WO2002100558A1

WO2002100558A1 - Device for compound dispensing

Info

Publication number: WO2002100558A1
Application number: PCT/SE2002/001133
Authority: WO
Inventors: Thomas Laurell; Johan Nilsson
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-06-13
Filing date: 2002-06-13
Publication date: 2002-12-19
Anticipated expiration: 2003-12-13
Also published as: SE0102088D0

Abstract

The invention relates to a device for dispensing very small amounts of compound volumes of liquids. It comprises three layers (5, 1, 2) made e.g. of silicon, including an actuation layer (5), by which the ejecting membrane (14) of the device is provided, a first guiding layer (1) containing means for guiding the first liquid, and a second guiding layer (2) for guiding the second liquid. The ejecting membrane (14) is activated by a piezoelectric element (6). Between the ejecting membrane (5) and the first guiding layer (1) a first chamber (3) is formed. Between the first guiding layer (1) and the second guiding layer (2) a second chamber (4) is formed; said first chamber having an inlet (11) and an outlet (12), and a first nozzle/orifice (1), said nozzle/orifice being disposed in line with the piezoelectric element (6). The second chamber (4) are provided with an inlet (7) and an outlet (8) together with a second nozzle/orifice (2), disposed in line with the first nozzle/orifice and the piezoelectric element. The chambers (3, 4), the piezoelectric element (6) and the nozzle/orifices (1, 2) are disposed such that a liquid volume ejected from the first chamber (3), by means of power from the piezoelectric element (6), passes through the second nozzle/orifice (2) and becomes surrounded by a thin film of liquid from the second chamber (4), forming a free flying droplet just outside the second nozzle/orifice (2).

Description

DEVICE FOR COMPOUND DISPENSING

Field of the invention

The present invention relates to a device for compound dispensing, and more particularly to a device capable of delivering small, precise amounts of liquid, and at the same time surrounding or mixing these small amounts of liquid with another liquid. The device will bestow the amount of liquid (the droplet) a certain amount of kinetic energy, which enables the droplet to travel a distance through e.g. the air and impact on a surface or the like. The structure of the device comprises a number of layers in a suitable material, e.g. silicon. The dispensing function of the invention is general. Areas of contemplated application for the device include, e.g., to become part of analysis equipment in laboratory and chemical analysis, but also to become part of equipment for printing and reproduction.

State of the art

In the fields of laboratory and chemical analysis there is a continuous need for improving methods. Specific parameters targeted for improvement includes accuracy, speed, and cost and the amount of specimen needed to be able to carry out an analysis at all. The need for dispensing very small amounts of various liquids and solutions with high accuracy is apparent. In many applications there is also a need to protect the specimen against the physical and chemical influence of the medium surrounding the device which typically could be vacuum, air or another gaseous medium.

Various liquid dispensing apparatuses are known in the art. US 6,192,768 to Wallman et al discloses a flow-through sampling cell and use thereof, preferably manufactured in silicon and useful for continuous picovolume sampling in analytical flow. It comprises a flow channel and a sample emerging orifice in one wall of said channel and a pressure pulse generating means arranged at the opposite wall, by which pressure generating means a pressure pulse is generated. Said pulse forces a drop of liquid through the sample emerging orifice.

In U.S. 4,734,706 to Le is disclosed a film-protected print head for an ink jet printer or the like. A viscoelastic and ink-immiscible fluid is used to form a membrane over the ink orifice of a drop-on-demand, pressure pulse ink jet head. The droplets are ejected through the viscoelastic membrane. The membrane fluid does not add to the droplets.

In U.S. 4,196.437 to Hertz is disclosed a method and an apparatus for providing a compound liquid jet of fine droplets, particularly suitable for ink-jet recording systems. A primary stream of clean fluid is formed by ejecting under pressure a primary liquid from a nozzle and then causing the primary stream to traverse a thin layer of a secondary fluid that contain pigments, to form a compound liquid stream.

A problem liable to occur with known technology is that a crystal may form at the nozzle/orifice opening due to evaporation. It is also a problem that a piece of dust or a liquid deposit may adhere to the nozzle/orifice opening. It is also a problem that the primary and/or secondary liquid cannot easily be changed. Another problem is that the designs of the nozzles/orifices for the primary and secondary liquids are not optimised.

These problems will alter the surface tension forces affecting the droplet as it leaves the nozzle/orifice and thereby resulting in a misdirected droplet. In its most severe form this will stop the droplet completely.

Summary of the invention

Therefore, the invention provides a device for compound dispensing, and more particularly to a device capable of delivering very small precise amounts of liquid, and at the same time surrounding or mixing these small amounts of liquid with another liquid.

The device comprises a first chamber provided with a first nozzle/orifice and integrated ejection means for on-demand ejection of droplets, so called drop-on- demand.

In accordance with the invention, the device also comprises a second chamber covering the first nozzle/orifice, the second chamber having a second nozzle/orifice and being arranged for providing a volume of liquid from the first nozzle/orifice with additional liquid when passing through the second chamber and through the second nozzle/orifice.

Preferably said first and second chambers are both provided with an inlet and an outlet. The device is also preferably manufactured in a three layer structure including an actuation layer, by which an ejecting membrane of the device is provided, a first guiding layer containing means for guiding the first liquid, and a second guiding layer for guiding the second liquid.

Nozzle/orifices and chambers are arranged for providing a droplet of liquid from the first chamber with either a thin outer film of liquid, or a more substantial amount of liquid from the second chamber during said droplet's passage through said second chamber and nozzle/orifice.

The device could be manufactured in silicon and the ejection means could preferably comprise a piezoelectric element.

A device according to the invention will therefore provide the following features and advantages over previously known art: - Sampling of flows in both the first and second chamber, and any additional chambers according to the invention are provided for by means of the flow-through arrangement with inlet and outlet to each chamber.

Problems with crystal forming and particle deposits on the outermost nozzle/orifice front side giving rise to misdirected droplets are avoided by providing the outermost chamber with a suitable fluid preferably without particles or crystal- forming components.

Problems with crystal forming and particle deposits on the inner nozzle/orifice giving rise to misdirected droplets are avoided by providing the outermost chamber with a suitable fluid that do not stimulate or generate crystal or deposit growth.

Satellite droplets that may form will not cause unwanted contamination because the fluid in the outermost chamber is chosen to be of a non-contamination nature.

Multiple fluid layers can be arranged to a droplet by providing a device with multiple fluid chambers according to the invention, creating a "multiple compound dispensing" device.

The flow-through design enables a continuous flow of the clean liquid in the secondary chamber which will circumvent cross-contamination from previously ejected liquids.

The invention is defined in the accompanying claim 1, while preferred embodiments are set forth in the dependent claims.

Brief description of the drawings The invention will be described below with reference to the accompanying drawings, in which: figure 1 is a side view of an embodiment of the present invention; figure 2 is an alternative embodiment of the nozzle/orifice in fig.1 ; figure 3 is a top view of the embodiment in fig. 1; figure 4 is a detail view pertaining to conduit and nozzle/orifice dimensions; figure 5 shows a problem with misdirected droplets in prior art; figure 6 shows the forming of a compound droplet just outside the second nozzle/orifice; and figure 7 shows detail of distance between first and second orifice.

Detailed^' description of preferred embodiments

The invention will solve the need for dispensing very small amounts of various liquids and solutions with high accuracy and at the same time protecting the specimen against the physical and chemical influence of the medium surrounding the device which typically would be vacuum, air or another gaseous medium.

The invention will also solve the problem that a crystal of salt easily may form at the nozzle/orifice opening due to evaporation. It will also solve the problem that a piece of dust may adhere to the nozzle/orifice opening. Both these problems would otherwise alter the surface tension forces affecting the droplet as it leaves the nozzle/orifice and cause a misdirected droplet, confer fig. 5.

The device comprises three layers made e.g. of silicon, including an actuation layer 5, by which the ejecting membrane 14, including a pushbar 13, of the device is provided, a first guiding layer 1 containing means for guiding the first liquid, and a second guiding layer 2 for guiding the second liquid. The pushbar 13 of the ejecting membrane 5 is activated by a piezoelectric element 6. Between the ejecting membrane 5 and the first guiding layer 1 a first chamber 3 is formed. Between the first guiding layer 1 and the second guiding layer 2 a second chamber 4 is formed. Said first chamber is provided with an inlet (11) and an outlet (12), and a first conduit 101 ending in a first nozzle/orifice 16, said nozzle/orifice being disposed in line with the piezoelectric element 6. The second chamber 4 is provided with an inlet 7 and an outlet 8 and a second conduit 102 ending in a second nozzle/orifice 18 disposed in line with the first nozzle/orifice and the piezoelectric element. The chambers 3, 4, the piezoelectric element 6 and the nozzle/orifices 16, 1 8 are disposed such that a first volume of liquid ejected from the first chamber 3, by means of power from the piezoelectric element 6 passes through the second nozzle/orifice 18 and becomes surrounded by a thin liquid film of liquid from the second chamber 4. It is also possible to instead of a thin liquid film, a more substantial amount of liquid from the second chamber is added to or mixed with the first volume of liquid.

Figure 2 shows an alternative shape 21 of the nozzles/orifices 18 and 16 from fig. 1 , where the edges of the substrate near the nozzle/orifice are level with the rest of the substrate. Figure 4 shows a conduit with a conical shape having an inner opening 41, an outer opening 42 and a channel length 43, a protruding distance 44, a flat zone width 46, a taper angle 47, and an obtuse inner angle 45. The area of the inner opening is normally equal or lesser than the area of the outer opening. The conduit could be rectangular, square or circular in cross section. At least some part, preferably the main part of the channel length 43 of said conduit, is arranged to be conical.

In preferred embodiments the first nozzle/orifice is of the type shown in fig. 1, i.e. 16, and the second nozzle/orifice is of the type shown in figure 2, i.e. 21. It is also possible to have it another way around, or to use nozzles/orifices of intermediate shape. Alternatively, all orifices are of the type shown in fig. 4 with different values on the parameters inner opening area, outer opening area, channel length 43, pro- trading distance 44, flat zone width 46, taper angle 47 and o inner angle 45. A value of the protruding distance 44 equalling zero will create a case similar to the one described in figure 2. Due to limitations imposed by crystal structure and etch techniques, only certain values on these angles are achievable. For example, with a preferred technique, both the inner angle 45 and the taper angle 47 are given a value of 35,3°.

Figure 3 shows an embodiment of the invention from above. The pushbar 13 is shown in the middle, underlying orifices/nozzles are not shown for the sake of clarity.

One of the features of the invention is the concept of arranging a thin liquid surface in front of an ejecting nozzle/orifice, and in direct contact with said nozzle/orifice. If, for best performance, different characteristics are needed by a liquid to be ejected, this invention offers the possibility to combine characteristics from two separate liquids, by bringing the liquids together at the time of ejection. If, for example, it is needed for a droplet to both contain a high concentration of salt, but also to add a minimum of salt crystal to nozzle/orifice edges, a solution could be to actively surround a first high saline concentration liquid with a second low saline concentration or non saline containing liquid, at the time of ejection, through the above described arrangements. The gas/liquid interface is defined by the low/none saline liquid at the outer chamber 2.

By using inlets and outlets in addition to nozzle/orifices, the advantage is won, being able to flush the chambers with e.g. an inert cleaning fluid, without having to following or preceding another liquid in a sequence, will contaminate that other liquid, are diminished.

A continuous minor flow applied in one or more of the chambers by means of draining a small continuous flow of fluid from the respective outlet will further help to remove contamination particles or other contaminants. Such a continuous flow would also further reduce the risk of clogging.

The compound dispensing device according to the present invention can be manufactured as a three-layer structure. The layers could be manufactured in ceramics. The layers may also be manufactured in silicon. It is also possible to form the layers in plastic materials, for instance by using a silicon or metal matrix. Many plastics have good chemical properties. The silicon layer structure can be produced by means of well-known technologies. Channels and cavities can be produced by means of anisotropic etching. The silicon layer may be protected against etching by an oxide layer, that is by forming an Si0₂ layer. Patterns may be arranged in the Si0₂ layer by means of lithographic technologies. Also, etching may be selectively stopped by doping the silicon and using pn etch stop or other etch stop techniques. Since all these process steps are well known in the art they are not described in detail here.

The device includes means for providing the mechanical force and power to the membrane of the device. The technological method of said means used in preferred embodiments of the invention could be chosen from among the group of electro- static, electromagnetic, magnetostrictive, hydraulic, pneumatic, electromechanical, mechanical, combustion, gas pressure, heat engine and piezoelectric principles.

The device is preferably provided with a piezoelectric element providing the mechanical force and power to the membrane of the device. The ejecting membrane is thus activated by the piezoelectric element. The piezoelectric element is attached to a backing or yoke (not shown) to hold the element and take up the reaction forces. The piezoelectric element is preferably of the so called multi-layer type in order to generate a contraction/expansion as large as possible of the element. A bimorph piezoceramic element may also be used. The element may be attached to the membrane via a spacer, e.g. made of acrylic resin (Plexiglas) in order to concentrate the lift force of the piezoelectric element to a narrow area.

In a preferred embodiment the membrane distance between the pushbar 13 and the edge of the membrane 14 is approximately 300 μm. The thickness of the membrane 14 is 7 μm. The distance between edges 31 and 32 is 3 mm, and the thickness of actuation layer at non-etched portions is approximately 300 μm. A distance d between the first orifice and second orifice as shown in figure 7 can be 100-150 μm.

The function of the device may be understood with reference to figure 1. The ejection sequence includes actuating the piezoelectric element 6 with a voltage of preferably 10-50V. When the piezoelectric element is actuated with such a voltage, the element expands, decreasing the volume of the first chamber 3. Due to the shape of the chamber 3 and the first nozzle/orifice 1 , a volume of liquid is formed and ejected through the second chamber 4 and the second nozzle/orifice 2. Due to surface tension forces a droplet will form from said volume just outside the second nozzle/orifice, see fig. 6.

A feature of the device is that the droplet size and ejection moment and frequency can be dynamically varied by controlling the electrical parameters of the energising voltage to the piezoelectric element and some other parameters. Among mentioned parameters are the stroke, i.e. displacement of the piezoelectric element, which is controlled by the amplitude of the energising voltage, and the frequency of pulses in the energising voltage actuating the piezoelectric element. One pulse of these actuating signals can be called an actuation pulse. The rising slope or edge of the actuation pulse has great influence on size and speed of the delivered droplet. In preferred embodiments, means for generating actuation pulses with different rise times and amplitudes are provided.

It will be appreciated by persons skilled in the art that the structure of the compound dispensing device according to the present invention has several advantages over the prior art. These advantages include solving of the problems that a crystal of salt or a liquid deposit easily may form at the nozzle/orifice opening due to evaporation, surface tension or related effects, and also solving of the problem that a piece of dust may adhere to the nozzle/orifice opening. A person skilled in the art may produce the device of the invention using standard technologies. It will be appreciated that manufacturing steps may be performed in various ways and various orders without departing from the invention. The scope of the invention is only limited by the claims below.

Claims

1. A device for dispensing precise volumes of compound liquids, provided with a first chamber (3) provided with a first orifice (16) and integrated ejection means (5, 6), characterised by a second chamber (4) covering the first orifice (16), the second chamber (4) having a second orifice (18) and arranged for providing a volume of liquid from the first orifice (16), with additional liquid when passing through the second chamber (4) and through the second orifice (18).

2. A device according to claim 1, characterised in that said first chamber is provided with an inlet (11) and an outlet (12)

3. A device according to claim 1 or 2, characterised in that the second chamber (4) is provided with an inlet (7) and an outlet (8)

4. A device according to claim 1, characterised in that the first orifice (16) and the second orifice (18) are placed in line with each other.

5. A device according to any of the claims 1 - 4, characterised by a three layer structure including an actuation layer (5), by which a pushbar (13) and an ejecting membrane (14) of the device is provided, a first guiding layer (1 ) containing means for guiding the first liquid, and a second guiding layer (2) for guiding the second liquid.

6. A device according to any of the claims 1 - 5, characterised in that orifices (16, 18), and chambers (3, 4) are dimensioned for providing a droplet of liquid from the first chamber (3) with a thin outer film of liquid from the second chamber (4) during said droplet' s passage through said second chamber (4) and orifice (18)

7. A device according to any of the claims 1 - 5, characterised in that orifices (16, 18), and chambers (3, 4) are dimensioned for adding to a droplet of liquid from the first chamber^'(3) a substantial amount of liquid from the second chamber (4) during said droplet's passage through said second chamber (4) and orifice (2).

8. A device according to any of the claims 1 - 7, characterised in that it is manufactured in silicon.

9. A device according to any of the claims 1 - 7, characterised in that it is manufactured in plastic, metal or ceramics.

10. A device according to any of the claims 1 - 9. characterised in that the ejecting means (5, 6) can be controlled to eject a droplet at a certain point in time (drop- on-demand).

11. A device according to any of the claims 1 - 10, characterised in that the ejecting means (5, 6) comprises a piezoelectric element (6).

12. A device according to claim 10, characterised in that it provides means (19) for generating electrical actuation pulses with various launching times, rise times, amplitudes and frequencies.

13. A device according to any of the claims 1 - 10, characterised in that the ejecting means (5, 6) is actuated by electrostatic, electromagnetic, magnetostrictive, hydraulic, or pneumatic principles.

14. A device according to any of the preceding claims 1 - 13, characterised in that one or both of the orifices (16, 18) have a protruding length (44) of zero, providing a flush surface.

15. A device according to any of the preceding claims 1 - 14, characterised in that it is provided with conduits (101, 102) at one or both of the orifices (16, 18) and that said conduits have a conical shape in at least some part of their extent.

16. A device according to claim 15 , characterised in that the conduits (101, 102) at one or both of the orifices (16, 18) have a circular conical shape in at least some part of their extent.

17. A device according to claim 15, characterised in that the conduits (101, 102) at one or both of the orifices (16, 18) have a rectangular conical shape in at least some part of their extent.

18. A device according to claim 15, characterised in that the conduits (101, 102) at one or both of the orifices (16, 18) have a square conical shape in at least some part of their extent.

19. A device according to any of the preceding claims, characterised in that one or both of the orifices (16, 18) have a protruding length (44) greater than zero, and an inner angle (45) between 0 and 90 degrees.

20. A device according to claim 15, characterised in that the conduits (101, 102) have a taper angle(47jthat is between 0° and 80°.

21. A device according to claim 20, characterised in that the taper angle (4 Ij is approximate ly 35.3 ° .

22. A device according to any of the preceding claims, characterised in that a distance (d) between inner (16) and outer (18) orifices are 0 μm, i.e. said orifices are in the same plane, or more.

23. A device according to any of the preceding claims, characterised in that the distance (d) between inner (16) and outer (18) orifices are between 1O0 and 150 μm.

24. A device according to any of the preceding claims, characterised in that it is provided with further chambers with orifices as mentioned in claim 1 , i.e. a third, a forth, a fifth chamber or more.

25. A device according to claim 24 characterised in that the third chamber, and any further chambers is provided with an inlet and an outlet

26. A device according to claim 24 or 25, characterised in that the first orifice (16) and the second orifice (18) and any further orifices are placed in line with each other.