Methods and systems for preparing a sample on a substrate

Abstract

A sample preparation method (100) for subsequent analysis is disclosed. The method (100) comprises dispensing (110) a sample (30) in liquid state on a substrate (14) being thermally coupled to a temperature control element (12). The method further comprises drying (120) the sample (30). The method further comprises obtaining (130) input data including at least one input parameter on ambient conditions. The method further comprises controlling (140) the temperature of the temperature control element (12) based on the obtained input data.

Description

[0001] METHODS AND SYSTEMS FOR PREPARING A SAMPLE ON A SUBSTRATE

[0002] Technical Field

[0003] The present disclosure relates to methods and systems for preparing a sample, particularly a biological sample, on a substrate for subsequent analysis of the sample.

[0004] Background

[0005] Conventional methods for analyzing biological samples such as blood or body fluids typically include two analysing techniques which may be performed manually or automated. First, an analysis of sample characteristics may be performed on the sample in a liquid state. For example, a flow cytometer using impedance, fluorescence, and / or scattered light-based measurements processes a sample of blood suspended in a fluid steam to count red blood cells, white blood cells, platelets, and to derive other parameters of a complete blood count.

[0006] Second, a sample may be examined and analysed using a dried preparation of the sample on a microscope slide. Typically, in sample preparation a "wedge1smear of the blood sample is prepared manually or automated. Manual sample preparations using wedge smears yield samples with highly variable thicknesses and distribution of blood constituents. The wedge smear often has only a single narrow band with an appropriate cell density for examination and analysis, and the location and shape of this band varies from slide to slide. In addition, due to a lack of uniformity, smear preparations often preclude absolute quantitation of sample properties for a given patient. In general, only relative proportions can be assessed within the smear itself. Existing sample preparation techniques also include methods and systems that produce a uniform, high-quality specimen. Such sample preparation methods and systems use a known volume of the sample in a highly consistent manner, which makes automation of the quantitation of sample properties directly from the specimen possible, thereby obviating sample analysis traditionally performed using flow-based systems.

[0007] Upon dispensing a blood sample on a surface of a microscope slide, it is common to dry the resulting blood sample prior to analysis. Sample cells start air-drying at a certain evaporation rate according to ambient conditions as soon as they are deposited onto the slide during dispensing. In addition to air-drying samples under ambient conditions, existing techniques include force-air drying using a fan or the like in order to control the drying rate which greatly influences the cell morphology.

[0008] There exists an ongoing need in controlling a drying process during sample preparation.

[0009] Summary

[0010] The present disclosure relates to a method for preparing a sample as defined in claim 1 and sample preparation apparatus and an automated analyser system for carrying out that method as defined in claims 11 and 15, respectively. The dependent claims depict advantageous embodiments of the present disclosure.

[0011] According to a first aspect of the present disclosure a sample preparation method for subsequent analysis is disclosed. The method comprises dispensing a sample in liquid state on a substrate. The method further comprises obtaining input data including at least one, in particular at least two, input parameter on ambient conditions. The method further comprises drying the sample. The substrate is thermally coupled to a temperature control element. The temperature of the temperature control element is controlled based on the obtained input data. By controlling the temperature of the temperature control element, the temperature of the substrate, and specifically its upper surface, can be influenced as the substrate is thermally coupled to the temperature control element. Besides other factors (i.e. other input parameters) which may be considered for controlling the temperature of the temperature control element (and for controlling the drying behaviour of the sample), the temperature of the upper surface of the substrate is decisive for the drying rate of the sample. By considering ambient conditions (e.g., ambient temperature and ambient humidity) when controlling the temperature control element (and thereby indirectly controlling the upper surface temperature of the substrate) the drying rate can be kept more closely and / or more constantly at a desired drying rate. Thereby, the preservation of the cell morphology of the sample can be improved compared to less constant / closely kept desired drying rates and / or artifacts can be avoided or at least reduced. In embodiments, the ambient conditions may comprise ambient humidity and ambient temperature. In embodiments, ambient humidity may refer to the relative humidity in the environment where the method is performed.

[0012] In embodiments, obtaining at least one, in particular at least two, input parameter on ambient conditions may comprise measuring ambient humidity and measuring ambient temperature.

[0013] In embodiments, controlling the temperature of the temperature control element may comprise applying an evaporation rate algorithm. The evaporation rate algorithm may be configured to determine a target temperature of the temperature control element based on the obtained input data.

[0014] In embodiments, obtaining the input data may include obtaining an input parameter on a desired drying behaviour of the sample. Specifically, obtaining the input data may include obtaining an input parameter on a desired drying rate and / or a desired drying time of the sample. In embodiments, obtaining the input data may include obtaining an input parameter on a desired drying time of the sample. In embodiments, obtaining the input data may include obtaining an input parameter on a volume of the sample. In embodiments, obtaining the input data may include obtaining an input parameter on the surface area of the sample. In embodiments, obtaining an input parameter on the volume of the sample may include obtaining the sample volume dispensed and / or the sample volume to be dispensed. In embodiments, obtaining an input parameter on the surface area of the sample may include obtaining a wetted radius of the sample. In embodiments, obtaining the input data may include obtaining an input parameter on a desired drying rate. The desired drying rate may be sample type specific. In embodiments, the desired drying rate may be predefined and / or selected from a look up table. In exemplary embodiments, the predefined desired drying rate may be obtained based on experimental data.

[0015] In embodiments, the desired drying time may be a predefined drying time. In embodiments, the predefined drying time may be about 10s to about 40s. Specifically, predefined drying time may be about 20s to about 30s.

[0016] In embodiments, the volume of the dispensed sample may be about 0.1 pl to about 2.0pl. Specifically, the volume of the dispensed sample may be about 0.25pl to about 1.5pl. More specifically, the volume of the dispensed sample may be about 0.5 pl to about 1.25pl. In some embodiments, the volume of the dispensed sample may be l.Opl or I l + / - up to 0.1 pl.

[0017] In embodiments, the desired drying time is selected based on the volume of the dispensed sample. In embodiments, the desired drying time may be selected from a lookup table which comprises a predefined correlation of the volume of a sample and a predefined drying time.

[0018] In embodiments, based on the determined target temperature, the temperature of the temperature control element may be adjusted. Particularly, the temperature of the temperature control element may be increased or decreased. The skilled person understands that the temperature of the temperature control element and / or the temperature of the substrate and / or the temperature of the sample (dispensed sample or sample to be dispensed) may be measured and / or surveilled. Adjusting the temperature of the temperature control element based on the determined target temperature influences the drying rate of the sample. This again has an effect on the cell morphology (e.g., structure, shape and size). In other words, an advantage of having a method to compensate for the variations of ambient conditions is that it decreases the variability in cell morphology and hence leads to higher reproducibility (and thereby consistency) and better comparable results.

[0019] In embodiments, the temperature of the temperature control element may be thermoelectrically adjusted.

[0020] In embodiments, the substrate may be thermally coupled to the temperature control element via conduction.

[0021] In embodiments, the sample may be a biological sample, particularly a biological sample comprising blood.

[0022] In embodiments, dispensing may comprise printing the sample on the substrate.

[0023] In embodiments, the sample may be dispensed on the substrate in a predefined pattern. The pattern may include at least one of a pattern of a plurality of adjacent rows, a pattern of parallel rows, a spiral pattern and / or boustrophedon pattern. In embodiments, separation between rows of the pattern during the dispensing may be between about 0.1mm and about 1.0mm, more particularly between about 0.2mm and about 0.6mm. In embodiments, the separation distance between rows may be measured from a center of a row to center of an adjacent row (e.g., needle movement in y-direction).

[0024] In embodiments, drying does not include force-air drying. More specifically, the whole method does not include force-air drying, particularly not during dispensing and drying the sample.

[0025] In embodiments, the sample preparation method may be carried out in an automated analyser system. In some embodiments, the sample may be prepared for subsequent automated analysis in the automated analyser system.

[0026] In a second aspect, a sample preparation apparatus for use in an automated analyser system is disclosed. The sample preparation apparatus comprises a temperature control element, a substrate, a sample applicator, and a control unit. The substrate is thermally coupled to the temperature control element. The sample applicator is configured to dispense a sample on the substrate. The control unit configured to control the temperature of the temperature-control element based on input data including at least one input parameter on ambient conditions.

[0027] In embodiments, the sample preparation apparatus may be configured to perform the method according to the first aspect.

[0028] In embodiments, the sample preparation apparatus may further comprise a temperature- controlled support. The temperature controlled support may comprise the temperature control element. The substrate may be arranged on the temperature-controlled support.

[0029] In embodiments, the temperature control element may comprise a thermoelectric element. The thermoelectric element may be a Peltier element.

[0030] In embodiments, the temperature control element may be configured to conductively control a temperature of the substrate. In embodiments, the substrate may be a slide. Particularly, the substrate may be a microscope slide. In embodiments, the slide is made of glass or plastic material. Alternatively, any other suitable slide material which is configured to conduct heat with the temperature control element, e.g., a ceramic or metallic slide may be used.

[0031] In embodiments, the substrate may have a thickness of about 0.1mm to about 2.0mm, specifically about 0.5mm to about 1.5mm, for instance 1mm.

[0032] In embodiments, the sample preparation apparatus may further comprise a temperature sensor configured to measure ambient temperature. In embodiments, the sample preparation apparatus may further comprise a humidity sensor configured to measure ambient humidity. In embodiments, the humidity sensor may be arranged close to the dispensing location. For instance, the humidity sensor may be arranged at the sample applicator or, if present, at the temperature-controlled support.

[0033] In embodiments, the sample preparation apparatus may further comprise a wall protection arranged on lateral sides of the substrate. The wall protection may be arranged and configured to protect the sample from lateral air streams. Thereby, the slide upper surface can be protected from air streams, for instance lateral air streams, which negatively influence the cell morphology.

[0034] In a third aspect, an automated analyser system for analysing a prepared sample is disclosed. The automated analyser system comprises the sample preparation apparatus according to the second aspect. The automated analyser system further comprises a sample analysis apparatus configured to analyse the sample prepared by the sample preparation apparatus.

[0035] Overall, the present inventors have found that common drying techniques, particularly force air drying, negatively affects the morphology of sample cells. Furthermore, when using merely air drying, the morphology of the sample cells vastly depend on and vary with varying ambient conditions. By using the disclosed temperature control element while at least considering ambient conditions, the temperature of the substrate, and specifically its upper surface, can be influenced as the substrate is thermally coupled to the temperature control element. Besides other factors (i.e. other input parameters) which may be considered for controlling the temperature of the temperature control element (and for controlling the drying behaviour of the sample), the temperature of the upper surface of the substrate is decisive for the drying rate of the sample. By considering ambient conditions (e.g., ambient temperature and ambient humidity) when controlling the temperature control element (and thereby indirectly controlling the upper surface temperature of the substrate) the drying rate can be kept more closely and / or more constantly at a desired drying rate. Thereby, the cell morphology of the sample can be maintained and / or artifacts can be avoided or at least reduced. In other words, an advantage of having a method to compensate for the variations of ambient conditions is that it decreases the variability in cell morphology and hence leads to higher reproducibility (and thereby consistency) and better comparable results. Furthermore, the results are more consistent over various areas of the sample and the disclosed solution may result in cost reduction compared to, for instance, solutions using a climate chamber.

[0036] The term “sample applicator” as used herein refers to a device that dispenses a sample onto a substrate. Typically, although not always, sample applicators include a fluid conduit for dispensing fluid samples. Sample applicators can include pipettes, needles, and tubes, for example. In embodiments, the sample applicator may move relatively to the substrate or the support on which the substrate is placed. For instance, the sample applicator may be moved while the substrate or the support on which the substrate is placed may remain in a fixed location. In another embodiment, the substrate or the support on which the substrate is placed may be moved relatively to the fixed sample applicator. In yet another embodiment, both the applicator and the substrate or the support on which the substrate is placed may be absolutely moved and moved relatively to each other.

[0037] The term “sample” can be understood as a solution, a suspension, a liquid, or another type of fluid sample dispensed by the sample applicator onto a surface of the substrate. A sample can be a biological specimen such as blood, for example. In other examples, a sample may be a non-biological specimen such as a reagent, a QC material or a calibrator. In embodiments the “sample in liquid state” may also be referred to as “liquid sample” or “sample to be dried”. After drying, a sample may also be referred to as a “dried sample”.

[0038] “Drying the sample” may be understood as evaporating liquid phase (e.g. water content) from the sample. The present disclosure relies on controlled air drying by influencing the temperature of the sample via controlling the temperature control element and / or the substrate thermally coupled thereto. In embodiments, drying the sample may include evaporating liquid phase from the sample until the liquid phase in the sample is 20% or less, specifically 10% or less, and more specifically 5% or less. In embodiments, drying the sample may include evaporating liquid phase from the sample at least until the liquid phase in the sample is between 1% to 30%, specifically 5% to 20%, more specifically 10% to 15%.

[0039] The term “substrate” is a member onto which a sample can be dispensed. Typically, but not always, substrates have a planar receiving surface onto which the sample can be dispensed by the sample applicator. An example substrate is a microscope slide, or any other reflective material capable of supporting a sample.

[0040] The term “upper surface” of the substrate corresponds to the substrate surface closest to the sample applicator. The term “lower surface” of the substrate corresponds to the substrate surface opposite to the upper surface. The “thickness” of the substrate corresponds to a maximum dimension of the substrate measured between the upper and lower surfaces in a direction perpendicular to the plane of the upper surface.

[0041] Brief Description of the Drawings

[0042] Other characteristics will be apparent from the accompanying drawings, which form a part of this disclosure. The drawings are intended to further explain the present disclosure and to enable a person skilled in the art to practice it. However, the drawings are intended as non-limiting examples. Common reference numerals on different figures indicate like or similar features.

[0043] FIG. 1 schematically depicts the sample preparation method according the first aspect of the present disclosure;

[0044] FIG. 2 schematically depicts the automated analyser system according to the third aspect of the present disclosure which includes the sample preparation apparatus according the second aspect of the present disclosure;

[0045] FIG. 3 depicts an example correlation of ambient conditions and desired temperature of the substrate. Detailed Description

[0046] Embodiments of the method and system for preparing a sample on a substrate according to the present disclosure will be described in reference to the drawings as follows.

[0047] Fig- 1 shows a schematic sample preparation method 100 according to the first aspect of the present disclosure. The sample preparation method 100 is particularly suited for subsequent analysis of the prepared sample. The method 100 comprises four main steps 110, 120, 130, and 140. The steps need not be performed in the depicted successive order, but may be performed in a different order and / or at least partially simultaneously.

[0048] Step 110 represents dispensing a sample 30 in liquid state on a substrate 14. As will be explained further below with respect to Fig. 2, the substrate 30 is thermally coupled to a temperature control element 12. In some embodiments, the substrate 14 may be for instance thermally coupled to the temperature control element 12 via conduction. Such a thermal coupling may also include distances up to 0.5mm, preferably up to 0.3mm, and most preferably up to 0.2mm between the substrate 14 and the temperature control element 12. The method 100 of present disclosure may particularly use biological samples comprising blood. It should be understood that other samples, particularly biological samples may be used (e.g. other body fluids than blood, for instance cerebrospinal fluid). The sample 30 may be dispensed as a single smear or multiple smears, e.g. in a pattern. The smear may, for instance be applied in a drop-like or cylinder-like form. It should however be understood that the sample 30 may be dispensed on the substrate 14 in another form, e.g. in a predefined pattern. For instance, the sample 30 may be dispensed in a pattern including at least one of a pattern of a plurality of adjacent rows, a pattern of parallel rows, a spiral pattern and / or boustrophedon pattern. In some embodiments, a separation between rows of the pattern during the dispensing may be between about 0.2 mm and about 0.6 mm. In embodiments, the sample 30 may be dispensed on the substrate 12 using a sample applicator 16. In some embodiments, dispensing 110 may comprise printing the sample 30 on the substrate 14. In embodiments, dispensing 110, particularly printing, may comprise translating the sample applicator 16 in x- and / or y-direction (see, e.g. Fig. 2) relative to the substrate 14 while dispensing the sample 30 through the sample applicator 16 onto the substrate 14. A height between a dispensing tip of the sample applicator 16 and the substrate 14 (e.g. in z-direction as shown in Fig. 2) may be chosen to create a desired layer thickness of cells (for instance, a monolayer of cells of the sample). In some example embodiments, the volume of the dispensed sample 30 may be about 0.1 pl to about 2.0pl. Specifically, the volume of the dispensed sample 30 may be about 0.25pl to about 1.5pl. More specifically, the volume of the dispensed sample 30 may be about 0.5 l to about 1.25pl. In some embodiments, the volume of the dispensed sample may be l.Opl or Ipl + / - up to 0.1 pl.

[0049] Step 120 represents drying the sample 30.

[0050] Step 130 represents obtaining input data including at least one input parameter on ambient conditions.

[0051] Step 140 represents controlling the temperature of the of the temperature control element based on the obtained input data.

[0052] As explained above, the liquid sample 30 may start drying, particularly air-drying, at a certain evaporation rate according to ambient conditions as soon as the liquid sample 30 is dispensed, e.g. from a sample applicator 16. By controlling, e.g. regulating, the temperature of the temperature control element 12 based on ambient conditions, the evaporation rate of the fluid sample 30 can be influenced and / or controlled. In other words, a controlled air-drying at a desired evaporation rate (or drying rate) can be achieved. This is possible because the temperature control element 12 is thermally coupled to the substrate 14. That means the temperature of the substrate 14, particularly the temperature on its upper surface, can be controlled via controlling the temperature of the temperature control element 12. As the fluid sample 30 is dispensed on the upper surface of the substrate 14, the temperature of the fluid sample 30 (which is substantially the same as the temperature of the upper surface of the substrate 30) can be adjusted to achieve a desired evaporation rate. In very advantageous embodiments, drying 120 does not include force-air drying. Force-air drying should be understood as generating a fluid (e.g. air) stream which has a relative movement with respect to the dispensed sample, e.g. using a fan. More specifically, the whole method 100 does not include force-air drying, particularly not during dispensing 110 and drying 120 the fluid sample 30. This is particularly advantageous because the present inventors found out that force-air drying negatively affects the morphology of sample cells. In other words, the controlled air- drying approach via using a temperature control element 12 may improve the cell morphology of the dried sample 30 compared to alternative drying processes which rely on forced air drying and / or less constant temperature control.

[0053] Obtaining 130 input data including at least one, in particular two, input parameter on ambient conditions may comprise obtaining input data including input parameters on ambient humidity and ambient temperature. Particularly, obtaining input parameters on ambient conditions may comprise measuring ambient humidity and measuring ambient temperature.

[0054] In other words, ambient conditions may comprise ambient humidity and ambient temperature. In embodiments, ambient humidity may refer to the relative humidity in the environment where the method is performed.

[0055] Besides input data on ambient conditions, obtaining 130 input data may further include obtaining one or more input parameters on the sample 30. Particularly, one or more input parameters on the drying behaviour of the sample 30 may be obtained. In some embodiments, the one or more input parameters on the drying behaviour of the sample 30 may be determined in tests before performing the sample preparation method 100.

[0056] In embodiments, obtaining 130 input data may include obtaining an input parameter on a desired drying time of the sample 30. In embodiments, obtaining 130 the input data may include obtaining an input parameter on a volume of the sample 30. In embodiments, obtaining 130 the input data may include obtaining an input parameter on the surface area of the sample 30. In embodiments, obtaining an input parameter on the volume of the sample 30 may include obtaining the sample volume dispensed and / or the sample volume to be dispensed. In embodiments, obtaining an input parameter on the surface area of the sample 30 may include obtaining a wetted radius of the sample 30.

[0057] In embodiments, obtaining 130 the input data may include obtaining an input parameter on a desired drying rate. The desired drying rate may be sample type specific. In embodiments, the desired drying rate may be predefined, calculated and / or selected from a lookup table. The look up table may comprise a predefined correlation of the sample type and a predefined drying rate. In examples, the desired drying rate may be obtained based on experimental data. For instance, it may be tested which drying rate has the least negative effect on cell morphology. The least negative effect on cell morphology may, for instance, be determined based on a test which leads to a maximum of red blood cells (RBC) with central pallor. Central pallor of RBCs refers to the pale area in the center of an RBC that is visible when the cell is stained and observed under a microscope.

[0058] In embodiments, the desired drying time may be a predefined drying time. In embodiments, the predefined drying time may be about 10s to about 40s. Specifically, predefined drying time may be about 20s to about 30s. In embodiments, the desired drying time may be selected based on the volume of the dispensed sample 30. In embodiments, the desired drying time may be selected from a lookup table. The lookup table may comprise a predefined correlation of the volume of a sample and a predefined drying time.

[0059] Controlling 140 the temperature of the temperature control element 12 may particularly comprise applying an evaporation rate algorithm. The evaporation rate algorithm may be configured to determine a target temperature of the temperature control element 12 based on the obtained input data. In embodiments, based on the determined target temperature, the temperature of the temperature control element 12 may be adjusted. Particularly, the temperature of the temperature control element 12 may be increased or decreased. The skilled person understands that the temperature of the temperature control element 12 and / or the temperature of the substrate 14 and / or the temperature of the sample 30 (dispensed sample or sample to be dispensed) may be measured and / or surveilled. Adjusting the temperature of the temperature control element 12 based on the determined target temperature influences the drying rate of the sample 30. This again has an effect on the cell morphology (e.g., structure, shape and size). In other words, an advantage of having a method to compensate for the variations of ambient conditions is that it decreases the variability in cell morphology and hence leads to higher reproducibility (and thereby consistency) and better comparable results. In some embodiments, the temperature of the temperature control element 12 may be thermoelectrically adjusted. By controlling 140 the temperature of the temperature control element 12, the temperature of the substrate 14, and specifically its upper surface, can be influenced as the substrate is thermally coupled to the temperature control element 12. Besides other factors (i.e. other input parameters) which may be considered for controlling the temperature of the temperature control element 12 (and for controlling the drying behaviour of the sample 30), the temperature of the upper surface of the substrate 14 is decisive for the drying rate of the sample 30. By considering ambient conditions (e.g., ambient temperature and / or ambient humidity) when controlling the temperature control element 12 (and thereby indirectly controlling the upper surface temperature of the substrate 14) the drying rate can be kept more closely and / or more constantly at a desired drying rate. Thereby, the cell morphology of the sample 30 can be improved and / or artifacts can be avoided or at least reduced.

[0060] In further detail, the evaporation rate algorithm may combine one or more evaporation related formulas. For instance, evaporation time formulas as follows in formula 1.1 and / or formula 1.2 may be considered in the evaporation rate algorithm as well as a concentration gradient formula based on Ideal Gas Law and Buck equation (see, formulas 2.1 and 2.2):

[0061] Formula 1.1:

[0062] Knowing the initial volume Vo, the evaporation time can be calculated:

[0063] Formula 1.2:

[0064] Values used in formulas 1.1, 1.2, and 2.1 in [Si-units]: m mass transfer, i.e., evaporation rate [kg / s] tevapevaporation time [s]

[0065] J: local mass flux [kg / (m2s1)] n: normal vector

[0066] A: free surface area [m2]

[0067] Vo: initial volume [m3] rw: wetted radius [m] pw: density [kg / m3]

[0068] Dv: vapour diffusivity of water in the air [m2 / s]

[0069] Ac = (Coo - Ci): concentration gradient [kg / m3]

[0070] Considering the following formula 2.1 and / or formula 2.2, the evaporation rate algorithm is capable of determining a target temperature based on the obtained input data to achieve a desired drying rate and / or drying time (for a specific volume and surface):

[0071] Formula 2.1: Values used in formula 2.1 in [Si-units]:

[0072] M: molar mass of water [g / mol]

[0073] R: universal gas constant [J / mol K]

[0074] (p relative humidity [%]

[0075] T«>: temperate at infinity(air) [°C]

[0076] Ti: interfacial temperature (surface- substance) [°C] ps,oo: saturation vapour pressure at infinity (air) [Pa] ps,i: interfacial saturation vapour pressure (liquid-air) [Pa]

[0077] Considering the following formula 2.2 (Buck equation) pressures ps. / and ps,i may be determined:

[0078] Formula 2.2: p = 0.61121

[0079] Values used in formula 2.1 in [Si-units]: p: pressure [kPa]

[0080] T : temperature [°C]

[0081] It should be understood, that sample type specific properties are known to the method and system for preparing the sample 30. Further explanations with regard to the above formulas as such are omitted at this point, as these formulas should be known to the skilled person (see, e.g., “Comparison of drop evaporation models on hot surface - Adria Gonzalez Esteve”).

[0082] Example method 1

[0083] To further explain the functioning of the described sample preparation method 100, one example of how it may be performed is given in this paragraph. As described a liquid sample 30 may be dispensed 110 on the substrate 14, the substrate 14 being thermally coupled to the temperature control element 12. The sample type may for instance be blood of a known volume Vo and may be dispensed in such a technique that a wetted radius rwis also known. As soon as the sample 30 is dispensed it starts air-drying at a certain evaporation rate m. In order to dry 120 the sample 30 at a desired drying rate m, i.e. to control the air-drying process, the temperature of the liquid sample 30 on the substrate 14 is controlled via controlling the temperature of the temperature control element 12. As can be seen in formula 1.1 above, the drying rate m is dependent on the concentration gradient Ac. As can be seen in formulas 2.1 and 2.2 Ac again depends on ambient conditions (ambient humidity ; ambient temperature T«>) and the temperature Ti of the sample 30 which is directly affected by the temperature Ti of the temperature control element 12. Therefore, input data including at least one input parameter on ambient conditions is obtained 130. Based on the input data, the temperature of the temperature Ti control element 12 is controlled 140 in order to dry 120 the sample 30 at the desired drying rate m. Alternatively, to desired drying rate m, a desired drying time tevap may be considered using formula 1.2 above in order to dry 120 the sample 30.

[0084] In that regard, Fig. 3 shows an exemplary correlation of ambient conditions (ambient temperature “air”; ambient humidity “RH”) and temperature of the substrate 14 (“slide”). As explained above, the temperature of the substrate 14 is considered equivalent to the temperature of the temperature control element 12 and to the temperature of the sample 30 dispensed on the substrate 14. Various circular datapoints are shown for exemplary conditions and the desired substrate temperature in order to achieve a desired drying rate. In environments where the ambient humidity is higher and / or the ambient temperature is lower, the dispensed sample dries more slowly. In these cases, the temperature of the temperature control element 12 may be increased (e.g., the temperature control element 12 may heat the sample 30). Conversely, where the ambient humidity is lower and / or the ambient temperature is higher, the dispensed sample dries more rapidly. In these cases, the temperature of the temperature control element 12 may be decreased (e.g., the temperature control element 12 may cool the sample 30). Two exemplary conditions are highlighted in Fig. 3. In dashed lines, the ambient temperature is about 15°C and the ambient humidity is about 30%. Compared to the surroundings, the substrate 14 shall be heated up to a temperature of little below 22°C. Conversely, when the ambient temperature is about 30°C and the ambient humidity is about 30%, the substrate 14 shall be cooled down to a temperature of little above 27°C (see, continuous lines). The correlation table of Fig. 3 should only be seen as an example of how to implement the sample preparation method without necessarily using the evaporation rate algorithm described above. For instance, based on the obtained ambient conditions, a target temperature of the temperature control element 12 may be obtained from a lookup table, e.g. a correlation table as that depicted in Fig. 3.

[0085] It should be understood that the temperature of the temperature control element 12 may be regulated several times during the method, particularly during the whole method. Particularly, the evaporation rate algorithm may iteratively determine a target temperature and / or adjust the temperature of the temperature control element 12 according to the target temperature over time. As will be explained further below, the sample preparation method 100 may be carried out in an automated analyser system 1. In some embodiments, the sample 30 may be prepared for subsequent automated analysis in the automated analyser system 1.

[0086] With respect to very schematic Fig. 2, the sample preparation apparatus 10 for use in an automated analyser system 1 according to the second aspect of the present disclosure will be explained. The sample preparation apparatus 10 comprises a temperature control element 12, a substrate 14, a sample applicator 16, and a control unit 18. The substrate 14 is thermally coupled to the temperature control element 12. The sample applicator 16 is configured to dispense a sample 30 on the substrate 14. In the example of Fig. 2, the sample applicator 16 has already dispensed three drop-like samples 30 and is about to dispense a fourth sample 30. The control unit 18 is configured to control the temperature of the temperature-control element 12 based on input data including at least one input parameter on ambient conditions.

[0087] Particularly, the sample preparation apparatus 10 may be configured to perform the method 100 according to the first aspect. In that respect, the control unit 18 is further configured to obtain 130 the input data.

[0088] As shown in Fig. 2, the sample preparation apparatus 10 may further comprise a temperature- controlled support 13. The temperature controlled support 13 may comprise the temperature control element 12. The substrate 14 may be arranged on the temperature-controlled support 13. In the example configuration according to Fig. 2, the temperature control element 12 may be embedded in the temperature controlled support 13. Thereby, an upper side of the temperature control element 12 may be unobstructed such that the substrate 14 can be placed directly on the temperature control element 12. Specifically, a lower surface of the substrate 14 is in contact with an upper surface of the temperature-controlled support 13, more specifically with an upper surface of the temperature control element 12, such that both surfaces are conductively coupled. Specifically, the temperature of the upper surface of the temperature- controlled support 13 may be controlled by the control unit 18. In embodiments, the temperature-controlled support 13 may be a temperature-controlled metal plate which can be heated and / or cooled. Particularly, the temperature control element 12 may comprise a thermoelectric element. The thermoelectric element may, for instance, be a Peltier element. The temperature control element 12 may be configured to conductively control a temperature of the substrate 14. Specifically, the temperature control element 12 may be configured to conductively control the temperature of an upper surface of the substrate 14, particularly the entire upper surface of the substrate 14. More specifically, the temperature control element 12 is configured to conductively control the upper surface of the substrate 14 at a substantially uniform temperature. In some embodiments, the temperature control element 12 is configured to conductively control the temperature of selected regions of the upper surface of the substrate 14 at a uniform temperature or at different temperatures.

[0089] In embodiments, the substrate 14 may be a slide. Particularly, the substrate 14 may be a microscope slide. In embodiments, the slide may be made of glass material or plastic material. Alternatively, any other suitable slide material which is configured to conduct heat with the temperature control element 12, e.g., a ceramic or metallic slide may be used.

[0090] In embodiments, the substrate 14 may have a thickness of about 0.1mm to about 2.0mm, specifically about 0.5mm to about 1.5mm.

[0091] In embodiments, the sample preparation apparatus 10 may further comprise a temperature sensor I la configured to measure ambient temperature. In embodiments, the sample preparation apparatus 10 may further comprise a humidity sensor 11b configured to measure ambient humidity. The sensor I la, 11b may be connected (wired or wireless) to the control unit 18. In other words, the measured ambient temperature and / or the measured ambient humidity may be used as input data / input parameters for the control unit 18, specifically for applying the evaporation rate algorithm. In embodiments, additionally or alternatively, the control unit 18 may obtain input data on ambient temperature and / or input data on ambient humidity from a system / sensors external to the sample preparation apparatus 10.

[0092] The control unit 18 is further connected to the temperature control element 12 to control the temperature of the temperature control element 12. The sample preparation system 10 may further comprise a control unit 17 for controlling the sample applicator 16. As indicated by the double arrow, the control unit 17 may be configured to control a movement of the sample applicator 16 relative to the substrate 14. Although the double arrow is only directed in opposing x-directions, it should be understood that the sample applicator 16 may be moved in x-,y- and / or z-direction. In some embodiments, alternatively or additionally, the temperature-controlled support 13 may be moved in x-,y- and / or z-direction. For instance, the temperature-controlled support 13 may have a stage function or may be coupled to a movable stage. The control unit 18 may be configured to control movement of the stage.

[0093] As further shown in Fig. 2, the control unit 18 for obtaining input data and for controlling the temperature control unit 12, and the control unit 17 for controlling the sample applicator 16 may be communicatively coupled (wired or wireless). For instance, the control units 17, 18 may exchange data on location, temperature and / or sample details (e.g., sample volume dispensed and / or sample volume to be dispensed and / or temperature of the sample being dispensed and / or temperature of the sample to be dispensed). In some embodiments, the control units 17 and 18 may be implemented as one control unit.

[0094] In some embodiments, the sample preparation apparatus 10 may further comprise a wall protection arranged on lateral sides of the substrate 14 (not shown in the figures for clarity reasons). The wall protection may be arranged and configured to protect the sample 30 from lateral air streams. Thereby, the upper surface of the substrate 14 (and thus the sample 30) can be protected from lateral air streams which negatively influence the cell morphology.

[0095] With further regard to Fig. 2, an automated analyser system 1 for analysing a prepared sample is disclosed. The automated analyser system 1 comprises the sample preparation apparatus 10 according to the second aspect and as explained before. The automated analyser system 1 further comprises a sample analysis apparatus 20 configured to analyse the sample prepared by the sample preparation apparatus 10.

[0096] Although the present invention has been described above and is defined in the attached claims, it should be understood that the invention may alternatively be defined in accordance with the following embodiments: A sample preparation method (100) for subsequent analysis, the method (100) comprising: dispensing (110) a sample (30) in liquid state on a substrate (14) being thermally coupled to a temperature control element (12); drying (120) the sample (30); obtaining (130) input data including at least one input parameter on ambient conditions; controlling (140) the temperature of the temperature control element (12) based on the obtained input data. The sample preparation method (100) of embodiment 1, wherein the ambient conditions comprise ambient humidity and ambient temperature. The sample preparation method (100) of any one of the preceding embodiments, wherein obtaining (130) input parameters on ambient conditions comprises measuring ambient humidity and measuring ambient temperature. The sample preparation method (100) of any one of the preceding embodiments, wherein controlling (140) the temperature of the temperature control element (12) comprises applying an evaporation rate algorithm configured to determine a target temperature of the temperature control element (12) based on the obtained input data. The sample preparation method (100) of any one of the preceding embodiments, wherein obtaining (130) the input data further includes obtaining an input parameter on a desired drying time of the sample (30) and / or an input parameter on a volume of the sample (30) and / or an input parameter on the surface area of the sample (30). The sample preparation method (100) of embodiment 5, wherein the desired drying time is a predefined drying time, particularly wherein the predefined drying time is about 10s to about 40s, specifically about 20s to about 30s. 7. The sample preparation method (100) of any one of embodiments 5 or 6, wherein the volume of the dispensed sample (30) is about 0.1 pl to about 2.0pl, specifically about 0.25pl to about 1 ,5pl, more specifically about 0.5pl to about l.Opl.

[0097] 8. The sample preparation method (100) of any one of embodiments 5 to 7, wherein the desired drying time is selected based on the volume of the dispensed sample.

[0098] 9. The sample preparation method (100) of any one of embodiments 4 to 8, wherein, based on the determined target temperature, the temperature of the temperature control element (12) is adjusted, particularly wherein the temperature of the temperature control element (12) is increased or decreased.

[0099] 10. The sample preparation method (100) of any one of the preceding embodiments, wherein the temperature of the temperature control element (12) is thermoelectrically adjusted.

[0100] 11. The sample preparation method (100) of any one of the preceding embodiments, wherein substrate is thermally coupled to the temperature control element (12) via conduction.

[0101] 12. The sample preparation method (100) of any one of the preceding embodiments, wherein the sample (30) is a biological sample, particularly a biological sample comprising blood.

[0102] 13. The sample preparation method (100) of any one of the preceding embodiments, wherein dispensing (110) comprises printing the sample (30) on the substrate (14).

[0103] 14. The sample preparation method (100) of any one of the preceding embodiments, wherein the sample (30) is dispensed on the substrate (14) in a predefined pattern, particularly in a pattern of a plurality of adjacent rows.

[0104] 15. The sample preparation method (100) of embodiment 14, wherein separation between adjacent rows during the dispensing is between about 0.2 mm and about 0.6 mm. 16. The sample preparation method (100) of any one of the preceding embodiments, wherein drying (120) does not include force-air drying.

[0105] 17. The sample preparation method (100) of any one of the preceding embodiments, wherein the sample preparation method (100) is carried out in an automated analyser system (1), and optionally wherein the sample (30) is prepared for subsequent automated analysis in the automated analyser system (1).

[0106] 18. A sample preparation apparatus (10) for use in an automated analyser system (1), the sample preparation apparatus (10) comprising: a temperature control element (12), a substrate (14) being thermally coupled to the temperature control element (12), a sample applicator (16) configured to dispense a sample (30) on the substrate (14), a control unit (18) configured to control the temperature of the temperature-control element (12) based on input data including at least one input parameter on ambient conditions.

[0107] 19. The sample preparation apparatus (10) of embodiment 18 being configured to perform the method (100) of any one of embodiments 1 to 17. 0. The sample preparation apparatus (10) of any one of embodiments 18 to 19, further comprising a temperature-controlled support (13) which comprises the temperature control element (12), and wherein the substrate (14) is arranged on the temperature- controlled support (12). 1. The sample preparation apparatus (10) of any one of embodiments 18 to 20, wherein the temperature control element (12) comprises a thermoelectric element, particularly a Peltier element. 2. The sample preparation apparatus (10) of any one of embodiments 18 to 21, wherein the temperature control element (12) is configured to conductively control a temperature of the substrate (14). The sample preparation apparatus (10) of any one of embodiments 18 to 22, wherein the substrate (14) is a slide, particularly a microscope slide. The sample preparation apparatus (10) of embodiment 23, wherein the slide is made of glass or plastic material. The sample preparation apparatus (10) of any one of embodiments 18 to 24, wherein the substrate (14) has a thickness of about 0.1mm to about 2.0mm, specifically about 0.5mm to about 1.5mm. The sample preparation apparatus (10) of any one of embodiments 18 to 25, further comprising a temperature sensor (I la) configured to measure ambient temperature and / or a humidity sensor (1 lb) configured to measure ambient humidity. The sample preparation apparatus (10) of any one of embodiments 18 to 26, further comprising a wall protection arranged on lateral sides of the substrate (30). An automated analyser system (1) for analysing a prepared sample (30) comprising: the sample preparation apparatus (10) of any one of embodiments 18 to 27, and a sample analysis apparatus (20) configured to analyse the sample (30) prepared by the sample preparation apparatus (10).

Claims

Claims1. A sample preparation method (100) for subsequent analysis, the method (100) comprising: dispensing (110) a sample (30) in liquid state on a substrate (14) being thermally coupled to a temperature control element (12); drying (120) the sample (30); obtaining (130) input data including at least one input parameter on ambient conditions; controlling (1 0) the temperature of the temperature control element (12) based on the obtained input data.

2. The sample preparation method (100) of claim 1, wherein obtaining (130) at least one input parameter on ambient conditions comprises measuring ambient humidity and measuring ambient temperature.

3. The sample preparation method (100) of any one of the preceding claims, wherein controlling (140) the temperature of the temperature control element (12) comprises applying an evaporation rate algorithm configured to determine a target temperature of the temperature control element (12) based on the obtained input data.

4. The sample preparation method (100) of any one of the preceding claims, wherein obtaining (130) the input data further includes obtaining an input parameter on a desired drying time of the sample (30) and / or an input parameter on a volume of the sample (30) and / or an input parameter on the surface area of the sample (30).

5. The sample preparation method (100) of claim 4, wherein the desired drying time is selected based on the volume of the dispensed sample.

6. The sample preparation method (100) of any one of claims 4 or 5, wherein, based on the determined target temperature, the temperature of the temperature control element (12) is adjusted, particularly wherein the temperature of the temperature control element (12) is increased or decreased.

7. The sample preparation method (100) of any one of the preceding claims, wherein substrate is thermally coupled to the temperature control element (12) via conduction.

8. The sample preparation method (100) of any one of the preceding claims, wherein the sample (30) is a biological sample, particularly a biological sample comprising blood.

9. The sample preparation method (100) of any one of the preceding claims, wherein drying (120) does not include force-air drying.

10. The sample preparation method (100) of any one of the preceding claims, wherein the sample preparation method (100) is carried out in an automated analyser system (1), and optionally wherein the sample (30) is prepared for subsequent automated analysis in the automated analyser system (1).

11. A sample preparation apparatus (10) for use in an automated analyser system (1), the sample preparation apparatus (10) comprising: a temperature control element (12), a substrate (14) being thermally coupled to the temperature control element (12), a sample applicator (16) configured to dispense a sample (30) on the substrate (14), a control unit (18) configured to control the temperature of the temperature-control element (12) based on input data including at least one input parameter on ambient conditions.

12. The sample preparation apparatus (10) of claim 11, further comprising a temperature- controlled support (13) which comprises the temperature control element (12), and wherein the substrate (14) is arranged on the temperature-controlled support (12).

13. The sample preparation apparatus (10) of any one of claims 11 or 12, wherein the temperature control element (12) comprises a thermoelectric element, particularly a Peltier element.

14. The sample preparation apparatus (10) of any one of claims 11 to 13, further comprising a wall protection arranged on lateral sides of the substrate (30).

5. An automated analyser system (1) for analysing a prepared sample (30) comprising: the sample preparation apparatus (10) of any one of claims 11 to 14, and a sample analysis apparatus (20) configured to analyse the sample (30) prepared by the sample preparation apparatus (10).

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