Sample transfer from droplet arrays using electric fields

Abstract

The present invention relates to a method for transferring a part of a sample without contact, a device for transferring a part of a sample without contact, and the use of the device for transferring a part of a sample.

Description

[0001] The present invention relates to a method for transferring a part of a sample without contact, a device for transferring a part of a sample without contact, and the use of the device for transferring a part of a sample.

[0002] Lab-on-a-Chip (LOC) instruments are micro-laboratories on a single chip, measuring just a centimeter in size, that have been developed over the past few decades for chemical and biological analyses. Key advantages of these devices include rapid analysis, low sample and reagent consumption, and multiplexing capabilities. Droplet microarrays are an example of LOCs and can be used, for instance, for DNA analysis.

[0003] With a large number of analytical samples placed on a droplet microarray, many experiments or analytical protocols can be performed in parallel. A typical (droplet) microarray with circular hydrophilic regions is shown in Figur 1 schematically represented. Overall, these microarrays have the following advantages: Small volumes result in low consumption of rare materials. Parallel modification and characterization make it possible to test a large number of samples in a short time.

[0004] Despite the numerous advantages of droplet microarrays, there is still no reliable method for extracting aliquots to monitor or analyze the progress of processes within the droplets. Aliquot extraction is complicated, among other things, by the large number and small volume of samples available for analysis. This renders conventional tools, such as pipettes, unsuitable.

[0005] In principle, it is possible to perform aliquot extraction using a flat plate that approaches the droplet microarray from above and detaches a portion of the droplet. For the parallel transfer of aliquots from one microarray to another, the so-called "sandwich" method involves bringing two microarrays into contact using a mechanical alignment device.

[0006] Methods based on contact transfer of the droplet with a second microarray do not provide good control over the amount of droplet aspirated. In most cases, a significant portion of the droplet is transferred. In contrast, practical applications prefer transferring very small amounts of the aliquot to allow for successive aliquot extraction. Furthermore, such contact-transfer methods are limited by the potential for droplet contamination and slower aspiration rates.

[0007] The present invention is therefore based on the objective of providing a method for the contactless transfer of a portion of a sample that overcomes the aforementioned disadvantages of known methods for aliquot extraction from microarrays. In particular, a method for the controlled, low-contamination, effective, and parallel transfer of smaller portions of samples is to be enabled.

[0008] This problem is solved by the embodiments characterized in the claims. In particular, the present invention provides a method for the contactless transfer of a portion of a sample, comprising the steps of: providing an arrangement comprising the following components arranged one above the other in this order: a first electrode which is horizontally oriented, a microarray which has a surface with at least one region and carries a sample on at least one region, a sample collector and a second electrode which is oriented parallel to the first electrode, provided that neither the first electrode nor the sample collector touches the sample, and applying an electrical voltage between the first and the second electrode to generate an electric field between the two electrodes, thereby transferring a portion of the sample from the microarray to the sample collector.

[0009] In the inventive method for the contactless transfer of a portion of a sample, the sample is arranged between two parallel electrodes, whereby an electric field acts upon it after an electrical voltage is applied between the two electrodes. The action of the electric field on the sample causes dielectric polarization of the sample.

[0010] The mechanism of dielectric polarization of electrically non-conductive or dielectric materials is shown schematically in Figur 2 As shown, unlike electrically conductive materials, dielectric materials do not contain free charges. Therefore, unlike in electrical conductors, charges in dielectric materials cannot flow in response to the generated electric field, but can only shift slightly from their equilibrium position. This causes the electric field to dielectrically polarize these materials. Due to this dielectric polarization, positive charges within the dielectric material are displaced in one direction and negative charges in the opposite direction. Consequently, two electric charges with opposite signs are locally generated on opposite sides of the material, creating an internal electric field that partially compensates for the external electric field acting on the material.

[0011] If a sample of a dielectric liquid is now in the Figur 3 When exposed to an electric field as shown, negative charges accumulate on the top of the sample. Therefore, a resulting electrostatic force acts on this part of the sample, indicated by a dashed line. If the electric field is strong enough, this resulting force is large enough to overcome the surface tension within the sample, leading to the separation and thus transfer of the top part of the sample, as shown in Figur 3 depicted.

[0012] Other materials, such as water, are conductive, but their response to an applied electric field is similar to that of dielectric materials. The main difference is that charge accumulation in conductive materials is primarily due to the migration of free charges, as opposed to bound charges in a dielectric. Electric fields can also be used in conductive materials to detach and transfer portions of a sample. Thus, the generated electric field can cause a spontaneous transfer of a portion of the sample from the surface of the microarray supporting the sample toward the second electrode.

[0013] The method of the present invention enables the contactless transfer of a portion of a sample, carried by a region of the microarray, by applying a voltage between the first and second electrodes. Specifically, a portion of the sample is transferred from the microarray towards the second electrode and onto the sample collector.

[0014] The contactless transferred portion of the sample can then be subjected to further processes, for example, (bio)chemical analysis. Thus, the contactless transfer method of the present invention allows for the controlled, low-contamination, and efficient transfer of small sample portions at high speed and with a high degree of parallelization.

[0015] For the purposes of the present invention, contactless transfer of a sample portion is understood to mean the transfer of a portion of the sample, carried by a microarray, to another component of the arrangement or device for contactless transfer, without the other component being in contact with the sample or being brought into contact with it. For example, the portion of the sample is transferred contactlessly to the sample collector. The transfer process comprises separating a portion of the sample and accelerating the separated portion toward the sample collector by the electric field, as well as depositing the separated portion of the sample onto the sample collector. In this case, the sample collector is neither in contact with nor being brought into contact with the sample. The transferred portion of the sample can also be referred to as an aliquot.

[0016] The choice of sample is not particularly restricted, as long as it can be dielectrically polarized by the application of an electric field and at least a portion of it can be transferred. To simplify the transfer of this portion of the sample, it is preferably a liquid.

[0017] In a preferred embodiment of the present invention, the sample comprises a dielectric solvent and / or a conductive solvent. Suitable solvents include, but are not limited to, deionized water, aqueous 1 M NaCl solution, PBS buffer, HEPES buffer, TRIS buffer, methanol, ethanol, acetonitrile, dimethylformamide, and dimethyl sulfoxide. These solvents can be sufficiently dielectrically polarized and have a suitable surface tension to facilitate the contactless transfer of a portion of the sample by applying an electrical voltage. Preferably, the sample comprises water or PBS buffer as the solvent.

[0018] In addition to the solvent, the sample may comprise at least one further component. The specific component depends on the intended use of the sample or the transferred portion and can be selected accordingly by a person skilled in the art. Preferably, the component is an analyte or a reagent. For example, the sample may contain at least one component selected from the group consisting of cells, cell components, small molecules, proteins (e.g., peptides, antibodies, enzymes), nucleic acids (e.g., RNA and DNA), lipids, polysaccharides, metabolites, blood serum, blood plasma, lymph fluid, cerebrospinal fluid, urine, saliva, tear fluid, tissue extracts, cell culture media, bacteria, and viruses. Small molecules are defined as molecules with a molecular mass of 800 g / mol or less.

[0019] The sample volume is not limited and can be selected by a person skilled in the art depending on the availability or need of the sample. The sample volume can be similar to the volume of samples on common droplet microarrays.

[0020] In a preferred embodiment of the present invention, the sample volume is 100 pL to 100 µL, preferably 100 nL to 10 µL. Here, the sample volume refers to the total volume of the sample. A liquid sample of such a volume typically forms a droplet. Therefore, in the process according to the invention, the sample can be a droplet. If several samples are partially transferred simultaneously in the process, the samples can have approximately the same volume, e.g., the sample volumes each lie within a range of + / - 10%, preferably + / - 5%, even more preferably + / - 1%, based on the average of the volumes of all samples.

[0021] A sample portion is understood to be a partial portion or aliquot of the sample. This portion has the same composition as the sample itself but a smaller volume. The volume of the transferred sample portion is not further limited and can be chosen by a person skilled in the art depending on the availability of the sample and the intended use of the transferred portion. For example, the transferred sample portion may comprise 1% to 10% of the sample's volume. Therefore, the transferred sample portion may, for example, have a volume of 1 pL to 10 µL, preferably 1 nL to 1 µL. If, in the non-contact sample transfer method, portions are transferred simultaneously from several samples, the volume refers to the average volume of the individual transferred portions.

[0022] The volume of the transferred portion of the sample and the average volume of the individual transferred portions can be determined gravimetrically. If the density of the sample is unknown, the density of the solvent can be used as an approximation for gravimetric volume determination. The volume of the transferred portion of the sample can also be determined by analyzing the height of the transferred portion (droplet volume) using optical methods and calculating the volume based on the shape of the droplet formed from the transferred portion (ball cap), provided the contact area and contact angles of the droplet are known. Alternatively, the volume of the transferred portion of the sample can be determined by fluorescence measurement, using the fluorescence intensity as a function of volume obtained in a calibration experiment.

[0023] The method according to the invention comprises the step of providing an arrangement which includes a first electrode which is horizontally oriented, a microarray which has a surface with at least one region and carries a sample on at least one region, a sample collector and a second electrode which is oriented parallel to the first electrode, arranged one above the other in this order, with the proviso that neither the first electrode nor the sample collector touches the sample, and a step of applying an electrical voltage between the first and the second electrode in order to generate an electric field between both electrodes, whereby a part of the sample is transferred from the microarray to the sample collector.

[0024] The surface and at least one region of the microarray are not particularly restricted with regard to their properties, as long as the at least one region of the surface can support a sample. The properties of the region can be determined by the material from which the microarray is formed or by a modification of the surface. For example, the surface can be wholly or partially modified to be hydrophilic and / or hydrophobic in order to provide hydrophilic and / or hydrophobic regions.

[0025] In a preferred embodiment, the at least one region is at least one hydrophilic region. That is, the arrangement includes a microarray having a surface with at least one hydrophilic region, and carrying a sample on at least one hydrophilic region.

[0026] When an electric field acts on a sample supported by a non-hydrophilic surface, the sample can move along the surface. Such movement can make reproducible, non-contact transfer of a portion of the sample difficult or even impossible. The non-contact transfer of a sample portion—especially with regard to its reproducibility—can be improved if the sample is supported on a hydrophilic region of the microarray surface.

[0027] In a further preferred embodiment, the at least one hydrophilic region is enclosed by a hydrophobic region. In this case, the microarray has a surface with at least one hydrophilic region enclosed by a hydrophobic region, and the sample is carried on the at least one hydrophilic region. Enclosing the at least one hydrophilic region with the hydrophobic region can further suppress movement along the surface of the carried sample and thus increase the reproducibility of transferring a portion of the sample, for example, during sampling.

[0028] Additionally, a microarray having a surface with at least one hydrophilic region enclosed by a hydrophobic region can be used in subsequent experiments, for example in cell cultures, biochemical assays, or analytical procedures. This saves resources. The same applies to the sample collector if it has a surface with at least one hydrophilic region or a surface with at least one hydrophilic region enclosed by a hydrophobic region.

[0029] Preferably, in the method according to the invention, the step of providing the arrangement is carried out before the step of applying the electrical voltage.

[0030] For the purposes of the present invention, an arrangement is understood to be a grouping of certain elements in a predetermined manner. Therefore, the arrangement of the components can be understood as both an arrangement of the components and a grouping of the components. The components are positioned in the manner specified.

[0031] The arrangement comprises, but is not limited to, the first electrode, the microarray, the sample collector, and the second electrode. These are arranged one above the other in the sequence first electrode - microarray - sample collector - second electrode. For the purposes of the present invention, "arranged one above the other" means that the components are arranged vertically. That is, the first electrode, the microarray, the sample collector, and the second electrode are arranged vertically in this order from bottom to top.

[0032] The positioning of the individual components within the arrangement is not particularly restricted, as long as the first electrode, the microarray, the sample collector and the second electrode are arranged one above the other and part of the sample can be transferred from the microarray to the sample collector by the applied voltage, which generates an electric field.

[0033] Since the first electrode is horizontally aligned and the second electrode is aligned parallel to the first electrode, the second electrode is also horizontally aligned.

[0034] In the context of the present invention, a horizontal orientation means that the surface of a component which has the largest area in a two-dimensional projection extends substantially horizontally, preferably horizontally.

[0035] While not limited to this, the microarray and the sample collector can also be aligned parallel to each other. For the purposes of the present invention, a parallel alignment of two components can mean that the surfaces of several components, each having the largest area in a two-dimensional projection, are substantially parallel to each other, preferably parallel. A parallel alignment of the microarray and the sample collector enables the efficient transfer of a portion of the sample from the microarray to the sample collector.

[0036] Preferably, the microarray and / or the sample collector are horizontally oriented. Therefore, in the arrangement, the first electrode, the microarray, the sample collector, and the second electrode can be horizontally oriented, but are not limited to this.

[0037] To generate the most homogeneous electric field possible, the first and second electrodes are preferably arranged congruently above one another. This means that the first and second electrodes can have the same dimensions and identical shape and are offset from each other only in a vertical direction, but not in a horizontal direction.

[0038] The positioning of the microarray relative to the two electrodes is not particularly restricted. The microarray should be positioned between the electrodes such that a portion of the sample can be transferred by the electric field present between the electrodes. Preferably, the microarray is located entirely between both electrodes. In this case, the microarray is not offset from the two electrodes in a horizontal direction and is smaller than both electrodes combined. In this context, the size of the microarray and the electrodes refers to the dimension of a surface of the microarray / electrodes in the horizontal plane. The size of the microarray / electrodes can also be determined by the area of ​​the main surface of the microarray / electrodes facing each other. The area of ​​each main surface is determined by its flat, i.e., two-dimensionally projected, shape.

[0039] The microarray can therefore be located entirely within the space extending between the first and second electrodes. Nevertheless, in the arrangement of the method of the present invention, the microarray is not limited to a specific position within the arrangement and constitutes a comprehensive component for supporting a sample to be divided.

[0040] Preferably, the microarray is arranged directly on a surface of the first electrode, without being confined to it. The microarray can be arranged entirely on a surface of the first electrode without projecting beyond it in a horizontal direction.

[0041] The second electrode can be positioned directly on a surface of the sample collector or be rigidly connected to its surface. For example, the second electrode can be rigidly connected to the surface of the sample collector by being applied to it.

[0042] Additionally, the arrangement fulfills the requirement that neither the first electrode nor the sample collector touches the sample. To ensure that the first electrode does not touch the sample, the surface of the microarray containing the at least one sample-bearing region can be the surface of the microarray facing away from the first electrode. This surface corresponds to the surface of the microarray facing the sample collector. That is, the sample carried by the microarray is located on the surface of the microarray facing the sample collector. If the at least one sample-bearing region is a hydrophilic region, the microarray has this hydrophilic region on the surface facing away from the first electrode or towards the sample collector.

[0043] In this arrangement, the sample collector is positioned above the surface of the microarray, which has at least one region, without touching the sample itself. This can be achieved by positioning the sample collector at a sufficient distance from the microarray. The distance between the microarray and the sample collector creates a gap between them. If the at least one region supporting a sample is a hydrophilic region, the sample collector is positioned accordingly above the surface of the microarray, which has at least one hydrophilic region, without touching the sample itself.

[0044] Preferably, the sample collector is positioned directly above the microarray. Both are therefore aligned perfectly. This alignment of the microarray and the sample collector ensures that the transferred portion of the sample can be reliably deposited onto the sample collector.

[0045] The distance between the microarray and the sample collector is not further restricted, as long as the distance is large enough to prevent the sample collector from coming into contact with the sample, and small enough to allow the transfer of a portion of the sample. To satisfy both conditions, the distance between the microarray and the sample collector is preferably 1 to 10 mm, more preferably 2 to 5 mm. Because the sample collector, which faces the surface of the microarray having the at least one region, is not in contact with the sample, the portion of the sample can only be transferred without contact in the method of the present invention.

[0046] In a preferred embodiment of the present invention, the arrangement comprising the first electrode, the microarray, the sample collector and the second electrode is not moved to transfer part of the sample to the sample collector.

[0047] In this arrangement, the distance between the first and second electrodes is not particularly restricted. Depending on the required electric field strength and the thicknesses of the components of the arrangement, a person skilled in the art can select the distance between the two electrodes appropriately. To achieve a sufficiently high electric field strength for transferring the sample portion and simultaneously allow for the aforementioned arrangement of components, the distance between the first and second electrodes can be from 0.5 to 20 mm, preferably from 1.0 to 10 mm.

[0048] The first and second electrodes are not restricted in shape, size, or material, as long as they can generate an electric field when an electric voltage is applied. Both electrodes can be identical or different in shape, size, and material.

[0049] With regard to shape, neither the first nor the second electrode is particularly restricted. To generate an electric field between the electrodes, it is advantageous if both electrodes have a shape suitable for forming a capacitor. Preferably, both electrodes independently have a circular or polyhedral shape. Polyhedral electrodes are, for example, hexagonal, pentagonal, rectangular, or square, particularly square.

[0050] In a preferred embodiment, the first electrode and the second electrode have the same shape and are circular, rectangular or square, particularly preferably circular.

[0051] The shape of the electrode refers here to the geometry of a surface of the electrode, preferably the main surface of the electrode facing the microarray or the sample collector. The main surface of an electrode refers to a surface of the electrode that extends in the horizontal plane of the arrangement.

[0052] At least one of the surfaces of the first electrode and / or the second electrode can be flat. If a surface of the first electrode and / or the second electrode is flat, preferably the surface facing the microarray or the sample collector is flat. Due to the arrangement of the components, one surface of the first electrode and one of the second electrodes facing the microarray or the sample collector, respectively, are primary surfaces. Particularly preferably, both primary surfaces of the first electrode and the second electrode are flat. Flat primary surfaces of the electrodes facilitate the setup of the arrangement and generate a homogeneous electric field after the application of the electric voltage.

[0053] Preferably, all horizontally extending surfaces of the first electrode and the second electrode are flat.

[0054] One of the electrodes may be smaller than the other; preferably, both electrodes are the same size. In this context, the size of an electrode refers to the dimension of one of its surfaces in the horizontal plane. The size of the electrode can also be determined by the area of ​​the main surface of the respective electrode facing the microarray or sample collector. The area of ​​the main surface is determined in its flat, i.e., two-dimensionally projected, form.

[0055] It is particularly desirable for both electrodes to be identical. In this case, both electrodes have the same shape and size.

[0056] In a preferred embodiment, the first electrode and the second electrode are each a capacitor plate, which together can form a capacitor.

[0057] The thickness of the first and second electrodes is not particularly restricted. The first and second electrodes can have the same or different thicknesses. Preferably, the first electrode has a greater thickness than the second electrode. A thicker first electrode is more stable and reliably supports the microarray if the microarray is arranged directly on the first electrode. With regard to load-bearing properties, the first and / or the second electrode can have a thickness of 0.50 mm to 5.0 mm, more preferably 1.0 mm to 4.0 mm, and most preferably 2.0 mm to 3.0 mm. For improved transparency, the first and / or the second electrode can have a smaller thickness. In this case, the first and second electrodes, or the deposited electrode, preferably have a thickness of 5 nm to 1 mm, more preferably 10 nm to 500 µm, and most preferably 50 nm to 200 µm, independently of each other.

[0058] In the present invention, the thickness can generally be understood as the extent perpendicular to a principal surface of a component. The principal surface refers to a surface of a component that extends in the horizontal plane of the arrangement. If a component is horizontally oriented, its thickness corresponds to its extent in the vertical direction, and the principal surface corresponds to a surface extending in the horizontal plane.

[0059] The specific materials of the first and second electrodes are not particularly restricted, as long as both electrodes are made of a sufficiently electrically conductive material to allow a sufficiently high voltage to be applied to them in order to generate an electric field between the two electrodes that is strong enough to transfer a portion of the sample. Electrodes typically comprise an electrical conductor, a semiconductor, or conductive polymers. To improve their electrical properties, the electrodes can be made of either an electrical conductor or a semiconductor. Electrical conductors, semiconductors, and conductive polymers suitable for use in electrodes are well known to those skilled in the art.

[0060] The electrical conductor can be at least one selected from the group consisting of a metal, graphite, and carbon nanotubes. Preferably, the electrical conductor is a metal. The metal can be, for example, aluminum, copper, tantalum, niobium, or alloys thereof, most preferably aluminum or copper. Preferably, the first electrode is an electrode made of a metal, more preferably aluminum.

[0061] Suitable semiconductors for the electrodes include, for example, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), niobium-doped anatase TiO₂ (NTO), and doped zinc oxide. Indium tin oxide is preferred as the semiconductor. Preferably, the semiconductor is transparent. An electrode made of a transparent semiconductor allows the transfer of the sample portion to be visually monitored. For the purposes of this application, a semiconductor is transparent if it has a transmission of at least 84% in the visible wavelength range (400 to 700 nm) when it is in the form of a 100 nm thick layer. Examples of transparent semiconductors are indium tin oxide (ITO). Preferably, the second electrode is transparent and consists of a transparent semiconductor, preferably indium tin oxide (ITO).

[0062] Suitable conductive polymers include poly(3,4-ethylenedioxythiophene) (PEDOT), poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), poly(4,4-dioctylcyclopentadithiophene), polyaniline (PANI), polypyrrole (PPy), poly(thiophene), and poly(p-phenylenediamine) (PPDA). These polymers offer a wide range of electrical and mechanical properties that can be optimized for specific applications. It is also possible to use conductive polymers such as polyfluorene, polyacetylene, and polythiophene, which are frequently used in biomedical applications due to their flexibility and conductivity. A single type of conductive polymer or several types—i.e., mixtures of conductive polymers—can be used as the electrode to precisely control the coating properties, such as conductivity, stability, and flexibility.

[0063] In a preferred embodiment, the second electrode is made of indium tin oxide.

[0064] A microarray within the meaning of the present invention is understood to be a solid substrate with a surface comprising at least one area, also called a spot, on at least one surface of the microarray. The areas define positions on which samples can be placed. The areas can be arranged in a regular pattern.

[0065] If the at least one region is a hydrophilic region, a microarray within the meaning of the present invention is understood to be a solid substrate with a surface layer comprising at least one hydrophilic region, also called a spot. The optional hydrophilic regions define positions on which samples can be placed. If present, the hydrophilic regions can be arranged in a regular pattern. A photolithographic process can be used to produce such patterns.

[0066] Optionally, the surface layer also has a hydrophobic area (hydrophobic border) that surrounds the at least one optional hydrophilic area. In this case, it can also be referred to as a patterned surface layer or a patterned surface.

[0067] Preferably, a main surface of the microarray has a surface with at least one region, the surface layer having at least one hydrophilic region, or the patterned surface layer having at least one hydrophilic region enclosed by a hydrophobic region, particularly preferably the main surface facing the sample collector.

[0068] The thickness of the microarray is not particularly restricted and can be any value, as long as the microarray can be provided in the arrangement. Preferably, the thickness of the microarray is 0.1 to 2 mm, more preferably 0.5 to 1.0 mm.

[0069] The shape of the microarray is not particularly restricted. Preferably, the microarray has the same shape as the first electrode and / or the second electrode, preferably as both electrodes. That is, the microarray can have a circular or polyhedral shape. A polyhedral microarray is, for example, hexagonal, pentagonal, rectangular, or square, particularly square. The shape of the microarray here refers to the geometry of a surface of the microarray, preferably the main surface of the microarray facing the sample collector. The main surface of the microarray refers to a surface of the microarray that extends in the horizontal plane of the arrangement. Preferably, the surface of the microarray comprising the at least one region is flat.

[0070] The surface layer can be, for example, in the form of a foil, film, or coating. The substrate is not particularly restricted and can be any substrate that is preferably solid in a temperature range of -30°C to 130°C, more preferably in a temperature range of 0°C to 40°C, and most preferably at room temperature. The solid substrate can, for example, be made of glass or plastic. In a preferred embodiment, the solid substrate is transparent, with a glass substrate being preferred. The solid substrate preferably has a flat surface, more preferably a flat main surface.

[0071] The microarray regions are not particularly restricted in their shape and can be circular, star-shaped, or polygonal (triangular, rectangular, pentagonal, or hexagonal). Preferably, the regions are circular or rectangular. Regions with a triangular, hexagonal, or rectangular shape allow for a close arrangement of the regions on the substrate. Nevertheless, a microarray according to the present invention is not limited to a specific arrangement of regions and represents a comprehensive approach for generating defined arrays of individual samples of equal volume on the surface of a substrate. The same applies to the hydrophilic regions, if present.

[0072] The regions can be, for example, triangular or rectangular with a side length of 5 mm or less, preferably 3 mm or less, more preferably 1 mm or less, and even more preferably 500 µm or less. The regions can be circular with a diameter of 5 mm or less, preferably 3 mm or less, more preferably 2 mm or less, even more preferably 900 µm or less, and most preferably 500 µm or less. Neither the side length in the case of triangular or rectangular regions nor the diameter of circular regions is particularly restricted, as long as the sample as a whole can be contained within them. For example, the side length or diameter may be 10 µm or more, preferably 50 µm or more, more preferably 100 µm or more, and even more preferably 200 µm or more. The upper and lower limits of the side length or diameter may be combined as desired.The same applies to hydrophilic areas, if any.

[0073] If present, the hydrophobic region which can enclose the optional at least one hydrophilic region can have a width of 1 mm or less, more preferably 0.5 mm or less and most preferably 0.1 mm or less between two adjacent hydrophilic regions.

[0074] Furthermore, the thickness of the surface layer or the patterned surface layer, if present, is not limited. With regard to transparency properties and the reduction of manufacturing costs, the (patterned) surface is preferably thin. In particular, a thickness of 45 µm or less is preferred, more preferably 30 µm or less, and most preferably 15 µm or less.

[0075] In general, surfaces can be classified as hydrophilic or hydrophobic depending on their contact angle with water. A surface with a static contact angle of at least 90° is considered hydrophobic, while a surface with a static contact angle of less than 90° is considered hydrophilic. A distinction is regularly made between two different contact angles: a static and a dynamic contact angle. Static contact angles (θstat) are determined by placing a drop on a surface and measuring the contact angle of the droplet at rest with the surface using a goniometer or a camera with specialized software. (sessile drop Measurement). Dynamic contact angles, on the other hand, represent contact angles outside of an equilibrium state and are measured during the advance (θ adv) or retraction (θ rec) of a droplet. The difference between θ adv and θ rec is called contact angle hysteresis.

[0076] In a preferred embodiment of the present invention, hydrophobic areas have a static water contact angle of at least 90°, preferably more than 95°, more preferably more than 100° and most preferably more than 110°.

[0077] In a further preferred embodiment, the hydrophobic region(s), if present, of a microarray is superhydrophobic and / or the hydrophilic region(s), if present, is superhydrophilic. In a preferred embodiment of the present invention, superhydrophobic regions have a static water contact angle of more than 130°, preferably more than 140°, and more preferably more than 150°. Furthermore, superhydrophilic regions preferably have a water contact angle of less than 30°, more preferably less than 20°, and most preferably less than 10°.

[0078] The hydrophobic regions of a microarray can be hydrophobic, omniphobic, or superhydrophobic. Similarly, the hydrophilic regions can be hydrophilic, omniphilic, or superhydrophilic. Here, "omniphobic" refers to a surface's property of repelling all liquids, while "omniphilic" describes surfaces that are wetted by all liquids.

[0079] The microarray of the present invention is capable of carrying at least one sample on its (patterned) surface. In a preferred embodiment, a microarray is suitable for carrying at least 1 sample per cm² of the (patterned) surface, more preferably at least 10 samples per cm² of the (patterned) surface, even more preferably at least 50 samples per cm² of the (patterned) surface, and most preferably at least 100 samples per cm² of the (patterned) surface. The upper limit of the number of samples per cm² of the (patterned) surface is not particularly restricted and can be determined according to requirements.However, in order to simplify the method of the present invention and to avoid cross-contamination of adjacent samples, it is preferred that a microarray carries at most 1000 samples per cm² of the (patterned) surface, more preferably at most 100 samples per cm² of the (patterned) surface, and even more preferably at most 20 samples per cm² of the (patterned) surface.

[0080] The sample can be applied to the surface, or the patterned surface if present, of the microarray using known methods. Application can be manual or automated, for example. Automated application is preferred. Application can be achieved, for example, by discontinuous wetting. Methods using [methods] are particularly noteworthy. rolling droplet, standing droplet, liquid dispensing, printing, ink-jet printing, contact printing, Pipetting, or immersion and removal of the microarray from a solution. However, the method of application according to the present invention is not particularly limited, and a person skilled in the art can select the most suitable method depending on the objective.

[0081] At the rolling droplet In this method, a drop of the sample to be applied is rolled over the (patterned) surface of the microarray, causing droplets with a defined geometry and volume to form spontaneously in the (hydrophilic) areas. This allows for the targeted application of the sample to specific areas of the microarray, and it is possible to apply different samples to different (hydrophilic) areas of the microarray.

[0082] At the standing droplet In this method, the (patterned) surface of the microarray is coated with a solution of the sample to be applied, and the excess solution is tipped off to the side, causing droplets with a defined geometry and volume to form spontaneously in the (hydrophilic) areas. The relatively simple procedure of standing droplet However, this method requires a larger sample volume compared to the rolling droplet This method requires that the entire (patterned) surface of the microarray be layered, and all generated samples contain the same solution.

[0083] At the liquid dispensing In this method, a droplet is formed at the nozzle outlet and then transferred. This transfer can occur through contact with the microarray while the droplet is still on the nozzle. (contact liquid dispensing) or the droplet is formed far enough away from the microarray and only hits the microarray after it has detached from the nozzle. (non-contact liquid dispensing).

[0084] methods zum printing, ink-jet printing, contact printing Pipetting is sufficiently familiar to the expert.

[0085] Basically, there are two different types of microarrays with optional hydrophilic regions, which differ in the type of (patterned) surfaces and can be selected by a person skilled in the art based on the solvent to be used. For aqueous solvents with a high surface tension (more than 70 mN m⁻¹), the following are generally used: high surface tension liquids (HSTL) microarrays are used, whereas for organic solvents with a lower surface tension (less than 40 mN m -1< ) low surface tension liquids (LSTL) microarrays are used.

[0086] An HSTL microarray can be manufactured, for example, by a process that includes the following steps: (a) Providing a polymerization mixture between two solid supports; (b) Polymerizing the polymerization mixture to form a porous polymer layer; (c) Removing one of the two solid supports; and (d) Modifying the surface of the porous polymer layer, thereby forming the (patterned) surface comprising hydrophilic regions, each optionally enclosed by a hydrophobic region.

[0087] For example, photoinitiated copolymerization of 2-hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA) on a glass substrate can form a porous polymer layer that significantly increases the surface area and, through the presentation of numerous hydroxyl groups, greatly enhances the substrate's hydrophilicity. These hydroxyl groups can then be esterified with 4-pentinic acid and thus selectively functionalized using a photomask via a thiol-yne reaction: In an optional first step, hydrophobic borders can be created with perfluorodecanethiol (PFDT), and in a second step, hydrophilic regions can be generated using mercaptoethanol. The optional hydrophobic and necessary hydrophilic properties are achieved through the increased surface area of ​​the polymer.

[0088] Alternatively, suitable hydrophilic and / or hydrophobic nanoparticles can be applied to the porous polymer layer to create the (patterned) surface. Suitable methods for this are known to those skilled in the art, for example, the methods described in EP 3 733 277 A1. Without being limited to these, the following method can be used: To prepare a silica sol solution, 0.25 g of silica nanoparticles (Aerosil 200) are mixed with 30 mL of ethanol. The mixture is treated in an ultrasonic bath for 30 minutes. Subsequently, 0.33 g of vinyltrimethoxysilane and 200 µL of concentrated HCl are added to the solution. The mixture is treated in an ultrasonic bath for a further 60 minutes. Afterward, the solution is left to stand in a dark place for 24 hours.

[0089] For coating the substrate, a glass slide (or other suitable substrate) is placed in a spin coater. 500 µL of the prepared silica sol solution is applied to the substrate. The substrate is then coated at 1500 rpm for 15 seconds. This process is repeated five times to ensure uniform coating. The coated slide is then dried at 130–200°C for one hour.

[0090] For the hydrophobic modification, a 10% solution of 1H,1H,2H,2H-perfluorodecanethiol in acetone is prepared. The solution is applied evenly to the coated glass slide. A quartz plate is placed over the slide to prevent the formation of air bubbles. The slide is irradiated with UV light (260 nm, ~5 mW / cm²) for 30 seconds. After irradiation, the quartz plate is removed, and the slide is washed with ethanol and dried with nitrogen.

[0091] For the hydrophilic modification, a 10% cysteamine or 2-mercaptoethanol solution in ethanol is prepared. This solution is applied to the coated slide, which is then covered again with a quartz plate. The slide is irradiated again with UV light (260 nm, ~5 mW / cm²) for 30 seconds. After irradiation, the quartz plate is removed, the slide is washed with ethanol, and dried with nitrogen.

[0092] To create specific patterns, a photomask with the desired design is placed over the coated slide. The slide is then irradiated with UV light (260 nm) through the photomask to selectively modify specific areas. The slide is subsequently washed with acetone and ethanol to remove any unreacted thiols.

[0093] To verify the surface properties, the water contact angle (WCA) is measured to confirm the hydrophobicity and hydrophilicity of the patterned areas. Hydrophobic areas should preferably have a WCA greater than 90°, while hydrophilic areas should preferably have a WCA less than 20°.

[0094] For the fabrication of an LSTL microarray, additional polymerization on the substrate surface can be omitted. In general, the fabrication of an LSTL microarray comprises the following steps: (A) Providing a substrate comprising a surface having hydroxyl groups; (B) Contacting the surface having hydroxyl groups with a halogenated dialkyl alkenyl silane to form dialkyl alkenyl silyl groups on the surface; (C) Optionally, selectively reacting the alkenyl groups of some of the dialkyl alkenyl silyl groups with a hydrophobic thiol to obtain hydrophobic thioether groups; and (D) reacting the alkenyl groups of the (remaining) dialkyl alkenyl silyl groups with a hydrophilic thiol to obtain hydrophilic thioether groups.

[0095] To create optional hydrophilic regions enclosed by a hydrophobic area, a glass surface can be modified with chlorodimethylvinylsilane and patterned using a photochemical thiol-ene reaction. PFDT is used to form the hydrophobic boundaries, while cysteamine hydrochloride is used for the hydrophilic regions.

[0096] The method of the present invention provides an arrangement comprising a microarray having a surface with at least one region, optionally at least one hydrophilic region and optionally enclosed by a hydrophobic region, and carrying a sample on at least one (hydrophilic) region. Microarrays with at least one optional hydrophilic region can be produced according to the method described above. The number and arrangement of the regions or the optional hydrophilic regions are not particularly limited.The number of optional hydrophilic regions can be at least 1 per cm² of the (patterned) surface of the microarray, more preferably at least 4 per cm² of the (patterned) surface of the microarray, even more preferably at least 8 per cm² of the (patterned) surface of the microarray, and most preferably at least 16 per cm² of the (patterned) surface of the microarray. The regions, or the optional hydrophilic regions, are preferably arranged in a regular pattern, for example, in rows and columns.

[0097] Furthermore, the application of a sample to at least one region or optional hydrophilic region can be carried out as described above. Preferably, the sample is applied to more than one region or optional hydrophilic region of the (patterned) surface, preferably to more than 5, 10, 20, 50, 100, or 500 regions or hydrophilic regions, and more preferably to all hydrophilic regions, if any. Alternatively, the solution is applied to at least 5, 10, 15, 20, 30, 50, or 75% of the regions or optional hydrophilic regions, and more preferably to 100% of the hydrophilic regions, if any.

[0098] To obtain a microarray that carries a sample on at least one region or optional hydrophilic region, a solution containing the sample or corresponding to it in composition can be applied. Alternatively, the corresponding components of the sample can be present in dry form on the at least one region or optional hydrophilic region of the microarray. These components dissolve upon application of a suitable solvent to the microarray, thus forming the sample.

[0099] A sample collector within the meaning of the present invention is understood to be a solid support onto which a portion of the sample can be transferred. The sample collector is therefore suitable for allowing a portion of the sample to be deposited on its surface. The solid support can, for example, be made of glass or plastic. In a preferred embodiment, the solid support is transparent, with a glass support being preferred. The solid support, and thus also the sample collector, preferably has a flat surface, preferably a flat main surface that may face the microarray.

[0100] The sample collector can also serve to prevent electrical arcing between the electrodes. Therefore, the sample collector can, for example, be made of an electrically insulating material and extend completely through the space between the first and second electrodes. In this case, the sample collector acts as an insulator between the two electrodes. Examples of electrically insulating materials include glass and electrically insulating plastics such as polypropylene, polyethylene, and polydimethylsiloxane.

[0101] The thickness of the sample collector is not particularly restricted and can be any value, as long as the sample collector can be provided in the arrangement. Preferably, the thickness of the sample collector is 100 µm to 2 mm, more preferably 200 µm to 1 mm, for example 500 µm.

[0102] In a preferred embodiment, the sample collector is a glass plate with a thickness of 500 µm.

[0103] The surface of the sample collector can be modified or unmodified. If a surface of the sample collector is modified, preferably the surface facing the microarray is modified. A modified surface of the sample collector has a surface layer comprising at least one hydrophilic region, or a patterned surface layer comprising at least one hydrophilic region, each of which is enclosed by a hydrophobic region (hydrophobic border). The descriptions for the microarray apply accordingly to the (patterned) surface layer, the at least one hydrophilic region, and the hydrophobic region of the sample collector.

[0104] If a surface of the sample collector is modified and at least one region of the microarray is hydrophilic, the microarray and the sample collector are preferably aligned so that each hydrophilic region of the microarray corresponds to a hydrophilic region of the sample collector. In this arrangement, a portion of the sample is transferred from the microarray to a specific section of the sample collector in a controlled manner. The opposing hydrophilic regions of the microarray and the sample collector can be identical in shape and size. The aligned arrangement of the hydrophilic regions on the microarray and the sample collector prevents cross-contamination between the transferred portions of the sample and simplifies further handling of the transferred portions.

[0105] The surface of the sample collector facing away from the microarray, preferably the main surface facing away from the sample collector, can be coated with the second electrode. In this case, the sample collector and the second electrode are rigidly connected. If the second electrode is thin or mechanically weak, it is stabilized by the connection to the sample collector. If the sample collector is coated with the second electrode, the second electrode is preferably deposited entirely onto the sample collector. For example, the second electrode is deposited as a 100 nm thick indium tin oxide layer on the sample collector. For this purpose, the sample collector and the second electrode can be congruent, i.e., have the same shape and size, or the second electrode can be smaller than the sample collector.

[0106] In this context, the size of the sample collector and the second electrode refers to the dimensions of a surface of the sample collector / second electrode in the horizontal plane. The size of the sample collector / second electrode can also be determined by the area of ​​the main surface of the sample collector / second electrode facing the sample collector or second electrode. The area of ​​the respective main surface is determined in its flat, i.e., two-dimensionally projected, form.

[0107] The arrangement may include at least one further component. If at least one further component is included in the arrangement, it is appropriately positioned between or above the other components.

[0108] For example, the arrangement may additionally include at least one spacer. The at least one spacer, if included, can be used to adjust the distance between two components of the arrangement. If at least one spacer is included, it may be arranged between the first electrode and the sample collector and / or between the first electrode and the second electrode. The at least one spacer, if present, is in contact with both components between which it is arranged. In the provided arrangement of the method according to the invention, one spacer may be arranged between the first electrode and the sample collector, and another spacer may be arranged between the first electrode and the second electrode.

[0109] Furthermore, the assembly can include a clamping ring. The clamping ring can grip the other components of the assembly and secure it.

[0110] Furthermore, the setup can include a camera. If present, the camera is positioned above the second electrode and pointed towards the sample collector. In this case, the second electrode is transparent. The camera allows monitoring of the sample transfer process.

[0111] The method for contactless transfer of a part of a sample according to the present invention further comprises a step of applying an electrical voltage between the first and the second electrode to generate an electric field between the two electrodes, thereby transferring a part of the sample from the microarray to the sample collector.

[0112] Methods for applying an electrical voltage between the first and second electrodes are well known to those skilled in the art. For example, the electrical voltage can be applied by means of a voltage source. In this case, the first electrode is connected to one pole and the second electrode to the other pole of the voltage source.

[0113] The magnitude of the electrical voltage is not particularly limited, as long as it generates a sufficiently strong electric field to transfer a portion of the sample. For this purpose, an electrical voltage of 4.0 kV to 12 kV can be applied, for example. A voltage of 5.0 kV to 8.0 kV is more preferably applied. The electrical voltage is preferably applied as a direct current voltage or a voltage pulse. Nevertheless, the voltage is not limited according to the present invention and represents a comprehensive means for the contactless transfer of a portion of a sample.

[0114] In the inventive method for the contactless transfer of a part of a sample, the applied voltage can generate an electric field with a field strength of 800 kV / m to 2400 kV / m, preferably from 1000 kV / m to 1600 kV / m.

[0115] In a preferred embodiment of the present invention, the generated electric field has a field strength of 800 kV / m to 2400 kV / m, preferably of 1000 kV / m to 1600 kV / m.

[0116] The duration of applying the electrical voltage or generating the electric field between the two electrodes is not further limited, as long as a portion of the sample can be transferred contactlessly from the microarray to the sample collector. For example, the duration can range from 0.9 seconds (s) to 4 minutes (m), preferably from 1.0 to 50 seconds.

[0117] Applying a voltage between the first and second electrodes generates an electric field between them. This electric field leads to dielectric polarization of the sample and a spontaneous transfer of a portion of the sample. In this context, transferring a portion of the sample from the microarray to the sample collector means that, due to the action of the electric field, a portion of the sample is detached, moves along the field lines towards the second electrode, and is deposited on the surface of the sample collector facing the microarray.

[0118] Preferably, the electric field is generated by a capacitor. In this case, the first and second electrodes are capacitor plates.

[0119] In the method of the present invention, the volume of the transferred portion of the sample can be influenced by several parameters of the provided arrangement and the applied electrical voltage. For example, the volume of the transferred portion of the sample is influenced by the size and shape of the at least one region, the contact angle between the sample and the surface of the microarray, the volume of the sample, the strength of the electric field, and the conductivity of the sample. Therefore, the method of the present application offers a high degree of flexibility to vary the volume of the transferred portions of the sample.

[0120] The method for contactless transfer of a part of a sample of the present invention may include further steps.

[0121] For example, after a portion of the sample has been transferred, the electrical voltage can be switched off. Without being limited to this, in the inventive method, the sample collector containing the transferred portion of the sample can then be replaced with a new sample collector, and a further portion of the sample can be transferred to the new sample collector by reapplying the electrical voltage. The method for the contactless transfer of a portion of a sample can be carried out several times in succession on the same sample (with a reduced volume).

[0122] After transferring part of the sample, a further step may follow, which concerns the use of the transferred part of the sample.

[0123] The contactless transfer method of the present invention is particularly suitable for extracting cell samples, small molecules, proteins, peptides, nucleic acids, lipids, polysaccharides, antibodies, enzymes, metabolites, blood serum, plasma, lymph fluid, cerebrospinal fluid, urine, saliva, tear fluid, tissue extracts, and cell culture media from a (droplet) array for analysis and for extracting multiple aliquots for diagnostic purposes. For these applications, contactless aliquot extraction is essential to avoid contamination of the sample(s). Contamination of the sample through the extraction of an aliquot, for example, through contact of the sample with other objects, as well as cross-contamination between different samples, can be prevented with the method according to the invention. Nevertheless, the method according to the invention allows for the parallel and efficient extraction of a portion from several samples.

[0124] In a preferred embodiment of the present invention, the transferred portion of the sample is used for analysis, diagnostic purposes, or screening procedures. Therefore, the method of the present invention can be used to extract cell samples, cell components, small molecules, proteins, peptides, nucleic acids, lipids, polysaccharides, antibodies, enzymes, metabolites, blood serum, plasma, lymph fluid, cerebrospinal fluid, urine, saliva, tear fluid, tissue extracts, and cell culture media from a (droplet) array for analysis or diagnostic purposes. In these cases, non-contact extraction of a portion of a sample (aliquot extraction) is essential to avoid contamination. Consequently, the portion of a sample transferred by the method according to the invention is used, for example, in quantitative or qualitative (bio)chemical analysis.For diagnostic purposes, the transferred portion of the sample can be used to diagnose diseases or in tests on body fluids. Screening procedures include, in particular, methods for identifying new drugs, identifying inhibitors, and identifying intermolecular interactions.

[0125] The present invention further relates to a device for the contactless transfer of a part of a sample, comprising an arrangement which includes the following components arranged one above the other in this order: a first electrode which is horizontally oriented, a microarray which has a surface with at least one region, a sample collector and a second electrode which is oriented parallel to the first electrode, with the proviso that there is a space between the microarray and the sample collector; and a voltage source which generates an electric field between the first electrode and the second electrode.

[0126] In a preferred embodiment, the at least one region is at least one hydrophilic region. In this case, the microarray has a surface with at least one hydrophilic region.

[0127] Optionally, the at least one hydrophilic region can be enclosed by a hydrophobic region. In this case, the microarray has a surface with at least one hydrophilic region enclosed by a hydrophobic region.

[0128] The descriptions relating to the method for the contactless transfer of a portion of a sample apply accordingly to the device for the contactless transfer of a portion of a sample. In particular, the descriptions of the arrangement provided in the method apply accordingly to the device.

[0129] The gap between the microarray and the sample collector is formed by a distance between the two. This gap enables contactless transfer, as the sample collector cannot touch the sample being applied to the microarray.

[0130] The height of the gap is not further restricted. The gap height can be reduced to generate a stronger electric field at the same voltage, or the same electric field strength at a lower voltage. To generate a sufficiently strong electric field, the gap height can be less than 1 cm. The height refers to the dimension of the space between the microarray and the sample collector. Therefore, the gap height corresponds to the distance between the microarray and the sample collector.

[0131] The height of the gap is preferably large enough to prevent the sample collector from coming into contact with any applied samples, and small enough to allow the transfer of a portion of the sample. To satisfy both conditions, the height of the gap is preferably 1 to 10 mm, more preferably 2 to 5 mm.

[0132] The space is filled with the gas surrounding the device; preferably, the space is filled with air.

[0133] The present invention further relates to the use of the device for transferring a part of a sample, comprising applying a sample to at least one region of the microarray or, if present, to at least one hydrophilic region of the microarray; and applying an electrical voltage between the first and the second electrode to generate an electric field between the first electrode and the second electrode.

[0134] The descriptions concerning the method for contactless transfer of a portion of a sample and the device for contactless transfer of a portion of a sample apply accordingly to the use of the device. In particular, the descriptions concerning the application of the sample to the microarray and the step of applying an electrical voltage between the first and second electrodes to generate an electric field between the first and second electrodes apply accordingly to its use.

[0135] The figures show: Figur 1 : Schematic side view of a (droplet) microarray with circular hydrophilic regions (a) without and (b) with samples. Figur 2 Schematic diagram of electric polarization. (a) shows the schematic atomic structure of a material without an electric field and (b) the structure with an applied field. The entire distribution of charges induced by the field is shown in (c). Figur 3 Electrostatic detachment: Separation and transfer of a portion of a sample under the influence of an electric field. Applying an electric field dielectrically polarizes the sample, causing negative charges to accumulate in the upper part of the sample near the anode. If the resulting electrostatic force is strong enough to overcome the surface tension, a portion of the sample detaches. Figur 4 Schematic view of a device for the contactless transfer of a portion of a sample from a microarray (top view on the left, side view on the right). The electric field is indicated by arrows. Figur 5 a) Images of the transfer process of an array of nine 8 µL drops of deionized water onto spots with a diameter of 2.8 mm, shown in side (top) and top (bottom) views before, during, and after the application of a 6 kV voltage for 50 seconds. The electrode spacing was 4 mm. b) Volume ranges of the transferred portions of nine samples containing 10 µL of an aqueous 1 M NaCl solution and of nine samples containing 8 µL of deionized water. The transfer was performed under identical conditions (i.e., under the conditions specified for a). Figur 6 A 4×4 pattern of 14 µL deionized water samples before application of the electric field (left). The same arrangement after applying an electrical voltage of 6 kV between the electrodes for a period of 0.9 seconds (right). The diameter of the circular hydrophilic areas is 2.8 mm. Figur 7 Transferred portions of samples were transferred from a 5×18 pattern of 8 µL deionized water samples placed on a microarray with circular hydrophilic regions measuring 2.8 mm in diameter by applying a voltage of 6 kV for 50 seconds. The first microarray containing the non-transferred portions of the samples has been removed from the lower figure to show only the transferred portions.

[0136] The present invention will be further explained below using examples, without, however, being limited to, such examples.

[0137] A device for the contactless transfer of a portion of a sample is shown schematically in Figur 4 The device comprises two circular electrodes spaced 3 to 5 mm apart. The lower electrode, i.e., the first electrode, is made of aluminum, and the upper electrode, i.e., the second electrode, is made of indium tin oxide (ITO). The sample collector is a circular glass disk 500 µm thick, coated with the second electrode in a 100 nm thick layer. The transparency of the second electrode allows for monitoring of the contactless transfer process. The first electrode is separated from the sample collector and the second electrode by a spacer to create a gap in which the microarray can be placed. The first and second electrodes are connected to a voltage generator capable of producing a voltage of up to 6 kV.The exemplary device provided can generate a strong electric field in the space between the first and second electrodes. Real-time monitoring of the contactless sample transfer process within the described exemplary device is possible using a camera mounted on the top.

[0138] The examples used microarrays, which are superhydrophobic glass plates with circular hydrophilic regions. These hydrophilic regions were created by photolithographic modification of nanoparticles on the glass surface. The microarrays used differ in diameter and the number of hydrophilic regions. The hydrophilic regions of a microarray have a diameter of either 1.4 mm or 2.8 mm.

[0139] To demonstrate the effectiveness of the method and apparatus for the contactless transfer of a portion of a sample according to the present invention for liquids with different conductivities and surface tensions, deionized water, a 1 M aqueous NaCl solution, and dimethyl sulfoxide (DMSO) were used as samples. After applying a voltage of 6 kV, contactless transfer of a portion of the sample onto the sample collector was achieved for samples consisting of 10 µL of an aqueous 1 M NaCl solution, samples consisting of 8 µL of deionized water, and samples consisting of 8 µL of DMSO. Unless otherwise specified, the voltage was applied for a period of 50 seconds.

[0140] The process of contactless transfer of a portion of the samples is in Figur 5 Shown in a side view and top view.

[0141] In the experiments, the microarray was loaded both fully and partially with samples ranging in volume from 800 nL to 15 µL. With both full and partial loading, it was possible to transfer a portion of the samples.

[0142] The transfer of a portion each from several samples of deionized water with a volume of 14 µL, arranged in a 4x4 pattern on a microarray with circular hydrophilic areas with a diameter of 2.8 mm, by applying a voltage of 6 kV, is described in Figur 6 The transferred parts of the sample are shown in the right-hand figure. Figur 6 Clearly recognizable. The volume of the transferred part of the sample is small compared to the volume of the original sample. To accurately calculate the transferred part of the sample, image processing was performed in conjunction with contact angle measurements, assuming that the surface of the transferred part of the sample is a spherical cap. To calculate the volume of the transferred part of the sample, its height was first measured using optical methods. Subsequently, the volume was calculated based on the shape (spherical cap) of the droplet formed from the transferred part of the sample, taking into account the contact area and the contact angle of the droplet. For the in the Figur 6 The mean volume of the transferred parts of the samples shown was calculated to be 35 nL.

[0143] Therefore, the inventive method transferred only a very small portion of the sample compared to the original sample volume. This, and the fact that the contactless transfer of a portion of the sample can be repeated several times in succession, demonstrates the excellent suitability of the method for contactless transfer of a portion of a sample according to the present invention for aliquot extraction in droplet microarrays.

[0144] As in Figur 7 As shown, by applying a voltage of 6 kV, a portion of a sample consisting of deionized water with a volume of 8 µL, arranged in a 5x18 pattern on a microarray with hydrophilic areas with a diameter of 2.8 mm, can be successfully transferred without contact. The lower figure of the Figur 7The microarray was removed to ensure better visibility of the transferred sample portions. In this example, the mean volume of the transferred sample portions was calculated to be 0.90 µL. While this mean volume is significantly larger than in the previous example, which used samples of deionized water with a volume of 14 µL, it is still considerably smaller compared to the volume of the original sample.

[0145] Further experiments demonstrated that if the volume of the transferred sample portions is not sufficiently small, the parameters of the process can be adjusted to further reduce their volume. For example, the volume of the transferred sample portions can be influenced by the size and shape of the hydrophilic regions, the contact angle of the sample on the microarray surface, the sample volume, the strength of the electric field, and the sample conductivity. Therefore, the volume of the transferred sample portion can be very flexibly controlled using the inventive method, and the method can be used to transfer sample portions of varying sizes.

Claims

1. A method for non-contact transfer of a portion of a sample, comprising the steps of: providing an arrangement comprising the following components arranged one above the other in this order: a first electrode oriented horizontally, a microarray having a surface with at least one region and carrying a sample on at least one region, a sample collector, and a second electrode oriented parallel to the first electrode, provided that neither the first electrode nor the sample collector touches the sample, and applying an electrical voltage between the first and second electrodes to generate an electric field between the two electrodes, thereby transferring a portion of the sample from the microarray to the sample collector.

2. A method for transferring a part of a sample without contact according to claim 1, wherein the at least one region is at least a hydrophilic region, wherein optionally the at least one hydrophilic region is enclosed by a hydrophobic region.

3. A method for transferring a part of a sample without contact according to claim 1 or 2, wherein the arrangement comprising the first electrode, the microarray, the sample collector and the second electrode is not moved in order to transfer the part of the sample to the sample collector.

4. Method for contactless transfer of a part of a sample according to any one of claims 1 to 3, wherein the generated electric field has a field strength of 800 kV / m to 2400 kV / m.

5. Method for contactless transfer of a part of a sample according to any one of claims 1 to 4, wherein the sample has a volume of 100 pL to 100 µL.

6. Method for contactless transfer of a part of a sample according to any one of claims 1 to 5, wherein the sample comprises a dielectric liquid or a conductive liquid.

7. Method for contactless transfer of a part of a sample according to any one of claims 1 to 6, wherein the transferred part of the sample is used for analysis, diagnostic purposes or in screening procedures.

8. Device for contactless transfer of a part of a sample, comprising an arrangement which includes the following components arranged one above the other in this order: a first electrode which is horizontally oriented, a microarray having a surface with at least one region, a sample collector and a second electrode which is oriented parallel to the first electrode, with the proviso that there is a space between the microarray and the sample collector; and a voltage source which generates an electric field between the first electrode and the second electrode.

9. Device for contactless transfer of a part of a sample according to claim 8, wherein the first and the second electrode are arranged at a distance of 0.5 to 20 mm from each other.

10. Device for contactless transfer of a part of a sample according to claim 8 or 9, wherein the at least one region is at least a hydrophilic region, wherein optionally the at least one hydrophilic region is enclosed by a hydrophobic region.

11. Device for contactless transfer of a part of a sample according to claim 10, wherein the at least one hydrophilic region is a superhydrophilic region and the hydrophobic region, if present, is optionally a superhydrophobic region.

12. Use of the device according to any one of claims 8 to 11 for transferring a part of a sample, comprising: applying a sample to at least one region of the microarray or, if present, to at least one hydrophilic region of the microarray; and applying an electrical voltage between the first and the second electrode to generate an electric field between the first electrode and the second electrode.

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