WO2024099551A1

WO2024099551A1 - Incubator avoiding condensation

Info

Publication number: WO2024099551A1
Application number: PCT/EP2022/081279
Authority: WO
Inventors: Daniel Brücher
Original assignee: Infors Ag
Priority date: 2022-11-09
Filing date: 2022-11-09
Publication date: 2024-05-16

Abstract

The invention relates to an incubator that comprises a chamber (11) for hosting microbiological cultures or cell cultures, a cooling unit adapted to cool an interior of the chamber (11), and a control unit (17). The control unit (17) is configured to control the cool-ing unit dependent on a value indicative of the temperature difference between the interior and an ambience of 0 the chamber (11) and to avoid condensation in the interior of the chamber (11).

Description

Incubator avoiding condensation

Technical Field

The invention relates to an incubator and a method of operating the incubator.

Background Art

In general, an incubator is a device used to grow and maintain microbiological cultures or cell cultures. Such incubator is configured to maintain optimal conditions in terms of temperature, humidity and advantageously also other conditions, such as the C02 and oxygen content of the atmosphere, or in other words, the air, inside. Incubators are essential for much experimental work in cell biology, microbiology and molecular biology. Incubators are used to culture both bacterial and eukaryotic cells.

A conventional incubator comprises a chamber with a regulated temperature. Some incubators also regulate humidity, gas composition, or ventilation within the chamber. For temperature regulation, a conventional incubator typically includes a heating and a compressor cooling, in other words, an "active cooling". Such conventional incubator is suitable for an application called "stopping reaction", in which the cultivation is stopped by strong and fast cooling, e.g. from 37 to 4°C, advantageously within 10 min.

Another application, called "switch from growth to production", includes a more gentle temperature reduction, e.g. from 37 to 32 or 28°C. In such application, the growth of cells is slowed down, in particular such that a higher yield of antibodies is achieved in the cells . In such application, avoiding contamination is crucial . Since condensation water poses a risk of contamination, condensation has to be avoided . This , however, is di f ficult to achieve with conventional incubators due to their strong cooling that cannot be fine-tuned . Further, conventional incubators , due to the cooling compressor, have the disadvantage of using excessive amounts of energy . In general , some way of cooling the chamber is necessary for the described applications , even though the interior temperature Ti is above the ambient temperature Ta, because of the heat input due to the various components , in particular electric components , of the incubator .

Disclosure of the Invention

The problem to be solved by the present invention, therefore , is to provide an incubator that is in particular suitable for the application " switch from growth to production" . It is , thus , an obj ective of the invention, to facilitate cooling while , at the same time , avoiding condensation within a chamber of the incubator . Further, according to embodiments of the invention, the incubator shall be energy-ef ficient , quiet , and/or robust .

This problem is solved by an incubator comprising the following features :

- a chamber for hosting microbiological cultures or cell cultures : Typically, the chamber is enclosed by a housing, e . g . in the shape of a cuboid, that is adapted to be closed by a door that is e . g . pivotally mounted to the housing . Advantageously, the chamber comprises smooth surfaces which may in particular be easily cleaned and kept sterile . In particular, an interior of the chamber is largely shielded from an ambience of the incubator in terms of gas , humidity and/or temperature exchange . This facilitates establishing regulated conditions , e . g . in terms of atmosphere , humidity and/or temperature , in the chamber . Advantageously, however, the chamber is not fully air-tight but configured to allow a pressure compensation with the ambience .

- a cooling unit adapted to cool an interior of the chamber : The cooling unit may comprise at least one of the following : a cooling compressor, a Peltier element , and/or a fan .

In case of the cooling unit comprising a cooling compressor, it is advantageous that the cool side of the compressor is not in direct contact with the interior of the chamber . Rather, the cooling unit may comprise an additional circuit of cooling unit or a heat trans fer element as described below in order to facilitate a smooth and gentle cooling while avoiding condensation .

Advantageously, the cooling unit comprises a heat trans fer element which comprises an inner section facing the interior of the chamber and an outer section facing the ambience of the chamber : In particular, the heat trans fer element leads through the housing of the chamber and facilitates an increased heat trans fer from the interior to the ambience of the chamber, and vice versa .

In particular, the heat trans fer element is a passive heat trans fer element , in the sense that no energy is input in the heat trans fer element for trans ferring the heat . Advantageously, the heat trans fer element comprises a heat pipe . The heat pipe , in particular, is a heat trans fer element that employs phase transition to trans fer heat between two solid interfaces . In embodiments of the incubator, the heat pipe comprises a copper envelope , and/or the heat pipe comprises water as working fluid . For the envisaged application of the incubator, it is further advantageous that an operating range of the chamber and of the heat trans fer element comprises temperatures at least between 20 and 40 ° C .

In case the cooling unit comprises a heat trans fer element , it further advantageously comprises a cooling element adapted to cool the outer section of the heat trans fer element : In particular, the cooling element is mounted on an outer side of the chamber . While it is possible to achieve a cooling of the interior of the chamber by exposing the outer section of the heat transfer element to the ambience , the cooling element advantageously comprises means to regulate a heat trans fer from the interior of the chamber to the ambience , thereby controlling a cooling power .

In an advantageous embodiment , the cooling element comprises an outer fan adapted to cool the outer section of the heat trans fer element . By controlling a rotation speed of the fan, the heat trans fer may be controlled . However, such cooling of the chamber by a heat trans fer element , in particular by a heat pipe , is physically limited to situations in which an interior temperature of the chamber is greater than an ambient temperature . In this sense , the cooling of the chamber by a heat trans fer element may be called a "passive cooling" , despite of the controllable cooling element , in particular the outer fan . This is in particular in contrast to the "active cooling" by a cooling compressor that is not functional without an energy supply .

The incubator further comprises a control unit which is configured to control the cooling unit , in particular the cooling element , dependent on a value indicative of the temperature di f ference between the interior and the ambience of the chamber and to avoid condensation in the interior of the chamber . In case of the cooling element comprising an outer fan, the control unit is configured to control the rotation speed of the outer fan . Such incubator with a "passive cooling" through a heat transfer element, in particular a heat pipe, has several advantages over conventional incubators: It is energy-efficient, in particular in comparison to cooling by a cooling compressor (roughly by a factor of 3) , or, even more so, to cooling by a Peltier element (roughly by a factor of 10) .

The incubator with a cooling element or with a Peltier element is robust and has only few moving parts. This, in turn, facilitates a long operating life and a cheap operation without too much maintenance. Further, in comparison to cooling compressors, the incubator is environmentally friendly by avoiding the use of and the refill of hazardous cooling agents.

Finally, the claimed incubator facilitates a gentle cooling of the chamber over a longer time span, e.g. gradually over more than 60 min, while strictly avoiding any condensation, which could potentially lead to a contamination in the chamber, e.g. by mould. Thus, the incubator is particularly suitable for the application "switch from growth to production" described above.

Finned elements

In an embodiment, the cooling unit comprises an inner finned element mounted on the inner section of the heat transfer element. The inner finned element is in thermal contact with the interior of the chamber and serves in particular for improving the heat transfer between the interior of the chamber and the inner section of the heat transfer element. For this purpose, typical finned elements have an increased surface area as compared to the element which they are mounted to. They may e.g. be made of aluminium.

In an advantageous embodiment, the cooling unit comprises a thermal insulation mounted on the part of the inner finned element that is located next to the heat transfer element. Such part of the inner finned element, due to its proximity to the heat transfer element is coolest and, thus, the most prone to condensation. The insulation, therefore, further helps to avoid condensation in the interior of the chamber. Advantageously, the thermal insulation comprises a water-repellent or waterproof surface. This facilitates an easier cleaning and keeping the surfaces in the interior of the chamber free of contaminants.

Alternatively or additionally, the cooling unit may comprise an outer finned element mounted on the outer section of the heat transfer element. The outer finned element is in thermal contact with the ambience of the chamber and serves in particular for improving the heat transfer between the ambience and the outer section of the heat transfer element. In case of the cooling element comprising an outer fan, the outer fan is arranged and adapted to cool the outer finned element, in particular by circulating ambient air through the outer finned element .

Sensors

Advantageously, the incubator comprises various sensors in order to be able to adapt to differing boundary conditions, such as an ambient temperature, a first (initial) temperature in the interior of the chamber and a first (initial) humidity in the interior of the chamber. Based on the values measured by the sensors, the incubator may be controlled according to different temperature profiles over time, e.g. differing in a duration of the temperature reduction or a second (target) temperature in the chamber. Such sensors advantageously comprise at least one of the following:

- an interior temperature sensor that is adapted to measure an interior temperature of the chamber, - an ambient temperature sensor that is adapted to measure an ambient temperature ,

- a humidity sensor that is adapted to measure the humidity in the interior of the chamber .

Any of these sensors advantageously is in communication with the control unit . Thus , the control unit may be configured to control the cooling unit , in particular the cooling element , and in particular a humidity control unit ( described in the following) according to measurement values received from the sensors .

Humidi ty control

In an embodiment , the incubator comprises a humidity control unit that is adapted to control the humidity in the interior of the chamber and is controllable by the control unit . Advantageously, the humidity control unit comprises a steam generator located outside the chamber . The steam generator may comprise a water reservoir and a heating element arranged at the water reservoir for generating steam . By being arranged outside the chamber, the risk of condensation in the interior of the chamber is lowered . In a second embodiment , the humidity control unit may comprise an open water bath located inside the chamber . This water bath may comprise a heating element for generating steam .

Advantageously, the humidity control unit comprises a pump for selectively pumping steam from the reservoir or ambient air into the chamber . By pumping steam into the chamber, evidently, the humidity in the chamber may be increased, whereas the humidity may be decreased by supplying ambient air into the chamber . The pump and in particular the steam generator are controllable by the control unit such that , in connection with the humidity sensor, the humidity in the chamber may be regulated to a desired value , which advantageously is below 85 % in order to avoid condensation . Further advantageous features

In an embodiment, the incubator comprises an inner fan arranged in the interior of the chamber. The inner fan is adapted to circulate air in the interior of the chamber. This ensures a homogeneous distribution of conditions, e.g. regarding temperature, humidity and gasses, which is important for the reliability of growing cells .

In an embodiment, the incubator comprises a HEPA filter for filtering the air in the interior of the chamber. HEPA is the short form of "High-Efficiency Particulate Air". By filtering the air, contaminations are removed and sterile conditions ensured. In that case, the inner fan is adapted to circulate the air through the HEPA filter.

In an embodiment, the incubator comprises shelves for static incubation of cells.

In an embodiment, the incubator comprises a shaker adapted to shake the microbiological cultures or the cell cultures in the interior of the chamber. Advantageously, the shaker is configured to shake one or more trays arranged in the chamber. The microbiological or cell cultures may be put on the tray, e.g. in a test glass or in a conical flask. Advantageously, the shaker is adapted to subject the cultures to an orbital motion. This enhances the homogeneity of the cultures and increases air supply through the liquid culture-to-air surface .

Operating method

A second aspect of the invention relates to a method of operating the incubator. As pointed out before, such method is particularly useful for performing the application "switch from growth to production". The method comprises the following steps:

(i) for a first time period, regulating the temperature in the chamber to a first temperature value (Tl) : This first time period is typically intended for the growth of the cells. It may e.g. last for several days. Advantageously, the first temperature value is between 35 and 40°C, in particular around 37°C.

(ii) over a transitional time period (tT) , reducing the temperature in the chamber to a second temperature value (T2) : Advantageously, the second temperature value is between 27 and 32°C. In typical labs with an ambient temperature between 18 and 22 °C, such second temperature value can be achieved by the above-described "passive cooling". Advantageously, the step of reducing the temperature in the chamber is conducted gradually over a transitional time period. A duration of the transitional time period may e.g. be at least 60 min, in particular at least 120 min. This ensures a smooth slowing down of the cell production rate.

(iii) for a second time period (t2) , regulating the temperature in the chamber to the second temperature value (T2) : The second time period is typically intended for the production of antibodies by the cells.

According to the invention, the temperature and/or the humidity in the chamber are regulated during the above steps (i) , (ii) and (iii) such that the humidity does not to reach 100 % and in particular does not exceed 85 %. In other words, the temperature in the chamber must, at all times, be higher than the dew point. In order to fulfil this criterion, a reduction of humidity may, or may not, be necessary depending on a first humidity value in the first time period and an intended second (target) temperature value. Often, however, a reduction of humidity will be necessary, in particular when a similar second (target) humidity value, e.g. between 75 and 85 % , needs to be achieved as the first humidity value . As described earlier, the reduction of humidity may be achieved by pumping ambient air, which is typically cooler and less humid, into the chamber .

In di f ferent embodiments , the reduction of humidity may be performed either by continuously controlling and adapting the humidity according to the above criterion over the transitional time period, or by reducing the humidity in the chamber to a transition humidity value (RHT ) before reducing the temperature in step ( ii ) above . In the latter case , the transition humidity value needs to ful fil the criterion that the second temperature value ( T2 ) is larger than a dew point of air having the first temperature value ( Tl ) and the transition humidity value (RHT ) .

With the above method of operation, a gentle temperature reduction is achieved without getting any detrimental condensation in the incubator .

In an advantageous embodiment of the incubator, the control unit is configured to control the cooling unit , in particular the cooling element , and, i f present , the humidity control unit to execute the described method .

Further, it is understood from the above that the incubator and the operating method may advantageously be used for growing or maintaining microbiological cultures or cell cultures .

Other advantageous embodiments are listed in the dependent claims as well as in the description below .

Brief Description of the Drawings

The invention will be better understood and obj ects other than those set forth above will become apparent from the following detailed description thereof . Such description makes reference to the annexed drawings, wherein :

Fig. 1 shows a schematic illustration of an incubator according to an embodiment of the invention;

Fig. 2 shows a block diagram of the control in an incubator according to an embodiment of the invention;

Fig. 3 shows a schematic time series of temperature (T) and humidity (RH) according to a method of operating an incubator according to an embodiment of the invention .

Modes for Carrying Out the Invention

Fig. 1 schematically illustrates an embodiment of an incubator 1 as described above. The incubator

I comprises a chamber 11 in which the cell cultures are put in order to grow, be maintained and/or produce e.g. antibodies. For providing optimal conditions for the cells, the atmosphere in the chamber 11 can be controlled, e.g. in terms of temperature Ti, humidity RHi and/or its gas composition.

For certain applications, such as the applications "stopping reaction" and "switch from growth to production" described above, the interior of the chamber

II needs to be cooled. Cooling of the chamber 11 is not only necessary for achieving temperatures below the ambient temperature Ta but also in a certain temperature range above the ambient temperature. This is due to the heat input of various components of the incubator 1, e.g. an inner fan 16 and a shaker motor (not shown) . In a typical lab with an ambient temperature of around 20°C, cooling may already be necessary to achieve temperatures of 30°C or 35°C and less.

A gentle cooling of the chamber 11, which does not go below the ambient temperature Ta, may be achieved by a cooling unit 13 comprising a passive heat transfer element 13c, such as a heat pipe that connects the interior of the chamber 11 with the ambience. While, alternatively, a block of thermally conducting material, e.g. copper, may be used as passive heat transfer element 13c, the effective thermal conductivity of a heat pipe may be two to three orders higher, making heat pipes the preferred passive heat transfer element.

In order to improve the thermal coupling to the interior of the chamber 11 as well as to the ambience, an inner heatsink with fins 13b and an outer heatsink with fins 13a may be mounted to the heat pipe. Further, the cooling unit 13 may comprise a cooling element 14 for regulating the cooling power, which is arranged to cool the outer section, in particular outer fins 13a. The cooling element 14 may be implemented as a fan 14, e.g. a regular computer fan, blowing air (shown as arrow in Fig. 1) with the ambient temperature Ta onto the outer fins 13a. Such cooling element 14 is advantageously controlled dependent on the temperature difference between the interior and the ambience, Ti - Ta. For this purpose, the incubator 1 advantageously comprises sensors for the interior temperature Ti and the ambient temperature Ta.

Advantageously, the incubator 1 further comprises a HEPA filter 15 arranged for filtering the air in the interior of the chamber 11. A good circulation of the air within the chamber 11 and through the HEPA filter may be achieved with an inner fan 16.

Fig. 2 shows a block diagram of an advantageous control for an incubator such as the incubator 1 of Fig. 1. The control unit 17 receives as input the values of the interior temperature Ti, the ambient temperature Ta and the interior humidity RHi, as measured by corresponding sensors, see e.g. Fig. 1. Dependent on the measured values, the control unit 17 controls the cooling element 14 and a humidity control unit 18 (not shown in Fig. 1, see the section "Humidity control" above) such that the interior temperature Ti and the interior humidity RHi follow a desired course over time.

The desired course of the interior temperature Ti is mostly given by the application that is to-be- performed, see e.g. the gentle cooling down in Fig. 3. The humidity RHi, in turn, is regulated to stay below 100 % at any time in order to avoid condensation. Since certain components in the interior of the chamber 11, such as the inner section of the heat pipe 13c, may be - and typically will be - cooler than the measured interior temperature Ti, the humidity RHi is advantageously controlled to never exceed 85 %. In this way, condensation is avoided also on the cooler components.

Fig. 3 illustrates schematic time series of the interior temperature Ti and the interior humidity RHi for a gentle cooling action as e.g. in the application "switch from growth to production". In such application, the cells, for growing, are typically subjected to a first temperature Tl, e.g. around 37°C, for a first time period tl. During the same time, the humidity is controlled to have the first humidity value RHI, e.g. between 75 and 85 %.

Then, a slow and gentle transition from the first temperature Tl to the second temperature T2 takes place, e.g. to around 32 or 28°C. Such temperature T2 is ideal for the cells to stop growing but to increase their production rate e.g. of antibodies. Such slow and gentle temperature reduction from Tl to T2 over a transitional time period tT, e.g. of one or two hours, is advantageously performed by means of the passive heat transfer element 13c since it is robust and energy-efficient.

In order to avoid condensation in the chamber 11 during the temperature reduction, the humidity in the chamber may be lowered to a transitional humidity value RHT . This may be effected by the humidity control unit 18. In case the humidity reduction is performed and finished before the temperature reduction starts, as is shown in Fig. 3, the transitional humidity value RHT is determined dependent on the temperatures T1 and T2, e.g. by the control unit 17, such as to fulfil the following criterion: The second temperature value T2 is larger than a dew point of air having the first temperature value T1 and the transition humidity value RHT. Advantageously, again, some safety margin is factored in, e.g. by requir- ing that also the second (target) humidity value RH2 does not exceed e.g. 85 %. Alternatively, the humidity may be controlled and adapted continuously over the transitional time period tT such that is does not reach 100 %, in particular not exceed 85 %, at any time. In this way, con- densation within, and thereby contamination of, the chamber 11, is reliably avoided.

Claims

1. An incubator, comprising

- a chamber (11) for hosting microbiological cultures or cell cultures,

- a cooling unit adapted to cool an interior of the chamber (11) ,

- a control unit (17) configured to control the cooling unit dependent on a value indicative of the temperature difference between the interior and an ambience of the chamber (11) and to avoid condensation in the interior of the chamber (11) .

2. The incubator of claim 1, wherein the cooling unit comprises at least one of the following:

- a cooling compressor,

- a Peltier element,

- a fan.

3. The incubator of any of the preceding claims , wherein the cooling unit comprises

- a heat transfer element (13c) comprising an inner section facing the interior of the chamber (11) and an outer section facing an ambience of the chamber (11) ,

- a cooling element (14) adapted to cool the outer section of the heat transfer element (13c) , wherein the control unit (17) is configured to control the cooling element (14) dependent on a value indicative of the temperature difference between the interior and an ambience of the chamber (11) and to avoid condensation in the interior of the chamber (11) .

4. The incubator of any of claim 3, wherein the heat transfer element (13c) comprises a heat pipe, in particular wherein the heat pipe comprises a copper envelope, and/or in particular wherein the heat pipe comprises water as working fluid.

5. The incubator of any of claims 3 to 4, wherein an operating range of the chamber

(11) and of the heat transfer element (13c) comprises temperatures at least between 20 and 40°C.

6. The incubator of any of claims 3 to 5, wherein the cooling unit comprises

- an inner finned element (13b) mounted on the inner section of the heat transfer element (13c) and in thermal contact with the interior of the chamber (11) .

7. The incubator of claim 6, wherein the cooling unit comprises

- a thermal insulation mounted on a part of the inner finned element (13b) located next to the heat transfer element (13c) , in particular wherein the thermal insulation comprises a water-repellent or waterproof surface.

8. The incubator of any of claims 3 to 7, wherein cooling unit comprises

- an outer finned element (13a) mounted on the outer section of the heat transfer element (13c) and in thermal contact with the ambience of the chamber (11) .

9. The incubator of any of claims 3 to 8, wherein the cooling element (14) comprises an outer fan adapted to cool the outer section of the heat transfer element (13c) , in particular to cool the outer finned element (13a) , wherein the control unit (17) is configured to control a rotation speed of the outer fan.

10. The incubator of any of the preceding claims, comprising

- an interior temperature sensor adapted to measure an interior temperature (Ti) of the chamber (11) , and

- an ambient temperature sensor adapted to measure an ambient temperature (Ta) , wherein the interior temperature sensor and the ambient temperature sensor are in communication with the control unit (17) .

11. The incubator of any of the preceding claims, comprising

- a humidity control unit (18) adapted to control a humidity in the interior of the chamber (11) and controllable by the control unit (17) , and

- a humidity sensor adapted to measure the humidity (RHi) in the interior of the chamber (11) and in communication with the control unit (17) .

12. The incubator of claim 11, wherein the humidity control unit (18) comprises a steam generator located outside the chamber (11) and comprising a water reservoir and a heating element arranged at the water reservoir, wherein the humidity control unit (18) comprises a pump for selectively pumping steam or ambient air into the chamber (11) , wherein the pump and in particular the steam generator are controllable by the control unit (17) .

13. The incubator of any of the preceding claims, comprising - an inner fan (16) arranged in the interior of the chamber (11) and adapted to circulate air in the interior of the chamber (11) .

14. The incubator of any of the preceding claims, comprising

- a HEPA filter (15) for filtering the air in the interior of the chamber (11) , wherein the inner fan (16) is adapted to circulate the air through the HEPA filter (15) .

15. The incubator of any of the preceding claims, comprising

- a shaker adapted to shake the microbiological cultures or the cell cultures in the interior of the chamber (11) , in particular wherein the shaker is adapted to subject the cultures to an orbital motion.

16. A method of operating the incubator of any of the preceding claims, the method comprising the following steps:

(i) for a first time period (tl) , regulating the temperature in the chamber (11) to a first temperature value ( Tl ) ,

(ii) over a transitional time period (tT) , reducing the temperature in the chamber to a second temperature value (T2) ,

(iii) for a second time period (t2) , regulating the temperature in the chamber (11) to the second temperature value (T2) , during the above steps (i) , (ii) and (iii) , regulating the temperature and/or the humidity in the chamber (11) such that the humidity does not reach 100 %, in particular does not exceed 85 %.

17. The method of claim 16, before step (ii) further comprising the step of reducing the humidity in the chamber (11) to a transition humidity value (RHT) , wherein the second temperature value (T2) is larger than a dew point of air having the first temperature value (Tl) and the transition humidity value (RHT) .

18. The method of any of claims 16 to 17, wherein the first temperature value (Tl) is between 35 and 40°C, in particular 37°C, and/or wherein the second temperature value (T2) is between 27 and 32°C.

19. The method of any of claims 16 to 18, wherein a duration of the transitional time period (tT) is at least 60 min, in particular at least 120 min.

20. The incubator of any of claims 1 to 15, wherein the control unit (17) is configured to control the cooling unit, in particular the cooling element (14) , and in particular the humidity control unit (18) to execute the method of any of claims 16 to 19.

21. A use of the incubator of any of claims 1 to 15 or 20 for growing or maintaining microbiological cultures or cell cultures.

22. A use of the method of any of claims 16 to 19 for growing or maintaining microbiological cultures or cell cultures.