WO2010041214A1

WO2010041214A1 - Integrated microfluidic device

Info

Publication number: WO2010041214A1
Application number: PCT/IB2009/054422
Authority: WO
Inventors: Clemens J. M. Lasance; Marc W. G. Ponjee; Paul L. Collins; David A. Fish
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2008-10-10
Filing date: 2009-10-08
Publication date: 2010-04-15

Abstract

The present invention provides an integrated micro fluidic device (100) comprising a plurality of fluidic chambers (20) provided on a substrate (19), the plurality of fluidic chambers (20) being logically organized in rows and columns, each fluidic chamber (20) comprising a fluidic region (21), the area under the fluidic region (21) being divided into a plurality of segments (22), each segment (22) comprising a heater (23) integrated in the substrate (19), each heater (23) of each segment (22) being individually drivable. The device (100) furthermore comprises a plurality of temperature sensors (32) integrated in the substrate (19), each temperature sensor (32) being individually drivable. Furthermore, a control circuit is provided for individually driving the heaters (23) and temperature sensors (32), the control circuit being separated in location from the heaters (23). The present invention also provides a method for making such an integrated microfluidic device (100).

Description

Integrated micro fluidic device

TECHNICAL FIELD OF THE INVENTION

The present invention relates to micro fluidic devices. More particular, the present invention relates to an integrated micrfluidic device comprising segmented heating and sensing functions and to a method for manufacturing such an integrated microfluidic device.

BACKGROUND OF THE INVENTION

In the past decade a wide variety of bio-fluidic functions for total analysis systems has been reported using electrical actuation, such as, for example, droplet fluidics, gel based valves, micro-mechanical actuators for mixing/flow, on-chip PCR (polymerase chain reaction), (di)electrophoretic techniques and electric field based sensors. Despite these and other advances, the use of the vast arsenal of electrically driven bio-fluidic functions in diagnostic applications is so far limited, which is primarily due to the challenging system integration aspects such as cost-effectiveness, performance (speed, sensitivity, reliability) and ease-of-use (automatic control).

Lab-On-A-Chip (LOAC) systems are been actively considered in, for example, the detection of DNA sequences corresponding to certain diseases. Polymerase Chain Reaction (PCR) is a specific example of a technique that enables the amplification of DNA. This technique requires accurate cycled temperature steps to enable high efficiency amplification. The advantage of LOAC systems is that they reduce the bulky and time consuming equipment used in current laboratories.

LOAC systems will require both active drive, i.e. temperature controllers in the case of PCR, and micro-fluidic systems for moving and processing the various biological elements. There may also be system components external to the LOAC. Furthermore, the LOAC will often need to be a disposable element that fits into a fixed piece of equipment to perform its function.

Where LOAC systems used to be formed on Si substrates, nowadays, LOAC systems are also made on glass substrates and are then referred to as lab-on-glass (LOG) devices. Main advantages of LOG technology with respect to crystalline Si-based integration approaches is the natural fit of LOG with the need for electronics distributed over a relatively large area combined with the need for cost-effectiveness. Costs of LOG are more than 10- fold lower per cm² than crystalline Si. In addition, the transparent and biocompatible glass substrate puts fewer constraints on the cartridge and system design, e.g. the LOG technology can readily be applied in disposable devices that mainly consist of plastic.

A LOG device comprises a number of fluidic chambers 4 arranged in an array and electronic elements such as addressing elements 5 and heater means 6 inside each fluidic chamber 4, as illustrated in Fig. 1. A particular problem that arises in arbitrary LOG devices comprising heater means 6 is that whatever array size or configuration is used, each chamber sees a different thermal environment. For example, the corner chambers would see greater thermal losses compared to a chamber at the top centre or a chamber surrounded on all sides with other chambers. This may particular be a problem for heated micro-fluidic systems with ~ 10 μl fluid volumes, because the perimeter of the glass is a large proportion of each chamber dimension and the total number of chambers 4. Each fluidic chamber 4 may comprise a select line 7, a data line 8, an addressing element 5 and a heater means 6 such as an actuator. The array may comprise M rows and N columns. The larger M and N become, the more each fluidic chamber undergoes uniform heating. For a chamber with a 10 μl volume, the chamber dimensions are approximately 16 mm x 3 mm = 50 mm². With e.g. 20 fluidic chambers 4 on one substrate this requires a large glass substrate of approximately 1000 mm² for the fluidics regions alone. Therefore, it is not possible to improve the temperature uniformity by increasing the number of fluidic chambers 4 by an order of magnitude because there is no room for that and because this is not feasible in Point of Care (PoC) hand held devices.

SUMMARY OF THE INVENTION

It is an object of embodiments of the present invention to provide an integrated microfluidic device and a method for manufacturing such an integrated microfluidic device.

The above objective is accomplished by a method and device according to the present invention. According to a first aspect of the present invention, the integrated microfluidic device comprises: a plurality of fluidic chambers provided on a substrate, the plurality of fluidic chambers being logically organized in rows and columns, each fluidic chamber comprising a fluidic region, the area under the fluidic region being divided into a plurality of segments, each segment comprising a heater integrated in the substrate, each heater of each segment being individually drivable, a plurality of temperature sensors integrated in the substrate, each temperature sensor being individually drivable, each segment comprising a temperature sensor and - a control circuit for individually driving the heaters and temperature sensors, the control circuit being separated in location from the heaters.

An integrated microfluidic device according to the invention allows a uniform heating over the whole or a majority part of a substrate of the device, e.g. allows a uniform heating of all fluidic chambers of the integrated microfluidic device. This improves reproducibility of tests and experiments performed in the integrated microfluidic device. Preferably the control circuit comprises a number of addressing elements equal to the number of fluidic chambers, at least one row driver, and a column driver. Temperature uniformity in time and space has been created.

In an advantageous embodiment, the control circuit comprises a plurality of row drivers, there being one row driver for each of the fluidic chambers. Individual closed loop control of the heaters and the temperature sensors enables the desired temperature control with high uniformity and accuracy combined with fast heating rates.

The control circuit may comprise one major row drive for individually driving all heaters and temperature sensors of all fluidic chambers. Preferably the temperature sensors are formed by a pair of temperature elements. A differential temperature sensor approach offers the best performance. The temperature elements should be made from different materials and are located in close proximity to the heaters.

In order to obtain even better temperature uniformity the heaters may be formed of a main heater and a guard around the main heater. The guards are preferably of the same material as the heaters.

Preferably, each segment has a guard controlled by a temperature sensor. Preferably, a heat sink is formed at a side of the substrate opposite to the side on which the integrated microfluidic device is formed. The heat sink may be patterned. The material of the heat sink may be a metal foil. Preferably the metal foil has open areas positioned vertically below the chambers. Preferably the metal of the foil is positioned vertically below the drive circuits to provide there a fast cooling. Thermocycling is achieved by fixing the device with the patterned heath sink to a cooling block. The integrated microfluidic device according to the invention may be used for performing molecular diagnostics experiments.

In particular, the integrated microfluidic device according to the invention is suitable for performing polymerase chain reaction (PCR). According to another aspect of the invention, an integrated microfluidic diagnostic device comprises a controller for controlled driving of the integrated molecular diagnostics device, the controller comprising a control unit for controlled and individually driving heaters and temperature sensors of the integrated microfluidic device.

According to a second aspect of the invention, there is provided a method for manufacturing an integrated microfluidic device, the method comprising: providing a plurality of fluidic chambers on a substrate, the plurality of fluidic chambers being logically organized in rows and columns, each fluidic chamber comprising a fluidic region, the area under the fluidic region being divided into a plurality of segments, providing for each segment a heater integrated in the substrate, each heater of each segment being individually drivable, providing a plurality of temperature sensors integrated in the substrate, each temperature sensor being individually drivable, each segment being provided with a temperature sensor and providing a control circuit for individually driving the heaters and temperature sensors, the control circuit being separated in location from the heaters.

Preferably a heat sink is formed at a side of the substrate opposite to the side on which the integrated microfluidic device is formed. The heat sink may be patterned. The material of the heat sink may be a metal foil. The metal foil has open areas positioned vertically below the chambers. The metal of the foil is positioned vertically below the drive circuits to provide there a fast cooling.

Preferably a heater is formed of electrically conductive, preferably optically transparent material such as indium-tin-oxide (ITO). The heater may be formed of a main heater and a guard around the main heater. Preferably the main heater and the guard are of the same material. Preferably a temperature sensor is formed by providing a pair of temperature elements. The temperature elements are formed of different material.

The above objective is accomplished by a method and device according to the present invention. Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims. The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an example of an arbitrary array of fluidic chambers according to prior art.

Fig. 2 schematically illustrates the principle of segmented heating according to embo diments o f the invention.

Fig. 3 a passive array of fluidic chambers with integrated heaters.

Fig. 4 illustrates part of an integrated microfluidic device according to embodiments of the invention.

Fig. 5 illustrates one fluidic chamber of an integrated microfluidic device according to embodiments of the invention.

Fig. 6 illustrates an integrated microfluidic device according to embodiments of the invention.

Fig. 7 illustrates an example of an addressing element which can be used with an integrated microfluidic device according to embodiments of the invention. Fig. 8 illustrates drive electronics for the addressing elements which can be used with an integrated microfluidic device according to embodiments of the invention.

Fig. 9 illustrates temperature sensor layout within a fluidic chamber according to embodiments of the present invention.

Fig. 10 illustrates a temperature sensor selection circuit which can be used with an integrated microfluidic device according to embodiments of the invention.

Fig. 11 illustrates full chamber layouts for a 60V chamber layout (left side) and for a 100V chamber layout (right side).

Fig. 12 schematically shows an integrated microfluidic device according to embodiments of the invention. Fig. 13 schematically illustrates a 60V chamber layout (right side) and a 100V chamber layout (left side) for integrated microfluidic devices according to embodiments of the invention.

Fig. 14 a) shows an embodiment of an integrated heater, b) Schematic layout of a chamber with the integrated heater, the heater being formed of a main heater and a guard around the main heater, c) Situation without guard, left: Z-plane, right: Y-plane, as indicated, d) shows the same situation as c) after powering the guard.

Fig. 15 illustrates a fluidic chamber with temperature non-uniformity and high circuit temperatures. Fig. 16 schematically shows an integrated microfluidic device according to embodiments of the invention.

Fig. 17 gives the thermal simulations of a single chamber operating at its maximum power output, a) 20 μm air gap under chamber (white circle) and b) 20 μm air gap under chamber (white circle), and 20 μm metal under the chamber positioned under the drive circuits.

Fig. 18 schematically illustrates a system controller for use with an integrated microfluidic device according to embodiments of the present invention.

In the different figures, the same reference signs refer to the same or analogous elements.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. Any reference signs in the claims shall not be construed as limiting the scope. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.

Where the term "comprising" is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated.

Furthermore, the terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a computer system or by other means of carrying out the function. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention. In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. The present invention provides an integrated microfluidic device which solves the problem of non-uniform heating of different fluidic chambers present on a same substrate and to a method for manufacturing such an integrated microfluidic device. The microfluidic device comprises a plurality of fluidic chambers provided on a substrate. For solving the problem of non-uniform heating it was recognized by the inventors that a segmented heating structure is required for each fluidic chamber on the substrate, with individual control of each segment to optimize and adjust the temperature profile. This creates potential issues for the design of the device and for the necessary drive electronics.

A schematic illustration of a possible implementation of such a segmented heating structure for a fluidic chamber 10 is shown in Fig. 2. The fluidic chamber 10 comprises a fluidic area or fluidic region 11. Under the fluidic area 11 a heater is provided which is divided into heater segments 12. For each heater segment 12 furthermore a temperature sensor 13 is provided. The design shown in Fig. 2 was, however, found to have several design issues when using this approach:

Row lines or address lines Addr 1 to Addr N for addressing each heater segment 12 go through each chamber 10. This fills the chamber area with address lines, power lines and ground lines (the latter two are not shown in Fig. 2 for clarity). This will block radiation e.g. used during luminescence, e.g. florescence detection during quantitative PCR (polymer chain fluidic), thereby reducing the detection sensitivity of the chamber array. Sensing is required at key locations in the chamber 10, such as e.g. the border. The temperature sensor 13 cannot be placed at the same layer as the heater means, e.g. heater resistor, because this creates a gap in the heating area, thereby introducing non-uniformity in heating and sensing, especially on areas larger than 20 μm x 20 μm.

A differential temperature sensor approach, i.e. a temperature sensor 13 for each of the heater segments 12, offers the best performance, however these must be made from different materials and located in close proximity to prevent any temperature offset, this cannot be achieved in passive 1 or 2 metal layer fabrication processes, as the they must be stacked onto of one another, and the heater material and existing sensors 13 are using these metal layers. As used in the topology of an active matrix display, each heater segment 12 has a row line Addr 1 to Addr N, a column line 15, and a TFT which acts as an addressing element 14. The addressing element 14 for each heater segment 12 is very large (for power efficiency) and complex (for digital, PWM addressing in LTPS which removes device variations) (see further). This means it cannot be located inside each segment as it will block light used during luminescence, e.g. florescence detection during quantitative PCR (polymer chain fluidic), thereby reducing the detection sensitivity of the chamber array.

For a simple chamber array, it is possible to design it like a passive display (see Fig. 3 which shows an example of a passive array of chambers with integrated heater means). However, due to the number of segments, it is not feasible to have complete external heater control like a passive AMLCD (active matrix liquid crystal display design), i.e. the row driver and column driver are located outside the pixel array or off the glass substrate and not each pixel has an addressing element. The passive approach would require too many connections, i.e. 9 segments, 2 tracks per segments, so that 20 fluidic chambers requires 360 tracks. The passive design would also need long thick track lengths to the heaters, reducing the heater efficiency and consume large amounts of area.

Summarizing, when a large number of fluidic chambers 10 is required it is not practical with a passive matrix technology, due to: the number of connections required, - the heater and sensor arrangement, causing heating and/or sensing errors, and reduced luminescence, e.g. fluorescence efficiency due to the number and thickness of the tracks.

Therefore, the present invention uses an active matrix system. In that case the high mobility of Low Temperature Poly Silicon (LTPS) may be suitable because: - complexity of the addressing element (digital addressing), the power efficiency required by the addressing element (consumes less area), can integrate the row driver, if yield is not affected.

Because of the above, the present invention provides in a first aspect an integrated micro fluidic device comprising: - a plurality of fluidic chambers provided on a substrate, the plurality of fluidic chambers being logically organized in rows and columns each fluidic chamber comprising a fluidic region, the area under the fluidic region being divided into a plurality of segments, each segment comprising a heater integrated on the substrate, each heater of each segment being individually drivable, a plurality of temperature sensors integrated on the substrate, each temperature sensor being individually drivable, each segment comprising a temperature sensor and a control circuit for individually driving the heaters and temperature sensors, the control circuit being separated in location from the heaters. An integrated micro fluidic device according to embodiments of the invention allows a uniform heating over the whole substrate of the device, i.e. allows a uniform heating of all fluidic chambers of the integrated micro fluidic device. This improves reproducibility of tests and experiments performed in the integrated microfluidic device.

Fig. 4 to Fig. 6 illustrate the principle of an integrated microfluidic device 100 according to embodiments of the present invention.

Fig. 4 schematically illustrates part of an integrated microfluidic device 100 according to embodiments of the invention. The integrated microfluidic device 100 comprises a plurality of fluidic chambers 20 with integrated heating and sensing functions. The plurality of fluidic chambers 20 are logically organized in rows and columns. Throughout this description, the terms "column" and "row" are used to describe sets of array elements which are linked together. The linking can be in the form of a Cartesian array of rows and columns however the present invention is not limited thereto. As will be understood by those skilled in the art, columns and rows can be easily interchanged and it is intended in this disclosure that these terms be interchangeable. Also, non-Cartesian arrays may be constructed and are included within the scope of the invention. Accordingly the terms "row" and "column" should be interpreted widely. To facilitate in this wide interpretation, the claims refer to logically organized rows and columns. By this is meant that the plurality of fluidic chambers are linked together in a topologically linear intersecting manner; however, that the physical or topographical arrangement need not be so. For example, the rows may be circles and the columns radii of these circles and the circles and radii are described in this invention as "logically organized" rows and columns. Also, specific names of the various lines, e.g. reset line and first and second select line, are intended to be generic names used to facilitate the explanation and to refer to a particular function and this specific choice of words is not intended to in any way limit the invention. It should be understood that all these terms are used only to facilitate a better understanding of the specific structure being described, and are in no way intended to limit the invention.

The plurality of fluidic chambers 20 is formed on a substrate 19. According to embodiments of the invention, the substrate 19 may be any electrical insulating layer being optically transparent, such as a glass substrate. Using a glass substrate offers significant optical, large-area and cost advantages from conventional LOAC systems on silicon or metal. However, glass substrates have a lower thermal conductivity and this can create problems when power is dissipated in unwanted areas on the substrate.

Fig. 5 shows one fluidic chamber 20 of the device 100. Each of the fluidic chambers 20 comprises a fluidic region 21, also referred to as fluidic area, at which reaction or experiments are to be performed. The area underneath the fluidic region 21 is divided into a plurality of segments 22. Each segment 22 is provided with a heater 23. This is for obtaining a required heating rate within the fluidic chamber 20. According to embodiments of the invention the heaters 23 may be in the form of a series of resistors, as is illustrated in Fig. 10. The heaters 23 of each of the segments 22 are individually drivable.

The integrated micro fluidic device 100 also comprises a plurality of temperature sensors 32 (see for example Fig 9 or Fig. 10), each segment 22 comprising a temperature sensor. According to embodiments of the invention, the temperature sensors may comprise Ti and TiN. The number of temperature sensors per chamber depends on many parameters and is subject to optimization.

Furthermore, the integrated micro fluidic device 100 comprises a control circuit for individually driving the heaters 23 and temperature sensors, the control circuit being separated in location from the heaters 23. This can be clearly seen from Fig. 5. The control circuit may comprise a number of addressing elements 24 equal to the number of fluidic chambers 20, at least one row driver 25, and a column driver 26. The control circuit furthermore comprises row select lines 27 and column lines or data lines 28.

The addressing element 24 for each segment 22 can be very large (for power efficiency) and complex (for digital, PWM addressing in LTPS which removes device variations). Therefore, according to embodiments of the present invention, the control circuit, and especially the addressing elements 24, are separated in location from the heaters 23, thereby maximizing the transparency of the segment 22 to improve luminescence, e.g. florescence efficiency, as normally the heating element is made out of ITO, a transparent metal conducting layer. The addressing elements 24 generate a required signal when addressed, including level shift signals, buffers and signals for driving the heaters 23. The addressing elements 24 are collected together near the heaters 23 but outside the fluidic region 21, thereby minimizing track distances, as can be seen from Fig. 5. Hence, according to embodiments of the present invention, the control circuit comprising a.o. the addressing elements 24 is separated in location from the heaters 23. However row lines 27 are still to be supplied to each of the addressing elements 24. The required number of row lines 27 can be very high and can consequently take up valuable glass area and foil connections.

According to embodiments of the invention, the control circuit may comprise a row driver 25 for each fluidic chamber 20, thereby treating each chamber 20 as if it is a mini display. According to other embodiments, however, the control circuit may comprise one master row driver stage 25 that supplies each fluidic chamber 20 with the addressing signals. The latter is illustrated in Fig. 6 for an integrated molecular diagnostics device 100 according to embodiments of the invention. The integrated molecular diagnostics device 100 illustrated in Fig. 6 comprises two rows of fluidic chambers 20. The row lines 27 are routed around the fluidic chamber 20 to prevent entering the fluidic regions 21. This may be an advantage because it does not provide interference with tests or reactions being performed in each of the fluidic chambers 20.

Fig. 7 illustrates in detail an example of an addressing element 24 which can be used with an integrated micro fluidic device 100 according to embodiments of the invention to address the heaters 23 of each of the segments 20. The row select lines 27 (ckl and ck2) are not generated on the glass substrate 19 but supplied externally to prevent any potential yield issues. The data input can be considered as a column, and the Ramp input is wired into the array like a row line. The addressing element 24 may comprise a comparator 29, in the example given a three-stage comparator, a level shifter 30 to higher voltages and high voltage drive transistors 31.

Fig. 8 shows a final layout for the addressing elements 24 which may be used in an integrated micro fluidic device 100 according to embodiments of the invention, both for a design having ten fluidic chambers 20, also referred to as a 60V chamber design (left hand side) and for a design having twenty fluidic chambers 20, also referred to as a 100V chamber design (right hand side).

Fig. 9 illustrates a possible layout for the temperature sensors 32 and the positioning of the temperature sensors 32 within each fluidic chamber 20. The temperature sensors 32 may be formed of pairs of temperature sensor elements 32a and 32b. A first temperature sensor element 32a may, according to embodiments of the invention, for example be formed of a strip of Ti wrapped into a square with a width of e.g. 10 μm and a space of e.g. 10 μm in between wraps with 15 Ω/μm² resistivity and lOkΩ will occupy an area of 0.126 mm² = a square of approximately 360 μm x 350 μm. The second temperature sensor element 32b may, for example, comprise a strip of TiN wrapped into a square with width 10 μm and space 10 μm in between raps with 25 Ω/μm² and lOkΩ will occupy an area of 0.075 mm² = a square of approximately 277 μm x 270 μm. The first temperature sensor element 32a formed of Ti was electrically connected to the first metal Ml. Connection to the TiN layer was made with the first metal layer Ml, but in addition electrical connections down to GE (gate electrode) metal were made to ensure good contact. Fig. 10 illustrates a selection circuit 40 for driving the temperature sensors 32 according to an embodiment of the present invention. The selection circuit may comprise nine sensor select row lines 33 and five column signals 34, i.e. TiN (2^nd temperature sensor element) voltage monitor column 34a, Ti (1^st temperature sensor element) voltage monitor column 34b, sensor voltage monitor column 34c, TiN (2^nd temperature sensor element) current column 34d and Ti (1^st temperature sensor element) current column 34e. The selection circuit may furthermore comprise a TiN (2^nd temperature sensor element) current path 35 and a Ti (1^st temperature sensor element) current path 36.

Fig. 11 shows a full chamber layout, i.e. a fluidic chamber as schematically illustrated in Fig. 5 together with drive electronics, according to embodiments of the invention both for a design having ten fluidic chambers 20, also referred to as a 60V chamber design (left hand side) and for a design having twenty fluidic chambers 20, also referred to as a 100V chamber design (right hand side). The high voltage circuitry has been disclosed in a corresponding European patent application 08156962.6 (priority date 27-05-2008) and is incorporated here by reference. Fig. 12 show a full layout of an integrated microfluidic device 100 according to an embodiment of the invention for a design having twenty fluidic chambers 20, also referred to as a 100V chamber design. Each fluidic chamber 20 is wired together in series as can be seen from Fig. 12. This drawing shows the number of connections required by all twenty fluidic chambers 20, with some connections made at both left and right sides of the array of fluidic chambers 20 to reduce power and line resistance. The layout may comprise eighteen clock inputs 37, nine ramp inputs 38, ten data inputs 33, fifty sensor inputs and outputs 41 and nine sensor select lines 33. Bottom and top chamber connections are the same. Fig. 13 shows a final layout and size for an integrated microfluidic device 100 according to an embodiment of the invention for a design having twenty fluidic chambers 20, also referred to as a 100V chamber design (left side of Fig. 13) and for a design having ten fluidic chambers 20, also referred to as a 60V chamber design (right side of Fig. 13). The 100V design may, for example, have a length L of 88 mm and a width W of 67.5 mm. The 60V design may, for example, have a length L of 52 mm and a width W of 66.5 mm. The integrated micro fluidic device 100 according to embodiments of the invention may be used in molecular diagnostics experiments such as e.g. biotechnical applications where controlled heating provides functional capabilities such as mixing dissolution of solid reagents, lysing, thermal denaturation of proteins and nucleic acids and lysis of cells, elution of bound molecules, enhanced diffusion rates of molecules in a sample, and modification of surface binding coefficients.

A prime example of such a functional capability, that requires reproducible and accurate temperature control, is high efficiency thermal cycling for DNA amplification using polymerase chain reaction (PCR) and ligase chain reaction (LCR). A number of other reactions, including isothermal DNA amplification techniques, ligand binding, enzymatic reactions, extension, transcription and hybridization reactions are also generally carried out at optimized, controlled temperatures. In addition, temperature control is of importance for drug discovery, where large numbers of candidate drugs have to be tested against reactivity. Furthermore, temperature control is essential to operate pumps and reversible/irreversible valves that are thermally actuated. Thermal expansion valves may include a sealed pressure chamber bounded by a diaphragm, or include a bubble valve. Thermally actuated pumps may use induced thermal gradients or the thermo capillary effect to pump fluid.

Rapid heat transfer and temperature uniformity are crucial for efficiently performing PCR and this makes temperature control one of the most essential features in a PCR system. PCR is a temperature controlled and enzyme-mediated amplification technique for nucleic acid molecules, usually consisting of 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.

Miniaturization of conventional PCR devices brings in great saving in space, sample and reagent consumption, automation and high throughput, and accelerates the amplification process by increasing the surface to volume ratio. Moreover, introduction of PCR on a miniaturized device such as a lab-on-a-chip, e.g. an integrated molecular diagnostics device as described above in embodiment of the present invention, brings the point of diagnosis to the point of care, and with that increases the speed of diagnosis, which saves lives and reduces costs. In order to achieve a required heating rate within a PCR chamber, the integrated micro fluidic device 100 comprises segments with heaters 23 located underneath the fluidic areas 21, as was described above. Power may, according to embodiments of the invention, be dissipated in the form of a series of resistors, e.g. thin film resistors. Other regions of a LOAC device may also require thermal cycling such as e.g. a thermo -pneumatic valve or flow rate sensor, which may also use a resistor or resistive device elements. Provided enough space is available to ensure one-dimensional heat transfer, no problems are to be expected regarding the temperature uniformity of the fluidic chamber 20. Unfortunately, to ensure a maximum efficiency the space available per chamber 20 has to be minimized leading to heat leakage and cross-talk which in the case of PCR will result in poor or non-specific DNA amplification.

Considering an array of fluidic chambers 20 as, for example illustrated in Fig. 6, Fig. 12 or Fig. 13 the worst case situation from a thermal point of view is the one where one fluidic chamber 20 is operational while all of its neighboring fluidic chambers 20 are not. Simulations show clearly that in order to maintain a certain required temperature uniformity in space and time the heaters 23 should extend quite a bit beyond the space occupied by the fluidic chamber 20, which results in significantly less useful area.

The heaters can be further improved to alleviate the temperature non- uniformity caused by heat leakage along a rim of the heater. Therefore, embodiments of the invention provide a way to overcome this problem by adding a small region around a central or main heater 23a, also referred to as a guard 23b, of which the temperature can be controlled independently from the main heater 23 a in such a way that the heat losses in the lateral direction are minimized. This is illustrated in Fig. 14.

Fig. 14a shows a schematic of a fluidic chamber 20, a heater comprising a main heater and a guard, a fluid inside the chamber, a wall and a top layer. The top layer can be a glass or polystyrene. The material of the walls may be SU8 or PET. The substrate may be glass polystyrene or another plastic material or a foil.

Fig. 14 b shows the layout of the cell used for the simulation, quarter symmetry, also indicating the planes for which the temperatures are shown. In this example the guard comprises 3 segments. The material of the guard is preferably the same as the material of the main heater. In this example the width of the guard is 0.5 mm and the thickness is 0.5 mm.

Fig. 14c shows a temperature plot after 25 s of starting an imposed heat flux profile revealing clearly the temperature non-uniformity caused by heat leakage along the rim of the heater. The highest temperature in the centre just above the heater is Ti= 90.15 ⁰C, while the lowest temperature OfT₂= 67.03 ⁰C is in the lower right corner.

Fig. 14d shows the same situation after powering the guard. It has been shown, that when driving the guard together with the main heater, heat losses can significantly be reduced. In this example the highest temperature in the centre just above the heater is Ti= 103.8 ⁰C, while the lowest temperature of T₂= 103.7 ⁰C is in the lower right corner. Due to the guard, the temperature difference ΔT_li2=0.1 ⁰C.

According to this embodiment, heat losses are minimized such that temperature uniformity on a LOAC can be achieved with high spatial resolution. Power may, according to embodiments of the invention, be dissipated in the form of a series of resistors, e.g. thin film resistors. Other regions of a LOAC device may also require thermal cycling such as e.g. a thermo -pneumatic valve or flow rate sensor, which may also use a resistor or resistive device elements.

Since much of the area in a LOAC device can be taken up by the fluidic regions 21, the active electronics must fit into the remaining space. This can cause track lengths to become bottlenecked in places and transistors to be squeezed into a small area. In these locations the power dissipation can result in temperatures violating performance and reliability requirements. This may causes two problems:

The temperature uniformity of designed regions can be upset, which in the case of PCR will result in poor or non-specific DNA amplification. This is shown in the temperature plots in Fig. 15.

High temperatures in the drive circuitry causes carrier charge injection into the device's channel region, this shifts the threshold voltage of the active devices making them appear more resistive, when this occurs the device is at risk of dissipating more power and becoming unstable (=thermal runaway). In addition high temperatures compounded with high voltages can also cause instabilities in the TFTs (thin film transistors).

Furthermore, this issue becomes a major reason why low voltage PCR is not yet possible, as higher currents are required (equation (I)) and as can be seen from equation (2) below the power lost within the transistors and other resistive elements increases with the square of the current.

Power = I x V (1)

Power = I²R = V²/ R. (2) In order to ensure that the temperature uniformity is maintained and active devices are not damaged, a good thermal contact can draw away the power and ensure lower temperatures inside circuit regions. However a good thermal contact can also draw away heat from the areas where relatively high temperatures are required, which may result in the overall system consuming much more power than necessary and loose the advantage of the glass being less thermal conductive. On the other hand, a certain 'goodness' of thermal contact is required to ensure a specified cooling rate. In summary, a 3D optimization is needed to construct the pattern in terms of size and thickness. According to embodiments of the invention, the integrated microfluidic device

100 may furthermore comprise a heat sink (see Fig. 16). The heat sink may be provided on the substrate at a side opposite to the side where the integrated molecular diagnostics device is formed. According to embodiments of the invention, the heat sink may be formed of a metal foil. The metal foil may have a thickness of, for example, between 10 μm and 100 μm. The metal foil allows thermal controlled heat sinking.

By, according to embodiments of the invention, patterning the heat sink, e.g. metal foil, such that it only makes contact where necessary, the high temperatures that occur from unwanted power dissipation can be reduced. This may prevent possible damage of the driver circuit of the device 100 and errors in temperature accuracy. Moreover, by patterning the heat sink, air or plastic filled cut-out regions may be formed which will allow higher temperatures where required for a lower overall power density. The thermal cycling required by many Lab-on-a-chip devices are all high power, and any method to reduce this maximum power will enable portable equipment that can operate from batteries. If this feature is combined with active cooling methods as known by a person skilled in the art a fast cooling rate can also be maintained.

Fig. 16 (left side) shows a layout of a twenty chamber Multiplex PCR lab-on- a-chip device 100. The fluidic chambers 20 may, according to the present example, have dimensions of 23 mm x 4 mm carrying a fluid volume of 10-25 μL each. Each fluidic chamber 20 will consume 10 W of power to create a uniform temperature of 100⁰C, which makes the whole system require 200 W of power. This is beyond the limits of any portable handheld device and is comparable in power required by a light bulb. Reducing this power can be achieved by using a heat sink structure as illustrated in the right part of Fig. 16. This diagram shows a patterned metal foil 42, attached to the underside of the glass substrate 19 and comprising cut-out regions 43. These cut-out regions 43 may also be useful to maintain a transparent optical substrate 19 underneath fluidic regions 21 for, e.g. a label based luminescent, e.g. fluorescent system. It has been shown that by, according to the present embodiment of the invention, patterning the heat sink 42 as described above, temperature of the drive circuitry 44 can, in the example given below, be reduced by about 26°C. Fig. 17 gives the thermal simulations of a chamber operating at its maximum power output. Fig. 17a shows the temperature of the chamber and drive circuits are approaching ~100°C and 88⁰C respectively with a uniform 20 μm air gap under the glass substrate. Fig. 17b shows the same power dissipation but with an air gap of 20 μm under the single chamber and a 2mm wide 20μm thick metal foil under the chamber, located vertically below the drive circuits. A comparison of the temperatures shows that the drive circuit temperatures can be reduced by 26⁰C because of the additional heat sink structure. Further optimization could be made to improve this further.

It has to be noted that the integrated molecular diagnostics device 100 according to embodiments of the invention and as described above can, besides being used for PCR, also be used for thermal cycling in thermo -pneumatic valves/pumps, blood gas analysis, flow rate sensing and other similar LOAC functions known by a person skilled in the art.

In a second aspect, the present invention provides a method for manufacturing an integrated micro fluidic device 100. The method comprising: - providing a plurality of fluidic chambers 20 on a substrate 19, the plurality of fluidic chambers 20 being logically organized in rows and columns, each fluidic chamber 20 comprising a fluidic region 21, the area under the fluidic region 21 being divided into a plurality of segments 22, providing for each segment 22 a heater 23 integrated in the substrate 19, each heater 23 of each segment 22 being individually drivable, providing a plurality of temperature sensors 32 integrated in the substrate 19, each temperature sensor 32 being individually drivable, and providing a control circuit for individually driving the heaters 23 and temperature sensors 32, the control circuit being separated in location from the heaters 23. According to embodiments of the invention, the method may furthermore comprise providing a heat sink. The heat sink may be provided on the substrate 19 at a side opposite to the side where the integrated microfluidic device 100 is formed. Providing a heat sink may be performed by providing a metal foil. According to embodiments of the invention, the heat sink may be patterned. By patterning the heat sink, cut-out regions 43 may be formed in the heat sink, thereby significantly reducing drive circuit temperatures.

According to embodiments of the invention, providing a heater 23 may be performed by providing a heater 23 comprising a main heater 23 a and a guard 23b around the main heater. In that way, heat losses can significantly be reduced during operation of the integrated micro fluidic device 100.

Providing a temperature sensor 32 may be performed by providing a pair of temperature elements, e.g. a first and second temperature sensor element 32a, 32b. According to embodiments, the first and second temperature sensor elements 32a, 32b may be formed of a different material, e.g. the first temperature element 32a may be formed of Ti while the second temperature sensor element 32b may be formed of TiN.

To achieve a required heating rate within a PCR chamber, power is dissipated in the form of a series of resistors located underneath the fluidic areas. Thermocycling is achieved by fixing the disposable to a cooling block. The heating ramp is typically 15K/s, the cooling ramp is typically 20 K/s. The heaters are simply switched off during the cooling ramp (duration e.g. 2 s.).

Other regions of a LOAC device may also require thermal cycling such as a thermo -pneumatic valve or flow rate sensor, these would also use a resistor or resistive device elements.

In a further aspect, the present invention also provides a system controller 50 for controlled driving of an integrated micro fluidic device 100 according to embodiments of the present invention as shown in Fig. 18. The system controller 50 according to the present aspect may comprise a control unit 51 for controlled and individually driving heaters 23 and temperature sensors 32 of the integrated microfluidic device 100. It is clear for a person skilled in the art that the system controller 50 may comprise other control units for controlling other parts of the integrated molecular diagnostics device 100; however, such other control units are not illustrated in Fig. 18.

The system controller 50 may include a computing device, e.g. microprocessor, for instance it may be a micro-controller. In particular, it may include a programmable controller, for instance a programmable digital logic device such as a Programmable Array Logic (PAL), a Programmable Logic Array, a Programmable Gate Array, especially a Field Programmable Gate Array (FPGA). The use of an FPGA allows subsequent programming of the integrated microfluidic device 100, e.g. by downloading the required settings of the FPGA. The system controller 50 may be operated in accordance with settable parameters.

It is to be understood that although preferred embodiments, specific constructions and configurations, as well as materials, have been discussed herein for devices according to the present invention, various changes or modifications in form and detail may be made without departing from the scope of this invention as defined by the appended claims.

Claims

CLAIMS:

1. An integrated microfluidic device (100) comprising: a plurality of fluidic chambers (20) provided on a substrate (19), the plurality of fluidic chambers (20) being logically organized in rows and columns, each fluidic chamber (20) comprising a fluidic region (21), the area under the fluidic region (21) being divided into a plurality of segments (22), each segment (22) comprising a heater (23) integrated in the substrate (19), each heater (23) of each segment (22) being individually drivable, a plurality of temperature sensors (32) integrated in the substrate (19), each temperature sensor (32) being individually drivable, each segment comprising a temperature sensor (32) and - a control circuit for individually driving the heaters (23) and temperature sensors (32), the control circuit being separated in location from the heaters (23).

2. An integrated microfluidic device (100) according to claim 1, wherein the control circuit comprises: - a number of addressing at least one row driver (25), and a column driver (26).

3. An integrated microfluidic device (100) according to claim 2, wherein the control circuit comprises a plurality of row drivers (25), there being one row driver (25) for each of the fluidic chambers (20).

4. An integrated microfluidic device (100) according to claim 2, wherein the control circuit comprises one major row driver (25) for individually driving all heaters (23) and temperature sensors (32) of all fluidic chambers (20).

5. An integrated microfluidic device (100) according to any of the previous claims, wherein the temperature sensors (32) are formed by a pair of temperature elements (32a, 32b).

6. An integrated microfluidic device (100) according to any of the previous claims, wherein the heaters (23) are formed of a main heater (23a) and a guard (23b) around the main heater.

7. An integrated microfluidic device (100) according to claim 6, wherein each segment (22) has a guard (23b) controlled by a temperature sensor (32).

8. An integrated microfluidic device (100) according to any of the previous claims, furthermore comprising a heat sink (42) at a side of the substrate opposite to the side on which the integrated microfluidic device is formed.

9. An integrated microfluidic device (100) according to claim 8, wherein the heat sink (42) is patterned.

10. Use of the integrated microfluidic device (100) according to any of the previous claims for performing molecular diagnostics experiments.

11. Use of the integrated microfluidic device (100) according to any claims 1 to 9 for performing polymerase chain fluidic experiments.

12. Method for manufacturing an integrated microfluidic device (100), the method comprising: providing a plurality of fluidic chambers (20) on a substrate (19), the plurality of fluidic chambers (20) being logically organized in rows and columns, each fluidic chamber (20) comprising a fluidic region (21), the area under the fluidic region (21) being divided into a plurality of segments (22), providing for each segment (22) a heater (23) integrated in the substrate (19), each heater (23) of each segment (22) being individually drivable, - providing a plurality of temperature sensors (32) integrated in the substrate

(19), each temperature sensor (32) being individually drivable, each segment being provided with a temperature sensor (32) and providing a control circuit for individually driving the heaters (23) and temperature sensors (32), the control circuit being separated in location from the heaters (23).

13. Method according to claim 12, wherein the method furthermore comprises providing a heat sink.

14. Method according to claim 12 or 13, wherein providing a heater (23) is performed by providing a heater comprising a main heater and a guard (23b) around the main heater (23 a).

15. Method according to any of claims 12 to 14 wherein providing a temperature sensor is performed by providing a pair of temperature elements.

16. Controller for controlled driving of an integrated micro fluidic device (100), the controller comprising a control unit for controlled and individually driving heaters (23) and temperature sensors (32) of the integrated microfluidic device (100).