Pipette with a hydrophobic tip and method for producing same
The oxidative surface treatment and hydrophobic coating of pipette tips address adhesion issues, allowing precise dispensing of hydrophilic liquids in microfluidic systems by forming a hydrophobic outer layer while maintaining the inner surface hydrophilic.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2025-12-12
- Publication Date
- 2026-06-18
AI Technical Summary
Existing pipettes with hydrophilic surfaces struggle to effectively dispense hydrophilic liquids due to adhesion issues, particularly when used in microfluidic analysis systems, where hydrophilic reagents cling to the tip, making dispensing difficult or impossible.
A method involving oxidative surface treatment of pipette tips, followed by reaction with hydrophobic substances like perfluorinated organosilanes, forms a hydrophobic coating on the outer surface while keeping the inner surface hydrophilic, preventing hydrophilic liquids from adhering.
Enables reliable dispensing of small hydrophilic liquid volumes by preventing adhesion to the pipette tip, ensuring accurate and efficient reagent delivery in microfluidic systems.
Smart Images
Figure EP2025086772_18062026_PF_FP_ABST
Abstract
Description
[0001] R. 415708
[0002] - 1 -
[0003] Description
[0004] title
[0005] Pipettes with hydrophobic tips and methods for their manufacture
[0006] The present invention relates to a method for manufacturing a pipette with a hydrophobic tip. Furthermore, the present invention relates to a pipette with a hydrophobic tip, which can be manufactured in particular by means of the method.
[0007] State of the art
[0008] Microfluidic analysis systems, also known as lab-on-a-chip systems, can be used for the rapid processing of patient samples in medical diagnostics. These systems consist of a chamber containing an array with numerous cavities. Each cavity contains different reagents that can be reacted with the patient sample. The array is then flushed with a solution of the patient sample, which may have been pretreated. Such a microfluidic analysis system is described in EP 3 993 905 B1.
[0009] Pre-positioning the reagents in the cavities can be achieved by dispensing them using a glass pipette. For this purpose, the reagents are typically dissolved in water together with hydrophilic, water-soluble polymers, such as agarose and polyacrylamide, and then introduced into the cavities, for example, using a piezoelectric dispensing technique. After the water evaporates, the polymers immobilize the reagents within the cavities.
[0010] Disclosure of the invention R. 415708
[0011] - 2 -
[0012] The process for manufacturing a pipette with a hydrophobic tip comprises providing a pipette with a tip. A pipette is understood to be any device suitable for pipetting, which also includes, for example, capillaries. The tip is filled with a liquid. The tip undergoes an oxidative surface treatment. Subsequently, the tip is immersed in at least one substance that reacts with hydroxyl groups to form a hydrophobic solid. This substance is dissolved or dispersed in a hydrophobic solvent.
[0013] The pipette is preferably selected from a metal pipette, in particular a steel pipette, a ceramic pipette, or a glass pipette. A glass or ceramic pipette is particularly preferred.
[0014] An untreated glass or ceramic surface has hydroxyl groups on its surface and is therefore hydrophilic. When a glass or ceramic pipette is used to dispense a hydrophilic liquid, such as a hydrophilic solution used to pre-store reagents in the cavities of a microfluidic analyzer array, this liquid tends to cling to the tip of the glass or ceramic pipette, making dispensing difficult or impossible. By creating a coating of a hydrophobic solid on the outside of the tip, formed by the substance reacting with the OH groups on the glass or ceramic surface, the outside of the tip is hydrophobized, thus preventing the hydrophilic liquid from detaching from the tip.Filling the tip with a suitable liquid during the process prevents the solution or dispersion of the substance in the hydrophobic solvent from penetrating the tip and thus rendering its interior hydrophobic. Such a hydrophobic coating on the inside of the tip is undesirable, as it would prevent the tip from being filled with a hydrophilic liquid.
[0015] The oxidative surface treatment, particularly of a glass or ceramic pipette, is preferably carried out by immersing the tip in an aqueous solution of at least one oxidizing agent. The oxidizing agent has the R. 415708
[0016] - 3 -
[0017] The purpose is to oxidize any organic residues that may be present on the outer surface of the tip and to activate the glass or ceramic. An oxidizing agent is defined in particular as an oxidizing agent with a standard potential of at least +1.30 V at 298 K.
[0018] For example, chromic acid can be used as an oxidizing agent. However, the use of hydrogen peroxide is preferred, which is particularly advantageous when using a ceramic pipette. Hydrogen peroxide is especially preferably present in the aqueous solution in the presence of ammonia or sulfuric acid. This allows for particularly effective hydrophilization of the glass or ceramic surface for the subsequent reaction.
[0019] To remove residues of the oxidizing agent from the tip, it is preferred that, between immersion of the tip in the aqueous solution of the oxidizing agent and immersion of the tip in the solution or dispersion of the substance, the tip is immersed in water, particularly distilled water. In particular, immersion in a mixture of water and acetic acid is also permissible. After removal of the tip from the water, it is preferably blown dry with nitrogen.
[0020] When using a steel pipette, the oxidative surface treatment is preferably carried out by immersing the tip in an aqueous solution of at least one oxidizing agent, in particular nitric acid.
[0021] The substance that is to react with the OH groups of the surface to form a hydrophobic solid is preferably present in the solution or dispersion at a concentration of at least 0.05 wt% to ensure a sufficiently high reactivity of the substance towards the surface.
[0022] In a preferred embodiment of the process, the substance is a perfluorinated organosilane, which is particularly preferably selected from the group consisting of perfluorooctyltrichlorosilane, perfluorodecyltrichlorosilane, perfluorooctyltrimethoxysilane, perfluorodecyltrimethoxysilane, perfluorooctyltriethoxysilane, perfluorodecyltriethoxysilane, and mixtures thereof. Such perfluorinated organosilanes react with hydroxyl groups of R. 415708
[0023] - 4 -
[0024] The surface is coated with a Teflon-like hydrophobic layer by the functional silane groups (trichlorosilane, -methoxysilane, -ethoxysilane, dichlorosilane, -methoxysilane, -ethoxysilane) reacting with the OH groups of the surface to form corresponding silanols, thus binding to the surface. The reactivity of these functional silane groups is sufficient for a reliable coating of a previously hydrophilized surface. In this embodiment of the process, the hydrophobic solvent is a perfluorinated oil. Particularly preferred perfluorinated oils are bis(nonafluorobutyl)(trifluoromethyl)amine, perfluoroheptane, and / or perfluorotripentylamine.
[0025] In another preferred embodiment of the process, the substance is a non-fluorinated organosilane. This is particularly preferably selected from the group consisting of dichlorodimethylsilane, dimethoxydimethylsilane, diethoxydimethylsilane, methyltrimethoxysilane, methyltriethoxysilane, octyltrichlorosilane, decyltrichlorosilane, octyltrimethoxysilane, decyltrimethoxysilane, octyltriethoxysilane, decyltriethoxysilane, and mixtures thereof. The reaction of the functional silane groups of such a non-fluorinated organosilane with the hydroxyl groups of the previously hydrophilized surface results in strong bonds to the surface and a reliable coating with the hydrophobic solid. In this embodiment of the process, the hydrophobic solvent is a non-fluorinated oil, particularly preferably an alkane and / or a cycloalkane and / or an aromatic compound. Most preferably, it has at least six carbon atoms.
[0026] In yet another preferred embodiment of the process, the substance is a colloid. Particularly preferably, the colloid is a polysaccharide and / or a vinyl chloride-vinyl acetate copolymer and / or an unsaturated polyester resin, which frequently forms the basis of so-called "lacquers." The polysaccharide is most preferably selected from the group consisting of cellulose derivatives, cellulose acetate, and nitrocellulose. While in the first two preferred embodiments of the process the substance is dissolved in the oil, in this preferred embodiment it is dispersed in the oil. The oil can be a non-fluorinated or a perfluorinated oil. The [reference to R. 415708]
[0027] - 5 - The non-fluorinated oils and perfluorinated oils preferred in both previously described preferred embodiments of the process are also preferred in this preferred embodiment of the process.
[0028] To remove residues of the substance from the tip, after immersion of the tip in the solution or dispersion of the substance, it is preferably immersed in a hydrophobic solvent, which is particularly preferably identical to the hydrophobic solvent in which the substance was dissolved or dispersed in the previous process step. The tip can then be dried for subsequent use in dispensing hydrophilic liquids.
[0029] The liquid used to fill the pipette tip during the process is preferably hydrophilic. Water is particularly preferred. This choice of liquid is based on the understanding that preventing the inside of the tip from becoming hydrophobic is most important by preventing its contact with the substance. This is ensured by the immiscibility of the hydrophilic liquid with the hydrophobic solvent in which the substance is dissolved or dispersed. It is accepted that the liquid is miscible with the aqueous solution of the oxidizing agent, so that when the tip is immersed in the aqueous solution of the oxidizing agent, the oxidizing agent can diffuse into the tip.
[0030] A pipette, manufactured in particular by the method described above, has a hydrophobic solid on the outside of its tip. The thickness of this solid layer is in particular less than 1.0 pm.
[0031] The hydrophobic solid is preferably selected from the group of fluoroalkylsilanes or alkylsilanes, consisting of perfluoroalkyl chains or alkyl chains which are bound to the surface via silanols.
[0032] Preferably, the pipette is a pipette configured to dispense liquid volumes of less than 1.0 nl. It is particularly preferably configured to dispense liquid volumes in the range of 100 pl to R. 415708
[0033] - 6 -
[0034] To dispense 450 pl. When dispensing such small volumes of liquid, the adhesion of a hydrophilic liquid to the outside of the pipette tip can severely impede or even prevent the dispensing process, making the hydrophobic coating on the outside of the tip particularly advantageous.
[0035] Furthermore, it is preferred that the inner diameter of the tip at its opening is in the range of 60 pm to 90 pm. Such a narrow opening of the pipette tip would make the pipette particularly difficult to use for dispensing a hydrophilic liquid if a hydrophobic coating were to form on its inner surface; therefore, protecting the inside of the tip from hydrophobization by filling the tip with a liquid during the process is particularly advantageous.
[0036] Brief description of the drawings
[0037] Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description.
[0038] Figure 1 schematically shows the sequence of a method according to an embodiment of the invention.
[0039] Figure 2 shows a schematic cross-sectional view of a pipette according to an embodiment of the invention.
[0040] Exemplary embodiments of the invention
[0041] In an embodiment of the method according to the invention, shown in Figure 1, a glass pipette 20 is provided in a first step 11. This pipette has a tip 21 configured to dispense liquid volumes of 100 pl or more. The opening of the tip 21 has an inner diameter of, for example, 75 pm. The glass pipette 20 is filled with water 31. In a second process step 12, the tip 21 of the glass pipette 20 is immersed in an aqueous solution 32, which is obtained, for example, by dissolving 5 parts by volume of water with 1 part by volume of a solution 32.
[0042] - 7 -
[0043] A 25 wt% aqueous ammonia solution and 1 volume part of a 30 wt% aqueous hydrogen peroxide solution were mixed. The aqueous solution 32 has a temperature of, for example, 70 °C, and the immersion is carried out for a period of, for example, 10 minutes. The same steps can be carried out when using a ceramic pipette. If, however, the pipette 20 is a steel pipette, activation of the steel surface prior to silanization can be carried out by treatment with concentrated nitric acid.
[0044] In a third process step 13, the tip 21 is immersed in distilled water 33 to remove any remaining aqueous solution 32 from the outside of the tip 21. In a fourth process step 14, the tip 21 is removed from the water 33 and dried using a nitrogen stream. In a fifth process step 15, the tip 21 is immersed, for example, in a 0.1 wt% solution of perfluorooctyltrichlorosilane in bis(nonafluorobutyl)(trifluoromethyl)amine (Fluorinert FC-40 from 3M) 34. The tip 21 is left in the solution at room temperature for, for example, 3 minutes and then removed from the solution. In a sixth process step 16, it is immersed in bis(nonafluorobutyl)(trifluoromethyl)amine 35, which does not contain organosilane. After the tip has been removed from this as well, it is blown dry again with nitrogen in a seventh process step 17 and the water 31 is drained from the glass pipette 20.
[0045] Figure 2 shows the glass pipette 20 obtained in this way. On the outer surface 22 of the tip 21, a hydrophobic and chemically inert perfluorinated layer has formed due to activation of the glass surface by the action of hydrogen peroxide in alkaline solution and the subsequent reaction of the hydroxyl groups on the glass surface with the perfluorooctyltrichlorosilane. This hydrophobic solid 40 prevents hydrophilic liquids, such as aqueous solutions in particular, from adhering to the outer surface 22 of the tip 21. The inner surface 23 of the tip 21, on the other hand, was filled with water 31 during process steps 11 to 17 and therefore could not be made hydrophobic.
Claims
R. 415708 - 8 - Claims 1. Method for producing a pipette (20) with a hydrophobic tip (21), comprising the following steps: Providing (11) a pipette (20) with a tip (21) filled with a liquid (31), Oxidative surface treatment (12) of the tip (21), and Immersion (15) of the tip (21) in at least one substance which reacts with OH groups to form a hydrophobic solid (40) and which is dissolved or dispersed in a hydrophobic solvent (34).
2. Method according to claim 1, characterized in that the pipette (20) is a glass pipette or ceramic pipette.
3. Method according to claim 2, characterized in that the oxidative surface treatment is carried out by immersing the tip (21) in an aqueous solution (32) of hydrogen peroxide.
4. Method according to one of claims 1 to 3, characterized in that the concentration of the at least one substance in the hydrophobic solvent (34) is at least 0.05 wt.%.
5. Method according to any one of claims 1 to 4, characterized in that the hydrophobic solvent (34) is a perfluorinated oil and the substance is a perfluorinated organosilane.
6. Method according to any one of claims 1 to 4, characterized in that the hydrophobic solvent (34) is a non-fluorinated oil and the substance is a non-fluorinated organosilane. R. 415708 - 9 - 7. Method according to any one of claims 1 to 4, characterized in that the hydrophobic solvent (34) is a non-fluorinated or a perfluorinated oil and the substance is a colloid.
8. Method according to any one of claims 1 to 7, characterized in that the liquid (31) in the tip (21) of the pipette (20) is hydrophilic.
9. Pipette (20), characterized in that a hydrophobic solid (40) is arranged on an outer surface (22) of its tip (21).
10. Pipette (20) according to claim 9, characterized in that the hydrophobic solid comprises fluoroalkyl chains or alkyl chains which are bound to the surface via silanol groups.
11. Pipette (20) according to claim 9 or 10, characterized in that it is configured to dispense liquid volumes of less than 1.0 nl.
12. Pipette (20) according to one of claims 9 to 11, characterized in that an inner diameter of its tip (21) at its opening is in the range of 60 pm to 90 pm.
13. Pipette (20) according to one of claims 9 to 11, characterized in that it was manufactured by a method according to one of claims 1 to 8.