WO2009074180A1

WO2009074180A1 - Valve based or viscosity based control of a fluid pump

Info

Publication number: WO2009074180A1
Application number: PCT/EP2007/063872
Authority: WO
Inventors: Hans-Georg Haertl
Original assignee: Agilent Technologies, Inc.
Priority date: 2007-12-13
Filing date: 2007-12-13
Publication date: 2009-06-18
Also published as: GB2467864A; US20100260617A1; GB201007368D0

Abstract

A pump control (100) for controlling a fluid pump (102) for pumping a fluid, the pump control (100) comprising a pump oil path comprising an oil pump (104) and at least one valve (106, 108), the oil pump (104) being adapted for pumping pump oil to the fluid pump (102), the at least one valve (106, 108) being arranged downstream of the oil pump (104), and a control unit (110) adapted for controlling a pump oil pressure in the fluid pump (102) by switching the at least one valve (106, 108) so that the fluid can be pumped in response to the pump oil pressure.

Description

DESCRIPTION

VALVE BASED OR VISCOSITY BASED CONTROL OF A FLUID PUMP

BACKGROUND ART

[0001] The present invention relates to a pump control.

[0002] In liquid chromatography, a fluidic analyte may be pumped through a column comprising a material which is capable of separating different components of the fluidic analyte. Such a material, so-called beads which may comprise silica gel, may be filled into a column tube which may be connected to other elements (like a control unit, containers including sample and/or buffers) using fitting elements. In liquid chromatography, the mobile phase containing the dissolved analyte may be moved through a stationary phase which is capable of separating different components of the analyte. A liquid chromatography setup may then be connected to other elements like sampling unit, detection unit, sample and solvent pump oil reservoirs and control unit. The movement of the liquid may be enforced through pressure.

[0003] US 4,599,049 discloses a high pressure meter pump system with improved accuracy provided by subdividing a large meter pump capacity into metered subvolume charges which are incrementally delivered to a high pressure slave pump. This enables the pump system to achieve improved accuracy independent of flow rate and therefore increasing the range of flow rates available with acceptable accuracy. Additionally, the pump system self-primes independently of flow rate and therefore does not require degassing of the solvent being pumped.

[0004] EP 0,115,672 discloses a mechanism for pulsation damping in a reciprocating diaphragm pump system which is especially suitable for solvent delivery in modern high pressure liquid chromatography requiring a wide range of solvent flow rates and pressures. The disclosed damper has good overall performance over the full range of liquid chromatographic conditions, a dead volume independent of solvent pressure, and largely eliminates the necessity for continuously pumping the working oil of the diaphragm pump to a maximum operating pressure.

[0005] EP 0,309,596 discloses a pumping apparatus for delivering liquid at a high pressure, in particular for use in liquid chromatography, and comprises two pistons which reciprocate in pump chambers, respectively. The output of the first pump chamber is connected via a valve to the input of the second pump chamber. The pistons are driven by linear drives, e.g., ball-screw spindles. The stroke volume displaced by the piston is freely adjustable by corresponding control of the angle by which the shaft of the drive motor is rotated during a stroke cycle. The control circuitry is operative to reduce the stroke volume when the flow rate which can be selected by user at the user interface is reduced, thus leading to reduced pulsations in the outflow of the pumping apparatus. The pumping apparatus can also be used for generating solvent gradients when a mixing valve connected to different solvent containers is coupled to the input of the pumping apparatus.

[0006] Particularly for modern HPLC (high performance liquid chromatography) requirements, fluids of small volumes have to be pumped with high pressure through the fluidic apparatus. With further decreasing volumes and further increasing pressures, this task may become difficult for conventional pumping systems.

DISCLOSURE

[0007] It is an object of the invention to provide an efficient pumping system. The object is solved by the independent claims. Further embodiments are shown by the dependent claims.

[0008] According to an exemplary embodiment of the present invention, a pump control for controlling a fluid pump (for instance a main pump for pumping a liquid and/or gaseous substance) for pumping a fluid is provided, the pump control comprising a pump oil path (for instance a conduit system having one or more flow controlling components) comprising an oil pump (for instance an auxiliary pump for pumping a pump oil for indirectly effecting the pumping characteristic of the fluid) and at least one valve (which may be any component switched in a flow path of the pump oil and selectively controlling whether or not or to which extent the pump oil is guidable through the pump oil path), the oil pump being adapted for pumping pump oil to the fluid pump, the at least one valve being arranged downstream (in a pump oil flow direction) of the oil pump, and a control unit (for instance a processor) adapted for controlling a pump oil pressure in the fluid pump (for instance exclusively) by switching the at least one valve so that the fluid can be pumped in response to the pump oil pressure (for instance as a consequence of a functional coupling between the pump oil path and a fluid path, for instance mediated through an impermeable membrane separating the pump oil from the fluid).

[0009] According to another exemplary embodiment, a pump system is provided, the pump system comprising a fluid pump for pumping a fluid, and a pump control having the above mentioned features for controlling the fluid pump for pumping a fluid.

[0010] According to still another exemplary embodiment, a method of controlling a fluid pump for pumping a fluid is provided, the method comprising providing a pump oil path comprising an oil pump and at least one valve arranged downstream of the oil pump, pumping pump oil by the oil pump to the fluid pump, and controlling a pump oil pressure in the fluid pump by switching the at least one valve so that the fluid can be pumped in response to the pump oil pressure.

[0011 ] According to still another exemplary embodiment of the present invention, a pump control for controlling a fluid pump for pumping a fluid is provided, the pump control comprising an adjustment unit (for instance a processor) adapted for adjusting (for instance increasing or decreasing) a viscosity (which may be denoted as a material's resistance to flow) of pump oil to thereby adjust a pumping characteristic of the fluid pump.

[0012] According to yet another exemplary embodiment, a method of controlling a fluid pump for pumping a fluid is provided, the method comprising adjusting a viscosity of pump oil to thereby adjust a pumping characteristic of the fluid pump.

[0013] According to a first exemplary aspect, a pump control is provided having an oil pump in functional interaction with a fluid pump to be controlled. The pump oil system and the fluid system are hydraulically coupled so that the control of a pump oil pressure within the pump oil path has an impact on the fluid pressure of the fluid pump and is controlled by switching one or more valves. Therefore, (for instance electronic) valve control signals may allow to control the fluid pressure in a defined manner, thereby allowing to control the fluid pump with improved precision and time resolution. Such a configuration may allow to combine the high pressure capability of a high- pressure oil pump with the low fluid volume requirements of a fluid pump such as a microfluidic pump.

[0014] According to a second exemplary aspect, a viscosity of pump oil in a pumping system is controlled or modulated to thereby adjust or set a desired pumping characteristic, for instance to set a flow or an effective pumping pressure. Such a pump oil viscosity can be controlled by the variation of electric fields, of magnetic fields, of temperature or of any other physical parameter having an impact on the viscosity of the material of the pump oil. For example, the viscosity of an electrorheological fluid used as a pump oil may be controlled over a very broad range and with a very fast time resolution by applying and releasing electric fields.

[0015] In the following, further exemplary embodiments of the pump control according to the first exemplary aspect will be explained. However, these embodiments also apply to the pump system according to the first exemplary aspect, to the method of controlling a fluid pump according to the first exemplary aspect, and to the pump control and the method of pumping a fluid by a fluid pump according to the second exemplary aspect.

[0016] The oil pump may be a high-pressure pump. For example, this high pressure pump may be realized as a commercially available hydraulic oil pump in order to bring oil to a high pressure, for instance of hundreds to thousands bar.

[0017] The oil pump may be adapted for generating a pressure of at least about 500 bar, particularly of at least about 800 bar, more particularly of at least about 1000 bar. These pump oil pressures may be appropriate to bring a fluid to be conducted via the coupled fluid pump to a sufficiently high pressure, particularly so that it can be used with modern chromatographic systems such as HPLC systems (high performance liquid chromatography).

[0018] The pump control may comprise a pump oil reservoir for accommodating pump oil. Such a pump oil reservoir may be a container in which pump oil is accommodated. For pump oil, silicone oil or any mineral or vegetable oil may be used. It may be particularly advantageous to use an electrorheological fluid as pump oil. Electrorheological fluids (ERFs) may be denoted as suspensions of extremely fine non-conducting particles (for instance up to 50 μm diameter) in an electrically insulating fluid. The viscosity of such fluids may change reversibly over an extremely broad range (for instance by an order of 10 or even 100.000) in response to an electric field. For example, a typical ERF can be converted from the consistency of a liquid to that of a gel or even a solid, and back, with fast response times for instance in the order of milliseconds. Examples of the ERFs are crude oil, silicone oil, vegetable oil such as olive oil or sunflower oil, mixed with corresponding particles such as natural polymers, polymeric salts, etc. By using an ERF as pump oil, the application of electric fields in capacitor-like valves may be used to control the viscosity and therefore the pressure conditions in the system.

[0019] As an alternative to an architecture in which a pump oil reservoir is used having a dedicated storage volume for oil and an inlet and an outlet, it is also possible to provide the pump control system as a closed loop without a dedicated oil reservoir, so that the pump oil may then be accommodated in closed loop lines or conduits.

[0020] The at least one valve may comprise an inlet valve arranged, in a pumping direction, downstream of the pump oil reservoir and upstream of the fluid pump. In other words, the pump oil may then be conducted from the pump oil reservoir to the oil pump, from there to the inlet valve and subsequently to the fluid pump. Thus, by controlling whether the inlet valve is open or closed, and to which extent the inlet valve is open, it is possible to control a pressure of pump oil to be supplied from the pump oil reservoir to the fluid pump, so that an impact of the pump oil system to the fluid system is adjustable.

[0021 ] The at least one valve may comprise an outlet valve arranged, in a pumping direction, downstream of the fluid pump and upstream of the pump oil reservoir. In other words, the pump oil may then be conducted from the fluid pump, from there to the outlet valve and subsequently to the pump oil reservoir. Such an outlet valve may bridge an impact region of the pump oil on the fluid pump and a backflow into the fluid container. Also by controlling the outlet valve to be closed, opened, or opened to a certain extent, it is possible to precisely influence the pressure conditions within the fluidic system.

[0022] The at least one valve may comprise an electric field generator unit adapted for generating an electric field for adjusting a viscosity of the pump oil comprising an electrorheological fluid (ERF). By implementing an electric field generator such as capacitor plates, particularly a cylinder capacitor, it is possible to locally manipulate the viscosity of the pump oil within the electric field generator unit with high precision so that a high oil throughput can be achieved by switching off the electric field and a slow pump oil flow can be achieved by applying an electric field, wherein the fast response time of electrorheological fluids which may be in the order of magnitude of milliseconds can be beneficially used.

[0023] The at least one valve may comprise a cylinder capacitor through which the pump oil is guidable via a lumen (such as a hollow cylindrical conduit) formed between two cylindrical electrodes of the cylinder capacitor. The cylinder capacitor may be formed by an inner cylinder and an outer hollow cylinder being arranged concentrically to one another and delimiting a lumen in between. By applying an electric voltage between the two cylindrical electrodes to generate an electric field, an electrorheological fluid flowing through the lumen can be controlled over a very wide range regarding fluid viscosity, thereby effectively controlling the pressure in the system.

[0024] The control unit may be adapted for controlling a pump oil pressure in the fluid pump by switching the at least one valve based on an electric control signal (for instance a current or a voltage signal, which may be pulsed). Since an electric control signal such as a pulse may be used as a switching signal, a fast switching and controlling of the pressure may be achieved, for instance with a frequency of at least about 1 Hz, particularly of at least about 5 Hz, more particularly of about at least 10 Hz. Therefore, a very fast switching may be enabled which cannot be obtained easily with mechanical valves. As an alternative to an electric switching signal, it is possible to use an electromagnetic radiation switching signal which may be a light pulse (which, for instance, can be converted into an electric signal using optoelectronic converters).

[0025] At least one further valve may be provided in addition to the inlet valve and/or the outlet valve and may be arranged downstream of the oil pump. In such a configuration, a single pump control may be used in combination with a plurality of fluid pumps, wherein individual valves may be arranged between the pump control and the individual ones of the fluid pumps.

[0026] The pump control, more precisely a membrane-based interface between the pump oil path and the fluid path may be free of a piston. In other words, it may be dispensable to provide a piston acting on pumping oil in a housing having a membrane dividing the housing into a pump oil compartment and a fluid compartment. Therefore, by omitting a mechanically reciprocating piston, the number of movable parts can be reduced and the system can be kept simple and small. The pump control can then be achieved by simply controlling viscosity of the fluid passing electrically controlled valves.

[0027] In the following, further exemplary embodiments of the pump system according to the first exemplary aspect will be explained. However, these embodiments also apply to the pump control according to the first exemplary aspect and to the method of controlling a fluid pump for pumping a fluid according to the first exemplary aspect. These embodiments also apply to the pump control and to the method of pumping a fluid by a fluid pump according to the second exemplary aspect.

[0028] The fluid pump may comprise a housing and a mechanically flexible (particularly impermeable) membrane dividing an interior of the housing into a pump oil department (in fluid communication with the pump oil) and into a fluid department(in fluid communication with the fluid). The control unit may be adapted for controlling pump oil pressure in the pump oil department thereby exerting a pumping force on fluid in the fluid department via the resulting motion of the flexible membrane. In other words, the valves may define the pump oil pressure characteristics in the pump oil department. Via the flexible membrane, the corresponding forces are transferred or translated to the fluid which is controlled accordingly.

[0029] The fluid department may comprise an inlet coupled to a fluid reservoir (such as one or more solvent containers) and may comprise an outlet via which the pressurized fluid may be supplied to a unit to further process the pressurized fluid. A fluid path may be directed from the fluid reservoir, through the inlet, through the fluid department, and through the outlet.

[0030] The inlet may be coupled to a fluid reservoir (for instance storing solvents or a sample, for instance a biological sample), and the outlet may be connected to a fluid separation system such as a chromatographic column. Therefore, a fluid separation may be performed with a high pressure which may be particularly advantageously for modern HPLC arrangements.

[0031 ] The pump system may further comprise a fluid pre-pump arranged between the fluid reservoir and the inlet. The fluid pre-pump may be a low pressure pump for precisely adjusting a desired fluid flow and may be a precise piston pump or plunger pump (for instance operating at a pressure of about 5bar). This low pressure fluid pre- pump in combination with the valve controlled high pressure pump and the pump oil path may define both an accurate and a high pressure system which allows to process even very small fluid volumes.

[0032] The fluid department may comprise an outlet coupled to a fluid separation unit, particularly a chromatographic column. In liquid chromatography, a fluidic analyte (brought to a high pressure by the pump system) may be pumped through a column comprising a material which is capable of separating different components of the fluidic analyte. Such a material, so-called beads, may be filled into a column tube which may be connected to other elements (like a processor, containers including sample and/or buffers) using fitting elements. Before analysis on a column, the fluidic analyte is loaded into the liquid chromatography apparatus. A steering unit controls an amount of fluidic sample to be loaded on the liquid chromatography apparatus.

[0033] In addition to the above described fluid pump, the pump system may comprise at least one further fluid pump. The pump control may be adapted for controlling pumping of the fluid by the fluid pump and by the at least one further fluid pump. For example, in such an embodiment, it is possible that one pump control is used to simultaneously control multiple fluid pumps, thereby allowing the implementation of very complex systems with a simple construction.

[0034] The fluid department of the oil-fluid interface housing may comprise an outlet coupled to a fluidic device. Thus, a fluidic device may be supplied with a liquid, fluid or sample under a desired pressure condition, for instance under high pressure.

[0035] The fluidic device may be adapted to analyze at least one physical, chemical and/or biological parameter of at least one compound of a fluidic sample. Examples for physical parameters are temperature, pressure, volume or the like. Examples for chemical parameters are concentration of a component, a pH value of a liquid, or the like. Examples for biological parameters are the presence or absence or concentration of proteins or genes in a solution, the biological activity of a sample, or the like.

[0036] The fluidic device may comprise at least one of a sensor device, a device for chemical, biological and/or pharmaceutical analysis, a capillary electrophoresis device, a liquid chromatography device, a gas chromatography device, an electronic measurement device, and a mass spectroscopy device. Exemplary application fields are gas chromatography, mass spectroscopy, UV spectroscopy, optical spectroscopy, IR spectroscopy, liquid chromatography, and capillary electrophoresis (bio-) analysis. The fluidic device may be integrated in an analysis device for chemical, biological and/or pharmaceutical analysis. When the fluidic device is a device for chemical, biological and/or pharmaceutical analysis, functions like (protein) purification, electrophoresis investigation of solutions, fluid separation, or chromatography investigations may be performed with such an analysis device. Particularly, the fluidic device may be a high performance liquid chromatography device (HPLC) by which different fractions of an analyte may be separated, examined and analyzed.

[0037] In the following, further exemplary embodiments of the pump control according to the second exemplary aspect will be explained. However, these embodiments also apply to the method of pumping a fluid by a fluid pump according to the second exemplary aspect, the pump control according to the first exemplary aspect, the pump system according to the first exemplary aspect and the method of controlling a fluid pump for pumping a fluid according to the first exemplary aspect.

[0038] The adjustment unit may be adapted for adjusting a viscosity of pump oil comprising an electrorheological fluid (ERF) by applying an electric field to the pump oil in at least a portion of a pumping path. Selectively modulating the viscosity of an ERF by the pump control may allow to adjust the viscosity of the pump oil, thereby effecting an indirect but well-defined, accurate and reliable impact on the fluid to be pumped.

[0039] Additionally or alternatively, the adjustment unit may be adapted for adjusting a viscosity of pump oil comprising a magnetorheological fluid (MRF) by applying a magnetic field to the pump oil in at least a portion of a pumping path. A magnetorheological fluid may be a suspension of micrometer sized magnetic particles in a carrier fluid, for instance a type of oil. When subjected to a magnetic field (which may be generated for instance by a coil having an opening through which the magnetorheological fluid flows), the fluid greatly increases its viscosity to the point of becoming a viscoelastic solid. The viscosity can be controlled precisely by varying the magnetic field intensity.

[0040] Further additionally or alternatively, the adjustment unit may be adapted for adjusting a viscosity of pump oil by manipulating a temperature of the pump oil (for instance by selectively cooling or heating the pump oil) in at least a portion of the pumping path. For instance, the fluid can be pumped through a chamber having a controllable temperature where it may be brought in contact with a thermoelectric heating/cooling element which can control the temperature of the fluid efficiently, thereby having an impact on the viscosity. Thus, also the temperature dependence of the viscosity of pump oil may be used for pump control purposes.

[0041] The pump control may be adapted for controlling a m icroflu id ic fluid pump. The term "microfluidic" may particularly denote that a volume of the fluids pumped through the system may be in the order of magnitude of microlitres or hundreds of microlitres. Furthermore, the dimensions of channels of the fluid pump may be in the order of magnitude of micrometres to millimetres.

[0042] The pump control may be adapted for controlling a fluid pump coupled with a fluid separation unit, particularly with a chromatographic column. Such a chromatographic column may be filled with beads and may allow for a separation of a mobile phase based on a characteristic interaction with a stationary phase.

[0043] Exemplary embodiments may overcome the conventional shortcoming that the dynamic switch stroke of valves may be too small. Typically, it may be 20:1. In contrast to this, exemplary embodiments may operate with a significantly larger switch stroke (i.e. ratio of pressure drop in an open state/pressure drop in a closed state or flow in an open state /flow in a closed state). According to an exemplary embodiment, since significantly more pump oil under pressure is available than required, it is possible to pump back a part thereof without use. When switching two ERF valves in series and switching a non-linear dissipation resistance in between, it is possible that always a part of the pressure oil flows away without being used, but when the two ERF valves are closed, this portion is significantly larger than in an opened state. By taking this measure, the switch stroke of the arrangement may be significantly increased. Even under undesired circumstances where such a measure may be not sufficient, it is possible to add one or more further stages in a serial configuration.

[0044] According to an exemplary embodiment, a common rail booster pump may be provided. Such a booster pump may be a further development of a pump implemented in a 1090 liquid chromatography system of Agilent Technologies. Conventional pistons in a control section may be substituted by a valve controlled high pressure pump with an inlet valve and an outlet valve which may be switched in a controlled manner, so that at each time, the pulses may control opening of one of the valves and closing of another one. By taking this measure, high frequencies of up to 20 Hz or more may be obtained.

[0045] Such valves may be ERF valves. In an embodiment, at least three of these ERF valves may be provided. This may allow to increase the dynamical range, particularly the ratio between a maximum pressure and a minimum pressure which, for instance may be 1200 bar/3 bar = 400. Exemplary embodiments may allow for a common rail construction with a plurality of booster arrangements connected in parallel to one another.

[0046] Exemplary embodiments may particularly be appropriate for small flow volumes and high pressure values. In such an operation mode, the incompressibility of liquids does no longer apply strictly. For a precise pump flow it may be therefore necessary to know the fluid properties. For solving such problems by exemplary embodiments, the viscosity of pump oil may be adjusted in order to control a fluid pump. By controlling the time dependence of the pumping scheme by means of electrical signals in contrast to a mechanical control, high pumping frequencies of 10 Hz and more are achievable, and a user-defined adjustment of the pump frequency is possible. The stress acting on the pump may be reduced since a load only has to be applied when this is necessary. [0047] ERFs may be particularly advantageous for a use in a pump, since these materials may have non-abrasive properties (i.e. they do not destroy or deteriorate the pump). Furthermore, ERFs do not have a strong tendency to sediment, may be long- lasting and applicable even under harsh conditions. Furthermore, ERFs are appropriate since they have a fast frequency response. For instance, silicone oil with small particles may be used as ERFs. Since ERFs may be cheap, they are appropriate as pump oil which may be required to be replaced from time to time.

[0048] It is possible to provide a plurality of ERF valves (some of them may have a high resistance, other ones may have a low resistance, so as to allow for different pressure drops). These effects are enhanceable, and the pressure of the oil booster may be varied over a wide range. Simultaneously, the low pressure pump may be prevented from damage. A non-linear flow resistor may be switched into the pump oil path, which can also be realized as an ERF valve. Such an element may ensure that the resistance does not increase in a non-linear manner with the flow. In this context, non-linear turbulence effects may be considered.

[0049] Due to the electronic control, a high degree of freedom regarding the adjustability can be achieved. Particularly, a pump control with a high pressure pump may be provided controlling the oil pressure in a booster pump, wherein at least one valve is switched in a piston-free manner to realize such a control performance. This may allow for a fast switch by using electronically adjustable valves. The pump may be controlled by modification of the viscosity of the pump oil. With such a configuration, high switching frequencies of 20 Hz and more may be obtained and it is no longer necessary to know the fluid characteristics (such as a temperature-pressure dependency or behaviour and fluid compressibility). A high pressure pump implementable in the pump oil path can be a commercially available hydraulic pump (for instance a vane-type pump or a piston pump).

[0050] A fluid processing element, such as a chromatographic column, may be provided downstream of the housing in which the membrane is mounted and may be filled with a fluid separating material. Such a fluid separating material which may also be denoted as a stationary phase may be any material which allows an adjustable degree of interaction with a sample so as to be capable of separating different components of such a sample. The fluid separating material may be a liquid chromatography column filling material or packing material comprising at least one of the group consisting of polystyrene, cellulite, polyvinylalcohol, polytetrafluoroethylene, glass, polymeric powder, silicon dioxide and other suitable metal oxides. However, any packing material can be used which has material properties allowing an analyte passing through this material to be separated into different components, for instance due to different kinds of interactions or affinities between the packing material and fractions of the analyte.

[0051] The processing element may be filled with a fluid separating material, wherein the fluid separating material may comprise beads having a size in the range of essentially 1 μm to essentially 50 μm. Thus, these beads may be small particles which may be filled inside the separation columns. The beads may have pores having a size in the range of essentially 0.02 μm to essentially 0.03 μm. The fluidic sample may be passed through the pores, wherein an interaction may occur between the fluidic sample and the pores. By such effects, separation of the fluid may occur.

[0052] Optionally, the described fluid processing element may be followed by a further processing element and may have a size which differs from a size of the further processing element. Particularly, the processing element (enrichment-column) may be significantly smaller than the further processing element (main column). This different size may result in a different volume capability and in different fluid separation probabilities of the two processing elements, which may be adjusted or adapted to one another.

[0053] The fluidic system may be adapted as a fluid separation system for separating components of the mobile phase. When a mobile phase including a fluidic sample is pumped through the fluidic system, for instance with a high pressure, the interaction between a filling of the column and the fluidic sample may allow for separating different components of the sample, as performed in a liquid chromatography device or in a gel electrophoresis device.

[0054] However, the fluidic device may also be adapted as a fluid purification system for purifying the fluidic sample. By spatially separating different fractions of the fluidic sample, a multi-component sample may be purified, for instance a protein solution. When a protein solution has been prepared in a biochemical lab, it may still comprise a plurality of components. If, for instance, only a single protein of this multi- component liquid is of interest, the sample may be forced to pass the columns. Due to the different interaction of the different protein fractions with the filling of the column (for instance using a gel electrophoresis device or a liquid chromatography device), the different samples may be distinguished, and one sample or a band of material may be selectively isolated as a purified sample.

BRIEF DESCRIPTION OF DRAWINGS

[0055] Other objects and many of the attendant advantages of embodiments of the present invention will be readily appreciated and become better understood by reference to the following more detailed description of embodiments in connection with the accompanied drawings. Features that are substantially or functionally equal or similar will be referred to by the same reference signs.

[0056] Fig. 1 and Fig. 2 show pump systems according to exemplary embodiments.

[0057] Fig. 3 shows an ERF valve realized by a cylinder capacitor according to an exemplary embodiment.

[0058] Fig. 4 and Fig. 5 illustrate pump systems according to exemplary embodiments.

[0059] Fig. 6 illustrates a high performance liquid chromatography apparatus according to an exemplary embodiment.

[0060] The illustration in the drawing is schematically.

[0061] In the following, referring to Fig. 1 , a pump system 150 according to an exemplary embodiment will be explained.

[0062] The pump system 150 comprises a fluid pump 102 for pumping a fluid such as a solvent for a biochemical separation procedure. Furthermore, a pump control 100 is provided for controlling the fluid pump 102 for pumping the fluid.

[0063] The pump control 100 is adapted for controlling the fluid pump 102 for pumping the fluid and comprises a closed pump oil path comprising a pump oil container 112, an oil pump 104 and two valves 106, 108. The oil pump 104 is adapted for pumping pump oil from the pump oil container 112 to the fluid pump 102 (in a direction as indicated by arrows in Fig. 1 ) and back into the pump oil container 112. The valves 106, 108 are arranged downstream of the oil pump 104, in the pumping direction. A control unit 110 such as an electronic control box is provided for controlling a pump oil pressure in the fluid pump 102 by selectively switching the valves 106, 108 using electric switch signals 114 so that the fluid in the fluid pump 102 (which is hydraulically coupled to the pressurized pump oil via a flexible impermeable membrane 132) can be pumped in response to the pump oil pressure.

[0064] The oil pump 104 is a high pressure pump for generating a pressure of, for instance, 800 bar. The pump oil reservoir 112 is provided for accommodating a pump oil which is a mixture of a silicone oil and small particles selected so that the pump oil is an electrorheological fluid (ERF).

[0065] The inlet ERF valve 106 is provided and arranged, in a pumping direction, downstream of the pump oil reservoir 112 and upstream of the fluid pump 102. The outlet ERF valve 108 is provided in a pumping direction downstream of the fluid pump 102 and upstream of the pump oil reservoir 112. The valves 106, 108 are controlled by the control unit 110. For that purpose, the pulsed electronic control signals 114 are supplied from the control unit 110 to the valves 106, 108. Since these control signals 114 are electronic control signals, the control can be performed with a high time precision of, for instance, a frequency of 10 Hz. The control signals 114 may be provided individually for each valve 106, 108, or may be provided in common for multiple valves 106, 108. The control signals 114 for the valves 106, 108 may be identical or may differ, for instance may have a phase shift of 90° or 180° with respect to one another.

[0066] No piston is required in a housing 130 in which the pump oil effects the fluid, as will be explained in the following in more detail. The fluid pump 102 namely comprises the housing 130 and a movable displaceable flexible impermeable membrane 132 dividing an interior volume of the housing 130 into a pump oil department 134 for accommodating the pump oil and into a fluid department 136 for accommodating the fluid. The control unit 1 10 is adapted for directly controlling the pump oil pressure in the pump oil department 134 thereby exerting a pumping force also on the fluid in the fluid department 136 via the flexible membrane 132 so that the control unit 110 indirectly controls the fluid pressure in the fluid department 136.

[0067] The fluid department 136 comprises an inlet 138 coupled to a fluid reservoir 140 (in which a solvent or a sample may be provided) and comprises an outlet 142. A fluid pre-pump 144 is arranged between the fluid reservoir 140 and in the inlet 138. The fluid pre-pump 140 is a low pressure pump having a maximum pressure of, for instance, 5 bar. The outlet 142 is coupled to a chromatographic column 146.

[0068] Since the container 112 comprises an electrorheological fluid which is pumped by the high pressure pump 104 through the pump control 100, the valves 106, 108 may control the pumping characteristics by applying electric field on the basis of the control signals 114 thereby effecting the viscosity of the pump oil in a time dependent manner to thereby open, close or partially open the valves 106 and/or 108. In addition to the already described components, a high pressure damping unit 152 is provided between the high pressure pump 104 and the inlet valve 106. The high pressure damper 152 may serve as a damping element to keep the pressure constant. The control unit 110 may be an electronic control box, and may be realized by a central processing unit (CPU) or a microprocessor. The fluid pre-pump 144 may be a low pressure solvent pump. Fig. 1 illustrates a booster with ERF valves 106, 108.

[0069] In the following, referring to Fig.2, a pump system 250 according to another exemplary embodiment will be explained.

[0070] The pump system 250 is formed by a pump control 200 and a fluid pump 102 of the type as explained above. The pump system 250 may allow for a dynamic range extension of the inlet valve configuration.

[0071] In addition to the components shown in Fig. 1 , the embodiment of Fig. 2 further comprises a non-linear flow resistor 202 which may be realized as an ERF valve. An additional ERF valve 204 is provided downstream of the inlet valve 106 and upstream of the fluid pump 102. In Fig. 2, the nonlinear restrictor 202 is adapted for restricting the oil flow from between the two valves 106, 204 upstream of the chamber 130.

[0072] Fig. 3 shows an exemplary construction of the ERF valve 106, wherein the ERF valves 108, 204 may be constructed in a similar or identical manner.

[0073] The ERF valve 106 comprises an electric field generator unit 300, namely a current or voltage source for generating an electric field by applying a corresponding voltage between an inner cylindrical metallic member 302 and an outer cylindrical metallic member 304 of the cylinder capacitor structure 106. For applying and non- applying the electric field in a selective manner, a switch 308 (such as a transistor switch) may be selectively closed or opened. A fluid flowing through a lumen 306 between the inner full cylinder 302 and the outer hollow cylinder or tube 304 may then be controlled regarding viscosity, in dependence of the presently applied electric field value.

[0074] In other words, the valve 106 comprises a cylinder capacitor formed by the cylindrical elements 302, 304 delimiting the lumen 306 through which the pump oil is guidable. Other designs are also possible.

[0075] Fig. 4 shows a pump system 400 according to another exemplary embodiment having a pump control 100 as shown in Fig. 1. Additionally, a plurality of fluid pumps 102 are connected in parallel to the pump control 100 which controls the plurality of fluid pumps 102 simultaneously. Outlets 142 of the fluid pumps 102 are connected so as to perform a mixing between different fluids at a mixing point 402. Alternatively, it is possible to further process some or all of the fluids at the fluid outlets 142 of the fluid pumps 102 individually, instead of mixing them.

[0076] Fig. 5 illustrates a pump system 510 according to another exemplary embodiment having a modified pump control 500 which is based on the pump control 100 but comprises additional ERF valves 502 assigned to each individual one of the several fluid pumps 102. As indicated by reference numeral 100', the pump control 100 of Fig. 1 may be modified for the configuration of Fig. 5 in a manner that the valves 106, 108 of Fig.1 may be dispensable in view of the provision of separate ERF valves 502 assigned to each of the fluid pumps 102. Thus, the pump control 100 may or may not comprise the ERF valves 106, 108, since their function can be supplemented or substituted by the individual valves 502. Outlets 142 of the fluid pumps 102 are connected so as to perform a mixing between different fluids at a mixing point 402. Alternatively, it is possible to further process some or all of the fluids at the fluid outlets 142 of the fluid pumps 102 individually, instead of mixing them.

[0077] Fig. 6 shows a HPLC system 610 implementing a pump system 620 according to an exemplary embodiment. Such a pump system 620 may be configured for instance similar to the pump systems 150, 250 shown in Fig. 1 or Fig. 2.

[0078] The HPLC system 610 may be used in the context of liquid chromatography. The pump 620 pumps a mobile phase towards a separation device 630 (for instance a chromatographic column), which includes a stationary phase. A sample supply unit 640 is arranged between the pump 620 and the separation device 630 in order to insert a sample into the mobile phase, if desired. The stationary phase of the separation device 630 is provided to separate components of the sample. A detector 650 detects separate components of the sample, and a fractioning device 660 can be provided to output separate components of the sample fluid, for instance into a waste container or sample containers provided for that purpose.

[0079] In a simple embodiment, the pump oil of a mechanical reciprocating oil pump (similar to the 1090 Booster pump) can be replaced by an ER-Fluid and the override valve is then supplemented or replaced with an ERF-Valve.

[0080] It should be noted that the term "comprising" does not exclude other elements or features and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

1. A pump control (100) for controlling a fluid pump (102) for pumping a fluid, the pump control (100) comprising

a pump oil path comprising an oil pump (104) and at least one valve (106, 108), the oil pump (104) being adapted for pumping pump oil to the fluid pump (102), the at least one valve (106, 108) being arranged downstream of the oil pump (104); and

a control unit (110) adapted for controlling a pump oil pressure in the fluid pump (102) by switching the at least one valve (106, 108) so that the fluid can be pumped in response to the pump oil pressure.

2. The pump control (100) according to claim 1 , comprising at least one of the following features:

the oil pump (104) is a high-pressure pump;

the oil pump (104) is adapted for generating a pressure of at least 500 bar, particularly of at least 800 bar, more particularly of at least 1000 bar;

the at least one valve (106, 108) comprises an electric field generator unit (300) adapted for generating an electric field for adjusting a viscosity of the pump oil comprising an electrorheological fluid;

the at least one valve (106) comprises a cylinder capacitor (302, 304) through which the pump oil is guidable via a lumen (306) formed between two cylindrical electrodes of the cylinder capacitor (304, 306);

the pump control (100) comprises a pump oil reservoir (112) accommodating an electrorheological fluid;

the pump control (100) comprises at least one further valve (502) arranged downstream of the oil pump (104);

the pump control (100) is adapted as a piston-free pump control.

3. The pump control (100) according to claim 1 or any one of the preceding claims,

comprising a pump oil reservoir (112) for accommodating pump oil.

4. The pump control (100) according to claim 3, comprising at least one of the following features:

the at least one valve comprises an inlet valve (106) arranged, in a pumping direction of the oil pump (104), downstream of the pump oil reservoir (112) and upstream of the fluid pump (102);

the at least one valve comprises an outlet valve (108) arranged, in a pumping direction of the oil pump (104), downstream of the fluid pump (102) and upstream of the pump oil reservoir (112).

5. The pump control (100) according to claim 1 or any one of the preceding claims,

wherein the control unit (110) is adapted for controlling pump oil pressure in the fluid pump (102) by switching the at least one valve (106, 108) based on an electric control signal (1 14).

6. The pump control (100) according to claim 5,

wherein the electric control signal (114) has a frequency of at least 1 Hz, particularly of at least 5 Hz, more particularly of at least 10 Hz.

7. A pump system (150), the pump system (150) comprising

a fluid pump (102) for pumping a fluid;

a pump control (100) according to claim 1 or any one of the preceding claims for controlling the fluid pump (102) for pumping a fluid.

8. The pump system (150) according to claim 7,

wherein the fluid pump (102) comprises a housing (130) and a flexible membrane (132) dividing an interior of the housing (130) into a pump oil department (134) and into a fluid department (136); wherein the control unit (110) is adapted for controlling the pump oil pressure in the pump oil department (134) thereby exerting a pumping force on fluid in the fluid department (136) via the flexible membrane (132).

9. The pump system (150) according to claim 8,

wherein the fluid department (136) comprises an inlet (138) coupled to a fluid reservoir (140) and comprises an outlet (142).

10. The pump system (150) according to claim 9,

comprising a fluid pre-pump (144) arranged between the fluid reservoir (140) and the inlet (138).

11. The pump system (150) according to claim 10,

wherein the fluid pre-pump (140) is a low-pressure pump.

12. The pump system (150) according to claim 8 or any one of the preceding claims,

wherein the fluid department (136) comprises an outlet (142) coupled to a fluid separation unit (146).

13. The pump system (150) according to claim 12,

wherein the fluid separation unit (146) comprises a chromatographic column.

14. The pump system (400) according to claim 7 or any one of the preceding claims,

comprising at least one further fluid pump (102);

wherein the pump control (100) is adapted for controlling pumping of the fluid by the fluid pump (102) and by the at least one further fluid pump (102).

15. The pump system (100) according to claim 8 or any one of the preceding claims,

wherein the fluid department (136) comprises an outlet (142) coupled to a fluidic device (146).

16. The pump system (100) according to claim 15, comprising at least one of the following features:

the fluidic device (146) is adapted to analyze at least one physical, chemical and/or biological parameter of at least one compound of a fluidic sample;

the fluidic device comprises at least one of the group consisting of a sensor device, a test device for testing a device under test or a substance, a device for chemical, biological and/or pharmaceutical analysis, an electrophoresis device, a capillary electrophoresis device, a liquid chromatography device (146), a gas chromatography device, a gel electrophoresis device, an electronic measurement device, and a mass spectroscopy device.

17. The pump system (100) according to claim 7 or any one of the preceding claims,

comprising a separation unit (146), particularly a chromatographic column, adapted for separating different components of the fluid and being in fluid communication with the fluid pump (102).

18. A method of controlling a fluid pump (102) for pumping a fluid, the method comprising

providing a pump oil path comprising an oil pump (104) and at least one valve (106, 108) arranged downstream of the oil pump (104);

pumping pump oil by the oil pump (104) to the fluid pump (102);

controlling a pump oil pressure in the fluid pump (102) by switching the at least one valve (106, 108) so that the fluid can be pumped in response to the pump oil pressure.

19. A pump control (100) for controlling a fluid pump (102) for pumping a fluid, the pump control (100) comprising

an adjustment unit (106, 108, 110) adapted for adjusting a viscosity of pump oil to thereby adjust a pumping characteristic of the fluid pump (102).

20. The pump control (100) according to claim 19, comprising at least one of the following features: the adjustment unit (106, 108, 110) is adapted for adjusting a viscosity of pump oil comprising an electrorheological fluid by applying an electric field to the pump oil in at least a portion of a pumping path;

the adjustment unit (106, 108, 110) is adapted for adjusting a viscosity of pump oil comprising a magnetorheological fluid by applying a magnetic field to the pump oil in at least a portion of a pumping path;

the adjustment unit (106, 108, 110) is adapted for adjusting a viscosity of pump oil by adjusting a temperature of the pump oil in at least a portion of a pumping path;

the pump control (100) is adapted for controlling a microfluidic fluid pump (102);

the pump control (100) is adapted for controlling a fluid pump coupled with a fluid separation unit (146), particularly with a chromatographic column.

21. A method of pumping a fluid by a fluid pump (102), the method comprising

adjusting a viscosity of pump oil to thereby adjust a pumping characteristic of the fluid pump (102).