Microfluidic device and method for operating a microfluidic device

Abstract

A method for operating a microfluidic device (115) for analyzing sample material is presented. The microfluidic device (115) is designed as a pressure-based microfluidic device with at least one pneumatically actuated, membrane-based fluid displacement chamber (451, 452, 453). The method comprises a step of transferring a liquid volume (420) containing the sample material between a first microfluidic chamber (451) and a second microfluidic chamber (452) at a predefined flow velocity through a microfluidic connecting channel (461, 462) connecting the chambers (451, 452) to break up or separate a gas bubble (425) contained in the liquid volume (420). The connecting channel (461, 462) has a spatial dimension that is less than one third of a spatial dimension of at least one of the chambers (451, 452).

Description

State of the art

[0001] The invention relates to a method for operating a microfluidic device for analyzing sample material and to a microfluidic device for analyzing sample material according to the preamble of the independent claims. The present invention also relates to a computer program.

[0002] Microfluidic analysis systems (so-called lab-on-chips, or LoCs for short) enable automated, reliable, fast, and cost-effective processing of patient samples, for example, for medical diagnostics. By combining a variety of operations for the controlled manipulation of fluids, complex molecular diagnostic test sequences can be performed in a microfluidic device, also known as a lab-on-chip cartridge. The processing of the lab-on-chip cartridge and the analysis of the patient sample can be performed in a compact analysis device. Different types of microfluidic analysis systems are known in the state of the art, which are also referred to as lab-on-chip platforms or lab-on-chip systems.Such lab-on-chip platforms pursue various technological approaches to deliver microfluidic operations: Centrifugal-based lab-on-chip systems, for example, utilize the centrifugal, Coriolis, and Euler forces that occur in a lab-on-chip cartridge set in controlled rotation. Another class of lab-on-chip platforms are pressure-based systems, which achieve controlled fluid transport within a microfluidic cartridge by applying at least two pressure levels to it.For this purpose, the microfluidic cartridge has, in particular, a plurality of pneumatic microchannels for the defined guidance of a gaseous medium subjected to overpressure or underpressure, such as air or an inert gas, within the microfluidic cartridge, as well as a microfluidic network of fluidic microchannels for guiding liquids within the microfluidic cartridge.

[0003] During operation of such microfluidic devices, gas bubbles can also form in a liquid. Compared to centrifugal-based lab-on-chip systems, which allow such gas bubbles to be easily removed by centrifuging the microfluidic device, taking advantage of the existing density difference and high centrifugal forces, the acceleration forces that can be generated in a pressure-based microfluidic system are generally lower, which can make the separation of gas bubbles more difficult. Disclosure of the invention

[0004] Against this background, the approach presented here provides a method for operating a microfluidic device for analyzing sample material and a microfluidic device for analyzing sample material according to the main claims. The measures listed in the dependent claims enable advantageous refinements and improvements of the device specified in the independent claim.

[0005] According to embodiments, the elimination of gas bubbles in a liquid can be enabled, particularly for a pressure-based microfluidic device. Thus, a method that enables the elimination—that is, in particular, the fragmentation or separation—of a gas bubble in a liquid volume in a suitable microfluidic device, in particular without requiring centrifugation of the device, and the corresponding suitable microfluidic device can be provided, particularly for use in pressure-based microfluidic systems with membrane-based fluid displacement chambers.

[0006] A method for operating a microfluidic device for analyzing sample material is presented, wherein the microfluidic device is designed as a pressure-based microfluidic device with at least one pneumatically actuated membrane-based fluid displacement chamber, the method comprising the following steps: Transferring a liquid volume containing the sample material between a first microfluidic chamber and a second microfluidic chamber at a predefined flow velocity through a microfluidic connecting channel connecting the chambers to divide or separate a gas bubble contained in the liquid volume, wherein the connecting channel has a spatial dimension that is smaller than one-third of a spatial dimension of at least one of the chambers. The transfer can be carried out, in particular, by actuating the pneumatically actuated membrane-based fluid displacement chamber.

[0007] The microfluidic device can, for example, be a microfluidic analysis system in the form of a lab-on-chip (LoC) cartridge, which can comprise a microfluidic network for processing fluids, for example, for analyzing patient samples. Thus, in addition to the chambers and the connecting channel, the microfluidic device can also have further devices and additional or alternative structures, for example, among others, structures for conducting fluids to the chambers and the connecting channel. The microfluidic device can be used for microfluidic lab-on-chip systems for medical diagnostics. A fluid displacement chamber can be understood in particular as a microfluidic pump chamber or, more generally, as a chamber having an actuator, in particular a deflectable membrane, for displacing fluid from the chamber.The spatial dimension can be a width, in particular a width between two opposing walls, which are arranged in particular parallel to the flow direction of the liquid volume, of the channel or the respective chamber, a height, and additionally or alternatively a length, a cross-sectional area, or the like. The spatial dimension can be understood in particular as the cross-sectional area of ​​a microfluidic structure that is perpendicular to the mean flow direction in a segment of the microfluidic device, such as the connecting channel or the two microfluidic chambers. The connecting channel can also be referred to as a microfluidic constriction or microfluidic bottleneck, or can comprise such a constriction.

[0008] In other words, a method for eliminating a gas bubble from a liquid volume present in a microfluidic chamber can be provided, comprising a step of transferring the liquid volume through a microfluidic constriction or bottleneck and at a sufficient flow velocity into a second microfluidic chamber. After the liquid volume with the gas bubble passes through the microfluidic bottleneck, the gas bubble in the liquid volume is divided into at least two gas bubbles. Advantageously, the combination of the bottleneck with the sufficiently high flow velocity creates sufficiently large shear forces to divide the gas bubble.A predefined flow velocity is therefore understood to mean, in particular, a value of a flow velocity of the liquid volume in the connecting channel that is sufficiently large so that the microfluidic shear forces acting on the gas bubble when passing through the constriction between the chamber and the connecting channel are sufficiently large to split the gas bubble into at least two parts. This has the advantage that the at least two gas bubbles present after the splitting of the initial gas bubble each have a smaller volume and a smaller diameter compared to the initially present gas bubble. For example, the reduced gas bubbles can be removed particularly easily via a channel with a small cross-section.In addition, by splitting the gas bubble, it can be ensured, for example, that the gas bubble is not present along the entire vertical extent of a microfluidic chamber and thus does not impair the evaluation of a fluorescence signal of the liquid volume in the microfluidic chamber.

[0009] According to one embodiment, the transferring step can be carried out once or repeatedly. In particular, the transferring step can be carried out until the gas bubble is divided into at least two, preferably more than two, parts. In this case, the gas bubble can be moved back and forth, in particular, between the two microfluidic chambers. Such an embodiment offers the advantage that by repeatedly carrying out the transferring step, the gas bubble can be successively divided into a plurality of smaller gas bubbles. As a result, even in the event that the microfluidic shear forces acting on the gas bubble during a single initial execution of the transferring step may not be sufficient to bring about immediate, in particular even multiple, division of the gas bubble, a reliable division of the gas bubble can be achieved overall.This can be achieved, in particular, by subjecting the gas bubble to varying shear forces depending on its positioning in the microfluidic flow field and its state of motion. Consequently, by repeatedly transferring the liquid volume with the gas bubble and the resulting variations in the positioning and state of motion of the gas bubble, the probability of successful fragmentation of the gas bubble can be increased.

[0010] The method can also include a step of aligning the microfluidic device in the Earth's gravitational field at a predetermined angle or angular range to the field lines of the gravitational field, in particular in an angular range between 0 and 60 degrees, for example at an angle of approximately 30 degrees. This has the advantage that, in addition to the microfluidic forces acting on gas bubbles contained in the liquid volume, a buoyancy force can also be used to remove the gas bubbles. This allows for the overall elimination of a gas bubble from a liquid volume in a combined manner by microfluidically fragmenting the gas bubble and utilizing the gravity or buoyancy force acting on the gas bubbles.

[0011] Furthermore, the transfer step can be repeated multiple times through the same microfluidic connecting channel. This allows for a particularly simple design of the microfluidic device. In particular, just two microfluidic chambers connected to one another via a microfluidic connecting channel, which can function as a constriction, can be sufficient to carry out the method. Furthermore, repeated execution can ensure that gas bubbles present in the liquid volume are dispersed in a particularly reliable manner. Because such a system has only two actuation states, which can be directly converted into one another, a particularly rapid transition between the states is possible.This allows the method to be advantageously combined particularly easily and flexibly with other process steps of a microfluidic process and to be carried out particularly quickly. For example, during a temperature control step, the liquid volume can remain in the same temperature-controlled chamber almost the entire time, and is only briefly moved out of the chamber during the transfer step and immediately re-entered to break up or remove gas bubbles.

[0012] Furthermore, the transfer step can be carried out by deflecting a flexible membrane into at least one fluid displacement chamber. As explained above, a fluid displacement chamber can be understood to mean, in particular, a microfluidic pump chamber or, more generally, a chamber having an actuator, in particular a deflectable membrane, for displacing fluid from the chamber. Such an embodiment offers the advantage that, through the use of a flexible membrane, a precisely defined and controlled displacement of the liquid volume from a microfluidic chamber or fluid displacement chamber can be achieved. In particular, a virtually complete transfer of the liquid volume from the first to the second microfluidic chamber can be achieved.In an advantageous embodiment, the fluid displacement chamber can in particular have a lens-shaped design with chamfered side walls in order to achieve, on the one hand, a good flow through the entire fluid displacement chamber and, on the other hand, to achieve an almost complete liquid volume transfer. Depending on the positioning of the initially present gas bubble in the microfluidic chamber or fluid displacement chamber, the lens-shaped design of the chamber in combination with a pressure-based deflection of the elastic membrane into the fluid displacement chamber can, if necessary, exert particularly large shear forces on the initial gas bubble present in the liquid volume upon deflection of the membrane and displacement of the liquid volume from the chamber or fluid displacement chamber. Furthermore, such a chamfered design of the side walls can prevent excessive sticking, i.e.Excessive adhesion of the flexible membrane to the chamber walls can be prevented. The microfluidic displacement volume of such a membrane-based fluid displacement chamber can, for example, be between 10 µl and 50 µl, and preferably between 20 µl and 30 µl.

[0013] The deflection of the membrane into the fluid displacement chamber can be actuated pneumatically. In this way, a particularly fast, simple and defined actuation of the fluid displacement chamber can take place and, if sufficient pneumatic pressure is applied to actuate the fluid displacement chamber, sufficiently large dynamic shear forces can be exerted on a gas bubble enclosed in the liquid volume. In this case, an overpressure is applied to expel a fluid displacement chamber and a negative pressure is applied to suck in via a fluid displacement chamber. The overpressure can be, for example, between 200 mbar and 3000 mbar, preferably between 1000 mbar and 2000 mbar, and the negative pressure can be, for example, between 0 mbar and 900 mbar, preferably between 400 mbar and 800 mbar.The flexible membrane can, for example, be formed from a thermoplastic elastomer with a thickness between 50 µm and 200 µm, for example 100 µm, and have a sufficiently low modulus of elasticity.

[0014] The first chamber can also be designed as a fluid displacement chamber. Additionally or alternatively, the second chamber can be designed as a fluid displacement chamber. In particular, the transfer step can be effected by moving the liquid volume back and forth between fluid displacement chambers or between exactly two fluid displacement chambers that are connected to one another via the microfluidic connecting channel. In this way, the method can be carried out in a particularly simple, efficient, and time-saving manner. Furthermore, a microfluidic device for carrying out the method according to this advantageous embodiment can be realized in a particularly compact, cost-effective, and sustainable or resource-saving manner.

[0015] According to one embodiment, the transferring step can be performed at a frequency of 0.3 Hertz to 10 Hertz or 3 Hertz to 5 Hertz. According to one embodiment, the frequency can correspond to an actuation frequency with which the deflection of a flexible membrane into at least one fluid displacement chamber is carried out. In this way, on the one hand, rapid dynamic fragmentation of the gas bubble can be achieved by the shear forces acting at the interface, and on the other hand, simple control of the microfluidic device for generating the fluid flow can be achieved, for example, using a processing unit with pneumatic multi-way valves and pump-fed pressure reservoirs.

[0016] Furthermore, after the transfer step has been performed, continuation of the method can be delayed for a predefined waiting period. In other words, a delay step can be performed after the transfer step. In this way, for example, gas bubbles trapped in the liquid volume can be dissipated by the buoyancy force acting on them or the inertial forces resulting from a previous pumping process.

[0017] A microfluidic device for analyzing sample material is also presented, wherein the microfluidic device is designed as a pressure-based microfluidic device with at least one pneumatically actuated membrane-based fluid displacement chamber, wherein the device has the following features: a first microfluidic chamber for containing a liquid volume containing the sample material and a second microfluidic chamber for containing the liquid volume; and a microfluidic connecting channel connecting the chambers for dividing or separating a gas bubble contained in the liquid volume, wherein the connecting channel has a spatial dimension that is less than one third of a spatial dimension of at least one of the chambers, wherein the chambers and the connecting channel are designed to enable a transfer of the liquid volume between the chambers at a flow velocity through the connecting channel that is substantially predefined by the applied pneumatic pressure, the viscosity of the liquid and the fluidic resistance.

[0018] In other words, a microfluidic device is presented, comprising at least one pneumatically actuated membrane-based fluid displacement chamber, a microfluidic connecting channel, and a second chamber, wherein the first chamber and the second chamber are connected to one another via the microfluidic connecting channel such that a fluid transfer between the first and the second chamber can take place via the microfluidic connecting channel, wherein a spatial dimension of the microfluidic connecting channel is smaller than a spatial dimension of the first and the second chamber. In the operational state of the device, exactly one of the chambers can comprise a fluid volume with at least one gas bubble enclosed in the fluid volume, wherein the gas bubble has a diameter that is larger than the spatial dimension of the microfluidic connecting channel between the first and the second chamber.In this way, the microfluidic device is designed particularly advantageously so that upon transfer of the liquid volume with the enclosed gas bubble through the microfluidic connecting channel, a geometric deformation of the interface between the gas volume of the gas bubble and the liquid surrounding the gas bubble occurs and thus a fragmentation of the gas bubble is promoted by the shear forces acting on the interface of the gas bubble.

[0019] According to one embodiment, the first chamber and the second chamber can be arranged one above the other with respect to the Earth's gravitational field when the device is in an operational state. This can favor the accumulation of gas bubbles trapped in the liquid volume in the upper chamber of the two with respect to the gravitational field.

[0020] The first chamber and the second chamber can also have an identical displacement volume within a tolerance range. Such an embodiment offers the advantage of enabling a complete and precisely defined transfer of the entire liquid volume from one chamber to the other, thus promoting the efficient elimination of a gas bubble present in the liquid volume. The first and second chambers can, for example, be lens-shaped, whereby pumping of liquid can be achieved via the pneumatically actuated deflection of a flexible membrane within the chambers, which can be designed, for example, as fluid displacement chambers.

[0021] Furthermore, a cavity for separating gas can be arranged adjacent to one of the chambers, fluidically connected to this chamber. In this way, a gas bubble initially present in a liquid volume can be removed, discharged, or eliminated from the region of the two chambers. For this purpose, the adjacent cavity can, for example, initially be filled with liquid, which can be at least partially displaced by at least part of the gas volume of the initially present gas bubble.

[0022] Furthermore, the connecting channel can have a spatial dimension that is less than one-fifth of the spatial dimension of at least one of the chambers. Such an embodiment offers the advantage that, in the region of an expansion of the microfluidic structure from the connecting channel toward the chambers, particularly high microfluidic shear forces can be exerted on the interface of a gas bubble present in a liquid volume, thus promoting the fragmentation of the gas bubble in a transfer step.

[0023] According to one embodiment, the connecting channel can have a meandering section. In this way, the strength of the shear forces acting on the interface of a gas bubble present in a liquid volume can be further increased if necessary. If the microfluidic connecting channel has a greater length due to the meandering design compared to a straight or at least partially straight design, a higher fluidic resistance occurs when flowing through the microfluidic connecting channel with a meandering pattern, even with a comparable channel cross-section. Thus, the time required for flow through the microfluidic connecting channel can be specifically adjusted by precisely designing the meandering channel.Furthermore, the interaction of the liquid with the channel walls of the microfluidic connecting channel and in particular the existing momentum transfer of the channel walls to the liquid can be advantageously used to achieve improved mixing of the liquid by transferring the liquid through the microfluidic connecting channel.

[0024] The method mentioned herein can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

[0025] The approach presented here further provides a control unit configured to perform, control, or implement the steps of a variant of the method presented here in corresponding devices. This embodiment of the invention in the form of a control unit also allows the problem underlying the invention to be solved quickly and efficiently.

[0026] For this purpose, the control unit can have at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading sensor signals from the sensor or for outputting control signals to the actuator, and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a microcontroller, or the like, wherein the memory unit can be a flash memory, an EEPROM, or a magnetic storage unit.The communication interface can be designed to read in or output data wirelessly and / or wired, wherein a communication interface that can read in or output wired data can read this data, for example, electrically or optically from a corresponding data transmission line or output it to a corresponding data transmission line.

[0027] In this case, a control unit can be understood as an electrical device that processes sensor signals and outputs control and / or data signals depending on them. The control unit can have an interface that can be implemented in hardware and / or software. In a hardware implementation, the interfaces can, for example, be part of a so-called system ASIC, which contains a wide variety of functions of the control unit. However, it is also possible for the interfaces to be separate integrated circuits or to consist at least partially of discrete components. In a software implementation, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.

[0028] In an advantageous embodiment, the control unit controls the process. This control is achieved, in particular, via actuators, which, for example, enable the application of different pressure levels to the individual pneumatic connections of the device.

[0029] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular when the program product or program is executed on a computer or a device.

[0030] Furthermore, an analytical device is presented that comprises an embodiment of the control device mentioned herein. The analytical device is configured to analyze input samples. For this purpose, a microfluidic device can be inserted into a receiving area of ​​the analytical device. The analytical device is also configured to effect operation of a microfluidic device inserted into the receiving area.

[0031] Furthermore, a system is presented which comprises an embodiment of the analysis device mentioned herein and an embodiment of the microfluidic device mentioned herein.

[0032] Examples of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows: Fig. 1 a schematic representation of an analysis device according to an embodiment; Fig. 2 a schematic representation of a control unit according to an embodiment; Fig. 3 is a flowchart of an embodiment of a method for operating a microfluidic device; Fig. 4 schematic representations of a part of a microfluidic device according to an embodiment; Fig. 5 schematic representations of a part of a microfluidic device according to an embodiment; and Fig. 6 a schematic representation of a part of a microfluidic device according to an embodiment.

[0033] In the following description of advantageous exemplary embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted. The features described in the exemplary embodiments can each be implemented individually and / or in combination with one another. If an exemplary embodiment comprises an "and / or" connection between a first feature and a second feature, this should be read to mean that the exemplary embodiment, according to one embodiment variant, has both the first feature and the second feature, and according to a further embodiment variant, either only the first feature or only the second feature.

[0034] Fig. 1 shows a schematic representation of an analysis device 100 according to one embodiment. In this embodiment, the analysis device 100 is designed to analyze input samples, allowing PCR tests, for example, to be performed. For this purpose, a microfluidic device 115, which is merely an example of a cartridge with a plastic housing and a microfluidic network for processing the sample, can be inserted into a receiving area 102. In this embodiment, the analysis device 100 further comprises a display 104 with a touch function, via which, merely an example of a cartridge, settings for the desired analysis process can be manually entered. Furthermore, the display 115 is designed merely as an example to display analysis results. The analysis device 100 further comprises a control device 110. The control device 110 is designed to operate the microfluidic device 115 or to control its operation.The control unit 110 will be discussed in more detail with reference to the following figures.

[0035] A special design of pressure-based lab-on-chip systems is based on the use of a flexible membrane, which is integrated into the lab-on-chip cartridge, which can also be referred to as a microfluidic device 115, and is used to create the liquid transport in the cartridge. This occurs in particular through a pressure-based, i.e., pneumatically controlled deflection of the membrane into designated recesses in the cartridge, thereby causing a targeted displacement of liquids. The deflection of the membrane occurs in particular via pneumatic microchannels, so that a defined deflection of the membrane into the designated recesses can achieve targeted liquid transport in the microfluidic network of the cartridge.

[0036] The integration of a flexible membrane into the lab-on-chip cartridge combines several advantages: For example, a targeted deflection of the membrane into designated cavities or recesses can be used to create microfluidic valves and pumping chambers within the cartridge, which can displace and process defined volumes of liquid. Furthermore, by using a flexible membrane integrated into a lab-on-chip cartridge, the liquids are almost completely enclosed within the cartridge, with only venting channels being required. This prevents environmental contamination by the sample, or vice versa. Furthermore, such microfluidic lab-on-chip cartridges can be manufactured cost-effectively from polymers using series production processes such as injection molding, injection-compression molding, stamping, or laser transmission welding.

[0037] In other words, active microfluidic elements, in particular membrane-based valves and pump chambers, are used to control and / or establish fluid transport within such a microfluidic cartridge or device 115. By deflecting the flexible membrane onto a valve saddle or into a pump chamber, the microfluidic flow through a channel is controlled and / or microfluidic transport of liquids is established.

[0038] The active microfluidic elements are controlled in particular by a processing unit or the analysis device 100 and via pneumatic microchannels integrated into the microfluidic device 115. For this purpose, the microfluidic device 115 has, in particular, a pneumatic interface to the processing unit. The pneumatic interface is, on the one hand, suitably designed to enable control by the processing unit and, on the other hand, suitably implemented in the microfluidic device 115 to allow control of all active microfluidic elements in the microfluidic device 115.

[0039] Typically, a plurality of active microfluidic elements are controlled via a common pneumatic interface with multiple pneumatic ports, which can therefore also be referred to as a manifold. By designing the pneumatic interface as a manifold comprising multiple pneumatic ports, pneumatic control of the microfluidic device 115 in an external processing unit or the analysis device 100 can be achieved in a particularly simple and compact manner. In addition to, for example, such a manifold as a pneumatic interface, the processing unit also has additional interfaces to the microfluidic lab-on-chip cartridge, such as thermal interfaces for controlling the temperature of liquids in the lab-on-chip cartridge or an optical interface for evaluating a fluorescence signal.

[0040] An important operation within a molecular diagnostic test procedure, which can be performed in such a lab-on-chip cartridge or microfluidic device 115 in a processing unit or analysis device 100, is the execution of an amplification reaction to specifically amplify nucleic acids. A frequently used amplification method is the polymerase chain reaction. This is based on a repeated, cyclic execution of the steps of denaturation, annealing, and elongation, which must take place at different temperatures, such as 95°C, 55°C, and 72°C. Consequently, thermal cycling of the reaction volume is required to perform a polymerase chain reaction.

[0041] In addition to controlling the temperature of the reaction volume in a stationary chamber with a heat exchange interface, the system described above also offers a particularly advantageous way of controlling the temperature of the reaction liquid by microfluidically pumping the liquid volume back and forth between different microfluidic pump chambers whose walls have different temperatures. In this way, particularly rapid thermal cycling of a liquid volume in the device 115 can be achieved, whereby even a low thermal conductivity, such as that of polymers, of the device 115 is sufficient.

[0042] To perform an amplification reaction, however, a reaction mix, such as a master mix for a polymerase chain reaction, must first be prepared. The reagents required for this can be provided, in particular, in the form of a freeze-dried, lyophilized dry reagent, such as a so-called reaction bead. The reaction mix can be prepared by dissolving the dry reagent with an elution buffer, which in particular contains purified sample material.The dry reagent is stored in a dedicated pre-storage chamber upstream of the microfluidic device 115, which is implemented in the network of the device 115 via at least two microfluidic channels. For example, the first microfluidic channel can be used to supply liquid to the dry reagent pre-storage chamber and the second microfluidic channel can be used to vent the dry reagent pre-storage chamber. However, there is fundamentally the possibility that, upon dissolving the bead in a liquid, a gas bubble forms in the liquid volume. This gas bubble is formed in particular by a gas such as air or an inert gas. This gas bubble is initially enclosed within the bead before the bead is completely detached from the surrounding liquid, and is then released into the liquid volume upon dissolving the bead.

[0043] Furthermore, even if a liquid is simply heated, for example in connection with carrying out an amplification reaction, the formation of a gas bubble in the liquid volume can occur, since the solubility of gases in an aqueous medium is generally temperature-dependent and decreases with increasing temperature.

[0044] The formation of a gas bubble in a liquid volume can be undesirable. For example, this can affect a fluorometric measurement, such as if the liquid volume is a reaction mix for conducting a quantitative polymerase chain reaction or another reaction with fluorometric detection of the reaction characteristics, such as an isothermal amplification method. Furthermore, such a gas bubble can represent a dead volume and thus impair the establishment of a defined concentration in a liquid solution during a dissolution process. Furthermore, a gas bubble in a pressure-driven membrane-based microfluidic system can have a detrimental effect on pumping processes, for example, if the gas bubble adheres to a fluid displacement chamber and thus affects the generation of a fluid flow via the fluid displacement chamber.

[0045] According to embodiments, a method is therefore provided, particularly for use in pressure-based microfluidic systems with membrane-based fluid displacement chambers, which allows, for example, the elimination—that is, in particular, the fragmentation or separation—of a gas bubble present in a liquid volume. Furthermore, according to embodiments, a suitable microfluidic device is provided, which is particularly advantageously suited for carrying out such a method.

[0046] Fig. Figure 2 shows a schematic representation of a control unit 110 according to an embodiment. The control unit 110 corresponds to or is similar to the control unit of Fig. 1. The control unit 110 is designed to control the microfluidic device from Fig. 1 or a similar microfluidic device or to control the operation thereof. The microfluidic device is designed as a pressure-based microfluidic device with at least one pneumatically actuated membrane-based fluid displacement chamber.

[0047] The control unit 110 comprises a transfer device 214 for transferring a liquid volume containing the sample material between a first microfluidic chamber and a second microfluidic chamber at a predefined flow velocity through a microfluidic connecting channel connecting the chambers for dividing or separating a gas bubble contained in the liquid volume. The microfluidic device has a first chamber, a second chamber, and a connecting channel. The connecting channel has a spatial dimension that is smaller than one-third of a spatial dimension of at least one of the chambers. The transfer device 214 is designed, for example, to actuate or control at least one pneumatically actuated membrane-based fluid displacement chamber of the microfluidic device.

[0048] According to one embodiment, the control unit 110 also includes an alignment device 212 for aligning the microfluidic device in the Earth's gravitational field at a predetermined angle or angular range relative to the field lines of the gravitational field. The angular range is, in particular, between 0 and 60 degrees. The angle is, for example, approximately 30 degrees. The alignment device 212 is designed, for example, to actuate or control an actuator for supporting or controlling the second alignment of the device.

[0049] Fig. 3 shows a flow diagram of an embodiment of a method 300 for operating a microfluidic device. The method 300 for operating is executable to use the microfluidic device for analyzing sample material from Fig. 1 or a similar microfluidic device, or to control the operation thereof. The method 300 for operation can be carried out using the control device from one of the figures described above or a similar control device. The microfluidic device is designed as a pressure-based microfluidic device with at least one pneumatically actuated membrane-based fluid displacement chamber.

[0050] The method 300 for operating comprises a step 314 of transferring a liquid volume containing the sample material between a first microfluidic chamber and a second microfluidic chamber at a predefined flow velocity through a microfluidic connecting channel connecting the chambers to divide or separate a gas bubble contained in the liquid volume. The connecting channel has a spatial dimension that is less than one-third of a spatial dimension of at least one of the chambers.

[0051] According to one embodiment, transferring step 314 is performed once or multiple times. In particular, transferring step 314 is performed multiple times through the same microfluidic connecting channel. According to one embodiment, after transferring step 314 has been performed, a continuation of the method is delayed for a predefined waiting period, for example, a waiting period of 0.3 to 3 seconds. A continuation of the method can be understood as a repetition of transferring step 314 and / or an execution of another method step.

[0052] According to one embodiment, transferring step 314 is performed by deflecting a flexible membrane into at least one fluid displacement chamber. In particular, the deflection of the membrane into the fluid displacement chamber is pneumatically actuated. For example, the first chamber is configured as a fluid displacement chamber and / or the second chamber is configured as a fluid displacement chamber. According to one embodiment, transferring step 314 is performed at a frequency of 0.3 Hertz to 10 Hertz or 3 Hertz to 5 Hertz.

[0053] According to one embodiment, the method 300 for operating also comprises a step 312 of aligning the microfluidic device in the gravitational field of the Earth at a predetermined angle or angular range to the field lines of the gravitational field, in particular in an angular range between 0 and 60 degrees, for example at an angle of approximately 30 degrees.

[0054] According to one embodiment, Fig. 3 is a schematic flow diagram of the method 300 that can be carried out for the fragmentation of gas bubbles in a liquid volume in a microfluidic device, with a repeated execution of the transferring step 314, as follows: In a first embodiment of step 314 of transferring, the liquid volume with at least one enclosed gas bubble is pumped from the first microfluidic chamber into the second microfluidic chamber, The transfer of the liquid volume between the first and second microfluidic chambers takes place via the microfluidic connecting channel. The microfluidic connecting channel of the microfluidic device is designed as a constriction or point, whereby sufficiently large shear forces are exerted on the at least one gas bubble present in the liquid volume. The transfer step takes place, for example, by means of a membrane-based fluid displacement chamber, which leads to the liquid transfer by displacing liquid from the respective microfluidic chamber. The actuation or operation of the membrane takes place, in particular, pneumatically, with a sufficiently large pressure being applied to cause a deflection of the membrane and a displacement of liquid in the microfluidic system.

[0055] In a second embodiment of transfer step 314, the liquid volume is transferred from the second microfluidic chamber back into the first microfluidic chamber. The second embodiment of transfer step 314, or the back transfer, can be carried out, for example, by a combined pneumatic deflection of the membrane in the region of the second microfluidic chamber for a targeted displacement of the liquid volume present there and a pneumatic suction of the membrane in the region of the first microfluidic chamber for a targeted suction of the liquid volume into the first microfluidic chamber.

[0056] In a third and fourth embodiment of transfer step 314, the first and second embodiments are repeated, for example. In this way, a reliable and, for example, multiple fragmentation of the initial gas bubble in the liquid volume can be achieved.

[0057] According to one embodiment, method 300 additionally comprises a step 312 of aligning the device in the Earth's gravitational field in order to utilize the buoyancy force acting on the gas bubbles for improved removal of the gas bubbles. Alignment step 312 is performed, in particular, before transferring step 314. For example, the microfluidic device is aligned in the Earth's gravitational field with the plane in which the microfluidic network is present such that a non-vanishing force component of the gravitational field is present within the plane of the microfluidic network, wherein, in particular, the first and second microfluidic chambers are at different potentials in the Earth's gravitational field.

[0058] Fig. Figure 4 shows schematic representations of a portion of a microfluidic device 115 according to an embodiment. The microfluidic device 115 corresponds to or is similar to the microfluidic device from one of the previously described figures. The microfluidic device 115 is a microfluidic device 115 for analyzing sample material. The microfluidic device 115 is designed as a pressure-based microfluidic device with at least one pneumatically actuated membrane-based fluid displacement chamber.

[0059] Fig. Figure 4 illustrates, using a chronological series of five images (A, B, C, D, and E), which are, for example, fluorescence microscopic images, of the microfluidic device 115 with pneumatically actuated membrane-based fluid displacement chambers, an implementation of the method described herein. The five images (A, B, C, D, and E) in Fig. 4 each show a part or section of the microfluidic device 115 in a top view, with insets on the left side of the figures showing an enlarged region of the microfluidic device 115 that is particularly relevant for a step of the method. The enlarged region of the microfluidic device 115 is marked in each figure by a box with a dashed line.

[0060] Generally speaking, the microfluidic device 115 comprises a first microfluidic chamber 451 for containing a liquid volume 420 containing the sample material, a second microfluidic chamber 452 for containing the liquid volume 420, and a microfluidic connecting channel 461 connecting the chambers 451, 452 for dividing or separating a gas bubble 425 contained in the liquid volume 420. The connecting channel 461 has a spatial dimension that is smaller than one-third of a spatial dimension of at least one of the chambers 451, 452. The chambers 451, 452 and the connecting channel 461 are designed to enable a transfer of the liquid volume 420 between the chambers 451, 452 at a predefined flow rate through the connecting channel 461.

[0061] According to the embodiment illustrated here, the microfluidic device 115 comprises a series circuit of three chambers 451, 452, and 453, which are all designed, for example, as membrane-based microfluidic fluid displacement chambers. The chambers 451, 452, and 453 are connected to each other via two microfluidic connecting channels 461 and 462.

[0062] According to one embodiment, at least one of the chambers 451, 452, and 453 is designed as a membrane-based microfluidic fluid displacement chamber. In particular, at least two of the chambers 451, 452, and 453 are arranged one above the other in an operational state of the microfluidic device 115 with respect to the gravitational field of the Earth. The first chamber 451 and the second chamber 452, as well as, according to the embodiment shown here, also the third chamber 453, have a displacement volume that is identical within a tolerance range. In particular, the connecting channel 461 and / or 462 has a spatial dimension that is smaller than one-fifth of a spatial dimension of at least one of the chambers 451, 452, and 453. Even if Fig. 4 is not explicitly shown, a cavity for separating gas, which is fluidically connected to the respective chamber, can be arranged adjacent to at least one of the chambers 451, 452 and 453 and, additionally or alternatively, the connecting channel 461 and / or 462 can have a meander-shaped section.

[0063] In a first figure A of Fig. 4, a liquid volume 420 is present in the first chamber 451 of the three fluid displacement chambers, which has several enclosed gas bubbles 425. Even after the initial transfer of the liquid volume 420, a significant gas bubble 425 is present in the liquid volume 120, as shown in a second figure B in Fig. 4. Only after repeated transfers back and forth between the first chamber 451 and the second chamber 452 is the liquid volume 420 without a larger gas bubble 425, as can be seen from a third Fig. and a fourth Fig. in Fig. 4. Gas bubbles 425 can be separated at the upper end of the third fluid displacement chamber or chamber 453. Finally, by repeatedly performing the transferring step, or in other words, by repeatedly transferring and re-transferring, a liquid volume 420 can be produced without a visible trapped gas bubble. In the fifth figure E in Fig. 4, a liquid volume 420 free of or almost free of air bubbles can be seen as a result of the process.

[0064] The volume of a fluid displacement chamber or chamber 451, 452, 453 is, for example, between 10 µl and 30 µl, preferably 20 µl. The overpressure for actuating a fluid displacement chamber is, for example, between 500 mbar and 3000 mbar, preferably 1400 mbar; the negative pressure for actuating a fluid displacement chamber is, for example, between 0 mbar and 800 mbar, preferably 700 mbar. The membrane has, for example, a thickness between 70 µm and 150 µm, preferably 100 µm, and is formed from a thermoplastic elastomer such as thermoplastic polyurethane. The actuation frequency is, for example, between 1 Hz and 5 Hz, preferably 3 Hz.

[0065] The resulting volume flow when transferring a liquid volume is, for example, 30 µl / s to 1000 µl / s, a (minimal) cross-section of the connecting channel through which the liquid transport takes place is, for example, 100 × 100 µm 2= 0.01 µl / mm to 1000 × 1000 µm 2 = 1 µl / mm, the average flow velocity in the connecting channel is, for example, 0.03 m / s to 10 m / s. For efficient fragmentation of gas bubbles, the kinetic energy during the transfer of the liquid is particularly greater than the surface energy of the interface between a gas bubble and the surrounding liquid, or the inertial forces of the liquid are greater than the surface forces at the interface of a gas bubble, so that the resulting shear forces at the interface of the gas bubble promote fragmentation.

[0066] Fig. Figure 5 shows schematic representations of a part of a microfluidic device 115 according to an embodiment. The representations or illustrations in Fig. 5 are similar to the illustrations and figures from Fig. 4. Fig. 5 shows a Fig. 4 comparable chronological series of figures A, B, C, D and E, which illustrates an implementation of the method described herein on a microfluidic device 115. The microfluidic device 115 and the method used here correspond to or are at least similar to the device and the method used in Fig. 4. In a similar manner, a successive fragmentation of the gas bubble 425 enclosed in the liquid volume 420 can also be achieved. The initial, see Figure A in Fig. 5, the gas bubble 425 present in the liquid volume 420 can be separated in particular by multiple transfers and re-transfers of the liquid volume 420 between the chambers 451 and 452 via the connecting channel 461, so that finally, see Figure E in Fig. 5, there is no longer any larger visible gas bubble in the liquid volume 420.

[0067] Fig. Figure 6 shows a schematic representation of a part of a microfluidic device 115 according to an embodiment. The microfluidic device 115 corresponds to or is similar to the microfluidic device from one of the figures described above. In other words, Fig. 6 shows a schematic representation of a microfluidic device 115 with pneumatically controllable membrane-based fluid displacement chambers, which can be used to carry out the method mentioned herein.

[0068] According to the embodiment shown here, the microfluidic device 115 comprises three chambers 451, 452, 453 of at least approximately equal size, each designed here as a fluid displacement chamber with a volume of, for example, 20 µl each, two microfluidic connecting channels 461 and 462 which connect the first chamber 451 and the second chamber 452 as well as the second chamber 452 and the third chamber 453 to one another, and two pneumatically controllable microfluidic valves 690 and 695 in order to separate the chambers 451, 452, 453 and the connecting channels 461 and 461 from the further microfluidic network of the device 115 if necessary.

[0069] The control of the chambers 451, 452, 453, designed here as fluid displacement chambers, as well as the microfluidic valves 690, 695, is achieved via pneumatic microchannels 671, 672, 673, which can be controlled from an external processing unit or an external analysis device via a pneumatic interface with a plurality of ports 692, 693. The microfluidic connecting channels 461 and 462 have a reduced cross-section compared to the chambers 451, 452, 453 in order to exert microfluidic shear forces on any gas bubbles that may be present in the liquid volume when a liquid volume is pumped back and forth between at least two of the chambers 451, 452, 453.

[0070] With reference to the figures described above, exemplary embodiments are explained again in other words and in summary below.

[0071] Overall, the microfluidic network of the presented microfluidic device 115 comprises in particular an arrangement of active microfluidic elements such as valves 690, 695 and pump chambers or

[0072] Chambers 451, 452, 453, which are connected to each other and to other passive, i.e., non-pneumatically controllable, elements via a network of microfluidic channels 461, 462, 671, 672, 673. The other passive elements include, for example, liquid reagent storage chambers, at least one closable sample input chamber, a filter chamber with an integrated filter element, at least one liquid storage chamber, and vent openings.

[0073] The microfluidic device 115 is realized, for example, in the form of a polymer cartridge and in particular by a polymer multi-layer structure, so that it can be manufactured cost-effectively from polymer materials by using series production processes such as injection molding, injection compression molding, punching and / or laser transmission welding.

[0074] The active microfluidic elements, e.g., the valves 690, 695 and pump chambers or chambers 451, 452, 453, are used in particular for the pneumatically controlled production and control of the microfluidic flow in the microfluidic network of the microfluidic device 115. The active microfluidic elements are, in particular, microfluidic valves 690, 695 and pump chambers orChambers 451, 452, 453, which are each designed to cause a displacement of liquids from a partial volume provided for this purpose of liquid-conducting structures of the device 115, and which can be controlled in particular pneumatically by a processing unit provided for this purpose, here for example the analysis device 100, via an interface with pneumatic ports, so that a fully automated microfluidic processing of the liquids in the device 115, which is designed for example as a polymer cartridge, can be achieved.

[0075] The active microfluidic elements, i.e., for example, the valves 690, 695 and pump chambers or chambers 451, 452, 453, are designed according to one embodiment using a flexible membrane that adjoins two further rigid polymer components, with fluid-conducting structures located in at least one of the further polymer components. A microfluidic valve 690, 695 is realized by separating two fluid-conducting structures by a particularly pneumatically induced deflection of a membrane into a designated and particularly advantageously shaped partial volume of the fluid-conducting structures. A microfluidic pump chamber 451, 452, 453 is closely related to the valve 690, 695 and is also based on the displacement of fluids from designated areas of fluid-conducting structures of the device 115.In contrast to valves 690, 695, pump chambers 451, 452, 453 generally have a larger displacement volume and are used in particular for temporarily holding defined volumes of liquid and in particular for holding a significant part or the entire or almost the entire volume of a liquid to be processed in one step of a microfluidic process.

[0076] In this case, a microfluidic pump chamber 451, 452, 453 can, for example, be used advantageously, particularly in combination with two microfluidic valves 690, 695 enclosing the pump chamber 451, 452, 453, in order to realize a pump unit that enables the highest possible flow rates to be produced in the microfluidic device 115 in the most compact space possible. This is achieved in particular by designing the pump unit from a pump chamber 451, 452, 453 with a large displacement volume, which is used for pumping, i.e., for the directed displacement of liquids, and two valves 690, 695 with a small displacement volume, which, through a suitable actuation scheme, are used solely to determine and establish the pumping direction.Overall, such a pumping unit is characterized by a large pumping volume per pumping step, a small space requirement for the realization of the pumping unit and by a pulsatile, i.e., strongly temporally variable flow rate profile.

[0077] In order to achieve pumping with a flow rate that is as constant and less variable as possible, peristaltic pumping by peristaltic actuation of at least three similar active microfluidic elements is particularly suitable, wherein the at least three active microfluidic elements have a similar volume and in particular almost the same volume. Peristaltic pumping with three similar active microfluidic elements can be achieved regardless of their, for example, identical displacement volume, i.e. in particular both through the use of microfluidic valves 690, 695, which can have a small displacement volume, or through the use of microfluidic pump chambers 451, 452, 453, which can in particular have a larger displacement volume.

[0078] Consequently, with regard to peristaltic fluid transport, a conceptual distinction between valve and pump chamber is irrelevant. This conceptual separation only makes sense if the microfluidic elements are used multifunctionally: A microfluidic element that, in addition to establishing peristaltic fluid transport, is primarily used to control the microfluidic flow within the microfluidic device 115 is therefore referred to in particular as a microfluidic valve 690, 695.A microfluidic element which, in addition to producing a peristaltic liquid transport, is primarily used to generate the microfluidic flow and to temporarily store a significant portion of the liquid volume 420 to be processed within the microfluidic device 115 is therefore referred to in particular as a microfluidic pump chamber 451, 452, 453.

[0079] Depending on the functionalities used of a microfluidic element, an advantageous embodiment is carried out: A microfluidic valve 690, 695 and in particular a microfluidic control or isolation valve, i.e. a microfluidic valve 690, 695 which is used exclusively for controlling the microfluidic flow or for isolating liquid-conducting structures, and not for peristaltic liquid transport, therefore has in particular the smallest possible displacement volume, on the one hand in order to have the smallest possible liquid volume which is to be flushed in a microfluidic process, and on the other hand in order to achieve the most compact possible realization of the microfluidic device 115.A pump chamber 451, 452, 453, which is used in particular for the defined storage and measuring of liquids, on the other hand, has in particular a predetermined displacement volume, for example 20 µl, which essentially corresponds to the liquid volume 420 to be processed or at least a significant fraction thereof.

[0080] Regardless of the fluid transport mechanism and the precise design of an active microfluidic element, fluid transport within the microfluidic device 115 is achieved, as described above, by deflecting a flexible polymer membrane into fluid-conducting recesses of a rigid polymer component, so that a controlled displacement of fluids within the microfluidic device 115 can be achieved, in particular by applying different pressure levels to a pneumatic interface of the device 115. In addition to the active, i.e., pneumatically controlled, microfluidic elements for establishing and controlling fluid transport in the fluidic network, the device 115 as a whole comprises, in particular, the passive components described below: Liquid reagent pre-storage chambers are used, in particular, for the long-term stable pre-storage and defined release of liquid reagents required for conducting a test procedure in the device 115. In particular, the pre-storage chambers contain all liquid reagents required for conducting a test procedure. Thus, with the exception of the sample, no additional liquids need to be introduced into the device 115 by the user in order to conduct a test procedure fully automatically within the device 115.

[0081] A sample input chamber is designed, in particular, for introducing a sample, for example, a flocked swab containing a swab sample or a sample liquid, i.e., a liquid containing components of a sample, into the device 115. The sample input chamber can, in particular, be closed by means of a lid element in order to be able to exclude contamination of the environment by the sample or, conversely, of the sample by the environment.

[0082] In addition, a filter chamber with a filter element can be integrated into the microfluidic network for extracting components from a sample fluid. The filter element can, for example, be a silica mesh suitable for extracting deoxyribonucleic acids (DNA) or ribonucleic acids (RNA).

[0083] A liquid storage chamber is particularly designed to receive and store liquids, such as portions of a sample liquid, particularly after components have been extracted by the filter element. The liquids can, for example, remain in the liquid storage chamber without causing environmental contamination by the liquid, even after the test procedure on the cartridge or device 115 has already been performed. This can be ensured, in particular, by implementing a decoupling reservoir between the liquid storage chamber and the vent opening.

[0084] Vent openings serve, in particular, to vent the microfluidic system and thus ensure pressure equalization within the microfluidic system, for example, during a pumping process of a liquid from one of the liquid reagent pre-storage chambers into the liquid storage chamber. In particular, decoupling reservoirs are located in the microfluidic network upstream of the vent openings, which prevent unwanted leakage of liquid from the device 115.

[0085] The described active and passive elements are connected to one another via microfluidic channels 461, 462, 671, 672, 673 and thus form a microfluidic network which has a suitable topology, ie spatial arrangement of elements constituting the network, in order to be able to carry out at least one and in particular a plurality of different microfluidically executed test sequences in the network.

[0086] The specific implementation of device 115 is based in particular on a flexible, microstructured polymer membrane, which is welded, in particular partially, to two microstructured polymer components by laser welding, which can also be referred to as laser transmission welding. The rigid polymer components contain, in particular, fluid-conducting recesses that form the microfluidic channels 461, 462, 671, 672, 673, pump chambers 451, 452, 453, and valves 690, 695. Furthermore, at least one of the components comprises, in particular, pneumatic channels 461, 462, 671, 672, 673, which are used to control the active microfluidic elements, i.e., in particular, the pump chambers 451, 452, 453 and the valves 690, 695.The microfluidic elements are controlled in particular by a pressure-based, locally defined deflection of the elastic membrane into the recesses of the polymer components forming valves 690, 695 and pump chambers 451, 452, 453. At least two pressure levels are used to control the microfluidic elements. In particular, the control and provision of the pressure levels is carried out by the analysis device 100 or an external processing unit, which in particular has a pneumatic interface, a so-called manifold, to the device 115.

[0087] Example dimensions and specifications for the microfluidic device 115 are listed below.

[0088] Basic exemplary specifications of the microfluidic device 115: Lateral dimension of the microfluidic device 115: 30 × 30 mm 2 up to 300 × 300 mm 2 , preferably 50 × 50 mm2 up to 200 × 200 mm 2 , for example 118 × 78 mm 2 . Displacement volume of a microfluidic pump chamber or fluid displacement chamber 451, 452, 453: 10 µl to 50 µl, preferably 15 µl to 25 µl, for example 20 µl. Displacement volume of a microfluidic valve 690, 695: 30 nl to 1 µl, preferably 100 nl to 300 nl. Cross-section of a microfluidic channel 461, 462: for example, 400 µm × 600 µm. Volume of a dry reagent pre-storage chamber: 10 µl to 50 µl, preferably 20 µl to 30 µl, for example 25 µl.

[0089] Materials and manufacturing processes for the realization of the microfluidic device 115: - Components with liquid-carrying structures: Polymers such as polycarbonate (PC), styrene-acrylonitrile copolymer (SAN), polypropylene (PP), polyethylene (PE), cycloolefin copolymer (COP, COC), polymethyl methacrylate (PMMA). - Flexible membrane: Thermoplastic elastomers (TPE) such as polyurethane (TPU) or styrene block copolymer (TPS). - Processes for manufacturing and assembling components: Series production processes such as injection molding, injection compression molding, punching, laser welding.

[0090] Fluids used in the microfluidic device: - Aqueous solutions, in particular buffer solutions, in particular with components of a sample liquid. - Sample fluid: In particular, an aqueous solution containing sample material, particularly of human origin, obtained from, for example, body fluids, swabs, secretions, sputum, or tissue samples. The targets to be detected in the sample fluid are particularly of medical, clinical, therapeutic, or diagnostic relevance and can be, for example, bacteria, viruses, certain cells, such as circulating tumor cells, cell-free DNA, or other biomarkers.

[0091] Gravity field for buoyancy-driven removal of gas bubbles: Earth's gravitational field with a gravitational acceleration of approximately 9.81 m / s 2 ; in particular, the device 115 is aligned at a predetermined angle or angular range to the field lines of the gravitational field; the alignment can, for example, be at an angle between 0 and 60 degrees, for example at an angle of 30 degrees.

[0092] The dimensions and specifications mentioned are exemplary. The properties of the fluids used and the material properties and surface properties of the materials used to construct the device 115 are also important for the design and functionality of the device 115.

Claims

[1] Method (300) for operating a microfluidic device (115) for analyzing sample material, wherein the microfluidic device (115) is designed as a pressure-based microfluidic device with at least one pneumatically actuable membrane-based fluid displacement chamber (451, 452, 453), the method (300) comprising the following steps: Transferring (314) a liquid volume (420) containing the sample material between a first microfluidic chamber (451) and a second microfluidic chamber (452) at a predefined flow rate through a microfluidic connecting channel (461, 462) connecting the chambers (451, 452) for dividing or separating a gas bubble (425) contained in the liquid volume (420), wherein the connecting channel (461, 462) has a spatial dimension that is smaller than one third of a spatial dimension of at least one of the chambers (451, 452). [2] The method (300) according to claim 1, wherein the step (314) of transferring is performed once or multiple times. [3] Method (300) according to one of the preceding claims, comprising a step (312) of aligning the microfluidic device (115) in the gravitational field of the Earth at a predetermined angle or angular range to the field lines of the gravitational field, in particular in an angular range between 0 and 60 degrees, for example at an angle of approximately 30 degrees. [4] Method (300) according to one of the preceding claims, wherein the step (314) of transferring is carried out repeatedly through the same microfluidic connection channel (461, 462). [5] Method (300) according to one of the preceding claims, wherein the step (314) of transferring is carried out by deflecting a flexible membrane into at least one fluid displacement chamber (451, 452, 453). [6] Method (300) according to claim 5, wherein the deflection of the membrane into the fluid displacement chamber (451, 452, 453) is pneumatically actuated. [7] Method (300) according to one of claims 5 to 6, wherein the first chamber (451) is designed as a fluid displacement chamber and / or the second chamber (452) is designed as a fluid displacement chamber. [8] Method (300) according to one of the preceding claims, wherein the step (314) of transferring is carried out at a frequency of 0.3 Hertz to 10 Hertz or of 3 Hertz to 5 Hertz. [9] Method (300) according to one of the preceding claims, wherein after execution of the step (314) of transferring, a continuation of the method (300) is delayed for a predefined waiting period. [10] Microfluidic device (115) for analyzing sample material, wherein the microfluidic device (115) is designed as a pressure-based microfluidic device with at least one pneumatically actuated membrane-based fluid displacement chamber (451, 452, 453), wherein the device (115) has the following features: a first microfluidic chamber (451) for containing a liquid volume (420) comprising the sample material and a second microfluidic chamber (452) for containing the liquid volume (420); and a microfluidic connecting channel (461, 462) connecting the chambers (451, 452) for dividing or separating a gas bubble (425) contained in the liquid volume (420), wherein the connecting channel (461, 462) has a spatial dimension that is smaller than one third of a spatial dimension of at least one of the chambers (451, 452), wherein the chambers (451, 452) and the connecting channel (461, 462) are designed to enable a transfer of the liquid volume (420) between the chambers (451, 452) at a predefined flow velocity through the connecting channel (461, 462). [11] Microfluidic device (115) according to claim 10, wherein the first chamber (451) and the second chamber (452) are arranged one above the other with respect to the gravitational field of the Earth in an operational state of the device (115). [12] Microfluidic device (115) according to one of claims 10 to 11, wherein the first chamber (451) and the second chamber (452) have a displacement volume that is identical within a tolerance range. [13] Microfluidic device (115) according to one of claims 10 to 12, wherein adjacent to one of the chambers (451, 452) there is arranged a cavity for separating gas, said cavity being fluidically connected to said chamber (451, 452). [14] Microfluidic device (115) according to one of claims 10 to 13, wherein the connecting channel (461, 462) has a spatial dimension that is smaller than one fifth of a spatial dimension of at least one of the chambers (451, 452). [15] Microfluidic device (115) according to one of claims 10 to 14, wherein the connecting channel (461, 462) has a meander-shaped section.

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