WO2003024597A1

WO2003024597A1 - Microscale fluid handling system

Info

Publication number: WO2003024597A1
Application number: PCT/SE2002/001698
Authority: WO
Inventors: Patrik Hollman; Ove ÖHMAN
Original assignee: Åmic AB
Priority date: 2001-09-18
Filing date: 2002-09-18
Publication date: 2003-03-27
Also published as: SE0103110D0

Abstract

Multilayer microscale fluid handling device that comprises at least one polymer substrate (30) with a microscale fluidic structure formed in a first surface of the substrate, and a microscale through-hole that extends from the microscale fluidic structure to an opposite surface of the substrate. There is also provided a method for manufacturing such.

Description

Microscale fluid handling system

Field of the Invention

The present invention relates to microscale fluid handling devices and methods for manufacturing such. More specifically, the invention relates to a multilayer polymer microscale fluid handling device and a method of manufacturing the same.

Prior Art

Currently, extensive efforts are being made to reduce the volumes of reagents and samples used in assays. New devices which are capable of performing assays on volumes of the order of nanolitres and picolitres are under development. Devices for performing such assays are commonly known as microscale fluid handling devices.

Such systems are mainly produced by different replication techniques. A master is formed on the surface of silicon wafer, mainly by different lithography and etching steps. The master is then either used as a direct mold in the replication process, or it is used to create positive or negative master copies. The step of replication may comprise techniques such as injection molding of a thermoplastic material, hot- embossing of a thermoplastic material, casting a thermoset polymer or elastomeric material.

Conventional polymer based microscale fluid handling systems however are limited to in-plane structures and are limited in complexity. Due to the in-plane restriction, a number of features or elements cannot be incorporated in existing replicated microscale fluid handling devices.

A multilayer fluid handling system is described in US 5,961,932, in which a micro- ceramic chemical plant is disclosed. However, the technique of forming a multilayer structure in the green ceramic-state, followed by sintering at high temperatures, is a much more complicated manufacturing process, compared to replication of polymers. Therefore, this process is a low-volume process and the resulting ceramic fluid handling devices are expensive to produce and cannot be of single use type, whereby the risk for contamination is increased.

Up to now it has not been possible to manufacture polymer microscale fluid handling structures with well defined microscale communication holes between the microscale fluid handling structures on one surface and the opposite surface thereof. Furthermore, it is of great importance that such communication holes approximately have the same cross-sectional area as the microscale fluid handling structures that they are connected to. To achieve a uniform flow it is of great importance that all sections of the microscale fluidic system, except for reaction chambers and the like, have an essentially uniform cross sectional area.

WO 01/26812 Al disclose a microscale fluidic device having a cover laminated thereon and access holes that extend through the cover. These access-holes are solely intended for injection or withdrawal of fluid from the device and therefore they do not need to be microscale sized. Therefore the access-holes are punched or drilled out from the cover. The method of punching holes has a number of disadvantages that limits the use of such holes to create well defined holes needed in a ulti layer microscale fluid handling device. Firstly, it is extremely difficult to punch holes with a size in the microscale region. Secondly, it is difficult to align the punched holes with the other microscale features in the device.

One method for producing replicated polymer substrates with through holes of suitable size and shape is shown in applicants own application PCT/ SEO 1/02250 which is directed towards making nozzles for ink-jet printing heads and the like.

Summary of the invention

The object of the invention is to provide a multilayer microscale fluid handling system and a method for producing the same, which overcomes the drawbacks of the prior art multilayer microscale fluid handling systems and devices. This is achieved by the multilayer microscale fluid handling system as defined in claim 1, and the method as defined in claim 13.

One advantage with such a multilayer microscale fluid handling system is that it, due to low production costs, can be designed as a single use system, whereby contamination risks connected with reuse of fluid handling systems are avoided.

Another advantage is that the system in a simple manner may comprise transparent substrates that permit in situ optical analysis of fluids in the system.

Another advantage is that the system may be of more complex nature compared to prior single layer microscale fluid handling systems.

Another advantage is that semi permeable membranes, filters and the like may be incorporated in the multilayer microscale fluid handling system in a simple manner.

Still another advantage is that microscale fluid handling systems comprising crossing microscale channels may be realized.

Yet another advantage is that valves and pumps may be integrated in the microscale fluid handling system in a simple manner.

Embodiments of the invention are defined in the dependent claims.

Brief description of the figures

Fig. 1 is a cross-sectional view of a microscale fluid handling system according to the present invention comprising a lateral filter.

Fig. 2 shows a flow chart over the microscale fluid handling system in fig 1.

Fig 3 shows a flow chart over the microscale fluid handling system in fig 3. Fig. 4 is a cross-sectional view of a microscale fluid handling system according to the invention comprising a crossing microscale channel.

Fig. 5 shows an example of a sample distribution on the surface of a substrate produced a 10 by 10 micro-array according to one embodiment of the present invention.

Figs. 6a and 6b show an example of a microscale valve in an open and closed state, respectively.

Fig. 7 shows an example of a microscale pump.

Fig. 8 shows an example of a silicon master for producing a layer in the multilayer microscale fluid handling system according to the present invention.

Fig. 9 shows a negative master copy of the silicon master of Fig 8.

Fig. 10 shows a resin layer applied on the negative master copy of fig 9.

Fig. 11 shows a lithography step in the method according to the present invention.

Fig. 12 shows the resulting polymer substrate from the method presented with reference to figs. 8 through 11.

Detailed description of the invention

Embodiments of the invention will now be described with reference to the figures.

A "through hole" is to be understood as a channel like structure through an essentially flat member. The "through hole" has a first opening and a second opening on opposite sides of said member. The geometries of said openings can be of optional shapes, and may be mutually different. The present invention relates to microscale fluid handling systems with two or more fluid handling layers. By building up such systems from more than one layer a number of features can be provided that cannot be provided in a single layer. Furthermore, multi-layer systems offer the possibility to provide laterally extending structures or components in the fluidic system.

Throughout this application the expression microscale fluidic structure refers to all types of microscale structures capable of handling fluid in a microscale device, and which may be produced on/ in the surface of a polymeric substrate. Examples of microscale fluidic structure are microscale channels, ducts, different types of reaction or mixing chambers and the like. Further, the term fluid is intended to refer to fluids in all flowing states, i.e. gas, or liquid state.

The structure of the microscale fluid handling system according to the invention may be compared to multi layer circuit boards, wherein the conductors are substituted for microscale channels and inter-board connectors or vias by inter- laminar through holes. When the next layer is laminated on top of a layer with a microscale cannel, the channel is closed. The individual "circuit board" type layers are piled on top of each other to create the desired fluid handling system. To achieve a working system, the inter-laminar holes have to be aligned with the receiving structure in the next layer (microscale channel, another inter-laminar hole or the like). The diameter of the holes is about 50-100 μm and the dimensions of the microscale channels are in the same order. The alignment of different layers is may be done by optical techniques, of the type commonly used in the field of microelectronics. Alternatively, the alignment is performed by precision mechanical constructions of the type described in the Swedish patent application 0202092-3, whereby extremely fast and accurate alignment is achieved.

The individual polymer layers in the device according to the invention may be formed by replication in several ways, such as by, injection molding of a thermoplastic material, hot-embossing of a thermoplastic material, casting a thermoset polymer or elastomeric material. Preferably, the inter-laminar through holes are created directly in the replication process. Alternatively the inter-laminar through holes in the polymer layers may be formed in replicated polymer substrates, by micro machining techniques such as drilling, milling, laser or water ablation and the like. The individual layers are then glued together after being aligned.

The microscale fluid handling device according to present invention may comprise microscale structures such as: fluid valves, filter structures, mixing or dilution chambers. The device may further comprise one or more layers comprising a flow- cell which can, when pressed against an external substrate, allow fluid to flow over the external substrate.

The microscale fluid handling device according to the present invention may further comprise a number of independent fluid handling systems in the same device, such as numerous parallel systems for performing parallel experiments, or two or more flow-cells forming an array of flow-cells.

The microscale fluid handling device comprising a flow-cell or an array of flow-cells may also be used to direct fluids to sites on the surface of a substrate to produce a surface active substrate which in turn is used as an analytical device.

The principals of the present invention lies in a multilayer microscale fluid handling device that comprises at least one polymer substrate with a microscale fluidic structure formed in a first surface of the substrate, and a microscale trough-hole that extends from the microscale fluidic structure to an opposite surface of the substrate. By incorporation of such layers into a multilayer microscale fluid handling device, all types of devices described above may be produced

The overall method according to the invention comprises two main steps:

providing at least one polymer substrate with a microscale fluidic structure formed in a first surface of the substrate, and a microscale through-hole that extends from the microscale fluidic structure to an opposite surface of the substrate, and

aligning and laminating said polymer substrate with other substrates to form the multilayer microscale fluid handling system. Now the method according to the invention will be described in detail with reference to a schematic embodiment of the present invention.

One possible method for providing said at least one polymer substrate according to an embodiment of the present invention is now described in detail by way of an example, which is not to be regarded as limiting on the scope of the invention as defined in the claims, and with reference to Figs. 8 to 12.

Firstly a master 700 (Fig. 8) in the form of a silicon wafer 710 is produced. Microscale channels 720 and other microscale surface structures 730 are formed in the surface 740 of the silicon wafer by methods known in the art, e.g. lithography followed by etching and the like. Normally the master comprises a large number of sections, each representing a layer in an independent microscale fluid handling system.

Thereafter, a negative master copy 750 (Fig. 9) of the structured silicon master 700 is created by electroplating in e.g. nickel, i.e. a copy with opposite polarity (containing convex structures) is created. The process of making master copies by electroplating in nickel is well known in the art of micro replication and will therefore not be described in detail herein. The negative master copy 750 is thereafter used as mold surface for the molding of polymer substrates for the inventive microscale fluid handling system.

The method of molding polymer substrates comprises the following steps:

Applying an UV curing epoxy resin 760 (Fig. 10) (e.g. SU8 obtainable form Micro Chem. Corp.) of a desired thickness onto the mold surface of the nickel master copy 750 by spin-coating. Other types of epoxy resins that are curable by electromagnetic radiation may also be used.

In order to create the through holes connecting the microscale channels with the opposite side of the substrate, a mask 770 is placed above the epoxy resin 760 (Fig. 11). The mask need not be in physical contact with the resin layer 760. The mask 770 is preferably a glass plate on which a pattern of non-transparent areas 780 has been provided by a suitable technique. Mask making is an art well known to the skilled man and need not be further discussed herein. These areas 780 can take any desired shape to create holes of a suitable shape. The mask 770 is placed such that the non-transparent spots 780 are aligned with microscale structures (see Fig. 11). Then, the disk is exposed to UV light in order to polymerize the non-shaded portions of the resin layer 760. After an appropriate time of exposure (e.g. 150 seconds), and heating to 95oC, the resin is cured in the regions outside the shading areas 780. The non-cured parts 790 of the resin layer 760 are dissolved in propylene glycol ether acetate, which opens up through holes 800, as shown in Fig. 12. Finally the molded resin layer is removed mechanically from the mold, and the polymer substrate 810 is finished, as shown in Fig 12.

Thereafter the polymer substrate 810 is laminated with at least one additional layer to form a multilayer microscale fluid handling device according to the present invention. The additional layers may be produced using the above molding method or any other applicable technique.

Whereas other microscale fluid handling devices based on silicon wafers, ceramics and the like have to be used repeatedly due to the high production costs, the microscale fluid handling device manufactured by the method according to the present invention is a low-cost polymeric disposable device that allows single-use, which eliminates the risk for contamination. Furthermore, the use of transparent polymeric materials permits that the device is formed such that optical analysis of samples in the device may be performed.

Further features and possibilities of the present invention will be evident from the following embodiments.

Figure 1 shows a schematic embodiment according to the present invention comprising five individual layers 10 - 50 laminated on top of each other. The first layer is referred to as top cover plate 10, the second as fluid delivery layer 20 the third as filter layer 30, the fourth as fluid receiving layer 40 and the fifth as bottom cover plate 50. The top cover plate 10 is preferably a transparent polymer plate with at least one fluid inlet hole or well 60 into which the fluid to be filtered and analyzed is entered. The inlet hole 60 in this plate may be of a relatively large diameter, compared to the underlying microscale structures. The top cover plate 10 may be manufactured by microscale replication techniques such as molding and injection molding or simply by punching out inlet holes 60 from a polymer plate.

The top cover plate 10 further encloses a microscale channel 70 formed in the fluid delivery layer 20 for communication between the inlet hole 60 and an upper filter opening 80. The fluid delivery layer 20 is formed by through-hole type microscale replication molding as is discussed in detail above, whereby extremely well defined microscale structures may be achieved.

The filter layer 30 provides a filter element 90 in the lateral region directly below upper filter opening 80. Fluid is directed to the filter element 90 by the opening 80, and collected from the filter element by a collecting microscale channel 100 in the fluid receiving layer 40. In an alternative embodiment the entire filter layer 30 is provided as a homogeneous unidirectional filter element 90, whereby fluid that is directed to the filter element by the opening 80 flows vertically though the filter element 90 without horizontal dispersion.

The fluid receiving layer 40 collects the filtered fluid from the filter element 90 and the collecting microscale channel 100 directs the fluid to a through hole 110 and eventually to an analyze-chamber 120 in the bottom cover plate 50. The bottom cover plate 50 is preferably a transparent polymeric plate that allow optical characterization of the filtered fluid.

According to another embodiment of the present invention, it is possible to produce more complex microscale fluid handling devices wherein two or more microscale channels cross. To allow crossing of two microscale channels it is necessary to provide channels in more than one plane.

Figure 3 shows a flowchart over a mixing-arrangement 200 comprising a number of mixing cells 205 each cell comprising one mixing chamber 210. Each mixing chamber 210 is connected with one individual inlet 220, one individual outlet 230, and one common reagent inlet 240. Each individual inlet 220 is connected to an inlet microscale channel 250, connecting them to an individual sample inlet 260, arranged a distance away from the reaction chamber and is used for injecting a sample into the mixing cell 205. When the mixing is completed, the individual outlet 230 of each cell 205 drains the mixing chamber 210. The individual outlet 230 is connected to an outlet microscale channel 270 which ends at an individual sample outlet or at a sample analysis site 280.

The common reagent inlet 240 is connected to a reagent microscale channel 290. All reagent microscale channels 290 in the mixing arrangement 200 are in turn connected to a common feed microscale channel 300 for feeding the same reagent to all mixing chambers 210. At one end, the common feed microscale channel 300 is connected to a reagent inlet or well 310. As is shown in the figure, the common feed microscale channel 300 must cross the inlet microscale channels 250 (or the outlet microscale channels 270) to reach the individual mixing chambers 210.

Figure 4 shows a schematic example of the above mixing arrangement 200 that is possible according to another embodiment of the present invention. In Fig. 4 a first layer 320 has a top surface 325 which comprises a number of mixing chambers 210, each having their individual inlet channels 250, individual outlet channels 270 and reagent microscale channels 290. To allow connection to the common feed microscale channel 300, the reagent microscale channels 290 are provided with, a through-hole 330 that extends through the first layer 320 to the bottom surface 335. The common feed microscale channel 300 is provided in a second layer 340 that is laminated to the bottom surface 335 of the first layer 320. The common feed microscale channel 300 is aligned with the through holes 330, such that the common feed microscale channel 300 is in fluidic communication with all of the reagent microscale channels 290. Furthermore the first layer 320 is provided with a reagent supply through-hole 350, which is aligned with or otherwise arranged to be in fluidic communication with (side channel 355) the common feed microscale channel 300, and is used for feeding reagent to the common feed microscale channel 300. In a third embodiment, the microscale fluid handling device comprises a number of individual flow-cells in an array that are individually addressed. The microscale fluid handling device comprising a flow-cell or a micro-array of flow-cells is used to direct fluids to sites on the surface of a substrate for the purpose of in-situ analysis in real-time or ex-situ analysis. That is, the flow-cell is removed and the substrate analyzed using some form of external analytical method. Figure 5 shows an example of the resulting sample distribution on the surface of a substrate from a 10 by 10 micro-array.

However, if one strives to make a micro array sufficiently large in terms of the number of independent flow-cells, at the same time as the size of the micro-array is kept at (or near) a minimum, all individual microscale channels that has to be connected to the output holes cannot be accommodated in a single plane. Hence, a multi layer approach is necessary when designing large micro- array systems with individually or substantially individually addressable flow-cells.

The polymeric microscale fluid handling device according to the invention may be formed such that micro-array systems of virtually any size and complexity can be produced at low cost, and with all benefits from the polymeric material.

In another embodiment of the present invention, active components such as valves and pumps are included in the fluid handling system. As is shown in figs. 6a, 6b and 7 the active components are based on the multi-layer design of the system.

Figs. 6a and 6b show a valve 500 that is used to close a microscale channel 510. The valve 500 is basically comprised of a through-hole 520, at the upper end connected to a control channel (not shown) for controlling the valve, and at the end facing the microscale channel 510 closed by a flexible membrane 540. The control channel 530 is at the other end connected to a pneumatic or fluidic control device (not shown) that controls the pressure in the control channel. When a high pressure is applied on the flexible membrane 540 through the control channel, the flexible membrane 540 expands (see fig. 6b) into the micro channel 510, and if the pressure is high enough the membrane 540 will close the entire channel 510. Fig. 7 shows one embodiment of a fluid pump 600 that may be incorporated in the microscale fluid system of the present invention. The pump 600 is comprised of three independently controllable valves 610a-c. To achieve a pumping action, the three valves 610a-c are repeatedly actuated in a successive manner.

Claims

1. Multilayer microscale fluid handling device characterized in that

it comprises at least one polymer substrate (30) with a microscale fluidic structure formed in a first surface of the substrate, and a microscale through- hole that extends from the microscale fluidic structure to an opposite surface of the substrate.

2. Multilayer microscale fluid handling device according to claim 1 characterized in that

said polymer substrate (30) is injection molded in a thermoplastic material.

3. Multilayer microscale fluid handling device according to claim 1 or 2 characterized in that

said polymer substrate (30) is hot-embossed in a thermoplastic material

4. Multilayer microscale fluid handling device according to any of the claims 1 to 3 characterized in that

said polymer substrate (30) is formed as a thermoset polymer by casting.

5. Multilayer microscale fluid handling device according to any of the claims 1 to 4 characterized in that

said polymer substrate (30) is formed in an elastomeric polymer material.

6. Multilayer microscale fluid handling device according to any of the claims 1 to 5 characterized in that

it comprises a fluid valve.

7. Multilayer microscale fluid handling device according to any of the claims 1 to 6 characterized in that

it comprises a fluid pump.

8. Multilayer microscale fluid handling device according to any of the claims 1 to 7 characterized in that

it comprises a filter structure.

9. Multilayer microscale fluid handling device according to any of the claims 1 to 8 characterized in that

it comprises a mixing or dilution chamber.

10. Multilayer microscale fluid handling device according to any of the claims 1 to 9 characterized in that

it comprises a flow-cell, which can, when pressed against an external substrate, allow fluid to flow over the external substrate.

11. Multilayer microscale fluid handling device according to any of the claims 1 to 10 characterized in that

it comprises an array of flow-cells.

12. Multilayer microscale fluid handling device according to claim 11 characterized in that

the individual flow-cells in an array can be individually addressed.

13. Method of manufacturing a multilayer microscale fluid handling system, characterized by the steps of:

providing at least one polymer substrate (30) with a microscale fluidic structure formed in a first surface of the substrate, and a microscale through- hole that extends from the microscale fluidic structure to an opposite surface of the substrate, and

aligning and laminating said polymer substrate (30) with other substrates to form the multilayer microscale fluid handling system.

14. Method of manufacturing a microscale fluid handling system according to claim 12, characterized in that the step of providing at least one polymer substrate comprises:

providing a mold surface defining a microscale fluidic structure

applying a light curable epoxy resin layer (760) onto the mold surface,

masking said curable resin with a mask having a pattern of non-transparent areas defining position and geometry of at least one microscale through-hole,

exposing the curable resin to curing conditions such that only portions exposed by said mask are cured;

dissolving non-cured resin; and

removing the cured resin layer from the mold surface.