EP0379437B1 - Method and apparatus for the rapid regulation of the temperature of a wall - Google Patents

Abstract

PCT No. PCT/FR90/00042 Sec. 371 Date Sep. 18, 1990 Sec. 102(e) Date Sep. 18, 1990 PCT Filed Jan. 19, 1990 PCT Pub. No. WO90/08298 PCT Pub. Date Jul. 26, 1990.A method and apparatus for high speed temperature regulation of elements (12) in thermal contact with a fluid contained in liquid-vapor equilibrium inside an enclosure (10) which is closed in sealed manner and which is provided with thermal insulation, temperature regulation being provided by means of an external heat source (S) imposing a reference temperature (Tc) to the fluid contained inside the enclosure (10) and causing a corresponding variation in the temperature (Te) of the elements (12) by changing the phase of the fluid. The invention is particularly applicable to performing molecular biology reactions at controlled temperature.

Description

The invention relates to a method and a device for rapid thermal regulation of a plurality of wall zones according to the preamble of claim 1 and according to the preamble of claim 6.

Such a method and such a device are known from US-A-4 679 615. Such a method is used in particular for molecular biology operations comprising reactions at controlled temperature such as for example enzymatic DNA treatment operations.

Some of these operations require submitting samples of cells or macromolecules to thermal cycles comprising temperature stages each determined very precisely in duration and in temperature (ΔT <0.1 ° C). In some cases, these temperature cycles must be repeated many times.

It is moreover desirable, for reasons of yield, to carry out these operations simultaneously on a large number of samples. It is then necessary to be able to control over time, in a very precise manner, the temperature of a large number of samples, to vary the temperature of these samples in a uniform manner, and to make the transitions between the temperature stages as quickly as possible to that the total duration of a given operation is compatible with an industrial application (the duration of biological reactions cannot be reduced).

Document US-A-4 679 615 discloses a method and an apparatus for heating and cooling biological samples by means of a heat conducting plate which carries the samples and the ends of which are in contact with a liquid that you can heat or cool. The ends of the plate are expected to be at temperatures different to establish a temperature gradient in the plate, so that the biological samples are subjected to different temperatures. This method and this device do not allow biological samples to be submitted simultaneously to identical thermal cycles.

Document FR-A-2 193 187 describes an isothermal heating device with several heating chambers of the "heat pipe" type, that is to say comprising a reservoir containing a fluid for transporting heat in the liquid phase and in the vapor phase , and a heat source such as a burner or an electrical resistance, associated with this tank. This device makes it possible to maintain a constant temperature in the heating chambers, but does not make it possible to simultaneously carry out thermal cycles therein comprising temperature stages separated by abrupt transitions.

The subject of the invention is precisely a method and a device for rapidly regulating a temperature, which make it possible to avoid the drawbacks of the known technique and to satisfy the conditions expressed above.

The subject of the invention is also a method and a device of this type, which are in particular applicable to carrying out molecular biology operations of the aforementioned type, simultaneously on a large number of biological samples.

The subject of the invention is also a method and a device of this type, which are applicable to other cases, when the temperature of an element or a set of elements has to be varied quickly and precisely. , as is for example the case in reactors with controlled wall temperature, enzymatic reactors, cellular reactors, reactors for polymerization, treatment or transformation of plastic materials, in photography (treatment of movies), etc.

The invention therefore provides a method of rapid thermal regulation of a plurality of wall zones in particular of receptacles containing biological samples, in order to simultaneously submit them to identical thermal cycles comprising successive stages of predetermined durations and temperatures separated by transitions, using for this purpose an enclosure surrounding said wall areas and containing a heat transfer fluid in thermal contact with these wall areas, and an external source of heat associated with the enclosure to yield and take heat from said fluid in order to maintain the temperature of the wall zones equal to a set temperature imposed by the source, characterized in that it consists in sealingly enclosing a liquid-vapor balance of said fluid in said enclosure, the latter allowing free circulation of the vapor phase of the fluid and having an internal coating of circula capillary action of the liquid phase of the fluid, and to control said source to vary the set temperature in accordance with the stages of the aforementioned thermal cycles and to make abrupt transitions between these stages, the temperature of said wall zones following almost instantaneously the variations in said set temperature by local condensations and sprays of the fluid in the enclosure.

The invention makes a particular application, of the technique of the "heat pipe" used initially in the space industry to quickly evacuate a large quantity of heat produced by a heating element, which is in general an electronic unit integrated into a satellite. The heat pipe is essentially a closed tube containing an internal coating of a porous material with capillary circulation of liquid, and a determined fluid remaining in the two-phase liquid-vapor state in the tube under the working conditions envisaged. The two ends of the tube are connected, one to the heating element, the other to a surface for dissipating heat outside by radiation. The transfer of heat between the heating element and the outside takes place in the heat pipe by phase change of the fluid which, in a continuous manner, vaporizes in the vicinity of the heating element and condenses in the vicinity of the surface of diffusion towards the exterior, the coating of capillary material ensuring in a continuous and almost instantaneous manner the transfer of the liquid from the cold end to the hot end of the heat pipe. The thermal conductivity of a heat pipe is very high, several orders of magnitude greater than that of copper, for example.

This principle has also been used, as already said, for heating rooms at constant temperature.

The invention uses this known principle for a different purpose, to achieve precise and almost instantaneous cycles of temperature variation of walls in contact with an appropriate fluid. More specifically, the invention makes it possible to heat and cool at will and almost instantaneously samples in thermal contact with an appropriate fluid in two-phase liquid-vapor equilibrium, and to maintain these samples at a precise temperature for a determined period.

In other words, the invention makes it possible, using the same means, to maintain a temperature at a predetermined value and to suddenly vary this temperature to another predetermined value, thanks to the fact that the means used present vis-à-vis the outside, a substantially infinite thermal inertia (which allows it to maintain the temperature precise predetermined and to withdraw it from the influences of parasitic external phenomena), that is to say a substantially zero thermal inertia (which allows it to vary this temperature very quickly, to another predetermined value).

According to a particular embodiment of the invention, the method also consists in determining the nature and the total mass of the fluid as a function of the volume of said enclosure so that the liquid-vapor balance of the fluid and the impregnation of the capillary coating by the fluid in the liquid phase are maintained for any temperature within a predetermined range of set temperatures.

When the method according to the invention is used for molecular biology operations, where the temperature of a sample can vary according to a determined cycle between extreme values of approximately 0 and 100 ° C. for example, the invention makes it possible to vary almost instantaneously the temperature of the samples subjected to these reactions, to make it take any value between the aforementioned extreme values.

The heat source used can be of the reversible type, making it possible to selectively increase and decrease the set temperature of the fluid, or else can comprise two switchable heat sources, one making it possible to increase the set temperature of the fluid and the other to decrease it.

As a variant, the external energy source may comprise means making it possible to vary the vapor pressure of the fluid in the enclosure.

Indeed, a variation in the vapor pressure of the fluid in the enclosure makes it possible either to raise the temperature of this fluid (compression of the vapor phase), or to decrease this temperature (expansion of the vapor phase). With calibration and precise detection of the pressure and the temperature of the fluid, a conventional means of varying the pressure of the deformable wall type for example, makes it possible to determine the set temperature of the fluid.

In the case where the invention is applied to molecular biology reactions, the elements whose temperature will be regulated can be tubes provided with filtration membranes and containing biological samples such as cells or macro-molecules, and the method according to the invention then consists in combining the cyclic temperature variations with additions of reagents and pressure variations in the tubes, for example for the treatment of DNA.

In this case, the durations of the transitions between predetermined temperature stages become appreciably negligible compared to the cumulative duration of the biological reactions themselves.
The invention also provides a device for rapid thermal regulation of a plurality of wall zones, in particular of receptacles containing biological samples, for simultaneously subjecting them to identical thermal cycles comprising successive stages of predetermined durations and temperatures separated by transitions, this device comprising an enclosure surrounding said wall areas and containing a heat transfer fluid in thermal contact with these wall areas, and an external source of heat associated with the enclosure for transferring and taking heat from said fluid in order to maintain the temperature of the wall zones equal to a set temperature imposed by said source, characterized in that the enclosure is sealed and contains a liquid-vapor balance of said fluid, this enclosure allowing the free circulation of the vapor phase of the fluid and comprising an internal coating capillary circulation of the liquid phase of the fluid, the device comprising source control means for varying the set temperature in accordance with the stages of the aforementioned thermal cycles and for making sudden transitions between these stages, the temperature of said wall zones following almost instantaneously the variations in said temperature setpoint by local condensation and vaporization of the fluid in the enclosure.

In one embodiment of this device, applicable in particular to molecular biology reactions, the enclosure has parallel passages opening to the outside and forming receptacles or housing of tubes in which are placed biological samples such as cells or macromolecules .

The walls of these passages form means of heat transfer by conduction between the contents of the receptacles or the tubes and the fluid contained in the enclosure, while the walls of the enclosure on which the ends of the passages open are covered with sealing by hoods associated with means for pressurizing or vacuuming the content of the receptacles or tubes.

Preferably, the tubes are carried at one end by the same transverse plate intended to be applied to a wall of the enclosure when the tubes are housed in the passages of the enclosure.

A very large number of tubes can thus be treated simultaneously, each containing a biological sample.

• la figure 1 est un schéma de principe de l'invention ;
• la figure 2 représente schématiquement un dispositif selon l'invention, pour des opérations de biologie moléculaire ;
• la figure 3 est une vue schématique en coupe d'une partie essentielle du dispositif de la figure 2;
• la figure 4 représente schématiquement une variante de réalisation du dispositif.

The invention will be better understood and other details and advantages thereof will appear more clearly on reading the description which follows, given by way of example, with reference to the appended drawings in which:

• Figure 1 is a block diagram of the invention;
• FIG. 2 schematically represents a device according to the invention, for molecular biology operations;
• Figure 3 is a schematic sectional view of an essential part of the device of Figure 2;
• FIG. 4 schematically represents an alternative embodiment of the device.

Reference is first made to FIG. 1 to explain the principle of the invention.

The reference 10 designates a closed sealed enclosure and preferably at least locally insulated, comprising a wall 12, for example tubular, whose temperature is to be varied. The wall 12 is in contact with a fluid enclosed in the enclosure 10 and which is in liquid-vapor equilibrium for all the values between which it is desired to vary the temperature of the wall 12. The fluid in the liquid phase completely impregnates a coating 14 made of porous or fibrous material for example, capable of ensuring capillary circulation of the liquid, and which lines the enclosure 10 and the wall 12 by providing continuous paths for capillary circulation of liquid between the wall 12 and a peripheral part of the enclosure wall 10.

This peripheral wall of the enclosure 10 is in thermal contact with an external energy source S such as a heat source of the reversible type (with Peltier effect for example or with circulation of fluid). This source S is intended to impose a set temperature Tc on the fluid which is in the enclosure 10 in liquid-vapor equilibrium, so that the temperature Te of the wall 12 becomes equal to the set temperature Tc as quickly as possible. possible. When the set temperature Tc is higher than the temperature of the fluid, there is locally, in the zone of thermal contact with the external heat source S, a vaporization of part of the fluid in liquid phase, which results in an increase in the pressure inside the enclosure 10. As the liquid-vapor equilibrium temperature varies in the same direction as the pressure, the aforementioned increase in pressure results in an increase in the value of the liquid-vapor equilibrium temperature in the enclosure. This temperature becomes higher than the temperature of the wall 12, which causes local condensation of the fluid. This condensation results in the release of heat, the fluid yielding its latent heat of condensation to the cold parts of the enclosure. If the enclosure 10 is suitably insulated, the only available cold source is the wall 12, which therefore receives the latent heat of condensation from the condensed part of the fluid. This heat supply results in an increase in the temperature Te of the wall 12.

This double phenomenon of local vaporization of the fluid in the zone of thermal contact with the external heat source S, and of local condensation in the zone of contact with the wall 12 results in a capillary circulation of the liquid from the wall 12 to the zone contact with the source S, and continues until the temperature equilibrium obtained for Tc = Te. As the latent heat of condensation of the fluid is much greater than its specific heat for the temperature variations considered, the rise in temperature of the wall 12 is almost instantaneous. It is in fact the heat transfers by conduction through the wall of the enclosure 10, which will slow down the temperature regulation.

Conversely, when it is desired to decrease the temperature of the wall 12 relative to the equilibrium temperature, the set temperature Tc is reduced to the desired value, which results in local condensation of fluid in the pregnant 10, a decrease in the pressure in this enclosure and a corresponding decrease in the liquid-vapor equilibrium temperature of the fluid, and therefore by vaporization of liquid in the vicinity of the wall 12. The vaporizing liquid takes its latent heat of vaporization on the wall 12, which is the only hot spring available. The temperature of the wall 12 therefore decreases until it becomes equal to the set temperature Tc, thanks to the transfer of fluid in the liquid phase in the capillary coating of the enclosure 10, between its zones of thermal contact with the source S and the wall 12.

A choice of suitable materials makes it possible to improve the transfer of heat by conduction between the fluid contained in the enclosure 10, the wall 12 and the external heat source S. With regard to the latter, the means of connection with the enclosure 10 can also be of the heat pipe type if necessary and optionally shaped to receive several enclosures simultaneously.

It is of course possible, instead of using a heat source S of the reversible type, to selectively use a hot outside source and a cold outside source, one of which will serve to increase the set temperature, and the other to decrease it. .

It is also, as a variant, this external heat source can be replaced by an appropriate means for varying the vapor pressure of the fluid inside the enclosure 10. This pressure variation can be done, either by injecting fluid under pressure in the enclosure, either by reducing the volume of the enclosure, by means of a movable wall or an elastically deformable wall of the membrane type.

In all cases, an external energy source S makes it possible, by changing the phase of the fluid contained in the enclosure 10, to vary the temperature of the wall 12 rapidly, almost instantaneously.

The enclosure 10 also makes it possible to maintain the temperature of the wall 12 at a set value imposed by the source S. Any variation in the temperature of the wall 12 which would be due for example to the release or absorption of heat during a chemical reaction is immediately and automatically compensated for by the enclosure 10 which also protects the wall 12 from parasitic external influences.

FIG. 2 represents a device for applying the principle according to the invention. To make it easier to understand, the same references have been given in FIG. 2 as in FIG. 1 to the elements of the device which correspond to those represented in FIG. 1.

In FIG. 2, therefore, we find a tightly closed enclosure 10 containing an appropriate fluid in two-phase liquid-vapor equilibrium and an internal coating ensuring capillary circulation of the fluid in the liquid phase, and in which are arranged passages for receiving the elements of which the temperature must be regulated. The external heat source S is in thermal contact by conduction with the peripheral wall of the enclosure 10, the two upper and lower transverse walls 16,18 of which are insulated.

The elements are tubes 12 carried by the same plate 20 and are intended to engage in parallel through passages 22 of the enclosure 10 which are shaped so as to receive the tubes 12 by establishing good thermal contact with them. For this, the tubes 12 can have a slightly frustoconical outer surface, the passages 22 having a corresponding inner surface.

The tubes 12 are in the present case open at their two ends, and their upper ends open onto the upper face of the plate 20. Des covers 24 and 26 are provided for sealingly covering, respectively, the plate 20 carrying the tubes 12 and the underside 18 of the enclosure 10. These covers 24, 26 are connected to means 28 for controlling the pressure prevailing at the two ends of the tubes 12, on either side of a filtration membrane mounted transversely inside each tube 12.

The means 28 also control the operation of the external energy source S, to regulate the temperature in the tubes 12.

Figure 3 is a schematic sectional view, in more detail, of the essential part of this device in the operating position.

FIG. 3 shows the cylindrical tubes 12 comprising a filtration membrane 30, which are embedded in the through passages 22 of the enclosure 10, and the covers 24 and 26 mounted in sealed manner, respectively on the plate 20 carrying the tubes 12 and on the lower wall of the enclosure 10. Plates or sheets 32 of thermally insulating material perforated at the outlet of the passages 22 are interposed between the upper and lower walls of the enclosure 10 on the one hand, and the plate 20 and the lower cover 26, respectively, on the other hand.

The fluid used in the device according to the invention is for example a "freon" (registered trademark) having the required characteristics.

The coating of material, for example porous or fibrous, ensuring the capillary circulation of the liquid inside the enclosure 10 may be a material, for example sintered, wettable by the liquid and conventionally used in the refrigeration industry.

The enclosure 10 is made of a material resistant to pressure variations (these are of the order of about 15% on either side of an average pressure when the temperature varies from 0 to 100 ° C.), the material which can be either a good thermal conductor such as brass for optimal heat transfer with the external source S, or a thermally insulating material to reduce heat transfers through the upper and lower faces 16, 18 of the enclosure. In the first case, the faces 16, 18 of the enclosure are insulated while, in the second case, heat transfer means are provided through the peripheral wall of the enclosure.

In the variant embodiment shown diagrammatically in FIG. 4, the device comprises an enclosure 10 of the aforementioned type, associated with an external heat source S and receiving, in the cavities of its upper face, wells or tubes 12 carried at their upper ends by the same plate 20. This plate 20 is covered with a film 34 of impermeable material which closes the wells or tubes 12. A heating or cooling hood 36 covers the plate 20 and is associated with means 38 for thermal regulation maintaining its temperature substantially equal to that of the tubes 12.

Of course, the cover 36 can also be constituted by an enclosure of the same type as the enclosure 10, associated with the same source S as the latter.

The number of tubes 12 carried by the plate 20 can be relatively large (for example and conventionally 96 tubes in 8 rows and 12 columns) and the tubes 12 can be molded in one piece with the plate 20.

The device according to the invention can be used with a single external heat source, of the reversible type, or else with two switchable heat sources, one hot and the other cold.

The device according to the invention will, in practice, be associated with a robot controlled by computer, which will arrange the samples to be processed and the any additives or reagents in the tubes 12, place the plate 20 carrying the series of tubes 12 on the enclosure 10, possibly move this enclosure from one heat source to the other, etc. The pressure control at the ends tubes 12 will allow filtration, dialysis, recovery of solid matter by reversing the pressure difference, etc.

Claims (16)

1. A method of high speed temperature regulation of a plurality of wall zones (12, 20), in particular of receptacles containing biological samples, for the purpose of subjecting them simultaneously to identical thermal cycles including successive stages of predetermined temperatures and durations, the stages being separated by transitions, by using an enclosure (10) surrounding said wall zones and containing a heat transfer fluid in thermal contact with the wall zones, and an external heat source (S) associated with the enclosure to take heat from and to give heat to said fluid so as to maintain the temperature of the wall zones equal to a reference temperature imposed by the source, the method being characterized in that it consists in enclosing in sealed manner a liquid-vapor equilibrium of said fluid in said enclosure (10), said enclosure enabling the vapor phase of the fluid to flow freely and including an internal lining for capillary flow of the liquid phase of the fluid, and in controlling said source (S) to vary the reference temperature in accordance with the above-mentioned stages of the thermal cycles and to implement the sudden transitions between said stages, the temperature of said wall zones quasi-instantaneously tracking the variations of said reference temperature by local condensation and vaporization of the fluid in the enclosure (10).
2. A method according to claim 1, characterized in that it consists in determining the total mass and the nature of the fluid as a function of the volume of the enclosure (10) in such a manner that liquid-vapor equilibrium of the fluid and impregnation of the coating (14) by the fluid in the liquid phase are maintained for all temperatures lying within a predetermined range of reference temperatures.
3. A method according to claim 1, characterized in that said source (S) is of a reversible type, enabling the reference temperature (Tc) to be increased or decreased selectively.
4. A method according to claim 1 or 2, characterized in that it consists in associating the enclosure (10) with two switchable heat sources, one hot and one cold, and in controlling them in alternation respectively to increase and decrease the temperature of said wall zones.
5. A method according to any one of claims 1 to 4, characterized in that it also consists in associating said source (S) with means for varying the vapor pressure of the fluid inside the enclosure (10).
6. Apparatus for high speed temperature regulation of a plurality of wall zones (12, 20), in particular receptacles containing biological samples, for the purpose of subjecting them simultaneously to identical thermal cycles including successive stages of predetermined temperatures and durations, the stages being separated by transitions, this apparatus including an enclosure (10) surrounding said wall zones and containing a heat transfer fluid in thermal contact with the wall zones, and an external heat source (S) associated with the enclosure to take heat from and to give heat to said fluid so as to maintain the temperature of the wall zones equal to a reference temperature imposed by the source, the apparatus being characterized in that the enclosure (10) is sealed and contains a liquid-vapor equilibrium of said fluid, said enclosure enabling the vapor phase of the fluid to flow freely and including an internal lining (14) for capillary flow of the liquid phase of the fluid, the apparatus including means (28) for controlling the source (S) to vary the reference temperature in accordance with the above-mentioned stages of the thermal cycles and to implement the sudden transitions between said stages, the temperature of said wall zones quasi-instantaneously tracking the variations of said reference temperature by local condensation and vaporization of the fluid in the enclosure (10).
7. Apparatus according to claim 6, characterized in that said source (S) is reversible, being selectively capable of supplying heat to the fluid and of taking heat from the fluid.
8. Apparatus according to claim 6, characterized in that said external source comprises two switchable heat sources: a hot source and a cold source.
9. Apparatus according to claim 6, characterized in that said source comprises means for varying the vapor pressure of the fluid contained in the enclosure (10).
10. Apparatus according to any one of claims 6 to 9, characterized in that the external source (S) is in thermal contact with said fluid via at least a portion of one of the walls of the enclosure (10), with the other walls (16, 18) being provided, at least locally, with thermal insulation.
11. Apparatus according to any one of claims 6 to 10, characterized in that said enclosure (10) includes parallel passages (22) opening out to the outside and forming receptacles and/or housings for the tubes (12).
12. Apparatus according to claim 11, characterized in that the walls of said passages (22) form means for transferring heat by conduction between the contents of the receptacles or the tubes (12) and the fluid contained inside the enclosure (10).
13. Apparatus according to claim 11 or 12, characterized in that the walls (16, 18) of the enclosure into which the ends of the passages (22) open out are covered in sealed manner by respective caps (24, 26) associated with means (28) for selectively raising or lowering the pressure of the contents of said receptacles or tubes (12).
14. Apparatus according to claim 13, characterized in that the tubes (12) are open at both ends and are provided with filter membranes (30).
15. Apparatus according to any one of claims 11 to 14, characterized in that said one end of each of said tubes (12) is carried by a common transverse plate (20) for application against one of the walls (16) of the enclosure (10).
16. Apparatus according to claim 11 or 12, characterized in that the top ends of the tubes (12) are carried by a common plate (20) and are closed by a film (34) of impermeable material placed on said plate, the plate being mounted in the above-mentioned enclosure (10) and being covered by a heating or cooling cap (36) associated with temperature regulation means (38) for maintaining its temperature at a value substantially equal to that of the tubes (12).

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