Fluidics module, device and method for pumping a liquid

Abstract

A fluidics module rotatable about a rotational center includes first and second chambers and a compression chamber. First and second fluid channels are provided between the first and second chambers and the compression chamber, respectively. The flow resistance of the second fluid channel is smaller, for a flow of liquid from the compression chamber to the second chamber, than a flow resistance of the first fluid channel for a flow of liquid from the compression chamber to the first chamber. Upon rotation at a high rotational frequency, liquid is initially introduced from the first chamber into the compression chamber via the first fluid channel, so that a compressible medium is compressed within the compression chamber. Subsequently, the rotational frequency is reduced, so that the compressible medium within the compression chamber will expand and so that, thereby, liquid is driven into the second chamber via the second fluid channel.

Claims

1. A fluidics module rotatable about a rotational center, comprising: a first chamber including a fluid outlet; a compression chamber; a second chamber separate from the first chamber and including a fluid inlet; a first fluid channel between the fluid outlet of the first chamber and the compression chamber; a second fluid channel between the compression chamber and the fluid inlet of the second chamber, wherein the first fluid channel and the second fluid channel are fluidically coupled to the compression chamber at at least one radially outer area of the compression chamber, wherein a liquid may be centrifugally driven through the first fluid channel from the first chamber into the compression chamber, wherein the second fluid channel includes at least one portion whose beginning is located further outward radially than its end, wherein a flow resistance of the second fluid channel for a flow of liquid from the compression chamber to the second chamber is smaller than a flow resistance of the first fluid channel for a flow of liquid from the compression chamber to the first chamber, wherein, upon rotation of the fluidics module, a compressible medium within the compression chamber may be trapped and compressed by a liquid driven from the first chamber into the compression chamber by centrifugal force, and wherein liquid may be driven into the second chamber from the compression chamber through the second fluid channel by a reduction of a rotational frequency and by a consequent expansion of the compressible medium, and wherein the compression chamber permits the liquid driven from the first chamber into the compression chamber by centrifugal force to trap and compress the compressible medium in the compression chamber.

2. The fluidics module as claimed in claim 1, wherein a flow cross-section of the second fluid channel is larger than a flow cross-section of the first fluid channel.

3. The fluidics module as claimed in claim 1, wherein the fluid inlet of the second chamber is located further inward radially than the fluid outlet of the first chamber.

4. The fluidics module as claimed in claim 3, wherein the entire second chamber is located further inward radially than the first chamber.

5. The fluidics module as claimed in claim 1, wherein the second fluid channel comprises a syphon.

6. The fluidics module as claimed in claim 1, wherein the compression chamber comprises a fluid inlet to which the first fluid channel is fluidically coupled at the at least one radially outer area of the compression chamber, and a fluid outlet to which the second fluid channel is fluidically coupled at the at least one radially outer area of the compression chamber.

7. The fluidics module as claimed in claim 1, wherein the compression chamber comprises a fluid opening fluidically coupled to a channel section into which the first fluid channel and the second fluid channel lead.

8. The fluidics module as claimed in claim 1, wherein the first fluid channel comprises a valve which represents a higher flow resistance for a flow of fluid from the first chamber to the compression chamber than in the opposite direction.

9. A device for pumping a liquid, comprising: a fluidics module as claimed in claim 1, a drive configured to: subject the fluidics module to a first rotational frequency, in a first phase, that drives liquid from the first chamber through the first fluid channel into the compression chamber, where the compressible medium is thus trapped and compressed, filling levels of the liquid in the first fluid channel, the compression chamber and the second fluid channel adopting a state of equilibrium; and reduce the rotational frequency in a second phase such that the compressible medium within the compression chamber will expand and thereby drive liquid from the compression chamber through the second fluid channel into the second chamber.

10. The device as claimed in claim 9, further comprising: a unit that supports expansion of the compressible medium upon reduction of the rotational frequency.

11. The device as claimed in claim 10, wherein the unit for supporting comprises at least one of a pressure source for producing a pressure within the compression chamber, a heat source for heating the compressible medium, and a unit for effecting gas evolution due to chemical reactions.

12. The device as claimed in claim 1, wherein the compression chamber is a non-vented chamber.

13. A method of operating a fluidics module rotatable about a rotational center, the fluidics module comprising a first chamber including a fluid outlet, a compression chamber, a second chamber separate from the first chamber and including a fluid inlet, a first fluid channel between the fluid outlet of the first chamber and the compression chamber, and a second fluid channel between the compression chamber and the fluid inlet of the second chamber, wherein the first fluid channel and the second fluid channel are fluidically coupled to the compression chamber at at least one radially outer area of the compression chamber, wherein the second fluid channel includes at least one portion whose beginning is located further outward radially than its end, wherein a flow resistance of the second fluid channel for a flow of liquid from the compression chamber to the second chamber is smaller than a flow resistance of the first fluid channel for a flow of liquid from the compression chamber to the first chamber, the method comprising: rotating the fluidics module to centrifugally drive a liquid through the first fluid channel from the first chamber into the compression chamber to thereby trap and compress a compressible medium within the compression chamber by the liquid, and reducing the rotational frequency so that the compressible medium in the compression chamber expands to thereby drive at least a part of the liquid from the compression chamber through the second fluid channel into the second chamber.

14. The method as claimed in claim 13, further comprising supporting the expansion of the compressible medium upon reduction of the rotational frequency.

15. The method as claimed in claim 14, wherein supporting comprises at least one of subjecting the compressible medium to a pressure, heating the compressible medium, and effecting gas evolution within the compression chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which:

(2) FIG. 1 schematically shows a top view of a section of an embodiment of an inventive fluidics module;

(3) FIG. 2 shows schematic representations for illustrating the function of the embodiment shown in FIG. 1;

(4) FIGS. 3 and 4 show schematic side views for illustrating embodiments of inventive devices; and

(5) FIG. 5 shows a schematic top view of a section of an alternative embodiment of an inventive fluidics module.

DETAILED DESCRIPTION OF THE INVENTION

(6) Before explaining embodiments of the invention in more detail, it shall initially be pointed out that embodiments of the present invention are applied, in particular, in the field of centrifugal microfluidics, which is about processing liquids within the nanoliter to milliliter ranges. Accordingly, the fluidics structures may have suitable dimensions within the micrometer range for handling corresponding volumes of liquid. The fluidics structures (geometric structures) as well as the associated methods are suited for pumping liquid radially inward in centrifuge rotors. In this context, inward pumping is understood to mean transporting liquid from a radially outer position to a radially inner position, in each case in relation to a rotational center about which the fluidics structure may be rotated. Passive inward pumping is understood to mean inward pumping which is controlled exclusively by the rotational frequency of the rotor and the fluidic resistances of the feed and discharge conduits to and from a compression chamber.

(7) Whenever the expression radial is used, what is referred to is radial in terms of the rotational center about which the fluidics module and/or the rotor is rotatable. In the centrifugal field, thus, a radial direction away from the rotational center is radially falling, and a radial direction toward the rotational center is radially rising. A fluid channel whose beginning is closer to the rotational center than its end is therefore radially falling, whereas a fluid channel whose beginning is spaced further apart from the rotational center than its end is radially rising.

(8) Before addressing in more detail an embodiment of a fluidics module having corresponding fluidics structures with reference to FIGS. 1 and 2, a description shall initially be given of embodiments of an inventive device with reference to FIGS. 3 and 4.

(9) FIG. 3 shows a device having a fluidics module 10 in the form of a rotational body comprising a substrate 12 and a cover 14. The substrate 12 and the cover 14 may be circular in top view, having a central opening by means of which the rotational body 10 may be mounted to a rotating part 18 of a drive means via a common fastener 16. The rotating part 18 is rotatably mounted on a stationary part 22 of the drive means 20. The drive means may be a conventional centrifuge having an adjustable rotational speed, or a CD or DVD drive, for example. A control means 24 may be provided which is configured to control the drive means 20 so as to subject the rotational body 10 to rotations at different rotational frequencies. As is obvious to persons skilled in the art, the control means 24 may be implemented, for example, by a computing means programmed accordingly or by a user-specific integrated circuit. The control means 24 may further be configured to control the drive means 20 upon manual inputs on the part of a user so as to effect the rotations of the rotational body. In any case, the control means 24 is configured to control the drive means 20 so as to subject the rotational body to the rotational frequencies that may be used so as to implement the invention as is described here. A conventional centrifuge having only one rotational direction may be used as the drive means 20.

(10) The rotational body 10 comprises the fluidics structures that may be used. The fluidics structures may that may be used be formed by cavities and channels in the cover 14, the substrate 12 or in the substrate 12 and the cover 14. In embodiments, fluidics structures may be formed in the substrate 12, for example, whereas fill-in openings and venting openings are formed in the cover 14.

(11) In an alternative embodiment shown in FIG. 4, fluidics modules 32 are inserted into a rotor, and together with the rotor 30 they form the rotational body 10. The fluidics modules 32 may each comprise a substrate and a cover, wherein, again, corresponding fluidics structures may be formed. The rotational body 10 formed by the rotor 30 and the fluidics modules 32, again, may be subjected to a rotation by a drive means 20 controlled by the control means 24.

(12) In embodiments of the invention, the fluidics module and/or the rotational body comprising the fluidic structures may be formed from any suitable material, for example plastic, such as PMMA (polymethyl methacrylate, polycarbonate, PVC, polyvinyl chloride) or PDMS (polydimethylsiloxane), glass or the like. The rotational body 10 may also be considered to be a centrifugal-microfluidic platform.

(13) FIG. 1 shows a top view of a section of an inventive fluidics module 50 wherein the cover has been omitted, so that the fluidics structures can be seen. The fluidics module 50 shown in FIG. 1 may have the shape of a disc, so that the fluidics structures are rotatable about a rotational center 52. The disc may comprise a central hole 54 for attachment to a drive means, as was explained above with reference to FIGS. 3 and 4, for example.

(14) The fluidics structures are configured to pump fluid radially inward within the fluidics module 50. The fluidics structures comprise a first chamber 60, which represents an inlet chamber, a compression chamber 62, and a second chamber 64 separate from the first chamber 60, which represents a receiving chamber. A fluid outlet 66 of the inlet chamber 60, which in the embodiment represented is arranged at a radially outer end of the inlet chamber 60, is fluidically connected to a fluid inlet 70 of the compression chamber 62 via a first fluid channel 68. The fluid inlet 70 may be located at a radially outer area of the compression chamber 62. A fluid outlet 72 of the compression chamber 62 is fluidically connected to a fluid inlet 76 of the receiving chamber 64 via a second fluid channel 74. The fluid outlet 72 is arranged at a radially outer area of the compression chamber 62, said radially outer area being spaced apart from the fluid inlet 70 in the azimuthal direction. The second fluid channel 74 comprises a radially inwardly extending portion and thus represents a radial rise for a flow of liquid from the compression chamber 62 to the second chamber 64.

(15) As is schematically indicated in FIG. 1, the inlet chamber 60 may comprise a fill-in area 80 and a venting area 82. The receiving chamber 64 may comprise a venting area 84. The fill-in area 80 and the venting areas 82 and 84 may be fluidically connected to a corresponding fill-in opening (not shown) and venting openings (not shown).

(16) As may be seen in FIG. 1, the flow cross-section of the second fluid channel 74, which fluidically connects the fluid outlet 72 of the compression chamber 62 to the fluid inlet 76 of the receiving chamber 64, is larger than the flow cross-section of the fluid channel 68, which connects the fluid outlet 66 of the inlet chamber 60 to the fluid inlet 70 of the compression chamber 62. Thus, the second fluid channel 74 offers a lower flow resistance to a flow of liquid from the compression chamber 62 to the receiving chamber 64 than the first fluid channel 68 offers for a flow of liquid from the compression chamber 62 to the inlet channel 60.

(17) A pumping height, via which a liquid may be pumped from the compression chamber 62 into the receiving chamber 64, is designated by reference numeral 90 in FIG. 1.

(18) In the operation, which will be explained below with reference to FIG. 2, a phase 1 initially comprises introducing a volume of a liquid into the inlet chamber 60 (for example via the fill-in area 80). In this context, the inlet channel 68 will fill up in a capillary manner, or its fill-in operation is supported by rotation of the fluidics module at a low rotational frequency f.sub.low. Once the inlet chamber 60 has been filled, the rotational frequency is increased from the low frequency f.sub.low to a high frequency f.sub.high. Due to the centrifugal force F.sub.z acting as a result of this increase in the rotational frequency, the liquid is forced from the inlet chamber 60 through the inlet channel 68 into the compression chamber 62 and into the outlet channel 74. In this context, the frequency f.sub.high is sufficiently high so as to apply such a centrifugal force to the liquid that, as a result, a compressible medium located within the compression chamber 62, for example air, is compressed as is indicated in phase 2 of FIG. 2. Due to this compression, the pressure within the compression chamber 62 increases from a pressure p.sub.1, as is shown in phase 1 in FIG. 2, to a pressure p.sub.2, as is shown in phase 2 in FIG. 2. In the event of a steady rotational frequency, the filling levels of the liquid in the inlet channel 68, the outlet channel 74 and the compression chamber 62 adopt a state of equilibrium and/or a position of equilibrium, as may be seen from the filling levels in phase 2 in FIG. 2.

(19) Starting from this state, the rotational frequency is reduced so rapidly, in phase 3 shown in FIG. 2, that the pressure within the compression chamber 62 is decreased in that a large part of the sample liquid escapes via the path of the lowest resistance. This path of the lowest resistance is the outlet channel 74, which offers a lower flow resistance for the flow of liquid to the receiving chamber 64 than the inlet channel 68 offers for a flow of liquid to the inlet chamber 60. In accordance with the reduction in pressure p.sub.3 within the compression chamber 62, the air located within the compression chamber 62 will expand.

(20) In embodiments of the invention, the low rotational frequency f.sub.low may also become zero or adopt negative values, which indicates a reverse rotational direction.

(21) In embodiments of the invention, the fluidics module may be realized monolithically. Embodiments of the invention may be configured for pumping any sample liquids, such as water, blood or other suspensions. Embodiments of the invention allow that at a rotational frequency of about 6 Hz as a low rotational frequency and of about 75 Hz as a high rotational frequency, and at a rotational deceleration of about 32 Hz/s, 75% of a sample of water of 200 L may be conveyed radially inward within about 3 seconds over a pumping height of about 400 mm.

(22) In the embodiment described, only one inlet channel 68 and one outlet channel 74 are provided. In alternative embodiments, several inlet channels may be provided between the inlet chamber 60 and the compression chamber 62, and/or several outlet channels may be provided between the compression chamber 62 and the receiving chamber 64.

(23) As is shown in FIG. 1, the fluid outlet 66 is located further inward radially, in relation to the rotational center 52, than the fluid inlet 70 of the compression chamber 62, so that the inlet channel 68 is radially declining. The fluid outlet 72 of the compression chamber 62 is located further outward radially than the fluid inlet 76 of the receiving chamber 64, so that the fluid channel 74 is radially rising.

(24) In the embodiment shown in FIG. 1, the entire receiving chamber 64 is located further inward radially than the inlet channel 60. Thus, embodiments of the invention enable a net pumping action directed radially inward.

(25) In alternative embodiments, the fluid channel 74 may also comprise radially declining portions. For example, the fluid channel 74 may comprise a syphon via which the compression chamber 62 is fluidically connected to the receiving chamber 64. The outlet of said syphon may be located further outward radially than the fluid outlet of the compression chamber 62, it being possible for the compression chamber to be via a sucking action within the syphon following filling (priming) of the syphon, which is effected by the reduction of the rotational frequency.

(26) FIG. 5 shows alternative fluidics structures of an embodiment of a fluidics module. A compression chamber 162 comprises only one fluid opening 163 at a radially outer area, which may be referred to as a fluid inlet/outlet. A first fluid channel 168 is provided between the fluid outlet 66 of a first chamber (reservoir) 160 and the compression chamber 162, and a second fluid channel 174 is provided between the compression chamber 162 and the fluid inlet 76 of a second chamber (collecting chamber) 164, which is separate from the first chamber 160. The chambers 160 and 164, in turn, may be provided with a corresponding fill-in area 80 and venting areas 82 and 84. As is shown in FIG. 5, the first fluid channel 168 and the second fluid channel 174 lead into a channel section 165 fluidically connected to the fluid opening 163. By means of the fluidics structure shown in FIG. 5, inward pumping may be implemented in a manner analogous to that described above with reference to FIGS. 1 and 2 in that the fluidics module is subjected to corresponding rotations. Thus, the explanations shall apply accordingly to the embodiment shown in FIG. 5.

(27) In embodiments of the present invention, liquid is thus pumped radially inward within a rotor. In this context, initially, liquid is pumped radially outward at a high rotational frequency through one or more narrow inlet channels (which exhibit high hydrodynamic resistance) into a chamber wherein a compressible medium is trapped and compressed. At the same time, one or more further outlet channels (which exhibit a low hydrodynamic resistance), which are connected to the compression chamber and to a receiving chamber located radially inward, are filling up. Due to a rapid deceleration of the rotor to a low rotational frequency, the compressive medium will expand again. A large part of the liquid is pumped through the outlet channel(s) into the receiving chamber, whereas only a smaller part of the liquid is pumped back into the inlet channel(s).

(28) In embodiments of the invention, the pumping operation may be supported by additional expansion of the compressible medium within the compression chamber. Such additional expansion may be thermally induced in that corresponding heating is provided. Alternatively, such additional expansion may be caused by gas evolution due to chemical reactions. Again, as an alternative, such an expansion may be supported by additional external pressure generation by means of a corresponding pressure source.

(29) As was explained above, the different flow resistances may be achieved in that the inlet channel comprises a smaller flow cross-section than the outlet channel, so that the narrow inlet channel represents a high resistance for the liquid to be processed, whereas the wide outlet channel represents a very low resistance. In alternative embodiments, the flow resistance might be achieved by adjusting the lengths of the inlet channel and of the outlet channel accordingly since the flow resistance also depends on the length of a fluid channel in addition to the flow cross-section, as is known.

(30) Embodiments of the present invention thus enable passive inward pumping in centrifuge rotors. Unlike conventional methods, the present invention represents a passive method requiring no additional media (liquid, wax, etc.) in the rotor and no additional external elements such as pressure sources or heat sources, for example, and thus involves lower expenditure and lower cost. In embodiments of the present invention, such external elements may be provided to be merely supportive. In addition, embodiments of the present invention enable clearly faster pumping than previous methods, merely several seconds being taken for a few 100 L, as opposed to several minutes in accordance with known methods. Moreover, the present invention is advantageous in that the pumping method may be repeated any number of times by means of the fluidic structure described.

(31) It is obvious to persons skilled in the art that the fluidics structures described represent only specific embodiments and that alternative embodiments may deviate in terms of size and shape. Any persons skilled in the art may readily appreciate any fluidics structures and rotational frequencies which deviate from the fluidics structures and rotational frequencies described while being suitable for inward pumping of a desired volume of liquid in accordance with the inventive approach. In addition, it is obvious to any person skilled in the art in what manner the volume of the compression chamber and the flow resistances of the fluid channels may be implemented in order to achieve the inventive effect.

(32) While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations and equivalents as fall within the true spirit and scope of the present invention.