Micro flow filtration system and integrated microfluidic element

Abstract

A micro fluid filtration system (100) preferably for increasing the concentration of components contained in a fluid sample has a fluid circuitry (1). The fluid circuitry (1) comprises the following elements: A tangential flow filtration element (7) capable for separating the fluid sample into a retentate stream and a permeate stream upon passage of the fluid, an element for pumping (3) for creating and driving a fluid flow through the fluid circuitry (1) and at least one element for obtaining information about the properties of the fluid sample within the circuitry. The circuitry further comprises a plurality of conduits (24) connecting the elements of the fluid circuitry (1) through which a fluid stream of the fluid sample is conducted. The circuitry (1) has a minimal working volume of at most 5 ml, which is the minimal fluid volume retained in the elements and the conduits (24) of the circuitry (1) such that the fluid can be recirculated in the circuitry (1) without pumping air through the circuitry (1). An integrated microfluidic element (20) of the circuitry (1) contains the functionality of at least two elements of the group of elements of the circuitry (1).

Claims

1. A microfluidic flow filtration system having a recirculation loop fluid circuitry, the recirculation loop fluid circuitry comprising the following elements and connecting the following elements to each other: a tangential flow filtration element having a feed inlet, a retentate outlet, a permeate outlet and a membrane that separates a fluid sample into a retentate stream and a permeate stream upon passage of the fluid sample into the tangential flow filtration element through the feed inlet, a pumping element that creates and drives a fluid flow of the fluid sample through the fluid circuitry and the tangential flow filtration element, wherein the retentate outlet is connected to an inlet of the pumping element, at least two obtaining elements that obtain information about the properties of the fluid sample within the fluid circuitry, wherein an inlet of the obtaining element is connected to an outlet of the pumping element and an outlet of the obtaining element is connected to the feed inlet of the tangential flow filtration element; and a plurality of conduits connecting the elements of the microfluidic flow filtration system; wherein a minimal working volume of the fluid circuitry is defined by a minimal fluid volume retained in the pumping element, the at least two obtaining elements and the plurality of conduits, such that the fluid can be recirculated in the fluid circuitry without pumping air through the fluid circuitry is at most 5 ml, the at least two obtaining elements are implemented into one integrated microfluidic element, the one integrated microfluidic element has a volume which is at most one fourth of the minimal working volume of the fluid circuitry, one obtaining element of the at least two obtaining elements is an optical measuring element that determines a concentration of components contained in the fluid sample, wherein said optical measuring element includes a cuvette having a height smaller than a height of connecting conduits and a width wider than a width of connecting conduits, and one obtaining element of the at least two obtaining elements is a physical measuring element that determines a viscosity of the fluid sample, wherein said physical measuring element includes two pressure sensors arranged upstream and downstream of the cuvette for measuring a pressure difference.

2. The microfluidic flow filtration system according to claim 1, wherein the integrated microfluidic element has a housing and the tangential flow filtration element has a TFF-housing which is part of the housing of the microfluidic element.

3. The microfluidic flow filtration system according to claim 2, wherein the membrane of the tangential flow filtration element is disposable.

4. The microfluidic flow filtration system according to claim 1, wherein the circuitry further comprises a reservoir suitable for containing the fluid sample, the reservoir being integrated in the fluid circuitry and having at least a reservoir inlet and a reservoir outlet both in connection to the circuitry.

5. The microfluidic flow filtration system according to claim 3, wherein a volume of the reservoir is at most 10 ml.

6. The microfluidic flow filtration system according to claim 3, wherein the volume of the reservoir is at most 1 ml.

7. The microfluidic flow filtration system according to claim 3, wherein the volume of the reservoir is at most 0.7 ml.

8. The microfluidic flow filtration system according to claim 3, wherein the volume of the reservoir is at most 0.5 ml.

9. The microfluidic flow filtration system according to claim 1, wherein the circuitry further comprises at least one valve element; and/or a hollow fiber element; and/or a regulator element that regulates the flow of the fluid through the fluid circuitry, and/or a pressure regulation element that regulates the pressure of the fluid in the fluid circuitry, and/or a determining element that determines pressure data which is one or more pressure sensors; and/or an optical detection element.

10. The microfluidic flow filtration system according to claim 1, wherein the minimal working volume of the fluid circuitry is at most 1 ml.

11. The microfluidic flow filtration system according to claim 1, wherein the minimal working volume of the fluid circuitry is at most 500 μl.

12. The microfluidic flow filtration system according to claim 1, wherein the minimal working volume of the fluid circuitry is at most 200 μl.

13. The microfluidic flow filtration system according to claim 1, wherein the minimal working volume of the fluid circuitry is at most 100 μl.

14. The microfluidic flow filtration system according to claim 1, wherein the conduits have an internal diameter of at most 1.5 mm.

15. The microfluidic flow filtration system according to claim 1, wherein the conduits have an internal diameter of at most 1 mm.

16. The microfluidic flow filtration system according to claim 1, wherein the conduits have an internal diameter of at most 0.7 mm.

17. The microfluidic flow filtration system according to claim 1, wherein the conduits have an internal diameter of at most 0.1 mm.

18. The microfluidic flow filtration system according to claim 1, wherein a conduit is a channel, a passage in an element of the circuitry, a pipe, or a tubing.

19. An integrated microfluidic element for a microfluidic flow filtration system with a fluid circuitry having a minimal working volume of at most 5 ml, wherein the integrated microfluidic element has a volume which is at most one fourth of the minimal working volume of a fluid circuitry of the micro flow filtration system, and provides the functionality of at least two obtaining elements for obtaining information about the properties of a fluid sample within the circuitry, wherein one obtaining element of the at least two obtaining elements is an optical measuring element that determines a concentration of components contained in the fluid sample, wherein said optical measuring element includes a cuvette having a height smaller than a height of connecting conduits and a width wider that a width of connecting conduits, and one obtaining element of the at least two obtaining elements is a physical measuring element that determines a viscosity of the fluid sample, wherein said physical measuring element includes two pressure sensors arranged upstream and downstream of the cuvette for measuring a pressure difference.

20. The integrated microfluidic element according to claim 19, comprising the functionality of a tangential flow filtration element having a feed inlet, a retentate outlet, a permeate outlet and a membrane that separates a fluid sample into a retentate stream and a permeate stream upon passage of the fluid sample into the tangential flow filtration element through the feed inlet.

21. The integrated microfluidic element according to claim 19, comprising a capillary or capillary channel.

Description

(1) The invention is illustrated in more detail hereafter based on particular embodiments shown in the figures. The technical features shown therein can be used individually or in combination to create preferred embodiments of the invention. The described embodiments do not represent any limitation of the invention defined in its generality.

(2) FIG. 1 shows a schematic view of a filtration system;

(3) FIG. 2 shows a flow filtration circuitry according to the invention with an integrated microfluidic element;

(4) FIG. 3 shows another schematic view of a fluidic circuitry for the determination of viscosity according to the invention;

(5) FIG. 4 shows an integrated microfluidic element comprising the functionality of two pressure sensors and a measuring element for detecting the concentration and viscosity;

(6) FIG. 5a, b shows two embodiments of another microfluidic element comprising the functionality of measuring the pressure in the circuitry and filtering the fluid sample.

(7) FIG. 1 shows a state-of-the-art microfluidic flow filtration system 100 having a circuitry 1. The circuitry 1 comprises a reservoir element which is a reservoir 2, a container or a tank containing the fluid sample, an element for pumping which is a pump 3, three pressure sensors 4, 5, 39, a cuvette 6, a tangential flow filtration element 7, a pressure regulator 8 and a valve 9 which is a T-shaped conjunction to withdraw fluid from the circuitry 1. Each functionality of the circuitry 1 is implemented by one single element like the reservoir 2, the pressure sensors 4, 5 or 39 or the cuvette 6. Because each of the elements and also the conduits connecting these elements have a contribution to the minimal working volume of the circuitry, the minimal working volume is relatively large. In the state of the art the minimal working volume of the fluid circuitry 1 is at least approximately 20 ml. Normally the minimal working volume is in the range of some 100 ml.

(8) FIG. 2 shows a micro fluid filtration system 100 according to the invention with a circuitry 1 for and by a plurality of conduits 24. The fluid circuitry 1 shown in FIG. 2 also comprises a reservoir 2, a pump 3 which is implemented by a 4-port-valve (valving apparatus) 10 and two syringes 11 that serve as a piston pump.

(9) The micro tangential flow filtration element 7 comprises a feed inlet 12, a retentate outlet 13, a permeate outlet 14 and a semipermeable membrane 15. The membrane 15 is capable of separating the fluid sample into a retentate stream and a permeate stream upon passage of the fluid sample into the tangential flow filtration element 7 through the feed inlet 12. The permeate stream withdrawn from the circuitry 1 via the permeate outlet 14 is collected in a permeate chamber 16. The permeate chamber can be located on a balance 17 to weight the amount of the permeate stream and to control the flow through the membrane 15 and to measure the amount of withdrawn fluid. The retentate stream flows through conduit 24, through the reservoir 2, the valving apparatus 10, the integrated microfluidic element 20 into the TFF-element 7. This circuitry is called retentate circuitry in which the microfluidic element 20 is located.

(10) The circuitry 1 according to the invention also comprises a valve 9 with a T-shaped conjunction and an outlet port 18. The outlet port 18 is used to withdraw fluid from the circuitry 1, particularly to withdraw the concentrated fluid at the end of the concentration process. The fluid is conducted to a collection reservoir 29.

(11) The pressure regulator 8 is a regulator element for regulating the pressure (and thereby the fluid flow) in the fluid circuitry 1. The pressure regulator 8 is controlled by a control unit 19 which is fed by the pressure values measured within the circuitry 1. These pressure values are detected by pressure sensor 39 and at least one pressure sensor which is integrated within the integrated microfluidic element 20.

(12) The integrated microfluidic element 20 defines a so-called volume element which is a separate and discrete element. The microfluidic element 20 has a volume in which fluid of the fluid circuitry is contained during its flow through the microfluidic element 20. The volume of element 20 is at most 25% of the working volume of the complete fluid circuitry 1. It could be shown that the microfluidic element 20 is one of the major elements of the fluid circuitry. Therefore, reducing its volume has a direct and positive influence to the complete fluid circuitry and its minimal working volume. So, preferably the working volume of the microfluidic element 20 is at most 20% of the minimal working volume, further preferably at most 15%. It can also be shown that the positive influence is increased if the volume of the microfluidic element 20 is at most 10% of the minimal working volume. During investigations within the frame of the invention positive effects of the volume of the volume element 20 have been determined if the volume of the microfluidic element 20 is at most 400 μl, preferably at most 50 μl. Nevertheless this allows processing of small fluid samples and in case of a concentration mode achieving high concentration rates.

(13) The circuitry 1 comprises the integrated microfluidic element 20 instead of the separated elements of the pressure sensors and the cuvette (which has here the functionality of a capillary with a different diameter compared to the diameter of the conduits before and after the integrated pressure sensors, respectively) which are signed by the reference numbers 4, 5 and 6 respectively in FIG. 1. In the embodiment shown in FIG. 2 the integrated microfluidic element 20 is a viscosity module 21 capable to measure the viscosity of the fluid sample contained in the circuitry 1. The dimensions of the viscosity module 21 are significantly reduced with respect to the overall dimensions of the separated elements of two pressure sensors and a cuvette. An important role plays the fact that the conduits 24 between the elements can be shortened with so that the minimal working volume of the circuitry 1 can be reduced in total.

(14) FIG. 3 shows a schematic principal view of a reduced circuitry 1 which comprises a reservoir 2, a pump 3, a pressure regulator 8 in form of a hose clamp 22 and a viscosity module 21 which is an integrated microfluidic element 20 or an microfluidic module. The microfluidic element 20 comprises the functionality of two pressure sensors and a cuvette. The viscosity module 21 further allows to determine the concentration and aggregation of compounds contained in the fluid sample by an optical measurement using the integrated transparent capillary 28 providing a cuvette function and to determine the viscosity by measuring a pressure gradient or difference using two pressure sensing elements, for example in form of pressure sensing modules 26, 27.

(15) The viscosity module 21 shown in FIG. 3 has two tube fittings 23 for connecting to the conduits 24 which are tubes 25 in this example. Between the two pressure sensing modules 26, 27 the capillary 28 is arranged which is directly connected to the pressure sensing modules 26, 27.

(16) The volume or minimal working volume of the viscosity module 21 is formed by the effective volume of (or in) the pressure sensing modules 26, 27 and by the effective volume of the capillary 28. To vary the volume of the viscosity module 21 (being the integrated microfluidic element 20) the volume of the capillary 28 or the volume of the fluidic connection to the pressure sensing modules 26 can be changed.

(17) To reduce the minimal working volume of the viscosity module 21 and so also the minimal working volume of the circuitry 1 and to enable viscosity determination, the internal diameter of the capillary 28 is preferably in a range between 100 μm and 500 μm. Particularly preferred is an internal diameter of the capillary 28 between 100 ™ and 250 μm. The internal diameter is understood as the diameter of the capillary 28 if the capillary has a circular cross section. If the capillary is not round, the internal diameter is to be understood as the dimension which is parallel to the optical measurement direction (arrow 34). So, a radiation or light beam which is transmitted by a source 31 passes through the capillary 28 along the internal diameter and is received by an optical detector 32. The width of the capillary which is perpendicular to the optical measurement distance 34 is not relevant for the optical measurement (as long as it is not too small to allow the light beam to pass through the cuvette).

(18) According to the invention the capillary 28 is preferably implemented in such a manner that the fluidic resistance of the capillary 28 and the fluidic length are adjusted in a way that establishes a pressure gradient along the capillary 28 which is substantially high. A pressure gradient or pressure difference is understood as substantially high if the pressure gradient along the capillary is at least in the range of approximately 0.05 bar per mPa sec (milli Pascal second).

(19) FIG. 4 shows a detailed view of an integrated microfluidic element 20 according to the invention. The microfluidic element 20 is a viscosity module 21 which comprises the functions of two pressure sensing modules 26, 27 and the function of a cuvette 6 which is integrated as a capillary 28.

(20) The upper picture in FIG. 4 shows a top view of the viscosity module 21. It is clearly shown that the width w of the transparent capillary 28 is wider than the width of the connecting conduits 24. This arrangement is used to calculate the viscosity on basis of measuring a pressure difference with the two pressure sensing modules 26, 27.

(21) The lower picture of FIG. 4 shows a side view of the viscosity module 21. It is clearly shown that the height h of the cuvette element 6 (capillary 28) is smaller than the height of the connecting conduits 24 (which are preferably pipes) and the fittings 23 respectively. An optical measuring unit 30 comprises a light emitting source 31 arranged above the capillary 28. The light emitting source 31 can be every source emitting an electromagnetic radiation which can be for example visible light or invisible light like ultraviolet light. A respective optical detector 32 is arranged below the capillary 28, preferably below the viscosity module 21, so that a radiation transmitted from the optical source 31 along the optical measurement direction 34 passes through the transparent capillary 28 of the viscosity module 21 and reaches the detector 32. This allows an online, real-time monitoring of the concentration of components or aggregates contained in the solution which flows in an unidirectional manner through the circuitry 1 and the viscosity module 21.

(22) The FIGS. 5a, b show two other embodiments of an integrated microfluidic element 40 which provides and contains the functionality of the tangential flow filtration element 7 and of the two pressure sensors 5 and 39 shown in FIG. 1 or FIG. 2, respectively.

(23) The upper picture of FIG. 5a shows a schematic cross-sectional side view of the first embodiment of the integrated microfluidic element 40 which includes the functions of the flow filtration element 7 and of two pressure sensors 5, 39 according to FIG. 2. The integrated microfluidic element 40 comprises a housing 50 in which a capillary channel 44 is formed. The capillary channel also comprises the feed inlet 12, the retentate outlet 13 and the permeate outlet 14. The housing 50 of the microfluidic element 40 forms a TFF-housing 51 of the tangential flow filtration element 7. In a preferred embodiment the TFF-housing 51 can be part of the housing 50 of the microfluidic element 40. The integrated microfluidic element 40 comprises two pressure sensing modules 26, 27 each located at an end of the filtration element 41. The filtration element 41 comprises the feed inlet 12 followed by a filtration chamber 42 containing the membrane 15 which is located above a support structure 43. The membrane 15 is sealed by a sealing 45 so that fluid flowing through the permeate outlet 14 have to pass the membrane 15. Preferably the membrane 15 of the tangential flow filtration element 7 is disposable. So, in case of clogging or after a predetermined process time the efficiency of the membrane may be reduced. Then, only the membrane has to be exchanged. The TFF-element 7 and the microfluidic element 40 remain unchanged. Especially the connections to connecting conduits do not have to be exchanged or renewed. Additionally, replacing the membrane 15 only does not influence the pressure sensing modules 26, 27. Only the sealing 45 sealing the membrane 15 to the housing 50 will also be renewed.

(24) The permeate outlet 14 of the filtration chamber 42 is located at the end of the chamber 42 which is essentially perpendicular to the flow direction. At the end of the chamber 42 also the retentate outlet 13 is positioned so that a part of a fluid flow through the filtration element 41 leaves the chamber at this end. In flow direction before and behind the filtration chamber 42 a channel 44 is implemented in the microfluidic element 40. In this channel 44 the two pressure sensing modules 26 and 27 respectively are arranged. So, the pressure difference between the two pressure sensing modules 26, 27 can be used to calculate the transmembrane pressure in the microfluidic element 40. The filtration chamber 42 can further be complemented with a turbulence promotor.

(25) The lower picture in FIG. 5a shows a cross-sectional top view along the line A-A of the upper picture. It is clearly seen that the capillary channels 44 at the two ends of the microfluidic element are relatively small. In the area of the pressure sensing modules 26, 27 the capillary is widened. The filtration chamber 42 is further widened in respect to the capillary channel 44 and the sensing modules 26, 27. Between the sensing modules 26, 27 and the filtration chamber 42 the capillary channels have their (normal) width.

(26) FIG. 5b shows another embodiment of an integrated microfluidic element 40 comprising a filtration element 41 and two pressure sensing modules 26, 27. The upper picture shows a cross sectional side view of the integrated microfluidic element 40; the lower picture shows a cross-sectional top view along the line A-A. The difference between the two embodiments in the FIGS. 5a and 5b is that in the embodiment shown in FIG. 5b the feed inlet 12 and the retentate outlet 13 are located at the upper side of the microfluidic element 40. So, the flow is deflected two times during passage of the microfluidic element 40. The pressure sensing modules 26 and 27 are located at the feed inlet 12 and at the retentate outlet 13, respectively, so that the pressure of the fluid is measured before and after the fluid passes the filtration chamber 42.

(27) The construction of the filtration element 41 of FIG. 5b itself is similar to the construction of the filtration element 41 according to FIG. 5a with respect to the arrangement of the membrane 15 and the permeate outlet 14. The cross sectional top view clearly shows that the capillary channel 44 is also widened in the area of the pressure sensing module 26, 27.

(28) The two embodiments of the microfluidic element 40 shown in the FIGS. 5a and 5b have the advantage that the construction of the element is cheap and easy to perform. Due to the fact that only small pieces have to be arranged together, the pieces can be manufactured with a high accuracy so that very small volumes of the filtration chamber 42 can be achieved. Further, due to the not needed fittings and conduits between the filtration element 41 and the pressure sensing modules 26, 27 the minimal working volume can be reduced further.

(29) So, using these alternative embodiments of an integrated microfluidic element or module 40, which contains at least two functionalities of the elements comprised in a fluidic circuitry, especially for concentration or purification of components contained within the fluid sample within this circuitry, allows to reduce the minimal working volume of the circuitry 1. Merging the functionality of at least two circuitry elements results in a compact component or module with a small and reduced minimal working volume that is optimized for concentrating small amounts of fluid, preferably of less than 20 ml.