[0001] The present invention relates to heating and more particularly to the thermal cycling
of specimen carriers.
[0002] In many fields specimen carriers in the form of support sheets which may have a multiplicity
of wells or impressed sample sites, are used for various processes
where small samples are heated or thermally cycled.
[0003] A particular example is the Polymerase Chain Reaction method (often referred to as
PCR) for replicating DNA samples. Such samples require rapid and accurate thermal
cycling, and are typically placed in a multi-well block and cycled between several
selected temperatures in a pre-set repeated cycle. It is important that the temperature
of the whole of the sheet or more particularly the temperature in each well be as
uniform as possible.
[0004] The individual samples are normally liquid solutions, typically between 1µl and 200µl
in volume, contained within individual sample tubes or arrays of sample tubes that
may be part of a monolithic plate. It is desirable to minimise temperature differentials
within the volume of an individual sample during thermal processing. The temperature
differentials that may be measured within a liquid sample increase with increasing
rate of change of temperature and may limit the maximum rate of change of temperature
that may be practically employed.
[0005] Previous methods of heating such specimen carriers have involved the use of attached
heating devices such as wire, strip and film elements and Peltier effect thermoelectric
devices, or the use of indirect methods where separately heated fluids are directed
into or around the carrier
[0006] The previous methods of heating suffer from the disadvantage that heat is generated
in a heater that is separate from the specimen carrier that is required to be heated.
[0007] The thermal energy must then be transferred from the heater to the carrier sheet,
which in the case of an attached heater element occurs, through an insulating barrier
and in the case of a fluid transfer mechanism occurs by physically moving fluid from
the heater to the sheet.
[0008] The separation of the heater from the block introduces a time delay or "lag" in the
temperature control loop. That is to say that the application of power to the heating
elements does not produce an instantaneous or near instantaneous increase in the temperature
of the block. The presence of a thermal gap or barrier between the heater and the
block requires the heater to be hotter than the block if heat energy is to be transferred
from the heater to the block. Therefore, there is a further difficulty that cessation
of power application to the heater does not instantaneously stop the block from increasing
in temperature.
[0009] The lag in the temperature control loop will increase as the rate of temperature
change of the block is increased. This can lead to inaccuracies in temperature control
and limit the practical rates of change of temperature that may be used.
[0010] Inaccuracies in terms of thermal uniformity and further lag may be produced when
attached heating elements are used, as the elements are attached at particular locations
on the block and the heat produced by the elements must be conducted from those particular
locations to the bulk of the block. For heat transfer to occur from one part of the
block to another, the first part of the block must be hotter than the other.
[0011] Another problem with attaching a thermal element, particularly a Peltier effect device,
is that the interface between the block and the thermal device will be subject to
mechanical stresses due to differences in the thermal expansion coefficients of the
materials involved. Thermal cycling will lead to cyclic stresses that will tend to
compromise the reliability of the thermal element and the integrity of the thermal
interface.
[0012] More recently our
PCT application GB97/00195 has disclosed a novel method
where the specimen carrier is metallic and direct electrical resistive heating is
applied to the metallic specimen carrier. The Specification of the aforesaid PCT application
discloses various features of heating the carrier and the whole of that disclosure
is deemed to be part of this Specification.
[0013] Now, a problem with heating samples in sample wells of such a carrier is that agitation
or stirring is sometimes desirable. The present invention aims to solve that problem.
[0014] Accordingly the invention provides a method of heating a specimen carrier in the
form of a metallic sheet and in which a matrix of sample wells is incorporated in
the sheet,
which method includes applying an alternating current to said sheet to provide heating
of the samples in the wells, and
a magnet is loosely contained within at least one well and is arranged to be agitated
by the alternating current so as to provide a stirring action during the heating.
Usually, but not necessarily always, each well will contain a magnet.
[0015] The sheet may be of silver or similar material of high thermal and electrical conductivity
and will generally have a thin section in the region of 0.3mm thickness, where the
matrix of sample wells is incorporated in the sheet. The sample wells may incorporate
samples directly or may carry sample pots or test tubes shaped to closely fit within
the wells.
[0016] The sheet may have an impressed regular array of wells to form a block and a basal
grid or perforated sheet may be attached to link the tips of the wells at their closed
ends to form an extremely rigid three-dimensional structure. In some applications
the mechanical stiffness of the block is an important requirement. Where a basal grid
is used, heating current is also passed through the metal of the grid. The basal grid
is preferably made of the same metal as the block.
[0017] While the metallic sheet may be a solid sheet of silver (which may have cavities
forming wells) an alternative is to use a metallised plastic tray (which may have
impressed wells), in which deposited metal forms a resistive heating element.
[0018] Another alternative is to electro form a thin metal tray (which again may have impressed
wells), and to coat the metal with a bio-compatible polymer.
[0019] These measures enable intimate contact to be achieved between the metallic heating
element and the bio-compatible sample receptacles. This gives greatly improved thermal
performance in terms of temperature control and rate of change of temperature when
the actual temperatures of the reagents in the wells is measured.
[0020] The plastic trays are conventionally single use disposable items. The incorporation
of the heating element into the plastic trays may increase their cost, but the reduction
in cycling time for the PCR reaction more than compensates for any increased cost
of the disposable item.
[0021] The bottom of the composite tray should be unobstructed if fan cooling is employed.
If sub-ambient cooling is required at the end of the PCR cycles, either with a composite
tray or a block, chilled liquid spray-cooling may be employed. The boiling point of
the liquid should be below the low point of the PCR cycle so that liquid does not
remain on the metal of the tray or block to impede heating. This also allows for the
latent heat of evaporation of the liquid to increase the cooling effect.
[0022] The heating current may be an alternating current supplied by a transformer system
wherein the heating power is controlled by regulating the power supplied to the primary
winding of the transformer. The sheet to be heated may be made part of the transformer
secondary circuit. The secondary winding may be a single or multiple loop of metal
that is connected in series with the sheet. By these means, the high current, low
voltage power that is required to heat the highly conductive sheet may be simply controlled
by regulating the high voltage, low current power supplied to the primary winding
of the transformer.
[0023] The transformer may comprise a toroidal core having an appropriate mains primary
winding and a single bus bar looped through the core and connected in series with
the metallic sheet to form a single turn secondary circuit.
[0024] Generally the sample wells may be conical in shape. This helps any stirring action
of each magnet within the respective well.
[0025] More specifically, in direct resistance heating using alternating current, an oscillating
magnetic field is produced at each well by the heating current. A small bar magnet,
(typically 5mm long by 1mm diameter), may be placed in each sample tube and the heating
current will cause oscillating forces to be applied to the magnet. The geometry of
the conical section of the sample tube will then constrain the bar to spin about an
axis that is not coaxial with, or normal to, the axial dimension of the bar. The stirring
action is then similar to that which would be produced by vigorously stirring each
individual tube with a manual stirring rod.
[0026] The magnets may be made of readily available materials, in particular hard magnetic
alloys such as Alnico 4. Rare earth magnets (for example iron-neodymium-boron or samarium-cobalt)
may also be used. To prevent contamination of the liquid sample, the magnet may be
given an inert coating. Such a coating may be of a bio-compatible polymer such as
polypropylene or polycarbonate, or a noble metal such as gold. A noble metal coating
has the advantage that it adds no significant volume to the magnet when applied in
a coating of sufficient thickness to ensure that the coating is not porous. When using
gold a 5µm thickness is sufficient to provide a pore-free coating, and adds a volume
of 0.08µl to the magnet.
[0027] The magnets cost much less than the typical reagent mix to be placed in a sample
tube, and may therefore be regarded as consumable items. However the magnets may clearly
be easily sorted from the waste reagents for cleaning and re-use.
[0028] The magnets may be small. In particular embodiments, for a 100µl liquid sample, a
magnet 1mm in diameter and 5mm long may be employed. Such a magnet has a volume of
3.9µl. A 0.5mm diameter by 3mm long magnet may be provided for use in smaller tubes
and would have a volume of 0.58µl. The approximate masses of these magnet examples
would be 31mg and 4.5mg respectively.
[0029] In certain embodiments, a magnet is placed in each of the wells to be agitated. In
standard practice the shape of the individual wells is conical and the magnet length
is chosen such that the long axis of the bar magnet is constrained to be within a
range of between 5 and 30 degrees of the axis of the well. Such orientation ensures
that the agitation magnet will spin eccentrically and will not jam in the well. The
diameter of the magnet should be as small as is practical, in order to minimise the
volume of the magnet. The passage of the alternating heating current through the block
gives rise to an alternating magnetic field circling the block in a plane normal to
the direction of current flow. The alternating magnetic field causes alternating forces
to be applied to the bar magnets as they try to align themselves with the magnetic
field. The conical shape of the wells constrains the movement of the magnets, which
then spin eccentrically in each well.
[0030] The effect of the eccentric spinning of the magnets is to vigorously stir the liquid
sample in each of the wells to which a magnet has been introduced. The stirring effect
almost completely eliminates any of the temperature differentials that may be observed
in a static sample during thermal cycling.
[0031] Preferably, the bottom of the sheet, even if a basal grid is attached, has an open
structure with a large surface area Such a surface is ideal for forced-air cooling.
Moreover, preferably there are no attached elements to impede free and full contact
between the metal of the sheet and moving air.
[0032] Ducting of the air may be provided to encourage even cooling effects over the extent
of the sheet. To allow for controlled cooling rates, the air movement may be under
proportional control. The control response time of a device that imparts movement
to air, for instance a mechanical element such as a fan, is slow compared to the fast
electronic control response of the heating system. The heating system may therefore
be used together with the fan to control the temperature changes of the sheet during
cooling.
[0033] The secondary winding in series with the sheet may have more than one loop through
the core of the transformer.
[0034] The power supply means and control for the heating current may be a high frequency
AC power supply permitting a reduction in the amount of material in the transformer
core.
[0035] The thermal uniformity of the sheet will be dependent on the heating power dissipation
at any point in the sheet being matched to the thermal characteristics of that point.
For instance, a point around the centre of the sheet will be surrounded by temperature
controlled metal, whereas a point at the edge of the sheet or block will have temperature
controlled metal on one side and ambient air on the other. The geometry of the sheet
may be adjusted with the aim of achieving thermal uniformity. In general practice
the geometry of sample sites or wells of a sheet or block will be a standardised regular
array. The industry standard arrays consist of 48, 96 or 384 wells in a 110 X 75mm
rectangular plate or block. These layouts are arbitrary and larger arrays of 768 and
1536 wells are appearing.
[0036] Typically, the geometric factors that may be varied comprise the thickness of the
metal from which the sheet is formed, and if a basal grid is used, the geometry of
the webs in the plane of the grid.
[0037] Embodiments of the invention will now be described by way of example with reference
to the accompanying diagrammatic drawings in which:
Figure 1 is a side elevation of a heating apparatus;
Figure 2 is a plan view of the apparatus of Figure;
Figure 3 is a side view of sample tubes incorporating magnets and located in wells
of a sheet of the heating apparatus of Figure 1;
Figure 4 is a top plan view showing the magnet location, and
Figure 5A to 5C shows a perspective, plan and side view of the block specimen carrier
of the apparatus shown in Figure 1.
[0038] A metallic sheet specimen carrier in the form of a multi-well block (1) measuring
110mm x 75mm and having 96 wells (2) disposed in a grid layout is formed in silver
nominally 0.3mm thick. This is attached to bus bars (3) of substantial cross-sectional
area. The bus bars loop once through a transformer (toroidal or square), core (4).
The core (4) has a primary winding (5) appropriate for the mains voltage employed.
The bus bars (3) also act as a structural member supporting the block (1). The transformer
primary current is controlled using a triac device (6). The triac device receives
current from an AC source and is controlled by a temperature control circuit (7) which
uses at least one fine wire thermocouple (8) soldered to a central underside region
of the block to sense the temperature of the block. The temperature control circuitry
may be operated manually or by a personal computer (9). More specifically, the heating
power may be controlled by proportional phase angle triggering of the triac (6) in
response to signals from the thermocouples (8) combined with programmed temperature
/ time information entered to describe the required thermal behaviour of the apparatus.
[0039] Cooling of the block is by means of a fan (10) mounted under the block, passing ambient
air over the protruding well forms (2), the air being directed by the enclosure in
which the block is mounted. The fan is controlled by the same temperature control
circuitry that drives the heater triac. Although not shown in detail, the airflow
is guided to give even cooling of the block (1) by means of multiple shaped air inlets
on the top, sides and bottom of the apparatus enclosure. The fan extracts air from
the inside of the enclosure. The negative pressure within the case is varied proportionally
by proportionally controlling the fan speed.
[0040] It will be appreciated that the rear surface of the block (1) has a large surface
area which is ideally suited to the dissipation of heat.
[0041] The measured performance of the example apparatus gives rates of change of temperature
in excess of 6 degrees per second and over/under shoots of less than 0.25 degrees
within the typical PCR working range of 50-100 degrees. The thermal uniformity of
the block is such that within 10 seconds of any temperature transition, even at rates
of change of temperature in excess of 6 degrees Celsius per second, the range of temperatures
that may be measured in wells around the block does not vary more than +/- 0.5 degrees
from the mean temperature.
[0042] The block (1) of the present embodiment will have an electrical resistance of around
0.00015 Ohms. To obtain the levels of heating desired, a current in the order of 1600A
is supplied to the block. The order of this required current is easily calculable
on the basis of the size of the block and the innate properties of silver. The current
in the primary winding (5) might be up to around 3A at 240V or 7A at 110V. Thus even
though high current is supplied across the block (1), the voltage across the block
remains low, say 0.25V. Further, the block (1) and bus bars (3) are isolated from
mains power and may be connected to ground to enhance safety further.
[0043] The described example uses a silver block with cavities, but metallised plastic tray
inserts, or electro formed thin metal trays, as previously described, may also be
used.
[0044] The system as described has several important advantages.
1.1 The block is heated directly with no requirement for heat transfer from an attached
heat source. This is very efficient and taken together with the very low specific
heat capacity of silver allows very rapid temperature changes.
1.2 Direct heating means that there is no thermal lag at all. Temperature control
functions are immediate so that the block may be cycled in temperature with little
or no over or undershoot. Temperature control is therefore inherently precise.
1.3 Since there are no obstructions or thermal barriers attached to the block, simple
forced-air cooling of the back of the block provides rapid and controllable cooling.
1.4 The fine wire thermocouple is soldered directly to the block so as to provide
close temperature measurement and control. Any other temperature measurement device
may be used as long as it does not introduce significant sensor lag.
1.5 The temperature distribution around the surface of the block is dependent on the
evenness of heating and the thermal conductivity of the block. The thermal conductivity
of silver is very high, and the distribution of heat .energy around the block is dependent
upon the distribution of the heating current. This may be regulated by varying the
geometry of the multi-well block. The variation in geometry will typically be achieved
by spatial variation in the thickness of the block (1) such that, (for instance),
the minimum metal thickness (of about 0.25mm), may be found at the middle of the block
surface and the maximum metal thickness (of about 0.4mm), may be found along the edges
of the block (1) parallel to the longer axis. The variations in metal thickness are
used to maintain thermal uniformity across the area of the block during thermal cycling
by compensating for the differing thermal environments experienced by different points
in the block (1).
[0045] The variations in metal thickness are produced whilst manufacturing the block by
electroforming. During the electroforming process the distribution of the electrodepositing
current is modulated such that the depositing current is higher in areas where a greater
thickness of metal is required.
[0046] The overall geometry of the block is standardised to accept liquid samples of 20-100µl
contained in either individual 200µl sample tubes or arrays of samples contained in
a 96 well microplate.
[0047] The large currents required may be easily produced and controlled since the block
becomes part of a heavy secondary circuit of the transformer. The cross-sectional
area of the winding bars is made considerably larger than the cross-sectional area
of the block so that significant heat generation only occurs in the block. The current
can be easily controlled in the primary winding (where the current is small), using
thyristors, triacs or other devices. Alternatively, the primary winding may be driven
by a high frequency, switch mode, controllable power supply. This allows the same
degree of control of the current induced in the secondary winding incorporating the
block, but the high frequency allows the use of a more compact core in the transformer.
[0048] Referring now to Figures 3 and 4, a novel stirring arrangement is shown. A sample
carrier (1)(which is equivalent to the block (1) described above) has conical cavities
(12) carrying 200µl sample tubes (13). Then, within each tube is loosely carried a
magnet (14).
[0049] Each is a small bar magnet, (typically 5mm long by 1mm diameter), which is placed
in each sample tube and the heating current is then able to cause oscillating forces
to be applied to the magnet. The geometry of the conical section of the sample tube
will then constrain the bar to spin about an axis that is not coaxial with, or normal
to, the axial dimension of the bar. The stirring action is then similar to that which
would be produced by vigorously stirring each individual tube with a manual stirring
rod.
[0050] The magnets can be made of readily available materials such as Alnico 4 and coated
with non-reactive materials such as polypropylene or PTFE or nobel metals such as
gold, for example a 5µm layer of acid hard gold plating may be used. The magnets cost
much less than the typical reagent mix to be placed in a sample tube, and may therefore
be regarded as consumable items. However the magnets may clearly be easily sorted
from the waste reagents for cleaning and re-use.
[0051] The magnets are small, 1mm diameter by 5mm long which gives a volume of 3.92µl for
use in a 200µl sample tube. A 0.5mm diameter by 3mm long magnet for use in smaller
tubes has a volume of 0.58µl. The approximate masses of these magnets are 31mg and
4.5mg respectively.
[0052] The action of the agitation magnets not only removes measurable temperature differentials
from the 100µl liquid samples used, but also increases the overall rate of heat transfer
from the block to the sample. Thus the programmed temperature/time profile is more
accurately reproduced in the thermal processing experienced by the liquid sample.
[0053] Figures 5A to 5C show the sample carrier sheet (block) (1) of Figures 1, 2 and 4
in more detail. As desribed above this metallic specimen carrier is in the form of
a multi-well block (1). This block (1) measures 110mm X 75mm and has an 8 X 12 array
of standardised conical wells 12mm deep and is formed in silver having an average
metal thickness of 0.33mm. An attached basal grid may also be provided which ties
together to exterior bottoms (101) of the wells.
[0054] It will be seen that the wells in the sheet (1) have a significant depth and thus
include side walls (102) and have an overall generally frustoconical shape. The wells
are arranged to accept and surround a significant portion of any sample tubes positioned
in the wells. This can help in the efficient transfer of heat into and/or out of samples.
A large surface area of tube is in contact with the sheet (1). Furthermore, in cooling
it will be noted that this large area of tube is in direct contact with a portion
of the sheet, ie the exterior or underside of the wells, over which ambient air is
fed.
[0055] Similar considerations also apply if samples are placed directly in the sheet rather
than in a sample tube.
[0056] It has been found that mains frequency currents eg 50Hz provide a good stirring effect.
[0057] The fact that the rear of the carrier sheet is exposed can lead to various other
advantages, in particular other apparatus may be located behind the sheet and/or access
to the rear of the sheet is easy to obtain. In a particular alternative, a method
and apparatus for realtime analysis or monitoring of reactions occurring in the sample
sites during heating and/or stirring can be provided. This may be implemented by providing
a optical probe in each sample site or well, typically this probe will be the tip
of a optical fibre which is located in an aperture towards the base of the well. The
fibre in each well will lead away from the rear (or underside) of the sheet to suitable
transmitter, receiver and analysis equipment. The monitoring will typically make use
of the fact that the fluorescing characteristics of the reagents change as the reaction
progresses. Thus an exciting frequency of light will be fed from the transmitter along
the fibres to each well. This exciting frequency will cause fluorescence in the reagents
and the emitted light will travel back along the fibres to the receiver and analysis
equipment where the fluorescence or changes in fluorescence will be analysed to give
an indication of the state of the reaction.
1. A method of heating a specimen carrier in the form of a metallic sheet (1) and in
which a matrix of sample wells (2) is incorporated in the sheet, which method includes
applying an alternating current to said sheet to provide heating of the samples in
the wells, and
wherein a magnet is loosely contained within at least one well and is arranged to
be agitated by the alternating current so as to provide a stirring action during the
heating.
2. Apparatus for thermally cycling and stirring samples, the apparatus comprising, a
specimen carrier in the form of a metallic sheet (1), in which sheet a matrix of sample
wells (2) is incorporated, means for applying an alternating current to said sheet
to provide heating of the samples in the wells, and
a magnet (14) loosely contained within at least one well which magnet is arranged
to be agitated by the alternating heating current so as to provide a stirring action
during heating.
3. A method according to claim 1 or an apparatus according to claim 2 in which each well
contains a magnet.
4. A method according to claim 1 or claim 3 or apparatus according to claim 2 or claim
3 in which the sheet is of a metal having a thermal and electrical conductivity.
5. A method according to any one of claims 1, 3 and 4 or an apparatus according to any
one of claims 2 to 4 in which the sample wells are arranged to incorporate samples
directly.
6. A method according to any one of claims 1, 3 and 4 or an apparatus according to any
one of claims 2 to 4 in which the sample wells are arranged to carry sample pots or
test tubes shaped to closely fit within the wells.
7. A method according to any one of claims 1 and 3 to 6 or an apparatus according to
any one of claims 2 to 6 in which the sample wells are conical in shape.
8. A method or apparatus according to claim 7 in which the or each magnet is a bar magnet
and the geometry of the conical section of the sample tube constrains the bar to spin
about an axis that is not coaxial with, or normal to, the axial dimension of the bar.
9. A method according to any one of claims 1 and 3 to 8 or an apparatus according to
any one of claims 2 to 8 in which the or each magnet is coated with a non-reactive
material.
10. A method according to any one of claims 1 and 3 to 9 or an apparatus according to
any one of claims 2 to 9 wherein the thickness of the material of the sheet is varies
as a function of position in the sheet in such a way as to promote even heating.
11. A method or apparatus according to claim 10 wherein the thickness of the sheet is
thinner than an average thickness towards the centre of the sheet and thicker than
an average thickness along edges of the sheet running generally parallel to the direction
in which current flows during operation.
12. A method or apparatus according to claim 10 or claim 11 in which the sheet is formed
by an electrodeposition process and the differences of thickness are acheived by controlling
the electrodeposition process.
1. Ein Verfahren zum Erwärmen eines Probenträgers in der Form einer metallischen Lage
(1), wobei eine Matrix von Probenbehältern (2) in der Lage enthalten ist, das Verfahren
beinhaltet das Anwenden eines Wechselstroms auf die Lage, um das Erwärmen der Proben
in den Behältern bereitzustellen, wobei
ein Magnet lose innerhalb mindestens eines Behälters enthalten und angeordnet ist,
um durch den Wechselstrom bewegt zu werden, um so eine Rührbewegung während des Erwärmens
bereitzustellen.
2. Vorrichtung zum thermischen Wechselbeanspruchen sowie zum Rühren von Proben, wobei
die Vorrichtung umfasst: einen Probenträger in der Form einer metallischen Lage (1),
während in der Lage eine Matrix von Probenbehältern (2) enthalten ist, und
Mittel zum Anwenden eines Wechselstroms auf die Lage, um das Erwärmen der Proben in
den Behältern bereitzustellen, sowie
einen lose innerhalb mindestens eines Behälters enthaltenen Magneten (14), der angeordnet
ist, um durch den Heizwechselstrom bewegt zu werden, um so eine Rührbewegung während
des Erwärmens bereitzustellen.
3. Ein Verfahren gemäß Anspruch 1 oder eine Vorrichtung gemäß Anspruch 2, während jeder
Behälter einen Magneten umfasst.
4. Ein Verfahren gemäß Anspruch 1 oder Anspruch 3 oder eine Vorrichtung gemäß Anspruch
2 oder Anspruch 3, wobei die Lage aus einem Metall mit einer thermischen sowie elektrischen
Leitfähigkeit besteht.
5. Ein Verfahren gemäß einem der Ansprüche 1, 3 und 4 oder eine Vorrichtung gemäß einem
der Ansprüche 2 bis 4, in denen die Probenbehälter angeordnet sind, um die Proben
direkt zu enthalten.
6. Ein Verfahren gemäß einem der Ansprüche 1, 3 und 4 oder eine Vorrichtung gemäß einem
der Ansprüche 2 bis 4, in denen die Probenbehälter angeordnet sind, um einen Probentopf
oder Testrohre aufzunehmen, die geformt sind, um genau in die Behälter zu passen.
7. Ein Verfahren gemäß einem der Ansprüche 1 und 3 bis 6 oder eine Vorrichtung gemäß
einem der Ansprüche 2 bis 6, in denen die Probenbehälter eine konische Form aufweisen.
8. Ein Verfahren oder eine Vorrichtung gemäß Anspruch 7, in denen der oder jeder Magnet
ein Stabmagnet ist und die Geometrie des konischen Abschnitts des Probenrohrs zwingt
den Stab, sich um eine Achse zu drehen, die nicht koaxial oder senkrecht zu der axialen
Dimension des Stabs ist.
9. Ein Verfahren gemäß einem der Ansprüche 1 und 3 bis 8 oder eine Vorrichtung gemäß
einem der Ansprüche 2 bis 8, in denen der oder jeder Magnet mit einem nicht reaktiven
Material beschichtet ist.
10. Ein Verfahren gemäß einem der Ansprüche 1 und 3 bis 9 oder eine Vorrichtung gemäß
einem der Ansprüche 2 bis 9, in denen die Dicke des Lagenmaterials als eine Funktion
der Position in der Lage variiert, um ein gleichmäßiges Erwärmen zu unterstützen.
11. Ein Verfahren oder eine Vorrichtung gemäß Anspruch 10, in denen die Dicke der Lage
in Richtung der Mitte der Lage dünner ist als die durchschnittliche Dicke und dicker
als eine durchschnittliche Dicke entlang den Rändern der Lage, die im Allgemeinen
parallel zu der Richtung verlaufen, in der der Strom während des Betriebs fließt.
12. Ein Verfahren oder eine Vorrichtung gemäß Anspruch 10 oder Anspruch 11, in denen die
Lage durch einen Metallabscheidungsprozess ausgebildet ist und die Unterschiede in
der Dicke durch das Steuern des Metallabscheidungsprozesses erzielt werden.
1. Procédé de chauffage d'un support d'échantillons sous forme de feuille métallique
(1) et dans lequel une matrice de cavités à échantillon (2) est incorporée dans la
feuille,
lequel procédé comprend l'étape consistant à appliquer un courant alternatif sur ladite
feuille pour assurer le chauffage des échantillons dans les cavités, et
dans lequel un aimant est contenu de façon non serrée à l'intérieur d'au moins une
cavité et est agencé pour être agité par le courant alternatif afin d'assurer une
action d'agitation au cours du chauffage.
2. Appareil destiné à cycler et agiter thermiquement des échantillons, l'appareil comprenant
:
un support d'échantillons sous forme de feuille métallique (1), dans laquelle feuille
une matrice de cavités à échantillon (2) est incorporée,
des moyens destinés à appliquer un courant alternatif sur ladite feuille pour assurer
le chauffage des échantillons dans les cavités, et
un aimant (14) contenu de façon non serrée à l'intérieur d'au moins une cavité, lequel
aimant est agencé pour être agité par le courant alternatif de chauffage afin d'assurer
une action d'agitation au cours du chauffage.
3. Procédé selon la revendication 1 ou appareil selon la revendication 2, dans lequel
chaque cavité contient un aimant.
4. Procédé selon la revendication 1 ou la revendication 3 ou appareil selon la revendication
2 ou la revendication 3, dans lequel la feuille est d'un métal possédant une conductivité
thermique et électrique.
5. Procédé selon l'une quelconque des revendications 1, 3 et 4 ou appareil selon l'une
quelconque des revendications 2 à 4, dans lequel les cavités à échantillon sont agencées
pour incorporer des échantillons directement.
6. Procédé selon l'une quelconque des revendications 1, 3 et 4 ou appareil selon l'une
quelconque des revendications 2 à 4, dans lequel les cavités à échantillon sont agencées
pour supporter des pots à échantillon ou des tubes à essai formés pour se loger de
façon serrée à l'intérieur des cavités.
7. Procédé selon l'une quelconque des revendications 1 et 3 à 6 ou appareil selon l'une
quelconque des revendications 2 à 6, dans lequel les cavités à échantillon sont de
forme conique.
8. Procédé ou appareil selon la revendication 7, dans lequel le ou chaque aimant est
un aimant en barre et la géométrie de la section conique du tube à échantillon force
la barre à tourner autour d'un axe qui n'est pas coaxial avec, ou normal à, la dimension
axiale de la barre.
9. Procédé selon l'une quelconque des revendications 1 et 3 à 8 ou appareil selon l'une
quelconque des revendications 2 à 8, dans lequel le ou chaque aimant est enduit d'un
matériau non réactif.
10. Procédé selon l'une quelconque des revendications 1 et 3 à 9 ou appareil selon l'une
quelconque des revendications 2 à 9, dans lequel l'épaisseur du matériau de la feuille
varie en fonction de la position dans la feuille de manière telle à favoriser un chauffage
uniforme.
11. Procédé ou appareil selon la revendication 10, dans lequel l'épaisseur de la feuille
est plus mince qu'une épaisseur moyenne vers le centre de la feuille et plus épaisse
qu'une épaisseur moyenne le long des bords de la feuille généralement parallèles à
la direction dans laquelle le courant passe au cours du fonctionnement.
12. Procédé ou appareil selon la revendication 10 ou la revendication 11, dans lequel
la feuille est formée par un procédé de dépôt électrolytique et les différences d'épaisseur
sont réalisées en contrôlant le procédé de dépôt électrolytique.