Pixel circuit, microfluidic chip and method of using the same

Abstract

The application discloses a pixel circuit suitable for a micro-fluidic chip adopting an active pixel array, comprising: an input end configured to input a voltage to a receiving end; the receiving end is electrically connected with a pixel electrode and outputs a voltage; a control end configured as a first TFT switch for controlling the electrical connection between the input end and the output end. The application can detect the electrical impedance of each pixel in the AM array micro-fluidic chip, and the detection scale is larger than that of the traditional PM chip, and the application is more practical; through the electrical impedance detection of the pixel, the application can distinguish the types of the droplets on the pixel electrode, and further realizes the detection of the position and moving state of the droplets in the micro-fluidic chip.

Description

Technical Field

[0001] This invention relates to the field of microfluidics, and more specifically, to a pixel circuit, a microfluidic chip, and a method of using the same. Background Technology

[0002] Currently, impedance detection methods used in microfluidic chips are mainly for passive matrix (PM) arrays. In a PM, each pixel has two drive signals directly connected to the external circuitry, making impedance detection relatively convenient. However, due to the large number of signal lines, the scale of a PM drive array is limited, typically containing only a few dozen pixels. Therefore, to improve the array size and integration of microfluidic chips, active matrix (AM) arrays are used. AM pixels contain one or more TFT (thin film transistor) switches that control the connection between the pixel electrode and the external drive signals. The drive uses a row-column scanning method, with the same row or column sharing a single signal line, greatly reducing the number of signal lines required for the drive array. Therefore, the number of pixels in an AM array can easily reach hundreds or thousands. However, because the electrodes in AM pixels are not directly connected to the external drive circuitry, conventional impedance detection methods cannot be directly applied. Therefore, existing impedance detection technologies are mainly based on PM array microfluidic chips, but the limited scale of PM arrays cannot meet the demands of high-throughput, large-scale arrays. Summary of the Invention

[0003] Therefore, the purpose of this invention is to provide a solution to the above problems: a impedance detection method based on an AM array microfluidic chip is designed, which can perform impedance detection on each pixel in the array. By detecting the difference in pixel capacitance, the types of droplets on the pixel electrodes can be distinguished, thereby realizing the movement detection and position detection of microdroplets in the AM array.

[0004] According to a first aspect of this disclosure, a pixel circuit is provided, suitable for a microfluidic chip employing an active pixel array, comprising: an input terminal configured to input a voltage to a receiver terminal; a receiver terminal electrically connected to a pixel electrode and outputting a voltage; and a control terminal configured as a first TFT switch for controlling the electrical connection between the input terminal and the output terminal.

[0005] In some possible implementations, a bypass capacitor is also included, which is configured to be grounded.

[0006] In some possible implementations, a detection circuit is also included, comprising: a first terminal connected to the pixel electrode via a series capacitor; a second terminal grounded via a resistor; a third terminal for outputting the detection signal of the detection circuit; and a control terminal configured as a second TFT switch for controlling the output of the detection signal. By integrating the detection circuit for detecting impedance into the pixel circuit, the impedance detection of the row of pixels with the gate turned on is achieved, enabling efficient simultaneous detection of multiple pixels in the array.

[0007] According to a second aspect of this disclosure, a pixel circuit is provided, suitable for a microfluidic chip employing an active pixel array, including an input terminal configured to supply a voltage for inputting a voltage to a receiver terminal; a receiver terminal electrically connected to a pixel electrode and outputting a voltage; and a control terminal including a first TFT switch and a second TFT switch, wherein the first TFT switch is used to control the opening or closing of the second TFT switch, and the second TFT switch is used to control the electrical connection between the input terminal and the receiver terminal.

[0008] In some possible implementations, a bypass capacitor is also included, which is configured to be connected to the supply voltage.

[0009] In some possible implementations, a detection circuit is also included. This detection circuit includes a first terminal connected to the pixel electrode via a series capacitor; a second terminal grounded via a resistor; a third terminal for outputting the detection signal of the detection circuit; and a control terminal configured as a third TFT switch for controlling the output of the detection signal. By integrating the detection circuit for detecting impedance into the pixel circuit, the impedance of the pixels in the row where the gate is turned on is detected, enabling efficient simultaneous detection of multiple pixels in the array.

[0010] In some possible implementations, the waveform of the aforementioned pixel circuit includes a single-pulse square wave, a double-pulse square wave, a multi-pulse square wave, a triangular wave, or a sine wave.

[0011] According to a third aspect of this disclosure, a microfluidic chip is provided, comprising: a conductive layer disposed on a cover plate and configured to have a detection circuit for reading output signals of pixel circuits; and an active pixel array disposed on a substrate and configured to have the pixel circuits involved in the first aspect of this disclosure. AM array (active array) microfluidic chips are relatively large in scale, and position detection is required for precise control of droplet movement. One detection method is impedance testing. The pixel electrodes on the substrate and the conductive layer of the cover plate can form a planar capacitor. The dielectric constant of the material between the two electrode plates of the planar capacitor can affect the capacitance value. Since the dielectric constant of a microdroplet and its surrounding medium differs significantly, the type of droplet on the pixel electrode is determined by detecting the capacitance value of the pixel electrode, i.e., whether there is a microdroplet on the detected pixel electrode, thereby determining the position of the microdroplet.

[0012] According to a fourth aspect of this disclosure, a microfluidic chip is provided, comprising: a conductive layer disposed on a cover plate; and an active pixel array disposed on a substrate and configured to have the pixel circuitry described in the second aspect of this disclosure. The AM array (active array) microfluidic chip is relatively large, and position detection is required for precise control of droplet movement. One detection method is impedance testing. The pixel electrodes on the substrate and the conductive layer of the cover plate can form a planar capacitor. The dielectric constant of the material between the two electrode plates of the planar capacitor can affect the capacitance value. Since the dielectric constant of a microdroplet differs significantly from that of its surrounding medium, the type of droplet on the pixel electrode is determined by detecting the capacitance value of the pixel electrode, i.e., whether a microdroplet is present on the detected pixel electrode, thereby determining the position of the microdroplet.

[0013] According to a fifth aspect of this disclosure, a method for locating microdroplets is provided, the method comprising: providing the aforementioned pixel circuit; applying a voltage to the pixel circuit and reading the capacitance value of the pixel electrode, wherein the location of the microdroplet is the pixel electrode whose capacitance value differs from that of the other pixel electrodes.

[0014] Based on the above technical solutions, it can be seen that this disclosure has the following advantages:

[0015] 1. It can perform impedance detection on each pixel in the microfluidic chip of AM array, which is larger in scale and more practical than the impedance detection of traditional PM chip;

[0016] 2. By detecting the impedance of pixels, the types of droplets on pixel electrodes can be distinguished, thereby enabling the detection of the position and movement state of droplets in microfluidic chips. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This diagram illustrates the structure of a microfluidic chip according to an embodiment of the present disclosure.

[0019] Figure 2 A schematic diagram of the detection circuit according to an embodiment of the present disclosure is shown;

[0020] Figure 3 A structural diagram of a pixel circuit according to an embodiment of this disclosure is shown;

[0021] Figure 4 A structural diagram of a pixel circuit according to another embodiment of this disclosure is shown;

[0022] Figure 5 A structural diagram of a pixel circuit with impedance detection function according to an embodiment of the present disclosure is shown;

[0023] Figure 6 A structural diagram of a pixel circuit with impedance detection function according to another embodiment of this disclosure is shown;

[0024] Figure 7 The diagram shows signal waveforms of the driving pixel circuits in some embodiments of this disclosure. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] One embodiment of this disclosure provides a pixel circuit, comprising: an input terminal configured to input a voltage to a receiving terminal; a receiving terminal electrically connected to a pixel electrode and outputting a voltage; and a control terminal configured as a first TFT switch for controlling the electrical connection between the input terminal and the output terminal.

[0027] In some embodiments, a bypass capacitor is also included, which is configured to be grounded.

[0028] In some embodiments, a detection circuit is further included, comprising: a first terminal connected to the pixel electrode via a series capacitor; a second terminal grounded via a resistor; a third terminal for outputting a detection signal from the detection circuit; and a control terminal configured as a second TFT switch for controlling the output of the detection signal. By integrating the detection circuit for detecting impedance into the pixel circuit, the impedance of the pixels in the row where the gate is turned on is detected, enabling efficient simultaneous detection of multiple pixels in the array.

[0029] Another embodiment of this disclosure provides another pixel circuit suitable for microfluidic chips employing active pixel arrays, characterized by comprising: an input terminal configured to supply a voltage for inputting a voltage to a receiving terminal; a receiving terminal electrically connected to a pixel electrode and outputting a voltage; a control terminal including a first TFT switch and a second TFT switch, the first TFT switch being used to control the opening or closing of the second TFT switch, and the second TFT switch being used to control the electrical connection between the input terminal and the receiving terminal; and a bypass capacitor configured to be connected to the supply voltage.

[0030] In some embodiments, a bypass capacitor is also included, which is configured to be connected to the supply voltage.

[0031] In some embodiments, a detection circuit is further included, comprising a first terminal connected to the pixel electrode via a series capacitor; a second terminal grounded via a resistor; a third terminal for outputting a detection signal from the detection circuit; and a control terminal configured as a third TFT switch for controlling the output of the detection signal. By integrating the detection circuit for detecting impedance into the pixel circuit, the impedance of the pixels in the row where the gate is turned on is detected, enabling efficient simultaneous detection of multiple pixels in the array.

[0032] In some embodiments, the waveform of the aforementioned pixel circuit includes a single-pulse square wave, a double-pulse square wave, a multi-pulse square wave, a triangular wave, or a sine wave.

[0033] An embodiment of this disclosure also provides a microfluidic chip, comprising: a conductive layer disposed on a cover plate and configured to have a detection circuit for reading output signals of a pixel circuit; and an active pixel array disposed on a substrate and configured as the aforementioned pixel circuit without integrated detection circuit.

[0034] Another disclosed embodiment provides another microfluidic chip, including: a conductive layer disposed on a cover plate; and an active pixel array disposed on a substrate and configured as a pixel circuit with the aforementioned detection circuit integrated.

[0035] An embodiment of this disclosure also provides a method for locating microdroplets. The method involves applying a voltage to the pixel circuit and reading the capacitance value of the pixel electrode when using the pixel circuit provided in the foregoing embodiment. The location of the microdroplet is the pixel electrode whose capacitance value differs from that of other pixel electrodes.

[0036] Based on the above technical solutions, it can be seen that this disclosure has the following advantages:

[0037] 1. It can perform impedance detection on each pixel in the microfluidic chip of AM array, which is larger in scale and more practical than the impedance detection of traditional PM chip;

[0038] 2. By detecting the impedance of pixels, the types of droplets on pixel electrodes can be distinguished, thereby enabling the detection of the position and movement state of droplets in microfluidic chips.

[0039] The structure of a microfluidic chip is as follows Figure 1 As shown, it includes a cover plate 1, which is made of glass or acrylic. A conductive layer 2 is disposed on the lower surface of the cover plate 1, and the conductive layer 2 can be made of ITO (indium gallium zinc oxide) or other conductive materials. A detection circuit is disposed on the conductive layer 2. Figure 2 It includes at least one sub-circuit consisting of an ADC (analog-to-digital converter) 6 and a differentiating circuit 5. When there are multiple sub-circuits on the conductive layer 2, the sub-circuits are connected in parallel with each other.

[0040] It also includes a substrate 4, which can be made of glass. Pixel circuits 3 are disposed on the substrate 4. Multiple sets of pixel electrodes in the pixel circuits 3 are connected in parallel, and the same row or column shares a single signal line for connection to the external driving signal, and is driven by row and column scanning.

[0041] The structure of pixel circuit 3 in one embodiment is as follows: Figure 3 As shown, the input terminal is connected to Data to input voltage to pixel circuit 3. The receiving terminal is electrically connected to the pixel electrode in active array 3, outputting the voltage of Data to the pixel electrode. The connection between the input terminal and the receiving terminal is controlled by a TFT switch (TFT), the on / off state of which is controlled by an external drive signal Gate. Pixel circuit 3 is also equipped with a bypass capacitor Cst, which is configured to be grounded for noise absorption.

[0042] The structure of pixel circuit 3 in another embodiment is as follows: Figure 4As shown, the pixel circuit 3 is input with the supply voltage (VCC). The receiving end outputs the voltage of VCC to the pixel electrode. The connection between VCC and the pixel electrode is controlled by the TFT2 switch. The opening and closing state of the TFT2 switch is controlled by the first TFT switch (TFT1), which is electrically connected to the Data terminal, and the opening and closing of this connection is controlled by the Gate signal. When the Gate signal drives the TFT1 switch to open, the second TFT switch (TFT2) receives the voltage at the Data terminal and becomes open. When the TFT2 switch is open, VCC and the pixel electrode are connected, and the pixel electrode receives the voltage applied by VCC. The pixel circuit 3 also includes a capacitor Cst, which is configured to be connected to VCC to absorb VCC noise.

[0043] In another embodiment, the detection circuit for impedance detection is integrated into the pixel circuit. In this case, the detection circuit is no longer disposed on the conductive layer 2 of the cover plate 1. The detection circuit is added to the driving circuit of the pixel electrode disposed on the substrate 4.

[0044] The structure of pixel circuit 3 in one embodiment is as follows: Figure 5 As shown, the input terminal is connected to Data to input voltage to pixel circuit 3. The receiving terminal is electrically connected to the pixel electrode in active array 3, outputting the voltage of Data to the pixel electrode. The connection between the input terminal and the receiving terminal is controlled by a first TFT switch, and the opening and closing state of the first TFT switch (TFT1) is controlled by an external driving signal Gate. The first terminal of the detection circuit is electrically connected to the pixel electrode through a series capacitor, while the second terminal is grounded through a resistor. The resistor R and the capacitor Cser form an RC differentiating circuit. The response signal of the differentiating circuit is output to the third terminal through the node between the RC circuits and is detected. The signal output of the differentiating circuit is controlled by a second TFT switch (TFT2), and the opening or closing of the second TFT switch is also controlled by the external driving signal Gate at the control terminal. When Gate is high, it controls the opening of a row of pixels in its row, and then the Data signal can be written to the pixel at the intersection of the corresponding column and the row opened by Gate. At the same time, the impedance signal of this row of pixels can also be output through the Out node. Thus, the simultaneous detection of the impedance of the row of pixels opened by Gate is realized. By integrating the detection circuit for detecting impedance into the pixel circuit, the impedance of the pixel in the row with the gate turned on is detected, enabling efficient simultaneous detection of multiple pixels in the array.

[0045] The structure of pixel circuit 3 in one embodiment is as follows: Figure 6As shown, the pixel circuit 3 is input with the supply voltage (VCC). The receiving end outputs the voltage of VCC to the pixel electrode. The connection between VCC and the pixel electrode is controlled by the second TFT switch (TFT2). The on / off state of TFT2 is controlled by the first TFT switch (TFT1). TFT1 is electrically connected to Data, and the opening and closing of this connection is controlled by the Gate signal. When the Gate signal drives TFT1 to turn on, TFT2 receives the voltage at the Data terminal and becomes on. When TFT2 is on, VCC and the pixel electrode are connected, and the pixel electrode receives the voltage applied by VCC. The first terminal of the detection circuit is electrically connected to the pixel electrode through a series capacitor, while the second terminal is grounded through a resistor. The resistor R and the capacitor Cser form an RC differentiating circuit. The response signal of the differentiating circuit is output to the third terminal through the node between the RC circuits and is detected. The signal output of the differentiating circuit is controlled by the third TFT switch (TFT3), and the on or off state of TFT2 is also controlled by the external driving signal Gate at the control terminal. When the Gate signal is high, it controls the opening of one row of pixels in its row. The Data signal can then be written to the pixel at the intersection of the corresponding column and the row opened by the Gate. Simultaneously, the impedance signal of this row of pixels can be output through the Out node. This enables simultaneous detection of the impedance of the pixels in the row opened by the Gate. By integrating the impedance detection circuit into the pixel circuit, the impedance detection of the pixels in the row opened by the Gate is achieved, enabling efficient simultaneous detection of multiple pixels in the array.

[0046] Figure 7 These are waveforms available for driving the pixel circuitry of a microfluidic chip in some embodiments. A is a single-pulse square wave, B is a double-pulse or multi-pulse square wave, C is a triangular wave, and D is a sine wave. Different waveforms input to the pixel circuitry will result in different output response waveforms from the differentiating circuit; therefore, the driving waveform can be selected according to actual needs. The selectable waveforms include, but are not limited to, the four waveforms mentioned above.

[0047] In some embodiments, when it is necessary to locate microdroplets in the active pixel array 3, a voltage is applied to the active pixel array 3, forming a capacitor between the pixel electrode in the active pixel array 3 and the conductive layer 2 of the cover plate. The dielectric constant of the material between the two electrode plates of a planar capacitor can affect the capacitance value. Since the dielectric constant of the microdroplet and its surrounding medium are significantly different, the capacitance value of the pixel electrode where the microdroplet is located is different from that of the other pixel electrodes. This difference in capacitance value is captured by the differentiating circuit 5 of the conductive layer 2 and emits a signal, which can be used to determine the type of droplet on the pixel electrode, that is, whether there is a microdroplet on the detected pixel electrode, thereby determining the location of the microdroplet.

[0048] In other embodiments, when it is necessary to locate microdroplets in the active pixel array 3, a voltage is applied to the active pixel array 3, forming a capacitor between the pixel electrode in the active pixel array 3 and the conductive layer 2 of the cover plate. The dielectric constant of the material between the two electrode plates of a planar capacitor can affect the capacitance value. Since the dielectric constant of the microdroplet and its surrounding medium are significantly different, the capacitance value of the pixel electrode where the microdroplet is located is different from that of the other pixel electrodes. This difference in capacitance value is captured by the pixel circuit 3 with impedance detection function and sends a signal, which can be used to determine the type of droplet on the pixel electrode, that is, whether there is a microdroplet on the detected pixel electrode, thereby determining the location of the microdroplet.

[0049] Although the present invention has been further described and illustrated in detail with reference to preferred embodiments, the invention is not limited to the disclosed examples, and those skilled in the art can derive other modifications therefrom without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A pixel circuit, suitable for microfluidic chips employing active pixel arrays, characterized in that, include: The input terminal is configured to input a voltage to the receiving terminal. The receiving end is electrically connected to the pixel electrode and outputs voltage; The control terminal is configured as a first TFT switch for controlling the electrical connection between the input terminal and the output terminal; The detection circuit includes: The first end is connected to the pixel electrode via a series capacitor; The second terminal is grounded through a resistor; The third terminal is used to output the detection signal of the detection circuit; The control terminal is configured as a second TFT switch to control the output of the detection signal.

2. The pixel circuit according to claim 1, characterized in that, It also includes a bypass capacitor, which is configured to be grounded.

3. A pixel circuit, suitable for microfluidic chips employing active pixel arrays, characterized in that, include: The input terminal is configured to supply voltage for inputting voltage to the receiving terminal. The receiving end is electrically connected to the pixel electrode and outputs voltage; The control terminal includes a first TFT switch and a second TFT switch. The first TFT switch is used to control the opening or closing of the second TFT switch, and the second TFT switch is used to control the electrical connection between the input terminal and the receiving terminal. The detection circuit includes: The first end is connected to the pixel electrode via a series capacitor; The second terminal is grounded through a resistor; The third terminal is used to output the detection signal of the detection circuit; The control terminal is configured as a third TFT switch to control the output of the detection signal.

4. The pixel circuit according to claim 3, characterized in that, It also includes a bypass capacitor configured to be connected to the supply voltage.

5. The pixel circuit according to any one of claims 1 to 4, characterized in that, The waveforms of the pixel circuit include single-pulse square waves, double-pulse square waves, multi-pulse square waves, triangular waves, or sine waves.

6. A microfluidic chip, characterized in that, include: A conductive layer is disposed on the cover plate; An active pixel array is disposed on a substrate and configured to have pixel circuitry as described in claim 1 or 3.

7. A method for positioning microdroplets, characterized in that, The method includes: Provide a pixel circuit as described in any one of claims 1 to 4; A voltage is applied to the pixel circuit and the capacitance value of the pixel electrode is read. The location of the microdroplet is the pixel electrode whose capacitance value is different from that of other pixel electrodes.

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