heater

Abstract

A heater for thermal cycling to perform PCR amplification, comprising a heat spreading layer having a reaction surface for transferring heat to a reaction cell, a heater track support layer having a cooling backside, an electrically conductive main heater track supported between the heater track support layer and the heat spreading layer, and four-terminal electrical contacts to the main heater track adapted to provide electrical connections for driving the main heater track and simultaneously detecting the resistance of the main heater track. The lateral dimensions of the reaction surface are greater than the heater thickness H, such that the area of ​​the reaction surface A>H 2 is.

Description

[Technical Field]

[0001] The present invention relates to a heater for providing a variable temperature to a reactive surface of the heater. [Background technology]

[0002] One exemplary process in which such a heater is needed is DNA amplification by polymerase chain reaction (PCR), where the heater provides rapid thermal cycling to reduce the completion time of the PCR.

[0003] Prior art heaters are fabricated from conductive tracks supported by an electrically insulating substrate and are controlled using a separate temperature sensor to detect the heater temperature and a control algorithm and electronic drive circuit to modulate the electrical drive to the heater.

[0004] To provide a fast thermal response, the heater must have a low thermal mass and must be in intimate thermal contact with the reaction surface. Specifically, the heat diffusion time from the heater element to the reaction surface must be shorter than the required temperature change response time, and therefore only a thin layer can separate the heater and the reaction surface.

[0005] Conventional heater and temperature control systems have several drawbacks when attempting to achieve fast response, precise temperature control and uniform temperature distribution.

[0006] For example, using a temperature sensor that is separate from the heater introduces delays in the heater control loop that can slow response speed or cause temperature overshoot.

[0007] Furthermore, heat generation within spatially separated resistive heating tracks positioned near the reaction surface results in temperature non-uniformity, with hotter regions directly above the heater tracks and cooler regions above the gaps between the heater tracks. Temperature non-uniformity on the reaction surface can reduce the efficiency and specificity of PCR amplification, and is therefore undesirable. Therefore, an object of the present invention is to increase temperature uniformity, where references to improved temperature uniformity and increased temperature uniformity are equivalent.

[0008] Temperature non-uniformity at the reaction surface can be reduced by using narrower tracks and gaps, but this complicates manufacturing using standard printed circuit board techniques. Temperature non-uniformity at the reaction surface can also be reduced by increasing the distance between the heater tracks and the reaction surface, but this increases the heat diffusion time from the heater to the reaction surface and slows the heater response.

[0009] Temperature nonuniformities can also be caused by edge effects, where the heater temperature drops at the edges due to lateral heat flow. In the prior art, edge effects are reduced by heater track pattern design that increases the heat output near the heater edges, for example, by reducing the track and gap widths of the heater elements in these areas. However, this approach must be carefully designed for the specific operating temperature and reaction surface geometry and heat load, and can be difficult to achieve when the heater track and gap widths are already close to the minimum practical for standard manufacturing processes. Furthermore, to minimize temperature nonuniformities, it is desirable to minimize the heater track and gap widths even in the central area of ​​the heater; therefore, further reducing the heater track and gap widths near the heater edges is difficult. Summary of the Invention [Problem to be solved by the invention]

[0010] To allow for rapid cooling when heater power is reduced, heaters are sometimes connected to a heat sink via a controlled thermal resistance. However, the temperature uniformity of the heater depends on the uniformity of the thermal contact between the heater and the heat sink. In particular, any air gap between the heater and the heat sink can cause significant thermal resistance and temperature non-uniformity. [Means for solving the problem]

[0011] In view of the above problems and objects, the present invention provides a heater for thermal cycling for performing PCR amplification. The heater comprises a heat spreading layer having a reaction surface for transferring heat to a reaction cell, a heater track support layer having a cooling back surface, an electrically conductive main heater track supported between the heater track support layer and the heat spreading layer, and four-terminal electrical contacts to the main heater track adapted to provide electrical connections for driving the main heater track and simultaneously detecting the resistance of the main heater track. The lateral dimensions of the reaction surface are greater than the heater thickness H, so that the area of ​​the reaction surface A>H 2 is.

[0012] Preferably, the main heater track has a width W track and has a width W gap a central region comprising a plurality of generally parallel track sections separated by gaps of a heat spreading layer thickness H D is the minimum width W of the track section track Smaller than or the minimum gap width W gap Smaller, W track or W gap is evaluated in the central region of the main heater track. This means that the main heater track can be manufactured using PCB manufacturing techniques. It also means that the heater is thin enough for many applications requiring rapid temperature changes.

[0013] Preferably, the gap width W gap and / or width of track section W trackis less in the track sections near the edges of the main heater track than in the track sections in the central region of the main heater track, which improves the temperature uniformity in the central region of the main heater track.

[0014] Preferably, the heater further comprises a guard heater track between the heater track support layer and the heat spreading layer, the guard heater track substantially surrounding the main heater track and having two additional electrical contacts to the guard heater track that are independent of the four-terminal electrical contacts to the main heater track, which inhibits lateral heat flow and improves temperature uniformity in the plane of the main heater track.

[0015] Preferably, the heater track support layer is 1×10 -4 ~1×10 -2 km 2 / W, more preferably in the range of 3×10 -4 ~3×10 -3 km 2 / W range.

[0016] Preferably, the heater further comprises a reaction surface heat spreader layer positioned in contact with or within one of the heat spreading layer or the heater track support layer, thereby improving temperature uniformity across the reaction surface.

[0017] Preferably, the reactive surface heat spreader layer is thermally conductive, has a higher lateral thermal conductivity, and has a lower heat capacity than one of the heat spreading layer or the heater track support layer.

[0018] Preferably, the reactive surface heat spreader layer is located within the heater track support layer at a distance L from the main heater track. s Positioned across L s is the heater track width W evaluated in the central region track and heater gap width W gapThis further improves the temperature uniformity on the reaction surface.

[0019] A backside heat spreader layer is preferably positioned on the backside, which improves temperature uniformity across the reactive surface as well as improving thermal contact with any heat sink adjacent to the backside.

[0020] Preferably, the heater further comprises a heat sink in contact with the back surface, which has the effect of reducing the temperature of the heater when it is not powered.

[0021] In another aspect, the present invention provides a disposable consumable comprising a heater and a reaction cell positioned in contact with a reaction surface.

[0022] In another aspect, the present invention provides a method of operating a heater or variable temperature reactor, the method comprising driving a main heater track, simultaneously detecting a resistance of the main heater track, and calculating a temperature of the main heater track based on the detected resistance.

[0023] Preferably, the method includes performing feedback-based actuation of the main heater track according to a series of temperature set points for the main heater track to cycle the temperature of the reaction surface to perform PCR amplification.

[0024] Preferably, the method further comprises driving the guard heater tracks to provide a higher heat output per unit area than the main heater track.

[0025] Preferably, said heater or disposable consumable further comprises control circuitry configured to carry out said method.

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a simplified cross-sectional view of one embodiment of the present invention comprising a heater and a heat sink. [Figure 2] 1 shows two exemplary schematic arrangements of heater tracks and electrical connections for the heater of the embodiment. [Figure 3] 1 is a schematic diagram showing an electronic circuit that can be used to drive a heater track. [Figure 4] 4A and 4B show simulated temperature distributions for a guard heater according to one embodiment of the present invention, and a comparison with the temperature distribution without the guard heater. [Figure 5] FIG. 2 is another schematic cross-sectional view showing the heater of the embodiment. [Figure 6] Figures 6A and 6B show simulated temperature distributions using a heat spreader of variable thickness and at two different positions, and Figures 6C and 6D show simulated temperature distributions using a heat spreader at different relative positions to the heater track, according to an embodiment of the present invention. [Figure 7] 7A and 7B show simulated temperature distributions with and without a backside heat spreader, according to an embodiment of the present invention. [Figure 8] 1 shows the heater track temperature and reaction surface temperature variations during PCR thermal cycling for a heater according to one embodiment of the present invention. [Figure 9] 1 shows an alternative arrangement of resistive heating tracks in a heater 100 according to the present invention. [Figure 10] 10 shows an exemplary range of thermal resistance when the thermal cycle includes a hold step. DETAILED DESCRIPTION OF THE INVENTION

[0028] An exemplary heater suitable for performing thermal cycling for PCR amplification is described below. Thermal cycling is desirably performed so quickly that the time required for temperature change does not occupy a significant portion of the total thermal cycling time. The total thermal cycling time is the sum of the temperature change time and the reaction time. The slowest part of the PCR reaction is the extension phase, which requires approximately 1 second or more for a typical sequence length of 100 base pairs. Therefore, the goal is a temperature ramping time of <1 second. The target temperature for PCR is typically 60°C to 95°C, so a temperature ramp rate of 70°C / second or more is required for heating and cooling to reduce the temperature change time to 1 second. Temperature ramp rates much higher than this (200°C / second or higher) offer limited speed advantages because the reaction time, rather than the time required for temperature change, accounts for a significant portion of the total time required.

[0029] In one embodiment described below, a heater for performing rapid thermal cycling has a temperature ramp rate of approximately 100° C. / sec without the drawbacks associated with conventional heaters and temperature control systems.

[0030] The heater may be disposed with the reaction cell, for example, as a disposable consumable that is supplied with the reagents and power required to perform a single reaction test and may then be discarded.

[0031] The heater includes the following elements: a main heater track configured to enable simultaneous heating and temperature sensing via the temperature-dependent resistance of the heater track, a guard heater track substantially surrounding the main heater track, a heat spreading layer positioned between the heater track and the reaction surface, and a heater support layer positioned between the heater track and the heater backside. The heater may also be provided with a heat sink in thermal contact with the backside to enable rapid cooling of the heater when heater drive power is reduced.

[0032] FIG. 1 shows a schematic cross-section of one embodiment of the present invention comprising a heater 100 and a heat sink 200 .

[0033] The heater 100 has a reactive surface 110 on one side and a back surface 120 on the opposite side. The reactive surface 110 is heated by the heater to provide a time-varying and substantially spatially uniform temperature. The back surface 120 is in thermal contact with a heat sink 200 to allow cooling when the heater 100 is not powered.

[0034] In the following description, the axial direction is defined as being perpendicular to the reaction surface, and the lateral direction is defined as being in the plane of the reaction surface.

[0035] The heater comprises a main heater track 130 for resistively heating the reaction surface, however, it is desirable to limit lateral heat flow associated with temperature gradients and temperature non-uniformities across the reaction surface, which reduces the accuracy of temperature control.

[0036] To limit lateral heat flow within the main heater track area, the main heater track 130 is generally surrounded by guard heater tracks 140. Guard heater tracks are additional heater tracks positioned near the edges of the main heater track and driven to maintain a temperature close to or higher than the target temperature of the main heater track. The heat output per unit area of ​​the guard heater track is higher than that of the main heater track to compensate for lateral heat loss. The guard heater tracks may be driven independently of the main heater. The main heater track 130 and the guard heater tracks 140 may be formed from a metal such as copper, for example.

[0037] The main heater track 130 and guard heater track 140 are positioned between a heater track support layer 150 and a heat spreading layer 160. The heater track support layer 150 may comprise a printed circuit constructed from, for example, FR4 or polyimide or another electrically insulating support material.

[0038] Reactive surface heat spreader layers 170, 180 reside within or in contact with each of the heater track support layer 150 and the heat spreading layer 160. The reactive surface heat spreader layers 170, 180 are layers made of a material that has a higher thermal conductivity than the heat spreading layer or the heater track support layer. The function of these reactive surface heat spreader layers is to increase temperature uniformity over the reactive surface 110. These reactive surface heat spreader layers each have a thickness H S , thermal conductivity k S , density ρ s , and specific heat capacity C s while the heater track support layer 150 and the heat spreading layer 160 each have an individual thickness H B , H D , thermal conductivity k B , k D , density ρ B , ρ D , and specific heat capacity C B , C D To enhance temperature uniformity while maintaining a fast temperature response, the reactive surface heat spreader layer must have a higher lateral thermal conductivity and / or a lower heat capacity than the heater track support layer 150 / heat spreading layer 160. For the heat spreader layer to have a higher lateral thermal conductivity than the heat spreading layer, H S k S >H D k D In order for the heat spreader layer to have a lower heat capacity than the heat diffusion layer, H S ρ S C S <H D ρ D C D In the case of the heater support layer, these conditions are respectively H S k S >H B k B and H S ρ S C S <H B ρ B C B can be replaced with

[0039] The reactive surface heat spreader layers 170, 180 are each positioned close to the main heater track 130. In this example, the reactive surface heat spreader layer 170 on the heat spreading layer 160 is located 10 μm from the upper surface of the main heater track, and the reactive surface heat spreader layer 180 on the heater track support layer 150 is located 5 μm from the lower surface of the main heater track.

[0040] The back surface 120 is also provided with a back surface heat spreader 190 to improve temperature uniformity over the reaction surface 110 .

[0041] The heat sink 200 can take any form, including a solid block as shown in Figure 1 and individual pillars as described below in Figure 7. The backside heat spreader 190 is particularly useful when uniform thermal contact between the heater track support layer and the heat sink cannot be guaranteed.

[0042] To achieve good thermal contact with the main heater track, the thermal resistance-area product between the main heater track and the backside heat spreader or heat sink is preferably less than 1×10 -4 ~1×10 -2 km 2 / W, and more preferably, 3×10 -4 ~3×10 -3 km 2 It should be in the range of / W.

[0043] The heater and heat sink (if used) can have a planar or curved shape. A planar shape may be preferred for ease of construction and optical monitoring of the reaction for which the heater is intended. However, other shapes, such as partially spherical or cylindrical, are also possible and may have advantages in that the tensioned flexible reaction cell and heater layer can make good thermal contact with each other and with the heat sink, which is typically a rigid metal part.

[0044] FIG. 2 shows two exemplary schematic arrangements of resistive heating tracks and electrical connections in heater 100, including main heater tracks 130, guard heater tracks 140, and the electrical connections to these heater tracks.

[0045] As shown in FIGS. 2(i) and 2(ii), the primary heater track 130 in these embodiments has a serpentine configuration. Alternatively, the primary heater track 130 may comprise multiple track sections positioned in parallel and electrically connected in parallel. Similarly, as shown in FIGS. 2(i) and 2(ii), the guard heater track 140 in these embodiments also has a serpentine configuration. As can be seen from the example in FIG. 2, in some embodiments, the guard heater track 140 does not completely surround the primary heater track 130, but rather approximately surrounds the primary heater track 130 to the extent necessary to achieve the effect of limiting lateral heat flow within the area of ​​the primary heater track. In many embodiments, this requirement corresponds to the guard heater track 140 surrounding more than 50% of the perimeter of the primary heater track 130.

[0046] Figure 2(i) shows a heater with uniform track and gap widths in the main heater track 130, while Figure 2(ii) shows a main heater track 130 with larger track and gap widths in a central region 131 and smaller heater track and gap widths near the heater's edges 133. The edge regions 133 also contain tracks oriented parallel to the heater's edges to provide increased heat output per unit area and to reduce thermal conductivity perpendicular to the heater's edges and thereby reduce lateral heat flow in the central region 131 for improved temperature uniformity.

[0047] Spatially separated temperature sensors can also cause a time lag between the temperature change at the primary heater track and the temperature change at the temperature sensor. This time lag can cause problems such as heater element temperature overshoot or fluctuation. To avoid these problems, the primary heater track is configured as a temperature sensor that uses the resistance of the heater element to determine its temperature. Metallic heater elements typically have a positive temperature coefficient of resistance, while metal oxide or semiconductor heater elements have a negative temperature coefficient. It is desirable for the heater element's temperature coefficient of resistance (TCR) to be large, preferably greater than 500 ppm / K, and more preferably greater than 2,500 ppm / K.

[0048] The main heater track 130 has positive and negative connections 132 and 134 for electrical drive, and a voltage sensing V sense It has a four-wire connection with a positive connection 136 and a negative connection 138. V sense The measurement of V can be used to precisely monitor the track resistance using a circuit such as that shown in Figure 3. In combination with the known temperature coefficient of resistance TCR of the main heater track 130, or the desired temperature set point, V sense can be used to perform temperature sensing of the main heater track 130. Using a four-wire connection with separate contacts for driving the main heater track and sensing the voltage across it, instead of using a conventional two-wire connection for both drive and sensing, has the advantage of eliminating voltage drops due to the internal resistance of the connections supplying current to the main heater track.

[0049] The guard heater track 140 has a positive connection 142 and a negative connection 144 that should be driven independently of the main heater track 130 .

[0050] FIG. 3 shows a supply connection V that can be used to drive a main heater track and simultaneously sense the resistance of the main heater track and calculate the temperature of the main heater track based on the sensed resistance. pos and Vneg 3 shows a simplified electronic circuit driven by a voltage V across the heater track. Such a control circuit may be included with the heater 100 or may be connected while the heater is in use. Referring to FIG. 3, current flows through the heater track 130 via a positive drive connection 132 and a negative drive connection 134. The heater track has a voltage V across it. sense is provided with a four-wire contact that allows the voltage V to be measured using a positive voltage detection contact 136 and a negative voltage detection contact 138 and a voltage measurement circuit 310. The current flowing through the heater track 130 is measured by a resistor R isense current sense resistor 320, where V is known, and the voltage V across the current sense resistor isense The current through the heater is measured using a voltage measurement circuit 330 to measure I heater =V isense / R isense The resistance of the heater track 130 is then calculated as R heater =V sense / I heater Feedback-based driving of the main heater track may then be performed according to a series of temperature setpoints. Temperature control is performed according to the R heater This is implemented by determining a setpoint value for R and controlling the heater drive to match the heater resistance setpoint value. Alternatively, temperature control may be performed continuously over a temperature range based on a known temperature coefficient of resistance, TCR. Switch 340, which may be a transistor, is turned on to measure the heater resistance, which in turn determines R heater The switch 340 is turned off or left on for a predetermined time interval depending on whether the setpoint resistance is above or below the required setpoint resistance at that time. Alternatively, the switch 340 may be driven by a pulse-width modulated waveform with a duty cycle selected to drive the heater with the required power. In either approach, the switch 340 is used to modulate the electrical drive to the main heater track to cycle the temperature of the reaction surface and perform PCR amplification.

[0051] The guard heater tracks may be operated in closed loop control with a temperature setpoint equal to or greater than that of the main heater track, or the guard heater tracks may be operated with the same controller or on / off timing as the main heater elements, but with a different drive voltage that can be adjusted to optimize temperature uniformity at a particular temperature setpoint.

[0052] Referring again to Figure 2, longitudinal and lateral sections A and B of this exemplary configuration were simulated to determine the temperature distribution, as shown in Figures 4A and 4B. The results of these simulations demonstrate the increased temperature uniformity achieved by using the guard heaters.

[0053] Referring to Figures 4A and 4B, simulation results of the temperature distribution on the reaction surface were obtained from the center of the rectangular heater area to the longitudinal (A) and lateral (B) edges. In each figure, the vertical axis indicates temperature, and the horizontal axis indicates the position along the longitudinal / lateral direction from the center. The temperature distribution is shown without (solid line) and with (dashed line) a guard heater, showing a more uniform temperature distribution when a guard heater is used. The positions of the main heater and guard heater are indicated in each of Figures 4A and 4B.

[0054] 5 shows another schematic cross-section through the heater 100 and the heat sink 200. As shown in FIG. 5, the main heater track 130 has a width W track having a width W gap The track sections comprise a plurality of generally parallel track sections separated by gaps of a gap width W gap The heat output from the main heater track 130 is non-uniform due to the finite width of the track and gaps. This means that the thickness H of the heat spreading layer must be large enough to achieve rapid temperature changes. D In this embodiment, the thickness of the heat spreading layer H Dis the minimum width W of the track section track Less than or equal to the minimum gap width W gap Narrower track and gap widths increase temperature uniformity at the reaction surface, but this is limited by typical design rules such as the requirements of PCB manufacturing technology.

[0055] Figure 5 also shows the simulation region C where the heater and heat sink are simulated. Figures 6A, 6B, 6C, and 6D show the simulated temperature within the simulation region C along the reaction surface. The simulations were performed using W track and W gap The figure assumes a copper track heater with a constant t=75 μm, and further assumes that the heater track support layer 150 is made of FR4 and the heat spreading layer 160 is made of polypropylene. The effect of increasing the heat spreader layer thickness is shown for two cases, where the vertical axis represents the temperature on the reaction surface and the horizontal axis represents the position from the center of the heater track along the reaction surface within simulation region C. Figure 6A shows the results of a simulation (Configuration A) in which an aluminum reaction surface heat spreader layer 170 is positioned between the heater track in the heat spreading layer and the reaction surface 110, 10 μm from the heater track, and the reaction surface heat spreader layer 180 is omitted. Figure 6B shows the results of a simulation (Configuration B) in which an aluminum reaction surface heat spreader layer 180 is positioned in the heater track support layer between the heater track of the heater and the backside surface 120, 5 μm from the heater track, and the reaction surface heat spreader layer 170 is omitted. In both cases, the heat spreader layer improves temperature uniformity, with thicker heat spreader layers being more effective, and configuration A being more effective than configuration B.

[0056] Figures 6C and 6D show simulation results for varying the position of the reactive surface heat spreader layer 170. In Figure 6C, the reactive surface heat spreader is positioned within the heat spreading layer, and the distance shown in the legend in the graph of Figure 6C indicates the separation between the top surface of the heater track and the heat spreader layer. In Figure 6D, the heat spreader is positioned within the heater support layer, and the distance shown in the legend in the graph of Figure 6D indicates the separation between the bottom surface of the heater track and the heat spreader layer. In both cases, the heat spreader is made of aluminum and is 100 nm thick. When the heat spreader is positioned within the heat spreading layer, the position of the reactive surface heat spreader has little effect on temperature uniformity (Figure 6C). However, when the reactive surface heat spreader is positioned within the heater support layer, it is preferable to position the reactive surface heat spreader within 15 μm of the heater to provide a substantial improvement in temperature uniformity (Figure 6D). This distance corresponds to the track and gap width and is equal to 20% of the smallest track and gap width evaluated in the central region.

[0057] In FIG. 1 , the heater 100 includes a backside heat spreader 190. While this feature is not required in all embodiments of the present invention, the backside heat spreader 190 has the advantage of further improving temperature uniformity across the reaction surface 110, as demonstrated using simulations. FIGS. 7A and 7B show simulation results comparing a heater without ( FIG. 7A ) and with ( FIG. 7B ) a backside heat spreader 190. In each figure, the upper plot shows the 40°C to 60°C temperature contours on the simulated heater. The simulated heater includes a heater track, shown as a dashed line; the shorter dashed line represents the main heater track 130, and the longer dashed line represents the guard heater track 140. Above the heater track, the reaction cell 710 is surrounded by a heat spreading layer 160 with the reaction surface 110, so that the temperature of the contents of the reaction cell can be controlled according to the temperature of the reaction surface. Additionally, in each figure, the lower plot shows the temperature profile along the reactive surface (solid line, legend "A"), in the plane cutting the heater track (legend "B"), and on the backside of the heater (legend "C"). Figure 7B assumes that the backside heat spreader is constructed from a 12 μm thick copper layer. In both simulations, the heat sink 200 with non-uniform thermal contact is represented as a set of three aluminum pillars, each 0.5 mm wide and 1.0 mm high. The geometry and results are shown for a 2D half-model with the plane of symmetry at x = 0. In all cases, the heater set point is 60 °C.

[0058] Figure 8 shows a simulation of the transient response of the heater described above with a rear heat spreader thermally cycled with temperature set points of 58°C, 73°C, and 98°C for a cycle time of 4 seconds. The temperature of the main heater track is shown by trace A (dashed line), and the temperature at the center of the reactive surface is shown by trace B (solid line).

[0059] As an example, a heater according to the present invention may be used to provide heat to a reaction. In such use, the reaction surface of the heater is positioned in contact with a reaction cell having a reaction volume containing a sample. To heat the reaction surface, the heater element is switched on, and heat generated by the heater element flows through the reaction surface into the reaction volume. If rapid cooling is required, the heater can contact a heat sink at its back side so that when the heater element is turned off, heat flows from the reaction surface through the heater and into the heat sink.

[0060] When a heater is applied for thermal cycling, such as to drive a PCR reaction, it is advantageous for the thermal diffusion time between the heater and the sample to be shorter than the target cycle time. Generally, the thermal diffusion time t of a material sample is: t=L 2 / D is given by where L is the characteristic length scale of the material sample and D is the thermal diffusivity of the material. Table 1 below shows one exemplary choice of material for a heater according to the present invention, where the heat diffusion time of the heat spreading layer is shorter than the reaction time of PCR, which is understood to take approximately 1 second to amplify a 100 base pair DNA sequence.

[0061] Furthermore, the thermal resistance R of the heater track support layer T is the temperature profile and heat sink temperature T Sink and heater power p Heat The temperature can be optimized to minimize the thermal cycling time for T LOW and T HIGH The time required for thermal cycling between R and R is minimized when the heating time is equal to the cooling time, and this condition is met by T =R T,Opt When , the following equation is satisfied:

[0062] R T,Opt =(T HIGH +T LOW -2T Sink ) / ρ Heat Table 2 (below) shows exemplary values ​​for heater power, optimum thermal resistance and thermal cycling time for a 50 mm2 area wafer cycled between 60°C and 95°C with a heat sink temperature of 30°C. 2 and the case of a reaction surface with a heat capacity of 0.04 J / K.

[0063] Table 3 (below) shows exemplary values ​​for heater power, optimal thermal resistance, and thermal cycle time for the case where the thermal cycle includes a hold step of 1 second duration at 72°C. These are for a 50 mm2 area wafer cycled between 60°C and 95°C with a heat sink temperature of 30°C. 2 and the case of a reaction surface with a heat capacity of 0.04 J / K.

[0064] 9 shows an alternative arrangement of resistive heating tracks in a heater 100 according to the present invention. In this embodiment, two main heater tracks 130 are arranged side-by-side to individually heat different areas of the reaction surface 110. Both main heater tracks are surrounded and separated by guard heater tracks 140.

[0065] The embodiment of Figure 9 shows how a heater according to the present invention can be equipped with a main heater track for each of multiple individually temperature-controlled areas of a reaction surface. The guard heater tracks 140 inhibit lateral heat flow, thereby increasing the precision with which each individual area of ​​the reaction surface can be temperature-controlled.

[0066] 9, the guard heater track 140 has three connections 142, 144, and 146 so that the current and heat output per unit area can vary between and around the two main heater tracks 130. Alternatively, each main heater track 130 may be equipped with a separate guard heater track 140 with two connections.

[0067] FIG. 10 shows an example of a preferred range 1001 of thermal resistance when the thermal cycle includes a hold step for controlling a heater or variable temperature reactor as described herein. A PCR cycle consists of melting, annealing, and extension steps, with extension often being the most time-consuming part of the reaction and requiring a hold step. This example includes a 1-second hold step at 72°C to allow time for extension in the PCR reaction. The time required for extension can vary depending on the speed of the polymerase and the length of the DNA sequence being amplified. A 1-second hold step may be appropriate for rapid amplification of DNA sequences with lengths in the 100-150 base pair range, typically used in nucleic acid-based diagnostic tests; longer sequences generally require longer extension times. The duration of the hold step is optimally long enough to allow for extension, but not excessively long; otherwise, it can dominate the overall cycle time, resulting in undesirable extension. Those skilled in the art will readily appreciate that adjustments to the hold step duration, illustrated as 1 second in the above example, can be made without significantly affecting the overall operation.

[0068] The graph in FIG. 10 shows the preferred range of thermal resistance values ​​(shown on a logarithmic scale) to allow both low thermal cycle times (solid line) and low energy consumption per cycle (dashed line), and indicates the minimum thermal cycle time, t cycle 1004 becomes undesirably large (>5 seconds) when the thermal resistance is greater than the desired maximum value 1003, while the energy dissipated per cycle E cycle 1005 becomes undesirably large (>10 J) when the thermal resistance is lower than the minimum desired value 1002. In summary, low energy consumption per cycle (A cell =5×10 -5 m 2 DES cycle <10J) Rapid Thermal Cycle (t cycle <5 seconds), 3 x 10 -3 ~3×10 -2 km 2The product R of the thermal resistance in the range of / W and the cell area T,Opt ×A cell is preferred.

[0069] In the above-described embodiment, the heater is provided in an assembly with a heat sink. However, the present invention is also applicable to cases where uniform heating is required but a heat sink is not necessary. For example, in applications where cooling time is not critical, the heat sink may be omitted.

[0070] In the above-described embodiment, the heater is equipped with a guard heater track 140. However, in addition to or instead of providing a guard heater track 140, the main heater track 130 may be designed to have a higher heat output near its edges and extend beyond the reaction volume. This higher heat output effect may be achieved by increasing the heater track density by reducing the gap width between two or more heater track portions closer to the edges of the main heater track than the central heater track portion of the main heater track. Alternatively, or additionally, this effect may be achieved by increasing the resistance of the main heater track by reducing the width or height of one or more heater track portions closer to the edges of the main heater track than the central heater track portion of the main heater track. The higher heat output of the heater elements near the edges can compensate for lateral heat flow and provide more uniform temperature conditions across the reaction volume. Furthermore, if the heater has a reaction surface that extends well beyond the required reaction volume, it is possible to omit both the guard heater tracks and the modifications near the edges of the main heater track.

[0071] Furthermore, the preceding description evaluates the inclusion and exclusion of each of the heat spreaders, and the reader will therefore understand that, although preferably included, each of heat spreaders 170, 180, and 190 may be omitted in embodiments of the present invention.

[0072] [Table 1]

[0073] Table 2

[0074] Table 3

Claims

1. 1. A heater for thermal cycling for performing PCR amplification, comprising: a heat spreading layer having a reaction surface for transferring heat to the reaction cell; a heater track support layer having a cooling back surface; an electrically conductive primary heater track supported between the heater track support layer and the heat spreading layer, the primary heater track being in the form of a plurality of generally parallel track sections electrically connected to one another to form the primary heater track, allowing simultaneous heating and temperature sensing of the reaction surface; and a four-terminal electrical contact to the main heater track adapted to provide an electrical connection for driving the main heater track and simultaneously sensing the resistance of the main heater track; Equipped with The area of ​​the reaction surface is greater than the square of the thickness H of the heater, so that the area of ​​the reaction surface A>H ２ That's the heater.

2. The main heater track has a plurality of generally parallel track section widths W ｔｒａｃｋ and has a width W ｇａｐ and the thickness of the heat spreading layer H Ｄ is the width W of the track section ｔｒａｃｋ or the width W of the gap ｇａｐ Smaller, W ｔｒａｃｋ or W ｇａｐ The heater of claim 1 , wherein is evaluated in a central region of the main heater track.

3. The gap width W ｇａｐ and / or the track section width W ｔｒａｃｋ 3. The heater of claim 2, wherein track sections near outer edges of the main heater track are smaller than track sections within the central region of the main heater track.

4. a guard heater track between the heater track support layer and the heat spreading layer, the guard heater track substantially surrounding the main heater track; two further electrical contacts to the guard heater track that are independent of the four-terminal electrical contact to the main heater track; The heater of claim 1 , further comprising:

5. The heater track support layer is 1×10 －４ ~1 x 10 －２ K.m. ２ / W, more preferably 3×10 －４ ~3 x 10 －３ K.m. ２ 5. A heater according to claim 1, having a thermal resistance-area product in the range of 1 / W.

6. 6. The heater of claim 1, further comprising one or more reactive surface heat spreader layers positioned in contact with or within one or both of the heat spreading layer or the heater track support layer.

7. 7. The heater of claim 6, wherein the reactive surface heat spreader layer has a higher thermal conductivity, a higher lateral thermal conductivity, and a lower heat capacity than one of the heat spreading layer or the heater track support layer.

8. The reactive surface heat spreader layer is disposed within the heater track support layer at a distance L from the main heater track. ｓ are positioned apart, and L ｓ is the heater track width W evaluated in the central region ｔｒａｃｋ and heater gap width W ｇａｐ The heater according to claim 2 or 3, and claim 6 or 7, wherein the minimum value of the temperature is less than 20%.

9. 9. The heater of claim 1, wherein a backside heat spreader layer is positioned on the backside for cooling.

10. 10. The heater of claim 1, further comprising a heat sink in contact with the back surface for cooling.

11. A disposable consumable product comprising the heater according to any one of claims 1 to 10 and a reaction cell arranged in contact with the reaction surface.

12. A method of operating a heater as described in any one of claims 1 to 10 or a method of operating a disposable consumable as described in claim 11, the method comprising driving the main heater track, simultaneously detecting a resistance of the main heater track, and calculating a temperature of the main heater track based on the detected resistance.

13. 13. The method of claim 12, comprising performing feedback-based actuation of the main heater track according to a series of temperature set points for the main heater track to cycle the temperature of the reaction surface to perform PCR amplification.

14. 14. The method of claim 12 or claim 13, wherein the heater is a heater as defined in claim 4, and the method further comprises driving the guard heater track to provide a higher heat output per unit area than the main heater track.

15. A heater according to any one of claims 1 to 10, further comprising a control circuit configured to carry out a method according to any one of claims 12 to 14.

16. 11. The heater of claim 1, wherein the plurality of track sections of the main heater track have a serpentine configuration or the plurality of track sections are electrically connected in parallel.

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