Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
  • B01L3/02—Burettes; Pipettes
  • B01L3/0275—Interchangeable or disposable dispensing tips

Definitions

• Pipettes or similar tools are often used for the defined absorption and distribution of liquids. With the help of pipettes, defined amounts of liquid can be taken from a storage container and transferred to a second container. In practice, an accurate and reproducible delivery of the amount of liquid is carried out via disposable pipette tips.
• the disadvantage of this method is that the pipette tip becomes contaminated when the pipette is immersed in the reaction volume. In processes that do not allow contamination, it is now necessary to change the pipette tip or to clean it using a complex procedure. These steps are very costly and time consuming. In practice, the trend today is to pipette a solution once taken up into several reaction volumes of the same consistency. This creation of so-called copies has the advantage that practically no contamination occurs.
• the disadvantage of this method is the complex handling of the reaction plates.
• Reaction wells (wells) is not a problem as the reaction volume is clear
• the pipetting volumes are getting smaller and smaller, since the actual reaction volume drops here to 10 ⁇ l.
• volumes of 10 nl to 1 ⁇ l are typically pipetted. Detaching a drop is only possible with these reaction plates still possible by immersing the pipette tip in the reaction volume. This leads to the contamination of the pipette tip or the reaction fluid already described
• DE 28 19 440 describes a method in which liquid is supplied from a storage container located above the dispensing nozzle via a hose line to the dispensing nozzle Drops created at the opening are torn off by a pressure gas pulse. This method can also be used to tear off a liquid drop from a pipette tip and offers the advantage that the smallest drops can be applied to a surface. Disadvantages of the method are the poor reproducibility of the drops and that liquid can also be pressed out of the depressions by the pressure pulse.
• DE 19 74 2005 describes a method with which volumes of less than 100 nL can also be pressed from a thin capillary.
• the volume pressed out here depends on the diameter of the capillary and the pressure pulse applied.
• the disadvantage of this method is on the one hand that complex printing technology and the poor reproducibility of the drop size.
• DE 197 42 005 describes a further development of this method.
• a method is also known in which the pressure is generated in a piezoelectric manner. The pressure tank is replaced by a piezo modulator mounted on the capillary.
• the advantage of this method is the improved reproducibility of the pulses and thus the drop size as well as the simple electrical control.
• the liquid to be pipetted is often to be introduced into already prepared solutions in the well of a well. Since both the well and the solution presented have a small volume, the use of pressure pulses for pipetting is associated with the risk that part of the reaction solution is printed out of the well.
• the precision of the pipetted volume, ie here the drop size, still largely depends on the tear off of the drop from the pipette tip or on the drop formation itself
• the object of the present invention was therefore to provide pipettes or pipette tips with which liquids can be taken up and distributed without residues. No liquid residues should remain on the pipette or pipette tip, which can either be carried on as contamination or reduce the volume to be pipetted.
• structured surfaces are liquid-repellent and self-cleaning. Such surfaces and processes for their production are disclosed, for example, in DE 19 80 3787 or DE 19 91 4007. Here it is described how drops drip off structured surfaces and thereby absorb dirt can
• structured surfaces the structures of which have a certain aspect ratio, that is to say a certain ratio between the high and mean width, improve the detachment or tearing off of liquid drops
• the present invention therefore relates to pipettes with structured surfaces, the surfaces of the pipettes coming into contact with a liquid having elevations with an average height of 50 nm to 10 ⁇ m and an average distance of 50 nm to 10 ⁇ m as well as surface energies of less than 19 mN / m
• the pipettes according to the invention can have completely structured surfaces or partially structured surfaces. It is important that the surfaces that come into contact with a liquid are completely or partially structured
• the surface energy of the structured areas which is determined on the unstructured material, is below 19 mN / m, preferably from 10 to 18 mN / m, in the pipettes according to the invention
• the structured surfaces used in the pipettes according to the invention are extremely hydrophobic and therefore highly water-repellent. They have a very high contact angle with water and promote the detachment or tearing off of liquid drops
• the contact angle or the surface energy is advantageously determined on smooth, unstructured surfaces.
• the material properties "hydrophobicity" is advantageously determined on smooth, unstructured surfaces.
• Liquid repellent or “liquid wetting” are also determined by the chemical composition of the uppermost molecular layers of the surface. A higher or lower contact angle or lower or higher surface energy of a material can therefore also be achieved by coating processes
• the hydrophobic properties of a surface can thus be defined via the surface energy, the contact angle on the smooth, ie unstructured material of various liquids being a measure of the surface energy, which is given in mN / m
• the average height of the elevation is preferably 50 nm to 4 ⁇ m with an average distance of 50 nm to 10 ⁇ m.
• the average height of the elevations 50 nm to 10 ⁇ m is one mean distance from 50 nm to 4 ⁇ m are particularly preferably the elevations have a height of 50 nm to 4 ⁇ m with an average distance from 50 nm to 4 ⁇ m
• the ratio of height to width of the surveys is of great importance, as already mentioned.
• the surveys can have aspect ratios from 0.5 to 20, preferably 1 to 10, particularly preferably 1 to 5
• the chemical composition of the top monolayer of the material is also important.
• radical sites are generated on the surface.
• the structured or unstructured material can be treated by means of plasma, UV or gamma radiation and special photoinitiators. After such an activation of the surface, ie generation of free radicals Additional monomers are polymerized on. Such a process generates a chemically particularly resistant coating.
• suitable monomers are acrylates, methacrylates and other vinyl derivatives, such as perfluorohexylethylene methacrylate
• the surface can be shaped or structured by stamping / rolling or at the same time during macroscopic shaping of the object, such as casting, injection molding or other shaping processes.
• the corresponding negative molds of the desired structure are required for this.
• An injection molding process is expediently used for the production of the pipettes according to the invention
• Negative molds for injection molding processes can be produced industrially, for example with the ligatechnology (R Wechsung in Mikroelektronik, 9, 1995, p 34 ff).
• First, one or more masks are produced by electron beam lithography with the dimensions of the desired elevations. These masks are used for exposure of a photoresist layer by X-ray depth lithography, whereby a positive shape is obtained.
• the gaps in the photoresist are then filled by electrodeposition of a metal.
• the metal structure obtained in this way represents a negative shape for the desired structure
• the elevations are arranged on a somewhat coarser superstructure.
• the elevations have the dimensions listed above and can be applied to an superstructure with an average height of 10 ⁇ m to 1 mm and an average distance of 10 ⁇ m to 1 mm
• the elevations of the superstructure can also be embossed, by means of lithographic processes or Shaping processes, such as casting or injection molding, can be applied
• the elevations and the superstructure can be applied simultaneously or in succession, ie first the superstructure, then the elevations, mechanically impressed, by means of lithographic processes or by shaping processing, such as casting or injection molding
• the shaping or structuring of the surfaces takes place in the case of surfaces with superstructure, as in the case of surfaces with elevations, expediently in one work step. Subsequent chemical modification of an already produced double-structured surface is of course also possible.
• Mechanical methods for introducing structures on unstructured surfaces or unstructured partial areas on structured surfaces are e.g. B embossing or stamping processes with prefabricated forms or stamping (needles).
• Pipette tips can also be structured over the entire pipette surface.
• the structuring, i.e. H. the elevations can be applied to the inner (a in FIG. 1) or the outer surface of the pipette (b in FIG. 2). It is also possible to have the elevations only on the pipette tip, i.e. H. onto the pipette outlet (c in Fig. 3).
• the materials used for the pipettes according to the invention must have the required values for the surface energy in the unstructured state. It can e.g. B. ö
• Perfluoroalkoxy compounds poly (ethylene), poly (propylene), poly (isobutene), poly (isoprene), poly (4-methyl-1-pentene), poly (vinyl alkanoates) and poly (vinyl methyl ether) as homo- or copolymer and other thermoplastic processable plastics are used
• the pipettes can be produced, for example, by an injection molding process in combination with a conventional injection molding tool manufactured by the LIGA process.
• the LIGA process is a structuring process that is based on basic processes of X-ray imaging, electroplating and molding. The process differs from micromechanics in this way that the structures are not created by an etching process in the base material, but can be molded inexpensively using a tool.In this case, the LIGA process is used to produce the tool.After the lithographic resist exposure (radiation-sensitive polymer) and development, the lacquer structure thus produced becomes a mold used for an electroplating process in which a metal alloy is deposited in the exposed spaces. Then the lacquer structure is removed and the remaining metal structure is used for the molding tool (G Gerlach, W Dotzel "Basics the micro system technology "Carl Hanser Verlag Kunststoff, 1997, page 60f)
• Pipette tips made of poly (propylene) with 0.5 to 10 ⁇ L pipetting volume were produced by injection molding, which had a microstructured surface at the outlet end with the aid of a tool described above (see FIG. 3).
• the distance between the elevations was 4 ⁇ m on average
• Pipettes made in this way can be used in automatic pipetting systems or dispensers

Landscapes

• Health & Medical Sciences (AREA)
• Clinical Laboratory Science (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Devices For Use In Laboratory Experiments (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Applications Claiming Priority (3)

Publications (1)

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Citations (1)

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• 1999
  • 1999-11-05 DE DE29919506U patent/DE29919506U1/de not_active Expired - Lifetime
• 2000
  • 2000-10-31 WO PCT/EP2000/010705 patent/WO2001032310A1/de not_active Application Discontinuation
  • 2000-10-31 JP JP2001534507A patent/JP2003523276A/ja active Pending
  • 2000-10-31 CA CA002389656A patent/CA2389656A1/en not_active Abandoned
  • 2000-10-31 EP EP00974490A patent/EP1225980A1/de not_active Withdrawn

Patent Citations (1)

Non-Patent Citations (1)

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