Apparatus, method and use for liquid handling

Abstract

An apparatus for liquid handling, in particular of small liquid volumes, an associated method and use for liquid handling, in particular for receiving and / or dispensing a liquid, the apparatus comprising: a capillary; a plate; means for moving the capillary and / or the plate relative to each other; and a sensor (9).

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The current invention relates to an apparatus and a method for liquid handling, in particular receiving and / or dispensing a liquid from or onto a plate. The present invention further relates to a corresponding use for liquid handling.DESCRIPTION OF THE RELATED ART

[0002] A fundamental problem when handling small liquid samples, in particular in the microliter, nanoliter, or picoliter range, is usually related to their high surface-to-volume ratio. Typically, high-throughput screening including the handling of such small liquid samples can be very challenging due to the high sample consumption, and it requires long processing time. For example, multi-well plates are used with 96, 384, 1536 or 3456 wells and pipetting robots to supply the liquids. The conventional way to dispense small amounts of fluids in an automated way is by a pipetting robot (EP 2 613 155 A1). Herein, the fluids can be received / aspirated or dispensed in a controlled manner in a multi-well plate or a plate with a patterned surface. Automated systems are widely available, however due to the large volumes per well, the sample consumption is high (e.g. 1 µl - 100 µl per well) and pipetting requires a substantial time.

[0003] In recent years, droplet microfluidics has been introduced for enhancing the speed in screening and reducing sample volumes. Droplet microfluidics have, however, disadvantages as the droplets are difficult to assess and standard procedures cannot be easily transferred. Hence, it is not suitable for many applications that are conducted on multi-well plates.SUMMARY OF THE INVENTION

[0004] It is the objective underlying the present invention to provide an improved, in particular more efficient, faster, easier, and / or more environmentally friendly apparatus and / or method for liquid handling, in particular for small liquid volumes.

[0005] This task is solved by an apparatus with the features of claim 1. Further embodiments of the apparatus, method as well as a use are defined by the features of further claims.

[0006] In a first aspect, the present invention is directed to an apparatus for liquid handling, wherein the apparatus comprises: a capillary having a first opening and a second opening; a plate having a top surface defining an x-y-plane, the top surface comprising at least one hydrophobic and at least one hydrophilic area, wherein the capillary is configured to receive and / or dispense a liquid from and / or onto the top surface of the plate via the second opening, means for moving the capillary and / or the plate relative to each other in two and / or three dimensions at a distance between the second opening of the capillary and the top surface of the plate, in particular at a distance in the range of 0.1 µm to 500 µm; and a sensor configured to measure the distance between the second opening of the capillary and the top surface of the plate.

[0007] The capillary for use in the present invention for all aspects and embodiments can be any capillary that is suitable for receiving and / or dispensing a liquid. In an embodiment of the apparatus, the capillary is made of metal, glass, a polymer, or plastic.

[0008] In an embodiment, the surface of the capillary walls inside the capillary, meaning the surface contacting the liquid when a liquid is inside the capillary, the surface of the capillary outside the capillary, and / or the surface surrounding the second opening of the capillary, has an opposing wettability property, i.e. hydrophilicity and hydrophobicity, or lipophilicity and lipophobicity, with respect to the liquid to be dispensed and / or received. For example, when dispensing a hydrophilic liquid, a capillary having a hydrophobic wall surface inside and / or outside the capillary is preferred. Accordingly, when dispensing a lipophilic liquid, a capillary having a lipophobic wall surface inside and / or outside the capillary is preferred.

[0009] Preferably, the capillary has a length in the range of 0.2 m to 0.5 m, optionally 0.01 m to 1 m, an inner diameter in the range of 40 µm to 150 µm, optionally 2 µm to 500 µm, and / or an outer diameter in the range of 100 µm to 400 µm, optionally 100 µm to 1000 µm. The inner diameter of the capillary is for receiving and / or dispensing a liquid.

[0010] The capillary of the apparatus has at least two, in particular at least two, three, four, five, six, seven, eight, nine or ten openings, which at least two openings are referred to as the first and the second opening. In an optional embodiment, the capillary has the shape of a straight linear tube, and / or the first and / or the second opening are arranged on opposite endings of the capillary. For example, the first opening is at the or defines the first ending of the capillary and / or the second opening is at the or defines the second ending of the capillary. However, the capillary may have any shape suitable for dispensing and / or receiving a liquid and, in some exemplary embodiments, the capillary does not have the shape of a straight linear tube and is, e.g., a Y-junction or a T-junction. In this case, the capillary may have only two openings (first opening and second opening), or it may have more than two openings, in particular three openings (i.e. first opening, second opening and third opening, the third opening having for example the same features and function as the first opening or optionally as the second opening). In an embodiment, the capillary has the form of a branched tube with at least one, in particular at least two, three, four, five, six, seven, eight, nine or ten first openings.

[0011] The first opening, for example a top opening of the capillary, can be arranged at any position area of the capillary which is distinct from the position area of the second opening, i.e. the first and the second opening are not the same or they do not overlap. The second opening, for example a bottom opening of the capillary, is arranged in a manner that it essentially faces the top surface of the plate, for example in a way that a plane defining the cross-sectional area of the second opening is (at least essentially) parallel to the x-y-plane of the plate, in particular the top surface of the plate.

[0012] In an embodiment, the apparatus comprises more than one capillary having a first opening and a second opening, for example at least two, three, four, five, six, seven, eight, nine, ten, eleven, or twelve capillaries, each capillary optionally having a first opening and a second opening. In particular, the more than one capillaries can be connected with each other in parallel thus allowing for operating the capillaries in a timely and / or spatially synchronized manner.

[0013] The plate of the apparatus, in particular the top surface of the plate, defines the x-y-plane, the top surface of the plate being the surface of the plate facing the capillary, for example the second opening of the capillary. Hence, the term "top" is not limited to any relationship with gravity and in some embodiments of the inventive apparatus, method, or use, the top surface of the plate can refer to a surface that has a normal vector pointing in direction or opposite the direction of gravity. A plate, as used herein, is a three-dimensional object which, when positioned within the apparatus, has a height and a base area essentially extending parallel to the x-y-plane. In an embodiment, the height of the plate is the same or less than its length, i.e. the length of its base area. In another embodiment, the height of the plate is the same or bigger than its length, i.e. the length of its base area. Plates for use in the present invention also encompass a plate with an irregular, i.e. respectively varying thickness and / or bow and / or warpage.

[0014] In an example, the top surface of the plate is not perfectly planar, and the top surface for example deviates from planarity of about 1 µm to 1000 µm, optionally 10 µm to 750 µm, 50 µm to 500 µm, 50 µm to 250 µm or 100 µm to 200 µm, for example by exhibiting elevations and / or depressions of about 1 µm to 1000 µm deviation from the plane of the top surface of the plate. However, it should be noticed that also top surfaces being perfectly planar fall within the scope of the present invention.

[0015] The person skilled in the art can freely choose the size of the plate depending on their needs. In an example, the plate is a rectangular plate and / or the top surface of the plate has a size of about 85 mm x 128 mm or 25 mm x 75 mm.

[0016] In an embodiment, the plate comprises or is made of metal, glass, polymer, or plastic, and the top surface of said plate comprises or consists of at least one hydrophobic and at least one hydrophilic area, or at least one lipophilic and at least one lipophobic area. These areas can be evenly or unevenly distributed over the top surface of the plate and arranged next to each other and / or contacting each other, each area having a size in the range of 50 µm to 250 µm, optionally 10 µm to 500 µm. For example, such areas are formed in the top surface of the plate by known means such as lithography, deposition or etching. Typically, the number of such areas on the plate is more than 10, in particular, more than 1000, more than 10.000, more than 100.000 or more than 1.000.000.

[0017] The capillary for use in the present invention is configured to receive and / or dispense a liquid. Optionally, and in an embodiment, the apparatus may comprise the liquid, e.g. on the top surface of the plate, in the capillary and / or in a reservoir that is or can be fluidly connected to the capillary. The explanations and definitions provided in the context of the present method, in particular in the context of step a), apply to the liquid for use in the apparatus defined herein. The liquid can be one or multiple different liquids, e.g. multiple liquids spatially distanced from one another in the capillary. The liquid can be any substance or mixture of substances in liquid form, including hydrophobic and hydrophilic liquids. The liquid can be a one-phase liquid, in particular if the capillary and / or apparatus is configured (and used) to dispense a liquid onto the top surface of the plate. Alternatively, the liquid can be a two-phase liquid, in particular if the capillary and / or apparatus is configured (and used) to receive a liquid from the top surface of the plate. The liquid may comprise partially undissolved or undissolved solids, i.e. it may be a suspension, or an emulsion. In an embodiment, the liquid is a one-phase liquid without undissolved or partially undissolved solids. The explanations provided for the liquid also apply to the method disclosed herein.

[0018] The apparatus further comprises at least one means for moving the capillary and / or the plate, such as an electric motor, an engine, and / or a drive. Such means are configured to move the capillary and / or the plate relative to each other in two and / or three dimensions, for example along a z-axis (perpendicular to the x-y-plane) and / or a plane parallel the x-y-plane of the top surface of the plate, and / or a vector combination thereof. In an embodiment, the means are configured to move the capillary along the z-axis of the plate and / or to move the plate along and / or parallel the x- and / or y-direction. The means for moving the capillary and / or the plate are configured to conduct a movement in such a way that the top surface of the plate and the second, i.e. bottom, opening do not contact each other, in particular remain at a distance in the range of 0.1 µm to 500 µm, optionally 1 µm to 500 µm, 10 µm to 500 µm, 100 µm to 500 µm, 250 µm to 500 µm, 0.1 µm to 400 µm, 0.1 µm to 300 µm, 0.1 µm to 200 µm, or 0.1 µm to 100 µm. In particular, the means are configured to move the capillary and / or the plate according to a geometrical profile of the top surface of the plate and across the hydrophilic and hydrophobic areas. For example, if the top surface of the plate is not perfectly planar and has some unevenness, the means can move the capillary and / or the plate accordingly, for example to ensure that the distance between those two remains constant during the movement.

[0019] It should however be noted that in some embodiments of the apparatus, the method, and / or the use, which may be combined with any of the preaddressed embodiments or the embodiments to be addressed unless in contradiction, the means are also configured to move the capillary and / or the plate so that the distance between the top surface of the plate and the second, i.e. bottom, opening of the capillary can be varied. In particular, depending on the flow rate and / or the volume flow of the liquid, the distance between the second, i.e. bottom, opening of the capillary and the top surface of the plate, can be changed, for example automatically, wherein the sensor measures the distance obtaining a measurement value and providing it to the means for moving the capillary and / or the plate, or alternatively, to a unit controlling the means.

[0020] The apparatus further comprises a sensor for measuring the (actual) distance between the second opening of the capillary and the top surface of the plate. In a typical example, the second opening allocates with the (physical) second ending of the capillary. In this example, the distance measured by the sensor relates to the distance between the (physical) second ending of the capillary and the surface of the plate. In a typical example, the sensor is also used to avoid contact between the plate and the capillary and to set a suitable distance between the second opening and the surface of the plate for receiving and / or dispensing a liquid from and / or onto the top surface of the plate via the second opening. However, if the second opening should not (exactly) allocate with the (physical) second ending of the capillary, the skilled person can determine the distance between the second opening and the (physical) second ending and use this information to assure that the capillary does not, e.g. scratch or touch the top surface of the plate based on the measurement of the sensor. In an alternative which can be combined with all aspects and embodiments disclosed herein unless in contradiction, the sensor can also be configured to measure the distance between the second ending of the capillary and the top surface of the plate. In this alternative, the second ending is the part of the capillary which is located closest to the surface of the plate.

[0021] For example, the sensor is configured to scan the top surface of the plate, in particular to provide a geometrical profile, preferably a 3D geometrical profile, of the top surface of the plate. In an embodiment, the sensor is further configured to forward an information about the geometrical profile to an optional control unit of the apparatus, which control unit controls the means for moving the capillary and / or the plate in accordance with the geometrical profile information. In an embodiment, the sensor is arranged above the top surface of the plate, or sidewise to the plate, for example outside an area obtained by an orthogonal projection of the top surface of the plate.

[0022] In an embodiment which may be combined with any of the embodiments or aspects already addressed or to be addressed, the top surface of the plate is covered with a hydrophilic or hydrophobic liquid or oil, in particular an inert hydrophilic or hydrophobic liquid or oil, such as e.g. a perfluorinated oil. Such covering liquid or oil is especially advantageous if the liquid to be deposited or received by the second opening of the capillary is volatile or would otherwise react with air - in this case the covering liquid provides a protection of the sample liquid.

[0023] In an embodiment of the apparatus according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, the apparatus further comprises means for applying a positive and / or a negative pressure onto the capillary, in particular between the first opening and the second opening of the capillary; and / or the sensor is a force sensor, an optical sensor, an electrical sensor, or a magnetic sensor.

[0024] In the context of the present invention, the means for applying a positive and / or negative pressure are in particular a pressure device allowing for generating a positive and / or negative pressure between the first and the second opening of the capillary, for example a vacuum pump, a syringe pump, a hydraulic pump, a diaphragm pump, a piston pump, a peristaltic pump, a plunger pump, a centrifugal pump, a turbine pump, or a pressure source such as pressure gas or a device providing a hydrostatic pressure.

[0025] A positive pressure between the first opening and the second opening of the capillary refers to an overpressure between the first and the second opening, wherein the pressure at or in the area of the first opening is bigger than the pressure at or in the area of the second opening. As consequence a liquid inside the capillary would flow from the first opening in direction of the second opening of the capillary and be therefore dispensed.

[0026] A negative pressure between the first opening and the second opening of the capillary refers to an underpressure between the first and the second opening, wherein the pressure at or in the area of the first opening is smaller than the pressure at or in the area of the second opening. As consequence a liquid inside the capillary would flow from the second opening in direction of the first opening of the capillary and be therefore received.

[0027] In an embodiment which may be combined with any embodiment or aspect already addressed or to be addressed, the apparatus is configured to change the distance between the second opening of the capillary and the top surface of the plate depending on the pressure applied by the means for applying a positive and / or negative pressure, the speed of moving the capillary and / or the plate relatively to each other, and / or the amount of liquid to be received or dispensed from or onto the top surface of the plate.

[0028] In an embodiment of the invention, the sensor is a tension and compression load cell, e.g. with a capacity of 10 g and / or a resolution of about 200 pg or 1.96 µN. In another embodiment, the sensor is a tension and compression load cell with a capacity in a range of, e.g., 11 g to 250 g, in particular 20 g to 200 g, 50 g to 150 g, 75 g to 125 g, or 100 g.

[0029] In an embodiment of the apparatus according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, the apparatus further comprises a control unit configured to control at least one of the following: the means for applying a positive pressure and / or a negative pressure; and / or the means for moving the capillary and / or the plate according to the distance between the second opening of the capillary and the top surface of the plate.

[0030] In an embodiment, the control unit is a processor, or a computer comprising a software and configured to control, in particular supervise, initiate, stop, and / or change the direction and / or speed of the means for applying a positive and / or negative pressure or the means for moving the capillary and / or the plate.

[0031] In an embodiment of the apparatus according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, the sensor is arranged at the capillary, in particular between the second opening of the capillary and the top surface of the plate, and optionally wherein the sensor and the capillary are together movable with respect to the top surface of the plate, or wherein the sensor is arranged outside an area obtained by an orthogonal projection of the top surface of the plate.

[0032] In an alternative which can be combined with all aspects and embodiments disclosed herein unless in contradiction, the sensor can also be arranged between the second ending of the capillary and the top surface of the plate. In this alternative, the second ending is the part of the capillary which is located closest to the surface of the plate.

[0033] In a second aspect, the present invention is directed to a method for liquid handling, in particular dispensing and / or receiving a liquid, the method comprising the following steps, in particular the steps being performed in the given order: a) providing an apparatus for liquid handling as disclosed herein and a liquid, in particular a one-phase liquid or a two-phase liquid; b) measuring a distance between the second opening of the capillary and the top surface of the plate by the sensor; and c) dispensing the liquid through the capillary via the second opening of the capillary onto the top surface of the plate or receiving the liquid from the top surface of the plate into the capillary via the second opening of the capillary.

[0034] The method allows for an easy and efficient liquid handling, in particular of small volumes of liquid in a microliter, nanoliter and / or picoliter range.

[0035] In step a), an apparatus according to any one of the previously addressed embodiments and a liquid are provided, in particular inside the capillary, or on the top surface of the plate. In particular, the liquid can be a one-phase liquid. A one-phase liquid means that any components of the liquid are miscible at the proportions used in the method, in particular at room temperature or at the temperatures indicated below, without phase separation at least during operation of the method. The skilled person can routinely determine whether the liquid, e.g. in the capillary, is and remains one phase during operation of the method. For example, the one-phase liquid does not comprise a second phase being solely a hydrophilic, hydrophobic, lipophilic or lipophobic liquid under the standard operation conditions of the apparatus, such as for example at a temperature in the range of 0°C to 90°C, optionally 10°C to 75°C, 20°C to 50°C, 22°C to 40°C or at room temperature. In an embodiment, the liquid is a hydrophilic or hydrophobic liquid with or without solid particles dispersed inside the liquid. In another embodiment, the liquid is a hydrophilic or hydrophobic liquid with or without any gas, in particular gas bubbles, inside the liquid.

[0036] The method further comprises a step b) of measuring, in particular determining a distance between the second opening of the capillary facing the top surface of the plate and the top surface of the plate, which measuring, is performed by the sensor of the apparatus, in particular by scanning the top surface of the plate, and in particular results in a geometrical profile of the top surface of the plate, further in particular a 3D geometrical profile of the top surface of the plate. The measuring performed in step b) allows for determining an accurate distance (e.g. within an accuracy of ± 0.1 µm) between the second opening of the capillary and the top surface of the plate, also when the top surface is not perfectly even and has some defects or artefacts localized at some areas of the top surface. In an alternative which can be combined with all aspects and embodiments disclosed herein unless in contradiction, the distance is measured between the second ending of the capillary and the top surface of the plate. In this alternative, the second ending is the part of the capillary which is located closest to the surface of the plate.

[0037] The method further comprises a step c) in which the liquid is dispensed through the capillary via its second opening onto the top surface of the plate, in particular by passing through the first opening and followed by passing through the second opening of the capillary, or in which the liquid is received from the top surface of the plate into the capillary via the second opening of the capillary, in particular by passing through the second opening of the capillary and followed by passing through the first opening of the capillary.

[0038] It has been found that providing a protective liquid layer over the plate in one of the method steps, in particular over and in contact with the top surface of the plate, can have the advantageous effect of protecting the liquid droplets located on the top surface of plate from the atmospheric conditions around them, e.g. from being decomposed by air, oxygen or water, depending on the nature of the droplets. In this example, the liquid of the protective liquid layer is preferably of a different phase than the liquid provided in step a) when both liquids are in contact, e.g. if the liquid provided in step a) is hydrophilic, the liquid of the liquid protective layer is hydrophobic, or if the liquid provided in step a) is hydrophobic, the liquid of the liquid protective layer is hydrophilic.

[0039] In an embodiment, the protective liquid layer is composed of a chemically inert substance, in particular a substance inert with respect to the liquid provided in step a) and is for example selected from the group of a fluorinated and / or non-fluorinated hydrocarbon, or a perfluorochemical.

[0040] In an embodiment, the liquid provided in step a) to be received from the top surface of the plate is a two-phase liquid. In particular if a protective liquid layer is provided over the plate, further in particular in one of the method steps a),b), or c), the liquid received by the capillary in step c) is a two phase-liquid, optionally comprising or consisting of the liquid from the protective liquid layer and the actual liquid provided in step a). Receiving a two-phase liquid inside the capillary allows for preforming separate compartments inside the capillary, the compartments consisting of one phase only. A compartmentalization has an advantageous effect for an optional subsequent dispensing of the liquid from the capillary and storing the liquid inside the capillary.

[0041] In an embodiment steps b) and c) are performed one after the other, both after step a), with a step sequence of a),b),c). Steps b) and c) can however also be repeated multiple times, which is desirable when more than one batch of liquid is to be received or dispensed, for example in a step sequence a),b),c),b),c) or a),b),c),b),c),b),c) or a),b),c),c) or a),b),c),c),c) if the measuring the distance does not have to be repeated. Steps b) and c) may also be conducted simultaneously meaning that measuring the distance is conducted while dispending or receiving the liquid.

[0042] In an embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, dispensing the liquid from the second opening of the capillary onto the top surface of the plate comprises a step wherein the liquid contacts the top surface of the plate while contacting the second opening of the capillary and wherein the capillary and / or the plate are moved at the distance and relative to each other to shear off a volume of liquid, in particular a droplet, onto the plate.

[0043] In this step being part of step c), the liquid is contacting the second opening of the capillary, in particular being inside the capillary and / or the second opening of the capillary, and simultaneously contacts the top surface of the plate while the second opening of the capillary and the top surface of the plate not contacting each other. This is realized by the formation of a column-like structure made of the liquid, which column-like structure extends from the second opening of the capillary to the top surface of the plate, contacting both the second opening of the capillary and the top surface of the plate. Alternatively, and if the second opening does not allocate with the second ending of the capillary being closest to the top surface of the plate, the liquid may instead simultaneously touch the second ending of the capillary and the top surface of the plate when the sheer-off is induced. In the above embodiments, dispensing the liquid does not entail pre-forming a droplet exiting from the second opening (or the second ending being closest to the top surface of the plate) of the capillary, in particular before it is dispensed onto the top surface of the plate. Once the above-described column-like structure is formed, in particular by applying a positive pressure between the first opening and the second opening of the capillary when the liquid is inside the capillary, the capillary and / or the plate are moved at a distance and relative to each other such that a volume of liquid, in particular in a microliter, nanoliter, or picoliter range, is sheared off onto the top surface of the plate, in particular as a droplet. Such shearing off for example takes place when a part of the column-like liquid structure, in particular at the second opening of the capillary is being moved in a different direction than another part of the column-like liquid structure, in particular at the top surface of the plate, or when both parts of the column-like structure are being moved in the same direction but with different relative speeds. Accordingly, no single droplet of the liquid is formed before the liquid contacts the top surface of the plate. For example, the movement to shear-off the volume of liquid is a movement of the capillary or the plate essentially in the x-y-plane of the plate, or a movement of the capillary and the plate essentially in the x-y-plane of the plate, either in the same direction at different speeds or in different directions, e.g. opposing directions at the same or different speeds. In one embodiment of the invention which may be combined with any of the preaddressed embodiments and aspects or embodiments and aspects to be addressed unless in contradiction, the movement to shear-off the volume of liquid comprises a z-component, i.e. it is a movement of the capillary or the plate essentially in the x-y-plane of the plate combined (contemporary or at different time points) with a z-direction vector orthogonal to the x-y-plane, or a movement of the capillary and the plate essentially in the x-y-plane of the plate combined with a z-direction vector orthogonal to the x-y-plane.

[0044] In an embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, moving the capillary and / or the plate at the distance and relative to each other comprises a movement of the plate essentially in the x-y-plane of the plate and / or a movement of the capillary essentially parallel or along a z-axis, the z-axis being essentially perpendicular to the x-y-plane of the plate.

[0045] In an embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, the liquid to be dispensed and / or received in step c) is a droplet of liquid, in particular a droplet of a one-phase liquid.

[0046] A droplet refers to a small drop, for example of a liquid or an oily substance, wherein the droplet can have a volume in a microliter, nanoliter and / or picoliter range. The droplet can be of any shape, in particular of an essentially spherical or spherical shape and / or of a drop shape. However, and as outlined above, a column-like structure made of the liquid, which column-like structure extends from the second opening of the capillary to the top surface of the plate, contacting both the second opening of the capillary and the top surface of the plate can be formed in an example of the present method. This column-like structure is understood to be an intermediate form of the droplet as used herein.

[0047] In an embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, the liquid is hydrophobic and is dispensed in step c) on a hydrophobic area of the plate or is received in step c) from a hydrophobic area of the top surface of the plate; or the liquid is hydrophilic and is dispensed in step c) on a hydrophilic area of the plate or is received in step c) from a hydrophilic area of the top surface of the plate.

[0048] The dispensing is preferably supported by attractive forces, such as the adhesion, between the liquid to exit or to enter the second opening of the capillary and the respective area of the top surface of the plate. Additionally, a person skilled in the art knows well how to determine if the liquid and / or the area of the top surface of the plate is hydrophilic or hydrophobic.

[0049] In an embodiment of the method, receiving the liquid from the top surface of the plate occurs after its dispending onto the top surface of the plate through the second opening of the capillary, i.e. the liquid to be received originates from the previously dispensed liquid.

[0050] In an embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, dispensing or receiving the liquid in step c) is supported and / or controlled by the means for applying a positive pressure and / or a negative pressure onto the capillary.

[0051] As previously mentioned, the means for applying a positive and / or negative pressure are in particular a pressure device allowing for generating a positive and / or negative pressure between the first and the second opening of the capillary, for example a vacuum pump, a syringe pump, a hydraulic pump, a diaphragm pump, a piston pump, a peristaltic pump, a plunger pump, a centrifugal pump, a turbine pump, or a pressure source such as pressure gas. In an embodiment, these means comprise or are operatively connected to a control unit which controls the dispensing and / or receiving of the fluid. For example, if the liquid should be received, the means for applying negative pressure are activated by the control unit and a negative pressure is applied onto the capillary, supporting the liquid to enter the second opening of the capillary. Analogously, if the liquid should be dispensed, the means for applying positive pressure are activated by the control unit and a positive pressure is applied onto the capillary, supporting the liquid to exit the second opening of the capillary.

[0052] In an embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, dispensing the liquid in step c) comprises the step of applying a positive pressure between the first opening and the second opening of the capillary and / or receiving the liquid in step c) comprises the step of applying a negative pressure between the first opening and the second opening of the capillary.

[0053] In an embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, dispensing the liquid from the second opening of the capillary or receiving the liquid into the second opening of the capillary in step c) is a continuous dispensing or a continuous receiving, in particular without stopping the flow of the liquid through the second opening of the capillary.

[0054] A continuous dispensing or receiving refers to a process in which the flow of the liquid, in particular one-phase or optionally a two-phase liquid, is not stopped at any point of time during the receiving or dispensing through the capillary, in particular the second opening of the capillary. In an embodiment, the continuously received liquid is a two-phase liquid comprising for example a hydrophilic and a hydrophobic phase, a hydrophilic or hydrophobic phase and a gas, in particular air.

[0055] In an embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, step b) of measuring a distance is performed by determining a three-dimensional map of the top surface of the plate with the sensor and / or wherein step b) of measuring the distance is repeated at least once, in particular after step a) and / or after step b) and / or after step c).

[0056] The three-dimensional map is a possible geometrical profile of the top surface of the plate which is provided by measurement data obtainable or obtained by the sensor. In order to determine the three-dimensional map, the sensor scans the top surface of the plate to obtain at least two, preferably a multiplicity of coordinate data. In an embodiment, the latter are subsequently plotted giving the three-dimensional map from which the distance between the second opening (or the second ending as outlined above) of the capillary and the top surface of the plate is easily determinable. The distance measuring, in particular scanning of the top surface of the plate, for example to obtain the three-dimensional profile, may be performed only once, for example directly after step a) and simultaneously with or before step c). However, step b) may also be performed several times before and / or after step c), for example 1 to 1.000, 1 to 500, or 1 to 10 times during the deposition or receiving of the liquid onto or from the plate.

[0057] In an embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, the flow of the liquid out and through the second opening of the capillary while dispensing the liquid in step c) is oscillating. In particular, such oscillating disposal can be reached by a pressure pulse pushing the liquid out and through the second opening of the capillary. Consistent with the above, the pressure pulse can be timely and spatially synchronized with the movement to shear-off the volume of liquid being a movement of the capillary and / or the plate.

[0058] In an embodiment which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, dispensing the liquid in step c) is piezo-driven.

[0059] In a further embodiment of the method according to the present invention which may be combined with any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, dispensing or receiving the liquid in step c) is not continuous, i.e. the flow of the liquid, in particular one-phase or optionally a two-phase liquid, is stopped during the receiving or dispensing through the capillary, in particular the second opening of the capillary, when the capillary is positioned above a first hydrophilic or hydrophobic area. In an embodiment, after the flow of the liquid has been stopped, the capillary and / or the plate is moved, in particular so that the capillary is positioned above a second hydrophilic or hydrophobic area, depending on the wettability of the liquid to be received or dispensed.

[0060] In a third aspect, the present invention is directed to a use of the apparatus or the method according to any of the embodiments and aspects preaddressed or still to be addressed unless in contradiction, the use being for liquid handling, in particular receiving and / or dispensing a liquid.

[0061] The use may be applied, but is not in any way limited to e.g. screening of chemicals, in particular natural or synthetic pharmaceuticals, sample preparation, for example for medical analyses, material scientific analyses, reaction screening, crystallizations, living organism studying, in particular studying of a cell culture, microorganisms, pathogens, bacteria, etc.

[0062] In an embodiment of the present invention, the apparatus further comprises analytical means, for example a spectroscope, in particular an optical spectroscope, e.g. IR-, and / or UV / Vis-, and / or fluorescence spectroscope, a microscope, a mass spectrometer, an NMR measuring device, or an X-ray diffractometer. Hence both in the method and in the use embodiments, the received and / or dispensed liquid may be subjected to an analytical measurement by applying the analytical means of the apparatus.BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Embodiments of the current invention are described in more detail in the following with reference to the figures. These are for illustrative purposes only and are not to be construed as limiting. It shows Fig. 1 a)a schematic depiction of the apparatus; Fig. 1 b)a schematic depiction of the apparatus; Fig. 2 a)photographs of experimental results obtained by using the apparatus; Fig. 2 b)photographs of experimental results obtained by using the apparatus; Fig. 3boxplot showing liquid volumes with respect to the corresponding pressure conditions; Fig. 4a schematic depiction of the apparatus; Fig. 5a schematic depiction of the apparatus in more detail; Fig. 6 a)a schematic overview of the liquid volume dispensing mechanism according to the present method; Fig. 6 b)a schematic overview of a gradient formation according to the present method. DETAILED DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 shows a very simplified schematic, and therefore not true-to-scale depiction of the apparatus 1 for liquid handling. The embodiment shown in Figure 1 a) comprises a capillary 2 having the form of a straight thin tube with a first opening 3 at its top / first ending (top opening) and a second opening 4 at its bottom / second ending (bottom opening). However, of course also other capillary shapes are possible, such as for example a curved capillary, and / or a capillary with a non-constant diameter, in particular wherein the first opening 3 has a bigger or smaller cross-sectional area, further in particular diameter than the second opening 4. The apparatus further comprises a plate having a top surface 5. In the embodiment shown in the Figure, the top surface 5 is perfectly planar and is defined by the x-y-plane. However, a skilled person understands that the top surface 5 in the most cases will not be perfectly planar but essentially planar. Hence, the top surface 5 of the plate can have some small imperfections deviating from the (perfect) x-y-plane of about 100 µm - 200 µm, optionally 1 µm - 500 µm, such as surface elevations or depressions. The top surface 5 of the plate exhibits at least one hydrophobic area 6 and at least one hydrophilic area 7, in particular more than one hydrophobic area 6 and more than one hydrophilic area 7, further in particular more than 2 hydrophobic areas 6 and more than 2 hydrophilic areas 7, or more than 5 hydrophobic areas 6 and more than 5 hydrophilic areas 7. In Figure 1, the areas are distributed symmetrically and equally over the top surface 5 of the plate, however also a non-symmetrical and / or non-equal distribution of the areas 6 and 7 is possible according to some further embodiments. The apparatus 1 further comprises a sensor 9 which is configured to measure the distance between the second opening (or second ending) 4 of the capillary 2 and the top surface 5 of the plate, in particular the shortest distance. The sensor 9 depicted herein is positioned outside an area obtainable by an orthogonal projection of the top surface 5 of the plate, meaning that it is positioned sidewise with respect to the plate or the top surface 5 of the plate and / or it is not positioned directly above the top surface 5 of the plate. Such positioning is however possible according to a different embodiment of the invention and the position of the sensor can be adjusted according to the needs of the skilled person. In the depicted apparatus 1, a means for moving 8 and / or controlling the movement of the capillary 2 and / or the plate relative to each other (in x-, y-, and / or z-direction) at a distance between the second opening 4 of the capillary 2 and the top surface of the plate 5 is schematically depicted as a checkered rectangle. In this embodiment, the means 8 is operatively connected only to the capillary 2, meaning that only the capillary 2 is movable and the plate is not movable - in the apparatus 1 and / or in the associated method for liquid handling.

[0065] The embodiment shown in Figure 1 b) essentially equals the embodiment of Figure 1 a) apart the operational connection of the means for moving 8 the capillary 2 and / or the plate relative to each other. In this embodiment, the means 8 is connected both to the capillary 2 and to the plate such that both the capillary 2 and the plate resp. the top surface 5 of the plate are movable. In another embodiment which is not depicted herein, the means 8 is operatively connected to the plate, not being connected to the capillary 2 - in this case only the plate is movable and the capillary 2 is / remains static.

[0066] Figure 2 a)shows photographs of experimental results of an apparatus characterization. Depicted are fluorescence (on the left) and brightfield (on the right) images of droplets obtained at 100 mbar, 150 mbar and 200 mbar pressure applied onto the capillary and 50 µm distance between the second opening (e.g. nozzle) and the top surface 5 of the plate. The spot diameter is 125 µm.

[0067] Figure 2 b)shows photographs of experimental results showing a variation of the droplet volume. Depicted are brightfield (top row) and fluorescence (middle row) images of droplets obtained on a standard fluorescence microscope. The bottom row shows projection images of one single droplet obtained on a confocal microscope formed under various pressures. Please note that in this Figure the numbering (1)-(6) relates to the experiment numbering ((1): experiment at 100 mbar, (2): experiment at 150 mbar, etc.) and the numbers are not the reference signs.

[0068] Figure 3 shows a boxplot summarizing the experimental droplet volumes under the corresponding pressure conditions. The nozzle to spot distance was adjusted as indicated on the upper horizontal axis. Please note that in this Figure the numbering (1)-(6) relates to the experiment numbering ((1): experiment at 100 mbar, (2): experiment at 150 mbar, etc.) and the numbers are not the reference signs.

[0069] Figure 4 shows one embodiment of the apparatus 1 as a 3D-CAD drawing. The plate is herein a glass plate having a patterned top surface 5 with hydrophilic and hydrophobic areas. The plate is mounted on a motorized microscope stage comprising a x-, y- and z-stage or a x-y- and z-stage as the means for moving 8 the capillary 2 and the plate with top surface 5 relatively to each other. The x-y-stage is configured to move the plate, in particular the top surface 5 of the plate in the x-y-plane, wherein the z-stage is configured to move either the capillary 2 and / or the plate along the z-axis allowing to adjust the distance between the top surface 5 of the plate and the second opening 4 of the capillary.

[0070] Figure 5 represents a more detailed view on the apparatus 1 from Figure 4, however the elements shown herein can also be used in any other embodiment of the invention. The top Figure shows a pressurized tube to be attached to the capillary 2 in the sense of a means for providing a positive pressure between the first opening 3 and the second opening 4 of the capillary 2, the pressurized tube also or alternatively being configured for providing the liquid under a desired pressure. The Figure in the bottom shows the capillary 2 arranged over the top surface 5 of the plate. Sidewise to and above the plate, a (side) camera objective is arranged and configured for monitoring the position of the capillary, in particular the distance between the second opening 4 of the capillary 2 and the top surface 5 of the plate and may function itself as the sensor 9 if the distance is determined optically by an operator of the apparatus 1, or it may be operationally connected to a processor or a control unit configured for determining the distance with the help of an implemented software.

[0071] Figure 6 a)shows a schematic overview of the liquid volume, in particular droplet dispensing mechanism. Depicted is the bottom ending of the capillary 2 comprising the second opening 4, the capillary 2 being filled with the liquid to be dispensed (drawn in black in the Figure). The capillary 2 and the top surface 5 of the plate are being moved relatively to each other at a (e.g. constant) distance and / or speed, meaning that the distance and / or speed between the hydrophilic areas and between the hydrophobic areas can remain the same. The liquid exits the second opening 4 of the capillary 2 and, without forming a droplet, contacts the top surface 5 of the plate, in particular at a hydrophilic area 7, a hydrophobic area 6, or both areas at once. Depending on the properties of the liquid (hydrophilic or hydrophobic), the liquid moves to either the hydrophilic area 7 (if the liquid is hydrophilic), or to the hydrophobic area 6 (if the liquid is hydrophobic), driven by the adhesion or intermolecular interactions, such as e.g. London or Van der Waals forces. After wetting a preferred area and forming a pre-droplet (which is an intermediate of a droplet, as for now it is column-shaped), the liquid is still in contact with the second opening 4 of the capillary 2 forming a (distorted) column-like shape in the gap between the top surface 5 of the plate and the second opening 4 of the capillary 2 (3 rd< Figure from the left). After a further movement of the capillary 2, of the top surface 5, or of both, the column-like structure is being sheered-off and a liquid portion finally forms the droplet on the top surface 5.

[0072] Figure 6 b)shows a schematic overview of a gradient formation according to the present method. Decrease of fluid flow through the capillary 2, in particular by a decrease of positive pressure and / or distance between the second opening 4 of the capillary 2 and the top surface 5 of the plate, results in a reduction of droplet volume across the plate (left Figure). Generation of a concentration gradient (middle Figure) for a mixture comprising at least two different liquids, in particular for droplets comprising or consisting of at least two different liquids (a first liquid and a second liquid), is accomplished by dispensing the second liquid onto the droplets of the first liquid deposited on the top surface 5 of the plate and having different volumes of the first liquid, in particular decreasing volumes across the plate. Dispensing the second liquid onto the droplets of the first liquid, in particular by applying an increasing flow, further in particular an increasing pressure throughout the deposition of the second liquid, allows for generating a concentration gradient in the liquid droplets - the concentration of the second liquid (e.g. a buffer) increases from the left to the right. In an embodiment, the gradient formation is used for analysing enzymatic reactions in the droplets (right Figure). REFERENCE SIGNS LIST 1apparatus6hydrophobic area2capillary7hydrophilic area3first opening8means for moving4second opening9sensor5top surface (of the plate)

Claims

1. An apparatus (1) for liquid handling comprising: - a capillary (2) having a first opening (3) and a second opening (4); - a plate having a top surface (5) defining an x-y-plane, the top surface (5) comprising at least one hydrophobic area (6) and at least one hydrophilic area (7), wherein the capillary (2) is configured to receive and / or dispense a liquid from and / or onto the top surface (5) of the plate via the second opening (4), - means for moving (8) the capillary (2) and / or the plate relative to each other in two and / or three dimensions at a distance between the second opening (4) of the capillary (2) and the top surface (5) of the plate, in particular at a distance in the range of 0.1 µm to 500 µm; and - a sensor (9) configured to measure the distance between the second opening (4) of the capillary (2) and the top surface (5) of the plate.

2. The apparatus (1) for liquid handling according to claim 1, wherein the apparatus (1) further comprises means for applying a positive pressure and / or a negative pressure onto the capillary (2), in particular between the first opening (3) and the second opening (4) of the capillary (2); and / or the sensor (9) is a force sensor, an optical sensor, an electrical sensor, or a magnetic sensor.

3. The apparatus (1) for liquid handling according to claim 1 or 2 further comprising a control unit configured to control at least one of: the means for applying a positive pressure and / or a negative pressure; and / or the means for moving (8) the capillary (2) and / or the plate according to the distance between the second opening (4) of the capillary (2) and the top surface (5) of the plate.

4. The apparatus (1) for liquid handling according to any one of the claims 1 to 3, wherein the sensor (9) is arranged at the capillary (2), in particular between the second opening (4) of the capillary (2) and the top surface (5) of the plate, and optionally wherein the sensor (9) and the capillary (2) are together movable with respect to the top surface (5) of the plate, or wherein the sensor (9) is arranged outside an area obtained by an orthogonal projection of the top surface (5) of the plate.

5. A method for liquid handling, in particular dispensing and / or receiving a liquid, the method comprising the following steps, in particular in the given order: a) providing an apparatus (1) according to any one of the claims 1 to 4 and a liquid, in particular a one-phase liquid; b) measuring a distance between the second opening (4) of the capillary (2) and the top surface (5) of the plate by the sensor (9); and c) dispensing the liquid through the capillary (2) via the second opening (4) of the capillary (2) onto the top surface (5) of the plate or receiving the liquid from the top surface (5) of the plate into the capillary (2) via the second opening (4) of the capillary (2).

6. The method for liquid handling according to claim 5, wherein dispensing the liquid from the second opening (4) of the capillary (2) onto the top surface (5) of the plate comprises a step wherein the liquid contacts the top surface (5) of the plate while contacting the second opening (4) of the capillary (2) and wherein the capillary (2) and / or the plate are moved at the distance and relative to each other to shear off a volume of liquid, in particular a droplet, onto the top surface (5) of the plate.

7. The method for liquid handling according to claim 6, wherein moving the capillary (2) and / or the plate at the distance and relative to each other comprises a movement of the plate essentially in the x-y-plane of the plate and / or a movement of the capillary (2) essentially parallel or along a z-axis, the z-axis being essentially perpendicular to the x-y-plane of the plate.

8. The method for liquid handling according to any of claims 5 to 7, wherein the liquid to be dispensed and / or received in step c) is a droplet of liquid, in particular a droplet of a one-phase liquid.

9. The method for liquid handling according to any one of the claims 5 to 8, wherein: the liquid is hydrophobic and is dispensed in step c) on a hydrophobic area (6) of the top surface (5) of the plate or is received in step c) from a hydrophobic area (6) of the top surface (5) of the plate; or the liquid is hydrophilic and is dispensed in step c) on a hydrophilic area (7) of the top surface (5) of the plate or is received in step c) from a hydrophilic area (7) of the top surface (5) of the plate.

10. The method according to any one on the claims 5 to 9, wherein dispensing or receiving the liquid in step c) is supported and / or controlled by the means for applying a positive pressure and / or a negative pressure onto the capillary (2).

11. The method according to any one on the claims 5 to 10, wherein dispensing the liquid in step c) comprises the step of applying a positive pressure between the first opening (3) and the second opening (4) of the capillary (2) and / or receiving the liquid in step c) comprises the step of applying a negative pressure between the first opening (3) and the second opening (4) of the capillary (2).

12. The method according to any one of the claims 5 to 11, wherein dispensing the liquid from the second opening (4) of the capillary (2) or receiving the liquid into the second opening (4) of the capillary (2) in step c) is a continuous dispensing or a continuous receiving, in particular without stopping the flow of the liquid through the second opening (4) of the capillary (2).

13. The method according to any of claims 5 to 12, wherein step b) of measuring a distance is performed by determining a three-dimensional map of the top surface (5) of the plate with the sensor (9) and / or wherein step b) of measuring the distance is repeated at least once, in particular after step a) and / or after step b) and / or after step c).

14. An apparatus (1), in particular the apparatus (1) according to any one of the claims 1 to 4, configured to perform the method steps according to any one of the claims 5 to 13.

15. A use of the apparatus (1) according to any one of the claims 1 to 4, or the method according to any one of the claims 5 to 13 for liquid handling, in particular receiving and / or dispensing a liquid.

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