Method for adjusting a piezoelectric actuator

Abstract

The invention relates to a method for adjusting a piezoelectric actuator (5) of a dispensing system (1), wherein the method comprises the following steps: emitting at least one excitation signal to the actuator (5) and determining at least one impedance value of the excited actuator (5), the piezoelectric actuator (5) being adjusted according to the determined at least one impedance value.

Description

[0001] Method for adjusting a piezoelectric actuator

[0002] The invention relates to a method for adjusting a piezoelectric actuator, a dispensing device, a data processing unit for carrying out the method, a computer program, a computer-readable data carrier and a data carrier signal.

[0003] Isolated cells are becoming an increasingly important material. Drugs such as monoclonal antibodies and other proteins are produced using so-called monoclonal cell lines. These are populations of cells that all originate from a single parent cell. The creation of monoclonal cell lines is necessary because it is the only way to ensure that all cells in the population have a nearly identical genome, thus producing drugs of consistent and reproducible quality.

[0004] To generate a monoclonal cell line, cells are transferred individually into microtiter plate containers. The cells to be transferred are produced by genetically modifying a host cell line and separating these modified cells. The deposition of individual cells into the microtiter plates is done using devices called dispensing devices.

[0005] Dispensing devices are known, each comprising a dispenser containing a liquid sample. The dispenser is designed such that liquid sample, e.g., in the form of a drop, is only dispensed after a dispensing section is actuated. The dispensing section is actuated by a piston of the dispensing device, which is actuated by a piezoelectric actuator of the dispensing device. Thus, the piston presses against the dispensing section when the piston is actuated by the piezoelectric element. The drop velocity, drop volume, and drop shape depend on the piston speed and the penetration depth of the piston into the dispensing section. The penetration depth of the piston into the dispensing area can be between 5 and 10 gm (micrometers).

[0006] Users of the dispensing device require that the liquid samples ejected during the dispensing processes be comparable and / or stable, particularly with regard to their velocity and / or shape and / or volume. In other words, it is desired that liquid samples with the same physical properties can be dispensed repeatedly. Thus, there is a need for the ejected liquid samples to have substantially the same velocity and / or shape and / or volume.

[0007] However, this requirement is not easy to meet. For example, the tolerances during the manufacturing of the aforementioned components are typically greater than 5 to 10 μm of the penetration depth. Furthermore, the tolerances can change during operation of the dispensing device. This occurs, for example, when the dispenser is replaced with another dispenser. A dispenser replacement may be necessary if a different liquid sample is to be dispensed after a dispensing process to avoid contamination of the liquid samples. Furthermore, it may be necessary to replace the piston and / or the piezoelectric actuator during maintenance and / or repair of the dispensing device.

[0008] The aforementioned tolerances make it difficult to install the piezoelectric actuator with such precision that the piezoelectric actuator is preloaded with a specified voltage. Preloading the piezoelectric actuator is necessary to avoid actuator damage and to dispense the liquid sample with the specified physical properties. As a result, with existing dispensing devices, the voltage at which the piezoelectric actuator is preloaded is unknown. Since the penetration depth and / or piston speed depend on the actuator preload, liquid samples often cannot be repeatedly ejected with the same physical properties, resulting in ejected liquid samples that are not comparable and / or stable. In particular, the ejected liquid samples often have different velocities and / or different shapes and / or different volumes.

[0009] To avoid these disadvantages, the actuator in known dispensing devices is manually adjusted. In particular, attempts are being made to find a setting for the piezoelectric actuator that avoids the aforementioned disadvantages. However, manual adjustment is inaccurate and time-consuming.

[0010] The object of the invention is to provide a method by means of which the piezoelectric actuator can be adjusted precisely and quickly.

[0011] The object is achieved by a method for adjusting a piezoelectric actuator of a dispensing device, the method comprising the following steps: transmitting at least one excitation signal to the actuator and determining at least one impedance value of the excited actuator, the piezoelectric actuator being adjusted depending on the determined at least one impedance value.

[0012] Another object of the invention is to provide a dispensing device in which the actuator can be adjusted accurately and quickly.

[0013] The object is achieved by a dispensing device comprising a dispenser for dispensing liquid sample, a piezoelectric actuator, and a data processing device configured to output at least one excitation signal to the actuator and to determine at least one impedance value of the excited actuator, wherein the data processing device is configured to adjust the actuator depending on the determined at least one impedance value.

[0014] According to the invention, it was recognized that by taking the impedance into account when adjusting the actuator, repeatable and / or stable and / or comparable ejected liquid samples can be achieved. In particular, the dispensed liquid samples can have essentially the same speed and / or the same shape and / or the same volume. Focusing on the impedance is advantageous because the tolerances of the components of the dispensing devices influence the impedance. Thus, adjusting the piezoelectric actuator, in particular based on the determined impedance of the actuator, offers the advantage that the tolerances are taken into account when adjusting the piezoelectric actuator. In this respect, even a dispenser change has no influence on the repeatability and / or comparability of the dispensed liquid samples.Furthermore, with the inventive design, it is no longer necessary for the piezoelectric actuator to be mechanically preloaded to a precise voltage. As explained in detail below, a voltage can be determined within the scope of the inventive method by which the piezoelectric actuator is to be preloaded. With the inventive method, there is therefore no longer any need to find an optimal preload through manual testing. Therefore, the piezoelectric actuator can be adjusted quickly and precisely using the method.

[0015] For the purposes of the invention, a dispensing device is understood to be a device by means of which one or more liquid samples are dispensed only after the dispenser has been actuated. The dispenser can be actuated directly or indirectly by the actuator. The dispensing device can have a piston that is actuated by the actuator when the actuator receives an excitation signal. The dispenser is configured such that the liquid sample contained in the dispenser cannot be dispensed without actuation by the piston or actuator. A predetermined volume, which can contain a predetermined number of particles, can be dispensed by means of the dispensing device, in particular by appropriate actuation by the piston. The above-mentioned features distinguish a dispensing device from a flow cytometer, in which a predetermined dispensing of liquid samples cannot occur by actuating a piston or actuator.

[0016] The liquid sample dispensed by the dispensing device, in particular the dispenser, can be a drop, in particular a free-floating drop. The liquid drop can have a volume in a range between 1 fl (femtoliter) and 1 L (microliter), in particular between 1 pl (picoliter) and 1 pL (microliter). The sample dispensing can be carried out according to a drop-on-demand mode. In this mode, the device dispenses a discrete rather than a continuous sample. Alternatively, the dispensed liquid sample can be a jet that, after being dispensed from the dispenser, may break up into individual liquid droplets.

[0017] The liquid sample dispensed from the dispensing device may contain liquid and no particles during dispensing operation, i.e., in operation where the piezoelectric actuator is already adjusted. Alternatively, the dispensed liquid sample may contain liquid and a single particle. Furthermore, the dispensed liquid sample may contain liquid and more than one particle.

[0018] The particles can be biological particles, where the biological particles can be microorganisms, such as bacteria, archaeans, yeasts, fungi, and viruses, or cells, DNA, RNA, or proteins. The liquid sample can contain a single or multiple biological particles of the aforementioned type. The liquid can be a suspension, which can promote growth of the biological particles arranged in the liquid. Alternatively, the particle can be a glass or polymer bead, particularly one that has the same or substantially the same volume as a cell.

[0019] The piezoelectric actuator can be designed in a stacked form. In this case, the piezoelectric actuator has several, in particular piezoceramic, elements. The individual elements are connected to one another. In an alternative design, the piezoelectric actuator can also have only a single, in particular piezoceramic, element. Regardless of the design of the actuator, the element can have any shape. For example, the element can be polygonal, disc-shaped, or tubular. The piezoelectric actuator also has electrodes for applying an electric field to the elements or the element. The actuator and thus the elements can be mechanically prestressed by a prestressing device. Prestressing is understood to mean a compressive force exerted on the elements by the prestressing device, by means of which the elements are pressed together.

[0020] The excitation signal is a signal applied to the piezoelectric actuator to deflect the actuator. In a dispensing device that additionally includes the piston, a deflection of the actuator also causes a deflection of the piston. After actuation by the actuator, the piston can move, in particular only, linearly. As described in more detail below, the excitation signal applied to the actuator in an adjustment mode for adjusting the piezoelectric actuator differs from an excitation signal applied to the actuator in a dispensing mode for dispensing a liquid sample.

[0021] The determined impedance value is an impedance value of the piezoelectric actuator. It was recognized that the impedance value depends on the bias voltage applied to the actuator. In this case, the dispenser and the bias device influence the impedance value because the bias voltage is adjusted via the bias device and the dispenser as a counter-tension element. In the case where the dispensing device has a piston, the piston also influences the impedance value. It is clear that several impedance values ​​can be determined using the method, which depend on the frequency of the excitation signal.

[0022] In a particular embodiment, the excitation signal can be a voltage signal, in particular a sinusoidal one. The excitation signal can lie within a frequency range. The frequency range can be selected such that it includes the resonance frequency of the actuator. Furthermore, the excitation signal can be varied over time. In particular, the excitation signal can be a sweep signal. Thus, multiple impedance values ​​can be obtained with one excitation signal. Alternatively or additionally, multiple excitation signals can be sent to the actuator. The individual excitation signals can each have a sinusoidal waveform. Furthermore, the excitation signals can differ from one another in frequency. The excitation signals can lie within the previously mentioned predetermined frequency range. The excitation signals can each be a voltage signal.This allows different excitation signals to be applied to the actuator, each with a different frequency. In particular, voltages can be applied to the actuator with a different frequency.

[0023] The excitation signal applied to the actuator during adjustment mode may differ from the excitation signal applied to the actuator during dispensing mode. For example, the amplitude of the excitation signal applied during adjustment mode may be smaller than the amplitude of the excitation signal applied during dispensing mode. The amplitude of the excitation signal may be so small that the actuator deflection is insufficient to eject a liquid sample from the dispenser. Selecting such an excitation signal during adjustment mode offers the advantage of preventing damage to the impedance measuring device and / or data processing equipment.

[0024] The at least one impedance value resulting from the transmission of the excitation signal having a frequency within the frequency range can be assigned to a mechanical bias voltage. When multiple excitation signals are transmitted, the resulting impedance values ​​can each be assigned to a mechanical bias voltage. This is possible because the mechanical bias voltage of the actuator was not changed during the impedance determination. As a result, one or more impedance values ​​can be assigned to a mechanical bias voltage setting. This is utilized, as described in more detail below, in the dispensing operation to generate comparable dispensed liquid samples.

[0025] The data received by the data processing device may already contain information about the impedance. In particular, the data may represent at least one impedance value. In this case, the impedance is determined outside the data processing device. Alternatively or additionally, the at least one impedance value may be determined by the data processing device based on the received data. The impedance value may be determined based on the voltage applied to the actuator and a resistor connected by the actuator or in series with the actuator. Both values ​​are determined by exciting the actuator with an alternating voltage at a specific frequency. In order to obtain the entire impedance spectrum, i.e., multiple impedance values, multiple impedance measurements must be performed at different excitation frequencies.

[0026] The actuator can be prestressed during a determination process of the at least one impedance value. In particular, the at least one impedance value can be determined when the actuator is prestressed. For this purpose, the dispensing device has a prestressing device that exerts a mechanical prestress on the actuator. The actuator can be tensioned against the dispenser. The dispensing device can have the piston. The piston can be arranged in the force flow between the actuator and the dispenser. In the prestressed state, the actuator is in direct contact with the dispenser or with the piston. The piston is in contact with the dispenser. In an embodiment of the dispensing device without a piston, the actuator is in contact with the dispenser in the prestressed state. The determination process includes emitting the at least one excitation signal and determining the at least one impedance value.

[0027] Such a design allows all tolerances of the aforementioned components to be taken into account when determining the at least one impedance value and to be reflected in the impedance values. This allows the tolerances to be considered when adjusting the piezoelectric actuator. For the sake of completeness, it should be noted that tolerances of components other than those mentioned above of the dispensing device can also be considered when adjusting the actuator if they influence the mechanical preload and thus the impedance of the actuator.

[0028] The at least one impedance value can be determined in the setting mode of the dispensing device. In the setting mode, the actuator is set and / or the values ​​required for setting the actuator are determined. As already described above, the amplitude of the excitation signal can be smaller in the setting mode than the amplitude of the excitation signal in the dispensing mode of the dispensing device. The "setting mode" of an actuator is thus understood to be an operating state of the dispensing device in which the actuator is set such that repeatable and / or stable and / or comparable liquid samples can be dispensed in the dispensing mode. In contrast, the "dispensing mode" of the actuator is an operating state in which the actuator is operated with the at least one parameter determined in the setting mode, in particular the mechanical preload and / or the excitation signal.In the dispensing mode of the dispensing device, the amplitude of the excitation signal is sufficiently high that the piston or actuator penetrates far enough into the dispensing section to dispense liquid sample.

[0029] The adjustment operation can be performed prior to the dispensing operation. This offers the advantage that the liquid samples dispensed during the dispensing operation are comparable, particularly with regard to shape, volume, and speed. The adjustment operation can be performed after a dispenser change and / or an actuator replacement and / or after a specified number of dispensing steps, each of which dispenses a liquid sample. The adjustment operation is performed after a specified number of dispensing steps to check whether the dispensing device is still functioning as intended.

[0030] In a particular embodiment, the data processing device can determine at least one reference impedance value. In particular, multiple reference impedance values ​​can be determined. To determine the at least one reference impedance value, multiple dispensing processes can be performed. Each of the dispensing processes can comprise one or more dispensing steps, in each of which a liquid sample is dispensed. The individual dispensing processes differ in the mechanical preload applied to the actuator. However, the dispensing steps within the dispensing process are carried out with the same preload.

[0031] A physical property of the dispensing device and / or the liquid sample dispensed during a dispensing process is determined. The data processing device can check whether the physical property meets a specified condition. The specified condition is met if the physical property of a dispensed liquid sample corresponds to a specified physical property. "Corresponds" also includes the case where the determined physical property does not exactly correspond to the specified physical property, but lies within a specified tolerance range. The physical property can be determined for all liquid samples of a dispensing process. This can be repeated for each dispensing process. The determination of the physical property can be performed manually or automatically.A physical property is considered any property of the dispensed liquid sample that can be measured and / or determined based on measurements. For example, the property can be an optical property of the liquid sample and / or the shape of the dispensed liquid sample. Alternatively or additionally, the property of the liquid sample can be the volume of the liquid sample and / or the velocity of the liquid sample. Furthermore, the property can be the number of drops dispensed following an excitation signal and / or whether each excitation signal also results in a dispensing of a liquid sample.

[0032] If a dispensing process can be determined in which the dispensed liquid sample(s) exhibit a predetermined property, an impedance measurement can be performed and at least one reference impedance value can be determined. In other words, at least one reference impedance value can be determined, wherein the actuator is biased during the impedance measurement with the bias voltage applied during the dispensing process, in which the physical property of the liquid sample and / or the dispensing device corresponds to the predetermined physical property.

[0033] The dispensing device may comprise an optical detection device for optically detecting the dispensed liquid sample. The physical property of the liquid sample can be determined based on the detected liquid sample. The optical detection device may comprise an imaging device for generating an image.

[0034] The at least one reference impedance value is determined analogously to the at least one impedance value. This means that at least one excitation signal or multiple excitation signals are transmitted to the actuator, wherein the excitation signal amplitude is frequency-dependent or the excitation signals have a different frequency. The data processing device determines the impedance of the excited actuator. For further details, reference is made to the above explanations. The at least one specific reference impedance value can be stored in an electrical memory of the dispensing device.

[0035] The data processing device can check whether at least one setting condition is met. The setting condition can depend on the at least one reference impedance value and / or on the at least one impedance value. Alternatively or additionally, the setting condition can also depend on a further impedance value, which is described in detail below. The data processing device can then adjust the actuator depending on the test result.

[0036] The actuator can be adjusted by changing the mechanical preload applied to the actuator. The dispensing device can comprise a preload device for preloading the piezoelectric actuator. The preload device can comprise a motor by means of which a preload element, such as a screw, is moved to change the preload applied to the actuator. Alternatively or additionally, the excitation signal sent to the data processing device can be changed. This allows an amplitude of the control signal to be changed. As a result, the actuator can be adjusted quickly and easily.

[0037] Adjusting the actuator via the mechanical preload has the advantage that the impedance value can be used as a controlled variable in a closed-loop control system. In this case, several determination processes can be performed during the adjustment operation, in which at least one impedance value or several impedance values ​​are determined. The determination processes differ from one another in the mechanical preload applied to the actuator.

[0038] In contrast, changing the control signal has no influence on the impedance, so control with impedance as the controlled variable in adjustment mode is not practical. However, the excitation signal, in particular the amplitude of the excitation signal, can be changed in dispensing mode depending on the test result in order to adjust the actuator. For this purpose, a relationship can be stored between the excitation signal applied in dispensing mode and the test result. This way, it is known which excitation signal should be applied to the actuator in dispensing mode if, for example, a certain impedance value differs from a reference impedance value. The relationship between the excitation signal in dispensing mode and the test result can be determined in a laboratory, especially once.

[0039] The test result can, for example, be the deviation of the determined impedance value from the reference impedance value. Further test results that can be used to determine the excitation signal are listed below. The determination of the at least one reference impedance value can be part of the setting operation. The reference impedance values ​​can be determined once, particularly in a laboratory, and used for all dispensing devices. Alternatively or additionally, it is possible to determine the reference impedance values ​​before commissioning the dispensing device and / or before dispensing operation. Furthermore, it is possible to determine the reference impedance values ​​at predetermined times and / or after maintenance of the dispensing device, particularly after replacing the actuator.

[0040] For the purposes of the invention, reference impedance values ​​are understood to be impedance values ​​that result when the actuator is in an ideal state. In this ideal state, the actuator is adjusted such that liquid samples are repeatedly dispensed with the same physical properties.

[0041] In a special embodiment, to adjust the piezoelectric actuator, the data processing device can check whether the determined impedance value corresponds to the reference impedance value or lies within a predetermined range that includes the impedance value. In doing so, it can be checked whether multiple impedance values ​​correspond to the respectively assigned reference impedance values ​​or lie within the predetermined range. The two values ​​are associated with each other if an impedance value associated with a frequency of the excitation signal corresponds to a reference impedance value or lies within the predetermined range associated with the same frequency of the excitation signal. The tolerances of the components of the dispensing device have no negative impact on the dispensing process if the actuator is adjusted such that the determined impedance values ​​correspond to the reference impedance values ​​or lie within the predetermined range.

[0042] The actuator can be adjusted such that the determined impedance value corresponds to the reference impedance value or lies within the specified range that includes the reference impedance value. As described above, this can be achieved by changing the preload on the actuator. Within the framework of a closed-loop control, the mechanical preload can be changed until the above adjustment condition is met. The actuator can be adjusted by the data processing device.

[0043] Alternatively or additionally, a deviation between the determined impedance value and the

[0044] The reference impedance value can be taken into account in an excitation signal during dispensing operation of the dispensing device. This allows the amplitude of the excitation signal during dispensing operation to be selected accordingly to compensate for the deviation determined during adjustment operation. As a result, comparable liquid samples can also be obtained in this way during dispensing operation. The excitation signals applied to the actuator during dispensing operation, which depend on the deviation, can be stored in a memory.

[0045] In another embodiment, the actuator can be adjusted as follows. This procedure can be performed in addition to or as an alternative to the procedure described above. The following analysis of the reference impedance values ​​can be performed by the data processing device.

[0046] During setup, a reference impedance value and / or a reference frequency value can be determined for a reference impedance point. A reference impedance point is a point assigned a reference impedance value and a reference frequency value. Reference impedance values ​​and / or reference frequency values ​​can be determined for multiple reference impedance points. The reference impedance point can be a resonance point or an anti-resonance point. A resonance point has an impedance value that is a local impedance minimum, and the anti-resonance point has an impedance value that is a local impedance maximum. As a result, after examining the determined reference impedance values, all reference impedance values ​​and / or reference frequencies of characteristic reference impedance points, such as resonance points and / or anti-resonance points, are known.

[0047] Furthermore, a reference frequency difference between two reference impedance points can be determined. Thus, at least one reference frequency range between resonance points or between anti-resonance points can be determined. Alternatively or additionally, a reference frequency difference between a resonance point and an anti-resonance point can be determined. Furthermore, a number of reference impedance points, in particular a number of resonance points and / or a number of anti-resonance points, can be determined in a reference frequency range.

[0048] The data processing device can check, as a setting condition, whether a specific impedance point, such as a resonance point or anti-resonance point, corresponds to the reference impedance point, such as the reference resonance point or the anti-reference resonance point, or lies within a predetermined range that includes the impedance point. In particular, it can be checked whether the impedance value of the impedance point corresponds to the reference impedance value of the reference impedance point or lies within a predetermined range that includes the reference impedance value, and / or whether the frequency value of the impedance point corresponds to the reference frequency value of the reference impedance point or lies within a predetermined range that includes the reference frequency value. An impedance point is a point to which an impedance value and a frequency value are assigned.

[0049] In addition, as a setting condition, it can be checked whether a frequency difference exists between two impedance points that corresponds to the reference frequency difference or lies within a specified range that includes the reference frequency difference. Furthermore, as a setting condition, it can be checked whether a number of impedance points exist in a frequency range that corresponds to the number of reference impedance points in the reference frequency range. In this case, it can be checked whether the frequency range corresponds to the reference frequency range or is shifted by a specified range relative to the reference frequency range.

[0050] Compared to the previously described method, the aforementioned adjustment conditions offer the advantage that not every impedance value is used to adjust the actuator, but only specific frequency ranges and / or impedance points. This allows for quick adjustment of the actuator.

[0051] The data processing device adjusts the actuator depending on the test result. The actuator can be adjusted such that the measured impedance value of the impedance point corresponds to the reference impedance value of the reference impedance point or lies within a predefined range that includes the reference impedance value. Alternatively or additionally, the actuator can be adjusted such that the frequency value of the impedance point corresponds to the reference frequency value of the reference impedance point or lies within a predefined range that includes the reference frequency value. Furthermore, the data processing device can adjust the actuator such that the frequency difference between two impedance points corresponds to the reference frequency difference or lies within a predefined range that includes the reference frequency difference.

[0052] In addition, the data processing device can set the actuator in such a way that a number of

[0053] Impedance points are present in a frequency range that correspond to the number of reference impedance points in the reference frequency range. The data processing device can adjust the actuator such that the frequency range is shifted such that it corresponds to the reference frequency range or the offset between the frequency range and the reference frequency range lies within a predetermined range.

[0054] The frequency range can be equal to the reference frequency range. In this case, the same number of impedance points and reference impedance points are present in the same frequency range. In particular, it can be checked whether the same number of resonance points and / or anti-resonance points are present in the same frequency range. The number can be zero, so that no impedance point and / or reference impedance point is present in the frequency range.

[0055] As already described above, the actuator can be adjusted by changing the mechanical preload applied to the actuator. By changing the mechanical preload, at least one impedance point or several impedance points can be shifted with respect to their impedance value and / or frequency value. The shift of the at least one impedance point can be performed in such a way that at least one of the above-mentioned adjustment conditions is met.

[0056] Alternatively or additionally, the excitation signal to the actuator can be changed during dispensing mode depending on the test result from the adjustment mode. By changing the excitation signal, particularly the amplitude of the excitation signal, excessive or insufficient mechanical preload can be compensated. Thus, by using the excitation signal during dispensing mode, the actuator can be precisely adjusted.

[0057] As explained in more detail below, the actuator can be easily adjusted by checking whether one or more adjustment conditions are met. This is possible because the tolerances of the components of the dispensing devices are reflected in the impedance values ​​and therefore a target state for the actuator can be easily set by observing the impedance values. In particular, it was recognized that the actuator can be easily adjusted if the determined impedance values ​​are examined to determine whether a resonance and / or an anti-resonance is present in at least one predetermined frequency range and / or whether at least one impedance value lies in a predetermined impedance range and / or whether a predetermined number of resonances and / or anti-resonances is present in a predetermined frequency range.

[0058] The bias voltage change described above can be implemented within the framework of a control process by the data processing device. Within the framework of the control process, the data processing device can cause the transmission of one or more control signals and the associated determination of impedance values ​​to be carried out several times in succession until at least one or more of the above-mentioned setting conditions are met.

[0059] In a particular embodiment, at least one additional impedance value, in particular several additional impedance values, can be determined to adjust the piezoelectric actuator. During the determination process, the actuator is not preloaded. Thus, the impedance value is influenced by the actuator and not by the piston and / or dispenser and / or the preloading device. Adjusting the actuator based on this method can be performed alternatively or in addition to one of the two embodiments described above, or in addition to both of the embodiments described above.

[0060] The data processing device can determine at least one reference deviation of the reference impedance value from the further impedance value. Furthermore, a deviation between the at least one impedance value and the further impedance value can be determined. It is also possible for multiple reference deviations and multiple deviations to be determined in an analogous manner. The actuator can be adjusted such that the deviation corresponds to the reference deviations or lies within a predetermined range that includes the reference deviation. If multiple deviations and multiple reference deviations are determined, the actuator can be adjusted such that the respective deviation corresponds to the respectively assigned reference deviation or lies within the predetermined range.

[0061] In this method for adjusting the actuator, the data processing device can also change the bias voltage of the piezoelectric actuator. In this method, the bias voltage can also be changed within the scope of a control process by the data processing device. Within the scope of the control process, the data processing device can cause the transmission of at least one control signal and the associated determination of impedance values ​​to be carried out several times until the at least one deviation corresponds to the reference deviation or lies within the specified range.

[0062] Alternatively or additionally, the data processing device can change the amplitude of the control signal during dispensing. The change depends on the test result from the setting mode. The magnitude of the change depends on the extent to which the deviation differs from the reference deviation.

[0063] This method takes advantage of the fact that the reference deviations of the additional impedance values ​​and the reference impedance values ​​are constant or essentially constant, regardless of the tolerances in the dispensing device. Therefore, during actuator adjustment mode, if the deviation between the determined impedance values ​​for a preloaded actuator and the additional impedance values ​​is known, the change in the bias voltage and / or the amplitude of the excitation signal can be easily determined. The bias voltage must be changed such that the deviation between the determined impedance values ​​and the additional impedance values ​​corresponds to the reference deviation or lies within the specified range. Alternatively or additionally, the amplitude of the excitation signal can be changed accordingly during dispensing mode so that the dispensed liquid samples are comparable.

[0064] Once the piezoelectric actuator has been adjusted by changing the bias voltage using the bias device and / or once it is known whether the control signal needs to be changed during dispensing mode, the actuator's adjustment mode is terminated. The dispensing device can then be transferred to dispensing mode, in which liquid sample is dispensed. The bias voltage is changed to the bias voltage determined during adjustment mode, and / or the dispensing process(es) are performed using the bias voltage and / or the control signal determined during adjustment mode.

[0065] A dispenser is defined as a device that holds a liquid sample. Furthermore, the dispenser dispenses the liquid sample after actuation by the piston or actuator in the dispensing mode. The liquid sample is discharged through an outlet opening of the dispenser. The outlet opening is dimensioned such that no liquid sample escapes from the dispenser due to capillary forces when the dispenser is not actuated by the piston or actuator.

[0066] The dispenser can be releasably inserted into a holder of the dispensing device. This makes it possible to replace the dispenser, for example to avoid contamination of liquid samples. The dispenser can have the dispenser section that is actuated by the piston or actuator to dispense liquid sample. The dispenser section can be made of a material that differs from the material of the rest of the dispenser. In particular, the dispenser section can have a mechanical membrane that is actuated by the piston to dispense liquid sample. The dispenser section can have the outlet opening through which liquid sample exits the dispenser. In addition, the dispenser can have a receiving space with a receiving opening for introducing liquid sample into the dispenser.The receiving space can be fluidically connected to the outlet opening by means of an outlet channel, wherein the outlet channel extends at least partially within the dispenser section. The outlet channel can have a smaller flow cross-section than the receiving space.

[0067] The dispensing device can have a deflection and / or suction device. The deflection device serves to deflect the dispensed liquid sample, in particular the dispensed drop. The suction device serves to suction the dispensed liquid sample. The dispensed liquid can be deflected and / or suctioned into a waste container. The deflection and / or suction can occur before the dispensed liquid enters the container, in particular the container of a microtiter plate. The dispensed liquid can be deflected and / or suctioned if the liquid contains no particles. Alternatively, the dispensed liquid can be deflected and / or suctioned if the number of particles contained in the liquid is greater or smaller than a predetermined value, in particular greater than 1.

[0068] Of particular advantage is a data processing device that has means by which the method according to the invention can be carried out. The data processing device can have an excitation unit for outputting the excitation signal. Furthermore, the data processing device can have a computing unit. The computing unit can be configured to determine the impedance values ​​and / or adjust the actuator in the manner described above based on the received data.

[0069] The data processing device can comprise a processor. Furthermore, the data processing device can comprise a circuit board with electrical components, such as the processor. The electrical components can be used, for example, to determine the impedance value. The data processing device can be configured to adjust the actuator. Furthermore, the data processing device can be configured to control and / or regulate the dispensing operation of the dispensing device. Alternatively, another data processing device can be provided by which the dispensing operation of the dispensing device is controlled or regulated.

[0070] Also particularly advantageous is a computer program that includes instructions that, when executed by a computer, cause the computer to carry out the method according to the invention. The computer can be the aforementioned data processing device. Furthermore, a computer-readable data carrier on which the computer program is stored is present. A data carrier signal that transmits the computer program is also advantageous.

[0071] The figures show the subject matter of the invention schematically, with identical or equivalent elements generally being provided with the same reference numerals. Here:

[0072] Fig. 1 is a schematic representation of a dispensing device according to the invention,

[0073] Fig. 2 shows a reference impedance curve in a state in which the piezoelectric actuator is biased with an ideal voltage,

[0074] Fig. 3 Impedance curves in a state where the piezoelectric actuator is biased with too low a voltage and in a state where the piezoelectric actuator is biased with an ideal voltage,

[0075] Fig. 4 shows an impedance curve in a state in which the piezoelectric actuator is biased with too high a voltage and in a state in which the piezoelectric actuator is biased with an ideal voltage,

[0076] Fig. 5 shows an impedance curve for the actuation system in a state in which the piezoelectric actuator is not prestressed,

[0077] Fig. 6 is a flow chart illustrating the determination of reference impedance values,

[0078] Fig. 7 is a flowchart illustrating a method for adjusting the piezoelectric actuator according to a first embodiment,

[0079] Fig. 8 is a flowchart illustrating a method for adjusting the piezoelectric actuator according to a second embodiment,

[0080] Fig. 9 shows a control scheme for adjusting the piezoelectric actuator according to a third embodiment. A dispensing device 1 shown in Fig. 1 comprises a dispenser 2 for receiving liquid sample 3. Furthermore, the dispensing device 1 comprises a piston 4 for actuating the dispenser 2 to dispense liquid sample 3 from the dispenser 2. Furthermore, the dispensing device 1 comprises a piezoelectric actuator 5 for actuating the piston 4 and a data processing device 6.

[0081] The data processing device 6 is configured to transmit a plurality of excitation signals to the actuator 5. During a dispensing operation of the dispensing device 1, the actuator 5 actuates the piston 4 based on the excitation signals, which causes the piston 4 to actuate the dispenser 2 to dispense liquid sample 3 from the dispenser 2. The data processing device 6 comprises an excitation unit 12 for generating the excitation signals.

[0082] The dispensing device 1 also has a pretensioning device 8, by means of which the piezoelectric actuator 5 is mechanically pretensioned with a voltage. The mechanical pretensioning device 8 is electrically connected to the data processing device 6. Therefore, the data processing device 6 can control the mechanical pretension by sending control signals, for example, to a motor of the pretensioning device 8. In an alternative embodiment (not shown), the pretensioning device 8 can be manually operated to adjust the pretension applied to the actuator.

[0083] The dispenser 2 can have a receiving chamber 9 for receiving liquid sample 3. The receiving chamber 9 has an inlet opening through which the liquid sample 3 is fed into the receiving chamber 9. Furthermore, the dispenser 2 can have a dispenser body 16 that is transparent and designed as a solid. The dispenser 15 can be a drop generator that dispenses the liquid in the form of a drop, as shown in Figure 5.

[0084] The dispenser 2 also has a dispenser section 10 that is fluidically connected to the receiving space 9. The dispensing section 10 has an outlet opening through which liquid sample exits the dispenser 2. The outlet opening has a geometry such that the liquid sample cannot exit the outlet opening due to capillary forces when the piston 3 does not actuate the dispenser section 10. The dispenser has an outlet channel that is fluidically connected to the outlet opening at one end and to the receiving space at the other. The outlet channel extends partially through the dispenser section 10 and has a smaller flow cross-section than the receiving space 9. The dispenser section 10 has a flexible membrane and is made of a different material than the dispenser body 16.

[0085] The dispensed liquid sample 3 can contain only liquid. Alternatively, the dispensed liquid sample 3 can contain one or more particles. In dispensing mode, the dispensed liquid sample 3 has a predetermined number of particles, which are dispensed into a container 17.

[0086] The dispensing device 1 has a holding device (not shown) that supports the containers 17. The containers 17 can be part of a microtiter plate 18. Furthermore, the dispensing device 1 has a displacement device 19 by means of which the dispenser 2 and the microtiter plate 18 can be displaced relative to one another. This makes it possible to adjust the container into which the liquid sample is dispensed. The displacement device 19 is electrically connected to the data processing device 6 and is controlled by the data processing device 6.

[0087] The dispensing device 1 also has an optical detection device 7. The optical detection device 7 is configured to detect the dispensed liquid sample 3. Furthermore, the optical detection device 7 is configured to detect at least a portion of the outlet channel and the outlet opening. The optical detection device 7 can determine whether the dispensed liquid sample 3 has a predetermined physical property. The optical detection device 7 is electrically connected to the data processing device 6.

[0088] Furthermore, the dispensing device 1 comprises a suction or deflection device by means of which the dispensed liquid sample 3 can be suctioned or deflected before the liquid sample enters the container 17. The suction and / or deflection typically occurs during dispensing when the dispensed liquid sample does not contain a predetermined number of particles.

[0089] As described above, a liquid sample 3 is dispensed when the dispenser section 10 is actuated by the piston 4. For this purpose, the piston 4 is actuated by the piezoelectric actuator 5, whereby the piston 4 moves linearly. The actuation of the piston 4 occurs depending on the excitation signal transmitted to the actuator 5 by the data processing device 6.

[0090] The dispensing device 1 can be operated in a setting mode. In the setting mode, the actuator 5 is adjusted such that the liquid samples 3 dispensed in a dispensing mode are comparable. This is the case, for example, if the liquid samples 3 have the same shape and / or the same volume and / or the same speed.

[0091] In adjustment mode, the data processing device 6 transmits at least one excitation signal to the actuator 5 preloaded by the preload device 8. Furthermore, at least one impedance value of the excited actuator 5 is determined. The data processing device 6 is configured to receive data. The received data can contain information about the voltage and / or current. The data processing device 6 can determine the at least one impedance value based on the received data. For this purpose, the data processing device 6 has a computing unit 13, by means of which the at least one impedance value is determined. The data processing device 6 adjusts the piezoelectric actuator 5 depending on the impedances of the actuation system 11.

[0092] In an alternative dispensing device 1 (not shown in the figures), the dispensing device 1 can have a measuring device that determines the impedances. In this embodiment, the determined impedances are transmitted to the data processing device 6.

[0093] In Figure 1, mechanical connections between components are shown with a dashed line and electrical connections between components are shown with a solid line.

[0094] Fig. 2 shows a reference impedance curve in a state in which the piezoelectric actuator 5 is biased with an ideal voltage. The reference impedance curve depends on the frequency of the excitation signal transmitted to the actuator 5. The reference impedance curve corresponds to the impedance curve that exists when the actuator 5 is biased at a voltage in which the dispensed liquid sample 3 has a predetermined property during dispensing operation of the dispensing device. In this case, the liquid samples dispensed in a dispensing operation are comparable. Thus, the reference impedance curve represents the desired impedance curve, so that the three methods described in more detail below are intended to adjust the actuator 5 such that the determined impedance curve corresponds to the reference impedance curve. The determination of the reference impedance curve is described in more detail in Figure 6.

[0095] The reference impedance curve exhibits several characteristic reference frequency ranges and / or reference impedance points. For example, there is a first reference frequency range R1 that exhibits two characteristic reference impedance points. The reference impedance points are a reference resonance point 21 and an anti-reference resonance point 22.

[0096] In addition, there is a second reference frequency range R2, which has four characteristic reference impedance points. Thus, the second reference frequency range has two reference resonance points 21 and two reference anti-resonance points 22. The two reference resonance points 21 differ from each other in their reference impedance values. Likewise, the two reference anti-resonance points differ from each other in their reference impedance values. The first reference frequency range R1 has a lower frequency than the second reference frequency range R2.

[0097] The width of the second reference frequency range R2 corresponds to the width of the second frequency range F2 in a state in which the actuator 5 is not biased. This state is shown in Figure 5. The second reference frequency range R2 is selected analogously to the second frequency range F2 shown in Figure 5 such that it has a reference resonance point and a reference anti-resonance point. The reference resonance point can be the reference resonance point with the lowest impedance value.

[0098] Fig. 3 shows impedance curves for a condition in which the piezoelectric actuator is biased with too low a voltage and for a condition in which the piezoelectric actuator is biased with an ideal voltage. The impedance curve in the condition in which the piezoelectric actuator is biased with the ideal voltage is shown in dashed lines. The dashed impedance curve corresponds to the reference impedance curve shown in Fig. 2. The impedance curve depends on the frequency of the excitation signal transmitted to actuator 5.

[0099] As can be seen from Figure 3, the impedance curve and the reference impedance curve differ. Thus, the impedance curve in a first frequency range F1, which corresponds to the reference frequency range R1, has no characteristic impedance points. In particular, the impedance curve in the first frequency range F1 has no resonance point and no anti-resonance point. In other words, the number of impedance points in the first frequency range differs from the number of reference impedance points in the first reference frequency range.

[0100] The impedance curve also differs from the reference impedance curve in the second frequency range F2. Thus, the second frequency range F2 is shifted from the reference frequency range toward lower frequencies. Analogous to the second reference resonance point, the second frequency range F2 includes the resonance point with the lowest impedance value and a predefined range around the resonance point.

[0101] Thus, the impedance curve has six characteristic impedance points, whereas the reference impedance curve has only four characteristic impedance points. Specifically, the impedance curve has three resonance points 14 and three antiresonance points 15, and the reference impedance curve has two reference resonance points 21 and two reference antiresonance points 22. In other words, the number of impedance points differs from the number of reference impedance points in the second frequency range.

[0102] Another difference is that the impedance values ​​of the resonance points differ significantly from the reference impedance values ​​of the reference resonance points. The same applies to the impedance values ​​of the antiresonance points.

[0103] Another difference is that a frequency difference between two impedance points is significantly different from a reference frequency difference between two reference impedance points. The frequency difference can be determined between the frequency values ​​assigned to the resonance points or between the frequency value assigned to a resonance point and the frequency value assigned to an anti-resonance point.

[0104] Fig. 4 shows an impedance curve for a condition in which the piezoelectric actuator is biased with an excessively high voltage, and for a condition in which the piezoelectric actuator is biased with an ideal voltage. The impedance curve for the condition in which the piezoelectric actuator is biased with the ideal voltage is shown in dashed lines. The reference impedance curve shown in dashed lines corresponds to the reference impedance curve shown in Fig. 2. The impedance curve depends on the frequency of the excitation signal transmitted to actuator 5.

[0105] The impedance curve differs from the reference impedance curve. Analogous to the impedance curve shown in Fig. 3, the impedance curve in the first frequency range F1 exhibits no characteristic impedance points, i.e., no resonance point and no antiresonance point.

[0106] In a third frequency range F3 of the impedance curve, which lies between the first and second frequency ranges, two characteristic impedance points exist: a resonance point 14 and an anti-resonance point 15. This is not the case with the reference impedance curve. Furthermore, the impedance values ​​of the impedance points occurring in the third frequency range F3 differ from the reference impedance values ​​of the reference impedance points present in the second reference frequency range R2.

[0107] Another difference is that the second frequency range F2 is shifted towards higher frequencies starting from the second reference frequency range R2.

[0108] Fig. 5 shows an impedance curve in a state in which the piezoelectric actuator 5 is not biased. In the state shown in Figure 5, no voltage is exerted on the actuator 5 by the biasing device 8. The impedance curve has two impedance points in the second frequency range F2, namely a resonance point 14 and an anti-resonance point 15. The second frequency range F2 is selected such that it contains the two impedance points 14, 15. In other words, after determining the impedance curve in the state in which the actuator 5 is not biased, the width of the second frequency range F2 is known. This width is used to define the second reference frequency range R2 and for the impedance curves shown in Figures 3 and 4. This makes it possible to determine whether or not the second frequency range is shifted compared to the second reference frequency range R2.

[0109] Fig. 6 shows a flowchart for determining reference impedance values. In a first step S1, a dispensing process is performed, comprising one or more dispensing steps. A liquid sample is dispensed per dispensing step. For this purpose, the piston 4 is actuated by the actuator 5, which receives at least one excitation signal, in particular a voltage signal, from the data processing device 6. During the dispensing processes, the mechanical preload of the actuator 5 is not changed.

[0110] In a second step S2, the optical detection device 7 detects the dispensed liquid sample. The optical detection device determines a physical property of the dispensed liquid sample 3. The physical property can be the volume of the liquid sample and / or the shape of the dispensed liquid and / or the velocity of the liquid sample and / or other properties. In a third step S3, for each dispensed liquid sample 3, a check is performed to determine whether the determined physical property corresponds to a predetermined property. The check can be performed in the optical detection device 7 or in the data processing device 6. Alternatively, the check can be performed manually.

[0111] If the condition is not met, the preload of actuator 5 is changed by preload device 8, and steps S1 to S3 are performed again. This means that another dispensing process with one or more dispensing steps is performed.

[0112] If the condition is met, a reference impedance measurement is performed in the fourth step S4. The actuator 5 is biased with a voltage corresponding to the voltage of the actuator 5 at which the liquid samples 3 exhibiting the specified property were dispensed. For this purpose, at least one excitation signal is transmitted to the actuator 5, and at least one reference impedance value, in particular a plurality of reference impedance values, is determined. The frequency of the excitation signal can be varied. Alternatively, a plurality of excitation signals differing from one another in frequency can be transmitted to the actuator 5, thus determining a plurality of reference impedance values.

[0113] Fig. 7 shows a flowchart illustrating a method for adjusting the piezoelectric actuator 5 according to a first embodiment. In a first method step T1, a dispenser 2 is inserted into a holder of the dispensing device 1.

[0114] In a second step T2, the data processing device 6 transitions to a setting mode in which at least one excitation signal is transmitted to the piezoelectric actuator 5, the frequency of which varies over time. Alternatively, excitation signals differing from one another in frequency can be supplied to the actuator 5. The mechanical preload is not changed during the transmission of the at least one excitation signal and / or during the determination of the impedance values. The data processing device 6 determines at least one impedance value for each excitation signal. Thus, after passing through a predetermined frequency range, several impedance values ​​are available.

[0115] In a third step T3, based on the determined impedance values, a check is performed to determine whether the actuator 5 is correctly adjusted. A correctly adjusted actuator 5 ensures that the dispensed liquid sample 3 exhibits the desired physical property during the dispensing operation of the dispensing device 1. The check takes advantage of the fact that the reference impedance curve (see Figure 2) is known. In particular, after examining the reference impedance curve, the reference frequency range R1, R2 and / or reference impedance points 21, 22 are known, based on which it can be assessed whether the actuator 5 is correctly adjusted.

[0116] This is possible because the reference impedance curve reveals the number and type of resonances and / or anti-resonances in which reference frequency sections R1, R2 are present. Furthermore, the reference impedance curve reveals the impedance values ​​of, for example, resonances and / or anti-resonances in the reference frequency sections R1, R2, which can be used to determine whether actuator 5 is correctly adjusted.

[0117] For this purpose, in the third step T3, it can be checked whether one or more of the following setting conditions are met or not. This allows checking whether a resonance and an anti-resonance are present in a first frequency range F1 of the impedance curve. Furthermore, it can be checked whether the second frequency range F2 corresponds to the second reference frequency range or is offset from it. Depending on whether the offset is directed toward lower or higher frequencies, it can be determined whether the bias voltage applied to the actuator is too low or too high.

[0118] In addition, it can be checked whether the number of impedance points present in the second frequency range, namely resonance points and / or anti-resonance points, corresponds to the number of reference impedance points. Alternatively or additionally, it can be checked whether the impedance values ​​of the impedance points in the second frequency range differ significantly from the impedance values ​​of the impedance points in the second reference frequency range.

[0119] Furthermore, it is possible to check whether a frequency difference between two impedance points corresponds to a reference frequency difference or lies within a specified range. Furthermore, the third frequency range F3 can be checked to see whether it contains a resonance point and an anti-resonance point.

[0120] The data processing device 6 performs the above-mentioned tests and, based on the test result(s), determines whether the actuator 5 is correctly adjusted. The actuator 5 is correctly adjusted if the test(s) show that the impedance values ​​meet the conditions described in Figure 2.

[0121] If one or more setting conditions are not met, the data processing device can determine whether the preload is too high or too low based on the test result(s). The actuator 5 is then adjusted in a fourth step S4. In particular, the preload of the actuator 5 can be changed by the preload device 8. Subsequently, the second and third steps T2, T3 are repeated with the changed preload. This process continues until it is determined in the third step T3 that at least one or more setting conditions are met.

[0122] If the setting conditions are met, the data processing device determines that actuator 5 is correctly set. Therefore, in the fifth step T5, the setting operation is terminated and the dispensing operation of the dispensing device 1 is started. In dispensing operation, actuator 5 is preloaded with the preload determined in the setting operation.

[0123] Fig. 8 shows a flowchart illustrating a method for adjusting the piezoelectric actuator 5 according to a second embodiment. The first step P1 corresponds to step T1 in Figure 7, so reference is made to the above explanations.

[0124] In a second step P2, analogous to the second step T2, at least one excitation signal whose frequency varies over time is supplied to the actuator 5. Alternatively, several excitation signals that differ from one another in frequency can be supplied to the actuator. However, unlike the second step T2 in Figure 2, the actuator 5 is not biased. This means that the data processing device 6 determines additional impedance values ​​that have the curve shown in Figure 5.

[0125] In a third step P3, an impedance measurement is performed again. For this purpose, at least one excitation signal is supplied to the actuator 5, the frequency of which varies over time. Alternatively, several excitation signals that differ from one another in frequency can be supplied to the actuator. In contrast to the second step P2, however, the actuator 5 is mechanically preloaded by the preload device 8. The impedance values ​​are determined analogously to the second step P2. Assuming that the actuator 5 is not correctly adjusted, impedance values ​​are obtained that have the curve shown in Figure 3 or Figure 4 or a similar curve.

[0126] In a fourth step P4, at least one deviation between the impedance values ​​determined in the third step P3 and the impedance values ​​determined in the second step P2 is determined. In a fifth step P5, it is determined whether the at least one deviation corresponds to a reference deviation. The reference deviation corresponds to a deviation between the further impedance values ​​determined in a non-biased state of the actuator, the curve of which is shown in Figure 5, and reference impedance values ​​determined analogously to the method described in Figure 6 and shown in Figure 2.

[0127] The data processing device 6 checks whether the at least one deviation corresponds to the reference deviation or lies within a predetermined range containing the reference deviation. If this is not the case, the actuator 5 is adjusted in a sixth step P6. The adjustment is performed analogously to the fourth step in Figure 7 by changing the mechanical preload applied to the actuator 5. Steps P3 and P4 are then repeated until the adjustment condition in the fourth step P4 is met.

[0128] If the test in the fifth step P5 shows that the setting condition is met, the data processing device terminates the setting mode in the seventh step P7 and switches to dispensing mode. In dispensing mode, actuator 5 is preloaded with the preload determined in the setting mode.

[0129] Fig. 9 shows a control scheme for adjusting the piezoelectric actuator 5 according to a third embodiment. The third embodiment differs from the two embodiments, whose sequence is shown in Fig. 7 and Fig. 8, in that each impedance value is checked to determine whether it corresponds to a reference impedance value or lies within a predetermined range containing the reference impedance value. This is explained in more detail below. In contrast, the impedance measurement is carried out analogously to the two methods by transmitting at least one excitation signal, in particular several excitation signals, to the actuator 5. Reference is made to the above explanations in this regard.

[0130] The following control steps can be performed in the data processing device 6. In a first control step C1, a deviation from a reference impedance value associated with the impedance value is determined for each impedance value. The impedance value and the reference impedance value are associated with each other via the frequency value of the excitation signal. Thus, both values ​​have the same frequency value.

[0131] In a second control step C2, a check is made to determine whether the deviation lies within a specified range. Depending on the test result, a third control step C3 determines whether actuator 5 is correctly adjusted or needs to be adjusted. If actuator 5 needs to be adjusted, a control variable for preload device 8 is output in the third control step C3, whereupon the preload of actuator 5 is changed.

[0132] The impedance measurement is performed again in a fourth control step C4, but the bias voltage of actuator 5 has been changed based on the manipulated variable. Control steps C1 to C3 are repeated until the deviation between the at least one impedance value and the reference impedance value is within the specified range. In this case, the third control step C3 determines that the adjustment operation is terminated.

[0133] List of reference symbols

[0134] 1 dispensing device

[0135] 2 dispensers

[0136] 3 liquid sample

[0137] 4 pistons

[0138] 5 piezoelectric actuator

[0139] 6 Data processing facility

[0140] 7 optical detection device

[0141] 8 Pre-tensioning device

[0142] 9 Recording room

[0143] 10 Dispenser section

[0144] 12 Excitation unit

[0145] 13 Computing unit

[0146] 14 Resonance

[0147] 15 Antiresonance

[0148] 16 dispenser bodies

[0149] 17 Container

[0150] 18 microtiter plates

[0151] 19 Traversing device

[0152] 20 Extraction deflection device

[0153] 21 Reference resonance point

[0154] 22 Reference antiresonance point

[0155] C1 -C4 steps when executing the procedure according to the third embodiment

[0156] F1 first frequency range

[0157] F2 second frequency range

[0158] F3 third frequency range

[0159] P1 -P7 steps when executing the procedure according to the second embodiment

[0160] R1 first reference frequency range

[0161] R2 second reference frequency range

[0162] S1 -S3 steps for determining reference impedance curve

[0163] T1 -T5 steps when executing the procedure according to the first execution

Claims

Patent claims 1. A method for adjusting a piezoelectric actuator (5) of a dispensing device (1), the method comprising the following steps: Sending at least one excitation signal to the actuator (5) and Determining at least one impedance value of the excited actuator (5), wherein the piezoelectric actuator (5) is adjusted depending on the determined at least one impedance value.

2. Method according to claim 1, characterized in that a. the excitation signal is a voltage signal and / or that b. the excitation signal lies within a frequency range and / or that c. the excitation signal varies over time.

3. Method according to claim 1 or 2, characterized in that a plurality of excitation signals are emitted, wherein a. the excitation signals differ from one another in frequency and / or b. the excitation signals lie within a predetermined frequency range.

4. Method according to one of claims 1 to 3, characterized in that determining the impedance value comprises receiving data, wherein the data represents at least one impedance value of the excited actuator (5) or by means of which at least one impedance value of the actuator (5) is determined.

5. Method according to one of claims 1 to 4, characterized in that a. the impedance value is determined when the actuator (5) is prestressed and / or that b. the actuator (5) is prestressed during the determination process.

6. Method according to one of claims 1 to 5, characterized in that a. the impedance value is determined in a setting operation of the dispensing device and / or that b. a setting operation of the dispensing device is carried out prior to a dispensing operation of the dispensing device and / or that c. an adjustment operation of the dispensing device (1) is carried out after a replacement of a dispenser (2) of the dispensing device (1) and / or after a removal of the actuator (5) and / or after a predetermined number of dispensing steps.

7. Method according to one of claims 1 to 6, characterized in that at least one reference impedance value, in particular several reference impedance values, are determined.

8. Method according to claim 7, characterized in that a plurality of dispensing processes are carried out to determine the reference impedance values, wherein the dispensing processes differ from one another in the bias voltage applied to the actuator (5).

9. The method according to claim 8, characterized in that a physical property of the liquid sample dispensed in the dispensing process and / or of the dispensing device is determined and that it is checked whether the determined physical property fulfills a predetermined condition.

10. The method according to claim 9, characterized in that at least one reference impedance value is determined, wherein the actuator (5) is biased with the voltage of the dispensing process in which the physical property fulfills the predetermined condition. 1 1 . Method according to one of claims 1 to 10, characterized in that a. it is checked whether at least one setting condition is fulfilled and the actuator (5) is adjusted depending on the test result and / or that b. in order to adjust the piezoelectric actuator (5) it is checked whether at least one setting condition is fulfilled, wherein the setting condition depends on the at least one reference impedance value and / or on the at least one impedance value.

12. Method according to one of claims 1 to 11, characterized in that a. to adjust the actuator (5), the bias applied to the actuator (5) is changed and / or that b. to adjust the actuator (5), an excitation signal is determined which is to be applied to the actuator (5).

13. Method according to one of claims 10 to 12, characterized in that it is checked whether the determined impedance value corresponds to a reference impedance value or lies in a predetermined range which has the reference impedance value.

14. Method according to claim 13, characterized in that a. the actuator (5) is adjusted such that the determined impedance value corresponds to the reference impedance value or lies in a predetermined range having the reference impedance value and / or that b. a deviation between the determined impedance value and the reference impedance value is taken into account in an excitation signal in a dispensing operation of the dispensing device.

15. Method according to one of claims 10 to 14, characterized in that a. a reference impedance value and / or reference frequency value is determined for at least one reference impedance point and / or that b. a reference frequency difference between two reference impedance points is determined and / or that c. a number of reference impedance points in a reference frequency range is determined.

16. Method according to claim 15, characterized in that it is checked whether a. an impedance point corresponds to the reference impedance point or lies in a predetermined range which has the reference impedance point and / or whether b. a frequency difference exists between two impedance points which corresponds to the reference frequency difference or lies in a predetermined range which has the reference frequency difference and / or whether c. a number of impedance points are present in a frequency range which corresponds to the number of reference impedance points in the reference frequency range.

17. Method according to one of claims 1 to 16, characterized in that for adjusting the piezoelectric actuator (5) at least one further impedance value, in particular several impedance values, are determined, wherein the actuator is not prestressed during the determination process.

18. Method according to claim 17, characterized in that a reference deviation of the reference impedance value from the further impedance value is determined.

19. Method according to claim 17 or 18, characterized in that a deviation between the at least one impedance value and the further impedance value is determined.

20. Method according to claim 19, characterized in that the actuator (5) is adjusted such that the deviation corresponds to the reference deviation or lies in a predetermined range which has the reference deviation.

21. Method according to one of claims 1 to 20, characterized in that the adjusted piezoelectric actuator (5) is used for dispensing liquid sample (3) in a dispensing operation of a dispensing device (1).

22. Dispensing device (1), in particular for carrying out a method according to one of claims 1 to 21, with a dispenser (2) for dispensing liquid sample (3), a piezoelectric actuator (5) and a data processing device (6) which is configured to output at least one excitation signal to the actuator (5) and to determine at least one impedance value of the excited actuator (5), wherein the data processing device is configured to adjust the actuator (5) depending on the determined at least one impedance value.

23. Dispensing device (1) according to claim 22, characterized in that the dispensing device (1) has an optical detection device (7) for optically detecting the dispensed liquid sample (3).

24. Dispensing device (1) according to claim 22 or 23, characterized in that the dispensing device (1) has a pretensioning device (8) for pretensioning the piezoelectric actuator (5).

25. Dispensing device (1) according to one of claims 22 to 24, characterized in that a. the dispenser (2) has a receiving space (9) for receiving liquid sample (3) and / or that b. the dispenser (2) has a dispenser section (10) which is actuated by the piston (4) or the actuator (5) in order to dispense liquid sample (3) from the dispenser (2).

26. Dispensing device (1) according to one of claims 22 to 25, characterized in that the data processing unit (6) has an excitation unit (12) for outputting at least one excitation signal and / or a computing unit (13) for determining the at least one impedance value.

27. Data processing unit (6) comprising means for carrying out the method according to one of claims 1 to 21.

28. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of claims 1 to 21.

29. A computer-readable data carrier on which the computer program according to claim 28 is stored.

30. A data carrier signal carrying the computer program according to claim 28.

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