Device for the capillary transport of liquids

Abstract

Disclosed is a device for the directed capillary transport of liquids, comprising at least two capillaries (8, 9, 33, 54, 55), the at least two capillaries (8, 9, 33, 54, 55) being designed such that the liquid can be transported in at least some regions in a passive, directed and capillary manner, characterised in that at least two of the capillaries (8, 9, 33, 54, 55) are interconnected in the direction of transport of the liquid via at least one capillary passage conduit (20, 23, 28, 29, 34, 40, 41, 59, 63). The invention is intended for use in the separation of components from a fluidic substance and/or in oil/water separation. A production method is characterised in that at least one part of the capillary structure is generated by means of laser irradiation, by means of a moulding tool, in particular a sintering mould, by means of a milling process, in particular by means of a micro-milling process, or by means of EDM.

Claims

1. A device for the directed capillary transport of liquids, said device comprising at least two capillaries each having at least one side wall, wherein said at least two capillaries are formed such that a passive directed capillary transport of the liquid is performed at least in certain regions, and at least one capillary passage channel wherein said at least two capillaries are connected to one another in the direction of transport of the liquid by said at least one capillary passage channel, wherein at least two of said capillaries each have a plurality of transport sections which, as seen in the direction of transport, succeed one another and provide for passive directed capillary transport over the entire transport section, wherein at least two of said transport sections end in a stop point which is operable to interrupt said passive directed transport of liquid, and wherein at least one of said at least one passage channel has a channel outlet positioned downstream of the stop point, as seen in the direction of transport, and adjacent to said stop point.

2. The device claimed in claim 1 wherein at least one of said at least one transport section has a cross section of the capillary which is reduced in the direction of transport.

3. The device claimed in claim 2 wherein at least some of said directed capillary transport is brought about by a material of at least one of said capillary side walls.

4. The device claimed claim 1 wherein at least some of said directed capillary transport is brought about by a material of at least one of said capillary side walls.

5. The device claimed in claim 1 wherein at least one of the stop points is formed by an enlarged transport cross section.

6. The device as claimed in claim 1, wherein at least one of the stop points is formed by a change in the surface material of at least one of said capillary side walls.

7. The device claimed in claim 1 wherein at least some of said at least two capillaries have a sponge-like structure.

8. The device claimed in claim 1 wherein at least one of said at least two capillaries is formed by a fiber material.

9. The device claimed in claim 8 wherein at least one of said at least two capillaries comprises at least one hollow fiber.

10. The device as claimed in claim 9 further comprising an inner capillary structure surrounded by at least one of said at least one hollow fiber.

11. The device claimed in claim 1, wherein at least one of said at least two capillaries is partially open.

12. The device claimed in claim 11 wherein at least one of said at least one partially open capillary is part of a surface.

13. The device claimed in claim 11 wherein at least one of said at least two capillaries is formed by a fiber material.

14. The device claimed in claim 13 wherein at least one of said at least two capillaries is formed by at least one hollow fiber.

15. The device claimed in claim 14 further comprising an inner capillary structure surrounded by at least one of said at least one hollow fiber.

16. A device for the directed capillary transport of liquids, said device comprising at least two capillaries each having at least one side wall, wherein said at least two capillaries are formed such that a passive directed capillary transport of the liquid is performed at least in certain regions, and at least one capillary passage channel wherein said at least two capillaries are connected to one another in the direction of transport of the liquid by said at least one capillary passage channel, wherein at least two of said capillaries each have a plurality of transport sections which, as seen in the direction of transport, succeed one another and provide for passive directed capillary transport over the entire transport section, wherein at least two of said transport sections end in a stop point which is operable to interrupt said passive directed transport of liquid, and wherein at least one of said at least one passage channel has a channel outlet positioned downstream of the stop point of a first one of the at least two capillaries, as seen in the direction of transport, and adjacent to said stop point wherein a stoppage of the liquid at said stop point is overcome by the supply of liquid from a second one of the at least two capillaries by way of said passage channel.

17. The device claimed in claim 16 wherein at least one of said at least one transport section has a cross section of the capillary which is reduced in the direction of transport.

18. The device claimed in claim 16 wherein at least one of said at least two capillaries is formed by a fiber material.

19. The device claimed in claim 16, wherein at least one of said at least two capillaries is partially open.

20. The device claimed in claim 19 wherein at least one of said at least two capillaries is formed by a fiber material.

Description

(1) FIG. 1 shows a detail of a capillary structure according to the invention,

(2) FIG. 2 shows the capillary structure from FIG. 1 with menisci that have progressed further,

(3) FIG. 3 shows the capillary structure from FIGS. 1 and 2 with menisci that have progressed further,

(4) FIG. 4 shows a sawtooth structure that is known from the prior art, within a capillary,

(5) FIG. 5 shows the capillary structure of FIGS. 1 to 3 in a mirror-image illustration, for clarifying the fact that backward transport of the liquid is inhibited,

(6) FIG. 6 shows in cross section a capillary structure that has been generated from fibers,

(7) FIG. 7 shows the capillary structure according to FIG. 6, in three different sections,

(8) FIG. 8 shows a further capillary structure of fibers,

(9) FIG. 9 shows the capillary structure according to FIG. 8 in three different sections,

(10) FIG. 10 shows a capillary structure comprising an inner fiber and an encasing fiber,

(11) FIG. 11 shows a capillary structure similar to FIG. 1, in a first stage of the liquid progress,

(12) FIG. 12 shows the capillary structure according to FIG. 1, in a second stage of the liquid progress,

(13) FIG. 13 shows the capillary structure according to FIG. 1, in a third stage of the liquid progress, and

(14) FIG. 14 shows the capillary structure according to FIG. 1, in a fourth stage of the liquid progress.

(15) FIG. 4 shows an asymmetric surface structure, known in principle from the prior art and in this case having a one-sided sawtooth shape, of a capillary 1 having a smooth side wall 2 and a sawtooth-shaped side wall 3, between which there is located a drop of liquid 4. The geometry of the capillary results in different curvatures of a front liquid surface 5 and a rear liquid surface 6. At the front liquid surface 5 there is a pressure difference, wherein the pressure P.sub.K.i directed toward the interior of the drop is smaller than the outwardly directed pressure P.sub.K.a. In the other direction, by contrast, the curvature is directed in opposition to this, and the outwardly directed pressure P.sub.K.a is smaller than the pressure P.sub.K.i directed into the interior of the drop. If no external forces are present, the pressure relationships have the result that the liquid is transported in capillary manner in the direction of transport (arrow 7), wherein transport continues until the drop 4 has adopted a stable position.

(16) FIGS. 1 to 3 show diagrammatically and in cross section an embodiment of a capillary structure as may be provided in a device according to the invention.

(17) FIG. 1 shows two capillaries which, in the text below, are designated the upper capillary 8 and the lower capillary 9. The properties “upper” and “lower” merely relate to the illustration in the drawing and not to a possible orientation of the capillary in space. This may be a partially open capillary structure having an upper side wall 10 and a lower side wall 11, between which there is arranged a middle structure 12. The capillary structure is downwardly delimited, perpendicular to the plane of the drawing, by a floor (not illustrated separately here). The capillary structure is open on the opposite side to the floor.

(18) The manner in which a liquid mass 13 progresses within the capillary structure, from left to right in the direction of transport 14, is described below.

(19) In the lower capillary 9, directed transport of the liquid mass 13 first runs as far as the corner point 15 of the middle structure 12. The corner. point 15, like every other corner point mentioned below, defines a respective stop point for the liquid transport in the capillary concerned.

(20) Correspondingly, the liquid mass runs in the upper capillary 8, as a result of the interaction of the geometry and contact angle 16, as far as the corner point 25. For the respective end positions, the upper meniscus 18 is drawn in for the upper capillary 8 and the lower meniscus 19 is drawn in for the lower capillary 9. In addition, the position 18a of the meniscus 18 at an earlier stage is drawn in for the upper capillary 8.

(21) In the end position drawn in with meniscus 18, the liquid mass 13 in the upper capillary 8 has already gone beyond the inlet of a passage channel 20 which connects the upper capillary 8 to the lower capillary 9. The passage channel 20 is itself also a capillary, and for this reason liquid from the liquid mass 13 moves out of the upper capillary and through the passage channel 20 to the lower capillary 9 as a result of capillary forces, and there forms a further meniscus 21 which runs as far as the corner point 15. At this point, the two menisci 19 and 21 are connected and combine to form a common new meniscus 22, as drawn in in FIG. 2, in an intermediate position 22a and a leading-edge end position 22. On the way to the leading-edge end position 22, the liquid mass 13 has flowed into a second passage channel 23 which in turn connects the lower capillary 9 to the upper capillary 8. The liquid from the lower liquid mass 13 runs through the passage channel 23 and into the upper capillary 8, as a result of the capillary forces, and there forms the further meniscus 24 which is combined at the corner point 25 with the further meniscus 18 to form a new common meniscus 26, which is illustrated in FIG. 3 on its way to the corner point 27. The described behavior of the liquid mass 13 continues through the further passage channels 28 and 29 such that the liquid mass 13 is transported further in the direction of transport 14.

(22) This procedure is achieved for example by putting a drop of liquid on the open side of the capillary structure. FIG. 5 shows the capillary structure from FIGS. 1 to 3 in mirror image, such that the direction of transport 14 prevailing in FIGS. 1 to 3 has in this case to be illustrated running from right to left. In the direction opposed to the direction of transport 14, progress of the liquid mass 13 is reduced or inhibited, since the capillaries are widened in the region of the menisci 30 and 31 that are drawn in such that the menisci have a markedly smaller curvature or are given a straight or convex shape. Thus, the liquid mass 13 does not reach the passage channels 40 or 41 in this direction without the supply of external forces, or is at least slowed down, the result of this being that a directed transport of liquid is achieved by means of the capillaries 8 and 9. A drop of liquid which is put onto a structure of this kind or a plurality of such capillary structures is thus distributed solely or at least predominantly in the direction of transport 14.

(23) The illustrative drawing in FIGS. 1 to 3 serves to schematically indicate the principle. FIGS. 11 to 14 illustrate a further variant on a capillary structure according to the invention which has been successfully tested in practice. Here, unlike the situation in FIGS. 1 to 3, outer side walls 50 and 51 are provided with asymmetric sequences of changes in cross section.

(24) Transport of a liquid mass 52 runs in the direction of the arrow 53. The liquid mass 52 runs in the direction of transport 53 in an upper capillary 54 as far as a first stop point 56. A liquid meniscus 57 adopts a largely uncurved shape.

(25) In a lower capillary 55, a lower branch of the liquid mass 52 forms a further meniscus 58 which is still pronouncedly concave (curved toward the liquid interior) in form and progresses in the direction of transport 53 in the lower capillary 55.

(26) In FIG. 12, the lower branch of the liquid mass 52 with its meniscus 58 has progressed further because of the capillary forces and has passed the inlet of a passage channel 59, which is also capillary. In the passage channel 59 there is formed a further meniscus 60 which progresses in the passage channel 59 until it is combined with the meniscus 52 at the stop point 56 and forms the new meniscus 61 (FIG. 13). In the meantime, the meniscus 58 in the lower capillary 55 has reached the further stop point 62. The meniscus 61 that progresses because of the capillary forces passes the inlet to the further passage channel 63, as a result of which a further meniscus 64 forms there (FIG. 14), and this will combine with the meniscus 58 of the lower capillary 55 at the stop point 62. Progress of the mechanism described results in directed transport in the direction of transport 53.

(27) An alternative capillary structure is shown in FIGS. 6 and 7, wherein the capillary structure is formed by fibers 32. In relation to a plane that is perpendicular to their longitudinal direction, the fibers have an asymmetric structure, the result of which is directed transport through the capillaries 33 formed between the fibers 32. In the sectional drawings “A”, “B” and “C” in FIG. 7, the arrangement of fibers 32 in a tightly packed arrangement is clear. Moreover, the sectional drawings “B” and “C” illustrate passage channels 34.

(28) Here too, the interaction between the capillaries 33 and the passage channels 34 provides for continuous progress of the liquid mass (not illustrated here) in a preferred direction, namely upward in FIG. 6.

(29) The capillary structure in FIGS. 6 and 7 may be delimited by side walls, which are not illustrated here. The capillary structure may be partially open or closed.

(30) FIGS. 8 and 9 illustrate an alternative arrangement of the fibers 32 in a more tightly packed arrangement, in an illustration corresponding to FIGS. 6 and 7. According to this, the fibers 32 are placed in relation to one another such that the asymmetry of the capillary cavities is increased. The tighter packing enables stop points to be overcome more easily by combining menisci.

(31) FIG. 10 shows an outer hollow fiber 36 which encases an inner fiber 35 and has numerous openings 37 on its periphery. By this means, a further variant on a capillary structure may be formed by packing a plurality of such combinations of encasing hollow fiber 36 and inner fiber 35 into a bundle. Here, the openings 37 form the passage channels between adjacent capillaries. The number of openings 37 may also be selected to be markedly smaller than that illustrated in FIG. 10. The decisive point is that the function of passage channels according to the invention is fulfilled. Each inner fiber 35 may be a solid fiber as illustrated in FIG. 10, or a hollow fiber. A plurality of inner fibers 35 may also be provided in the hollow fiber 36.

(32) TABLE-US-00001 List of reference numerals  1 Capillary  2 Side wall  3 Side wall  4 Drop of liquid  5 Front liquid surface  6 Rear liquid surface  7 Direction of transport  8 Upper capillary  9 Lower capillary 10 Side wall 11 Side wall 12 Middle structure 13 Liquid mass 14 Direction of transport 15 Corner point 16 Contact angle 18 Upper meniscus 18a Meniscus 19 Lower meniscus 20 Passage channel 21 Meniscus 22 Meniscus in end position 22a Meniscus in intermediate position 23 Passage channel 24 Meniscus 25 Corner point 26 Meniscus 27 Corner point 28 Passage channel 29 Passage channel 30 Meniscus 31 Meniscus 32 Fiber 33 Capillary 34 Passage channel 35 Inner fiber 36 Hollow fiber 37 Opening 40 Passage channel 41 Passage channel 50 Side wall 51 Side wall 52 Liquid mass 53 Direction of transport 54 Upper capillary 55 Lower capillary 56 Stop point 57 Meniscus 58 Meniscus 59 Passage channel 60 Meniscus 61 Meniscus 62 Stop point 63 Passage channel 64 Meniscus