Detection circuit and detection method of digital microfluidic system

Abstract

The present invention discloses a connection detection circuit and a connection detection method for a digital microfluidic system. The connection detection circuit includes: a row signal providing module, a column signal providing module, a voltage processing module, and a comparison and judgment module; the row signal providing module sequentially provides an on signal to the row control line; the column signal control module sequentially provides a detection signal to the column control line when the pixel unit of the current row is turned on, and the detection signal is an AC voltage signal with a preset amplitude and a preset frequency; the voltage processing module receives the detection signal after passing through the pixel unit and adjusts its voltage to a voltage range that can be sampled by the comparison and judgment module; the comparison and judgment module collects N data points corresponding to a first electrode, and determines the modulus based on the data, and compares it with a preset threshold value to judge the connection status and / or working status of the digital microfluidic system. Therefore, based on the structure of the existing pixel unit, a detection circuit and a detection method using an AC voltage signal as a detection signal are proposed.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of microfluidic systems, and in particular to a detection circuit and a detection method for a digital microfluidic system. Background Art

[0002] At present, in single-cell omics research, cell sorting is mainly based on microdroplet microfluidics technology (Microdroplet) or digital microfluidics (DMF) technology. Among them, digital microfluidics technology, also known as chip laboratory technology, can use the precise operation of droplets in the microliter to nanoliter range to achieve complex laboratory analysis; it has many advantages in the field of life science research, such as its high potential in portability and a significant reduction in the consumption of (rare or expensive) reagents or samples. One of the applications of digital microfluidics technology may include active digital microfluidic chips, which use switching elements such as thin-film transistors to achieve row and column encoding of electrode arrays, and control of any electrode in the electrode array through row control lines and column control lines. Compared with traditional passive digital microfluidic chips, this technology greatly reduces the number of connections, so the throughput is significantly improved.

[0003] When using an active digital microfluidic chip, it's crucial that each electrode is reliably connected to the drive circuit via its row and column control lines. Active digital microfluidic chips typically contain thousands or even tens of thousands of electrodes. A disconnect between a row or column control line and the drive circuit can cause the entire row or column of electrodes to fail, rendering the chip unable to complete experimental procedures due to functional loss. Therefore, it's crucial to perform a connection test before use to verify that all row and column control lines and electrodes are properly connected. Summary of the Invention

[0004] The embodiments of the present invention provide a detection circuit and a detection method for a digital microfluidic system, so as to realize detection of the digital microfluidic system by using a relatively simple circuit structure, and the method is convenient.

[0005] An embodiment of the present invention provides a detection circuit for a digital microfluidic system, wherein the digital microfluidic system includes row control lines, column control lines, and a pixel unit. The row control lines and the column control lines intersect to define a pixel region, and the pixel unit is located within the pixel region. The pixel unit includes a substrate, and a driving circuit layer, a first electrode layer, a first dielectric layer, a first hydrophobic layer, a liquid movement space, a second hydrophobic layer, and a second electrode layer sequentially stacked on one side of the substrate.

[0006] The detection circuit includes a row signal providing module, a column signal providing module, a voltage processing module and a comparison and judgment module;

[0007] The row signal providing module is electrically connected to each row control line and is used to sequentially provide an on signal to the row control line; the column signal control module is electrically connected to each column control line and is used to sequentially provide a detection signal to the column control line when the pixel unit of the current row is turned on, wherein the detection signal is an AC voltage signal with a preset amplitude and a preset frequency;

[0008] The comparison and judgment module is electrically connected to the second electrode layer through the voltage processing module; the voltage processing module is used to receive the detection signal after passing through the pixel unit and adjust its voltage to the voltage range that can be sampled by the comparison and judgment module; the comparison and judgment module is used to collect N data points corresponding to one of the first electrodes, and compare the module value determined based on the N data points with the preset threshold value to judge the connection status and / or working status of the digital microfluidic system; 128≤N≤2056 and N is an integer.

[0009] In one embodiment, the digital microfluidic system includes a driving circuit;

[0010] At least one of the row signal providing module, the column signal providing module and the comparison and judgment module is integrated with the driving circuit;

[0011] The driving circuit is used to provide the start signal and / or the detection signal to the pixel unit, and / or collect the data points and determine the connection status and / or working status of the digital microfluidic system.

[0012] In one embodiment, the comparison and judgment module includes an analog-to-digital conversion submodule, a Fourier transform submodule, a threshold storage submodule, and a threshold comparison submodule;

[0013] The analog-to-digital conversion submodule is used to collect N data points and transmit them to the Fourier transform submodule;

[0014] The Fourier transform submodule is used to perform an N-point fast Fourier transform based on the N data points, determine the modulus value at each frequency value, and select the main frequency modulus value or the maximum modulus value as the detection modulus value;

[0015] The threshold storage submodule is used to store the preset threshold;

[0016] The threshold comparison submodule is used to retrieve and compare the preset threshold and the detection module value; and judge the connection status and / or working status of the digital microfluidic system according to the comparison result.

[0017] In one embodiment, the voltage processing module includes a first voltage divider submodule, a follower submodule, an in-phase adder submodule, and a second voltage divider submodule;

[0018] The second electrode layer, the first end of the first voltage divider submodule and an input end of the follower submodule are all electrically connected to a first node, and the second end of the first voltage divider submodule is grounded; the output end and a power supply end of the follower submodule are both connected to the same input end of the in-phase adder submodule; the output end of the in-phase adder submodule is connected to an input end of the second voltage divider submodule, the other input end of the second voltage divider submodule is grounded, and the output end of the voltage divider submodule is electrically connected to the comparison and judgment module.

[0019] In one embodiment, the preset threshold is determined using the following formula:

[0020] Preset threshold = (connected module value min + unconnected module value max) / 2;

[0021] Among them, the connected modulus value min represents the minimum value of the modulus values ​​determined by the comparison and judgment module when all the first electrodes are connected normally in the digital microfluidic system; the unconnected modulus value max represents the maximum value of the modulus values ​​determined by the comparison and judgment module when all the first electrodes are not connected in the digital microfluidic system.

[0022] The embodiment of the present invention further provides a detection method for a digital microfluidic system, which is performed by applying any of the detection circuits provided above. The detection method includes:

[0023] The row signal providing module sequentially provides an enable signal to the row control line;

[0024] The column signal control module provides a detection signal to the column control line in sequence when the pixel unit of the current row is turned on. The detection signal is an AC voltage signal with a preset amplitude and a preset frequency;

[0025] The voltage processing module receives the detection signal after passing through the pixel unit and adjusts its voltage to a voltage range that can be sampled by the comparison and judgment module;

[0026] The comparison and judgment module collects N data points corresponding to the same first electrode in sequence, and compares the module value determined according to the N data points with a preset threshold value to judge the connection status and / or working status of the digital microfluidic system.

[0027] In one embodiment, the detection method further includes determining a preset amplitude and a preset frequency; specifically, including:

[0028] The column signal control module provides a plurality of AC voltage signals with different voltage values ​​and frequency values;

[0029] The comparison and judgment module respectively collects the module values ​​of whether there is an electrical connection, calculates the module value difference of whether there is an electrical connection under different AC voltage signals, and selects the AC voltage signal corresponding to the maximum module value difference as the detection signal.

[0030] In one embodiment, the detection method further includes determining the preset threshold; specifically including:

[0031] Determine in the digital microfluidic system that when all the first electrodes are connected normally, the minimum value among the moduli is a connected moduli value min;

[0032] Determining, in the digital microfluidic system, that when all the first electrodes are not connected, the maximum value among the moduli is a no-connection moduli value max;

[0033] The preset threshold is determined according to the connected modulus value min, the disconnected modulus value max, and the formula "preset threshold=(connected modulus value min+disconnected modulus value max) / 2".

[0034] In one embodiment, the AC voltage signal includes a sine wave signal, a square wave signal, or a triangle wave signal.

[0035] In one embodiment, the comparison and judgment module includes an analog-to-digital conversion submodule, a Fourier transform submodule, a threshold storage submodule, and a threshold comparison submodule; the comparison and judgment module sequentially collects N data points corresponding to the same first electrode, and compares the modulus determined based on the N data points with a preset threshold value, and judges the connection status and / or working status of the digital microfluidic system including:

[0036] The analog-to-digital conversion submodule collects N data points and transmits them to the Fourier transform submodule;

[0037] The Fourier transform submodule performs an N-point fast Fourier transform based on the N data points, determines the modulus value at each frequency point, and selects the main frequency modulus value or the maximum modulus value as the detection modulus value;

[0038] The threshold storage submodule stores the preset threshold;

[0039] The threshold comparison submodule retrieves the preset threshold and the detection module value, and compares them; and determines the connection status and / or working status of the digital microfluidic system according to the comparison result.

[0040] The detection circuit of the digital microfluidic system provided by an embodiment of the present invention includes a row signal providing module, a column signal providing module, a voltage processing module and a comparison and judgment module; the row signal providing module is electrically connected to each of the row control lines, and is used to provide an open signal to the row control line in turn; the column signal control module is electrically connected to each of the column control lines, and is used to provide a detection signal to the column control line in turn when the pixel unit of the current row is turned on, and the detection signal is an AC voltage signal with a preset amplitude and a preset frequency; the comparison and judgment module is electrically connected to the second electrode layer through the voltage processing module; the voltage processing module is used to receive the detection signal after passing through the pixel unit, and adjust its voltage to a voltage range that can be sampled by the comparison and judgment module; the comparison and judgment module is used to collect N data points corresponding to one of the first electrodes, and compare the modulus determined according to the N data points with a preset threshold value to judge the connection status and / or working status of the digital microfluidic system; 128≤N≤2056 and N is an integer. Therefore, based on the structure of the existing digital microfluidic system pixel unit, a detection circuit and method using an AC voltage signal as a detection signal can be provided, and the circuit structure is relatively simple, and the method is simple and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 Schematic diagram of the structure of a digital microfluidic system provided by an embodiment of the present invention;

[0043] Figure 2 1 is a schematic cross-sectional structural diagram of a pixel unit of a 1T1C active digital microfluidic chip in a digital microfluidic system provided by an embodiment of the present invention;

[0044] Figure 3 1 is a schematic structural diagram of a detection circuit of a digital microfluidic system provided by an embodiment of the present invention;

[0045] Figure 4 yes Figure 3 Schematic diagram of the local structure of the detection circuit;

[0046] Figure 5 Schematic diagram of an equivalent electrical model of a digital microfluidic system when the connection is normal during operation of the detection circuit provided by an embodiment of the present invention;

[0047] Figure 6This is a schematic structural diagram of a voltage processing module and a comparison and judgment module provided by an embodiment of the present invention;

[0048] Figure 7 It is a flow chart of a detection method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0050] Based on the technical problems in the background technology, in the related technologies, for example, patent CN108291884A of Sharp Life Sciences Co., Ltd. introduces a method for detecting the impedance above any electrode to determine the electrode state. This method realizes the impedance detection above the electrode by adding an impedance sensor unit consisting of 3 transistors and 1 capacitor to each electrode.

[0051] The main drawback of this approach is that the addition of an impedance sensor unit consisting of three transistors and a capacitor to each electrode makes the manufacturing process of active digital microfluidic chips, which typically contain thousands or even tens of thousands of electrodes, extremely complex and costly. Failure of any transistor will cause the function of that electrode to cease, compromising the functionality of the entire chip. The complex impedance sensor unit also places an additional burden on the driver circuitry, increasing its complexity.

[0052] This invention introduces a detection circuit and method for a pixel driver circuit based on an active digital microfluidic chip, such as a 1T1C (one transistor, one capacitor) circuit. This circuit and method eliminates the need for adding dedicated impedance sensors to the electrodes within the pixel unit and instead detects connection status simply by applying an AC voltage signal to the electrodes. The circuit and method demonstrate a simple structure, high reliability, strong scalability, and low equipment cost.

[0053] The following is combined with Figure 1-Figure 7 , the detection circuit and detection method of the digital microfluidic system provided by the embodiment of the present invention are exemplarily described.

[0054] refer to Figure 1 and Figure 2The digital microfluidic system 10 includes row control lines 110, column control lines 120 and pixel units 130. The row control lines 110 and the column control lines 120 intersect to define a pixel area, and the pixel unit 130 is located in the pixel area; the pixel unit 130 includes a substrate 300, and a driving circuit layer 310, a first electrode layer 320, a first dielectric layer 330, a first hydrophobic layer 340, a liquid movement space 350, a second hydrophobic layer 360 and a second electrode layer 370 stacked in sequence on one side of the substrate 300.

[0055] The row control line 110 can transmit a switch control signal to a row of connected pixel units 130 to control whether the pixel units 130 in the current row are in an on or off state. The column control line 120 is used to transmit a voltage control signal to the turned-on pixel units 130 to control the electrode potential difference in the liquid movement space 350 of the current pixel unit 130 in the current row, thereby controlling the movement of liquid in the liquid movement space 350.

[0056] It should be noted that Figure 1 Only two row control lines 110 are shown as examples, which are respectively represented by the first row control line 1101 and the second row control line 1102; two column control lines 120 are respectively represented by the first column control line 1201 and the second column control line 1202; four pixel units, each including its own first electrode layer (respectively represented by 3201, 3202, 3203 and 3204), switching elements (respectively represented by 171, 172, 173 and 174) and storage capacitor 18 (hereinafter also referred to as "capacitor 18"). This is only a partial structural diagram of the digital microfluidic system 10. In other embodiments, the number and arrangement of the row control lines 110, column control lines 120 and pixel units 130 can be set according to the requirements of the digital microfluidic system 10, and the embodiment of the present invention is not limited to this.

[0057] For example, refer to Figure 2 A switching element, such as a transistor structure, is formed in the driving circuit layer 310, which may include a channel 1, a gate 2, a drain 3 and a source 4. The pixel unit 130 may also include a metal layer 311, other dielectric layers (shown as 331 and 332 respectively), and a top cover 380; wherein, the liquid movement space 350, the second hydrophobic layer 360, the second electrode layer 370 and the top cover 380 together constitute an active digital microfluidic chip top cover 390.

[0058] Combine Figure 1In the 2*2 active digital microfluidic electrode array shown in FIG, the gate of the transistor is connected to the row control line 110, the source is connected to the column control line 120, the drain is connected to one end of the capacitor 18, and the other end of the capacitor 18 is connected to the common voltage by the control line 21; at the same time, the first electrode 6 is connected to the drain of the transistor.

[0059] In other embodiments, the pixel unit 130 may further include other film layer structures known to those skilled in the art, which is not limited in the embodiment of the present invention.

[0060] exist Figure 1 and Figure 2 Based on the reference Figure 3 and Figure 4 The detection circuit 20 includes a row signal providing module 210, a column signal providing module 220, a voltage processing module 230 and a comparison and judgment module 240; the row signal providing module 210 is electrically connected to each row control line 110, and is used to sequentially provide an opening signal to the row control line 110; the column signal control module 220 is electrically connected to each column control line 120, and is used to sequentially provide a detection signal (hereinafter also referred to as an "excitation signal") to the column control line 120 when the pixel unit 130 of the current row is turned on. The detection signal is an AC signal with a preset amplitude and a preset frequency. voltage signal; the comparison and judgment module 240 is electrically connected to the second electrode layer 370 through the voltage processing module 230; the voltage processing module 230 is used to receive the detection signal after passing through the pixel unit 130, and adjust its voltage to a voltage range that can be sampled by the comparison and judgment module 240; the comparison and judgment module 240 is used to collect N data points corresponding to a first electrode 320, and compare the modulus determined based on the N data points with a preset threshold value to determine the connection status and / or working status of the digital microfluidic system 10; 128≤N≤2056 and N is an integer.

[0061] This enables pixel-by-pixel detection. For example, the connection status may include whether the connection between the first electrode and the drive circuit, the row control line connection, and the column control line connection in the digital microfluidic system are normal; the operating status may include achieving the positioning of a droplet in a pixel unit, detecting the concentration of a chemical solution in a pixel unit, and monitoring a chemical reaction process. The following uses connection detection as an example for exemplary description.

[0062] For example, combined Figure 1 and Figure 4 , the connection detection principle is illustrated as follows:

[0063] First, the first row control line 1101 is turned on, turning on the transistors 171 and 172 in the first row. An AC voltage signal with a preset amplitude and frequency, such as a sine wave signal, a square wave signal, or a triangular wave signal, is applied to the first column control line 1201. The AC voltage signal is transmitted to the first electrode 3201 through the transistor 171, generating the AC voltage signal at the first electrode 3201. The method for determining the amplitude and frequency of the AC voltage signal will be described below.

[0064] If the first electrode 3201 is connected normally and the first row control line 1101 and the first column control line 1201 are working normally, the equivalent electrical model of the first electrode 3201 and the upper cover 390 is as follows: Figure 5 The capacitor 22 is an equivalent capacitor formed between the first electrode 3201 and the upper cover 390, and includes the first electrode 3201, the first dielectric layer 10, the first hydrophobic layer 340, the liquid moving space 350, the second hydrophobic layer 360 and the second electrode layer 370 (also called the conductive layer 370). The conductive layer 370 is connected to the Figure 6 The voltage processing circuit 230 is shown connected.

[0065] The voltage processing circuit 230 collects signals related to the connection status of the digital microfluidic system through the first node N1 and transmits them to the comparison and judgment circuit for processing to determine the connection status and / or working status of the circuit related to the first electrode 320. The specific processing and judgment methods are described below.

[0066] In this way, the connection detection of the electrodes in the first row and the first column is completed.

[0067] Thereafter, the first row control line 1101 is kept providing an on signal, and an AC voltage signal of a preset amplitude and a preset frequency is applied to the second column control line 1202 . The AC voltage signal is transmitted to the first electrode 3202 through the transistor 172 , so that the AC voltage signal is generated on the first electrode 3202 .

[0068] Repeat the above steps to determine the connection status of the first electrode 3202 in the first row and second column.

[0069] Then, the first row control line 1101 is turned off and the second row control line 1102 is turned on, thereby turning on the second row transistors 173 and 174. An AC voltage signal with a preset amplitude and a preset frequency is applied to the first column control line 1201. The AC voltage signal is transmitted to the first electrode 3203 through the transistor 173, so that the AC voltage signal is generated on the first electrode 3203.

[0070] Repeat the above steps to determine the connection status of the first electrode 3203 in the second row and first column.

[0071] Thereafter, the second row control line 1102 is kept on providing an on signal, and an AC voltage signal with a preset amplitude and a preset frequency is applied to the column control line 1204 . The AC voltage signal is transmitted to the first electrode 3204 through the transistor 174 , so that the AC voltage signal is generated on the first electrode 3204 .

[0072] Repeat the above steps to determine the connection status of the first electrode 3204 in the second row and second column.

[0073] At this point, the row-by-row and column-by-column scanning detection of all electrodes is completed, and a detection result can be generated. The detection result can include detection information such as the module value and connection status of all electrodes.

[0074] In one embodiment, continue to refer to Figure 4 The digital microfluidic system includes a driving circuit (shown as a row driving circuit and a column driving circuit); at least one of a row signal providing module, a column signal providing module, and a comparison and judgment module is integrated with the driving circuit; the driving circuit is used to provide an open signal and / or a detection signal to the pixel unit, and / or collect data points and judge the connection status and / or working status of the digital microfluidic system.

[0075] Exemplarily, the row signal providing module can reuse the row driving circuit, such as the shift register circuit; the column signal providing module can reuse the column driving circuit, such as the voltage signal providing module; the analog-to-digital converter in the driving circuit can collect data points and transmit them to the digital signal processing circuit for digital signal processing to obtain the analog value of each first electrode and determine its connection status.

[0076] Thus, the detection circuit can be simplified, that is, electrode detection can be achieved using a simple circuit structure. The method is simple and fast, with little interference and high reliability.

[0077] In one embodiment, referring to Figure 6 The comparison and judgment module 240 includes an analog-to-digital conversion submodule 241, a Fourier transform submodule 242, a threshold storage submodule 243 and a threshold comparison submodule 244; the analog-to-digital conversion submodule 241 is used to collect N data points and transmit them to the Fourier transform submodule 242; the Fourier transform submodule 242 is used to perform N-point fast Fourier transform based on the N data points, determine the modulus value at each frequency point, and select the main frequency modulus value or the maximum modulus value as the detection modulus value; the threshold storage submodule 243 is used to store the preset threshold; the threshold comparison submodule 244 is used to call the preset threshold and the detection modulus value, and compare them; the connection status and / or working status of the digital microfluidic system are judged according to the comparison results.

[0078] The analog-to-digital conversion submodule 241 (eg, ADC) collects N data points corresponding to the same first electrode, where the value of N ranges from 128 to 2056. For the same first electrode, N can be any value between 128 and 2056.

[0079] Among them, the Fourier transform submodule 242 (for example, inside the driving circuit) performs an N-point Fast Fourier Transform (FFT) based on the N data points. Here, FFT can convert the time domain signal into a frequency domain signal. The signal usually contains noise signals of various frequencies, which interfere with the effective signal and make it difficult to directly extract effective information from the time domain signal. Through FFT, the time domain signal can be converted into a frequency domain signal. Since the noise signal and the effective signal have different frequencies, the noise signal and the effective signal can be separated. The frequency of the effective signal can be directly selected to extract the relevant information of the effective signal. Therefore, FFT can also be regarded as a process of filtering noise. Because each point after FFT corresponds to a frequency point (increased in units of fundamental frequency), the modulus value of this point (the square root of the sum of the squares of the real part and the imaginary part) is the modulus value at the frequency value of this frequency point. In order to reduce noise interference, the modulus value of the point equal to the main frequency can be directly determined as the detection modulus value (when there is a connection, the modulus value of this point is actually the point with the largest modulus value among all points); or the maximum modulus value can be determined as the detection modulus value, and the detection modulus value is transmitted to the threshold comparison submodule 244 to prepare for comparison with the preset threshold.

[0080] By comparing the module values ​​of whether or not there is a connection, a preset threshold can be set. Exemplarily, the preset threshold is stored in the threshold storage submodule 243, and the value of the preset threshold depends on the voltage (ie, amplitude) and frequency of the excitation signal.

[0081] In one embodiment, the preset threshold is determined using the following formula:

[0082] Preset threshold = (connected module value min + unconnected module value max) / 2;

[0083] Among them, the connected modulus value min represents the minimum value of the modulus values ​​determined by the comparison and judgment module when all the first electrodes are connected normally in the digital microfluidic system; the unconnected modulus value max represents the maximum value of the modulus values ​​determined by the comparison and judgment module when all the first electrodes are not connected in the digital microfluidic system.

[0084] In other implementations, other methods may be used to determine the preset threshold, which is not limited in this embodiment of the present invention.

[0085] The threshold comparison module 244 compares the detection module value with a preset threshold value, and determines the connection state of the first electrode according to the relative magnitudes of the two.

[0086] Exemplarily, if the detection module value is equal to or greater than a preset threshold, it is determined that the connection is normal; if the detection module value is less than the preset threshold, it is determined that the connection is abnormal.

[0087] In this way, according to the comparison result between the detection module value and the preset threshold value, it can be determined whether the first electrode is connected to the driving circuit, and whether the row control line and the column control line are working normally.

[0088] In one embodiment, continue to refer to Figure 6 The voltage processing module 230 includes a first voltage divider submodule 231, a follower submodule 232, an in-phase adder submodule 233 and a second voltage divider submodule 234; the second electrode layer 370, the first end of the first voltage divider submodule 231 and an input end (“+”) of the follower submodule 232 are all electrically connected to the first node N1, and the second end of the first voltage divider submodule 231 is grounded GND; the output end and a power supply end (shown as VCC_3.3V) of the follower submodule 232 are both connected to the same input end (“-”) of the in-phase adder submodule 233; the output end of the in-phase adder submodule 233 is connected to an input end of the second voltage divider submodule 234, the other input end (“+”) of the second voltage divider submodule 234 is grounded, and the output end of the voltage divider submodule 234 is electrically connected to the comparison and judgment module 240.

[0089] Exemplarily, the first voltage divider submodule 231 may include a seventh resistor R7, the follower submodule 232 may include an operational amplifier and a first resistor R1, the in-phase adder submodule 233 may include an operational amplifier, and at the same time, the power supply end passes through the second resistor R2 and is connected to the same input end of the in-phase adder submodule 233 as the output end of the follower submodule 232, the other input end of the in-phase adder submodule 233 is grounded through the third resistor R3, and the second voltage divider submodule 234 includes a fifth resistor R5 and a sixth resistor R6.

[0090] On this basis, after the detection signal passes through the first electrode, it passes through the seventh resistor R7 to the ground GND. The main function of the seventh resistor R7 is voltage division. When the first electrode is not connected to the driving circuit (that is, in an open circuit state), the impedance between the driving circuit and the conductive layer is approximately infinite; when the first electrode is connected to the driving circuit, the impedance between the first electrode and the top cover is equivalent to the capacitor 22 (such as Figure 5), which is much smaller than the impedance value when the circuit is disconnected. Therefore, the voltage values ​​collected by the voltage processing module 230 through the connecting line 23 are different depending on whether the first electrode is connected to the driving circuit or not. Since the load carrying capacity of the voltage after voltage division is poor, in order to improve its load carrying capacity, the voltage is passed through a follower submodule 232 composed of an operational amplifier after voltage division; the output voltage of the follower submodule 232 has a negative voltage. In order to allow the analog-to-digital conversion submodule 241 to normally collect data points, the output end of the follower submodule 232 is electrically connected to a non-inverting adder submodule 233. The other input of the non-inverting adder submodule 233 can be the voltage from the driving circuit, such as 3.3V. Afterwards, it passes through a voltage divider circuit ( Figure 6 The second voltage divider submodule 234, that is, the voltage divider circuit composed of the fifth resistor R5 and the sixth resistor R6, adjusts the voltage to be within the voltage range sampled by the ADC (for example, which can be integrated in the driving circuit) and is collected by the ADC.

[0091] For example, in both cases of connection and no connection, the voltages of the nodes from the first node N1 to the ADC detection terminal may be as follows:

[0092] When connected: first node N1: ±2V 10kHz square wave, R1: ±2V 10kHz square wave, R5: 1.3-5.3V 10kHz square wave, ADC detection: 0.65-2.65V 10kHz square wave;

[0093] In the case of no connection: first node N1: 0V, R1: 3.3V, R5: 3.3V, ADC detection: 1.65V.

[0094] In other implementations, the potential of each node may be different according to the different detection signals, which is not limited in the embodiment of the present invention.

[0095] It should be noted that the presence or absence of a connection between the first electrode and the drive circuit is unrelated to the signal load capacity. The divided AC voltage signal, after passing through the voltage follower formed by the first-stage op amp, has an increased load capacity. Subsequent signal division does not distort the signal, facilitating ADC acquisition. Furthermore, the potential difference at the first node N1 changes the modulus frequency of the AC voltage signal. The voltage processing module 230 raises the voltage of the AC voltage signal above 0V to meet ADC sampling requirements.

[0096] On the basis of the above-mentioned embodiments, an embodiment of the present invention further proposes a detection method for a digital microfluidic system. The detection method can be executed by applying any detection circuit provided in the above-mentioned embodiments. Therefore, the detection method also has the beneficial effects of the detection circuit in the above-mentioned embodiments. The similarities can be understood by referring to the explanation of the detection circuit in the above text, and will not be repeated below.

[0097] For example, refer to Figure 5 , the detection method includes:

[0098] S510 , the row signal providing module sequentially provides an enable signal to the row control lines.

[0099] In this way, the transistors of a row of pixel units electrically connected to the row control line are all turned on, preparing for S520 .

[0100] S520 , when the pixel units in the current row are turned on, the column signal control module sequentially provides detection signals to the column control lines, where the detection signals are AC voltage signals with a preset amplitude and a preset frequency.

[0101] In this way, the detection signal can be provided to the first electrode of the pixel unit one by one, so as to realize the electrode detection by combining the following S530 and S240 executed by the voltage processing module and the price comparison judgment module.

[0102] S530: The voltage processing module receives the detection signal after passing through the pixel unit, and adjusts the voltage thereof to a voltage range that can be sampled by the comparison and judgment module.

[0103] In this step, the voltage processing module adjusts the voltage signal collected at its input terminal (ie, the first node N1) to a voltage signal that can be sampled by the subsequent comparison and judgment module, in preparation for the subsequent comparison and judgment.

[0104] S540: The comparison and judgment module collects N data points corresponding to the same first electrode in sequence, and compares the module value determined according to the N data points with a preset threshold value to judge the connection status and / or working status of the digital microfluidic system.

[0105] In this way, the connection status of the electrodes can be detected one by one.

[0106] In one embodiment, when executing Figure 5 Before the steps of the detection method shown, the detection method further includes determining a preset amplitude and a preset frequency of the detection signal; specifically, it may include:

[0107] Step 1: The column signal control module provides a plurality of AC voltage signals with different voltage values ​​and frequency values.

[0108] Step 2: The comparison and judgment module collects the module values ​​of whether there is electrical connection respectively, calculates the module value difference of whether there is electrical connection under different AC voltage signals, and selects the AC voltage signal corresponding to the maximum module value difference as the detection signal.

[0109] In this way, in order to select a better voltage and frequency for the detection signal, AC voltage signals with multiple voltage values ​​and multiple frequency values ​​can be selected, and the module values ​​of whether there is an electrical connection or not can be collected respectively. The module value difference of whether there is an electrical connection at different voltages and different frequencies can be calculated, and the voltage and frequency with the largest module value difference of whether there is a connection or not can be selected as the excitation signal for detection, so as to effectively distinguish between normal connection and circuit breakage.

[0110] In one embodiment, when executing Figure 5 Before the steps of the detection method shown, the detection method also includes determining a preset threshold; specifically including:

[0111] Step 1: Determine in the digital microfluidic system that when all first electrodes are connected normally, the minimum value among the moduli is the connected moduli value min.

[0112] Step 2: Determine in the digital microfluidic system that when all first electrodes are not connected, the maximum value among the moduli is the disconnected moduli value max.

[0113] Step 3: Determine the preset threshold value according to the connected modulus value min, the disconnected modulus value max, and the formula "preset threshold value = (connected modulus value min + disconnected modulus value max) / 2".

[0114] In this way, the comparison and judgment module determines the basis for judging whether there is a connection based on the detection module value.

[0115] In one embodiment, the AC voltage signal includes a sine wave signal, a square wave signal, or a triangle wave signal.

[0116] In other implementations, the AC voltage signal may also be an AC signal with other waveforms known to those skilled in the art, which is neither detailed nor limited in the embodiments of the present invention.

[0117] In one embodiment, the comparison and judgment module includes an analog-to-digital conversion submodule, a Fourier transform submodule, a threshold storage submodule, and a threshold comparison submodule. Based on this, Figure 5 The S540 may include:

[0118] Step 1: The analog-to-digital conversion submodule collects N data points and transmits them to the Fourier transform submodule.

[0119] Step 2: The Fourier transform submodule performs N-point fast Fourier transform based on N data points, determines the modulus value at each frequency value, and selects the main frequency modulus value or the maximum modulus value as the detection modulus value.

[0120] Step 3: The threshold storage submodule stores the preset threshold.

[0121] Step 4: The threshold comparison submodule retrieves the preset threshold value and the detection module value and compares them; the connection status and / or working status of the digital microfluidic system is judged based on the comparison result.

[0122] In other implementations, step three, ie, the threshold storage submodule storing the preset threshold, may also be performed before step one or step two, which is not limited in this embodiment of the present invention.

[0123] The beneficial effects of the detection circuit and detection method of the digital microfluidic system provided by the embodiments of the present invention include at least:

[0124] 1) Provide a detection solution for an active digital microfluidic electrode array based on an existing pixel driving circuit (e.g., 1T1C), which does not require an additional impedance sensor unit and has a simple circuit structure and strong versatility;

[0125] 2) The excitation signal can be an AC voltage signal with waveforms such as sine wave, square wave, triangle wave, etc., which is easy to implement;

[0126] 3) By coordinating row and column control lines to detect all electrodes, the connection detection of the entire electrode array can be quickly achieved in a short time;

[0127] 4) Using the AC voltage signal with the largest difference in modulus between electrical connection and non-electrical connection as the excitation signal facilitates effective detection. At the same time, the amplitude and frequency of the excitation AC voltage signal can be adjusted according to different chips, which is conducive to achieving better detection results.

[0128] 5) After collecting the voltage, perform FFT algorithm and select the point equal to the main frequency as the judgment point; or select the data point with the largest modulus value after FFT as the judgment basis, which can effectively filter out noise interference;

[0129] 6) The above method of setting a preset threshold value for whether a connection exists facilitates effective detection; at the same time, automatic determination of whether a connection exists can be achieved by setting a preset threshold value;

[0130] 7) This detection method is highly versatile and can be applied to various arrangements of active digital microfluidic chip electrode arrays;

[0131] 8) In addition to detecting whether the connection between the microfluidic chip and the driving circuit is normal, the detection circuit and detection method proposed in this invention can also be used to detect droplet positioning, distinguish chemical solutions of different concentrations, and monitor the progress of chemical reactions.

[0132] 9) This detection method has strong anti-interference ability and the detection results are highly reliable.

[0133] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A detection circuit for a digital microfluidic system, characterized in that: The digital microfluidic system includes row control lines, column control lines, and pixel units. The row control lines and the column control lines intersect to define a pixel area, and the pixel unit is located within the pixel area. The pixel unit includes a substrate, and a driving circuit layer, a first electrode layer, a first dielectric layer, a first hydrophobic layer, a liquid movement space, a second hydrophobic layer, and a second electrode layer sequentially stacked on one side of the substrate. The detection circuit includes a row signal providing module, a column signal providing module, a voltage processing module and a comparison and judgment module; The row signal providing module is electrically connected to each row control line and is used to sequentially provide an on signal to the row control line; the column signal control module is electrically connected to each column control line and is used to sequentially provide a detection signal to the column control line when the pixel unit of the current row is turned on, wherein the detection signal is an AC voltage signal with a preset amplitude and a preset frequency; The comparison and judgment module is electrically connected to the second electrode layer through the voltage processing module; the voltage processing module is used to receive the detection signal after passing through the pixel unit and adjust its voltage to the voltage range that can be sampled by the comparison and judgment module; the comparison and judgment module is used to collect N data points corresponding to a first electrode, and compare the module value determined based on the N data points with a preset threshold to determine the connection status and / or working status of the digital microfluidic system; 128≤N≤2056 and N is an integer.

2. The detection circuit according to claim 1, characterized in that The digital microfluidic system includes a driving circuit; At least one of the row signal providing module, the column signal providing module and the comparison and judgment module is integrated with the driving circuit; The driving circuit is used to provide the start signal and / or the detection signal to the pixel unit, and / or collect the data points and determine the connection status and / or working status of the digital microfluidic system.

3. The detection circuit according to claim 1 or 2, characterized in that: The comparison and judgment module includes an analog-to-digital conversion submodule, a Fourier transform submodule, a threshold storage submodule and a threshold comparison submodule; The analog-to-digital conversion submodule is used to collect N data points and transmit them to the Fourier transform submodule; The Fourier transform submodule is used to perform an N-point fast Fourier transform based on the N data points, determine the modulus value at each frequency value, and select the main frequency modulus value or the maximum modulus value as the detection modulus value; The threshold storage submodule is used to store the preset threshold; The threshold comparison submodule is used to retrieve and compare the preset threshold and the detection module value; and judge the connection status and / or working status of the digital microfluidic system according to the comparison result.

4. The detection circuit according to claim 1, characterized in that: The voltage processing module includes a first voltage divider submodule, a follower submodule, an in-phase adder submodule and a second voltage divider submodule; The second electrode layer, the first end of the first voltage divider submodule and an input end of the follower submodule are all electrically connected to a first node, and the second end of the first voltage divider submodule is grounded; the output end and a power supply end of the follower submodule are both connected to the same input end of the in-phase adder submodule; the output end of the in-phase adder submodule is connected to an input end of the second voltage divider submodule, the other input end of the second voltage divider submodule is grounded, and the output end of the voltage divider submodule is electrically connected to the comparison and judgment module.

5. The detection circuit according to claim 1, wherein: The preset threshold is determined by the following formula: Preset threshold = (connected module value min + unconnected module value max) / 2; Among them, the connected modulus value min represents the minimum value of the modulus values ​​determined by the comparison and judgment module when all the first electrodes are connected normally in the digital microfluidic system; the unconnected modulus value max represents the maximum value of the modulus values ​​determined by the comparison and judgment module when all the first electrodes are not connected in the digital microfluidic system.

6. A detection method for a digital microfluidic system, characterized in that: The detection method is performed by applying the detection circuit according to any one of claims 1 to 5, and includes: The row signal providing module sequentially provides an enable signal to the row control line; The column signal control module provides a detection signal to the column control line in sequence when the pixel unit of the current row is turned on. The detection signal is an AC voltage signal with a preset amplitude and a preset frequency; The voltage processing module receives the detection signal after passing through the pixel unit and adjusts its voltage to a voltage range that can be sampled by the comparison and judgment module; The comparison and judgment module collects N data points corresponding to the same first electrode in sequence, and compares the module value determined according to the N data points with a preset threshold value to judge the connection status and / or working status of the digital microfluidic system.

7. The detection method according to claim 6, characterized in that It also includes determining a preset amplitude and a preset frequency; specifically including: The column signal control module provides a plurality of AC voltage signals with different voltage values ​​and frequency values; The comparison and judgment module respectively collects the module values ​​of whether there is an electrical connection, calculates the module value difference of whether there is an electrical connection under different AC voltage signals, and selects the AC voltage signal corresponding to the maximum module value difference as the detection signal.

8. The detection method according to claim 6, characterized in that The method also includes determining the preset threshold value; specifically including: Determine in the digital microfluidic system that when all the first electrodes are connected normally, the minimum value among the moduli is a connected moduli value min; Determining, in the digital microfluidic system, that when all the first electrodes are not connected, the maximum value among the moduli is a no-connection moduli value max; The preset threshold is determined according to the connected modulus value min, the disconnected modulus value max, and the formula "preset threshold=(connected modulus value min+disconnected modulus value max) / 2".

9. The detection method according to claim 6, characterized in that The AC voltage signal includes a sine wave signal, a square wave signal or a triangle wave signal.

10. The detection method according to claim 6, characterized in that: The comparison and judgment module includes an analog-to-digital conversion submodule, a Fourier transform submodule, a threshold storage submodule, and a threshold comparison submodule; the comparison and judgment module sequentially collects N data points corresponding to the same first electrode, and compares the modulus determined according to the N data points with a preset threshold value, and judges the connection status and / or working status of the digital microfluidic system including: The analog-to-digital conversion submodule collects N data points and transmits them to the Fourier transform submodule; The Fourier transform submodule performs an N-point fast Fourier transform based on the N data points, determines the modulus value at each frequency point, and selects the main frequency modulus value or the maximum modulus value as the detection modulus value; The threshold storage submodule stores the preset threshold; The threshold comparison submodule retrieves the preset threshold and the detection module value, and compares them; and determines the connection status and / or working status of the digital microfluidic system according to the comparison result.

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