sacrificial structures, may be formed of the same material, which may be copper.

[0041] Accordingly, the method (100) begins with forming (block 101) on a surface, both 1) the sacrificial structures, which define fluid structures to be formed on the fluid analysis device and 2) the interconnect structures, which define electrical interconnects to be formed on the fluid analysis device. In some examples, the surface may be a carrier substrate such as silicon, glass, plastic, steel, copper, or any other rigid material such as a printed circuit board. [0042] In one example, forming (block 101) the sacrificial structures and the interconnect structures is done in a layer-wise operation. That is, the sacrificial structures and the interconnect structures themselves may be formed of sub-layers, each sub-layer including regions that when stacked form the sacrificial structures and the interconnect structures.

[0043] In one example, this may be done via an additive process wherein a plating resist pattern is formed and copper is added to a pattern formed by the plating resist material. That is, a plating resist material, which may be a polymer material, is patterned on a surface for example using photolithography. During such patterning, a portion of a plating resist material is removed. That is, a mask may be placed over those portions of the layer of polymer material that are to be preserved and the plating resist material may be exposed to energy such as ultraviolet energy or a laser energy. The energy causes certain portions of the plating resist material to be removed. The removed portions correspond to the sacrificial structures and interconnect structures.

[0044] A copper material is then plated such that it fills the removed portions of the plating resist material. In some examples, the copper plating may rise above the level of the plating resist material, in which case excess copper may be ground. The plating resist material may then be stripped for example, by a solvent or alkaline solution. Examples of solvent stripping agents include 1-methyl-2-pyrrolidone and dimethyl sulfoxide and examples of alkaline stripping agents include diluted potassium hydroxide (KOH), sodium hydroxide or a combination thereof, leaving a portion of a copper structure.

[0045] Accordingly, a first sub-layer is formed of a plating resist material with copper embedded therein. This operation may be performed for a second sub-layer, potentially with copper in a different pattern. After a number of cycles, a full copper structure is defined, which copper structures define the sacrificial structures and the interconnect structures. [0046] In another example, the formation (block 101 ) of the sacrificial structures and interconnect structures may be done via a subtractive method, wherein a copper material is removed to form the sacrificial structures and the interconnect structures. In this example, a sub-layer of copper film is placed on a surface, a mask is placed over regions of the sub-layer that correspond to sacrificial structures and over regions of the sub-layer that correspond to interconnect structures. An etchant is applied to the sub-layer such that just those regions remain that correspond to either the sacrificial structures or the interconnect structures. For example, a photomask may be placed over those regions of the copper film that correspond to either of the sacrificial structures or the interconnect structures. The copper not under a photomask is then etched away such that upon removal of the photomask layer, just the sacrificial structures and the interconnect structures remain.

[0047] The structures, that is both the sacrificial structures and the interconnect structures, are embedded (block 102) in a compound. For example, a compound such as epoxy mold compound in liquid form is poured over the structures. The epoxy mold compound may then be cured to form a solid mass around the structures. Ultimately, the epoxy mold compound serves as a mechanical protection for the electrical interconnect, and is to form walls of fluid structures.

[0048] Multiple of these layers of the compound with embedded structures are then stacked (block 103). That is, each layer of a fluid analysis device includes embedded structures that either will be etched away to form fluid structures or that will be retained to form electrical interconnects. By stacking (block 103) multiple layers, fluid structures that span multiple layers may be formed. Accordingly, the present method (100) provides for multi layered, or three-dimensional, fluid structures where other techniques for forming microfluidic devices may only be two-dimensional, i.e., fluid flows just in one plane as opposed to in multiple planes.

[0049] The fluid structures are then formed (block 104) by removing the sacrificial structures. That is, copper that fills the layers and is intended to be a fluid structure is removed, for example via wet etching. Copper that is to form the electrical interconnects by comparison is preserved, for example by placing a mask on top of interconnect structures. Accordingly, the present specification describes a multi-layered approach to form three-dimensional fluid analysis devices, which approach forms such fluid structures simultaneously with the electrical interconnects.

[0050] Figs. 2A-2H depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. As depicted in Fig. 2A and as described above, a pattern of a plating resist layer (207) may be formed on a substrate (202) to start forming structures. In some examples, the substrate (202) may include a copper plated stainless-steel carrier.

[0051] Forming the pattern may include placing a mask over regions of a plating resist material (207) that do not correspond to either sacrificial structures or interconnect structures and removing the plating resist material (207) that is not underneath the mask. Doing so results in a pattern where removed material corresponds to either sacrificial structures or interconnect structures.

[0052] Copper may then be filled into these portions as depicted in Fig.

2B to form a first sub-layer of the structures (208), which structures (208) may be either sacrificial structures or interconnect structures. In some examples, the copper is filled via electroplating where the structure is placed in a bath and copper is attracted to gaps in the plating resistor layer (207).

[0053] As depicted in Fig. 2C, the plating resist material (207) may be removed, for example, applying a solvent-based or alkaline-based stripping agent. As a result, a portion of the structures (208) remain.

[0054] As depicted in Fig. 2D, the first sub-layer (204-1) may be filled with a compound (210) such as epoxy mold compound, the surface ground to expose the copper structures (208), and this process may be repeated multiple times to generate multi-layer copper structures with at times complex geometries. That is, as depicted in Fig. 2D, a second pattern of plating resist material (207) may be formed on the first sub-layer (204-1). That is, a layer of rigid plating resist material (208) may be laminated over the first sub-layer (204- 1). Copper may be plated throughout this pattern layer to form a second sub layer (204-2) as depicted in Fig. 2E.

[0055] The plating resist material may be removed. For example, a solvent-based or alkaline-based solution may be used to remove the plating resist material, leaving just the structures (208) that are to form the fluid structures and electrical interconnects. As depicted in Fig. 2F, the compound (210) may be added over the copper structures to form a second sub-layer. [0056] The compound (210)/structure (208) layer (218) forms a portion of the multi-layered fluid structures and electrical connects of a fluid analysis device. That is, Figs. 2A - 2F depict a process to form a layer (218) of plastic compound with embedded structures (208).

[0057] With the structures (208) fully defined and encased in plastic compound (210), certain of the structures (208) are etched away to form the fluid structures. Accordingly, a mask (206) is placed over those structures (208) that define electrical interconnects, i.e. , the interconnect structures while those structures (208) that are to define fluid structures, i.e., sacrificial structures, are exposed as depicted in Fig. 2G.

[0058] Accordingly, as depicted in Fig. 2H following wet etching of the sacrificial structures that pertain to fluid structures and removal of the photomask (206), the fluid structure is formed, which in this example is a fluid channel (212) through which fluid may flow. By comparison, those structures (208) that were protected by the photomask (206), i.e., the interconnect structures, remain as electrical interconnects (314). The plastic compound (210) which lines the sacrificial structures remains to define the walls of the fluid structures.

[0059] In some examples, the etchant that may be used to remove the sacrificial structures may be nitric acid, saturated 30% with ferric chloride. Other examples of etchants include ammonium hydroxide, hydrogen peroxide, nitric acid, hydrochloric acid or combinations thereof.

[0060] Accordingly, as the structures (208) were ultimately defined by multiple layers of compound (210) with embedded structures (208), multiple layers of the compound (210) with embedded sacrificial structures are simultaneously etched. Moreover, as each layer includes both sacrificial structures and interconnect structures, these structures may be simultaneously formed.

[0061] As described above, the sacrificial use of copper to form fluid structures allows for numerous types of fluid structures to be formed. Figs. 3A - 9B depict various examples of such structures.

[0062] Figs. 3A and 3B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. As depicted in Fig. 3A, different layers (Fig. 2G, 218) of compound (210) embedded with structures may be stacked to form structures (208) that either are to form electrical interconnects or fluid channels. As described above in regards to Figs. 2A - 2F, each layer (Fig. 2G, 218) may be formed of sub-layers (Fig. 2E, 204). That is, forming the complex geometry of an individual layer (Fig. 2G, 218) may include stacking different sub-layers (Fig. 2E, 204) to get the complex geometry of an individual plastic compound layer (Fig. 2G, 218). As depicted in Fig. 3A, various layers (Fig. 2G, 218), indicated in dashed lines in Figs. 3A and 3B, may form a monolithic substrate without any adhesive used between adjacent layers (Fig. 2G, 218).

[0063] Then as depicted in Fig. 3B, certain of the structures (208), i.e. , the sacrificial structures, are etched to form fluid structures, an example of which is a fluid channel (212) with those remaining portions forming electrical interconnects (314). As depicted in Fig. 3B, such a method allows for the simultaneous formation of electrical interconnects (314) via a photomask (206) and fluid structures such as fluid channels (212) during a single etching operation. That is, sacrificial copper is removed to expose the fluid channels (212) while portions of the copper remain for electrical routing operations. A variety of fluid structures may be formed using this method. For example, as depicted in Fig. 3B, one such fluid structure is a fluid channel (212). The figures that follow depict a variety of other fluid structures that may be formed.

[0064] Figs. 4A and 4B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. As described above, using the methods described herein, a fluid analysis device may include any variety of fluid structures. Figs. 4A and 4B depict some examples of fluid structures. For example, a fluid structure may be a through hole (420). Fig. 4B depicts two through holes, a first through hole (420-1) with a single inlet on each surface and a second through hole (420-2) that includes two inlets on one surface and a single opening on another surface. [0065] Another example of a fluid structure is a reservoir (422). Fig. 4B depicts fluid reservoirs (422-1 , 422-2, 422-3, 422-4, 422-5, 422-6). The reservoirs (422) may be of a variety of types including ports which are open and allow introduction of fluid into the fluid analysis device. The reservoirs (422) may be of various sizes and may contain different fluids.

[0066] Another example of a fluid structure is a rupture device (424).

That is, a blister pack with a membrane may be placed over the fluid analysis device. Upon depression by a user, the rupture device (424) fluid structure may rupture the membrane letting the contents therein pass into corresponding containers. Accordingly, as can be seen in Fig. 4B, using sacrificial structures, a variety of microfluidic structures may be formed, including input output ports, fluid channels, multi-layer fluidic routing, chambers, reagent storage, waste, and DMF components. Fig. 4B also depicts interconnect structures that were retained via a photomask (206) to form electrical interconnects (314).

[0067] Figs. 5A and 5B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. Specifically, Figs. 5A and 5B depict other examples of fluid structures that are formed using the methods described herein. For example, Fig. 5B depicts shallow and deep reservoirs (422-7, 422-8, 422-9, 422-10, 422- 11 , 422-12, 422-13, 422-14). As described above, such reservoirs (422) may hold any type of fluid including sample fluid, reagents, and waste. Fig. 5B also depicts a through hole (420-3) fluid structure.

[0068] As depicted in Figs. 5A and 5B, in some examples, fluid structures may be formed on both faces. For example, as depicted in Fig. 5B, the fluid analysis device includes reservoirs (422) on both faces.

[0069] Fig. 5B also depicts another example fluid structure. Specifically, Fig. 5B depicts an embedded channel (526-1 , 526-2). To form such embedded channels (526), a layer of copper-embedded compound (210) is placed to form a floor, another is formed where the copper is etched away to form the embedded channel (526), and a lid placed thereon by another layer of copper- embedded compound (210).

[0070] Figs. 6A and 6B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. As depicted in Figs. 6A and 6B, the cross-sections of the fluid structures may be varied. That is, fluid structures may not have straight sidewalls. By implementing a layered approach, fluid structures such as through holes (420-4, 420-5, 420-6, 420-7), may have non-straight sidewalls as depicted in Fig. 6B. Accordingly, a manufacturer has an increased degree of freedom to control the channel depth and width along the fluid structure.

[0071] Figs. 7A and 7B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. Figs. 7A and 7B depict various examples of fluid structures such as channels (212-1 , 212-2, 212-3), through holes (420-8, 420-9) that are non-straight and reservoirs (422-15). Figs. 7A and 7B also depict fluid structures formed on both surfaces of the fluid analysis device.

[0072] Figs. 8A and 8B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. As described above, one example of a fluid structure is a rupture device (424-2, 424-3). As described above, blister packs (828-1 , 828-2) may be attached to a fluid analysis device, which blister packs (828) may include a reagent. Upon depression by a user, the membrane of the blister pack (828) ruptures against the respective rupture device (424) and fluid contained therein is released, to be held for analysis or to be directed along a fluid channel to another portion, and in some examples, another layer of a fluid analysis device.

[0073] Figs. 9A and 9B depict the formation of fluid structures via removing sacrificial structures, according to an example of the principles described herein. Specifically, Figs. 9A and 9B depict other examples of fluid structures that may be formed. In particular, the fluid structures may be post filters (930) that include a series of posts disposed in a chamber. As fluid flows past the posts, certain particles or components within the fluid may be trapped. That is, a post filters fluid based on particle size. Accordingly, using the method described herein, the plastic compound may be deposited in relatively thin widths such that post filters (930) may be formed. In some examples, the thickness of the plastic compound, and the thickness of the sacrificial structures that are etched away may be on the order of 15 micrometers such that fine features such as the posts in a post filter may be formed. In some aspects the posts may have an aspect ratio of 10:1. That is they may be 10 times higher than they are wide. Such dimensions may not be possible using injection molded technologies.

[0074] In another example, the sacrificial structures may form inertial filters (932). In an inertial filter (932), fluid flows along an elongate path, which may be a spiral. Particles in the flow are subject to the force of inertia which make them follow the direction of the original motion. An inertial filter (932) is curved and different particles are subject to different inertial forces. Accordingly, particles with different properties separate themselves from each other.

[0075] Fig. 10 is a flow chart of a method (1000) of forming fluid structures via removing sacrificial structures, according to an example of the principles described herein. According to the method (1000), multiple layers of compound (Fig. 2D, 210) are stacked (block 1001), which compound (Fig. 2D,

210)is embedded with 1) structures that are to form fluid structures, i.e. , sacrificial structures and/or 2) structures that are to form electrical interconnects, interconnect structures. That is, as described above, layers (Fig. 2G, 218) are formed of structures (Fig. 2B, 208) embedded in a compound (Fig. 2D, 210). In some examples an individual layer (Fig. 2G, 218) may be formed of sub-layers (Fig. 2E, 204). As will be demonstrated, at least one electrical interconnect spans at least two layers (Fig. 2G, 218).

[0076] The method (1000) may include embedding (block 1002) a sensor die between adjacent layers (Fig. 2G, 218) of compound (Fig. 2D, 210). In this example, embedded electrical interconnects (Fig. 3B, 314) may span multiple layers (Fig. 2G, 218) to establish an electrical signal between the embedded sensor die and the surface of the fluid analysis device.

[0077] With multiple layers (Fig. 2G, 218) stacked (block 301) and a sensor die embedded (block 1002) between adjacent layers (Fig. 2G, 218), a mask (Fig. 2G, 206) is placed (block 1003) over interconnect structures while the sacrificial structures are etched (block 1004) to form a multi-layer fluid routing path.

[0078] Fig. 11 is a block diagram of a multi-layered fluid analysis device (1134), according to an example of the principles described herein. In some examples, the multi-layered fluid analysis device (1134) is a microfluidic structure. In other words, the components, i.e. , the fluid structures (1136) and the sensor die (1138) may be microfluidic structures. A microfluidic structure is a structure of sufficiently small size (e.g., of nanometer sized scale, micrometer sized scale, millimeter sized scale, etc.) to facilitate conveyance of small volumes of fluid (e.g., picoliter scale, nanoliter scale, microliter scale, milliliter scale, etc.).

[0079] The multi-layered fluid analysis device (1134) may include many layers (218) of compound (Fig. 2D, 210). In some examples, the compound (Fig. 2D, 210) is a molded interconnect substrate. The multi-layered fluid analysis device (1134) also includes a number of fluid structures (1136) which are sacrificially-formed in the multiple layers (218). That is, as described above, the layers (218) may initially include copper regions that when stacked form copper structures that may be etched away. The etching away of the copper structures results in fluid structures (1136). At least one fluid structure (1136) spans across two layers (218) of plastic compound (Fig. 2D, 210). The multi layered fluid analysis device (1134) also includes a sensor die (1138) embedded between adjacent layers (218).

[0080] Fig. 12 depicts a multi-layered fluid analysis device (1134), according to an example of the principles described herein. Fig. 12 clearly depicts the different layers (218-1 , 218-2) that are stacked and depicts the fluid structures (Fig. 11 , 1136), which in this case include fluid channels (212) that span across multiple layers (218-1 , 218-2). As described above, the different layers (218) form a monolithic structure wherein no adhesive is used to adjoin layers.

[0081] Fig. 12 also clearly depicts the sensor die (1138) which in this case is mounted below the fluid analysis device (1134). In this example, at least one fluid structure is a fluid channel (212) which exposes the sensor die (1138) to a fluid introduced into the fluid analysis device (1134). That is, in this example, user depression of a blister pack (828-1 , 828-2) may direct fluid into the channel fluidly connected to the sensor die (1138). Fluid may be directed to the sensor die (1138) in other fashions as well. For example, fluid may be introduced via a port. As fluid passes through the fluid channel (212) it passes by the sensor die (1138) such that the sensor die (1138) may perform an operation on, or sense a characteristic of the fluid. As described above, in one example the electrical interconnect (314) is an embedded electrical trace that spans multiple layers (218-1 , 218-2).

[0082] In some examples, the multi-layered fluid analysis device (1134) also includes a transparent lid (1240) adhered to a top layer (218-2). The transparent lid (1240) allows a scientist to view the operations occurring within the fluid analysis device (1134). The lid (1240) of the fluid analysis device (1134) may be formed of a variety of materials. Depending on the application, in some examples the lid (1240) may be an optically transparent lid (1240). In this example, optical signals and/or light may pass through the optically transparent lid (1240) to illuminate the fluid passing therethrough, or to aid in any of the fluid analytic/manipulation operations that are executed. Examples of optically transparent materials include glass and polycarbonate.

[0083] As described above, the fluid analysis device (1134) of the present specification, allows multi-layer routing capability so the fluid analysis device (1134) can support multi-layer complex electrical routing, offering high precision electrodes to perform various microfluidic functions such as DMF operations, electrophoresis, capacitive sensing, and may be integrated with sensor die (1138).

[0084] Fig. 13 depicts a multi-layered fluid analysis device (1134), according to an example of the principles described herein. Fig. 13 depicts multiple sensor die (1138-1 , 1138-2, 1138-3) mounted at different positions within the multi-layered fluid analysis device (1134). As described above and as depicted in Fig. 12, in some examples, a sensor die (1138-3) may be formed on a bottom surface. For example, the sensor die (1138-3) may be flip chip mounted. In this example as depicted in others, the electrical interconnect (314) may be an embedded electrical trace that couples the sensor die (1138-3) to an external component.

[0085] Also as described above, the fluid analysis device (1120) may include a sensor die (1138-2) that is embedded between adjacent layers (218-1 , 218-2). In this example, a user may etch copper to form a sensor die recess and place the sensor die (1138-2) therein. A second layer (218-2) may then be placed on top to embed the sensor die (1138-2) inside the body of the fluid analysis device (1134). Doing so provides great flexibility in fluid analysis device (1134) configuration. That is, the sensor die (1138-2) need not be placed solely on an exposed surface, but could be placed anywhere on, or in, a fluid analysis device (1134). In some cases, doing so may result in a fluid analysis device (1134) with a smaller footprint as components may be stacked in different layers (218) of the fluid analysis device (1134). Fig. 13 also depicts an example where the fluid structure is a sensor die recess on a top layer (218- 2) into which the sensor die (1138-1 ) is placed.

[0086] Fig. 14 depicts a multi-layered fluid analysis device (1134), according to an example of the principles described herein. Specifically, Fig. 14 depicts a fluid analysis device (1134) used for digital microfluidics (DMF) analysis. DMF refers to an operation where microdroplets of a fluid are moved, ejected, stored, etc. by a platform of insulated electrodes (1442). Such operations may be used in such analytic processes such as mass spectrometry, colorimetry, electrochemical operations, and electrochemiluminescence.

[0087] In this example, the electrical interconnects (Fig. 3B, 314) described earlier may form the DMF electrodes (1442) used to move the microdroplets of fluid. As with the other examples, such DMF electrodes (1442) may be formed at the same time as sacrificial structures which are etched to form fluid structures. That is, as demonstrated above, multiple structures (Fig. 2B, 208) may be formed. Some of those structures are interconnect structures pertaining to the DMF electrodes (1442) while other structures (Fig. 2B, 208) are sacrificial structures pertaining to the fluid structures (Fig. 1 , 1136), whatever those fluid structures may be. During formation, the sacrificial structures pertaining to the fluid structures (Fig. 11 , 1136) are etched away while the interconnect structures that pertain to the DMF electrodes (1442) are retained such that DMF operations can be carried out on any introduced fluid. Fig. 14 also depicts an electrical input/output (1444) used in the DMF operation, which electrical input/output (1444) may similarly be formed as described above.

[0088] Fig. 15 depicts a PCR chamber fluid structure (1136). That is, as described above, fluid structures (1136) may be of any type. In one specific example, the fluid structure (1136) is used to carry out a PCR reaction. PCR refers to the generation of millions to billions of copies of a specific DNA sample. As such, a scientist may take a small sample of DNA and amplify it to a large number of copies, such that it may be studied in detail. During PCR, a DNA sample is heated to around 100 degrees Celsius (C) and then cooled to around 50 degrees C. Accordingly, in this example, the heating element (1546) of the PCR chamber may be formed via the interconnect structures. That is, copper embedded in a plastic compound may be retained and used to heat DNA samples that pass thereby, thus heating them to carry out PCR.

[0089] As described above, a fluid analysis device (Fig. 1 , 1134) may include any number of fluid structures (1136). Accordingly, any of the aforementioned fluid structures (1136) may be formed on a single device such that multiple fluid operations can be carried on a single lab-on-a-chip device. [0090] For simplicity in Fig. 15-19, the lid has been removed to view the fluid structure (1136). However, in each of these examples, a lid may be placed over the fluid structure (1136), whether that lid be a glass lid or a component of an overlying layer. That is, the PCR chamber and other fluid structure (1136) may be entirely embedded and enclosed within the fluid analysis device (Fig. 1 , 1134).

[0091] Fig. 16 depicts an electrophoresis fluid structure (1136), according to an example of the principles described herein. Electrophoresis refers to a process wherein an electric field is used to move and/or separate charged particles in a sample. In this example, electrodes (1648) formed in the layer may be used to separate these charged particles in a fluid. These electrodes (1648) may originate as interconnect structures which are maintained while sacrificial structures are etched away.

[0092] Fig. 17 depicts a droplet forming chamber fluid structure (1136), according to an example of the principles described herein. More specifically, as described above, the fluid structures (1136) may include embedded channels (Fig. 5B, 526) and in some examples these embedded channels (Fig. 5B, 526) may cross one another. The intersection of crossing channels (Fig. 5B, 526) may form a droplet-forming chamber (1750).

[0093] That is, a small amount of a sample fluid may be introduced into a droplet-forming chamber (1750) while an immiscible buffer fluid such as oil is introduced from the crossing channels into the droplet-forming chamber. As the sample fluid does not intermix with the immiscible buffer fluid, the sample forms into droplets which are suspended in the immiscible buffer fluid. Doing so may aid in subsequent analysis as it may be desirable to study the fluid as droplets.

[0094] Fig. 18 depicts a lysis chamber fluid structure (1136), according to an example of the principles described herein. Similar to the example depicted in Fig. 17, embedded channels (Fig. 5B, 526) may cross. In this example, the junction of the channels (Fig. 5B, 526) may form a lysis chamber (1852) where lysis occurs. Lysis refers to the rupturing of a cell membrane to expel the contents thereof. Accordingly, in this example, cells may be introduced into a lysis chamber (1852) while a lysing agent is introduced from the crossing channels into the lysis chamber (1852). The lysing agent may cause a reaction which causes the cells to rupture or burst. Doing so allows for the analysis of the cell contents.

[0095] Fig. 19 depicts a dry reagent storage chamber fluid structure (1136), according to an example of the principles described herein. That is, the fluid structure (1136) may include a chamber (1954) where a dry reagent may be stored. In this example, fluid may be introduced into the storage chamber (1954) which may interact with the dry reagent.

[0096] Accordingly, as demonstrated by these examples, a variety of fluid structures (1136) may be generated using sacrificial structures formed in a layer-wise fashion. Moreover, these fluid structures may be formed at the same time as interconnects using the same material, i.e., copper. Accordingly, the present specification describes methods and devices that greatly enhance the operations and capabilities of fluid analysis devices.

[0097] The systems and methods of the present specification 1) provide high precision and fine pitch fluidic routing capability; 2) support multi-layer fluidic routing layers; 3) are compatible with IC packaging technologies; 4) provide a system-in-package platform for life sciences application; 5) allow for creation of complex electrical routings; 6) are low cost and have a fast turnaround; and 7) support a variety of microfluidic functions.