WO2019238591A1

WO2019238591A1 - Warming block

Info

Publication number: WO2019238591A1
Application number: PCT/EP2019/065058
Authority: WO
Inventors: Niels Stengaard Hansen
Original assignee: Nilotech
Priority date: 2018-06-12
Filing date: 2019-06-10
Publication date: 2019-12-19

Abstract

The invention regards a warming block for maintaining the temperature of one or more test tubes, comprising: - a thermal conducting unit comprising one or more tube hole(s), each hole configured for receiving a longitudinal portion of a test tube at a first end, wherein each tube hole comprises a longitudinal slit extending from the first end, configured such that the inserted test tube can be visually inspected, and - a cover configured for encapsulating the thermal conducting unit.

Description

Warming block

Field of invention

The present invention relates to a warming block for maintaining the temperature of one or more test tube(s), such as maintaining the temperature distribution and/or temperature uniformity.

Background of invention

To ensure quality control, reproducible and reliable procedures, and high yields for pursued results, test samples are advantageously stored, handled, and tested under a controlled and stable environment, such as a temperature controlled environment.

Furthermore, it may be crucial for biological samples for medical test or treatment procedures to be kept in a stable environment to avoid degradation of the sample. For example, biological samples for IVF (in-vitro fertilization) must be kept in a temperature controlled environment during the entire process, i.e. storage, and handling, to avoid degradation and thus ensuring a higher yield for favourable treatment results.

Temperature control and temperature preservation is especially challenging during sample handling. Biological samples are typically stored in a vessel, such as a test tube, culture dish, syringe, or dish. When the vessel is directly exposed to the surroundings e.g. during handling and visual inspection of the vessel content, the surrounding air affects the sample temperature, e.g. causing localized cooling and temperature gradients within the sample.

To easily and safely maintain and preserve the temperature of the sample as much as possible during handling, the vessels are typically placed in a warming block or a heater block during handling. The samples are thus mainly placed in the warming block during the handling and various procedures, which may extend for hours. The warming block may be used directly in workstations with heated tabletops, other temperated tabletops, incubators, warming plates, and incubator hoods.

US 3,109,084 [1] discloses a heater block for test tubes, integrated with a thermal- electrical control device for controlling or maintaining the temperature of the heater block. The heater block comprises viewing apertures, such that the base of the inserted tubes may be visually inspected without removing the test tube from the heater block. The viewing apertures extend through the block, thus facilitating cleaning of the heater block, and the apertures may be covered by transparent covers to prevent air flow.

To improve the reliability and yield of biological samples and test samples, such as advancing the chances of favourable fertilization results for IVF samples, there is a need for warming blocks with improved temperature control and temperature maintenance, especially during sample handling. There is further a need for warming blocks that are more safe, simple, and convenient, to handle and clean.

Summary of invention

The present invention provides a warming block with improved temperature maintenance, and improved temperature distribution and uniformity of the samples placed in the warming block. The warming block is particularly suitable for test tubes. The warming block may further consist of entirely non-electronic components, thus facilitating machine washing, and a safe, simple and convenient cleaning.

A first aspect of the invention relates to a warming block for maintaining the temperature of one or more test tubes, comprising:

- a thermal conducting unit, comprising one or more tube hole(s), each hole

configured for receiving a longitudinal portion of a test tube at a first end, wherein each tube hole comprises a longitudinal slit extending from the first end, configured such that the inserted test tube can be visually inspected, and

- a cover configured for encapsulating the thermal conducting unit.

Description of Drawings

The invention will in the following be described in greater detail with reference to the accompanying drawings.

Figure 1 shows an exploded view of an embodiment of the warming block 1 according to the present disclosure, where test tubes 4 are inserted, in this case eight test tubes. Figure 2 shows an embodiment according to the present disclosure of the assembled warming block with eight test tubes inserted.

Figure 3 shows an embodiment according to the present disclosure of the warming block without test tubes inserted. Figure 4 shows an embodiment of the cuboid thermal conducting unit in the view from the length side (A), the width side (B), and the top (C), and examples of dimensions in millimeters are included.

Figure 5 shows an embodiment of a cylindrical thermal conducting unit shown in perspective view (A), in side view (B), cross-sectional view (C), and from the top (D). Examples of dimensions and diameters (shown as“0”) in millimeters are included. Figure 6 shows an embodiment of a cylindrical warming block, where the shape of three tube holes are seen in cross-section. Examples of dimensions, diameters (shown as“0”), and curve radius (shown as“R”) in millimeters are included.

Figure 7 shows an embodiment of a cuboid warming block, where the shape of a tube hole is seen in cross-section. Examples of dimensions, diameters (shown as“0”), and curve radius (shown as“R”) in millimeters are included.

Figure 8 shows an embodiment of a cuboid thermal conducting unit from a perspective view (A), and the top (B). Examples of dimensions, and curve radius (shown as“R”) in millimeters are included.

Figure 9 shows an embodiment of the set-up for the surface temperature

measurements carried out in Example 1.

Figure 10 shows results obtained in Example 1 , showing the surface temperature at the top of the block (part of the column in darker grey), and the lost thermal energy (column in lighter grey) for a warming block according to the present disclosure with cover and without cover, and a state-of-the-art warming block (without cover).

Figure 1 1 shows results obtained in Example 1 , showing the temperature gradient inside the 14 ml tube, when inserted in a warming block according to the present disclosure, the warming block in an embodiment with and without cover.

Detailed description of the invention

The invention is described below with the help of the accompanying figures. It would be appreciated by the people skilled in the art that the same feature or component of the device are referred with the same reference numeral in different figures. A list of the reference numbers can be found at the end of the detailed description section.

Warming block

A warming block may be provided with a plurality of elongated cavities, or tube holes, open at one end, for receiving individual test tubes. The depth of the tube hole should be such that a major portion of the length of the test tube is enclosed within the block whenever the test tube is inserted or mounted therein. Thus, the warming block is adapted to control and/or maintain the temperature of the inserted part of the test and the content therein.

The warming block according to the present disclosure is particularly suitable for test tubes. Thus, the warming block is particularly efficient for maintaining and preserving the temperature of test tubes and the samples placed therein, as well as providing a particularly uniform temperature profile throughout the entire volume of the test tube and the sample placed therein.

Figure 1 shows an exploded view of an embodiment of the warming block 1 , where test tubes 4 are inserted, in this case eight test tubes. Figure 2 shows an embodiment of the assembled warming block with the eight test tubes inserted, and Figure 3 shows an embodiment of the warming block without test tubes inserted.

As seen in e.g. Figure 3, the warming block comprises a thermal conducting unit 2 and a cover 6 configured for encapsulating the thermal conducting unit. By the term “encapsulating” is meant a cover that is covering the unit, or a portion of the unit, from at least three sides, in the same manner as a hood or a cap may cover a unit. In Figure 3, the cover encapsulates the lateral sides of the unit (i.e. the width and length sides) and the top side of the unit.

As also seen in e.g. Figure 3, the thermal conducting unit comprises tube holes 3, where each hole is configured for receiving a test tube 4. An end of the longitudinal test tube is inserted into the tube hole from a first end 3a of the tube hole, placed at the top side of the thermal conducting unit.

Test tubes are characterised by a closed end and an open end. When inserting the test tube into the tube hole, the closed end of the test tube is placed near the second end 3b of the tube hole, and the open end is placed near the first end 3a of the tube hole as illustrated in Figure 1. The closed end may be a round bottom tube as illustrated in Figure 1 , and the open end may be adapted to be closed by a cap as also illustrated in Figure 1 . The open end may further comprise a neck portion, such as a neck portion for closure, e.g. a neck portion for a screw cap. The closed end of the test tube is first inserted into the thermal conducting unit, such that when the test tube is fully inserted, the closed end is adjacent to the bottom side of the unit and the open end is adjacent to the top side of the unit.

The test tubes may be inserted either before or after the cover is placed to encapsulate the thermal conducting unit. Advantageously, the top side of the cover comprises apertures 6a adapted for receiving the test tubes, and further inserting the test tubes into the tube holes of the thermal conducting unit, as illustrated in Figure 3. Figure 1 shows an embodiment, where the test tubes comprise caps, and the cover apertures are adapted for receiving the test tube, and the cap acts as a stopper for the insertion. Alternatively, the top side of the cover may comprise apertures adapted for receiving the neck portion of the test tubes, such that when the test tubes are inserted into the thermal conducting unit, and the cover subsequently placed for encapsulation, only the neck portions of the test tubes extend through the cover apertures.

Temperature stability and uniformity

During use, the test tubes are inserted into the warming block. Thus, the temperature and temperature profile of the inserted test tubes and their content, will depend on temperature stability of the warming block, and the contact area between the test tube and the warming block.

The bigger the contact area between the test tube and the warming block, the more uniform temperature is obtained of the test tube and their content. Thus

advantageously, the entire length of the test tube is inserted to be in contact with the warming block. By the entire length of the test tube is meant the portion excluding the neck portion.

In an embodiment of the disclosure, the warming block is configured for receiving the entire length of the test tube.

To further increase the contact area between the test tube and the warming block, the tube hole is advantageously adapted to have the same length and shape as the test tube. Thus, the entire surface area of the test tube may be in contact with the warming block. The closed end of a test tube is typically spherical in shape, or dome-shaped, as shown in Figure 1. Thus, advantageously, the second end of the tube hole has a spherical shape. A spherically shaped second end of the tube hole facilitates a larger contact area between a test tube and the warming block, compared to e.g. the contact area between a test tube and a conic shaped second end of the tube hole.

Figure 6 shows an embodiment of a cylindrical warming block, where the shape of three tube holes are seen in cross-section, and Figure 7 shows an embodiment of a cuboid warming block, where the shape of a tube hole is seen in cross-section.

Examples of dimensions, diameters (shown as“0”), and curve radius (shown as“R”) in millimeters are included. The spherically shaped second end of the tube holes are exemplified to have a radius curvature of respectively R6 and R8.

In an embodiment of the disclosure, the second end of the tube hole has the same shape as the closed end of a test tube. In a further embodiment, the second end of the tube hole has a spheric shape.

During sample handling, such as procedures including test tubes, it is advantageous that the samples may be continuously visually inspected by a user during the procedures. However, introducing viewing apertures to the tube holes of a warming block inherently affects the temperature stability of the warming block, as well as the temperature distribution of the test tube, since a smaller portion of the tube surface area is in thermal contact and enclosed by the warming block.

For the warming block according to the present disclosure, it was surprisingly found that a viewing aperture in the shape of a longitudinal slit, and extending from the top side of the tube hole, in combination with a cover encapsulating the thermal conducting unit, provides surprisingly temperature stability and temperature uniformity of the test tube. Embodiments of the longitudinal slits 5 are illustrated in Figures 1 -5.

By the term tube hole“slit” is meant an opening having a length and a width, where the width is significantly smaller than the diameter of the tube, such as at least 50% smaller than the diameter of the tube. The longitudinal slit facilitates sufficient visual inspection, and further facilitates visual inspection of the test tube in at least the open end. Thus, the content of the test tube may be easily observed, and for many applications, it is further especially important to be able to monitor the open end of the test tube. Observation of the sample level or liquid level within the test tube, requires visible access to at least the open end. For example, when sampling and/or providing sample to a test tube, it is necessary to be able to observe the sample level to ensure desired sample amounts and/or avoid spillage and waste of sample material.

Visual inspection of at least the open end of the test tube is also advantageous for samples prone to phase segregation. Test tube samples placed in a warming block may be subject to phase segregation, such as sedimentation of a higher density phase to the bottom, and surface flocculation of a lower density phase to the surface (e.g. scum formation). For certain biological samples, surface flocculation is a particular issue. Thus, advantageously, the slit for visual inspection extends from the top side of the tube hole.

The surprising temperature stability and uniformity of the test tubes inserted in a warming block according to the present disclosure is further described in Example 1 .

The temperature stability of the warming block, and the temperature uniformity of the inserted test tubes, further depends on at least the following features:

- The material of the thermal conducting unit,

- The material and the position of the cover,

- The geometry of the longitudinal slit,

- The warming block shape, the distribution of the tube holes, and their dimensions.

For example, the geometry of the thermal conducting unit determines the ratio between the surface area and the volume of the warming block. The higher the surface area relative to the volume, the more relative surface is exposed to the surroundings, and the lower the temperature stability and uniformity of the warming block, and the content of the warming block. Thermal conducting unit

When the test tubes are inserted in the warming block, the thermal conducting unit provides heat transfer from the inner surface of the tube hole to the test tube. Thus, the temperature and temperature distribution of the thermal conducting unit determines the heat transfer to the test tube. Thus advantageously, the temperature of the thermal conducting unit is stable and uniform, such that the heat transfer to the test tube is stable and uniform.

The internal thermal conductivity of a thermal conducting unit may ensure that the temperature distribution within the thermal conducting unit becomes quickly and efficiently uniform, when exposed to certain conditions, e.g. when the thermal conducting unit is to be tempered to a predefined temperature. For example, a thermal conducting unit may be warmed, or tempered, by being placed in contact with a thermal-electrical control device, such as placed on top of an electrical heater. Upon contacting the thermal conducting unit with the heater, the unit is warmed from the contact point, and the unit may subsequently be tempered to an essentially uniform temperature as the heat is conducted internally within the unit, and if the heat loss to the surroundings is limited.

The tempering of a thermal conducting unit to a stable and uniform temperature will depend on the material. Fast warming to a stable and uniform temperature may be obtained with a thermal conducting unit comprising aluminum (Al), such as anodized aluminum. The thermal conductivity of the aluminum material further facilitates that a fast warming may be obtained by physically contacting a single side of the unit with a heating source. For example, the base plane 2a (or bottom plane) of the unit as shown in Figure 1 , may be placed in physical thermal connection with a heating source (not shown in Figure 1 ).

In an embodiment of the disclosure, the thermal conducting unit comprises anodized aluminum, and preferably consists of anodized aluminum.

In an embodiment of the disclosure, the thermal conducting unit is adapted to be in physical thermal connection with a heating source. In a further embodiment, the thermal conducting unit has a base plane, configured to form a physical thermal connection with a heating source. By the term“physical thermal connection” is meant a contact that does not involve electronic components, such as wires. Thus, thermal transfer between the heating source and the unit occurs entirely by conduction. The efficiency and uniformity of the thermal conduction between the thermal conducting unit and the heating source, thus depends on the physical contact area between the unit and the heating source.

Advantageously, the thermal conducting unit consists of non-electronic components, such that the unit is safe to handle and safe and easy to clean and disinfect, e.g. by machine wash, and further may be operated as a simple stand-alone unit after tempering has been carried out.

In an embodiment of the disclosure, the warming block is configured for use as a stand-alone unit. In another and further embodiment, the block is configured to be machine washable. In another and further embodiment, the block consists of non electronic components.

Anodized aluminum further has the advantage of being corrosion resistant. Thus, a warming block comprising anodized aluminum is a advantageously robust enough for multiple machine washings and disinfections.

A smooth surface has a lower thermal radiation than a rough surface. Thus, a warming block comprising a smoother surface will be more temperature stable than a warming block with a rough surface. Thus, advantageously, the thermal conducting unit has a smooth surface. A smooth aluminum surface may be obtained by surface abrasion of the aluminum, e.g. by polishing. An example of polishing includes chemical polishing.

The surface roughness is typically indicated as the arithmetical mean deviation of the assessed profile (Ra). A rough surface typically has a Ra above 1 .8 pm, and will have a matte appearance. In contrast, a polished surface may obtain a Ra below 1 .8 pm.

In an embodiment of the disclosure, the thermal conducting unit comprises polished aluminum, such as chemically polished aluminum. In a further embodiment, the thermal conducting unit has a surface roughness (Ra) of below 1 .8 pm, more preferably below 1 .5 or 1.2 pm, and most preferably below 1 or 0.8 pm. The thermal conducting unit is advantageously configured to be machine washable. To further facilitate the washing and drying process of the tube holes, the second end 3b of the tube hole is advantageously fluidly connected to the base plane 2a by a bottom bore 8, as indicated in Figures 5D, 6 and 7, such that the liquids from the washing process may be easily discharged from the bottom of the tube hole and to the surroundings through the bottom bore. For example the bottom bore may be a cylindrical opening with a diameter (0) of 4 mm or 3 mm, as shown in Figures 6-7.

At the closed tube hole end, the content of the test tube has a higher relative contact area with the thermal conducting unit, since the tube contacts the unit both at the tubular sides as well as at the round bottom. Thus, the bottom bore may also contribute to improve the temperature uniformity along the longitudinal test tube section. Thus, the bottom of the tube hole, corresponding to the second end 3b of the tube hole as shown in Figure 3, advantageously comprises a bottom bore 8. For example the bore may be a cylindrical opening with a diameter of 4 mm.

Cover plate

The presence of a cover plate encapsulating the thermal conducting unit, enables surprising temperature stability and temperature uniformity of the test tubes inserted in the warming block, as further described in Example 1.

For easy and convenient insertion and removal of the test tubes from the warming block, the cover is advantageously detachably attached to the thermal conducting unit. For example, the cover may have the shape of a hood, such as an open cuboid, box, or a half open cylinder, i.e. a structure where one side is open, configured for being attached to the thermal conducting unit by a locking mechanism, such as a clip lock mechanism 7 as illustrated Figure 1 , or a pivotable locking mechanism, such as a hinge.

In an embodiment of the disclosure, the cover has the shape of a hood, an open cuboid, an open box, or a half open cylinder. In another and further embodiment, the cover is configured to be detachably attached to the thermal conducting unit by a locking mechanism, such as a clip lock mechanism. The locking mechanism facilitates that the cover is easily detached from the unit and adapted to be replaceable. Thus both the cover and the thermal conducting unit is conveniently machine washable and can be disinfected. Devices that are machine washable are particular advantageous for warming block for biological samples, where contamination from surrounding and cross-contamination between samples are detrimental.

The temperature stability of the warming block, and the temperature uniformity of the inserted test tubes, depends on the material and position of the cover relative to the thermal conducting unit. Advantageous temperature stability and uniformity may be obtained for a cover having insulating properties, such as a cover comprising a high heat resistance material, such as polycarbonate. Polycarbonate further has the advantage of being transparent, such that the test tube is easily be visually inspected through the cover. To improve the long-term durability and effect of the cover, the polycarbonate is further advantageously UV stabilized.

In an embodiment of the disclosure, the cover comprises polycarbonate, and preferably consists of polycarbonate. In a further embodiment, the cover comprises UV stabilized polycarbonate, and preferably consists of UV stabilized polycarbonate.

The thicker the cover, the better the heat resistance, however also the lower the transparency of the cover. An optimal combination of sufficient heat resistance combined with sufficient transparency may be obtained for a cover having a thickness of 2 mm.

In an embodiment of the disclosure, the cover has a thickness of between 0.5-10 mm, more preferably between 1 -5 mm or 1 -3 mm, such as a thickness of 2 mm.

To further improve the insulating effect of the cover, the cover is advantageously adapted to form an air gap to the thermal conducting unit, when the cover is encapsulating the unit, as illustrated in Figure 2. The bigger the air gap, the higher the insulating effect, however also the lower the transparency of the cover and the lower the compactness of the warming block. An optimal combination of sufficient insulation combined with sufficient transparency and compactness may be obtained for a cover forming an air gap of 1 mm to the encapsulating thermal conducting unit. In an embodiment of the disclosure, the cover is configured to form an air gap to the encapsulated thermal conducting unit. In a further embodiment, the air gap is between 0.5-5 mm, more preferably between 1 -3 mm, such as 1 , 2 or 3 mm.

Longitudinal slit

The temperature stability of the warming block, and the temperature uniformity of the inserted test tubes, depends on the geometry of the longitudinal slit. The smaller the surface area of the slit, the smaller the surface area of the tube is exposed to the surroundings, and thus the more uniform the temperature within the test tube. Also, the longer the slit, and the wider the slit, the better the visual inspection of the test tube, however also the less uniform the temperature.

Advantageously, the surface area of the slit is as small as possible. Further advantageously, the geometry of the slit is as narrow as possible, thus enabling a larger section of the test tube to be inspected, and at the same time enabling a more uniform temperature distribution.

In an embodiment of the disclosure, the surface area of the longitudinal slit exposes between 2-10% of the tube surface area, more preferably between 3-8%, most preferably 4-6%, such as 5%.

In an embodiment of the disclosure, the width of the longitudinal slit is between 10-80% of the width of the test tube diameter, more preferably between 15-50% or 20-30%, such as 21% of the width of the test tube diameter. In a further embodiment, the longitudinal slit has a width of between 1 -10 mm, more preferably between 2-5 mm, such as a width of 3 mm.

In an embodiment of the disclosure, the length of the longitudinal slit is between 50- 100% of the length of the test tube, more preferably between 70-99% or 80-90%, such as 83% of the length of the test tube. In a further embodiment, the longitudinal slit has a length of between 40-190 mm, more preferably between 50-100 or 60-80 mm, such as a length of 65 mm. Shape

Advantageous temperature stability may be obtained with a thermal conducting unit having the shape of a cuboid, cube, or cylinder. Figures 1 -4, 8 show embodiments of thermal conducting units with a cuboid shape, and Figure 5 show an embodiment of a cylindrical thermal conducting unit.

Figure 4 shows an embodiment of the cuboid thermal conducting unit in the view from the length side (A), the width side (B), and the top (C), and examples of dimensions in millimeters are included.

Figure 5 shows an embodiment of a cylindrical thermal conducting unit shown in perspective view (A), in side view (B), cross-sectional view (C), and from the top (D). Examples of dimensions in millimeters are included.

In an embodiment of the disclosure, the thermal conducting unit has a cuboid- or cylindrical shape.

Tube hole distribution

The temperature stability further depends on the geometry and distribution of the tube holes. Advantageous temperature stability may be obtained for a cylindrical thermal conducting unit comprising seven tube holes distributed as exemplified in Figure 5. .

Advantageous temperature stability may further be obtained for a cuboid thermal conducting unit comprising between six to twelve, such as eigth tube holes distributed as exemplified in Figure 4 and 8.

Dimensions

The dimensions are advantageously configured such that the temperature stability of the warming block is optimised, e.g. the ratio between the surface area and volume of the unit is optimised. Simultaneously, for safe, easy, and convenient handling of the warming block, the dimensions of the warming block are further advantageously configured such that it may be carried or moved by a single hand or two hands of a user.

In an embodiment of the disclosure, the warming block is configured for receiving test tubes having a diameter between 10-20 mm, and/or a length between 50-200 mm, such as 14 ml round bottom tubes. In a preferred embodiment, the warming block is configured for test tubes having a diameter of 17 mm.

In an another and further embodiment, the warming block is configured for receiving between 1 -20 test tubes, more preferably between 4-12 or 6-10 test tubes, and most preferably 8 test tubes.

In an embodiment of the disclosure, the warming block is having a length of between 50-150 mm, more preferably between 80-140 mm or 100-120 mm, such as a length of 1 13 mm. In a further embodiment, the warming block is having a width of between 20- 80 mm, more preferably between 40-60 mm, such as a width of 49,8 mm. In a further embodiment, the warming block is having a height of between 50-100 mm, more preferably between 65-90 mm, such as a height of 78 mm.

Example

The invention is further described by the example below.

Example 1

Temperature measurements of a warming block according to the present disclosure were carried out and compared with the performance of a state-of-the art warming block.

Materials and methods

The tested warming block was configured for 14 ml round bottom tubes for instance NUNC pn: 150268 or the similar product from FALCON pn: 352006. The block could contain up to 8 tubes, as illustrated in Figure 1.

For each tube there was a 3 mm wide and approx. 65 mm high groove, or slit, in the block, which allowed the user to see the level in each tube. The block was machined in aluminum, which optionally may be further anodized.

The block was covered by 2 mm polycarbonate, which was transparent and allowed the user to monitor the level in each tube, while immersed in the block. The

polycarbonate cover also provided insulation around the block, and especially in front of the grooves. The polycarbonate cover was further designed such that there was a thin layer of air between the aluminum block and polycarbonate cover. The air also contributed to the insulation.

Subsequent to use, the polycarbonate cover was easily removed from the aluminum block for cleaning and disinfection.

The dimension of the warming block encapsulated by the polycarbonate cover was (length x width x height, or LxWxH): 1 13 mm x 49,8 mm x 78 mm.

Test Equipment

The test instrument used was a Dostmann P795 from German manufacturer Dostmann Electronics GMBH. P795 is a reference thermometer with a stated accuracy of 0.010 Celsius (C). The instrument supports simple analog PT100 sensors and PT 100 probes with memory, where calibration date is stored in a solid-state memory inside the probe or inside the probe handle. P795 has 2 inputs which both supports simple PT100 sensors and probes with PT100 sensor and calibration memory

The type of sensor used:

The naked PT 100 sensor was a simple PT 100 thread made in thin film on a 2 mm x 10 mm ceramic plate. The sensor was mounted with 1 m 2x2 wires to allow for 4 wire connections, which gives the most precise measurement. The naked PT 100 sensor was connected to the P795 instrument.

Warming plate

The warming blocks were warmed by a 420 x 440 x 8 mm aluminum plate equipped with a 200 watts heating foil in between the aluminum plate and an underlying 10 mm insulation material. The temperature was controlled by a solid-state sensor placed right below where the heating block is placed. The control electronics was a modified Origio HG/LS controller. When placing or removing heating blocks, the temperature of the surface changes. However, upon stabilizing, the temperature of the heating plate did not vary more than 0,10 C though each measurement.

Test Method

The measurements are in theory with an accuracy of 0.010 C when using PT 100 sensors and an appropriate instrument. However, in practice the accuracy is lower due to for example:

- it is extremely difficult to calibrate an instrument to such a precision especially when measuring absolute temperatures

- a probe of a certain size may influence on the temperature of the object which is being measured.

- the probe itself may be warmed/cooled via the electric connections or encapsulation which also influences absolute readings when high precision is required

All measurements performed were relative measurements from one point to another. For instance, from the heating plate to the top of the warming block.

Surface measurements

All surface measurements were done using the naked PT100 sensor. Special care was taken to ensure good mechanical connection between the ceramic plate of the sensor and the metal to be measured. At the same time care was taken about guiding the wires to minimize the cooling effect of the wire leading away to the sensor.

It quickly became evident that it was not sufficient. The sensor did simply not measure the correct temperature. The loss to the surface was too significant. Then we continued surface measurement by placing a small piece of insulating foam on top of the sensor. The foam was approx. 2x2x2 cm. Just enough to ensure that the sensor was sufficiently isolated from the air and not too big to actually influence the temperature of the surface below. This method is useful for measuring surfaces with a good heat conductance such as aluminum. Figure 9 shows an embodiment of the set-up for the surface temperature measurements.

Measurements inside tubes

To measure temperature inside the tubes we used the naked sensor. It cannot be immersed in water without protection. This sensor is only 10 mm long so it will not lead as much heat away as the pin-sensor. Heat loss through the wires may be an issue but it turned out that the sensor covered by the finger of a rubber glove performed well even at higher levels in the tube,. We continued using the naked sensor in the rubber glove.

Results

Normalization

All presented measurements are normalized to reference point. In this case 37°C. Meaning that if we compare the surface temperature on the heating plate with the surface temperature on the top of the warming block, then the surface of the warming plate is presented to be 37°C. In practice the temperature may have been for instance 37,1 °C. In that case we subtracted 0,1 °C from all measurements. Surface measurements

All temperature tests were performed at a room temperature between 20,5°C and 21 ,3°C.

Temperatures were measured on the heated surface next to the warming block and on top of the warming block. The results can be seen in Table 1 below. For comparison, the measurements were carried out on a warming block according to the present disclosure with cover (3^rd column) and without cover (2^nd column), and a state-of-the-art warming block. Table 1. Surface measurements on a warming block according to the present disclosure with cover (3^rd column) and without cover (2^nd column), and a state-of-the-art warming block.

The height of the state-of-the-art warming block was 70 mm, and the height of the warming block according to the present disclosure was 80 mm. The the state-of-the-art warming block was further round with a diameter of 78 mm, without a cover. From Table 1 it is seen that the temperature drop was 2,45°C from bottom to top of the state-of-the-art warming block, which is a significant loss, and only 1 ,95° and 0,47°C from bottom to top for the warming block according to the present disclosure without and with a cover.

It was surprisingly seen that the uncovered warming block showed a significant temperature drop from the bottom and up to the top surface. The state-of-the-art and the warming block without cover dropped respectively 2,45 and 1 ,95 degrees C from surface, as seen in Table 1 . This was measured in a room with steady temperature around 21 °C and with very limited traffic. It was further surprisingly that the state-of-the- art has a higher drop than the disclosed warming block without cover, since the state- of-the-art is the lowest block with the smallest surface (corresponding to 80% of the surface of the disclosed block). However, the state-of-the-art is darker in color, which may have an impact as dark objects radiates more heat than shiny surfaces.

The unprotected block showed that it loses most heat to its surroundings, and it may be even worse if there is significant movement in the air around it, or if the room is colder. Protection with a polycarbonate cover ensures more stability. The surface comes under much better control.

Figure 10 illustrates the surface temperature at the top of the block (part of the column in darker grey), and the lost thermal energy (column in lighter grey) for a warming block according to the present disclosure with cover and without cover, and a state-of-the-art warming block (without cover).

In-tube measurements

From Table 1 it seems that the state-of-the-art and the warming block according to the present disclosure perform similar when it comes to heat loss at distance from the heated surface to the top. We wanted to see how this influenced the temperature gradient inside a tube. To be able to compare directly, we decided to measure the gradients inside a tube, when placed in the covered as well as uncovered warming block according to the present disclosure. We used the naked sensor, inserted into a finger of a rubber glove, inserted into the tube. The results are seen in Table 2 below.

Table 2. In-tube measurements with a warming block according to the present disclosure respectively without cover (1 ^st column) and with cover (2^nd column).

Figure 1 1 further illustrates the results of Table 2, showing the temperature gradient inside the 14 ml tube, when inserted in a warming block according to the present disclosure, the warming block in an embodiment with and without cover.

The temperatures on the surfaces were also reflected inside the tubes. It is evident that in the unprotected block (i.e. the embodiment without cover), the temperature in the liquid drops more than in the protected. It is 0,87°C from the bottom to 4 cm height in the unprotected block versus 0,53°C in the covered warming block, of. Table 2.

Based on the measurements, the difference between the protected and the

unprotected block will become even more significant the higher in the tubes. However, our measuring equipment did not allow us to make trustworthy measurements above 4 cm.

The above measurements were made over long enough periods, allowing the temperatures to stabilize in the tubes. In conclusion, the protected warming block is a more controlled solution. The polycarbonate cover both works as insulation and at the same time allow the liquid level in the tubes to be monitored.

Reference numbers

1 - warming block

2 - thermal conducting unit

2a - base plane 3 - tube hole

3a - first end of tube hole 3b - second end of tube hole

4 - test tube

5 - slit

6 - cover

6a - cover aperture

7 - locking mechanism

8 - bore

References

[1 ] US 3,109,084

Claims

1. A warming block (1 ) for maintaining the temperature of one or more test tubes (4), comprising:

- a thermal conducting unit (2) comprising one or more tube hole(s) (3), each hole configured for receiving a longitudinal portion of a test tube at a first end (3a),

wherein each tube hole comprises a longitudinal slit (5) extending from the first end, configured such that the inserted test tube can be visually inspected, and

- a cover (6) configured for encapsulating the thermal conducting unit.

2. The block according to claim 1 , configured for use as a stand-alone unit.

3. The block according to any of the preceding claims, configured to be machine washable.

4. The block according to any of the preceding claims, consisting of non-electronic components.

5. The block according to any of the preceding claims, wherein the second end (3b) of the tube hole has the same shape as the closed end of a test tube.

6. The block according to any of the preceding claims, wherein the second end (3b) of the tube hole has a spheric shape.

7. The block according to any of the preceding claims, wherein the thermal

conducting unit (2) comprises anodized, and preferably consists of anodized aluminum.

8. The block according to any of the preceding claims, wherein the thermal

conducting unit comprises polished aluminum, such as chemically polished aluminum.

9. The block according to claim 8, wherein the thermal conducting unit has a

surface roughness (Ra) of below 1 .8 pm, more preferably below 1.5 or 1 .2 pm, and most preferably below 1 or 0.8 pm.

10. The block according to any of the preceding claims, wherein the thermal conducting unit is adapted to be in physical thermal connection with a heating source.

1 1. The block according to claim 10, wherein the thermal conducting unit has a base plane, configured to form a physical thermal connection with a heating source.

12. The block according to any of the preceding claims, wherein the thermal

conducting unit has a cuboid- or cylindrical shape.

13. The block according to any of the preceding claims, wherein the cover (6) comprises polycarbonate, and preferably consists of polycarbonate.

14. The block according to any of the preceding claims, wherein the cover

comprises UV stabilized polycarbonate, and preferably consists of UV stabilized polycarbonate.

15. The block according to any of the preceding claims, wherein the cover has a thickness of between 0.5-10 mm, more preferably between 1 -5 mm or 1 -3 mm, such as a thickness of 2 mm.

16. The block according to any of the preceding claims, wherein the cover is

configured to form an air gap to the encapsulated thermal conducting unit.

17. The block according to claim 16, wherein the air gap is between 0.5-5 mm, more preferably between 1 -3 mm, such as 1 , 2 or 3 mm.

18. The block according to any of the preceding claims, wherein the cover has the shape of a hood, an open cuboid, an open box, or a half open cylinder.

19. The block according to any of the preceding claims, wherein the cover is

configured to be detachably attached to the thermal conducting unit by a locking mechanism (7), such as a clip lock mechanism.

20. The block according to any of the preceding claims, wherein the surface area of the longitudinal slit (5) exposes between 2-10% of the tube surface area, more preferably between 3-8%, most preferably 4-6%, such as 5%.

21. The block according to any of the preceding claims, wherein the width of the longitudinal slit is between 10-80% of the width of the test tube diameter, more preferably between 15-50% or 20-30%, such as 21% of the width of the test tube diameter.

22. The block according to any of the preceding claims, wherein the longitudinal slit has a width of between 1 -10 mm, more preferably between 2-5 mm, such as a width of 3 mm.

23. The block according to any of the preceding claims, wherein the length of the longitudinal slit is between 50-100% of the length of the test tube, more preferably between 70-99% or 80-90%, such as 83% of the length of the test tube.

24. The block according to any of the preceding claims, wherein the longitudinal slit has a length of between 40-190 mm, more preferably between 50-100 or 60-80 mm, such as a length of 65 mm.

25. The block according to any of the preceding claims, configured for receiving the entire length of the test tube.

26. The block according to any of the preceding claims, configured for receiving test tubes having a diameter between 10-20 mm, and/or a length between 50-200 mm, such as a diameter of 17 mm.

27. The block according to any of the preceding claims, configured for receiving between 1 -20 test tubes, more preferably between 4-12 or 6-10 test tubes, and most preferably 8 test tubes.

28. The block according to any of the preceding claims, having a length of between 50-150 mm, more preferably between 80-140 mm or 100-120 mm, such as a length of 1 13 mm.

29. The block according to any of the preceding claims, having a width of between 20-80 mm, more preferably between 40-60 mm, such as a width of 49,8 mm.

30. The block according to any of the preceding claims, having a height of between 50-100 mm, more preferably between 65-90 mm, such as a height of 78 mm.