GB2451135A

GB2451135A - Analyser and pump

Info

Publication number: GB2451135A
Application number: GB0714214A
Authority: GB
Inventors: Lee Bulbrook
Original assignee: EQUINE HEALTHCARE Ltd
Current assignee: EQUINE HEALTHCARE Ltd
Priority date: 2007-07-20
Filing date: 2007-07-20
Publication date: 2009-01-21
Also published as: WO2009013447A1; GB0714214D0

Abstract

A pumping system comprising a chamber 2 with a deformable liquid-impermeable membrane 5 within the chamber thereby defining two compartments 7, 8 and means 9, 9a to pump a liquid into and out of one of said compartments, thereby causing a change in pressure in said other compartment. The system may comprise two chambers in a two part chamber assembly 11 and between which liquid is transferred by two one way piezoelectric pumps arranged in opposite senses. The membrane may be inelastic and a portion of the chamber may be transparent or translucent to allow fluid visualization. Also disclosed is a liquid analyser (Fig. 4) utilizing the pumping system for drawing a drop of liquid e.g. breath condensate into a sensing chamber.

Description

ANALYSER AND PUMP

Field of the Invention

The invention relates to analysers for analysing components in liquids, and pumping systems suitable for operating such analysers.

Background and Prior Art Known to the Applicant

As sensing elements become ever more small and sophisticated in their abilities to detect :. the presence of analytes in fluids, there are increasing opportunities for the development of portable analysis systems for determining the properties of liquids "in the field". One S...

such example might be the detection of hydrogen peroxide in breath condensate as an .,. 25 indicator of lung disease. Solid state sensing elements are available for the detection of * analytes such as hydrogen peroxide and often operate in a mode whereby the liquid to be analysed must be passed across the surface of a sensor. Such is the characteristics of these sensors that the flow rate needs to be maintained at a relatively constant level in * order to produce a consistent reading. The flow is required because sensors often consume the analyte of interest as part of the detection method, and so the sample must be continually replenished. The constancy of flow is required to prevent interference to the very small electrical signals (often as low as nanoAmpere) that are produced by the sensing elements.

Furthermore, it is often required to make these analysers not only portable, but small enough to be hand-held. As a result, low power-consumption systems are required for any fluid transport needs within the analyser.

Another problem that is also encountered is that the fluids to be analysed often have entrained gases within them, or air locks may be formed within the internal pipework within the analyser, and so any pumping system used within such an analyser needs to be able to cope with pumping a mixture of gas and liquid, and in some instances, suspended solids.

It is amongst the objects of the present invention to attempt to provide a solution to these and other problems.

Summary of the Invention

Accordingly, the invention provides a pumping system comprising: a chamber, comprising at least two ports; and a deformable liquid-impermeable membrane, within said chamber, located between two of said ports; thereby defining two compartments; and :. pumping means to pump, in use, a liquid into or out of one of said compartments, thereby :..::: causing a change in pressure in said other compartment. By using a deformable membrane, the membrane does not have to slide within a chamber, and so frictional losses :.., 25 can be reduced, so allowing lower flow rates to be achieved. Preferably, the membrane is substantially inelastic. In this way, no additional force is required to cause the elastic deformation, and again, lower and more stable flow rates can be achieved.

* Preferably, the pumping system comprises a second such chamber and membrane assembly, and wherein the pumping means is configured to transfer, in use, liquid between a first compartment of the first such chamber to a first compartment of the second such chamber; thereby causing an increase in pressure in the second compartment of one chamber and a corresponding decrease in pressure on the second compartment of the other chamber.

In any aspect of the invention it is particularly preferred that said pumping means comprises a piezoelectric pump.

When two chambers are used it is particularly preferred that said pumping means comprises two piezoelectric pumps, one such pump configured to pump, in use, liquid from a first compartment of the first chamber to a first compartment of the second chamber; and the second such pump configured to pump, in use, liquid from a first compartment of the second chamber to a first compartment of the first chamber.

In any aspect of the invention it is preferred that at least a portion of said chamber is translucent or transparent, thereby allowing visualisation, in use, of liquid entering or leaving a compartment.

Included within the scope of the invention is a pumping system substantially as described herein, with reference to and as illustrated by any appropriate combination of the accompanying drawings.

Also included within the scope of the invention is a liquid analyser comprising: a liquid- :. receiving portion; a sensing element, in fluid communication with said liquid-receiving portion; liquid transfer means to draw, in use, liquid from said liquid-receiving portion S...

and into contact with said sensing element; wherein said liquid transfer means comprises a pumping system described herein.

S

Preferably, said liquid-receiving portion comprises an indentation having a hole located towards the base of said indentation; and more preferably, said indentation has a * hydrophobic surface.

Also included within the scope of the invention is a liquid analyser substantially as described herein, with reference to and as illustrated by any appropriate combination of the accompanying drawings.

Brief Description of the Drawings

The invention will be described with reference to the accompanying drawings in which: Figure 1 is a schematic illustration of a single-chamber embodiment of a pumping system of the present invention; Figure 2 is a schematic illustration of a dual chamber embodiment of a pumping system; Figure 3 is a cross-sectional and schematic illustration of a pumping system of the present invention; and Figures 4A -4C are cross-sectional illustrations of a portion of a fluid analyser according to the present invention, in use.

Description of the Preferred Embodiments S. * .

Figure 1 illustrates, in schematic view, a pumping system according to the present Sb..

invention, generally indicated by 1. The system comprises a chamber 2 having a first port 3 and a second port 4. Located within the chamber 2 is a liquid impermeable membrane 5 sealed to the inside surface of the chamber 2 by means of a seal 6. The membrane 5 thereby defines two compartments 7, 8 within the chamber 2. Also provided within the system is a pump 9 to transport, in use, a liquid into the first compartment 7. In this * embodiment, the membrane 5 and its seal 6 are slideable within the cavity of the chamber 2 thus allowing the relative volumes of the two compartments 7, 8 to be adjusted by pumping liquid into and out of the first compartment 7.

In use, as liquid is pumped into the first compartment 7 by the pump 9, the membrane 5 and its seal 6 slides along the interior of the cavity 2 so that the volume of compartment 8 decreases as the volume of compartment 7 increases. In this way, by appropriate control of the pump 9, fluid in communication with the port 4 may be drawn towards the second compartment 8, or conversely expelled away from the compartment 8.

By means of this configuration, it is possible to use a pump 9 that it only capable of pumping liquids whereas the entire pumping system I is capable of moving both liquids and gases (and also small suspended solids) due to the action of the moving membrane 5.

If such a "liquid only" pump is to be employed, then when setting up the system, the first compartment 7 and the associated pipework leading through the port 3, into the pump 9 and on to a fluid reservoir (not illustrated) will be filled completely with liquid before use.

A further advantage of the system, as well as not requiring priming to pump either liquids or gases, is that the fluid to be pumped is isolated by the membrane'5 from the pump itself.

Figure 2 illustrates, again in schematic view, an alternative embodiment of the invention having a second such chamber 2A containing a membrane 5A and a seal 6A, again defining two compartments 7A and 8A. The first chamber 2 has an additional port 10 communicating with its first compartment 7 and connected to a second pump 9A entering the first compartment 7A of the second chamber 2A through its port 3A. The second chamber 2A also has an additional port IOA in communication with its first compartment 7A, and connected to the port 3 of the first chamber 2 through the pump 9. *. I..

*. In use, the two compartments 7 and 7A and the pipes and pumps 9, 9A connecting the compartments are filled with liquid. In this way, it is possible to use unidirectional pumps :**., to enable the system as a whole to pump in either direction. In a first mode of operation, * ° operating the pump 9A whilst pump 9 is switched off (and effectively operating substantially as a seal, i.e. at least to the extent that the seal is sufficient to resist pressure generated within a first chamber 7A causing any appreciable liquid flow through pump 9 and into chamber 7), will cause liquid to be drawn from compartment 7 into compartment 7A, thereby causing a suction in compartment 8 of the first chamber 2 drawing liquid or gas into or towards port 4, as illustrated in figure 2. in the second mode of operation, pump 9 may be switched on whilst pump 9A is switched off, and effectively acting substantially as a seal (as described above, mutatis mutandis); in this mode, liquid will be drawn from the compartment 7A of the second chamber 2A and into the compartment 7 of the first chamber 2. In this mode of operation, compartment 8 will increase in volume, thereby expelling any fluid that is in fluid communication with its port 4.

in either mode of operation, it will be noted that a corresponding opposite flow will be produced at the port 4A relative to that in the first port 4.

Figure 3 illustrates an alternative embodiment of a pumping system of the present invention. Illustrated is a chamber assembly II (illustrated in cross-section) and pumps 9 and 9A and associated pipework, in schematic view. The chamber assembly 11 is of two-part construction (1 IA and I1B) each part having corresponding pairs of indentations which, when mated together, define two chambers 2, 2A within the assembly 11. This embodiment of the invention is particularly suited to the pumping of fluids at very low flow rates, and can achieve flow rates low as the order of 100 nanolitres per minute.

Within each chamber 2 is located a flexible, deformable, liquid-impermeable membrane 5, 5A splitting the two chambers 2, 2A into their two compartments 7, 7A and 8, 8A. In this particularly preferred embodiment, the pumps 9, 9A are piezoelectric pumps such as :. those available from Bartells Mikrotechnik, Dortmund, Germany. Such piezoelectric pumps have the inherent advantage of a small size, and the ability to be driven by a relatively low-powered electrical source, such as a dry cell battery. The pumps are inherently capable of pumping either gases or liquids, but need to be operated at different frequencies and/or voltages for each. It is not possible, therefore, to arrange these pumps alone so that they can cope with a possible mixture of gas and liquid. This particular :*, embodiment of a pumping system therefore allows the advantages of the piezoelectric * pumps to be enjoyed when pumping such gas-liquid mixtures, liquid dispersions such as emulsions, or solid dispersions such as suspensions.

In this embodiment of the invention, each membrane 5, 5A is composed of a thin sheet of plastics film such as PVC or low density polyethylene that has been plasticly-deformed such that it can rest in its two extreme configurations (i.e. with the first compartment 7, 7A either empty or full) without requiring to be elastically deformed. In this way, movement of the membrane between these two extreme configurations provides very little or no resistance to pumping. The system can therefore deliver the required low flow rates consistently.

It is a characteristic of piezoelectric pumps that when they are not operating and there is little pressure drop across the inlet and outlet to the pump, the pumps effectively operate as a seal. However, as the pressure differential increases, the pumps will allow flow of liquid through them even in a non-operating state. Particular advantages flow from these characteristics: firstly, by use of appropriate switching mechanisms (not illustrated) to supply power to only one of the piezoelectric pumps 9, 9A, which operate in a urn-directional mode (the inoperative pump acts as a seal) enables one of the first compartments to be filled with liquid whilst the other is emptied. However, should one of the chambers empty (or the other chamber fill completely) the inoperative pump will allow liquid to pass due to the higher pressure differential, thus enabling a recirculating flow between the two compartments 7, 7A to be established, thus preventing any damage to the unit as a whole.

In especially preferred embodiments, the casing of the chambers is made of a translucent :..::: or transparent material (or at least has a translucent or transparent portion) to allow a user, S...

in use, to visualise the flow of liquid from one compartment 7 to another 7A. In this way, a user has a quick visual check on the correct operation of the pumping system. When such a transparent portion is employed, it is particularly effective that the liquid within the r compartment 7, 7A is rendered either opaque or brightly coloured by the addition of a *:*. dye.

A further aspect of the invention is a liquid analyser using a pumping system according to the present invention. Figure 4 illustrates, in cross-sectional view, a portion of such an analyser.

Figure 4A illustrates a portion of such an analyser having a liquid-receiving portion 12 in fluid communication with a sensing element 13 contained within a sensing chamber 14 via a hole 15 at the base of the liquid-receiving portion. Also illustrated in Figure 4A isa drop of liquid 16 deposited, in use, within the liquid receiving portion 12. A further port 17 of the sensing chamber 14 is connected to one of the ports 4 of a pumping system described herein. In this embodiment, the liquid-receiving portion 12 is formed as an indentation, or shallow dish, on the external surface of an analyser. In this way, a small drop of liquid 16 may be deposited into the liquid receiving portion and, when the pumping system is actuated to draw the liquid 16 into the sensing chamber 14 and across the face of the sensor 13, a user can see the droplet 14 diminish in size and be pulled into the analyser. In especially preferred embodiments therefore, the interior surface of the liquid receiving portion 12 is constructed to have a hydrophobic surface, thus causing a liquid placed within the liquid receiving portion to form a discreet, rounded droplet 16, for easy visualisation.

Figure 4B illustrates the configuration when most of the droplet 16 has been drawn into the sensing chamber 14 for analysis. Once the analysis is complete, the direction of operation of the pumping system may be reversed, thus expelling the liquid droplet 16 from the sensing chamber 14 and back into the liquid-receiving dish 12. The droplet can then be readily removed, by e.g. wiping it with a tissue. S. * S

::: In a further embodiment, a capillary tube may be brought into fluid communication with the hole 15 to allow flow of liquid into and/or out of the pumping system to be readily visualised as the liquid rises or falls within the tube. * S. ** * S * * S S. * * * S S.

Claims

1. A pumping system comprising: a chamber, comprising at least two ports; and a deformable liquid-impermeable membrane, within said chamber, located between two of said ports; thereby defining two compartments; and pumping means to pump, in use, a liquid into or out of one of said compartments, thereby causing a change in pressure in said other compartment.

2. A pumping system according to claim 1 comprising a second such chamber and membrane assembly, and wherein the pumping means is configured to transfer, in use, liquid between a first compartment of the first such chamber to a first compartment of the second such chamber; thereby causing an increase in pressure in the second compartment of one chamber and a corresponding decrease in pressure on the second compartment of the other chamber.

3. A pumping system according to either claim 1 or claim 2 wherein said membrane is substantially inelastic.

4. A pumping system according to any preceding claim wherein said pumping means comprises a piezoelectric pump. *

5. A pumping system according to claim 2, or either of claims 3 and 4, when dependent on claim 2, wherein said pumping means comprises two piezoelectric pumps, one such pump configured to pump, in use, liquid from a first compartment of the first chamber to a first compartment of the second chamber; and the second such pump configured to pump, in use, liquid from a first compartment of the second chamber to a first compartment of the first chamber.

6. A pumping system according to any preceding claim wherein at least a portion of said chamber is translucent or transparent, thereby allowing visualisation, in use, of liquid entering or leaving a compartment.

7. A pumping system substantially as described herein, with reference to and as illustrated by any appropriate combination of the accompanying drawings.

8. A liquid analyser comprising: a liquid-receiving portion; a sensing element, in fluid communication with said liquid-receiving portion; liquid transfer means to draw, in use, liquid from said liquid-receiving portion and into contact with said sensing element; wherein said liquid transfer means comprises a pumping system according to any of claims 1-7.

9. A liquid analyser according to claim 8 wherein said liquid-receiving portion comprises an indentation having a hole located towards the base of said indentation.

10. A liquid analyser substantially as described herein, with reference to and as illustrated by any appropriate combination of the accompanying drawings. ****

S *SS*

S

*0*5**

S * ** * S * *5** *S * S * * * S.

10. A liquid analyser according to claim 9 wherein said indentation has a hydrophobic surface.

11. A liquid analyser substantially as described herein, with reference to and as illustrated by any appropriate combination of the accompanying drawings. S. S 4 S I.e S... S * S..

SS

S SS

S S..

S . S.

SS S

S S. S S. S *

-Amendments to the claims have been files as follows:-

-

1. A pumping system comprising: a chamber, comprising at least two ports; and a deformable liquid-impermeable membrane, within said chamber, located between two of said ports; thereby defining two compartments; and a piezoelectric pump to pump, in use, a liquid into or out of one of said compartments, thereby causing a change in pressure in said other compartment.

2. A pumping system according to claim I comprising a second such chamber and membrane assembly, and wherein the pumping means is configured to transfer, in use, liquid between a first compartment of the first such chamber to a first compartment of the second such chamber; thereby causing an increase in pressure in the second compartment of one chamber and a corresponding decrease in pressure on the second compartment of the other chamber.

* 3. A pumping system according to either claim I or claim 2 wherein said membrane is * *.* *** substantially inelastic. ****

* 20 4. A pumping system according to claim 2, or claim 3 when dependent on claim 2, ** wherein said pumping means comprises two piezoelectric pumps, one such pump * *. configured to pump, in use, liquid from a first compartment of the first chamber to a first * S S *sS* * compartment of the second chamber; and the second such pump configured to pump, in * S S use, liquid from a first compartment of the second chamber to a first compartment of the first chamber.

5. A pumping system according to any preceding claim wherein at least a portion of said chamber is translucent or transparent, thereby allowing visualisation, in use, of liquid entering or leaving a compartment.

6. A pumping system substantially as described herein, with reference to and as illustrated by any appropriate combination of the accompanying drawings.

--

7. A liquid analyser comprising: a liquid-receiving portion; a sensing element, in fluid communication with said liquid-receiving portion; liquid transfer means to draw, in use, liquid from said liquid-receiving portion and into contact with said sensing element; wherein said liquid transfer means comprises a pumping system according to any of claims 1-6.

8. A liquid analyser according to claim 7 wherein said liquid-receiving portion comprises an indentation having a hole located towards the base of said indentation.

9. A liquid analyser according to claim 8 wherein said indentation has a hydrophobic surface.