Abstract:
A microfluidic device for transporting a fluid, in particular a micropump or microvalve. The device has films, which lie against each other at film surfaces facing each other and are connected to each other in such a way that a transport channel to be formed between the films is defined, Deflecting apparatuses for forming the transport channel by jointly deflecting the films lie against each other in a direction perpendicular to the film surfaces. A deflecting surface region of the rear film in the deflection direction lies within the deflecting surface region of the front film in the deflection direction defined by the connection between the films.

Description:
The present application is a 371 of International application PCT/DE2011/050017, filed May 31, 2011, which claims priority of DE 10 2010 022 550.9, filed Jun. 2, 2010 and DE 10 2011 015 184.2, filed Mar. 26, 2011, the priority of these applications is hereby claimed and these applications are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a device for transporting small volumes of a fluid, particularly a micropump or a microvalve. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention relates to the field of microfluidics, which is increasingly gaining significance in medicine and other biological sciences. Miniaturized devices for the analysis and/or material synthesis accommodated on a chip are increasingly used in diagnostics as well as in therapy. In particular, micropumps play an increasing role in medicament dosing. 
     The transport device mentioned above can be considered to be used as a separate device or as a component of a microfluidic analysis or/and synthesis device comprising additional components, particularly a so-called flow cell. 
     When manufacturing microfluidic flow cells, the methods as well as materials of semiconductor technology are used, i.e. materials such as glass, quartz or silicon. In the desire to lower the costs for the manufacturing of microfluidic products, synthetic materials are used more frequently as less expensive materials. With respect to achieving a mass production which is economical but still meets high precision requirements, this gives rise to a multitude of specific problems, which in many cases prevent further reduction of the costs and the manufacture of synthetic microfluidic chips as disposable products. 
     U.S. Pat. No. 7,832,429 B2 discloses a transporting device in the form of a micropump which includes a stiff plastic substrate and a film which rests against the substrate and is of the same synthetic material. The film which is partially connected to the substrate and partially rests against the substrate may be lifted from the substrate by negative pressure while forming a cavity, or a plurality of cavities which are connected to each other by means of permanent connecting ducts. A pumping effect can be achieved by sequentially forming the cavities. 
     Such transporting devices are preferably used in disposable microfluidic flow cells for analysis and synthesis, and for transporting small fluid quantities in the range of 0.001 ml to 10 ml in medical diagnostics, medicament dosing, cell cultivation, bioreactors, and agent development and micro-reaction technology. 
     The present invention is based on the object of creating a novel transporting device of the above described type which makes possible, while further improving the properties of the device, an economical mass production and, beyond that, simple, preferably mechanical and leakage-free points of intersection with an operating device. 
     The device according to the invention, which meets this object, is characterized by films which rest against each other with oppositely located film surfaces and are connected to each other by limiting a transport duct formed between the films, as well as by means of common deflection of the films which rest against each other in a direction perpendicular to the film surfaces, wherein a deflectable surface area of the rear film in the direction of deflection is located within the deflectable surface area of the front film in the direction of deflection, defined by the connection between the films. 
     In accordance with the invention, the transporting duct between the films which are connected to each other is formed only by actuating, i.e. deflecting the two films. Advantageously, this type of duct formation does not require a soft elastic film material which contains, for example, softeners and other substances, such as oils, and which would not be compatible with a large number of substances to be transported by the transporting duct. Possible materials for both films are PMMA, PS, COP, COC, PP, PC, PE, or PEEK. When the actuation is canceled, the transporting duct is formed back, for example, automatically. However, this forming back can also take place by a second actuation which counteracts the formation of the transporting duct. 
     While it would be conceivable to enclose the films for their connection in an operating device comprising clamping jaws and suction devices, the films are preferably connected inseparably to each other by mutual adherence of the film surfaces which rest against each other, particularly by welding. The tightness of the transporting duct can thus be ensured even at a high pressure of the fluid to be transported. 
     While the inseparably connected films could also be clamped in an operating device, wherein one of the clamping jaws would have to provide a suction function, in a preferred embodiment of the invention at least the rear film in the direction of the deflection is inseparably connected to a rigid substrate. This rigid substrate may preferably include, as is conventional in microfluidic flow cells, ducts, reservoirs, filters, or mixing and reaction chambers, or detection chambers, as well as fluidic inlets and, if applicable, outlets for introducing and/or removing samples which are connected to each other in series and/or parallel individually or jointly by the transporting device according to the invention. 
     Moreover, the front film in the direction of the deflection could be held by a clamping device. However, preferably the front film in the direction of deflection is inseparably connected, possibly through the rear film, to the substrate. 
     In accordance with an especially preferred further development of the invention, the deflectable surface area of the rear film in the direction of deflection is defined by the area of connection of this film with the substrate, particularly a welding seam connecting the film to the substrate. The deflectable surface area of the rear film rests in a loose but planar manner within the preferably enclosed circumferential welding seam against the substrate. 
     While it would be conceivable to use a clamping device for forming the limitation of the deflection surface area in the particularly preferred embodiment of the invention, also when connecting the front film to the rear film, the deflectable surface area of the front film in the direction of deflection is limited by a connecting area with the rear film, particularly a welding seam connecting the front film to the rear film. The preferably circumferentially enclosed welding seam of the rear film thus also includes the welding seam of the front film. 
     In accordance with another advantageous further development of the invention, the latter welding seam connecting the two films is a double welding seam for connecting the rear film to the substrate, preferably by laser welding. 
     Preferably, the two films consist of the same synthetic material, wherein this material additionally also may be the same as the material of the substrate. Advantageously, in this manner, a fluid to be transported comes into contact with only one and the same material. 
     Advantageously, the deflection device is provided for applying a pneumatic, hydraulic or/and mechanical pressure against the deflectable surface area of the rear film in the direction of deflection. 
     Correspondingly, a pressure duct for a pressurized gas or a pressurized liquid can open into the surface area of the substrate which is located opposite the deflectable surface area of the rear film. Alternatively, a throughopening for the passage of an actor ends at this location. 
     In accordance with another preferred embodiment of the invention, at least one duct opens into the surface area of the substrate which is located opposite the difference range of the deflectable surface areas of the front and rear films. 
     As a rule, the adhesive connection area between the films defining the transporting duct will be closed circumferentially between the films. Alternatively, it may include an opening, for example, for the entry of a liquid which will then enter the transporting duct as a result of capillary force. 
     In the latter case, the interior of the transporting duct is advantageously conditioned hydrophilically. 
     In accordance with another advantageous further development of the invention, devices for determining the degree of deflection of the front film or the interior volume of the transporting duct may be provided. The internal volume may vary, for example, if the pressure of a fluid to be transported varies. By measuring the respective size of the formed internal volume, the flow quantity can be kept constant by an appropriate control of the pump actuator movement. Any variations of the internal volume of the transporting duct which may occur as a result of pressure variations of the fluid to be transported, can advantageously be minimized by mounting an additional film for creating a pressure-controlled external space for the transporting area to which pressure can be applied separately and in a controlled manner. 
     An actuation device acting on the transporting duct is preferably provided for producing a closing front advancing in the transporting direction. The closing front pushes, in a peristaltic pumping movement, fluid which has entered the transporting duct and transports the fluid in the desired manner with the speed of the advancing closing front out of the transporting duct. The actuating device closes the transporting duct, if applicable, against the force applied for deflecting the films. Closing of the transporting duct is effected by placing the films flat against each other. 
     The transporting duct may have, on the entry side, several entry ducts for fluids to be mixed which are connected to several ducts or reservoirs for the various fluids. The actuator movement results, in addition to transporting the fluids, to simultaneously mixing of the fluids. 
     The invention will be described in the following with the aid of embodiments and the enclosed drawings referring thereto. In the drawing: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  shows a micropump according to the invention in a perspective view, 
         FIG. 2  shows the micropump of  FIG. 1  in an exploded view, 
         FIG. 3  is a longitudinal sectional view of the micropump of  FIG. 1 , 
         FIG. 4  shows various possibilities for forming a transport duct according to the invention, 
         FIG. 5  shows various possibilities for deflecting films in accordance with the invention, 
         FIG. 6  shows another embodiment of a pump for a structural pump group according to the invention, 
         FIG. 7  shows an embodiment of a structural valve group according to the invention, 
         FIG. 8  shows a multiple chamber pump according to the invention, 
         FIG. 9  shows various possibilities for determining the internal volume of a transporting duct constructed according to the invention, 
         FIG. 10  shows a structural pump group based on capillary action according to the invention, and 
         FIG. 11  shows a structural valve group according to the invention based on capillary action. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A structural micropump group illustrated in  FIGS. 1 to 4  comprises a substrate  1  in the form of a flat plate, a film  2  connected to the plate side of the substrate  1 , and another film  3  connected to the substrate  1  through the film  2 . On its side facing away from the films  2  and  3 , the substrate  1  is connected to a third film  4 . 
     In the illustrated embodiment, all of the mentioned components are of the same synthetic material. To be considered in this connection are, for example, PMMA, PC, PS, PP, PE, COC, COP, PET or PEEK. 
     The thickness of the substrate  1  may be, for example, between 0.5 mm and 5 mm, in particular between 0.5 mm and 2 mm. The thickness of the film  2  is preferably in the range of 0.001 mm to 0.5 mm, particularly 0.01 mm to 0.1 mm and the thickness of the film  3  is, for example, 0.01 mm to 1 mm, preferably 0.05 mm to 0.3 mm. 
     While the films  2  and  3  extend in the illustrated embodiment beyond the entire plate surface of the substrate  1 , the film  4  only covers a partial area of the respective plate surface and closes, in particular, a recess  5  formed in the substrate  1  and partially up to the ducts  6  and  7  or  8  and  9  leading to the connections  10  and  11 . 
     As can be seen particularly in  FIG. 2 , the film  2  has an oblong surface area  12  which is defined by a welding seam  13  connecting the film  2  to the substrate  1 , preferably by means of a welding seam  13  produced by a laser. Preferably, for carrying out the laser welding, the film  2  is constructed so as to be transparent at least in the area of the welding seam  13  for the selected laser wave length, and the area of the substrate  1  located underneath the welding seam  13  is constructed so as to be absorbent, for example, by adding additional absorbing materials, such as carbon or soot, to the synthetic material. Within the surface area  12  and outside of the welding seam, the film  2  rests loosely against the substrate  1 . 
     The film  3  has a surface area  14  which is similar to the surface area  12  but has a larger size which includes the surface area  12 , and a welding seam  15  which, as in the case of the welding seam  13 , is preferably formed by laser welding. The welding seam  15  connects as a double seam the film  3  to the film  2  as well as the film  2  to the substrate  1 . 
     Reference numeral  16  refers to a mechanical actor which is a component of an operating device for the structural micropump group comprising the substrate  1  and the films  2  to  4  and which is capable of deflecting the film  4  into the recess  5  in the substrate  1 . 
     On the side of the structural micropump group facing away from the actor  16 , an actor device  17  is arranged which extends over the length of the entire surface area  14  and comprises actors  18  which are movable individually perpendicular to the plane of the plate of the substrate  1 . 
     The manner of operation of the above described structural micropump group will be described in the following with the aid of  FIG. 3  whose  FIG. 3   a  shows a longitudinal sectional view along the middle of the surface area  12 ,  14  and whose  FIG. 3   b  shows a cross sectional view through these surface areas. 
     An elongation of the film  4  by the actor  16  into the recess  5  leads to a displacement of the fluid contained in the recess  5 , for example, air, into the ducts  6  and  7  which open into the substrate  1  opposite the surface area  12  of the film  2 , resting against the substrate  1 . The fluid emerging from the openings, which may possibly be compressed, expands the film  2  which, up to then, has been resting flat against the substrate  1  in the manner illustrated in  FIG. 3  with the formation of a deflection duct  20 . This elongation inevitably also causes an elongation of the film  3 , which up to then has been resting flat against the film  2 . Because of the greater elongation of the surface  14  of the film  3  as compared to the surface area  12  of the film  2 , during this elongation a transporting duct  19  is formed between the films  2 ,  3  into which the ducts  8  and  9  open at the ends thereof. 
     If, for example, the connection  10  forms an inlet for the fluid to be transported by the structural pump group, the waiting fluid is suctioned through the duct  8  into the transporting duct  19  as a result of the creation of the transporting duct  19 . 
     A progressing closing front, caused by the successive actuation of the actors  18  of the actuating device  17 , pushes the fluid which has been suctioned into the transporting duct  19  through the duct  9  to the connection  11  serving as an outlet. While fluid is being pushed out, new fluid to be transported can be suctioned already behind the closing front, so that in a peristaltic pump movement fluid can be continuously transported. Typical flow rates are between 0.1 μl/min and 10,000 μl/min. 
     It is understood that the above described structural pump group may also be capable of transporting from the connection  11  to the connection  10  in the reverse direction. 
     The structural pump group could be a component of a larger flow cell which carries out a large number of additional functions. The inlet and the outlet could coincide and a fluid transport could take place in a circular motion. Reservoirs could be provided instead of the connections  10  and  11 . 
       FIG. 4  shows another possibility for forming a transporting duct  19  between the films  2  and  3  by means of a deflection duct to which a pressurized fluid is admitted. 
     In accordance with  FIG. 4   a , an arrangement with two deflection ducts  20 ′ and  20 ″ is provided. Welding seams are omitted in  FIG. 4   a.    
       FIG. 4   b  shows an embodiment with a symmetrical deflection duct  20  in which only the film  2  is permanently connected to the substrate  1  through a welding seam  13 . A pressing device  21 , which preferably is a component of an operating device, serves for connecting the films  2 ,  3  to each other and for limiting the transporting duct  19 . 
     The position, number and width of the deflection duct or ducts, as well as the stiffness of the films, determine the cross section and the volume of the transporting duct  19 . 
       FIG. 5  explains different possibilities for film deflection. 
       FIGS. 5   a  and  5   b  illustrate the possibility, already discussed above, for the pneumatic and hydraulic pressure application to a deflecting duct  20 . 
       FIG. 5   c  explains the possibilities for deflecting the films  2 ,  3  by means of a mechanical element  22  which engages in a throughopening  23  in the substrate  1 . It may be advantageous in this connection if the mechanical element  22  is heated. By the equalization of the shapes of the element  22  and the film  2 , as well as the equalization between the film  2  and the film  3 , the heat can be transmitted very well to the fluid contained in the transporting duct, which is in particular advantageous for temperature changing cycles, as it is advantageous in the amplification of DNA by means of PCR, so that the transporting device for carrying out PCR and similar processes in microfluidic flow cells. For carrying out temperature exchange cycles, either the temperature of an element  22  can be actively varied or different elements  22  with constant temperatures can be connected with positive engagement successively to the film  3 . 
     In accordance with  FIG. 5   d , in the passage opening, a plastically or elastically deformable filling  24  is provided, which transmits the movement of the mechanical element  22 , wherein the filling  24  is composed of a silicon or thermoplastic elastomer. 
     The suitable stiffness of the deflecting film and the manner in which the deflection can take place make it possible to control the force necessary for the pump actors. 
       FIGS. 6 and 7  show further embodiments for actor devices. 
     An actor device  17 ′ according to  FIG. 6  has, instead of actors which are only capable of translatory movement, rollers  25  which carry out a rolling movement in accordance with arrow  27  in addition to a translatory movement according to arrow  26 , and which can transport a fluid by displacing a closing front in the transporting duct  19 . 
     An actor device  17 ″ illustrated in  FIG. 7  closes the transporting duct  19  over its entire length. Accordingly, the arrangement of  FIG. 7  has the function of a valve. 
       FIG. 8  shows an embodiment of a structural pump group with three successively arranged chambers or transporting ducts  19 ′,  19 ″,  19 ″′, which are connected to each other through overflow ducts  28  and  29 . An actor  30 ,  30 ′ and  30 ″ is assigned to each of the transporting ducts  19 ′,  19 ″ and  19 ″′. By successively actuating the actors, a fluid can be transported from an inlet duct  8  to an outlet duct  9  or vice-versa. 
     The volume of the transporting duct  19  formed by deflection of the films  2 ,  3  may also depend, through the extent of the deflection of the film  3  beyond the film  2 , on the input pressure of the fluid to be transported. In order to be able to take into consideration volumes of the transporting duct of different sizes during the fluid transport, it is essential to know the respective size of the transporting duct. 
       FIG. 9  shows various possibilities for measuring the deflection, or the magnitude of the volume of the transporting duct. In particular in applications in which the input pressure of a fluid to be transported is variable, for example, in the field of medicament dosing, it may be necessary to control the deflection of the films in order to be thereby able to control the flow through the pump, for example, by adjusting the pump frequency. 
       FIG. 9   a  shows an actor  31  with a light conductor  32 . The light conductor  32  sends light to a reflecting surface  37  on the film  3  in the transporting duct  19  and receives reflected light whose intensity depends on the respective elongation of the film  3  and the position  31  of the actor. From the light measurement in connection with a determination of the position of the actor, it is possible to determine the elongation of the film, and thus, the inner volume of the transporting duct. 
     In accordance with  FIG. 9   b , the light emitting and receiving light conductor  32  is not a component of the actor, but is arranged in a throughopening  23  in the substrate  1 . 
     In accordance with  FIG. 9   c , the measurement of the capacity of an electrode  33  on an actor  34 , and an electrode  35  on the film  3 , takes place in the area of the transporting duct  19 . The same configuration could be used for carrying out the measurement of the deflection of the film  3  by means of a conductivity measurement. In that case, the electrode  35  is preferably constructed as a conductive strip, for example, in the form of a strip shaped electrically conductive, especially metal, coating or imprint parallel to the longitudinal axis in the transporting direction of the duct  19 . Preferably, as illustrated in  FIG. 9   c , it is not necessary to separately contact the metal coating. According to  FIG. 9   c , at least two of the actors  18 ,  34  are each equipped with an electrode  33 , wherein the electrodes are electrically connected through an evaluating circuit. If one of the at least two actors is in the non-actuated state and the other is in the actuated state, the electrode  35  is contacted by the second actor, but not by the first. Correspondingly, current cannot flow between the two electrodes  33 . When actuating/moving the second actor, this second actor comes into contact, when contacting the film  3 , with the electrode  35  located on the film  3 , and current can flow between the electrodes  33  of the two actors. The time or the distance which the first actor requires from its initial position until contacting the film  3  is therefore a measure for the degree of deflection under pressure of the film  3  and can be utilized for carrying out the control. In the same manner, a configuration of several electrodes at a defined distance along the width of the transporting duct could be used, wherein the number of electrodes which are short circuited in accordance with the above described principle provides the information concerning the degree of the deflection of the film  3  caused by pressurization. 
       FIG. 9   d  shows a measuring transporting duct  19 ′ with an electrode  35  which is only used for measuring purposes and is not subjected to pumping action. The measurement of the deflection of the film  3  takes place capacitively between the electrode  35  and a further electrode  36 . 
     Also possible is the use of eddy current sensors for measuring the deflection of the film  3 . 
       FIG. 10  shows a structural group, with a substrate  1  and films  2 ,  3  and  4 , which differ from the structural pump group according to  FIGS. 1 to 4  in that a transporting duct  19 ″, to be formed between the film  2  and the film  3 , is open at one end because a connection between the films is not present. At the other end, the transporting duct is in connection with a further duct  9 . 
     The transporting duct  19 ″ is hydrophilically conditioned for filling by capillary action by providing internal surface modifications or coatings, for example, by wet chemical treatment, corona treatment, plasma treatment or polymerization. 
     By actuating an actor  16 , the transporting duct  19 ″ is formed and a liquid sample  40 , for example, a drop of blood on the skin of a finger, enters at the open end into the transporting duct  19 ″ by capillary action. The inlet opening of the further duct  9  in this case, forms a capillary stop. After filling, the transporting duct  19 ″ is closed at the open end by means of an actor  38  and the actor  16  is then taken back. The films  2 ,  3  then again rest flat against the substrate  1  by ejecting the liquid sample which had been taken into the further duct  9 . 
     According to  FIG. 11 , a further duct  9 ′ is also hydrophilically conditioned so that the mentioned capillary stop action is eliminated and a liquid sample enters also the further duct  9 ′ through the transporting duct  19 ″. An actor  39  closes the filled duct  9 ′. The device according to  FIG. 11  thereby acts as a valve. 
     The actors  16 ,  38  and  41  can be part of an operating device or part of a housing component of a disposable flow cell, wherein the housing component may be movable or slidable relative to the flow cell.