WO2008139415A1

WO2008139415A1 - Microfluidic device and method of operating a microfluidic device

Info

Publication number: WO2008139415A1
Application number: PCT/IB2008/051879
Authority: WO
Inventors: Marc W. G. Ponjee; Mark T. Johnson; Murray F. Gillies
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-05-14
Filing date: 2008-05-13
Publication date: 2008-11-20

Abstract

A micro fluidic device (100) for analysing a fluidic sample (201), the micro fluidic device (100) comprising a casing (101) enclosing a sample chamber and a turning mechanism (105) adapted for turning the casing (101).

Description

Micro fluidic device and method of operating a micro fluidic device

FIELD OF THE INVENTION

The invention relates to a microfluidic device. Further, the invention relates to a system for analysing a fluidic sample. Moreover, the invention relates to a method of operating a microfluidic device.

BACKGROUND OF THE INVENTION

Microfluidic devices are at the heart of many biochip technologies, being used for both the preparation of fluidic (for instance blood based) samples and their subsequent analysis. A biosensor is an example of a microfluidic device and may be used for the detection of an analyte that combines a biological component with a physicochemical or physical detector component.

A sample solution may comprise any number of components, including, but not limited to, bodily fluids (for instance blood, urine, serum, lymph, saliva, anal and vaginal secretions, perspiration and semen) of virtually any organism, with mammalian samples being preferred and human samples particularly preferred, environmental samples (for instance air, agricultural, water and soil samples), biological warfare agent samples, research samples (that is in the case of nucleic acids, the sample may be the products of an amplification reaction, including both target and signal amplification), purified samples, such as purified genomic DNA, RNA, proteins, etc., raw samples (bacteria, virus, genomic DNA, etc.). Virtually any experimental manipulation may have been done on the sample.

Integrated devices comprising biosensors and microfluidic devices are generally known. Such devices generally comprise small volume wells or reactors, in which chemical or biochemical reactions are performed and the results examined, and may regulate, transport, mix and store minute quantities of fluids rapidly and reliably to carry out desired (bio)chemical reactions and analysis in large numbers. By carrying out assays in small volumes, significant savings can be achieved in time and the costs of targets, compounds and reagents. The market for nucleic acid detection for medical, environmental, food and forensic applications is growing rapidly. Temperature control is often of vital importance in biotechnology applications, where controlled heating provides functional capabilities, such as mixing, dissolution of solid reagents, thermal denaturation of proteins and nucleic acids, enhanced diffusion rates of molecules in the sample, and modification of surface binding coefficients. A number of reactions, including DNA amplification techniques, ligand binding, enzymatic reactions, extension, transcription and hybridization reactions are generally carried out at optimized, controlled temperatures. Furthermore, temperature control may be necessary to operate microfluidic pumps and reversible/irreversible valves that are thermally actuated.

An example of a biochemical process that requires reproducible and accurate temperature control is high-efficiency thermal cycling for DNA amplification using polymerase chain reaction (PCR). PCR is a temperature controlled and enzyme-mediated amplification technique for nucleic acid molecules, usually including periodical repetition of three reaction steps: a denaturing step at 92-96 ⁰C, an annealing step at 37-65 ⁰C and an extending step at ~72 ⁰C. PCR can produce millions of identical copies of a specific DNA target sequence within a short time, thus has become a routinely used procedure in many diagnostic, environmental, and forensic laboratories to identify and detect a specific gene sequence.

Conventional arrays of temperature control elements have been described, for instance consisting of individually controlled elements (US 2004/0053290 Al) or based on CMOS technology (WO 2005/037433 Al).

In an active matrix approach, individual heaters may be addressed line-at-a- time. An active matrix array may be fabricated from one of the well-known large area electronics technologies, such as a-Si, LTPS (low-temperature polysilicon) or organic technologies. Besides a TFT (thin film transistor) as a switch, also diodes or MIM (metal- insulator-metal) diodes/switches can be used as active elements.

Conventional bioassays based on lab-on-a-chip technologies require not only a microfluidic cartridge but also an analysis apparatus in which the cartridge is inserted. The analysis apparatus performs and controls the (bio)chemical processing step(s) on the cartridge. However, operation of conventional analysis apparatuses may lack flexibility.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the invention to provide a sample analysis system with an efficient operability. In order to achieve the object defined above, a microfluidic device, a system for analysing a fluidic sample, and a method of operating a microfluidic device according to the independent claims are provided. In a first aspect the invention relates to a microfluidic device (100) for analyzing a fluidic sample (201), the microfluidic device (100) comprising a casing (101) enclosing a sample chamber; a turning mechanism (105) adapted for turning at least a part of the microfluidic device (100), particularly adapted for turning the casing (101).

According to an exemplary embodiment of the invention, a microfluidic device for analysing a fluidic sample is provided, the microfluidic device comprising a casing enclosing a sample chamber and a turning (or pivoting or rotating or oscillation) mechanism adapted for turning (or pivoting or rotating or oscillating) the casing.

According to another exemplary embodiment of the invention, a system for analysing a fluidic sample is provided, the system comprising a microfluidic device having the above mentioned features for analysing the fluidic sample and an analysis device for performing an analysis using the microfluidic device.

According to still another exemplary embodiment of the invention, a method of operating a microfluidic device for analysing a fluidic sample is provided, the method comprising turning a casing of the microfluidic device enclosing a sample chamber.

In the context of this application, the term "sample" may particularly denote any solid, liquid or gaseous substance to be analysed, or a combination thereof. For instance, the substance may be a liquid or suspension, furthermore particularly a biological substance. Such a substance may comprise proteins, polypeptides, nucleic acids, lipids, carbohydrates or full cells, etc.

The "substrate(s)" and/or the "casing" may be made of any suitable material, like glass, plastics, or a semiconductor. According to an exemplary embodiment, it may be advantageous to provide a substrate which is partially or (essentially) entirely transmissive for an electromagnetic radiation beam such as a light beam for reading out a sensor surface. For example, when using a light beam, a glass substrate may be an appropriate choice. The term "substrate" may be thus used to define generally the elements for layers that underlie and/or overlie a layer or portions of interest. Also, the "substrate" may be any other base on which a layer is formed, for example a glass or metal layer.

The term "sample chamber" may particularly denote a three-dimensional volume which is provided to accommodate a sample. This volume may be, for instance, in the order of magnitude of milliliters, microliters or nano liters. The term "turning mechanism" may particularly denote any specific configuration, provision or adaptation of a micro fluidic device allowing the micro fluidic device to be turned around one or more predefined axes (for instance for vertically flipping the device) by a predefined angle (for instance 90° or 180°). Also an oscillation of the microfluidic device around a center (similar like a pendulum) may fall under the term turning. Such a turning mechanism may be operated by an automatic mechanism (such as an electromotor under control of a control mechanism) or manually (for instance by muscle force of a human operator operating a grip or the like).

The term "temperature controller" may particularly denote any entity for measuring, adjusting, regulating, manipulating or influencing a temperature of the fluidic sample in the sample space. This may include heating, cooling or simply controlling.

The term "thermal barrier mechanism" may particularly denote any apparatus, entity or procedure provided for supplying a thermal barrier in a volume between an upper level of the fluidic sample and a lower surface of an upper portion of the casing/housing. Such a thermal barrier may provide thermal insulation between the fluidic sample and the upper portion of the casing to avoid heating energy or cooling energy losses. A thermal barrier may also be formed by employing a thermal 'switch', for example consisting of a memory metal or a bimetal, or anything that causes thermal coupling/decoupling.

The terms "upper portion" and "lower portion" may particularly relate to an arrangement of the microfluidic device which is appropriate for using the microfluidic device for detecting particles in a fluidic sample. Therefore, "low" and "upper" may be defined by the vector of the gravitational force and may relate to a lab coordinate system in which the device is operated.

According to an exemplary embodiment of the invention, a microfluidic device, for instance for applications in the field of life science, may be provided which has implemented a mechanism allowing to turn or rotate or pivot the microfluidic device around one or more of its axes. Such a rotation/motion may be advantageous since, for instance under the influence of the gravitational force, a sample accumulated in a lower portion of a sample chamber may be moved within the sample chamber, thereby allowing for a selective interaction or prohibition of such an interaction between the sample and functional features (such as a sensor-active area or a temperature controller) provided at specific portions of the microfluidic device. Such a rotation/motion may also be advantageous since it may allow to selectively alter the positional relationship between individual components of the device, for instance for positioning an optical detection unit relative to a specific one of a plurality of sensor portions to be read out by the optical detection unit.

For instance, enhanced performance of a microfluidic device may be enabled by agitating fluid, thermocycling, sequential processing of cartridges with overlap in the process steps, i.e. such a processing of a subsequent cartridge can be started before the total bioassay of the previous cartridge is finished. Furthermore, dual- side readout and/or dual- side sensor performance may be made possible, thereby allowing to improve the performance and reduce the costs per sensor event.

According to an exemplary embodiment of the invention, flipping of a lab-on- a-chip in an analysis apparatus is made possible. With flipping it may be particularly meant that the microfluidic device is rotated at least partly over at least one of its axis such that thereafter, the bottom (or top) face of the device is no longer in plane with the bottom (or top) face of the device before flipping. Examples of a microfluidic device are a lab-on-a-chip (LOC), micro total analysis system (μ-TAS) or microfluidic device that deals with part of a bioassay. Bioassays based on lab-on-a-chip (i.e. μ-TAS) technologies are often complicated devices comprising functionalities including, microfluidics, temperature control and/or readout. What is often over looked, however, is the analysis apparatus in which the cartridge is inserted. The analysis apparatus performs and controls the (bio)chemical processing step(s) on the cartridge. According to an exemplary embodiment of the invention, it is enabled to

(partially) flip a microfluidic device such as that used in molecular diagnostics, while a bioassay is being performed. The assay may, for instance, be for clinical, food or forensic applications. In particular, embodiments of the invention may improve the read-out of a micro-array (for instance based on hybridisation) by reduction of the background signal, and enable a higher throughput of cartridges in an analysis apparatus.

According to an exemplary embodiment of the invention, a cartridge can also be removed from a reader, flipped over and re-inserted in the reader.

In general, the user may insert the cartridge in the analysis apparatus according to a specified orientation. However, a change in orientation of the cartridge during the bio- assay may be required or beneficial to improve the performance of the bioassay and/or the performance of the analysis apparatus (for instance throughput). According to exemplary embodiments of the invention, many situations may occur that require or benefit from such flipping of a cartridge during the bioassay. Embodiments of the invention may improve the read-out of a micro-array (for instance based on hybridisation) by reduction of the background signal. In further embodiments, a higher throughput in an analysis apparatus may be enabled in which the micro fluidic devices (cartridges) are loaded. Embodiments of the invention are not limited to the explicit examples given herein, but flipping of a cartridge during a bioassay may be applied during and in between other steps of a bioassay, such as cell lysing, DNA extraction, etc.

In the following, further exemplary embodiments of the micro fluidic device will be explained. However, these embodiments also apply to the system for analysing a fluidic sample and the method of operating the micro fluidic device.

The casing of the microfluidic device may be completely closable or completely closed. In a completely closed condition, the sample may be entirely decoupled from influences of the environment, and may be sealed against the environment. This may also allow to prevent the sample from flowing out of the sample space when the microfluidic device is flipped or rotated.

The turning mechanism may be adapted for turning the casing in a manner that a first portion of the casing is converted from a lower portion of the casing into an upper portion of the casing, and that a second portion of the casing is converted from an upper portion of the casing into a lower portion of the casing. By reversing the inner surface of the sample chamber which is in direct contact with the sample, it is possible to selectively bring the sample in contact or out of contact with specific functional features (such as temperature controllers, sensors, etc.) provided at or in the surface of the sample chamber.

A temperature controller may be provided and located in the first portion of the casing, and may be adapted for controlling a temperature of the fluidic sample located in a sample chamber. Such a temperature controller may selectively influence the sample temperature with marginal heat losses by thermal equilibration procedures between the sample and the upper casing portion which is suppressed or eliminated since the gravitational force brings the sample only in contact with the lower portion of the casing, not with the upper portion of the casing. The temperature controller may comprise a heater, particularly a resistive heater such as an ohmic heater or an inductive heater. However, other heating procedures are possible, for instance a Peltier heater, an electromagnetic radiation based heater, etc. The temperature controller may also comprise a cooler, for instance a Peltier cooler. This may allow to perform a temperature adjustment or even complex temperature cycles. The second portion of the casing may be free of a temperature controller. Therefore, the temperature controller has to be provided only once in a microfluidic device allowing for a cost-efficient production of the device. By turning the device, the sample can be brought, in a fast manner, out of interaction with the temperature controller, thereby allowing a refined temperature control or regulation. Particularly, heating or cooling may be stopped quickly (without a need to wait until thermal equilibration procedures have finished) by simply turning the device upside down.

According to an exemplary embodiment, the microfluidic device may comprise a further casing enclosing a further sample chamber and a further temperature controller located in a first portion of the further casing and adapted for controlling a temperature of a fluidic sample located in the further sample chamber. The turning mechanism may be adapted for turning the further casing in a manner that the first portion of the further casing is converted from an upper portion of the further casing into a lower portion of the further casing, and that a second portion of the further casing is converted from a lower portion of the further casing into an upper portion of the further casing. Beyond this, a temperature reference unit may be provided, may be adapted for providing a predefined temperature reference and may be arranged between the first portion of the casing and the first portion of the further casing. Such a configuration is shown in Fig. 7 and corresponds to a multi-compartment microfluidic device. In such a compartment, a temperature reference plate, that is to say a temperature reference medium or a passive cooling element needs to be provided only once and in common for several compartments, allowing for a miniature and cost efficient production of the microfluidic device.

The microfluidic device may further comprise a sensor-active structure located at a surface of the first portion of the casing. Such a sensor-active structure may comprise capture molecules, a magnetic sensor area, an electric sensor area, a chemical sensor surface, etc. The sensor-active structure comprising capture molecules may be read out optically, magnetically, or electrically. Such a capture molecule comprising sensor-active structure may be operated in accordance with hybridization events which may occur between bound capture molecules and complementary particles to be detected. Since such a hybridization is highly sensitive, this may serve as a basis for a sensor principle.

The second portion of the casing may be free of a sensor-active structure. In this case, a sensor event may be carried out in a scenario in which the sensor-active structure is brought in an interaction with the sample to be analyzed. When the entire microfluidic device is reversed, the lower inner surface of the sample chamber which is then brought in contact with the sample to be analyzed does not carry out a sensor event, and the sensor- active structure being out of contact with the sample can then be read out conveniently without possibly disturbing fluid.

Alternatively, also the second portion of the casing may comprise a sensor- active structure. Then, by flipping in combination with the influence of gravitation, it may be selected which one of the two (or more ) sensor-active structures is presently brought in interaction with fluidic sample which will - under the influence of the gravitational force - accumulate in a lower volume portion of the sample chamber.

The microfluidic device may comprise a detection separation structure between the first portion of the casing and the second portion of the casing for enabling a separate detection of the sensor event of the sensor-active structure located at the surface of the first portion of the casing and the sensor-active structure located at the surface of the second portion of the casing. Such a detection separation structure may be, for instance, an optical barrier (for instance opaque or reflective) or a filter (interference or polarisation based) preventing light which is used for reading out a fluorescence sensing experiment from impinging on another sensor surface, which might generate disturbing background fluorescence radiation. Such a feature may be particularly advantageously applied in a microfluidic device having a plurality of chambers or a plurality of detection surfaces operating independently from one another. The microfluidic device may comprise a barrier generation mechanism adapted for providing a barrier in one of the group consisting of the upper portion of the sample chamber and the lower portion of the sample chamber to decouple the fluidic sample from one of the group consisting of the lower portion of the sample chamber and the upper portion of the sample chamber. For instance, an apparatus may be provided in which a closed or sealed sample chamber accommodating a sample is intentionally provided with a low thermal conductivity substance to bridge a space between an upper level of the fluidic sample on the one hand and a bottom surface of the upper portion of the casing enclosing the sample space on the other hand. This technical teaching may particularly allow improving the heating/cooling efficiency or the transfer of thermal energy from/to heating and/or cooling elements which may be provided in a lower portion of the casing and the fluidic sample. This may allow for a faster thermodynamic equilibrium between the fluidic sample and the lower portion of the housing, and therefore an accelerated sensor procedure. Further sufficient flexibility or compressibility of the (for instance gaseous) thermal barrier may allow the expansion of the fluidic sample under the influence of heat to be compensated. The microfluidic device may comprise a detection unit, particularly an optical detection unit, adapted for detecting a result of the analysis of the fluidic sample. Such a detection unit may include a light source and a light detector, wherein the light source may direct electromagnetic radiation onto a sensor surface, and the light detector may detect light emitted by fluorescence labels attached to molecules to be detected which have previously hybridized with capture molecules immobilized on a surface within the sample chamber.

Such a detection unit may be adapted to be turned by the turning mechanism in accordance with the turning of the casing. In other words, the detection unit may follow the motion of the casing. For example, it is then possible after having performed a hybridization detection event, to turn the casing together with the detection unit and to detect the molecules which have hybridized with the capture molecules and which are now no longer covered with a thick fluidic sample layer. Thus, the background signal may be reduced, thereby increasing the accuracy.

The detection unit may alternatively be adapted to remain spatially fixed when turning the casing. Such a configuration may be particularly advantageous in a scenario in which two sensor surfaces shall be evaluated with a single detection unit. Then, by turning the microfluidic device, the corresponding sensor portion may be brought into the detection path of the spatially fixed detection unit. This may allow to read out different sensor portions sequentially using one and the same detection unit. The turning mechanism may be adapted for turning the casing by a machine- controlled turning mechanism. Therefore, in accordance with a specific experimental sequence to be carried out, a machine may be programmed to perform a specific turning sequence in the context of a complex fluidic sample analysis procedure.

Additionally or alternatively, the microfluidic device may be adapted as a handheld device or may be inserted into a handheld device to enable a user to manually operate the turning mechanism for turning the casing. In such a scenario, the muscle force of an operator may be used to perform the turning operation of the microfluidic device.

The casing of the microfluidic device may enclose a plurality of separate sample chambers. Therefore, more than one analysis can be carried out at the same time, and the entire microfluidic device may then be turned for simultaneously turning around all of the sample chambers. Alternatively, only a specific selected sample chamber may be turned around to read out specifically this sensor device or to perform a specific operation in the context of a complex experiment or analysis procedure only with a specific sample chamber. The microfluidic device may be a sensor device, a sensor readout device, a biosensor device, a biochip, a lab-on-chip, an electrophoresis device, a sample transport device, a sample mix device, a cell lysing device, a sample washing device, a sample purification device, a sample amplification device, a polymerase chain reaction device, a sample extraction device or a hybridization analysis device. Particularly, the microfluidic device may be implemented in any kind of life science apparatus.

At least a part of an electronic circuitry of the microfluidic device may be realized in any of the large area electronics technologies such as a-Si, LTPS (low-temperature polysilicon) or organic technologies. Particularly, LTPS may be used for an electrical connection to electrodes and/or local current sources.

At least a part of the components of the microfluidic device may be integrated in the casing. This may allow to integrate not only sensors and heaters but also control electronics to form real time feedback.

Furthermore, a system may be provided incorporating a microfluidic device as described herein and further comprising an analysis device (i.e. a reading device, a benchtop device, a hand held device, etc.), whereby the turning mechanism turns the casing relative to the analysis device.

Beyond this, a system may be provided incorporating a microfluidic device as described herein and further comprising an analysis device (i.e. a reading device, a benchtop device, a hand held device, etc.), whereby the turning mechanism turns both the casing and the analysis device.

The aspects defined above and further aspects of the invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to these examples of embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

Fig. 1 illustrates flipping of a microfluidic device according to an exemplary embodiment of the invention.

Fig. 2 and Fig. 3 illustrate flipping of a microfluidic device/compartment according to an exemplary embodiment of the invention.

Fig. 4 and Fig. 5 illustrate flipping of a microfluidic device/compartment according to an exemplary embodiment of the invention. Fig. 6 illustrates a device for a miniature thermal cycling unit with heating elements on a single substrate, which is in contact with a temperature reference medium.

Fig. 7 illustrates a device according to an exemplary embodiment of the invention by which thermal cycling can be performed simultaneously on multiple cartridges using a single temperature reference plate.

Fig. 8 illustrates in-line processing of cartridges according to an exemplary embodiment of the invention by an analysis system that uses flipping of cartridges, wherein several locations are indicated in the apparatus where certain processing steps (for instance cell lysing, DNA amplification, etc.) are performed.

DESCRIPTION OF EMBODIMENTS

The illustration in the drawings is schematical. In different drawings, similar or identical elements are provided with the same reference signs.

In the following, referring to Fig. 1, a microfluidic device 100 according to an exemplary embodiment of the invention will be explained.

The microfluidic device 100 is adapted for analyzing a fluidic sample and comprises a casing 101 enclosing a sample chamber (not shown in Fig. 1) in which the fluidic sample is accommodated. Furthermore, a turning mechanism 105 is provided which is adapted for turning the casing 101. Fig. 1 shows the microfluidic device in an initial position and in three configurations after having performed different turning operations.

A view 120 shows the device 100 after turning by 180⁰C around a symmetry axis of the device 100. An illustration 130 shows the casing 101 after rotation by 90°. An illustration 140 shows the device 100 after rotating it by approximately 45°. More particularly, the turning mechanism 105 is adapted for turning the casing

101 in a manner that a first portion (or a first substrate) 106 of the casing 101 is converted from a lower portion of the casing 101 and to an upper portion of the casing 101, and that a second portion (or a second substrate) 107 of the casing 101 is converted from an upper portion of the casing 101 into a lower portion of the casing 101. This conversion is illustrated in illustration 120.

In the scenario of Fig. 1, the casing 101 is mounted on a rotatable table 102. It may also be fixed to this table by mechanic, magnetic, electric, adhering, or other provisions.

This rotatable table 102 is rotated by an electromotor 103 which is, in turn, controlled by a control unit 104 such as a CPU (central processing unit). Furthermore, a user interface 108 is provided which allows a user to control the operation of the control unit 104. The input/output unit 108 may include input elements such as a keypad, a joystick, buttons, or even a microphone of a voice recognition system. It may further comprise output elements such as a display like a LCD display, a cathode ray tube, a TFT display, a plasma display, etc.

Furthermore, a grip or turning lever 109 shaped to be manually operated by a hand of a human being is provided to allow a human user to manually rotate the micro fluidic device 100.

Furthermore, lateral side walls 112 of the casing 101 are shown. Fig. 2 and Fig. 3 show details of a portion of the microfluidic device 100 in two operation states, more particularly of the casing 101 and its interior construction.

Fig. 2 and Fig. 3 show a direction of gravity forces denoted with reference numeral 200. Furthermore, a fluidic sample 201 is shown. Above the upper level of the fluidic sample 201, a gas layer 202 acting as a thermal barrier is provided. Beyond this, an integrated heating element 203 as well as a layer 204 comprising immobilized capture probes forming a sensor active surface are shown.

The heating element 203 is part of a temperature controller located in the first portion 106 of the casing 101 and is adapted for controlling a temperature of the fluidic sample 201 located in the sample chamber, i.e. in an interior of the casing 101. The heating element 203 is a resistive heater. Furthermore, the second cover 107 of the casing 101 is free of a heating element.

The capture molecule layer 204 acts as a sensor-active structure and is provided at an inner surface of the first portion 106 of the casing 101. In contrast to this, the opposing second portion 107 of the casing 101 is free of a sensor-active surface. The gas layer 202 may serve as a barrier and may be generated by a barrier generation mechanism adapted for providing the barrier 202 in the upper portion of the sample chamber to decouple the fluidic sample 201 from the upper portion of the sample chamber, which is in Fig. 2 the second portion 107 and in Fig. 3 the first portion 106.

The embodiment of Fig. 3 and Fig. 4 is capable of flipping during micro-array analysis for enhanced performance. The detection sensitivity of the biosensor 100 is improved by flipping over the cartridge 101 that comprises the gas layer 202 (or other low refractive index material that does not mix with the fluid of interest 201) in the compartment 101 that comprises the capture site 204, for instance a hybridisation spot for DNA, or an array of capture sites (for instance a micro-array). During hybridisation, partial flipping of the sample 201 can be carried out to agitate the sample liquid and increase the change of capturing of target molecules. During this stage however, it is advantageous that the homogeneous gas layer 202 is present between the fluid of interest 201 and the substrate 107 opposite to the substrate 106 comprising the hybridisation capture sites 204 (see Fig. 2).

Prior to read-out, the microfluidic device 100 may be completely flipped over such that the gas layer 202 becomes located in between the array of hybridisation sites 204 and the fluid of interest 201 (see Fig. 3). This will happen due to the effect of gravity 200 and the differences in density between gas 202 and liquid 201. Due to the flipping, the fluid 202 containing the non-bonded target molecules is removed from the close vicinity of the surface comprising the immobilized capture spots 204. Optical read out may be carried out with any known optical detection method from the side of the device adjacent to substrate 106 in Fig. 3. As a consequence, the background signal is lowered (for instance fluorescent dyes in the fluid 202 that are not bonded to the capture spots 204 cannot be excited by the optical evanescent field), and the signal to background ratio is increased, and with that the detection sensitivity.

The sensitivity of these methods can be further enhanced by removing non- bonded molecules before detection. Numerous techniques are known to read-out a hybridization array 204 with increased sensitivity using surface-specific sensing. For example, it is possible to use the optical detection of fluorescent labels excited by evanescent waves of light passing through a light-guide directly underneath the surface comprising immobilized capture sites 204. This approach may be advantageous as the amount of excitation light reaching the fluorescent detector is low. Another example is the electrical detection of hybridised molecules for instance by measuring a change in capacitance or TFT characteristics.

The sensitivity of these methods can be further enhanced by removing non- bonded molecules before detection. To guarantee the removal of non-bonded material from the vicinity of the capture site 204 it is also possible to coat this interface with a hydrophobic layer. This will prevent liquid of the sample 202 (containing fluorescent material) from adhering to the surface 204 when the cartridge 101 is flipped for read-out.

Devices according to exemplary embodiments of the invention may incorporate a heating element 203 and/or sensing element 204, but it is not required to do so.

Incorporation of a gas layer 202 in a compartment 101 on a microfluidic device 100 comprising a micro-array 204 (for instance for genetic analysis) may be advantageous as it increases amongst others the temperature uniformity and allows for the thermal expansion of the fluid 202. Generally, the temperature of such a compartment 101 is controlled in order to define the binding of target molecules (for instance during hybridisation of DNA fragments present in the sample fluid 202). This embodiment can be applied in general to a biosensor based on surface immobilized capture spots 204 (for instance protein sensor), or to a micro fluidic device 100 comprising such a biosensor.

More generally, the (partial) flipping of a micro fluidic device (for instance biosensor) may be done during an assay by an apparatus suited to perform the assay. Such an apparatus may be a bench-top device or a handheld device suited to perform assays on the cartridges. In case of the handheld device, the user may flip the device comprising the inserted cartridge before reading-out of the biosensor (for instance micro-array) starts. Such a handheld device can be used for rapid molecular diagnostics at the point of care, or screening location, for instance airport. A simple scenario is: 1. The user inserts a cartridge comprising a biosensor into a handheld device, such that the orientation of the inserted cartridge is such that the bio-assay can be started. The preferred orientation can be indicated on the handheld device. For instance, the cartridge can be manufactured such that it only fits in one orientation in the handheld device, and the handheld device only starts with the assay when it is held in the preferred orientation. In an exemplary embodiment, the reader comprises a sensor to determine whether or not the handheld device with inserted cartridge is held in the correct orientation to start the assay. The sensor may be based on measuring the direction of gravitational forces (including centrifugal forces). In a further embodiment, indicators (for instance to signal to the user that the bio-assay may be started) and/or buttons to start the bio-assay on may be placed on the device such that the user may intuitively hold the handheld device in the correct orientation to start the bio-assay.

2. The user starts the assay by pressing a button and the assay commences.

3. At a certain moment during the assay, a signal (for instance using sound, light) is given to the user that the first part of the assay is performed, and prompts the user to flip the handheld device that incorporates the inserted cartridge. After flipping the handheld device starts to read-out the bio-sensor. Possibly, the user signals to the handheld device to start read-out after flipping. A sensor (for instance gravitational direction sensor) may be used to sense the required orientation for bio-sensor read-out and start subsequently automatically the read-out. In a further embodiment, indicators (for instance to signal to the user to flip the handheld device with cartridge) and/or buttons to continue the bio-assay may be placed on the device such that the user will intuitively hold the handheld device in the correct orientation to continue the bio-assay. For instance, a display showing the results of the assay may be placed on the face of the handheld device that should be orientated towards the user to continue the bio-assay (for instance read-out phase). ]

In the following, referring to Fig. 4 and Fig. 5, a microfluidic device 400 according to another exemplary embodiment of the invention will be explained.

In Fig. 4, the microfluidic device 400 used for bio-particle detection using immobilized capture probes 204 is shown in an operation state in which an analysis can be performed on a bottom substrate 106.

In Fig. 5, the microfluidic device 400 used for bio-particle detection using immobilized capture probes 204 is shown in an operation state in which an analysis can be performed on a top substrate 107.

In the embodiment of Fig. 4 and Fig. 5, an optical barrier 401 is shown. Furthermore, a light detector 402 and light sources 403, 404 which are used during the detection procedure are shown as well. A plurality of hybridization spots 204 are provided on both inner surfaces of the first portion 106 and of the second portion 107 of the casing.

The optical barrier 401 serves as a detection separation structure between the first portion 106 of the casing and the second portion 107 of the casing for enabling a separate detection of a sensor event at the sensor-active structure 204 at the surface of the first portion 106 of the casing and at the sensor-active structure 204 located at the surface of the second portion 107 of the casing. The optical barrier 401 prevents light generated by the light sources 403, 404 from being transmitted to the hybridization spots 204 on the opposing portion (portion 107 in Fig. 4 or portion 106 in Fig. 5) of the device 400. Therefore, in Fig. 4, the detection spots 204 located on an inner surface of the first portion 106 are detected. In the configuration of Fig. 5 which corresponds to a rotation by 180°, the detection of the hybridization spots 204 on the second portion 107 of the casing are carried out.

The embodiment of Fig. 4, Fig. 5 enables flipping during micro-array analysis for dual-side read-out. In this embodiment, a bio-cartridge 400 is flipped to enable the read- out of a dual- side biosensor (for instance a compartment or an array of compartments comprising a capture site 204 or an array of capture sites) using a single optical detection system 402 to 404.

Such a flipping may be advantageous as it may allow to use only a single optical detection system 402 to 404, which is the simplest way to allow for a reliable relative measurement of the two sides of the biosensor. In case, two optical systems are used, calibration of the incident light intensity, beam spots, detector sensitivity, etc. may be required. An additional benefit of the use of a single optical system is that less space is required in the analysis apparatus (for instance benchtop apparatus, handheld reader). Fig. 4, Fig. 5 show how such an embodiment may apply to biosensors that are read-out using light sources 403, 404 and a detector 402 on the same side of the bio-sensor 400. An optical barrier 401 is present to prevent interference in the detected optical signal by both sides 106, 107 of the substrate, for instance it prevents to excite optical dyes on the opposite substrate 106, 107 to be excited, or that prevents emitted light by the dyes on the opposite substrate 106, 107 to reach the detector 402. For example, the optical barrier 401 can be an incident light filter or emitted light filter based on interference and/or polarization. In the case of a filter based on polarization, it is possible that the optical barrier is a wire-grid with a polarization crossed with respect to the polarization of the incident light. In another embodiment, the optical barrier 401 is non-transmissive (for instance reflective and/or absorbing). In a further embodiment, the optical barrier 401 is a porous membrane, with a sufficient thickness such that the detector 402 detects no signal coming from the hybridisation sites 204 on the opposite substrate 106, 107.

The compartment 400 contains at least an inlet. Preferably, the compartment 400 comprises an outlet. In another embodiment, the sample fluid 201 can flow through or around the optical barrier 401 such that target molecules in the sample fluid 201 can hybridise on the top and bottom substrate 106, 107. The light sources 403, 404 (for instance lasers, LEDs) may comprises an excitation light filter, for instance based on interference and/or polarization. The detector 402 (for instance CCD camera) may comprise a detector filter, for instance based on interference and/or polarization. Embodiments of the invention also apply to detection principles other than discussed here, i.e. other optical detection mechanism (for instance using wave-guides and evanescent fields, plasmon optics) and non-optical detection mechanisms.

In the following, referring to Fig. 6 and to Fig. 7, a further exemplary embodiment of the invention will be explained. Fig. 6 shows a device 600 for a miniature thermal cycler with integrated heating elements 203 on a single substrate 601 which is in contact with a temperature reference medium 602. This temperature reference medium 602 serves as a passive cooling element. Reference numeral 603 denotes a TFT (Thin Field Transistor) for controlling the heating element 203. Furthermore, sensors may be provided at the position where the heaters 203 are located. A microfluidic board 604 serves as a thermal insulator. Furthermore, a matching layer/thermal diffuse layer 605 is provided between a sample space 606 on the one hand and the microfluidic board 604.

The use of a temperature reference plate 602 is advantageous for accurate and reproducibly thermal control on a microfluidic device 600 (for instance lab-on-a-chip for molecular diagnostics or chemistry) in case heating elements 203 are integrated on that microfluidic device 600, as shown in Fig. 6. The heating elements 203 allow active temperature control. In particular, the individual and independent control of the heating elements 203 may be advantageous, as it can be used to obtain a desired temperature profile in a compartment or to control the temperature per compartment. The temperature reference plate 602 is used to control the passive cooling of at least one microfluidic device 600. The integration of heating elements 203 and optional sensing elements on the device 600 may be based on active matrix technology. In view of costs, electronic elements (for instance heaters 203, sensors, switches 603) are preferably located only on a single side of a (disposable) lab- on-a-chip. In order to limit the temperature inhomogeneity across a compartment 600, the main thermal route for (passive) cooling of a device 600 is via the same substrate as that containing the heating elements 203.

Fig. 7 illustrates a microfluidic device 700 according to an exemplary embodiment of the invention. Fig. 7 shows a first compartment 701 and a second compartment 702. These compartments 701, 702 may be also considered as functionally different cartridges.

More particularly, in the microfluidic device 700, the further casing 702 is provided enclosing a further sample chamber. A further temperature controller 203 is located in a first portion 106 of the further casing 702 and is adapted for controlling a temperature of a fluidic sample 201 located in the further sample chamber. The turning mechanism 105 is adapted for turning the further casing 702 in a manner that the first portion 106 of the further casing 702 is converted from an upper portion of the further casing 702 (as shown in Fig. 7) into a lower portion of the further casing 702 (not shown in the figures), and a second portion 107 of the further casing 702 is converted from a lower portion of the further casing 702 (as shown in Fig. 7) into an upper portion of the further casing 702 (not shown in the figures). The device 700 comprises a common temperature reference unit 602 adapted for providing a predefined temperature reference and arranged between the first portion 106 of the casing 701 and the first portion 106 of the further casing 702. The described embodiment may enable flipping for enhanced throughput during thermal processing. In this embodiment, it is possible to flip a bio-cartridge 700 to enable thermal cycling of multiple bio-cartridge units 701, 702 simultaneously on a single temperature reference plate 602. This may be advantageous as it enables a higher throughput of bio-assays by an apparatus.

The temperature reference plate 602 is part of the analysis apparatus 700, i.e. not part of the bio-cartridge. Preferably, the bio-cartridge is in close thermal contact with the temperature reference plate 602 such that the side 106 of the bio-cartridge 701, 702 that comprises the heating elements 203 (for instance resistive heaters) is closest to the temperature reference plate 602. The temperature reference plate 602 may comprise metal. Preferably, the temperature reference plate 602 has a high thermal capacity with respect to a bio-cartridge 701, 702 to make it suitable to act as a temperature reference.

In the case where no homogeneous gas layer is present (i.e. system is open, expansion volume has been created elsewhere or the chamber is flexible and can expand) then another embodiment may be advantageous. In particular in such a case thermal cycling for DNA amplification (for instance PCR) can be carried out simultaneously in two cartridges using a single temperature reference plate 602 (see Fig. 7). Analogously, in another embodiment it allows to perform thermal cycling/control during a hybridisation assay. In a further embodiment, it allows to perform thermal cycling during DNA amplification in a cartridge, while performing thermal cycling/control during a hybridisation assay in another sample.

In an exemplary embodiment, the cartridge 700 is flipped inside an analysis apparatus (for instance bench-top machine) to enable simultaneous thermal processing of multiple cartridges 701, 702 using a single temperature reference plate 602. In the following, referring to Fig. 8, an analysis apparatus 800 according to an exemplary embodiment of the invention will be explained.

The analysis apparatus 800 comprises a first holder 801 for holding cartridges 803 after a processing procedure. Moreover, the analysis apparatus 800 comprises a second holder 802 for holding cartridges 803 before a processing procedure. For processing, individual cartridges 803 are taken from the second holder 802, are rotated around a rotation axis 804 and are sequentially supplied to a cell lysing unit 806, to a DNA extraction unit 807, to a DNA amplification unit 808, and to a sensor readout unit 809. Subsequently, the processed cartridges 803 are rotated around a rotation axis 805 and are sequentially supplied to the first holder 801. Thus, the embodiment of Fig. 8 shows flipping of a cartridge 803 in a read-out apparatus (bench-top analyser) 800. In this embodiment, a cartridge 803 is (partially) flipped in an apparatus 800 during the carrying out of a bioassay (or part of a bioassay) on that cartridge 803. This may be advantageous as it enables to perform in-line processing of cartridges 803 (with the benefit of high-throughput) using a limited space, due to which the dimensions of the apparatus 800 (for instance bench-top machine) can be restricted.

With in-line processing it may be particularly meant the sequential processing of cartridges 803 with overlap in the process steps i.e. such that processing of a subsequent cartridge 803 can be started before the total bioassay of the previous cartridge 803 is finished. For instance, when the biosensor (for instance micro-array) of a lab-on-a-chip is exposed to the fluid to be sampled (for instance in the hybridisation phase), it is possible to already begin sample processing, such as cell lysing, DNA extraction and PCR amplification on subsequent cartridges 803 before previous assays are complete (see Fig. 8). This way the throughput of an analysis system 800 is increased, such that ideally the analysis time per cartridge 803 is reduced from the total bioassay time to the time needed for the step that has the longest duration.

Although each step of the bioassay can be performed on the same cartridge 803, each step may require its own additional equipment, such as the fluorescence optical detection system, or a temperature reference plate. By splitting these functions in the bench- top apparatus 800, the in-line processing becomes possible.

In the case that space is limited within a system 800, a user may load a cartridge holder 802, which comprises multiple cartridges 803, underneath or on top of an analysis apparatus 800 such that flipping of a cartridge 803 inside the analysis apparatus 800 is required to enable proper processing. For instance, Fig. 8 illustrates the placing of multiple cartridges 803 underneath the analysis compartment 810 of an analysis apparatus 800, which is similar to the placing of paper underneath a printer. A method of taking a cartridge 803 out of the cartridge holder 802 may incorporate a flipping action.

In particular, also the embodiments of Fig. 1 to Fig. 7 may include flipping of a cartridge inside an analysis apparatus. It should be noted that the term "comprising" does not exclude other elements or features and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined.

It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

CLAIMS:

1. A micro fluidic device (100) for analysing a fluidic sample (201), the micro fluidic device (100) comprising a casing (101) enclosing a sample chamber; a turning mechanism (105) adapted for turning at least a part of the microfluidic device (100), particularly adapted for turning the casing (101).

2. The microfluidic device (100) of claim 1, wherein the casing (101) is completely closable or completely closed.

3. The microfluidic device (100) of claim 1, wherein the turning mechanism

(105) is adapted for turning the casing (101) in a manner that a first portion (106) of the casing (101) is converted from a lower portion of the casing (101) into an upper portion of the casing (101), and that a second portion (107) of the casing (101) is converted from an upper portion of the casing (101) into a lower portion of the casing (101).

4. The microfluidic device (100) of claim 3, comprising a temperature controller

(203) located in the first portion (106) of the casing (101) and adapted for controlling a temperature of the fluidic sample (201) located in the sample chamber.

5. The microfluidic device (700) of claim 4, comprising a further casing (702) enclosing a further sample chamber; comprising a further temperature controller (203) located in a first portion

(106) of the further casing (702) and adapted for controlling a temperature of a fluidic sample (201) located in the further sample chamber; wherein the turning mechanism (105) is adapted for turning the further casing

(702) in a manner that the first portion (106) of the further casing (702) is converted from an upper portion of the further casing (702) into a lower portion of the further casing (702), and that a second portion (107) of the further casing (702) is converted from a lower portion of the further casing (702) into an upper portion of the further casing (702); comprising a temperature reference unit (602) adapted for providing a predefined temperature reference and arranged between the first portion (106) of the casing (701) and the first portion (106) of the further casing (702).

6. The micro fluidic device (100) of claim 1, comprising a sensor-active structure

(204) located at a surface of a first portion (106) of the casing (101) in the sample chamber.

7. The microfluidic device (400) of claim 6, comprising a further sensor-active structure (204) located at a surface of the second portion (107) of the casing (101) in the sample chamber.

8. The microfluidic device (400) of claim 6, comprising a detection separation structure (401) between the first portion (106) of the casing (101) and the second portion (107) of the casing (101) for enabling a separate detection of a sensor event at the sensor- active structure (204) located at the surface of the first portion (106) of the casing (101) and of a sensor event at the further sensor-active structure (204) located at the surface of the second portion (107) of the casing (101).

9. The microfluidic device (100) of claim 4 or 6, comprising a barrier generation mechanism adapted for providing a barrier (202) in one of the group consisting of the upper portion of the sample chamber and the lower portion of the sample chamber to decouple the fluidic sample (201) from one of the group consisting of the lower portion of the sample chamber and the upper portion of the sample chamber.

10. The microfluidic device (400) of claim 1, comprising a detection unit (402 to

404), adapted for detecting a result of the analysis of the fluidic sample (201).

11. The microfluidic device (700) of claim 1, wherein the casing (701, 702) is configured to enclose a plurality of separate sample chambers.

12. A system for analysing a fluidic sample (201), the system comprising a microfluidic device (100) of claim 1 for analysing the fluidic sample (201); and an analysis device for performing an analysis using the microfluidic device (100).

13. The system of claim 12, wherein the turning mechanism (105) is adapted for turning the casing (101) relative to the analysis device.

14. The system of claim 12, wherein the turning mechanism (105) is adapted for turning both the casing (101) and the analysis device.

15. A method of operating a microfluidic device (100) for analysing a fluidic sample (201), the method comprising turning at least a part of the microfluidic device (100), particularly turning a casing (101) of the microfluidic device (100) enclosing a sample chamber.

16. The method of claim 15, comprising turning the casing (101) during a thermal treatment of the fluidic sample (201).