EP2623203A1 - Capillary dispenser - Google Patents

Abstract

The capillary dispenser has a piston cylinder unit (17) that includes a cylinder assembly (16) with inner cylinder (1-1), and a piston assembly (15) with hollow piston (5). The inner cylinder is connected with a capillary (8). The piston is moved in inner cylinder along the axis (A) between the upper and lower end positions of piston assembly. The piston is closed on one side, during the movement of piston to the lower end position of piston assembly.

Description

To equip a dispenser for dispensing minute volumes with capillaries, with which a liquid to be dispensed is received via the capillary effect, is known from the patent GB 23 686 40 B known. In order to dispense the liquid stored in the capillaries, an overpressure is generated at one end of the capillaries. This can be done individually or preferably on all capillaries together by being connected to a common pressure chamber.

A dispenser described here consists of a plurality of capillaries which are open on both sides, a compressed air supply, a valve for switching the compressed air, a pressure chamber consisting of an upper part with compressed air inlet and a lower part in which the capillaries are held. Upper and lower part of the pressure chamber are sealed against each other, so that when compressed air is applied to the pressure chamber, the compressed air is evenly distributed to the capillaries and the fluid located in the capillaries is ejected.

The main disadvantage of such a capillary dispenser is that the capillaries are emptied in parallel via a common pressure supply. In order to completely empty all capillaries, it is necessary to work with a high pressure, as already emptied capillaries act as a "short circuit" and the compressed air can escape through them with a relatively low resistance. Typical operating pressures are 15-25 psi and 1.0 - 1.7 bar, respectively.

The inflowing air leaves the capillaries at a speed of several meters per second and the expelled air volume can be a few milliliters, depending on the size of the pressure chamber, the applied pressure and the number of capillaries. This fact significantly limits the benefits of the technology.

A release of discrete drops on a "smooth" surface, such. B. a slide, is difficult or impossible, since the inflowing air divides the droplets and distributed over the surface. Therefore, only the delivery in wells (wells) of so-called microtiter plates comes into question. But here too there are restrictions; Thus, a release only in empty wells is possible, since it can come on the arrival of inflowing air in already filled with a liquid wells splash, resulting in a so-called crosstalk, also called crossover contamination, between the individual wells.

Such capillary dispensers are therefore designed purely for the delivery of liquid into empty wells. However, this does not completely solve the problem of cross contamination. The capillaries are never completely emptied immediately. When the liquid is ejected, a film of liquid remains on the inside of the capillary, which moves slowly towards the end of the capillary by gravity and inflowing air. Here it is dusted due to the high flow velocity of the air to form an aerosol. Also, this aerosol can be detected as cross-contamination, due to the high concentration of active substance contained or with sufficiently sensitive measuring systems.

In the field of liquid handling systems, so-called bubble wrap pipettes are known that can pick up and deliver liquid into and out of an associated pipette tip using a piston-cylinder unit.

The pipette tip is in this case attached to an opening in an end face of the inner cylinder. The piston is movably disposed within the inner cylinder on a common axis and sealed with respect to this. By raising or lowering the piston inside the inner cylinder, the free volume of the inner cylinder connected to the pipette tip is reduced or increased, whereby a liquid corresponding to the volume change can be picked up or dispensed via the pipette tip.

If, instead of a pipette tip, a capillary were to be attached, this would, since the free volume of the inner cylinder is relatively large relative to the volume of the capillary, be self-filled due to the capillary effect when immersed in a liquid. It would therefore not be necessary to raise the piston in the inner cylinder in order to take up liquid via the capillary.

The emptying of the capillary could, however, be carried out according to the principle of air displacement by decreasing the piston in the inner cylinder reduces the free cylinder volume and thus the air therein is pushed out through the capillary.

If a piston is provided for each capillary, the air displacement could be very finely dosed. This allows the training of a Drop at the free end of the capillary, which can be selectively discontinued by contact with, for example, a slide.

If the acceleration and the achievable speed of the piston are high enough, then contactless, i.e. a freely flying drop / liquid jet are discharged. The pressure required in this case for a single capillary is lower than for the common blowing out of all capillaries, since the pressure does not have to be oversized, as is necessary because of possible "short circuits", as explained in the description of the prior art.

The displaced by the piston free volume of the inner cylinder and thus the nachströmende from the capillary air was less than 50 ul in experiments and is thus by a factor of 20 to 200 less than with a capillary dispenser in which all capillaries are in communication with a pressure chamber.

This lower volume of air dispensed, with lower pressure and thus lower delivery rate allows both the dispensing on smooth surfaces and in vessels already containing a liquid, such as wells of a microtiter plate. An aerosol formation is thereby avoided as far as possible.

With the mentioned advantages, the use of piston-cylinder units, which are in each case associated with a capillary, seems to be formally suggested to the person skilled in the art. However, the disadvantages associated with having a capillary instead of a pipette lead him away from this idea.

After each delivery, the piston must be returned to its original position before re-dispensing, avoiding unwanted fluid intake.

It is the object of the invention to find a capillary dispenser having at least one piston-cylinder unit and in which an inadvertent uptake of liquid is safely avoided by design measures.

The capillary dispenser should advantageously be modifiable with only minor structural changes in order to optimize it either for a non-contact delivery in liquids or a delivery under contact of the capillary.

Advantageously, the capillaries should be quickly exchangeable at a high repetition rate. This object is achieved for a capillary dispenser with the features of claim 1. Advantageous embodiments are described in the subclaims.

• Fig. 1 a eine perspektivische Ansicht einer Baugruppe eines Kapillardispensers
• Fig. 1b eine Detailansicht der Baugruppe nach Fig. 1a
• Fig. 2 eine Schnittdarstellung der Baugruppe nach Fig. 1a
• Fig. 3a eine Kolben-Zylinder-Einheit 17 mit einer ersten Ausführung einer Kolbendichtung mittels einer Kolbendichtplatte 6 in einer oberen Endlage der Kolbenbaugruppe 15
• Fig. 3b die Kolben-Zylinder-Einheit gemäß Fig. 3a in einer unteren Endlage der Kolbenbaugruppe 15
• Fig. 4a ein Teil einer Kolben-Zylinder-Einheit 17 mit einer zweiten Ausführung einer Kolbendichtung mittels einer Kugel 12 in einer oberen Endlage der Kolbenbaugruppe 15
• Fig. 4b ein Teil einer Kolben-Zylinder-Einheit 17 mit einer zweiten Ausführung einer Kolbendichtung mittels einer Kugel 12 in einer unteren Endlage der Kolbenbaugruppe 15
• Fig. 5 eine Kolben-Zylinder-Einheit 17 mit einem Ventil 14

The invention will be explained in more detail with reference to exemplary embodiments with the aid of a drawing. Show:

• Fig. 1 a is a perspective view of an assembly of a capillary dispenser
• Fig. 1b a detailed view of the module after Fig. 1a
• Fig. 2 a sectional view of the module after Fig. 1a
• Fig. 3a a piston-cylinder unit 17 with a first embodiment of a piston seal by means of a piston sealing plate 6 in an upper end position of the piston assembly 15th
• Fig. 3b the piston-cylinder unit according to Fig. 3a in a lower end position of the piston assembly 15th
• Fig. 4a a part of a piston-cylinder unit 17 with a second embodiment of a piston seal by means of a ball 12 in an upper end position of the piston assembly 15th
• Fig. 4b a part of a piston-cylinder unit 17 with a second embodiment of a piston seal by means of a ball 12 in a lower end position of the piston assembly 15th
• Fig. 5 a piston-cylinder unit 17 with a valve 14th

In principle, a capillary dispenser according to the invention can be equipped with only one capillary, several capillaries in a row or several capillaries in a matrix. The capillaries can each be assigned to a piston-cylinder unit or a plurality of capillaries are connected to a common cylinder and thus associated with a common piston-cylinder unit 17.

Since a capillary dispenser is basically installed so that it dispenses in the direction of gravitational force, the following explanations are given as "above" or "below" clearly. They should also be understood as if a capillary dispenser is not operated in a vertical direction, for which there are applications especially for capillary dispensers with only one capillary.

If the structure and mode of operation of a capillary dispenser is described below on the basis of a piston-cylinder unit 17, then the statements apply to all the piston-cylinder units of the capillary dispenser.

In principle, a capillary dispenser according to the invention has at least one piston-cylinder unit 17, which consists of a cylinder assembly 16 with an inner cylinder 1.1 and a piston assembly 15, with a piston 5. The inner cylinder 1.1 and the piston 5 are arranged coaxially with one another on an axis A, wherein the piston 5 sealed relative to the inner cylinder 1.1, within this, along the axis A is movable by a stroke. The movement can in principle be initiated manually, but, in particular, if the capillary dispenser has a larger number of capillaries 8, motorized, including the capillary dispenser having a drive and a controller.

It is essential to the invention that the piston 5 is a hollow piston, which is opened at the beginning of its movement to the upper end position of the piston assembly 15 and then remains open on both sides over the length of the stroke.

During the movement towards a lower end position of the piston assembly 15, the piston 5 is closed at the beginning of one side and remains closed on one side over the entire length of the stroke. The lower and upper end positions of the piston assembly 15 limit the stroke. The inner cylinder 1.1 is pneumatically connected to at least one capillary 8.

Characterized in that the piston 5 is opened during its movement to the upper end position of the piston assembly 15 out and the piston-cylinder unit 17 thus represents an open system, the pressure conditions change at the associated with the inner cylinder 1.1 end of the at least one capillary 8, while the piston 5 is moved to the upper end position of the piston assembly 15 out. This movement thus has no influence on the voltage applied to the capillary 8 pressure conditions. That is, the capillary 8 could already be filled or at the same time, provided that it is in contact with a liquid with its other end (referred to below as the free end), it is filled exclusively via the capillary effect.

During the movement of the piston 5 to the lower end position of the piston assembly 15 out, it is closed and the piston-cylinder unit 17 thus constitutes a closed system. The air in the piston-cylinder unit 17 is compressed air, bringing the Pressure at the associated with the inner cylinder 1.1 end of at least one capillary 8 steadily increased, while the piston 5 is moved to the lower end position of the piston assembly 15 out. The air escapes via the at least one capillary 8, with which a liquid located therein is blown out.

Since the piston 5 must be opened after each emptying of the capillary 8 (venting), that is, the piston assembly 15 must be moved at least a small part of the stroke in the direction of the upper end position of the piston assembly 15, it is advantageous if the piston 5 and the Inner cylinder 1.1 are dimensioned over their length and their cross-section so that the stroke just enough for emptying the capillary 8. Thus, in each case with the emptying and venting of the full stroke is exhausted and the inner cylinder and the piston 1 1 can be dimensioned as small as possible.

It is clear to the person skilled in the art that the dimensioning can also be carried out in such a way that a stroke is sufficient to repeatedly empty the capillary 8. For bleeding and refilling the capillary 8, the piston assembly 15 is then raised only slightly in the direction of the upper end position of the piston assembly 15 so that the capillary 8 opens.

Since the pressure in the inner cylinder 1.1 does not rise abruptly and is also relatively low, the liquid can also be dispensed into a vessel in which there is already a liquid, without resulting in a so-called crosstalk, as described in the description of Prior art has been described. Pulse-like delivery is possible if a valve 14 is provided in the connection between the inner cylinder 1.1 and the capillary 8.

Basically, it is irrelevant for the operation of the piston-cylinder unit 17 where the piston 5 is closed. This can theoretically take place at the lower end guided in the inner cylinder 1.1, somewhere within or preferably at the upper end of the piston 5.

The closure preferably takes place by means of a piston seal. Either the piston 5 is formed directly with an end face formed on the upper end, the Vorteilhast is rounded, applied to the piston seal, or the seal is made indirectly by a provided around the end of the piston 5, sealed to the circumference of the piston head 5.1 to the piston seal is created. The latter has the advantage that on the dimensions of the piston head 5.1 a wider contact surface can be created. The piston seal may be preferred as a piston sealing plate 6, made of an elastic material, for. As an elastomer, executed. The sealing of all pistons 5 is then advantageously carried out with a same piston sealing plate 6. Instead, as a piston seal and individual cones or balls 12 are used. These cones or balls 12 may, for. As glass, ceramic or also preferably be made of an elastic material. By means of the piston head 5.1, the piston 5 is suspended in the piston assembly 15.

Hereinafter, some embodiments are described which differ by different structural embodiments of various components, such as head gasket, piston head 5.1, valve 14 and capillary 7. The different designs for the different components can be combined, even if not all of the possible combinations are explicitly mentioned here.

An advantageous embodiment which best meets the requirements for the precision and speed of dispensing of smallest volumes is a capillary dispenser with a multiplicity of capillaries 8 arranged in a matrix corresponding to the wells of commercially available microtiter plates, and one capillary per capillary 8 Cylinder unit 17 is present.

Such a capillary dispenser is intended in a first embodiment with reference to the Fig. 1-3 be explained.

The in Fig. 1a shown capillary dispenser with a matrix-like arrangement of capillaries 8, has a support plate 1, a pressure plate 2 and a piston retaining plate 3 and an adjacent to the support plate 1 indirectly via a sealing mat 10 magazine 9, in which the capillary 7 with the capillaries 8 hanging, non-positively the sealing mat 10 abut.

Per capillary 8, a piston-cylinder unit 17 is provided, which is arranged in each case on an axis A. In Fig. 1 For example, one of the axes A has been drawn. In order to have a view of the piston retaining plate 3, a piston-sealing plate covering this 6 and an overlying stop plate 4, which are also assigned to the piston-cylinder units 17, in Fig. 1a not shown.

The recesses shown in the support plate 1 are provided for - necessary for automatic operation assemblies, such as control assembly - engine and transmission. The support plate 1 at the same time forms the underside of a housing, not shown here.

Various embodiments of the piston-cylinder units 17 are shown as sectional views in the Fig. 2 to 5 to see.

A first embodiment of a piston-cylinder unit 17 is in the Fig. 3a and 3b shown, wherein the piston assembly 15 in 3a in an upper end position and in Fig. 3b is shown in a lower end position.

The piston-cylinder unit 17 essentially comprises an inner cylinder 1.1 and a concentric therewith arranged on a common axis A with the inner cylinder 1.1 piston 5. Also arranged on the axis A, is a capillary 8, the pneumatic with the inner cylinder 1.1 Connection stands. The piston 5 is a hollow piston open on both sides, which can be closed on one side.

The inner cylinder 1.1 of a piston-cylinder unit 17 is formed by a through hole in the support plate 1. As shown, it may be a stepped bore comprising a larger inner diameter portion in which the piston 5 travels and a smaller diameter portion to form a channel whose diameter is greater than the diameter of the capillary 8 but smaller the diameter of a capillary holder 7 formed on the top collar is 7.2. The length of the section in which the piston 5 is running, depending on the stroke and the axial play, which has the piston head 5.1 in a recess 3.1 of the piston plate 3, selected which determines in conjunction with the diameter of the piston 5, the maximum delivery volume. The smaller the grid is, in which the capillaries 8 are arranged, the smaller the diameter of the inner cylinder 1.1 must be necessarily dimensioned and therefore the greater must be the length of the section in which the piston 5 runs.

For sealing the piston 5 relative to the inner cylinder 1.1 is a piston 5 tightly enclosing sealing sleeve 11 is provided between the pressure plate 2 and the support plate 1.

The support plate 1 with the formed in a matrix-like arrangement inner cylinders 1.1, the pressure plate 2 with through holes in a same arrangement as the inner cylinder 1.1 and a corresponding number of sealing sleeves 11 together form an equal number of cylinder assemblies 16, as capillaries 8 are present.

The piston 5 of a piston-cylinder unit 17 is a hollow piston at the upper end of a piston head 5.1 is attached or formed. The piston head 5.1 encloses the upper end of the piston 5 as a cuff and has two perpendicular to the axis A extending end surfaces 5.1.1 and 5.1.2. On the lower face 5.1.1 of the piston head 5.1 can rest in a recess 3.1 of the piston retaining plate 3, which is deeper than the height of the piston head 5.1. Thus, the piston head has 5.1 in the direction of the axis A an axial clearance equal to the difference between the height of the piston head 5.1 and the depth of the recess 3.1. The upper end face 5.1.2 projects beyond the upper end of the piston 5, whereby it can be applied to the executed as a piston sealing plate 6 piston seal.

In principle, the upper end of the piston 5 can protrude beyond the upper end face 5.1.2, whereby the upper end of the piston 5 can be applied to the piston sealing plate 6.

How out Fig. 1a can be seen, the top of the piston retaining plate 3 a plurality of recesses 3.1 in a same matrix-like grid as the capillaries 8. The arranged in a row recesses 3.1 are connected via grooves 3.2 in conjunction, which together with the overlying, as a piston sealing plate. 6 formed piston seal form air ducts. Above the piston sealing plate 6, a stop plate 4 is arranged, which is fixed indirectly via the piston sealing plate 6 on the piston retaining plate 3 via detachable connections.

The piston retaining plate 3 and the stopper plate 4 are movable together along the axis A relative to the fixed support plate 1, whereby the piston 5 can be raised and lowered in the inner cylinder 1.1 according to the length of the stroke.

The piston retaining plate 3, the piston sealing plate 6, the stop plate 4 and the piston 5 with the respectively provided on it piston head 5.1 together form an equal number of piston assemblies 15, as capillaries 8 are present.

The capillary 8 assigned to a piston-cylinder unit 17 is pneumatically connected to the inner cylinder 1.1. In principle, any type of connection is possible here, which represents a connection sealing off from the environment.

In order to connect a matrix-like arrangement of capillaries 8 with a capillary dispenser, the capillaries 8 are introduced into the magazine 9 with the corresponding grid spacing and the magazine 9 is indirectly frictionally engaged on the carrier plate 1 via the sealing mat 10. In the following, the term magazine 9 is intended to stand for a plane plate, in which the capillaries 8 are arranged, regardless of how they are held in the plate and whether they are releasably or not releasably secured in the plate or held unattached.

In a less advantageous embodiment, the capillaries 8 z. B. be embedded in a magazine 9. The disadvantage here is that damaged, broken or clogged capillaries 8 can not be exchanged, which possibly makes the replacement of the entire magazine 9 required.

The capillaries 8 may instead individually in shafts, z. B. be taken from plastic and be releasably fixed in a magazine 9 via a provided on the shaft releasable screw, clamp or plug connection. The apparent advantage of the aforementioned solution is that the capillaries 8 are individually and easily replaced with shanks which are positively and / or non-positively connected to the magazine 9. The disadvantage is that such compounds can not be solved as often without wear and the tightening force to attach the Connection, may neither be too big nor too small, on the one hand not to damage the shaft and on the other hand to ensure a tight fit.

As an advantageous solution for grasping the capillaries 8, it is proposed to introduce these in each case into a capillary holder 7, which is designed like a pipette tip and into which Fig. 3a and 3b is shown. It consists of a tubular tip portion 7.1 and formed on this in the dispensing rear end tip collar 7.2 with a front and a rear, the tip portion 7.1 facing end face.

The capillary holders 7 can be inserted with their tip portion 7.1 in designated holes in a magazine 9 until the rear end of the top collar 7.2 comes to rest on the magazine 9 and the capillary holder 7 with a minimal radial play in the magazine 9 depends. To replace the capillary holders 7 and thus the capillaries 8, no connection must be solved, but the capillary holder 7 is pulled out only by a resistance-free lifting from the magazine 9, which is why the exchange to no mechanical stress on the capillary holder 7 and thus none by the exchange justified wear leads.

The capillary 8 is at the front end of the capillary holder 7, at least slightly protruding from this, attached. You can z. B. glued or pressed. The Kapillarhalterung 7 can be advantageously prepared as a monolithic injection molded part with the capillary 8 as an insert.

The magazine 9 can be positioned and fastened on the carrier plate 1 in such a way that the front end sides of the tip collars 7.2 are frictionally applied to the sealing mat 10.

dabei ist γ die Oberflächenspannung der Flüssigkeit, θ der Benetzungswinkel, p die Dichte der Flüssigkeit, g die Erdbeschleunigung und R der innere Radius der Kapillare 8.The capillaries 8 are preferably made of glass, but may also consist of other materials such as plastic or ceramic, wherein it must be ensured that the capillary rise height of the liquid to be dispensed sufficient to completely fill the capillary 8. The capillary rise height h can be calculated by the following formula: $$H=\frac{2\gamma \cos \mathrm{\Theta }}{\mathit{\rho gR}}$$

where γ is the surface tension of the liquid, θ the wetting angle, p the density of the liquid, g the gravitational acceleration and R the inner radius of the capillary 8.

The capillaries 8 preferably have a hydrophobic outer coating to prevent adhesion of the liquid when lifted out of the liquid as much as possible and to suppress the creeping of liquid on the outside of the capillary 8 in the formation of a drop at the capillary. Particularly advantageous is a coating of fluoropolymer.

Advantageously, the capillaries 8, and their free ends, as thin as possible to minimize the end face at the end of the capillary and thereby minimize the adhesion of liquid to the end face.

Hereinafter, the operation of a capillary dispenser according to the invention based on the function of a piston-cylinder unit 17, as shown in the Fig. 3a and 3b is shown, explained in cooperation with the illustrated capillary 8.

At the beginning of the Dispensiervorganges the piston assembly 15 is in an upper end position, as in Fig. 3a shown. The piston head 5.1 is located at the bottom of the recess 3.1 in the piston retaining plate 3. In the piston 5, whose lower end is in the inner cylinder 1.1, while the upper end is in communication with the atmosphere via the air ducts, the ambient pressure prevails in the inner cylinder 1.1.

Since the capillary 8 automatically fills by its capillary action on the immersion of its free end, as long as the other end is open and a substantially same ambient pressure is applied as at the free end, the capillary 8 may already be filled or now by immersion in a liquid be filled. For this purpose, a vessel filled with the liquid is preferably raised toward the capillaries 8.

For dispensing, a pressure must be built up in the inner cylinder 1.1, which presupposes that the inner cylinder 1.1 is closed and the free volume in it is subsequently reduced in order to expel the liquid from the capillary 8. The closing of the inner cylinder 1.1 takes place indirectly via the one-sided closing of the piston 5 by the piston assembly 15 is lowered. Like a way the axial play of the piston head 5.1, the piston head 5.1 is pressed indirectly via the piston sealing plate 6 to the stop plate 4 and closed. The piston-cylinder unit 17 is thus sealed from the environment and it is built on a further lowering of the piston assembly 15 and thus the piston 5, a pressure for dispensing the liquid from the capillaries 8 until it is sufficient to expel the liquid. See also Fig. 3b , A lower end position of the piston assembly 15 is given by the abutment of the piston retaining plate 3 on the pressure plate 2, but can also be defined by additionally existing stops.

After the complete dispensing of the liquid, the piston 5 is brought back into its upper end position by raising the piston assembly 15, with the piston 5 reopening so that the ambient pressure in the inner cylinder 1.1 is restored. In the process, or subsequently, liquid can be taken up again via the capillary 8, wherein the receptacle is not effected by suction, but exclusively by the capillary effect. The procedure described is synchronous for all piston-cylinder units 17 of the capillary dispenser.

In a second exemplary embodiment, the capillary dispenser should have an integer multiple of capillaries 8 than piston-cylinder units 17, as described in the first exemplary embodiment.

Here, a number of capillaries 8 are connected to each inner cylinder 1.1, which corresponds to the multiple of the piston-cylinder units 17. With increasing number of capillaries 8 to be emptied via a piston-cylinder unit 17, a larger pressure in the inner cylinder 1.1 must be established.

Instead of a piston sealing plate 6 as a piston seal for all piston-cylinder units 17, can also be per piston-cylinder unit 17 z. B. a ball 12 are used to seal the piston 5, which is inserted in an additional auxiliary plate 13 in a recess 13.1.

In the Fig. 4a and 4b a section of a piston assembly 15 is shown with a ball 12 as a piston seal in an upper and lower end position of the piston assembly 15.

Like the previously described embodiment, the piston head is 5.1 in the lower end position of the piston head assembly 15 in the recess 3.1 on the bottom and the piston 5 is open.

In the upper end position of the piston assembly 15, the upper end of the piston 5 is applied directly to the ball 12 and the piston 5 is closed. The ball 12 may be made of an elastomer or of glass, metal or ceramic with a high-precision surface. In the case of a non-elastic ball 12, the upper end of the piston 5 is made with an end face having a radius of curvature equal to the ball radius. The balls 12 are each placed above the individual pistons 5 in an auxiliary plate 13 in recesses 13.1 provided for this purpose. Also in this embodiment 3 grooves 3.2 are provided in the piston retaining plate. You can be introduced accordingly in the adjacent side of the auxiliary plate 13.

Another embodiment is based on Fig. 5 be explained.

For non-contact dispensing, as already explained in the description of the prior art, a high piston acceleration / speed is required in order to build up the pressure required for dispensing correspondingly quickly. This could be achieved by a large piston diameter. For this, however, the installation space, if only one capillary 8 is assigned to each inner cylinder 1.1, through the grid of capillaries 8, which on the grid of the wells of the target plates (96 plate = 9 mm, 384 plate = 4.5 mm, 1536 plate = 2.25 mm) is limited.

In order to manage without high accelerations / speeds, a valve 14 may be attached to the lower end of the inner cylinder 1.1. With the aid of the valve 14, it is possible in the inner cylinder 1.1 by means of the piston 5 to build up the required pressure for dispensing and then release it as a pressure pulse. For this purpose, miniature electromagnetic valves, but also passive ball check valves and so-called Durckbills or cross-slit valves made of an elastomer come into question. The problem with passive valves is that they typically do not release the pressure as a pulse but slowly open when a threshold is reached. In order to produce a pressure pulse with the passive valves, it is proposed to dimension the valve 14 so that it is still closed at a maximum pressure in the inner cylinder 1.1 and only mechanically opened by the application of the piston 5, so that the pressure abruptly can escape.

LIST OF REFERENCE NUMBERS

1

support plate

1.1

inner cylinder

2

platen

3

Piston retaining plate

3.1

recess

3.2

groove

4

stop plate

5

piston

5.1

piston head

5.1.1

lower end face of the piston head

5.1.2

upper end face of the piston head

6

Piston sealing plate

7

capillary holder

7.1

top part

7.2

lace top

8th

capillary

9

magazine

10

sealing mat

11

sealing sleeve

12

Bullet

13

auxiliary plate

13.1

deepening

14

Valve

15

piston assembly

16

cylinder assembly

17

Piston-cylinder unit

A

axis

Claims (9)

Capillary dispenser having at least one piston-cylinder unit (17), consisting of a cylinder assembly (16), with an inner cylinder (1.1) and a piston assembly (15), with a piston (5) arranged together on an axis (A) are, wherein the inner cylinder (1.1) at least with a capillary (8) is pneumatically in communication, wherein the piston (5) is designed as a hollow piston open on both sides and in the inner cylinder (1.1) along the axis (A) between an upper and a lower End position of the piston assembly (15) is movable and wherein the piston (5) is closed on one side to close the piston (5) during the movement to the lower end position of the piston assembly (15) on one side. Capillary dispenser according to claim 1, characterized
in that at least one piston assembly (15) includes a piston seal to which an upper end face of the piston (5) is frictionally engaged in the upper end position of the piston assembly (15), whereby the piston (5) is closed and the piston (5) within the piston assembly (15) has an axial play in the direction of the axis (A). Capillary dispenser according to claim 1, characterized
in that at least one piston assembly (15) includes a piston seal and on the piston (5) there is a piston head (5.1) protruding beyond an upper end face of the piston (5) and in the upper end position of the piston assembly (15) Piston seal is frictionally applied, whereby the piston (5) is closed and the piston (5) within the piston assembly (15) has an axial play in the direction of the axis (A). Capillary dispenser according to claim 2 or 3, characterized
that the piston seal is a ball (12) and the upper end face of the piston (5) is formed with a radius of curvature equal to the radius of the ball (12). Capillary dispenser according to claim 2 or 3, characterized
that the piston seal is a piston sealing plate (6). Capillary dispenser according to claim 1, characterized
that the inner cylinder (1.1) with the capillary (8) via a valve (14) is in communication. Capillary dispenser according to claim 1, characterized
in that at least one capillary (8) is fitted in a capillary holder (7) which has the shape of a pipette tip. Capillary dispenser according to claim 1, characterized
in that the capillary dispenser comprises a multiplicity of capillaries (8) and has per capillary (8) a capillary holder (7) in the form of a pipette tip into which the capillary (8), a free end projecting, is firmly inserted and the capillary holders (7 ) are arranged hanging in a magazine (9). Capillary dispenser according to claim 1, characterized
that each inner cylinder (1.1) with a plurality of capillaries (8) is in communication.

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