Electroactive chamber pump system and method for operating an electroactive chamber pump

Abstract

A chamber pump system 1 and associated method of use is defined. The pump system 1 comprises: at least one chamber pump 1 where the pump comprises a deformable chamber membrane 8, which defines a pump

Description

TECHNICAL FIELD The present invention relates to electroactive chamber pump systems having a dielectric elastomer transducer and to approaches to optimally operate a chamber pump system in terms of efficiency, throughput, and noise generation. TECHNICAL BACKGROUND Pump systems are integral components in a wide range of technical applications including medical devices and industrial processing where fluids have to be transported or pressurized or where a vacuum (e.g. 100 mbar) or an overpressure has to be generated. Along the broad variety of pumping systems, electroactive chamber pumps actuated with dielectric elastomer-based transducers have recently shown promising properties such as light weight, increased reliability, facilitated maintenance, energy efficient operation and a compact design making them highly robust and well suited for harsh environments. Dielectric elastomer transducers have a sheet-shaped elastomer-based dielectric material sandwiched between compliant soft electrodes. The working principle of a dielectric elastomer transducer as an actuator is based on the compression of a dielectric elastomer membrane produced by an electrostatic pressure between the soft electrodes. By applying a high electrical voltage, an electrical field is formed across the dielectric elastomer material which induces electrostatic forces that cause the dielectric elastomer material to deform. The compression of the elastomer leads to a corresponding expansion as the elastomers are considered as incompressible or slightly compressible. The resulting dielectric elastomer transducer may be attached to a rigid body so that the mechanical motion of the dielectric elastomer material is translated into actuation of, for instance, stiff structures. Due to its elastic properties, the deformation may return to the original state when the electrical field is removed. Also, dielectric elastomers transducers can be utilized as sensors. When a mechanical force applied thereon, it induces a deformation in the dielectric elastomer material altering the capacitance between the soft electrodes. By measuring the change of capacitance, the impacting force or deformation can be quantified. It is an object of the present invention to provide a chamber pump system with an improved performance. SUMMARY OF THE INVENTION This object has been achieved by the chamber pump system according to claim 1 and the method for operating a chamber pump system according to the further independent claim. Further embodiments are indicated in the depending sub-claims. According to a first aspect, an electroactive chamber pump system is provided comprising: - at least one chamber pump device, comprising: o a deformable chamber membrane defining a pump chamber, o a dielectric elastomer transducer mechanically coupled with the chamber membrane to actuate the chamber membrane with the effect that the volume of the pump chamber is changed; - a control unit for periodically energizing the dielectric elastomer transducer to induce a reciprocating motion of the chamber membrane according to an actuation frequency, wherein the control unit is configured to set the actuation frequency depending on at least one of an operating pressure and a total electrical power consumption. In essence, such a chamber pump device is driven by an actuator which may be formed by the dielectric elastomer transducer which is biased by a biasing means such as a spring to support extension and / or contraction of the dielectric elastomer material. The chamber pump system may have a variable volume limited by the deformable chamber membrane (or diaphragm). The deformable chamber membrane may be coupled with the dielectric elastomer actuator directly or indirectly to deform the deformable membrane and thereby change the volume of the chamber. Conventionally, the chamber is further equipped with an inlet valve to draw / suck in gases, such as vacuum level gases (e.g. starting at atmospheric pressure and declining to vacuum level in a for instance vacuum chamber of a solvent degasser), and an outlet valve to push out gases (e.g. exhaust or inlet for another pump chamber). The dielectric elastomer transducer may be manufactured with a thin sheet-like elastomer material such as a film, with a thickness of between 20 and 200pm. The dielectric elastomer may be or may comprise materials such as dielectrics, e.g. natural rubber, acrylic, polyurethane, silicone or other elastomers. The dielectric elastomer material may be coated with electrically conductive soft electrodes on each side with a thickness of between 1 and 10 pm as known in the art. The so formed dielectric elastomer element corresponds to a flexible capacitor. The dielectric elastomer element can be used in an actuator by applying a voltage to the conductive electrodes which results in an extension along a surface direction of the elastomer sheet due to the incompressibility of the e.g. silicone elastomer film. It can also be used as a sensor to measure a deformation by external forces by detecting a change in capacitance. In contrast to conventional electromechanically driven chamber pump systems, electroactive chamber pump systems provided with dielectric elastomer transducers exhibit dynamic characteristics which cause a frequency dependency in operation. The dynamic characteristics result from the elastic properties of the dielectric elastomer material and a biasing means which may include a mass or a linear spring or any biasing elements with negative stiffness. Basically, the dynamic characteristics result in a frequency dependency (PT1 characteristics) of the behavior of such a dielectric elastomer-based chamber pump device. The frequency dependency may exploit the resonance frequency enabling an energy-efficient operation of the dielectric elastomer transducer. When operated close to or at the resonance frequency the pump device demonstrates a significantly increased membrane stroke. Therefore, the control unit may be configured to set the actuation frequency depending on the operating pressure so that the actuation frequency may be set on the mechanical resonance frequency of the at least one chamber pump device, wherein the actual mechanical resonance frequency is determined based on the actual operating pressure, particularly by means of a model or a function which associates the actual operating pressure to a mechanical resonance frequency. The actual operating pressure may be defined as the mean operating pressure over one cycle period of charging and discharging the dielectric elastomer transducer. It may be provided that a DC offset of the actuating voltage is applied on the actuation voltage to finetune the resonance frequency to equal the actuation frequency. It may be provided that the operating pressure corresponds to a pressure difference between an inlet pressure of the at least one chamber pump and an outlet pressure of the at least one chamber pump. Basically, the frequency characteristics show a variable displacement of the dielectric elastomer transducer and, consequently, of the chamber membrane depending on the actuation frequency (at equal actuation voltages). Moreover, it has been found that the actuation voltage amplitude for the dielectric elastomer transducer affects the maximum possible pressure difference as the compression factor changes. So, the actuation voltage amplitude also affects the flow rate, while the frequency characteristics remain relatively constant across different voltage amplitudes. The dielectric elastomer transducer can be employed as a sensor for the operating pressure. The charge difference between the fully discharged and the fully charged state of the dielectric elastomer transducer (or between two charging states which indicate the stroke end positions) can be used as a measure for the change of capacitance and as a measure of the total power consumption which depends on the operating pressure. The total power consumption of the dielectric elastomer transducer defines the power consumption of the dielectric pump device. As the total power consumption directly depends on the operating pressure which has an effect on the mechanical resonance frequency, the control can be made directly based on the total power consumption measured or indirectly by determining the operating pressure from the measured total power consumption or the measured charge difference. Furthermore, in static operation the chamber pump device may be operated at a well-defined compression ratio / factor, allowing that as the operating pressure the inlet pressure of the at least one chamber pump device can be used for the control. A power measuring unit may be provided to measure an indication of the total electrical power consumption of any of the at least one chamber pump, wherein the control unit is configured to determine the operating pressure as a function of the total electrical power consumption. Thereby, a feedback control can be established which allows adapting the actuation frequency according to the total power consumption so that the actuation frequency may be continuously adapted to the operating pressure (related to the total power consumption) at the inlet of the chamber pump system. Moreover, the control unit may be configured to implement a feedforward control which allows determining the actuation frequency depending on the total power consumption of the at least one pump device according to a given operating function. According to a further embodiment, a plurality of chamber pumps may be provided in a cascaded arrangement to provide an increased pressure difference when operating the pump devices. Particularly, the compression ratios / factors of the plurality of chamber pumps may be set to be equal at the same actuation frequency and equal for their same resonance frequencies, wherein the compression factor is defined as the maximum differential pressure of each chamber pump when operated with an actuation frequency at the resonance frequency. Due to the always equal compression ratios / factors of the pump devices the operating pressure corresponds to the pressure difference between the inlet pressure of the most upstream one of the plurality of chamber pumps and the outlet pressure most downstream one of the plurality of the plurality of chamber pumps. According to an embodiment, the control unit may be configured to operate at least two of the chamber pumps of the cascaded arrangement with the same actuation frequency in an anti-phase manner resulting in an anti-parallel motion of the deformable chamber membrane of the at least two of the chamber pumps with the effect that a chamber volume of one of the at least two chamber pumps decreases while the chamber volume of another one of the at least two chamber pumps increases and vice versa. This allows to significantly reduce noise generation resulting from the mechanical excitation (noise cancelling). According to an embodiment, the at least two of the chamber pumps of the cascaded arrangement may be arranged so that their actuation (stroke) directions are parallel to each other. The actuation direction is defined as the effective stroke path along which the dielectric elastomer transducer actuates the deformable chamber membrane. The control unit may be configured to operate at least two of the chamber pumps with the same actuation frequency in an anti-phase manner resulting in an anti-parallel motion of the deformable chamber membrane of the at least two of the chamber pumps. This allows to significantly reduce noise generation resulting from the mechanical excitation (noise cancelling). It may be provided that the electroactive dielectric elastomer transducer of each chamber pump device is coupled with or comprises a biasing means with specific configurable biasing characteristics, wherein the dielectric elastomer transducer is configured to act against a restoring force, wherein the chamber pump devices are configured by means of setting the biasing characteristics so that the chamber pump devices have identical mechanical resonance frequencies for identical compression factors / ratios. The control unit may be configured to supply an AC control voltage to periodically actuate the electroactive elastomer transducer of each of the at least one chamber pumps. Moreover, a recuperation unit may be included and coupled with the dielectric elastomer elements so that electrical energy, stored or generated after removing the electrical field at the dielectric elastomer transducer of one of the at least two of the chamber pump devices, is used to establish the electrical field for the dielectric elastomer transducer of another one of the at least two of the chamber pumps. A first of the at least two of the chamber pumps may have an inlet valve and a second of the at least two of the chamber pumps has an outlet valve, wherein the first and second chamber pump are interconnected with an interconnection line, wherein the interconnection line has exactly one intermediary valve to only allow gas transport from the first to the second valve. This configuration allows saving one valve as the intermediary valve acts as the outlet valve for the first pump device and as the inlet valve for the second pump device. According to an embodiment, a power measuring unit is provided to measure an indication of the total electrical power consumption of the at least one chamber pump, wherein the control unit is configured to determine the operating pressure as a function of the total electrical power consumption. Particularly, it may be provided that the power measuring unit comprises a mean current measuring unit to determine a mean current over one or more cycle times of charging and discharging the dielectric elastomer transducer as an indication of the total power consumption. The total power consumption equals to the product of supply voltage and the mean current over the one or more actuation cycle. The control unit may be configured to variably set the actuating voltage amplitude depending on a desired mass flow of the chamber pump. The actuation amplitude defines the stroke and so the compression factor. The actuation amplitude is selected according to a given target pressure difference and is constant in static operation. If the pressure increases the operation frequency may increase as well. According to a further aspect, a degasser for at least partially degassing a gascontaining liquid is provided, wherein the degasser comprises: a liquid accommodation volume for accommodating the gas-containing liquid during degassing; a negative pressure chamber containing a negative pressure regime compared to the liquid accommodation volume (or compared to atmospheric pressure); - a gas permeable membrane separating the liquid accommodation volume from the negative pressure chamber; the above chamber pump system configured to generate the negative pressure regime in the negative pressure chamber. According to a further aspect a method for operating at least one chamber pump device is provided, wherein the at least one chamber pump comprises a chamber pump housing, a chamber membrane cooperating with the chamber pump housing to form a pump chamber, and an electroactive dielectric elastomer transducer mechanically coupled with the chamber membrane to actuate the chamber membrane to change the volume of the pump chamber; the method comprising the steps of: - periodically energizing the electroactive elastomer transducer to induce a reciprocating motion of the chamber membrane according to an actuation frequency, setting the actuation frequency depending on at least one of an operating pressure and an electrical power consumption. According to a further aspect a chamber pump system comprising a plurality of chamber pumps is provided to respectively provide a pressure difference and a control unit for controlling operation of the plurality of chamber pumps, wherein the control unit is configured to operate each chamber pump at or in a range close to its resonance frequency, and to operate at least two of the chamber pumps in an anti-phase manner. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments are described in more detail in conjunction with the accompanying drawings, in which: Figures 1a and 1b schematically show cross-sectional views through a chamber pump device in different pumping states; Figure 2 shows a diagram for illustrating the dynamic behavior of the pump device with the dielectric elastomer transducer; Figure 3 shows a diagram for illustrating the stroke depending on a actuation frequency for different inlet pressures of an exemplary pump device; Figure 4 shows a diagram illustrating the mean current for operating the pump device which indicates total power consumption; and Figure 5 shows a schematic illustration of a chamber pump system with two serial pump devices; Figure 6 shows a schematic of the actuators for illustrating energy recuperation in the chamber pump system of Figure 5; Figure 7 shows a sample separation device with a degasser according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF EMBODIMENTS Figure 1 schematically shows a chamber pump device 1 as used in the chamber pump system according to the present invention. The pump device 1 is formed in a substrate 2 having a cavity 3 which has an inlet valve 4 in connection with an inlet opening 5 to the cavity 3 and an outlet valve 6 in connection with an outlet opening 7 of the cavity 3. The cavity 3 is partly covered or closed by a flexible membrane 8 or diaphragm which is deformable. The flexible membrane 8 forms a closed (apart from the openings 5, 7) chamber 9 together with the cavity 3. The membrane 8 can be moved so that the formed chamber 9 will variably change its inner volume. The membrane 8 is coupled with a dielectric elastomer transducer 10. The dielectric elastomer transducer 10 includes a mass 11 which may be moveable and directly connected with the membrane 8. The mass 11 is coupled via a dielectric elastomer element 13 with supports 14 which attach ends of the dielectric elastomer element 13 to the substrate 2 so that the dielectric elastomer element 13 is clamped and preferably biased between the mass 11 and the substrate 2. Herein, the dielectric elastomer element 13 acts as a actuator for effecting motion of the membrane and as a sensor for measuring a total power consumption. The arrangement of mass 11 and dielectric elastomer element 13 may be biased with a biasing member such as a spring member 12, or a further antagonist dielectric elastomer element or the like, which excites a force onto the mass 11 and thereby onto the membrane 8. As shown in Figure 1a, in non-energized state the forces applied by the dielectric elastomer element 13 and the biasing member 12 are in equilibrium and have a stroke position which hold the membrane 8 in a first state which corresponds to the maximum volume of the chamber 9 if not under pressure. The mass 11 can be regarded as a combination of all movable masses of the system including an extra (adjustable) mass element (indicated as 11) and the masses of the pumping membrane, interconnecting parts and the like. The same holds for the biasing member 12 which is regarded as all elements which excite a force onto the mass 11. As shown in Figure 1b, by applying an electrical voltage onto the dielectric elastomer element 13, an electrical field is established which compresses the dielectric elastomer material of the dielectric elastomer element 13 and causes an extension of the dielectric elastomer element 13 between the supports 14 and the mass 11. The deformation decreases the thickness of the dielectric elastomer element 13 and increases its length so that the mass 11 is released. The spring force then pushes the mass 11 and the membrane 8 more into the cavity 3 thereby reducing the inner volume of the chamber 9. This forces the gas in the chamber 9 through the outlet opening 7 and through the outlet valve 6. If actuation of the dielectric elastomer transducer 10 is stopped the dielectric elastomer element 13 contracts and pulls the mass 11 so that the inner volume of the chamber 9 is increased. Thereby, a negative pressure is established in the chamber 9 resulting in the inflow of gas through the inlet valve 4 and the inlet opening 5. The pump device 1 is controlled by a control unit 15 which drives the dielectric elastomer element 13 with an AC actuation voltage so that a reciprocate pump action is obtained. Waveform of the AC actuation voltage may be a squared sinusoidal or the like. The control unit 15 is configured to variably set the actuation voltage amplitude and the actuation frequency of the actuation voltage. Furthermore, the control unit 15 includes or is connected with a current sensor to obtain a current flowing through the dielectric elastomer transducer 13 during operation. The dielectric elastomer transducer 10 forms a dynamic system with the biasing member 12 and the mass 11 the performance of which has a frequency dependency which is exemplarily shown in the diagram of Figure 2 for an exemplary pump device 1. The performance can be seen in the increase of the stroke length close to the resonance frequency. Further in Figure 3, it can be seen the dependency of the stroke over actuation frequency given a constant actuation amplitude for different (corresponding to compression factor / ratio) depends on the actuation frequency. The resonance are shown by the stroke maximum and are merely depending on system stiffness and masses. However, more or less independent of the actuating voltage amplitude, resonance frequency is relatively stable. A DC offset of the actuating voltage can be applied on the actuation voltage to slightly manipulate the resonance frequency, e.g. for fine-tuning. Moreover, the flow rate can be adjusted by means of varying the actuating voltage amplitude when the actuation frequency is at the resonance frequency. The selection of the actuating voltage amplitude and the actuation frequency can be made in a feedforward or feedback control implemented in the control unit 15. The feedback-control for setting the actuation frequency may be implemented as a model-based control which uses the total power consumption to determine the operating pressure, wherein the actuation frequency is controlled to correspond to the resonance frequency. The resonance frequency is determined by a model which determines the resonance frequency based on the total power consumption or based on the actual operating pressure. Basically, in one mode of operation, the inlet pressure can be obtained, i.e. by a pressure sensor, and the actuation frequency is selected accordingly. Furthermore, a feedback control can be established which controls the actuation frequency according to the inlet pressure of the pump device 1. The desired inlet pressure is predetermined and defines a fixed compression factor / ratio to be achieved in static operation. In another mode of operation, the pump device 1 may be controlled via an operation profile where the negative pressure is built up with varying actuating frequencies. The actuating frequency and the actuation voltage amplitude may follow a ramp characteristics having a lower frequency at the start of the pump system in combination a higher stroke (higher actuation voltage amplitude) and continuously shifting to a higher actuation frequency and a lower actuation voltage amplitude when closer to the desired negative pressure level. Furthermore, in an operation mode, the actuation frequency is controlled to equal the actual resonance frequency. The actual resonance frequency may be determined by means of a given model which is provided / configured to determine the resonance frequency depending on a determined operation pressure which may be determined based on a total power consumption. An indication of the total power consumption can be measured as the mean current for operating the pump device 1 over one charging and / or one discharging cycle (current integral over one charging and / or one discharging cycle. In a start-up phase the mean current may have a characteristics as shown in Figure 4. It can be seen that the mean current decreases over time which indicates that the pressure difference is increasing or the inlet pressure is decreasing when the actuation frequency is continuously adapted onto the resonance frequency. In Figure 5, a chamber pump system 20 is shown which has a series (cascaded) connection of a first and a second pump device T, 1”, both being controlled by a common control unit 15 and being operated at the same actuation frequency depending on the operating pressure as the pressure difference between the inlet pressure of the of the first chamber pump device 1* and the outlet pressure of the second chamber pump device 1”. To increase efficiency and to reduce noise generation, the two pump devices T, 1” are arranged in parallel with respect to their stroke directions and operated in an anti-phase manner so that the motions of the dielectric elastomer transducers 10 are anti-parallel to each other. This allows to significantly reduce noise generation by destructive interference. Basically, the first pump device T ejects gas from the chamber 9 through the outlet port to directly enter the chamber 9 of the second pump device 1” through the inlet port. As the outlet valve of the first pump device T and the inlet valve of the second pump device 1” have the same function they can be replaced by exact one single intermediate valve. Figure 6 shows a schematic of the circuitry of the dielectric elastomer elements 13 used for energy recuperation in resonance operation in the above described chamber pump system 20. As described the dielectric elastomer elements 13 are operated in synchronicity with a phase shift of 180°, i.e. one of the dielectric elastomer elements 13 is charged while the other one of the dielectric elastomer elements 13 is discharged a two step approach may be made. Each of the dielectric elastomer elements 13 is driven by a semiconductor switch Si and S2 (such as a MOSFET or the like), respectively, which are in series with the dielectric elastomer elements 13 indicated as capacity, which is the electronic equivalent of the dielectric elastomer elements 13. The serial branches are each connected with a supply voltage HV1, HV2, which may be equal. The intermediate nodes of the serial branches are interconnected with a recharging switch S4 (such as a MOSFET or the like). Due to the anti-phase operation of the dielectric elastomer elements 13 one of the dielectric elastomer elements 13 is discharged (from a fully charged state) while the other one of the dielectric elastomer elements 13 is charged (from a fully discharged state). Starting with a state where the semiconductor switch Si of the one dielectric elastomer element 13 is closed and the semiconductor switch S2 of the other dielectric elastomer element 13 is open. A recharging is made by opening the semiconductor switch S1 of the one dielectric elastomer element 13 and closing the recharging switch S4. Then the charges of the one dielectric elastomer element 13 flow into the other dielectric elastomer element 13 until a voltage equilibrium or voltage balance is achieved. Then, the recharging switch S4 is opened and the semiconductor switch S2 of the other dielectric elastomer element 13 is closed to fully charge the other dielectric elastomer element 13. At the same time the one dielectric elastomer element 13 may be fully discharged, e.g. by means of an extra discharging semiconductor switch (not shown). Such an electroactive pump system 20 may be applied with a degasser e.g. of a HPLC system for at least partially degassing a gas-containing liquid. Such a degasser comprises a liquid accommodation volume for accommodating the gas-containing liquid during degassing, a negative pressure chamber containing a negative pressure regime compared to the liquid accommodation volume (or compared to atmospheric pressure) and a gas permeable membrane separating the liquid accommodation volume from the negative pressure chamber. The above chamber pump system can be used to generate the negative pressure regime in the negative pressure chamber. Figure 7 shows a sample separation device 80 with a degasser of an HPLC system according to an exemplary use case of the above pump system 128. Such an HPLC system may be used for liquid chromatography, for example. A drive system 21 which is supplied with solvents from a supply unit with a liquid reservoir 25 drives a mobile phase (that is a liquid) through a sample separation unit 30 (such as a chromatographic column) which includes a stationary phase. A degasser 27 may degas the solvents before these are supplied to the drive system 21. A sample insertion or injection unit 40 with a fluidic switching valve 95 is arranged between the drive system 21 and the sample separation unit 30, to introduce a sample liquid in the fluidic separation path. The stationary phase of the sample separation unit 30 is provided for separating the components of the fluidic sample. A detector 50 which comprises a flow cell detects the separated components of the sample, and a fractionator may be provided to output the separated components of the sample in containers which are provided for this purpose. Liquids which are not required anymore may be output in a drain container 60. A control unit 70 controls the single components 20, 30, 40, 50, 60, 95 of the sample separation device 100. The degasser 27 contains a degasser chamber 100 with a degasser volume 102 which is delimited therein. In this degasser volume 102 of the degasser chamber 100, a degassing membrane 104 is accommodated defining a liquid accommodation volume for accommodating the gas-containing liquid during degassing. The degassing gas permeable membrane 104 may be arranged between a liquid phase supply 106 for supplying a liquid phase to be degassed and a liquid phase discharge 108 for discharging the degassed liquid phase. For example, the mobile phase supply 106 may be a hose which delivers the mobile phase from the liquid reservoir 25 to the degassing gas permeable membrane 104. For example, the degassing membrane 104 may be configured as a semi-permeable hose portion which is connected to the hose of the liquid phase supply 106. The liquid phase discharge 108 may also be a hose which delivers the degassed liquid phase from the degassing gas permeable membrane 104 to the drive system 21. At the degassing gas permeable membrane 104, the gas which is to be removed from the liquid phase may pass through the degassing gas permeable membrane 104 into the degasser volume 102. Figure 7 further shows a suction unit 116 which is connected to the degasser volume 102 via a fluid conduit with the pump system 128 which is configured as a suction system or a vacuum pump. The latter sucks the gas which passed through the degassing gas permeable membrane 104 from the degasser volume 102 and the vapor which is present in the degasser volume 102 with the lower partial pressure. This leads to effectively degassing the liquid phase in the degasser 27.

Claims

1. A chamber pump system comprising:- at least one chamber pump, comprisingo a deformable chamber membrane defining a pump chamber,o an electroactive elastomer transducer mechanically coupled with the chamber membrane to actuate the chamber membrane to change the volume of the pump chamber;- a control unit for periodically energizing the electroactive elastomer transducer to induce a reciprocating motion of the chamber membrane according to an actuation frequency,wherein the control unit is configured to set the actuation frequency depending on at least one of an operating pressure and a total electrical power consumption.

2. The chamber pump system according to claim 1, wherein the control unit is configured to set the actuation frequency depending on the operating pressure so that the actuation frequency is set on the actual mechanical resonance frequency of the at least one chamber pump, wherein the actual mechanical resonance frequency is determined based on the actual operating pressure, particularly by means of a model which associates the actual operating pressure to a mechanical resonance frequency.

3. The chamber pump system according to claim 2, wherein a DC offset of the actuating voltage is applied on the actuation voltage to finetune the resonance frequency to equal the actuation frequency.

4. The chamber pump system according to any of the claims 1 to 3, wherein the operating pressure corresponds to a pressure difference between an inlet pressure of the at least one chamber pump and an outlet pressure of the at least one chamber pump.

5. The chamber pump system according to any of the claims 1 to 4, wherein a plurality of chamber pumps are provided in a cascaded arrangement.

6. The chamber pump system according to claim 5, wherein the compression factors / ratios of the plurality of chamber pumps are set to be equal, wherein the compression factor / ratio is defined as the maximum differential pressure of each chamber pump when operated with an actuation frequency at the resonance frequency.

7. The chamber pump system according to claim 5 or 6, wherein the operating pressure corresponds to the pressure difference between the inlet pressure of the most upstream one of the plurality of chamber pumps and the outlet pressure of the most downstream one of the plurality of the plurality of chamber pumps.

8. The chamber pump system according to any of the claims 5 to 7, wherein the electroactive elastomer transducer of each chamber pump is coupled with a biasing means with specific biasing characteristics, wherein the electroactive elastomer transducer is configured to act against a restoring force, wherein the chamber pumps are configured by means of setting the biasing characteristics force to have identical mechanical resonance frequencies for identical compression factors / ratios.

9. The chamber pump system according to any of the claims 5 to 8, wherein the control unit is configured to operate at least two of the chamber pumps with the same actuation frequency in an anti-phase manner resulting in an anti-parallel motion of the deformable chamber membrane of the at least two of the chamber pumps so that a volume of the pump chamber of one of the at least two chamber pumps decreases while the volume of the pump chamber of another one of the at least two chamber pumps increases.

10. The chamber pump system according to any of the claims 5 to 9, wherein the at least two of the chamber pumps are arranged so that their actuation directions are parallel to each other, wherein the actuation direction is defined as the effective translatory path along which the dielectric elastomer transducer actuates the deformable chamber membrane,wherein the control unit is configured to operate at least two of the chamber pumps with the same actuation frequency in an anti-phase manner so that the deformable chamber membrane of the at least two of the chamber pumps have an anti-parallel motion.

11. The chamber pump system according to claim 9 or 10, wherein a recuperation unit is provided so that electrical energy generated after removing the electrical field at one of the at least two of the chamber pumps is sued to generate the electrical field for another one of the at least two of the chamber pumps.

12. The chamber pump system according to any of the claims 5 to 11, wherein a first of the at least two of the chamber pumps has an inlet valve and a second of the at least two of the chamber pumps has an outlet valve, wherein the first and second chamber pump are interconnected with an interconnection line, wherein the interconnection line has exactly one intermediary valve to only allow fluid transport from the first to the second valve.

13. The chamber pump system according to any of the claims 1 to 12, wherein a power measuring unit is provided to measure an indication of the total electrical power consumption of the at least one chamber pump, wherein the control unit is configured to determine the operating pressure as a function of the total electrical power consumption.

14. The chamber pump system according to claim 13, wherein the power measuring unit comprises a mean current measuring unit to determine a mean current over the cycle time of charging and discharging the dielectric elastomer transducer as an indication of the total power consumption.

15. The chamber pump system according to any of the claims 1 to 14, wherein the control unit is configured to supply an AC control voltage to periodically actuate the electroactive elastomer transducer of each of the at least one chamber pumps, wherein the control unit is configured to variably set the voltage amplitude depending on a desired mass flow of the chamber pump.

16. Degasser for at least partially degassing a gas-containing liquid, wherein the degasser comprises:- a liquid accommodation volume for accommodating the gas-containing liquid during degassing;a negative pressure chamber containing a negative pressure regime compared to the liquid accommodation volume;a gas permeable membrane separating the liquid accommodation volume from the negative pressure chamber;- a chamber pump system according to any of the claims 1 to 15 configured to generate the negative pressure regime in the negative pressure chamber.

17. Method for operating at least one chamber pump, wherein the at least one chamber pump comprises a chamber pump housing, a chamber membrane cooperating with the chamber pump housing to form a pump chamber, and an electroactive elastomer transducer mechanically coupled with the chamber membrane to actuate the chamber membrane to change the volume of the pump chamber; the method comprising the steps of:periodically energizing the electroactive elastomer transducer to induce a reciprocating motion of the chamber membrane according to an actuation frequency,- setting the actuation frequency depending on at least one of an operating pressure and an electrical power consumption.

18. A chamber pump system comprising a plurality of chamber pumps to respectively provide a pressure difference and a control unit for controlling operation of the plurality of chamber pumps, wherein the control unit is configured to operate each chamber pump at or in a range close to its resonance frequency, and to operate at least two of the chamber pumps in an anti-phase manner.

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