MEASURING DEVICE AND MICROPARTTIC MEASURING SYSTEM

Abstract

Measuring device (200, 200A, 200R) configured to measure a current signal for microparticle detection which flows through a nanopore device (100) with an opening (104) and an electrode pair (106, 108), wherein the measuring device (200, 200A, 200R) comprises the following: - a transimpedance amplifier (210, 210A) designed to convert the current signal into a voltage signal; and - a voltage source (220) configured to apply a DC bias voltage to the electrode pair (106, 108) in a normal measurement operating mode and to apply a calibration voltage, which has a predetermined waveform with an alternating current component, to the electrode pair (106, 108) in a calibration mode, wherein in normal measurement mode the nanopore device (100) contains particles (4) to be detected, and wherein in calibration mode the nanopore device (100) contains no particles (4) to be detected and at least one circuit constant of the measuring device (200) can be calibrated based on an output signal of the transimpedance amplifier (210, 210A) and the calibration voltage.

Description

AREA OF INVENTION

[0001] The present invention relates to measurement using a nanopore device. DESCRIPTION OF THE STATE OF THE TECHNOLOGY

[0002] A method for measuring particle size distribution, known as the "electrical sensing zone method" (Coulter principle), is known. In this method, an electrolyte solution containing particles is applied such that it passes through an opening called a "nanopore." When a particle passes through such an opening, the amount of electrolyte solution filling the opening is reduced by an amount equal to the volume of the particle, thus increasing the electrical resistance of the opening. Accordingly, if the opening has a thickness greater than the particle size, this arrangement can measure the volume of the particle passing through the opening by measuring its electrical resistance. Conversely, if the opening has a thickness sufficiently smaller than the particle size, this arrangement can measure the cross-sectional area (i.e., the area of ​​the particle passing through the opening).to measure the diameter) of the particle passing through the opening.

[0003] Fig. Figure 1 is a block diagram depicting a microparticle measurement system 1R, which uses the "electrical sensing zone method". The microparticle measurement system 1R includes a nanopore device 100, a measuring device 200R and a data processing device 300.

[0004] The interior of the nanopore device 100 is filled with an electrolyte solution 2 containing the particles 4 to be detected. The interior of the nanopore device 100 is divided by a nanopore chip 102, thus defining two interior spaces. Electrodes 106 and 108 are assigned to these two spaces. When an electrical potential difference is generated between electrodes 106 and 108, this creates an ion current flow between the electrodes. Furthermore, the particles 4 migrate from one space to the other space via the opening 104 by electrophoresis.

[0005] The measuring device 200R generates the electrical potential difference between the electrode pair 106 and 108 and acquires information that correlates with the resistance value Rp between the electrode pair. The measuring device 200R includes a transimpedance amplifier 210, a voltage source 220, and a digitizer 230. The voltage source 220 generates an electrical potential difference Vb between the electrode pair 106 and 108. The electrical potential difference Vb acts as the driving source for the electrophoresis and is used as a bias signal for measuring the resistance value Rp.

[0006] A microcurrent Is flows between the electrode pair 106 and 108 in inverse proportion to the resistance of the opening 104. Is=Vb / Rp

[0007] The transimpedance amplifier 210 converts the microcurrent Is into a voltage signal Vs. With the conversion gain as r, the following equation applies. Vs=r×Is

[0008] Substituting equation (1) into equation (2) yields the following equation (3). Vs=Vb×r / Rp

[0009] The digitizer 230 converts the voltage signal Vs into digital data Ds. As described above, the measuring device 200R is able to detect the voltage signal Vs in inverse proportion to the resistance value Rp of the opening 104.

[0010] Fig. Figure 2 is a waveform diagram of an example of the microcurrent measured by the measuring device 200R. It should be noted that the vertical and horizontal axes shown in the waveform and time diagrams in this description are extended or reduced as necessary for clarity. Furthermore, each waveform in the drawings is simplified or exaggerated to emphasize it or make it easier to understand.

[0011] During the brief period in which a particle passes through opening 104, the resistance value Rp of opening 104 increases. Accordingly, the current Is decreases in the form of a pulse each time a particle passes through opening 104. The change in current Is correlates with the particle size. The data processing device 300 processes the digital data Ds to analyze the number of particles 4 contained in the electrolyte solution 2, their particle distribution, or similar information. [State of the art documents][Patent documents] [Patent document 1] Japanese patent application JP 2011 - 513 739 A [Patent document 2] Japanese patent application JP H04 - 040 373 A [Patent document 3] PCT patent application WO 94 / 16308A1 [Patent document 4] Japanese patent application JP 2004 - 510 980 A [Patent document 5] US patent application US 2016 / 0154033A1 [Patent document 6] US patent application US 2013 / 0048499A1 [Patent document 7] German patent application DE 10 2006 032 906 A1 [Patent document 8] German patent application DE 25 34 955 A1 [Patent document 9] GB patent application GB 193 393 A

[0012] Patent document 5 (US 2016 / 0154033A1) relates to a measuring device that measures a current signal flowing through a device under test. A transimpedance amplifier converts the current signal into a voltage signal. A digitizer converts the voltage signal into digital data. A digital signal processing unit processes the digital data and controls the measuring device.

[0013] Patent document 6 (US 2013 / 0048499A1) relates to a device for measuring a parameter of a biomolecule using the Coulter principle. The device comprises a first liquid chamber and a second liquid chamber, as well as a synthetic nanopore located between the chambers. The nanopore defines a liquid flow direction from the first liquid chamber to the second liquid chamber and provides a pathway for molecules or other nanoparticles in the first chamber to flow to the second chamber. The device further includes electrodes in both liquid chambers and means for controlling the electrodes to measure the resistance, voltage difference, or ion current between the first and second electrodes.

[0014] Patent document 7 (DE 10 2006 032 906 A1) relates to a device for detecting and evaluating particles in a gas stream, comprising at least one sensor element having a flow-through opening through which the gas stream can flow. The device further comprises electrodes by means of which an electric field can be generated in the flow-through opening.

[0015] Patent document 8 (DE 25 34 955 A1) concerns the determination of the physical properties of particle systems, in particular the exact size distribution of the particles in such a system.

[0016] Patent document 9 (GB 193 393 A) concerns switching devices for railway transport.

[0017] In conventional electrical sensing zone methods, standard particles with a known particle size (volume) are first measured for calibration to establish a correlation between the particle size of each standard particle and the digital data Ds. Subsequently, measurements are performed for particles of arbitrary sizes to acquire the digital data Ds. The particle sizes are then determined based on the previously obtained correlation. Consequently, the information obtained with such conventional electrical sensing zone methods is limited to the number of particles or, alternatively, to the particle size (volume). This means that this approach is incapable of capturing detailed characteristic information such as particle shape or similar features. SUMMARY OF THE INVENTION

[0018] The present invention relates to a measuring device according to independent claim 1, wherein advantageous embodiments of the measuring device according to the invention are specified in dependent claims 2 to 11. The invention further relates to a microparticle measuring system according to dependent claim 12, wherein an advantageous embodiment of the microparticle measuring system according to the invention is specified in dependent claim 13.

[0019] With regard to the cause of the problem, the present invention focuses attention on the response speed (bandwidth) of the microparticle measurement system 1. That is, in a case where the microparticle measurement system 1 operates at a sufficiently high speed, the waveform of the digital data Ds correlates with the particle shape. However, for the reason mentioned below, it is difficult to equip such a conventional microparticle measurement system 1 with a large bandwidth.

[0020] Fig. Figure 3 is an equivalent circuit diagram showing the nanopore device 100 and the transimpedance amplifier 210.

[0021] As the diameter of aperture 104 decreases, the resistance Rp of aperture 104 increases, necessitating measurement in the microcurrent range. To provide a signal-to-noise ratio that meets the requirements, a resistor Rf with a resistance value of 100 MΩ to 1 GΩ is required. In this case, the resistor Rf is mounted as a high-precision lead resistor of a measuring device or, alternatively, as a chip resistor. However, such a resistor introduces a non-negligible parasitic capacitance Cf on the order of several hundred fF. This parasitic capacitance Cf drastically limits the amplifier's bandwidth (on the order of several kHz to several dozen kHz). This leads to difficulties in acquiring waveform information for obtaining detailed characteristic values ​​with respect to particle 4.

[0022] The nanopore device 100 is represented by an equivalent circuit that includes a resistance value Rp of the opening 104 and the parasitic capacitance Cp connected in parallel. The parasitic capacitance Cp causes the output voltage Vs to either exceed or fall below its value, which affects the stability of the transimpedance amplifier 210. To improve the waveform, the transimpedance amplifier 210 is configured such that its product (Rf * Cf) matches the product (Rp × Cp) of the nanopore device 100. This means that it is necessary to further increase the parasitic capacitance; that is, there is a trade-off between the bandwidth of the transimpedance amplifier 210 and its stability.

[0023] Furthermore, Rp and Cp change due to individual variations in the nanopore setup 100 and the manual application of a reagent. This leads to the problem of an unstable output waveform.

[0024] The present invention was made in consideration of such a situation. Accordingly, an exemplary purpose of one embodiment of the present invention is to provide a measuring device capable of accurately measuring the waveform of a current.

[0025] One embodiment of the present invention relates to a measuring device configured to measure a current signal flowing through a nanopore device with an opening and an electrode pair. The measuring device comprises a transimpedance amplifier configured to convert the current signal into a voltage signal; and a voltage source configured to apply a DC bias voltage to the electrode pair in a normal measuring mode and to apply a calibration voltage with an AC component to the electrode pair in a calibration mode. The measuring device is configured, in calibration mode, to calibrate at least one circuit constant of the measuring device based on an output signal from the transimpedance amplifier and the calibration voltage.

[0026] It should be noted that any combination or rearrangement of the structural components described above, and so on, is effective and encompassed by the present embodiments. Furthermore, this summary of the invention does not necessarily describe all the necessary features, so the invention may also be a subcombination of these described features. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Exemplary embodiments are now described with reference to the accompanying drawings, which are intended to be exemplary and not limiting, and in which similar elements are numbered the same in several figures, wherein: Fig. 1 represents a block diagram illustrating a microparticle measurement system using the "electrical sensing zone" method; Fig. 2 represents a waveform diagram showing an example of a microcurrent being measured by a measuring device; Fig. 3 represents an equivalent circuit showing a nanopore device and a transimpedance amplifier; Fig. 4 represents a block diagram illustrating a microparticle measurement system according to one embodiment; Fig. 5A and Fig. 5B Diagrams showing an example of a calibration process; Fig. 6 represents a block diagram illustrating a microparticle measurement system according to one embodiment; and Fig. Figure 7 shows a circuit diagram illustrating an exemplary configuration of an amplifier. DETAILED DESCRIPTION OF THE INVENTION

[0028] The invention will now be described on the basis of preferred embodiments, which do not limit the scope of the present invention but are intended to illustrate it by way of example. All features described in the embodiment and their combinations are not essential to the invention.

[0029] In the present description, the state expressed by the sentence "element A is connected to element B" includes a state in which element A is indirectly connected to element B via another element that does not substantially affect the electrical connection between them or impair the functions or effects of the connection between them, as well as a state in which they are physically and directly connected.

[0030] Similarly, the state expressed by the sentence "element C is provided between element A and element B" includes a state in which element A is indirectly connected to element C, or element B is indirectly connected to element C via another element that does not substantially affect the electrical connection between them or impair the functions or effects of the connection between them, as well as a state in which they are directly connected. BASIC VERSION

[0031] Fig. Figure 4 is a block diagram illustrating a microparticle measurement system 1 according to one embodiment. The microparticle measurement system 1 includes a nanopore device 100, a measuring device 200, and a data processing device 300.

[0032] The nanopore device 100 is as described in relation to Fig. 1 described. In particular, the nanopore device 100 includes a nanopore chip 102, which is provided with an opening 104, and an electrode pair 106 and 108. The interior of the nanopore chip 102 is filled with an electrolyte solution such as a KCl solution (potassium chloride), PBS solution (phosphate-buffered saline solution) or the like.

[0033] The measuring device 200 is configured to apply a voltage to the electrode pair 106 and 108 and to measure the current Is flowing through the opening 104. The measuring device 200 includes a transimpedance amplifier 210, a voltage source 220, a digitizer 230, an interface 240, and a calibration controller 250.

[0034] The data processing device 300 functions as a user interface. Furthermore, the data processing device 300 integrally controls the entire operation of the microparticle measurement system 1 and has functions for acquiring, storing, and displaying the measurement results. The data processing device 300 can be configured as a general-purpose computer or workstation. Alternatively, the data processing device 300 can be configured as a dedicated hardware component specifically designed for the microparticle measurement system 1.

[0035] The measuring device 200 can be switched between a normal measuring mode and a calibration mode. The data processing device 300 switches the operating mode of the measuring device 200 according to the user's (operator's) operation.

[0036] Operation in normal measurement mode is the same as in the Fig. The measuring device 200R is shown in Figure 1. In normal measurement mode, the voltage source 220 applies a DC bias voltage Vb to the electrode pair 106 and 108. The transimpedance amplifier 210 converts the current Is flowing through the nanopore device 100 into a voltage signal Vs. The digitizer 230 converts the voltage signal Vs into digital data Ds. The interface 240 transmits the digital data Ds to the data processing device 300. The time-series data of the digital data Ds represent the waveform of the current. The data processing device 300 processes the digital data Ds acquired in normal measurement mode to determine the number of particles 4 contained in the electrolyte solution 2 and their particle sizes.Furthermore, when using the calibration mode described below to increase the accuracy of the current waveform measurement, the data processing device 300 is able to capture detailed parameters such as the shape of each particle based on the current waveform.

[0037] Next, the calibration mode is described. When interface 240 receives predefined control data from data processing device 300, the measuring device 200 is put into calibration mode. In calibration mode, the calibration controller 250 controls the operation of the measuring device 200.

[0038] The calibration controller 250 instructs the voltage source 220 to generate a voltage signal for calibration. In particular, the voltage source 220 is configured to apply a calibration voltage Vcal with an AC component to the electrode pair 106 and 108.

[0039] For example, the input terminal of the transimpedance amplifier 210, i.e., electrode 106, is virtually grounded. By applying the calibration voltage Vcal with an AC component to electrode 108, the electrical potential difference between the two electrodes is changed. The waveform of the calibration voltage Vcal is represented by Vcal(t).

[0040] In calibration mode, the interior of the nanopore device 100 is filled with the electrolyte solution 2, which contains no particles 4. Accordingly, the resistance value Rp across the electrode pair 106 and 108 is constant. Consequently, the voltage signal Vs(t) at the output terminal of the transimpedance amplifier 210 corresponds to the waveform Vcal(t) of the calibration voltage Vcal.

[0041] The measuring device 200 is configured to correct at least one circuit constant based on a ratio between the output signal Vs of the transimpedance amplifier 210 and the calibration voltage Vcal. Next, a description of a process for optimizing the circuit constant is provided.

[0042] The transfer function representing the transfer from the output of the voltage source 220 to an output node of the transimpedance amplifier 210 is represented by H(s). With the spectrum of the voltage signal Vs(t) as vs(ω) and with the spectrum of the calibration voltage Vcal(t) as vcal(ω), the following equation applies. vs(ω)=H(ω)×vcal(ω)

[0043] The change in the circuit constant of the measuring device 200 corresponds to the change in the transfer function H(ω). Accordingly, from the perspective of the frequency domain, the circuit constant can preferably be optimized such that the spectrum vs(ω) of the measured voltage signal Vs approximates the spectrum vcal(ω) of the calibration voltage Vcal.

[0044] From a time domain perspective, the circuit constant can preferably be optimized such that the time waveform Vs(t) of the measured voltage signal Vs approximates the time waveform Vcal(t) of the calibration voltage Vcal.

[0045] The data processing device 300 can support a calibration process, including optimization of the circuit constant. For example, the data processing device 300 can generate waveform data Dcal of the calibration voltage Vcal(t) and transmit the waveform data Dcal to interface 240. The voltage source 220 can convert the waveform data received from the calibration controller 250 into the analog calibration voltage Vs(t). The data processing device 300 can modify the circuit constant so that the digital data Ds, representing the waveform of the voltage signal Vs, matches the waveform of the waveform data Dcal.

[0046] Alternatively, the data processing device 300 can convert the digital data Ds and the waveform data DCAL into frequency domain data using a Fourier transform and modify the circuit constants so that they approximate each other in the frequency domain.

[0047] Alternatively, the data processing device 300 can convert the digital data Ds and the waveform data Dcal into frequency domain data using a Fourier transform and calculate the ratio between them, which is used as the transfer function H(s). Furthermore, the data processing device 300 can adjust the circuit constant so that the calculated transfer function H(s) approximates ideal properties.

[0048] Furthermore, the operator can manually assist part of the process of optimizing the circuit constant. For example, the 300 data processing device can display the waveform of the calibration voltage and the waveform (or other spectrum) of the measured voltage signal on a screen so that they can be compared. The operator can visually compare the two waveforms (spectra) and select the circuit constant so that they approximate each other.

[0049] It should be noted that the calibration process can be performed by the calibration controller 250 instead of the data processing device 300, or otherwise performed jointly by the data processing device 300 and the calibration controller 250.

[0050] The above is the configuration of microparticle measurement system 1. Fig. Figure 5 is a diagram showing an example of the calibration process. In this example, a square wave is used as the calibration voltage Vs(t). Fig. Figure 5 shows the waveform Vs(t) of the voltage signal, which changes according to a change in the circuit constant of the measuring device 200. Waveform (i) represents a state in which the response rate is low, i.e., a narrow bandwidth state. Conversely, waveform (ii) represents a state in which, although the response rate is high due to high gain of the high-frequency components, oscillations easily occur due to its small phase margin. By optimizing the circuit constant, as shown by waveform (iii), this arrangement is able to support both high-speed operation and stability.

[0051] The microparticle measurement system 1, which can be optimized in calibration mode, has a further advantage, as described below. Conventional techniques result in significant distortion in the waveform of the voltage signal Vs. This leads to difficulties in extracting information (characteristic values) relating to the shape of each particle 4. In contrast, the microparticle measurement system 1, according to its embodiment, provides the voltage signal Vs with reduced waveform distortion. Consequently, the voltage waveform exhibits a strong correlation with the particle diameter distribution in the particle height direction. Therefore, the microparticle measurement system 1 is able to extract information (characteristic values) relating to the shape of each particle 4.

[0052] With the microparticle measurement system 1 according to the embodiment, this arrangement is able to compensate for the effects of fluctuations in resistance Rp that occur due to variations in the manufacture of the nanopore device 100 or due to variations in the application of a reagent. Furthermore, this arrangement is able to compensate for the effects of fluctuations in capacitance Cp that arise due to variations in the manufacture of the nanopore device 100.

[0053] Furthermore, this arrangement of the same measuring device 200 enables the measurement for several nanopore devices 100 which are designed with different design values ​​of the diameter of the opening 104 and with different design values ​​of the distance between the electrode pair 106 and 108.

[0054] The present invention comprises various types of devices and methods that can be configured as block or circuit configurations according to Fig. 4 can be considered or otherwise derived from the foregoing description. That is to say, the present invention is not limited to a specific configuration. Exemplary configurations and embodiments are described in more detail below to clarify and improve understanding of the core of the present invention and its operation. That is to say, the following description is in no way intended to limit the technical scope of the present invention.

[0055] Fig. Figure 6 is a block diagram illustrating a microparticle measurement system 1A according to one embodiment. The nanopore device 100 is shown as a parallel circuit with a resistor Rp1 and a parallel-coupled capacitor Cp1. The measuring device 200A is provided with an additional resistor or capacitor to accommodate the change in the product of Rp1 and Cp1 involved in the nanopore device 100.

[0056] The transimpedance amplifier 210A comprises an amplifier 212, capacitors Cf1 and Cf2, and resistors Rf1 and Rf2. The inverting input terminal of amplifier 212 is connected to electrode 106 of the nanopore device 100. A reference voltage is applied to the non-inverting input terminal of amplifier 212. The reference voltage can be a ground voltage. Other voltages can also be used as the reference voltage.

[0057] The first resistor Rf1 and the second resistor Rf2 are connected in series between the output terminal and the inverting input terminal of amplifier 212. The first capacitor Cf1 is connected in parallel with the first resistor Rf1. The second capacitor Cf2 is connected to the output of amplifier 212. The first capacitor Cf1 is an explicitly and deliberately included capacitor, distinct from any parasitic capacitance introduced by the first resistor Rf1.

[0058] A calibration controller 250A is capable of changing a circuit constant of the measuring device 200A according to the control data received by the data processing device 300. In this example, it is assumed that the data processing device 300 performs the optimization of the circuit constant in calibration mode and the final circuit constant is transmitted from the data processing device 300 to the interface 240.

[0059] In the Fig. In the example shown in Figure 6, the second resistor Rf2 is designed as a variable resistor that provides an adjustable circuit constant. A resistor control unit 252 and a decoder 254 of the calibration control 250 adjust the resistance value of the second resistor Rf2 according to a control instruction received from the data processing device 300. A digital potentiometer can be used as the second resistor Rf2.

[0060] The amplifier 212 is designed using a variable-gain feedback method. Such an amplifier offers a higher operating speed than conventional transimpedance amplifiers. Furthermore, this amplifier supports bandwidth control. The gain of the amplifier 212 is represented by "G". The gain G can be used as a circuit constant that can be changed. The gain G obtained during the calibration operation of the data processing device 300 is set for the amplifier 212 by means of the gain control unit 256 and the decoder 258.

[0061] The measuring device 200A can further comprise a third capacitor Cp2 and a third resistor Rp2. At least one of Cp2 and Rp2 can be used as an adjustable circuit constant. In this example, the third resistor Rp2 is designed as a variable resistor, such as a digital potentiometer or the like. A resistance value determined by the data processing device 300 is set for the third resistor Rp2 by means of a resistor control unit 260 and a decoder 262.

[0062] The voltage source 220 includes a waveform generator 222, a digital-to-analog converter 224, and a driver 226. In calibration mode, the waveform generator 222 produces waveform data at the calibration voltage Vcal(t). The digital-to-analog converter 224 converts the waveform data into an analog waveform signal. The driver 226 receives the output of the digital-to-analog converter 224 and applies the calibration voltage Vcal(t) to the electrode pair 106 and 108.

[0063] Fig. Figure 7 is a circuit diagram showing an exemplary embodiment of amplifier 212. Operational amplifiers marketed for microcurrent measurement are designed with a FET (field-effect transistor) or JFET (junction field-effect transistor) to suppress the bias current and keep it at a low level. However, such operational amplifiers have the trade-off of a narrow bandwidth compared to high-speed operational amplifiers such as a bi-CMOS or the like. To overcome this problem, amplifier 212 has a multi-stage structure with two or more operational amplifiers. In the first stage, an operational amplifier is used for microcurrent measurement. A high-speed amplifier is then used as the second and subsequent amplifier. This arrangement is capable of supporting a large bandwidth compared to a transimpedance amplifier configured as a single amplifier.

[0064] In particular, amplifier 212 includes a first operational amplifier OA1, a second operational amplifier OA2, and resistors Ri1 and Ri2. The first operational amplifier OA1, which forms the first stage, is designed as a FET or JFET. The second operational amplifier OA2 and the differential amplifier 218 are each designed as high-speed amplifiers, implemented as Bi-CMOS.

[0065] The first operational amplifier OA1, configured as the first stage, forms a voltage follower. The second operational amplifier OA2 and the resistors Ri1 and Ri2 form an inverting amplifier 216. The non-inverting input of the second operational amplifier OA2 corresponds to that shown in Fig. The non-inverting input terminal of amplifier 212 is shown in Figure 6. The output of the second operational amplifier OA2 corresponds to that shown in Figure 6. Fig. The output terminal of amplifier 212 is shown in Figure 6. The gain of amplifier 212 can be considered as the gain of inverting amplifier 216, which is represented by G = Ri2 / Ri1. Accordingly, if the gain G is to be configured as a variable gain, at least one of the resistors Ri1 and Ri2 can preferably be configured as a variable resistor.

[0066] The final stage of amplifier 212 is a differential amplifier (subtractor) 218. The differential amplifier 218 receives the output of the voltage follower 214 (the first stage) and the output of the inverting amplifier 216 (the second stage) and outputs the difference between them as a voltage signal Vs'. By using the differential amplifier 218, this arrangement is able to eliminate common-mode interference that occurs in the operational amplifier OA1 of the first stage and in the operational amplifier OA2 of the second stage.

[0067] The nanopore device 100 is shielded by a metal housing 110. A "Guard" amplifier 270 outputs a signal with the same electrical potential as that of the electrode 106 as a train protection signal and applies this signal to the shield housing 110. This provides shielding against the effects of noise. Furthermore, the electrode 106 and the amplifier 212 can be connected via a coaxial cable 112, and one outer conductor of the coaxial cable 112 can be driven by the "Guard" amplifier 270. This minimizes the effects of the parasitic capacitance Cs that occurs between the electrode 106 and ground, thereby improving signal distortion and the amplifier's bandwidth.

[0068] The calibration of the microparticle measurement system 1A is then described. The capacitor Cf1, which is provided as an additional capacitor for the transimpedance amplifier 210A, is designed to have a large capacitance in order to balance it with the RC product on the side of the nanopore device 100.

[0069] Furthermore, by providing resistor Rf2 and capacitor Cf2 as additional components and by adjusting the circuit constant to the condition Rf1 × Cf1 = Rf2 × Cf2, this arrangement is able to practically compensate for capacitor Cf1 from the perspective of the feedback circuit's transfer function. This arrangement drastically increases the bandwidth compared to a circuit where only the parasitic capacitance of resistor Rf1 is present.

[0070] Furthermore, this arrangement, as in Fig. Figure 7 illustrates a case where the amplifier 212 is configured in a multi-stage configuration with resistor Rf1 having a resistance value of 100 MΩ to increase the internal gain, capable of supporting a bandwidth of 1 MHz. By designing resistor Rf2 as a variable resistor, such as a digital potentiometer or the like, this arrangement is able to eliminate the effects of uncertain factors, such as parasitic capacitances, etc.

[0071] Furthermore, this arrangement is able to eliminate the capacitor Cp1 from the amplifier side by providing the resistor Rp2 and the capacitor Cp2 as additional components on the side of the nanopore device 100 such that they are arranged between the voltage source 220 and the nanopore device 100, and by adjusting the circuit constant by setting the product (Rp1 × Cp1), which is a variable value, such that it ensures the equation Rp1 × Cp1 = Rp2 × Cp2.

[0072] By providing this function, this arrangement enables the transimpedance amplifier 210A to have a maximum bandwidth and supports the stable operation of the nanopore device 100, where there are many uncertain factors.

[0073] Furthermore, this arrangement offers improved user-friendliness through the use of a digital potentiometer as a variable resistor and online control of the variable resistor. FIRST MODIFICATION

[0074] With reference to Fig. In section 7, an arrangement was described in which the amplifier 212 is configured as a two-stage unit. Other multi-stage configurations that use negative feedback and have three, four, or more amplifier stages can also be used. SECOND MODIFICATION

[0075] With reference to Fig. In section 7, an arrangement was described in which the first-stage amplifier is configured as a voltage follower with a gain g = 1. However, the present invention is not limited to such an arrangement. The gain can also be greater than 1. In this case, the "Guard" amplifier 270 can preferably be configured as an amplifier with a gain of 1 / g. THIRD MODIFICATION

[0076] In this embodiment, an arrangement is described in which a digitally controllable potentiometer is used for each of the multiple variable resistors. Furthermore, some or all of them can be configured as manually controlled variable resistors. In this case, the corresponding resistance value can be manually set by the user, based on the voltage waveform measured as the calibration voltage waveform. FOURTH MODIFICATION

[0077] In such a situation Fig. In the arrangement shown in Figure 7, a “Driving Guard” (270, 110) can be omitted in a case where the effects of the grounded capacitance Cs are negligible. FIFTH MODIFICATION

[0078] With such a Fig. In the arrangement shown in Figure 7, the differential amplifier 218 of the last stage can be omitted if the effects of common-mode interference occurring in the two operational amplifiers OA1 and OA2 are negligible. SIXTH MODIFICATION

[0079] The combinations of adjustable circuit constants described in this embodiment are for illustrative purposes only. Desired combinations can also be used. Other circuit constants, differing from those described above as examples, can also be configured as adjustable circuit constants. SEVENTH MODIFICATION

[0080] The present description has described a microparticle measuring device. However, the present invention is not limited to such an application. The present invention is also applicable to various types of measuring devices that support microcurrent measurement with a nanopore device, including, for example, DNA sequencers. EIGHTH MODIFICATION

[0081] In the embodiment described, an arrangement is used in which a square wave is used as the calibration voltage Vcal. However, the present invention is not limited to such an arrangement. A multi-tone signal, a swept sine wave, a pulse signal, etc., can also be used as the calibration voltage Vcal.

[0082] Although the preferred embodiments of the present invention have been described using specific terms, this description serves only for illustration.

Claims

[1] Measuring device (200, 200A, 200R) configured to measure a current signal for microparticle detection which flows through a nanopore device (100) with an opening (104) and an electrode pair (106, 108), wherein the measuring device (200, 200A, 200R) comprises the following: - a transimpedance amplifier (210, 210A) designed to convert the current signal into a voltage signal; and - a voltage source (220) configured to apply a DC bias voltage to the electrode pair (106, 108) in a normal measurement operating mode and to apply a calibration voltage, which has a predetermined waveform with an alternating current component, to the electrode pair (106, 108) in a calibration mode, wherein in normal measurement mode the nanopore device (100) contains particles (4) to be detected, and wherein in calibration mode the nanopore device (100) contains no particles (4) to be detected and at least one circuit constant of the measuring device (200) can be calibrated based on an output signal of the transimpedance amplifier (210, 210A) and the calibration voltage. [2] Measuring device (200, 200A, 200R) according to claim 1, wherein the calibration voltage has a rectangular waveform. [3] Measuring device (200, 200A, 200R) according to claim 1 or 2, wherein at least one previously described circuit constant is adjustable such that a waveform of the output signal of the transimpedance amplifier (210, 210A) approximates a waveform of the calibration voltage. [4] Measuring device (200, 200A, 200R) according to claim 1 or 2, wherein at least one previously described circuit constant is adjustable such that a transfer function defined with the waveform of the calibration voltage as its input and with the output signal of the transimpedance amplifier (210, 210A) as its output approximates an ideal characteristic function. [5] Measuring device (200, 200A, 200R) according to any one of claims 1 to 4, wherein the transimpedance amplifier (210, 210A) comprises the following: - an amplifier (212) arranged such that an inverting input terminal of it is connected to a first electrode of the electrode pair (106, 108) and a non-inverting input terminal of it receives a reference voltage; - a first resistor (Rf1) and a second resistor (Rf2) connected in series between the inverting input terminal of the amplifier (212) and an output terminal of the amplifier (212); - a first capacitor (Cf1) arranged in parallel with the first resistor (Rf1); and - a second capacitor (Cf2) which is connected to the output terminal of the amplifier (212). [6] Measuring device (200, 200A, 200R) according to claim 5, wherein at least one value of a resistance value of the second resistor (Rf2) and a capacitance value of the second capacitor (Cf2) is a variable value. [7] Measuring device (200, 200A, 200R) according to claim 5 or 6, wherein the amplifier (212) is configured to have variable gain. [8] Measuring device (200, 200A, 200R) according to one of claims 5 to 7, wherein at least one value of the first resistor (Rf1) and the first capacitor (Cf1) is designed to be variable. [9] Measuring device (200, 200A, 200R) according to any one of claims 1 to 8, further comprising: - a resistor (Rp1) and a capacitor (Cp1) that are arranged between the voltage source (220) and a second electrode of the electrode pair (106, 108). [10] Measuring device (200, 200A, 200R) according to claim 9, wherein a time constant provided by means of the resistor (Rp1) and the capacitor (Cp1) is adjustable. [11] Measuring device (200, 200A, 200R) according to any one of claims 1 to 10, further comprising: - a digitizer (230) designed to convert an output voltage of the transimpedance amplifier (210, 210A) into digital data (Ds); and - an interface (240) designed to transmit an output of the digitizer (230) externally. [12] Microparticle measurement system (1, 1A, 1R) comprising the following: - the measuring device (200, 200A, 200R) according to claim 11; and - a data processing device (300) connected to the interface (240) of the measuring device (200, 200A, 200R). [13] Microparticle measurement system (1, 1A, 1R) according to claim 12, wherein at least part of an operation to correct at least one circuit constant of the measuring device (200, 200A, 200R) is performed by means of the data processing device (300).

Images