JP2005336049A - High thermal efficiency glass microchannel and method for forming the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simplified and reliable manufacturing method in which heat exchange between alternately arranged microchannels is maximized. <P>SOLUTION: The method of forming a microfluidic device is provided with a step of supplying a mold 78, a step of positioning a soft glass sheet 70 of glass or a glass ceramic material on the whole surface of the mold, a step of applying the differential gas pressure on the soft glass sheet to conform the sheet to the mold to form the a microchannel 90 on at least one surface of the soft glass sheet and a step of substantially enclosing the microchannel 90 on at least one surface of the sheet by bonding a sheet 82 of glass or glass ceramic on the whole surface of the mold. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates generally to microfluidic devices and methods of manufacturing such devices, and more particularly to high thermal efficiency glass, glass-ceramic or ceramic microchannels or microfluidic devices, and methods of manufacturing such devices.

  A microchannel or microfluidic device is broadly understood as a device having a channel with a characteristic dimension roughly in the range of 10 μm to 1000 μm so that the fluid is directed and processed in various ways inside. ing. Such devices are considered highly promising because they enable innovative changes in chemical and biological processing techniques. This is because, in particular, the heat and mass transfer rates of microfluidic devices increase orders of magnitude beyond those achievable in conventional chemical processing systems.

  Microfluidic circuits in glass or glass-ceramic have the advantage of having excellent chemical resistance. However, while glass and glass-ceramics have relatively poor thermal conductivity, heat exchange is important in most chemical synthesis. Accurate and safe local thermal management generally allows chemical processing at relatively higher concentrations, pressures, and temperatures, resulting in better yields and higher efficiency in most cases It is.

  The present invention provides a device having a microfluidic channel formed from a thin glass, glass-ceramic or ceramic sheet material having good surface properties and sufficient strength, and further ensures that the device and channel are A method for efficient manufacturing is provided. Thin walled microchannels can enable efficient heat exchange while exhibiting excellent chemical durability and thermal resistance. The molding process of the present invention provides a simple and reliable manufacturing process while the resulting element maximizes heat exchange.

  According to one embodiment of the present invention, the microfluidic device includes a molded sheet made of a glass or ceramic material. The molded sheet has one or more first microchannels on its first side and one or more second microchannels on a second side opposite the first side. It is formed to have a channel. The second channel is complementary to the first channel. The first channel is substantially occluded by a first plate of glass or glass-ceramic material adhered to the first side of the molded sheet, and the second channel adheres to the second side. It can be substantially occluded by a second plate of glass or glass-ceramic material.

  According to another embodiment of the invention, a method for forming a microfluidic device is provided. This method provides a single surface mold, positions a sheet of glass or ceramizable glass on the mold, heats the mold and sheet, and adheres the sheet to the mold Including applying a gas pressure difference to. As a result, microchannels are formed on at least one side of the sheet, broadly both sides. The microchannel is then substantially occluded or surrounded by adhering glass or ceramizable glass over the entire surface of at least one side of the sheet containing the microchannel.

  In accordance with yet another embodiment of the present invention, a method for forming a microfluidic device is provided, the method including the step of deploying a first soft glass sheet over the moving mold. The first soft glass sheet has a first surface on the opposite side of the mold and a second surface on the mold opposite to the first surface. The method further includes vacuum forming to allow the soft glass sheet to adhere to the mold, resulting in the formation of an adhesive sheet having microchannels on both the first and second surfaces. The method further includes developing a second soft glass sheet on the first surface of the adhesive sheet, so that the second soft glass sheet is adhered to the adhesive sheet, and the first The microchannel is substantially occluded on the surface. The method further includes removing the adhesive sheet from the mold. The method further includes deploying a third soft glass sheet on the second surface of the adhesive sheet, so that the second soft glass sheet is adhered to the adhesive sheet, and the second The microchannel is substantially occluded on the surface.

  Both the foregoing summary and the following detailed description are exemplary of the invention and are intended to provide an overview or configuration in order to understand the nature and characteristics of the claimed invention. You should understand that. The accompanying drawings are incorporated into and constitute a part of this specification so as to provide a further understanding of the invention. The accompanying drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and processes of the invention.

  The present invention provides a device having a microfluidic channel formed from a thin glass, glass-ceramic or ceramic sheet material having good surface properties and sufficient strength, and further ensures that the device and channel are A method for efficient production is provided. The method of the present invention provides molding by gas pressure differential to achieve glass, glass-ceramic or ceramic microchannels with the desired thin wall properties and high surface quality. The resulting thin-walled microchannels enable efficient heat exchange while exhibiting excellent chemical durability and thermal resistance. The molding process of the present invention provides a simple and reliable manufacturing method while the resulting element maximizes heat exchange.

  According to the present invention, the microchannels are made by a method that involves plugging a three-dimensional glass, glass-ceramic or ceramic-like material, rather than simply by stacking microstructured flat plates. An exemplary method for constructing an aspect of the present invention is described below in connection with FIGS.

  FIG. 1 shows a cross-sectional view of an apparatus 10 useful in connection with one aspect of the present invention. The apparatus 10 may be pre-machined or, alternatively, a suitable material such as a heat resistant steel plate “NS 30 / ASI 310” available from Thyssen-France, 78 Maurepas, France. A fluid circuit mold 20 is formed. The mold 20 includes micro passages 22 for vacuum distribution. The mold 20 is placed in a vacuum sealing structure such as a vacuum box 24 having a surface or a ledge 26 for vacuum sealing surrounding it. The internal volume of the vacuum box 24 is connected to a vacuum source such as a vacuum pump, not shown in the figure.

  Prior to use, mold 20 is coated with a suitable release agent such as calcium hydroxide (eg, alcohol + 0.5% “Disperbick 190” test solution). Disperbick 190 is readily available from BYK-Chemie (BYK-Chemie Gmbh, Abelstr. 14D-46483 Wesel, Germany). The release agent is desirably sprayed uniformly on the entire surface of the mold 20.

  As shown in FIG. 2, a thin plate 30 made of a suitable glass material and having a surface area large enough to cover the surface or ledge 26 is then attached to the mold 20. The glass can be, for example, “Corning 1737” available from Corning Incorporated, Corning NY, USA.

  The thin plate 30 and the mold 20 are then heated together to a temperature above the annealing point of the glass material, but preferably near the softening point of the glass material. In the case of “Corning 1737”, which has an annealing point of about 721 ° C. and a softening point of about 925 ° C., the mold and sheet can be heated to about 870 ° C. for about 20 minutes or more.

  Thereafter, a vacuum is applied to the vacuum box 24 for a sufficient time such that the thin plate 30 is in close contact with the side surface of the mold 20. As a result, a molded sheet as depicted in FIG. 3 is obtained. As an alternative, gas pressure can be applied to the face of the sheet 30 on the opposite side of the mold 20, and the microchannel 22 is used only to relieve the pressure. As a further alternative, the positive pressure from the outside of the mold and the vacuum in the mold can be applied simultaneously.

In addition to reshaping the thin plate 30 into the molded sheet 32, vacuum forming also has the effect of re-sucking the thin plate 30 (vacuum re-suction). As a result, the molded sheet 32 is generally thinner than the original thin plate 30, and the area where the material is sucked into the mold is particularly thin. This vacuum forming method therefore reliably and reproducibly forms a wall structure with a thickness of 0.3 mm or less, preferably with a thickness in the range of about 0.2 mm to about 0.7 mm or less. It makes it possible to do well.
On the other hand, using an appropriate thickness of starting material, thicker wall structures can also be formed by using this method. This includes thicknesses in the range of about 0.7 mm to about 3 mm that are useful for use in high pressure or ultra high pressure applications.

  After vacuum forming, the mold 20 and the molded sheet 32 are cooled to a sufficiently low temperature that the molded sheet 32 can hold its molded shape, but high enough so that it can be easily removed from the mold 20. It is desirable to be temperature. For example, in “Corning 1737”, the sheet 30 can be cooled to about 750 ° C. over 2 minutes. Thereafter, light air pressure is applied to the vacuum channel 22 in order to remove the molding sheet 32 from the mold 20. A mold release agent greatly facilitates this step. The resulting molded sheet 32 is shown in cross section in FIG.

  Next, as shown in the cross section of FIG. 5, the upper and lower flat plates 34 and 36 are arranged to face the molded sheet 32 to form an assembly 38. Prior to bonding the assembly 38 together, the desired input and output holes may penetrate the upper plate 34 and / or the lower plate 36 by drilling, grinding or other suitable method (if necessary, the molded sheet 32). Is also formed). As shown in FIG. 5, the access holes may be formed in the opposite plate as in the case of holes 42 and 44 (on the right side of the figure), or the holes 46 and 48 as required. It is formed on the same flat plate as in the case. The access hole may extend through both the upper plate 34 and the molded sheet 32 as in the case of the hole 48.

  Thereafter, as shown in FIG. 6, the assembly 38 forms a microfluidic device 50 having closed or enclosed microchannels or passages 40 with example access holes 42, 44, 46, 48. To be glued. Bonding of the assembly 38 is preferably accomplished by holding the assembly 38 at about 870 ° C. for about 90 minutes by glass-to-glass thermal bonding of a “Corning 1737” glass slab and a “Corning 1737” shaped sheet. By drilling or otherwise forming the access hole before bonding, it can be annealed if there are any micro cracks or surface damage resulting from the hole forming process.

  The above inventive method example can form a pair of circuits separated by a thin glass layer in the same method step. For example, starting with a 0.5 mm thick sheet, the sidewall 58 thickness can range from 0.4 mm to 0.3 mm, showing only a slight barrier to heat exchange. By starting with a 0.7 mm or 1 mm thick sheet as required, the sidewalls can be thicker.

  The standard fluid connector 52 shown in FIG. 7 can be bonded by polymer bonding or other compatible glass bonding means.

  Since the above-described forming method can easily produce a pair of complementary channel patterns on the upper and lower surfaces of the forming sheet 32, one unique application of the microfluidic device thus formed is heat exchange. is there. As shown in FIG. 8, the channel on one side of the molded sheet 32 contains the first fluid F1, while the channel on the opposite side of the molded sheet 32 may contain the second fluid F2. Alternating channels are separated by a thin glass plate, which allows for quick and efficient heat transfer.

  FIG. 9 shows a plan view of one possible arrangement of alternating channels as in FIG. 8 in a microfluidic circuit. The channels 54 may be arranged in a straight line and in parallel, including access holes 56 provided at each end of each channel. Such channels can be used for two fluids in alternating channels with opposite flow, as suggested by the arrows and shading in the figure. Or, if necessary, other forms with parallel flow can be used for high performance heat exchange.

  FIG. 10 shows a plan view of another possible arrangement of alternating channels as in FIG. In FIG. 10, two alternating channels 54 include access holes 56 at the outer edge and the center of the helix and are placed together in a coaxial helix.

  Microchannel arrangements made by the methods described herein need not be limited to alternating and non-communication channel arrangements such as those shown in FIGS.

  For example, the mold in which the molded sheet 32 is formed as needed can be designed to minimize some or all channels on one side of the molded sheet 32. As a result, normal channels are interspersed in the minimized channels 60, as shown in the microfluidic device 50 of FIG. The resulting minimized channel may then be completely removed from the fluid circuit design. If desired, the minimized channel 60 can be filled with air, helium, other gases, or an incomplete vacuum as an alternative to insulate the adjacent fluid circuit channels as an alternative. Conversely, if a high thermal mass, relatively high thermal conductivity, and temperature uniformity are required, the minimized channel can be filled with water or other fluid.

  An embodiment of a device according to the invention having a minimized channel size on one side of the molded sheet is shown in the plan view of FIG. In this embodiment, the minimized channel 60 is not included in the microfluidic circuit, and a non-minimized channel 54 is provided including an access hole 56. In an embodiment such as that shown in FIG. 12, it is possible to block non-minimized channels with a single plate.

  In another embodiment of the microfluidic device of the present invention, an opening for fluid exchange may be provided as desired between the fluid channel on one side of the molded sheet 32 and the complementary fluid channel on the opposite side. This can be done by removing selected portions of the channel walls in the molded sheet 32. For example, by removing the material in the dashed boundary 41 shown in FIG. 13 from the shaped sheet 32 (by grinding, drilling, or other suitable method), fluid can flow between adjacent alternating channels 43 and 45. Bonds or through holes can be provided. Since the material to be removed does not need to extend long along the channel (in the direction inside or outside of the figure), the molded sheet can maintain its structural integrity substantially.

The microfluidic device of the present invention is available from Corning 0211, Corning 7059, Corning 1737 and Glaverbel Group (1170 Brussels, Belgium) available from Corning Incorporated, Corning, New York, USA. It has been successfully manufactured using a variety of glass constructions including “Glaverbel D 263”. Among these, “Corning 1737” shows the smallest thermal expansion coefficient of about 37.6 × 10 ⁻⁷ C. The microfluidic device formed from “Corning 1737” is suitable for use at a fluid temperature of 650 ° C. or lower. Aluminum borosilicates such as “Kerable” available from Keraglass (77 Bagneau sur Loing, France) can also be used. After the microfluidic device is formed as described above, “Kerable” is converted into ceramic glass (Vitroceram) by ceramization and exhibits an extremely low coefficient of thermal expansion of about −2 × 10 ⁻⁷ .

  As yet another embodiment of the present invention, two glass materials having reasonably close coefficients of thermal expansion can be used to form a single microfluidic device. For example, the upper and lower sheets used to close the passage in the element 50 can be formed from “Pyrex 7740” (see FIGS. 5 and 6), while the molded sheet 32 can be formed from “Corning 1737”. The difference in softening point of about 100 ° C. between these two glass materials allows heat sealing at about 780 ° C. This lower heat sealing temperature may help to prevent deformation of the molded sheet 32 after vacuum forming.

<Preferred manufacturing process>
The isothermal process described above is performed for the construction of a prototype, and is very suitable for small-scale manufacturing. A more cost effective and efficient production process is described below with reference to FIGS. 14 (A) to 14 (F).

  As shown in FIG. 14A, a sticky glass mass 70 is fed onto heated heated rollers 72, 74 from a tank feeder (not shown). The soft glass sheet 76 is vacuum formed immediately after being developed on the moving mold 78 to form a molded sheet 80 as shown in FIG. 14B, and the thickness thereof is reduced by vacuum drawing. Reduced to soft glass sheet 76. Next, in a second stage, which is immediately performed, the second soft glass sheet 82 is placed on the molded sheet 80 as shown in FIG. 14 (C). As shown in FIG. 14D, the second soft glass sheet immediately closes the upper surface of the molded sheet 80 to form a closed upper channel 90. Accordingly, the upper channel 90 is quickly formed and closed in a short time of about 5 to 10 seconds. The molded sheet having the closed upper channel 90 is then removed from the mold and placed on the support 82 in an inverted manner. The complementary fluid circuit that was not occluded in the previous stage is then covered with a third soft glass sheet 84 as shown in FIG. 14 (E), forming an occluded lower channel 100, resulting in The microfluidic device 50 of FIG. 14 (F) is obtained.

  For example, the preferred thermal conditions for forming “7740 Pyrex” are a roller heated to 650 ° C. and glass feed at 1350 ° C. onto a mold. The release material is preferably gas black derived from acetylene cracking. As the glass sheet becomes thinner, the roller temperature should increase. A sheet that has been rolled to 0.8 mm and vacuum formed is illustrated by way of example, with the glass thickness at the bottom of the formed sheet being less than 0.2 mm.

  The microfluidic device of the present invention and the microfluidic device produced by the process of the present invention need not be limited to designs having substantially vertical channel walls. FIG. 15 shows a cross-sectional view of a microfluidic device 50 having a triangular channel 40. This and other structures are easily achievable with the present invention.

  The process and method of the present invention allows the formation of reproducible and reliable very thin walled glass microchannels. The resulting microfluidic device of the present invention is particularly suitable for high performance microfluidic heat exchange.

  Compared to other methods of forming microfluidic devices, the current invention allows the wall area between adjacent channels to be increased relative to the cross-sectional area of the channel. The large wall area is mainly attributed to a relatively high channel aspect ratio (ratio of channel height to channel width) of 2: 1 or more that can be achieved with the disclosed method.

2 is a cross-sectional view of a mold 20 and a vacuum box 24 useful in connection with the present invention. It is sectional drawing of FIG. 1 after arrange | positioning the thin plate 30 on a metal mold | die. It is sectional drawing of FIG. 2 after vacuum-forming the thin plate 30 so that the shaping | molding sheet | seat 32 may be formed. FIG. 4 is a cross-sectional view after the molded sheet 32 of FIG. 3 is removed from the mold 20. FIG. 5 is a cross-sectional view of an assembly 38 including the molded sheet 32, the upper flat plate 34, and the lower flat plate 36 of FIG. 6 is a cross-sectional view of a microfluidic device 50 formed by gluing together the assembly of FIG. 5 according to an embodiment of the present invention. FIG. 7 is a cross-sectional view of the microfluidic device 50 of FIG. 6 including a fluid connector 52. FIG. 7 is a cross-sectional view of the microfluidic device of FIG. 6 showing alternating channels to which the first fluid F1 and the second fluid F2 can be assigned. FIG. 2 is a plan view of a microfluidic circuit design having parallel channels 54 each containing two access holes 56, possibly useful for devices of the present invention. FIG. 6 is a plan view of another microfluidic circuit design, having concentric helical alternating channels, each containing an access hole in the center and a spiral end, useful in some cases with the device of the present invention. 2 is a cross-sectional view of a microfluidic device 50 that includes a minimized channel 60. FIG. FIG. 3 is a plan view of another microfluidic circuit design including a minimized channel 60 that is useful in some cases with devices of the present invention. FIG. 5 is a cross-sectional view of the molded sheet 32 of FIG. 4 showing the location (inside the dashed boundary 41) where material can be removed to allow fluid exchange between adjacent alternating channels 43 and 45; (A)-(F) are the cross sections showing the specific stage of the presently preferred invention method for forming the element of the present invention. 4 is a cross-section of another embodiment of a microfluidic device 50 having triangular channels 40.

Claims (10)

  A microfluidic device comprising a molded sheet of glass or glass ceramic bonded to at least one sheet of glass or glass-ceramic material, wherein the molded sheet forms a microchannel .   The molded sheet of glass or glass-ceramic material is bonded between two sheets each of glass or glass-ceramic material to form complementary microchannels. Microfluidic device.   The molded sheet is made of a first glass material, the two sheets are each made of a second glass material, and the first glass material has a higher softening point than the second glass material. The microfluidic device according to claim 1, wherein the microfluidic device is a microfluidic device.   4. The molded sheet according to claim 1, wherein the molded sheet between adjacent microchannels separated by the molded sheet has a thickness in the range of about 0.2 mm to about 0.7 mm. The microfluidic device according to 1.   4. The molded sheet according to any one of claims 1 to 3, wherein the molded sheet between adjacent microchannels separated by the molded sheet has a thickness in the range of about 0.7 mm to about 3 mm. Microfluidic device.   The microfluidic device further comprising at least one through-hole penetrating through the molded sheet, wherein the through-hole enables fluid exchange between a pair of adjacent microchannels. 6. The microfluidic device according to any one of 1 to 5. A method of forming a microfluidic device, comprising:
A step of supplying a mold, a step of positioning a softened sheet made of glass or ceramic capable glass on the entire surface of the mold, and a gas pressure difference between the softened sheet so that the softened sheet is in close contact with the mold Forming a microchannel on at least one surface of the softened sheet, and adhering a sheet made of glass or ceramics on the entire mold surface to at least one surface of the softened sheet Substantially occluding the microchannel.   The method of claim 7, further comprising ceramizing the sheet and the softening sheet.   9. The step of applying a gas pressure difference to the sheet so that the sheet is in close contact with the mold includes forming a vacuum between the sheet and the mold. Method.   The step of adhering a sheet made of glass or ceramizable glass on the entire surface of the mold and substantially closing the microchannel on the at least one surface of the sheet includes softening glass on the adhesion sheet. The method according to any one of claims 7 to 9, characterized in that the sheet is developed and the softened glass sheet is adhered to the contact sheet.

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