Abstract
The disclosure relates to a method for operating a microfluidic device that includes providing at least one first medium at a first location of the microfluidic device, transporting at least one first medium from a first location to a second location of the microfluidic device, the at least one first medium being surrounded by at least one second medium in such a way that the at least one first medium only borders on the at least one second medium and on fluid boundaries of the microfluidic device or only on the at least one second medium. The at least one first medium and the at least one second medium cannot be mixed with one another.
Claims
1. A method for operating a microfluidic device, comprising: providing at least one first medium at a first site of the microfluidic device, transporting the at least one first medium from the first site to a second site of the microfluidic device, wherein the at least one first medium is surrounded by at least one second medium such that the at least one first medium is adjacent only to the at least one second medium and to fluid boundaries of the microfluidic device or only to the at least one second medium, and wherein the at least one first medium and the at least one second medium are not miscible with one another.
2. The method as claimed in claim 1, wherein: the providing of the at least one first medium includes providing a specifiable volume of the at least one first medium in a chamber of the microfluidic device, the chamber has at least one port, and the specifiable volume of the at least one first medium in the chamber is separated and measured off by the at least one second medium outside the chamber flowing around the at least one port.
3. The method as claimed in claim 1, wherein: the providing of the at least one first medium includes providing multiple first media, and the transporting of the at least one first medium includes transporting the multiple first media such that the multiple first media are mixed in a chamber of the microfluidic device.
4. The method as claimed in claim 1, wherein the transporting of the at least one first medium includes transporting at least one portion of the at least one first medium and/or at least one portion of the at least one second medium at least intermittently by peristaltic pumping.
5. The method as claimed in claim 1, further comprising: removing at least one gas pocket before, during, or after the transporting of the at least one first medium.
6. The method as claimed in claim 5, wherein the microfluidic device is, at least during part of the removing of the at least one gas pocket, oriented such that one side of a section from which the at least one gas pocket is removed is tilted with respect to a horizontal plane.
7. The method as claimed in claim 5, wherein the removing of the at least one gas pocket includes changing a temperature of a fluid in which the at least one gas pocket is enclosed.
8. The method as claimed in claim 5, wherein the removing of the at least one gas pocket includes removing the at least one gas pocket by transport of the at least one first medium and/or the at least one second medium.
9. The method as claimed in claim 1, wherein: a shuttle polymerase chain reaction is carried out, and the at least one first medium is a reaction medium of the shuttle polymerase chain reaction.
10. A microfluidic device comprising: a first site; and a second site, wherein the microfluidic device is configured to be provided at least one first medium at the first site and to transport the at least one first medium from the first site to the second site, the at least one first medium being surrounded by at least one second medium such that the at least one first medium is adjacent only to the at least one second medium and to fluid boundaries of the microfluidic device or only to the at least one second medium, and the at least one first medium and the at least one second medium are not miscible with one another.
Description
[0048] Further details of the invention and exemplary embodiments, to which the invention is not restricted however, will be more particularly elucidated on the basis of the drawings, where:
[0049] FIGS. 1a to 1d: show four schematic representations of microfluidic devices having a first medium and a second medium
[0050] FIGS. 2a to 2c: show schematic representations of a microfluidic device in three successive points in time, wherein a volume of a first medium is separated and measured off,
[0051] FIGS. 3a to 3e: show schematic representations of a microfluidic device in five successive points in time, wherein a first medium is generated and a volume of the first medium is separated, measured off and transported away,
[0052] FIGS. 4a to 4e: show schematic representations of a microfluidic device in five successive points in time, wherein a first medium is separated, measured off and transported away in two subvolumes,
[0053] FIG. 5: shows a schematic representation of a microfluidic device in which a chamber is partially filled with a first medium,
[0054] FIGS. 6a to 6f: show schematic representations of a microfluidic device in six successive points in time, wherein two first media are mixed together,
[0055] FIGS. 7a to 7f: show schematic representations of a microfluidic device having multiple valves which are switched differently in six successive points in time for peristaltic pumping,
[0056] FIGS. 8a and 8b: show two schematic representations for peristaltic pumping,
[0057] FIGS. 9a to 9d: show schematic representations of a microfluidic device in four successive points in time, wherein peristaltic pumping is carried out,
[0058] FIGS. 10a to 10d: show schematic representations of a microfluidic device in four successive points in time, wherein a gas pocket is removed,
[0059] FIG. 11: shows schematic representations of a microfluidic device which has a tipped orientation,
[0060] FIGS. 12a to 12c: show schematic representations of a microfluidic device in three successive points in time, wherein a gas pocket is removed,
[0061] FIGS. 13a to 13d: show schematic representations of a microfluidic device in four successive points in time, wherein a shuttle PCR is carried out, and
[0062] FIG. 14 shows a schematic representation of a method for operating a microfluidic device as per any of the exemplary embodiments from the previous figures.
[0063] FIGS. 1a to 1d show how, in a microfluidic device 1, a liquid phase as first medium 2 can be enclosed between two oil phases as second medium 3. In this case, the first medium 2 can especially be initially charged with a defined volume. The volume of the first medium 2 can be defined by the fixed and precisely producible geometry of the microfluidic device 1. In this form, it is therefore also possible to initially charge a defined concentration of the first medium 2, especially when an analyte is concerned.
[0064] To move the volume of the first medium 2 without dilution of the analyte therein by diffusion, the first medium 2 is enclosed among the second medium 3 (shown here by two oil phases). Since oil and water do not mix, dilution of the first medium 2 by diffusion does not take place. This can allow microfluidic transport of a defined volume of the first medium 2 through a first channel 5 or out of a first chamber 4 without any losses. The first chamber 4 is connected to a first channel 5 via a first port 25 and to a second channel 6 via a second port 26. The first medium 2 and the second medium 3 are surrounded by fluid boundaries 24.
[0065] In particular, the first medium 2 can be pre-stored in the first chamber 4 (FIG. 1a) and be transported therefrom into the first channel 5 through the first port 25 (FIG. 1b). In the further course of the first channel 5, the first medium 2 can be enclosed among the second medium 3 (FIG. 1c). FIG. 1d shows a different situation, in which the first medium 2 is enclosed in a first chamber 4 of the microfluidic device 1.
[0066] FIGS. 2a to 2c and 3a to 3e show two embodiments of a microfluidic device, by means of which a defined volume of an aqueous phase as first medium 2 can be brought between two inert oil phases as second medium 3.
[0067] In the embodiment as per FIGS. 2a to 2c, a first chamber 4 of known volume is arranged between a first channel 5 and a second channel 6 in parallel to the first channel 5. The first chamber 4 is connected to a first channel 5 via a first port 25 and to a second channel 6 via a second port 26. By means of appropriate fluid control (e.g., by use of valves or a pressure equalization system), the flow can be set into various directions and channel compositions (e.g., as a flow only in the channels 5, 6 or as a flow from the second channel 6 through the first chamber 4 into the first channel 5). In a first step, an aqueous phase as first medium 2 flows through the first chamber 4 (FIG. 2a) initially filled with a second medium 3 and the flow is stopped, with the result that the first chamber 4 is completely filled with the first medium 2 (FIG. 2b). The adjacent channels 5, 6, but not the first chamber 4, are subsequently flushed through with oil as second medium 3, with the result that the first chamber 4 is surrounded by two oil-filled channels 5, 6 (FIG. 2c). Now, what can be set is a flow from the second channel 6 through the first chamber 4 into the first channel 5. In this case, the three phases (i.e., the second medium 3 in the second channel 6, the first medium 2 in the first chamber 4 and the second medium 3 in the first channel 5) move in a laminar manner without mixing.
[0068] In a second embodiment as per FIGS. 3a to 3e, the first chamber 4 borders only on a first channel 5 (via a first port 25) and not on a first channel 5 and a second channel 6 as in the case of the first exemplary embodiment as per FIGS. 2a to 2c. Part of the first chamber 4 is open or (as shown) separated from the surroundings of the microfluidic device 1 by a gas-permeable membrane 7, meaning that air can be exchanged and/or pressure can be equalized between the first chamber 4 and the surroundings. The gas-permeable membrane 7 can especially be used as a sample input region, especially for applications in which only small quantities of a sample are introduced into the microfluidic device.
[0069] Moreover, FIG. 3a shows that a sample 8 (e.g., as a solid body or Lyobead) is present in the first chamber 4. To dissolve the sample 8 and/or to fill the first chamber 4, the first channel 5 is first filled with oil as second medium 3 in order to vent the entire system. The first chamber 4 is then filled with a liquid phase as first medium 2 (FIG. 3b). When the chamber is completely filled, oil as second medium 3 reflows through the first channel 5 and the first chamber 4 is thus completely closed off (FIG. 3c). The first medium 2 can then be re-enclosed among an oil phase as second medium 3 by pumping out the first chamber 4 via the first channel 5 (FIG. 3d) until the first chamber 4 is empty (FIG. 3e).
[0070] FIGS. 4a to 4e show a further exemplary embodiment of a microfluidic device 1, by means of which a defined volume of an aqueous phase as first medium 2 can be brought between two inert oil phases as second medium 3. Here, in contrast to the exemplary embodiment from FIGS. 2a to 2c, two subvolumes of the first medium 2 are successively removed from the first chamber 4. The starting point shown in FIG. 4a largely corresponds to the representation in FIG. 2c. As a result of a flow of the second medium 3 from the second channel 6 into the first channel 5, a portion of the first medium 2 is removed from the first chamber 4 (FIG. 4b). Thereafter, the second medium 3 reflows through the first channel 5 (FIG. 4c). Afterwards, the remaining portion of the first medium 2 is removed from the first chamber 4 (FIG. 4d). As can be seen in FIG. 4e, the first medium 2 is, in the further course of the first channel 5, present in two portions which are each enclosed by the second medium 3. FIGS. 4a to 4e therefore show that a two-phase system (having first medium 2 and second medium 3) can also be utilized for filling a microfluidic chamber with an aqueous phase (as first medium 2) only partially without any bubbles. The remaining volume of the chamber can be appropriately compensated for with an inert oil phase (as second medium 3). This can allow a dynamic adjustment of reaction volumes.
[0071] FIG. 5 shows one state from the exemplary embodiment from FIGS. 4a to 4e, in which the first chamber 4 is part-filled with the first medium 2 and part-filled with the second medium 3.
[0072] FIGS. 6a to 6f show an exemplary embodiment of a microfluidic device 1 in which two aqueous phase fluids (as a first medium 2 and a further first medium 9) are mixed. In this case, a first chamber 4 having a defined volume is half-filled with the first medium 2 (FIG. 6a). The first chamber 4 is connected to a first channel 5 via a first port 25 and to a second channel 6 via a second port 26. The supplying first channel 5 is then completely refilled with oil as second medium 3 (FIGS. 6b and 6c). After that, the first channel 5 is filled with the further first medium 9 (FIG. 6d). The first chamber 4 is then (preferably slowly) filled up with the further first medium 9, with the result that the entire first chamber 4 is filled with the two first media 2, 9 in the correct ratio. The first channel 5 is then refilled with the second medium 3, with the result that the two first media 2, 9 in the first chamber 4 are resurrounded by the second medium 3 in the channels 5, 6 (FIG. 6e). Owing to diffusion, the two first media 2, 9 in the first chamber 4 can mix rapidly, especially when the respective volumes are small. The result is shown in FIG. 6f, in which a mixture 10 of the two first media 2, 9 is present in the first chamber 4. The mixing process can be quickened by a temperature change. If desired, (bio)chemical reactions can also be carried out upon mixing. The combination of defined pumping processes and specified chamber geometries can allow mixing with different ratios between the first media 2, 9.
[0073] FIGS. 7a to 7f show how fluids can be moved with controlled speed in a linear or circular channel system of a microfluidic device by means of valves. Valves in the microfluidic device can be used not only for opening and closing microfluidic paths, but can also be used as peristaltic pumps. Along a desired microfluidic path (which can be linear or circular and is shown here as a linear first channel 5), what is formed by the valves as a result of serial opening and closing is a peristaltic pump. FIGS. 7a to 7f show the principle using the example of three valves 11, 12, 13 lying next to one another. Here, a circle indicates an open valve, whereas a cross indicates a closed valve. The valve status can also be represented digitally by, for example, a “1” signifying “open” and a “0” signifying “closed”. The valve status sequence 100 (FIG. 7e), 110 (FIG. 7d), 010 (FIG. 7c), 011 (FIG. 7b), 001 (FIG. 7a), 101 (FIG. 7f) generates a movement from left to right in the representation shown. The sequence 001 (FIG. 7a), 011 (FIG. 7b), 010 (FIG. 7c), 110 (FIG. 7d), 100 (FIG. 7e), 101 (FIG. 7f) generates a quasi-laminar flow from right to left.
[0074] Moreover, FIGS. 8a and 8b show that the valves 11, 12, 13 need not be placed next to one another, but can be arranged as desired along the first channel 5. This has the advantage that there is no need to place specific pump valves and that valves 11, 12, 13, which are present anyway, can be used instead. The flow rate can be set at a particular interval by means of a duration of a pause between successive valve positions.
[0075] FIGS. 9a to 9d show how the embodiment as per FIGS. 2a to 2c can be realized in a multichamber system (comprising a first chamber 4, a second chamber 14 and a third chamber 15) by peristaltic pumping. In a first step, the microfluidic device 1 is completely filled with an oil phase as second medium 3 (FIG. 9a). This need not necessarily be done by peristaltic pumping. When the microfluidic device 1 is filled, a fifth valve 18 and a sixth valve 19 between the chambers 4, 14, 15 and a first channel 5 are closed (FIG. 9b). A channel 5 arranged laterally in relation to the chambers 4, 14, 15 is then at least partially filled with the first medium 2. When this state is reached, the fifth valve 18 and the sixth valve 19 to the chambers 4, 14, 15 are opened and peristaltic pumping is carried out using the valves 11, 12, 13 until the first chamber 4 is completely filled with the first medium 2 (FIGS. 9c and 9d). The pump can be coupled to an optical feedback system, and be automatically stopped upon complete filling. Alternatively, just one trapped aqueous plug having the chamber volume can be introduced into the first chamber 4. When the first chamber 4 is completely filled, the fifth valve 18 to the first chamber 4 is closed and the first channel 5 is completely reflushed with the second medium 3 (by opening a fourth valve 17), with the result that only the first medium 2 remains in the first chamber 4 (FIG. 9d).
[0076] FIGS. 10a to 10d show how a two-phase system (having a first medium 2 and a second medium 3) can be used to remove gas pockets 16 in the first medium 2. In this structure, gas pockets 16 such as disruptive bubbles are removed by a temperature gradient. To this end, three microfluidic chambers 4, 14, 15 are arranged one after another and connected to one another by means of a respective small channel. Each of the three chambers 4, 14, 15 is individually heatable. The first chamber 4 is, then, set to the highest temperature and the second chamber 14 and the third chamber 15 to a lower temperature. At the same time, the heated gas bubbles 16 move from the first medium 2 into the colder second medium 3. When gravity is still acting along the chamber geometry (as shown), the gas pockets 16 rise to the very top owing to the lower density. What is therefore formed is a fluid system in which the first medium 2 is present in the first chamber 4, and the second chamber 14 and the third chamber 15 are filled with the second medium 3. In the third chamber 15, a gas phase can form. In the second medium 3, the temperature can then be raised again in order to ensure that the gas settles at the very top. The phase system can be shifted by one chamber in each case, with the first medium 2 then being situated for example in the second chamber 14 and the bubble-free second medium 3 in the third chamber 15. The bubble-containing first chamber 4 is then eliminated from the chamber system. The first chamber 4 can be closed or be refilled with the second medium 3.
[0077] FIG. 11 shows how an inclination of the microfluidic device 1 and thermally different zones can be utilized for the removal of gas pockets 16 as per FIGS. 10a to 10d. There is no need for gravity to act fully. Instead, an inclination (e.g., of 30°) is possible too. FIG. 11 shows a horizontal plane 21 and an angle 22 between the horizontal plane 21 and one side 23 of the microfluidic device 1 from FIGS. 10a to 10d. The three-chamber system shown in FIGS. 10 to 10d can be oriented such that the first chamber 4 containing the first medium 2 is at the bottom (c.sub.1 in FIG. 11). Each chamber 4, 14, 15 is then in its own thermal zone (T.sub.1, T.sub.2, T.sub.3). At the same time, what can be brought about gravity is that the light gas is shifted to the upper end of the third chamber 15 from the gas pocket 16 by heating (c.sub.3 in FIG. 11).
[0078] FIGS. 12a to 12c show an exemplary embodiment in which a gas pocket 16 as for FIGS. 10a to 10d and 11 can be removed. In FIGS. 12a to 12c, it is assumed that the gas pocket 16 has been removed from the first medium 2 as per the method as per FIGS. 10a to 10d with the aid of the conditions from FIG. 11 (FIG. 12a). To now remove the gas pocket 16 from the microfluidic device 1, a second medium 3 is subsequently shifted from the bottom through the three chambers 4, 14, 15 until the first medium 2 has been completely shifted from the first chamber 4 into the second chamber 14. At the same time, the gas pocket 16 is displaced from the third chamber 15 into the first channel 5 (FIG. 12b). Thereafter, the gas can be discharged from the microfluidic device 1 as a result of subsequent shifting of second medium 3 through the first channel 5 (but not through the chambers 4, 14, 15), with the result that a completely bubble-free microfluidic device 1 remains (FIG. 12c).
[0079] FIGS. 13a to 13d show how a bubble-free shuttle PCR can be carried out using a two-phase system and the combination of the above-described removal of a gas pocket 16. In a shuttle PCR, there is, in contrast to a thermal cycler, no dynamic change in the temperature of heaters, but there is shifting of the reaction mixture between different heaters having constant temperatures. To carry out a shuttle PCR, the microfluidic device 1 can be designed especially as per FIGS. 7a to 7f, 10a to 10d and 11. In the arrangement of three chambers 4, 14, 15 and a first channel 5, what are preferably envisaged are three valves 11, 12, 13, which form a peristaltic pump. The PCR reaction mixture (as first medium 2) is preferably initially charged in the first chamber 4 without any bubbles, whereas the second chamber 14 and the third chamber 15 and also the first channel 5 are filled with the second medium 3 (FIG. 13a). The chambers 4, 14, 15 are set to the appropriate temperatures required for the PCR. The first medium 2 as PCR mixture can then be held in the appropriate chambers 4, 14, 15 for respectively intended times before it is pumped peristaltically into the next of the chambers 4, 14, 15 (FIGS. 13b to 13d). What is shown in particular is how back-and-forth movement (shuttling) can be carried out between two temperatures. By reversing the pumping frequency, as described on the basis of FIGS. 7a to 7f, it is possible to pump in both directions.
[0080] FIG. 14 shows a method for operating a microfluidic device 1 as per any of the exemplary embodiments from the previous figures. The method comprises the following steps: [0081] a) providing at least one first medium 2, 9 at a first site of the microfluidic device 1, [0082] b) transporting the at least one first medium 2, 9 from the first site to a second site of the microfluidic device 1, wherein the at least one first medium 2, 9 is surrounded by at least one second medium 3 such that the at least one first medium 2, 9 is adjacent only to the at least one second medium 3 and to fluid boundaries 24 of the microfluidic device 1 or only to the at least one second medium 3, and wherein the at least one first medium 2, 9 and the at least one second medium 3 are not miscible with one another.
[0083] Furthermore, the method preferably comprises the following method step (drawn in with dashed lines), which is carried out before, during or after step b): [0084] c) removing at least one gas pocket 16.
[0085] In the example of FIG. 14, step c) is carried out after step b).
