Drive circuit for digital microfluidic array element, digital microfluidic chip and droplet driving and detection method using same

Abstract

A drive circuit for a digital microfluidic array element, a digital microfluidic chip and a droplet driving and detection method using same. The drive circuit for a digital microfluidic array element comprises a switch module and an export module. The switch module comprises an input node used for connecting to a data line, an output node used for connecting to an element electrode and a first switch, the first switch being connected to a scan line. The export module comprises an import node used for connecting to the output node, an export node used for connecting to an export voltage line and a second switch. On the basis of a data value of the scan line, the first switch is configured to address the output node, wherein (i) when the data value of the scan line is an active level, the first switch electrically connects the input node to the output node, so that the drive voltage of an element is equal to or greater than a threshold voltage required to control droplets that are present in the element, so as to set the element electrode to an actuated state, and (ii) when the data value of the scan line is an inactive level, the first switch electrically isolates the input node from the output node. In a first state, the second switch is configured to export a weak leakage current generated by the first switch, so that the drive voltage of the element electrode is less than the threshold voltage, so as to set the element electrode to a non-actuated state. In the actuated state, the element electrode is configured to actuate the droplets present therein, while in the non-actuated state, the element electrode is configured not to actuate the droplets present therein.

Description

Driving circuit of digital microfluidic array element, digital microfluidic chip and method for droplet driving and detection using the same TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to a digital microfluidic chip and a driving circuit thereof and a method for droplet driving and detection using the same. BACKGROUND

[0002] Microfluidic technology is a technology that can accurately control and manipulate microscale fluid, and can integrate sample preparation, reaction, separation, detection and other basic operations in biochemical processes on a centimeter-sized chip. This technology is generally applied to the analysis process of micro-amount of medicine in the fields of biology, chemistry, pharmacy, etc., wherein the digital microfluidic chip takes droplets as the control object, controls the movement of the droplets through electric field force, thermal force, electrostatic force, etc., and can control each individual droplet individually. The microfluidic technology requires a small amount of sample and reagent, has a simple structure, is easy to mass integrate, is more convenient for droplet manipulation, and has controllable droplet size and shape, with advantages of miniaturization, integration, low cost, high sensitivity, high flexibility, etc., greatly accelerating the speed of sample movement, extraction, separation, mixing and detection, and showing great prospects in the fields of physics, chemistry, biology, medicine, etc.

[0003] Digital microfluidic chips are particularly suitable for complex biochemical reaction processes, and as biochemical reactions become more and more delicate and complex, active digital microfluidic chips are increasingly favored due to their advantages of controllable number of droplets and programmable droplet path. However, due to the generally high driving voltage of digital microfluidic chips, active digital microfluidic chips are inevitably greatly affected by the leakage current of TFT, which undoubtedly reduces the flexibility and reliability of active digital microfluidic chips in driving droplets, limiting their further development, and therefore how to effectively reduce the influence of leakage current on droplet driving is a technical challenge currently faced.

[0004] SUMMARY

[0005] According to at least one embodiment of the present disclosure, a driving circuit of a digital microfluidic array element is provided, comprising: a switch module, a sink module; wherein the switch module comprises an input node for connecting to a source data line of a pulsed direct current voltage, an output node for connecting to an element electrode, and a first switch connected to a first scan line; the sink module comprises a sink-in node for connecting to the output node of the element electrode, a sink-out node for connecting to a sink voltage line, and a second switch; the first switch is configured to address the output node according to a data value of the scan line, wherein (i) when the data value of the scan line is a valid level, the first switch electrically connects the input node to the output node, so that the driving voltage of the element electrode is equal to or greater than a threshold voltage required for manipulating a droplet present in the element, thereby placing the element electrode in an actuated state; and (ii) when the data value of the first scan line is an invalid level, the first switch electrically isolates the input node from the output node; the second switch is configured to sink a weak leakage current generated by the first switch in a first state, so that the driving voltage of the element electrode is less than the threshold voltage, thereby placing the element electrode in a non-actuated state; wherein in the actuated state, the element electrode is configured to actuate a droplet present therein, and in the non-actuated state, the element electrode is configured not to actuate a droplet present therein.

[0006] According to at least one embodiment of the present disclosure, in the driving circuit of the digital microfluidic array element, the first state is an off state; and a control terminal of the second switch is connected to a first terminal of the second switch, so that the second switch always remains in the off state.

[0007] According to at least one embodiment of the present disclosure, in the driving circuit of the digital microfluidic array element, the first switch is connected between the input node and the output node, a control terminal of the first switch is connected to the first scan line; and the first switch comprises a first transistor; the second switch is connected between the sink-in node and the sink-out node; and the second switch comprises a second transistor.

[0008] According to at least one embodiment of the present disclosure, in the driving circuit of the digital microfluidic array element, a first terminal of the second transistor is connected to the sink-in node; and a second terminal of the second transistor is connected to the sink-out node.

[0009] According to at least one embodiment of the present disclosure, in the driving circuit of the digital microfluidic array element, a first terminal of the second transistor is connected to the sink-out node; and a second terminal of the second transistor is connected to the sink-in node.

[0010] According to at least one embodiment of the present disclosure, the driving circuit of the digital microfluidic array element is provided, wherein the first transistor and the second transistor have the same channel type. The channel resistance of the second transistor is greater than that of the first transistor.

[0011] According to at least one embodiment of the present disclosure, the driving circuit of the digital microfluidic array element is provided, wherein the width-length ratio of the second transistor is less than that of the first transistor; and / or, the active layer doping concentration of the second transistor is less than that of the first transistor.

[0012] According to at least one embodiment of the present disclosure, the driving circuit of the digital microfluidic array element is provided, wherein the first transistor is a multi-gate transistor; and the second transistor is a single-gate transistor.

[0013] According to at least one embodiment of the present disclosure, the driving circuit of the digital microfluidic array element is provided, wherein the first transistor has a low-leakage design, including a lightly doped drain (LDD) transistor.

[0014] According to at least one embodiment of the present disclosure, the driving circuit of the digital microfluidic array element is provided, further comprising a memory element; the memory element is configured to provide a storage signal for the output node; the memory element comprises a first capacitor connected between the output node and the export node; the first capacitor comprises a first plate connected to the export node; and a second plate connected to the output node; the second plate is the same conductive plate as the element electrode.

[0015] According to at least one embodiment of the present disclosure, the driving circuit of the digital microfluidic array element is provided, wherein the first state is an open state; and the second switch is configured to pass through the leakage current generated by the first switch by opening.

[0016] According to at least one embodiment of the present disclosure, the driving circuit of the digital microfluidic array element is provided, wherein the first switch is connected between the input node and the output node, and the control terminal of the first switch is connected to the first scan line; the first switch comprises a first transistor and a third transistor; the second switch is connected between the import node and the export node; and the second switch comprises a second transistor.

[0017] According to at least one embodiment of the present disclosure, a driving circuit of a digital microfluidic array element is provided, wherein a first end of the first transistor is connected to the input node; a first end of the third transistor is connected to a second end of the first transistor; a second end of the third transistor is connected to the output node; control terminals of the first transistor and the third transistor are connected to the first scan line; a first end of the second transistor is connected to the input node; a second end of the second transistor is connected to the output node; and a control terminal of the second transistor is connected to the first end of the third transistor.

[0018] According to at least one embodiment of the present disclosure, a driving circuit of a digital microfluidic array element is provided, wherein the switching module further comprises a detection module connected between the first switch and the output node, and the detection module comprises an auxiliary detection capacitor configured to address a polar fluid, wherein (i) when a first target signal appears in a voltage of the element electrode output node, the element electrode is loaded with a polar fluid; and (ii) when a second target signal appears in the voltage of the element electrode output node, the element electrode is not loaded with a polar fluid.

[0019] According to at least one embodiment of the present disclosure, a driving circuit of a digital microfluidic array element is provided, wherein the auxiliary detection capacitor is connected between the first end of the third transistor and the output node.

[0020] According to at least one embodiment of the present disclosure, a driving circuit of a digital microfluidic array element is provided, wherein the auxiliary detection capacitor has a voltage-dependent capacitance.

[0021] According to at least one embodiment of the present disclosure, a digital microfluidic chip is provided, comprising a plurality of manipulation elements, each manipulation element having an element electrode and a reference electrode, the chip further comprising a reference electrode driving circuit and an array element driving circuit as described in any one of the above, the reference electrode driving circuit being configured to apply a first reference voltage to the reference electrode, and the array element circuit being configured to address the element electrode of the corresponding manipulation element according to a data value of the first scan line.

[0022] At least one embodiment of the present disclosure provides a method for driving a digital microfluidic array element, the digital microfluidic array element having an element electrode and a reference electrode, the method comprising: applying a first reference voltage to the reference electrode; and addressing the element electrode according to a set of data, comprising: (i) when a first scan voltage is applied, a first data voltage is written to the corresponding array element electrode to define a voltage difference across the array element equal to or greater than an actuation voltage, then the array element is placed in an actuated state; (ii) when a second scan voltage is applied, the first data voltage is discharged, and the array element is placed in a non-actuated state; wherein in the actuated state, the element is configured to actuate a droplet present therein, and in the non-actuated state, the element is configured to not actuate a droplet present therein.

[0023] At least one embodiment of the present disclosure provides a method for monitoring the position of a digital microfluidic array element, the digital microfluidic array element having an element electrode and a reference electrode, the method comprising: applying a first reference voltage to the reference electrode; applying actuation data to the element electrode; collecting the voltage of the element electrode output node; and monitoring the voltage of the element electrode output node to address a polar fluid, comprising: (i) when a first target signal appears in the voltage of the element electrode output node, then the element electrode is loaded with a polar fluid; and (ii) when a second target signal appears in the voltage of the element electrode output node, then the element electrode is not loaded with a polar fluid. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are merely related to some embodiments of the present disclosure, but not limit the present disclosure.

[0025] FIG. 1 is a schematic cross-sectional view of a digital microfluidic chip according to some embodiments of the present disclosure.

[0026] FIG. 2A shows a circuit representation of the electrical load presented at an element electrode when a droplet is present in a digital microfluidic chip according to some embodiments of the present disclosure, and FIG. 2B shows a circuit representation of the electrical load presented at an element electrode when a droplet is not present in a digital microfluidic chip according to some embodiments of the present disclosure.

[0027] FIG. 3A is a schematic top view of a digital microfluidic chip according to some embodiments of the present disclosure; FIG. 3B is a schematic top view of a Bonding region of a digital microfluidic chip according to some embodiments of the present disclosure; and FIG. 3C is a schematic cross-sectional view of a digital microfluidic chip taken along line B-B’ in FIG. 3B according to some embodiments of the present disclosure.

[0028] FIG. 4A is a schematic composition diagram of a thin film electronic device in an array element circuit of a digital microfluidic chip according to the related art; FIG. 4B is a schematic circuit diagram of a thin film electronic device in an array element circuit of a digital microfluidic chip according to the related art; FIG. 4C is a schematic plan view of a thin film electronic device in an array element circuit of a digital microfluidic chip according to the related art; FIGs. 4D-4E are element electrode voltage measurement data when element electrodes are braked according to the related art.

[0029] FIG. 5 is a schematic composition diagram of a thin film electronic device in an array element circuit of a digital microfluidic chip according to some embodiments of the present disclosure.

[0030] FIG. 6A is a schematic circuit diagram of a thin film electronic device in an array element circuit of a digital microfluidic chip according to some embodiments of the present disclosure; FIG. 6B is a schematic plan view of a thin film electronic device in an array element circuit of a digital microfluidic chip according to some embodiments of the present disclosure; FIGs. 6C-6D are element electrode voltage measurement data when element electrodes are braked according to some embodiments of the present disclosure.

[0031] FIG. 7A is a schematic circuit diagram of a thin film electronic device in an array element circuit of a digital microfluidic chip according to other embodiments of the present disclosure; FIG. 7B is a schematic plan view of a thin film electronic device in an array element circuit of a digital microfluidic chip according to other embodiments of the present disclosure; FIGs. 7C-7D are element electrode voltage measurement data when element electrodes are braked according to other embodiments of the present disclosure.

[0032] FIG. 8A is a schematic circuit diagram of a thin film electronic device in an array element circuit of a digital microfluidic chip according to still other embodiments of the present disclosure; FIG. 8B is a schematic plan view of a thin film electronic device in an array element circuit of a digital microfluidic chip according to still other embodiments of the present disclosure; FIGs. 8C-8D are element electrode voltage measurement data when element electrodes are braked according to still other embodiments of the present disclosure.

[0033] FIG. 9A is a schematic circuit diagram of a thin film electronic device in an array element circuit of a digital microfluidic chip according to still other embodiments of the present disclosure; FIG. 9B is a schematic plan view of a thin film electronic device in an array element circuit of a digital microfluidic chip according to still other embodiments of the present disclosure; FIGs. 9C-9D are element electrode voltage measurement data when element electrodes are braked according to still other embodiments of the present disclosure.

[0034] FIG. 10A is a schematic circuit diagram of a thin film electronic device in an array element circuit of a digital microfluidic chip according to some embodiments of the present disclosure; FIG. 10B is a schematic plan view of a thin film electronic device in an array element circuit of a digital microfluidic chip according to some embodiments of the present disclosure; FIGs. 10C-10F are element electrode voltage measurement data when element electrodes are braked according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments of the present disclosure. Based on the described embodiments of the present disclosure, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present disclosure.

[0036] Unless otherwise defined, technical terms or scientific terms used in the present disclosure shall have the ordinary meaning of the terms to a person of ordinary skill in the art to which the present disclosure belongs. The terms “first”, “second” and similar terms used in the present disclosure do not denote any order, quantity or importance, but are only used to distinguish different components. The terms “include” or “contain” and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms “connect” or “connected” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0037] The various embodiments of the present disclosure provide a digital microfluidic chip, which can solve the technical problems of low driving flexibility and reliability of existing active digital microfluidic chips. The digital microfluidic chip of the embodiments of the present disclosure can derive the TFT leakage current, thereby avoiding the adverse effects caused by the leakage, has high flexibility in droplet control, and has high reliability, and thus can be applied to more biochemical reaction processes.

[0038] Figure 1 shows a portion of a conventional digital microfluidics chip in cross-section. The device comprises a lower substrate 11, on which is a layer formed of an electrically conductive material, which is patterned to make a plurality of element electrodes 3 (e.g. 3A and 3B in Figure 1). The term element electrode 3 can be understood to refer to both the physical electrode structure 3 associated with a particular array element, and also to the node of the circuitry connected directly to that physical structure. In operation, a driving voltage can be applied to different element electrodes (e.g. to element electrodes 3A and 3B respectively) while a reference electrode 4 is applied with a fixed ground voltage (e.g. zero volts), at which time the driving voltage experienced by the fluid on the element electrodes is equal to the element electrode voltage, so the element electrodes can also be referred to as driving electrodes. In an active digital microfluidics chip, thin film electronics 14 are provided on the lower substrate 11, and the array element electrodes 3 are driven by the thin film electronics 14. In a passive digital microfluidics chip, electrode traces 14 are provided on the lower substrate 11, and the array element electrodes 3 are driven by external driving signals via the electrode traces 14. Droplets 7 are composed of a polar material (which is typically aqueous and / or ionic) and are confined in a plane between the lower substrate 11 and a top substrate 21. A suitable gap between the lower substrate 11 and the top substrate 21 can be achieved by spacers 5, and a non-polar fluid 6 (e.g. oil) can be used to fill the volume not occupied by the droplets 7. An insulating layer 12 provided on the lower substrate 11 separates the electrically conductive element electrodes 3A, 3B from a first hydrophobic coating 13, on which the droplets 7 sit with a contact angle denoted by Θ. The hydrophobic coating is formed of a hydrophobic material (typically, but not necessarily, a fluoropolymer). A second hydrophobic coating 23 is on the top substrate 21, and the droplets 7 can be in contact with the second hydrophobic coating 26. The reference electrode 4 is interposed between the top substrate 21 and the second hydrophobic coating 23.

[0039] The contact angle Θ is defined as shown in Figure 1, and is determined by the balance of the surface tension components between the solid-liquid (γ SL ), liquid-gas (γ LG ) and non-polar fluid (γ SG ) interfaces, and satisfies Young's law in the absence of an applied voltage, which is given by the equation:

[0040] In some cases, the relative surface tensions of the materials involved (i.e. the values of γ SL , γ LG and γ SG ) can be such that the right-hand side of equation (1) is less than -1. This can typically occur in the case where the non-polar fluid 6 is oil. Under these conditions, the droplets 7 can lose contact with the hydrophobic coatings 13 and 23, and a thin layer of the non-polar fluid 6 (oil) can form between the droplets 7 and the hydrophobic coatings 13 and 23.

[0041] In operation, drive voltages (e.g., VT, V0, and V00 in FIG. 1) can be applied to different electrodes (e.g., to reference electrode 4, element electrodes 3A and 3B, respectively) to effectively control the hydrophobicity of hydrophobic coating 13. By arranging for different drive voltages (e.g., V0 and V00) to be applied to different element electrodes (e.g., 3A and 3B), droplet 7 can be moved in the lateral plane between the two substrates 11 and 21.

[0042] In the following description, it will be assumed that elements of an EWOD device such as the apparatus of FIG. 1 can receive data such that the element is placed in either an "actuated" state (a voltage applied to the element is sufficient to cause a droplet in the element to be subject to a significant electro wetting force) or a "non-actuated" state (a voltage applied to the element is insufficient to cause a droplet in the element to be subject to a significant electro wetting force). An element of an EWOD device can be placed in an actuated state by applying a voltage difference across the EWOD element that is equal to or greater in magnitude than a threshold voltage VEW, while an element of an EWOD device can be placed in a non-actuated state if the voltage difference across the EWOD element is less in magnitude than or substantially less than the threshold voltage VEW. The threshold voltage VEW is typically dependent on the properties of the droplet and the properties of the element. In particular, the threshold voltage VEW is typically dependent on the properties of the droplet (e.g., the relative permittivity of the droplet, the relative conductivity of the droplet, and the relative viscosity of the droplet) and the properties of the element (e.g., the relative permittivity of the element, the relative conductivity of the element, and the relative viscosity of the element). EW An element is in its non-actuated state if the magnitude of the voltage difference across the element is less than or substantially less than the threshold voltage VEW. The threshold voltage VEW is typically dependent on the properties of the droplet and the properties of the element. In particular, the threshold voltage VEW is typically dependent on the properties of the droplet (e.g., the relative permittivity of the droplet, the relative conductivity of the droplet, and the relative viscosity of the droplet) and the properties of the element (e.g., the relative permittivity of the element, the relative conductivity of the element, and the relative viscosity of the element). EW The threshold voltage VEW is often referred to as the "actuation voltage", which term is used below. In practice, the threshold voltage can often be determined as the minimum voltage required to achieve droplet operation (e.g., movement or splitting of a droplet). In many cases, there is one threshold voltage to move a droplet and a second (higher) threshold voltage to split a droplet, in which case the "actuation voltage" is preferably set above the threshold required to split a droplet. In practice, the non-actuated state can often be zero volts.

[0043] FIG. 2A shows a circuit representation of the electrical load 10A between element electrode 3 and reference electrode 4 in the presence of droplet 7. Droplet 4 can often be modeled as a parallel resistor and capacitor. Typically, the resistance of the droplet is relatively low (e.g., if the droplet contains ions) and the capacitance of the droplet is relatively high (e.g., because the relative permittivity of polar liquids is relatively high, e.g., -80 if the droplet is water-containing). In many cases, the droplet resistance is relatively small, so droplet 4 can effectively act as an electrical short. Hydrophobic coatings 13 and 23 have electrical properties that can be modeled as a capacitor. The total impedance between element electrode 3 and reference electrode 4 can be approximated by a capacitor as in the figure, the value of which is typically dominated by the insulating layer 12 and the hydrophobic coatings 13 and 23, and which can be on the order of picofarads in value for typical layer thicknesses and materials.

[0044] Figure 2B shows a circuit representation of the electrical load 10B between the element electrode 3 and the reference electrode 4 in the absence of a droplet 7. In this case, the droplet 4 assembly is replaced by the capacitance to the non-polar fluid 6 occupying the space between the top and bottom substrates. In this case, the total impedance between the element electrode 38 and the reference electrode 28 can be approximated by a capacitor whose value is dictated by the capacitance of the non-polar fluid and is typically small, of the order of picofarads.

[0045] For driving and sensing purposes, the electrical load 10 generally behaves as a capacitor in effect whose value depends on whether a droplet 7 is present at a given element electrode 3. In the presence of a droplet, the capacitance is relatively high (typically of the order of picofarads), while if no droplet 7 is present, the capacitance is low (typically of the order of femtofarads). If the droplet partially covers the element electrode 3, the capacitance can be approximated to the extent of coverage of the element electrode 3 by the droplet 7.

[0046] Figure 3A shows a portion of a conventional digital microfluidic chip in plan view. The chip is of sandwich construction, comprising two parts, an upper and a lower substrate, which are sealed and supported by a frame seal 5. The upper substrate 20 can have 10 vias on each of the left and right sides of the AA region (region A), which are used as sample or reagent addition or removal holes, the diameter of the vias matching the tip of a pipette, and the number of vias can be changed according to actual requirements. The lower substrate mainly comprises the following regions: the AA region (region A) composed of an array of element electrodes 3, the wiring region (region B) of Gate and Data lines, the static ring (region C) for preventing static electricity, the ground electrode (region D) for grounding the upper substrate, which is in communication with the upper substrate through conductive foam matching the size of the ground electrode, and the Bonding region (region E) for connecting with the FPC. The upper substrate mainly comprises a hydrophobic layer and a conductive layer, wherein the hydrophobic layer is consistent with the lower substrate, and the conductive layer is made of ITO. The thickness of the chip box (i.e. the thickness of the frame seal) is 20 um, and the filling medium is silicone oil, which can be changed according to requirements in actual design or use.

[0047] The Bonding region (region E) of the chip is composed of two rows of Bonding Leads, the upper row having m Bonding Leads and the lower row having n Bonding Leads, which are arranged alternately, as shown in Figure 3B. The arrangement and size of the Bonding Leads can be changed according to actual design requirements. Figure 3C is a sectional view of the dashed line B-B' in Figure 3B, and each Bonding Lead is composed of at least five layers, the Gate wiring layer 1401 and the SD wiring layer 1403 being in communication through GI vias, the SD wiring layer 1403 and the PAD layer 1405 being in communication through PVX vias, and the vias of GI and PAD being arranged alternately.

[0048] All the Gate lines and SD lines of all the pixels are connected to the metal lines (region F) at the outermost periphery of the chip through the electrostatic ring. When ESD is introduced into the chip, the electrostatic ring is opened, and all the electrostatic charges are uniformly distributed on the chip, reducing the accumulation of electrostatic charges in a single pixel. The GND lines of all the pixels are connected to the green SD metal lines (region F) at the outermost periphery of the chip. When the chip is normally used, the metal lines are connected to the ground signal through the Bonding Lead.

[0049] FIG. 4A shows a schematic diagram of an example arrangement of thin-film electronics 14 in an array element circuit in the related art. The array element circuit can include an actuation circuit 46 having input nodes ENABLE 141, DATA 142, and an output connected to an element electrode 3.

[0050] FIG. 4B shows a specific design of the array element circuit 14 in the related art. In this design, the output actuation circuit 46 includes a first switch 51 connected between the DATA signal 142 and the output node 3, and the control terminal of the first switch 51 is connected to the ENABLE signal 141. The first switch can be a first transistor T1. In this case, when a droplet moves to an adjacent element electrode 38B of the element electrode 38A, the output voltage on the electrode will always accumulate due to the drain current of the first transistor T1, resulting in failure of droplet driving.

[0051] Specifically, taking the process parameters commonly used in the related art as an example: the lower substrate of the digital microfluidic chip is composed of eight layers, namely, a Gate layer, a GI layer, an Active layer, an SD layer, a PVX layer, an ITO layer, a dielectric layer, and a hydrophobic layer. The Gate and SD layers are made of Mo metal material, with a thickness of about 200 nm. The GI layer is made of dense silicon nitride, with a thickness of about 400 nm and a dielectric constant of 7.2. The Active layer is made of a-Si and n+a-Si, which is the active layer of the TFT. The PVX layer is made of silicon nitride, with a thickness of about 300 nm and a dielectric constant of 6.5. The element electrode layer is made of ITO, with a thickness of about 52 nm. The dielectric layer can be made of silicon nitride, with a thickness of about 600 nm. The hydrophobic layer is made of Teflon, with a thickness of about 50 nm. The upper substrate of the digital microfluidic chip is composed of two layers, mainly including a hydrophobic layer and a conductive layer, wherein the hydrophobic layer is consistent with the lower substrate, and the conductive layer is made of ITO, with a thickness of about 30 nm. The chip box thickness is 20 um, and the filling medium is silicone oil. The driving voltage required for driving polar fluid by this chip structure is above 35 V.

[0052] An example connection relationship is shown in FIG. 4C: the Drain electrode of the first transistor (T1) 51 is connected to the DATA signal, the control terminal (Gate electrode) is connected to the ENABLE signal, the Source electrode is connected to the uppermost element electrode 3 through the via of the PVX, and the upper substrate reference electrode 4 is grounded.

[0053] An example driving signal is: the Vgh of the ENABLE signal is 90V, the Vgl is -9V, the period is 100us, and the peak width is 50us; the Vdh of the DATA signal is 70V, the Vdl is 0V, the period is 100us, and the peak width is 50us.

[0054] When the element electrode 3A is actuated to drive the droplet into the element electrode, that is, the ENABLE and DATA signals are both inputted with actuation signals, at this time, the measured element electrode voltage is about 69.7V, as shown in FIG. 4D. Since the upper substrate reference electrode 4 is grounded, the driving voltage between the two ends of the driving unit is about 69.7V, which is greater than the threshold driving voltage of the driving polar fluid, and the polar fluid inside the driving unit can be successfully driven.

[0055] When the droplet moves to the adjacent element electrode 3B, that is, the ENABLE signal applied to the element electrode 3A remains low, and the Data signal remains unchanged, at this time, since the first transistor 51 Vgs<0, and further Vgs-Vth<0, and Vds>100mV, the first transistor 51 works in the sub-threshold region or the cutoff region, and there is still a weak inversion layer formed in the back channel interface to form a conductive channel and further generate a leakage current. Due to the influence of this leakage current, the voltage on the element electrode will always accumulate, and at 2.8ms, it reaches 70V, as shown in FIG. 4E. Since the droplet has been transferred to the element electrode 3B at this time, as described before, the driving voltage on the element electrode 3B is 69.7V, and the driving voltage on the element electrode 38A reaches 70V at 2.8ms, which undoubtedly will affect the normal manipulation of the droplet, resulting in failure of the droplet manipulation.

[0056] FIG. 5 is a schematic diagram of an example arrangement of the thin film electronic device 14 in the array element circuit of the digital microfluidic chip according to some embodiments of the present disclosure. The array element circuit can include an actuation circuit 46 having input nodes ENABLE 141, DATA 142, and an output connected to the element electrode 3, a derivation circuit 47 connected to the output of the element electrode 3.

[0057] Figure 6A shows a design of the array element circuit according to some embodiments of the present application. The electrical load 10 and the reference electrode 4 are also shown in Figure 6A as they play a role in the operation of the circuit. The actuation circuit 46 comprises a first switch 51 and the discharge circuit 47 comprises a second switch 52. The first switch 51 is connected between a DATA signal 142 and an output node 143 which in turn is connected to the element electrode 3. The control terminal of the first switch 51 is connected to an ENABLE signal 141; the second switch 52 is connected between the output node 143 and a discharge signal line 144 and the control terminal of the second switch 52 is connected to the Drain electrode of the second switch 52. The first switch 51 can be a first transistor T1 and the second switch 52 can be a second transistor T2.

[0058] The array element circuit 14 performs two functions, namely an actuation function and a discharge function. The actuation function is explained as follows: the element electrode 3 is connected to the output node 143 of the array element circuit 14. To program data, a voltage is programmed onto the column addressing line 142. The ENABLE line 141 is then taken high to turn on the first transistor T1. The voltage on the DATA 142 is then programmed to the output node 143 which in turn is connected to the element electrode 3.

[0059] The discharge function is explained as follows: the second transistor T2 is connected between the output node 143 of the array element circuit 14 and the discharge signal line 144. When the ENABLE signal 141 is off and the Data signal 142 is on, the charge accumulated to the output node due to the leakage of the first transistor T1 can be connected to the discharge signal line 144 through the leakage effect of the second transistor T2, so that a large leakage voltage is not generated on the element electrode 3.

[0060] Specifically, taking the specific design of the array element circuit 14 shown in Figure 6B as an example: the connection relationship is as follows: the Drain electrode of the first transistor (T1) 51 is connected to the DATA signal 142, the control terminal (Gate electrode) is connected to the ENABLE signal 141, and the Source electrode is connected to the element electrode 3 of the uppermost layer through the via of PVX, and at the same time, the upper substrate reference electrode 4 is connected to the GND line 144. The Source electrode of the first transistor 51 is connected to the Drain electrode of the second transistor (T2) 52, and at the same time, is connected to the control terminal (Gate electrode) of the second transistor 52 through the GI via, and the Source electrode of the second transistor 52 is connected to the GND line 144. The process parameters and driving signals are the same as those commonly used in the prior art.

[0061] When the element electrode 3A is actuated, the driving liquid droplet enters the element electrode 3A, that is, the ENABLE and DATA signals input the actuation signal, at this time, the element electrode 3A voltage is about 40V, as shown in FIG. 6C, that is, the driving voltage is about 40V, which is greater than the threshold driving voltage required by the chip structure to drive the polar fluid, and the polar fluid can be successfully driven. At this time, since the first transistor 51 and the second transistor 52 are connected in series, the control terminal of the second transistor 52 is connected to the Drain electrode, so Vds = Vgs, the second transistor 52 cannot be fully opened, and the voltage across the second transistor 52 is greater than the voltage across the first transistor 51, and since the second transistor 52 and the driving unit composed of the element electrode 3A and the reference electrode 4 are connected in parallel, the voltage at the element electrode 3A is equivalent to the voltage across the second transistor 52, so that the driving unit voltage is about 40V, which is greater than the threshold driving voltage required by the chip structure to drive the polar fluid, and the polar fluid is successfully driven. At the same time, since the second transistor 52 cannot be fully opened, the charge on the pixel electrode cannot be completely discharged, which ensures the driving sensitivity of the digital microfluidic chip.

[0062] When the liquid droplet moves to the adjacent element electrode 3B, that is, the ENABLE signal 141 on the element electrode 3A remains low, and the Data signal 142 remains unchanged, at this time, due to the accumulation of charge to the output node 143 caused by the leakage of the first transistor 51, and the leakage effect of the second transistor 52 to the GND line 144 in time, so that a large leakage voltage is not generated on the element electrode 3A, as shown in FIG. 6D, the element electrode 3A voltage is always repeated as shown in the waveform, there is no large accumulated voltage, and the peak of the waveform is about 0.09V, which is less than the threshold driving voltage required by the chip structure to drive the polar fluid, and will not affect the programmed driving of the polar fluid. Therefore, this scheme can effectively reduce the influence of the leakage current on the driving of the liquid droplet, and further improve the driving reliability of the digital microfluidic chip.

[0063] FIG. 7A shows the design of an array element circuit according to some embodiments of the present application. The actuation circuit 46 comprises a first switch 51, and the discharge circuit 46 comprises a second switch 52. The first switch 51 is connected between the DATA (data) signal 142 and the output node 143, which in turn is connected to the element electrode 3. The control terminal of the first switch 51 is connected to the ENABLE (enable) signal 141; the second switch 52 is connected between the output node 143 and the discharge signal line 144, and the control terminal of the second switch 52 is connected to the Source electrode of the second switch 52. The first switch can be a first transistor T1, and the second switch can be a second transistor T2.

[0064] The array element circuit 84 performs two functions, namely, an actuation function and a derivation function. The actuation function is explained as follows: the element electrode 3 is connected to the output node 143 of the array element circuit 14. In order to program data, a voltage is programmed onto the column addressing line DATA. Then the ENABLE line is taken high to turn on the first transistor T1. The voltage on DATA is then programmed to the output node, which in turn is connected to the element electrode 38.

[0065] The derivation function is explained as follows: the second transistor T2 is connected between the output node of the array element circuit 84 and the derivation signal line. When the ENABLE signal is off and the Data signal is on, the charge accumulated to the output node due to the leakage of the first transistor T1 can be connected to the derivation signal line through the leakage effect of TFT2, so that a large leakage voltage is not generated on the element electrode 38.

[0066] Specifically, taking the specific design of the array element circuit shown in FIG. 7B as an example: the connection relationship is that the Drain electrode of the first transistor (T1) 51 is connected to the DATA (data) signal 141, the control terminal (Gate electrode) is connected to the ENABLE (enable) signal 142, the Source electrode is connected to the element electrode 3 in the uppermost layer through the via of PVX, and the upper substrate reference electrode 4 is connected to the GND line 144. The Source electrode of the first transistor 51 is connected to the Drain electrode of the second transistor (T2) 52, the Source electrode of the second transistor 52 is connected to the GND line, and the control terminal (Gate electrode) of the second transistor 22 is connected through the GI via. The process parameters and driving signals are the same as those commonly used in the prior art.

[0067] When the element electrode 3A is actuated to drive the droplet into the element electrode, that is, the ENABLE and DATA signals are both input with actuation signals, at this time, the measured element electrode voltage is about 69V, as shown in FIG. 7C, that is, the driving voltage is about 69V, which is greater than the threshold driving voltage required for the chip structure to drive the polar fluid, and the polar fluid can be successfully driven. At this time, since the first transistor 51 and the second transistor 52 are connected in series, the control terminal of the second transistor 52 is connected to the Source electrode, so Vds=Vgs, the second transistor 52 cannot be completely turned on, and the voltage across the second transistor 52 is greater than the voltage across the first transistor 51, and since the second transistor 52 and the driving unit composed of the element electrode 3A and the upper substrate reference electrode 4 are connected in parallel, the voltage at the element electrode 3A is equivalent to the voltage across the second transistor 52, so that the driving unit voltage is about 69V, which is greater than the threshold driving voltage required for the chip structure to drive the polar fluid, and the polar fluid is successfully driven. At the same time, since the second transistor 52 cannot be completely turned on, the charge on the pixel electrode cannot be completely led away, which ensures the driving sensitivity of the digital microfluidic chip.

[0068] When the droplet moves to the adjacent element electrode 3B, the ENABLE signal on the element electrode 3A remains low, and the Data signal does not change. At this time, the charge accumulated due to the leakage of the first transistor 51 to the output node 143 is timely introduced to the GND line 144 through the leakage effect of the second transistor 52, so that a large leakage voltage is not generated on the element electrode 38. As shown in FIG. 7D, the voltage on the element electrode 3A repeatedly shows the waveform, without a large accumulated voltage, and the peak of the waveform is about 0.11 V, which is less than the threshold driving voltage required for driving the polar fluid in the chip structure, and does not affect the programmed driving of the polar fluid. Therefore, the scheme can effectively reduce the influence of the leakage current on the driving of the droplet, and further improve the driving reliability of the digital microfluidic chip.

[0069] In the present exemplary embodiment, the control terminal of the second transistor is connected to the Source electrode of the second transistor, and is further connected to the export signal line 144, that is, the control terminal of the second transistor 52 is grounded. Compared with the Vg voltage of the control terminal connected to the output node 143, the control terminal is smaller, so that the second transistor 52 is more tightly closed when the element electrode 3A performs the actuation function, and the voltage across the element electrode 3A is larger. When the element electrode 3A performs the export function, although the voltage across the element electrode 3A is slightly increased due to the increased voltage division of the second transistor 52, it is far less than the threshold voltage, which has no effect on the driving of the droplet.

[0070] FIG. 8A shows the design of the array element circuit according to still another embodiment of the present application. The actuation circuit 46 comprises a first switch 51, and the export circuit 47 comprises a second switch 52. The first switch can be a first transistor T1, and the second switch can be a second transistor T2. The connection relationship of the first transistor T1 and the second transistor T2 is the same as that in FIG. 6A, and the voltage division of the first transistor T1 and the second transistor T2 is optimized.

[0071] Specifically, taking the specific design of the array element circuit 14 shown in FIG. 8B as an example: the first transistor (T1) 51 is a double-gate transistor with a W / L of 50 / (6+6), which is beneficial to reduce the leakage current and improve the charging rate of the element electrode; the second transistor (T2) 52 is a single-gate transistor with a W / L of 6 / 4, and the W / L is relatively small, so that the charge passing capacity is relatively weak, which can further improve the voltage division when the element electrode performs the actuation function. The process parameters and driving signals are the same as those in the foregoing related technologies.

[0072] When the element electrode 3A is actuated, the driving liquid droplet enters the element electrode 3A, that is, both the ENABLE and DATA signals input the actuation signal, at this time, the element electrode 3A voltage is about 58V, as shown in FIG. 8C, that is, the driving voltage is about 58V, which is greater than the threshold driving voltage required by the chip structure to drive the polar fluid, and the polar fluid can be successfully driven. At this time, since the first transistor 51 and the second transistor 52 are connected in series, the control terminal of the second transistor 52 is connected to the Drain electrode, so Vds = Vgs, the second transistor 52 cannot be fully opened, and the voltage across the second transistor 52 is greater than the voltage across the first transistor 51, and since the second transistor 52 and the driving unit composed of the element electrode 3A and the reference electrode 4 are connected in parallel, the voltage at the element electrode 3A is equivalent to the voltage across the second transistor 52, so that the driving unit voltage is about 58V, which is greater than the threshold driving voltage required by the chip structure to drive the polar fluid, and the polar fluid is successfully driven. At the same time, since the second transistor 52 cannot be fully opened, the charge on the pixel electrode cannot be completely discharged, which ensures the driving sensitivity of the digital microfluidic chip.

[0073] When the liquid droplet moves to the adjacent element electrode 3B, that is, the ENABLE signal 141 on the element electrode 3A remains low, and the Data signal 142 remains unchanged, at this time, due to the accumulation of charge to the output node 143 caused by the leakage of the first transistor 51, and the leakage effect of the second transistor 52 to the GND line 144 in time, so that a large leakage voltage is not generated on the element electrode 3A, as shown in FIG. 8D, the element electrode 3A voltage is always repeated as shown in the waveform, there is no large accumulated voltage, and the peak of the waveform is about 0.9V, which is less than the threshold driving voltage required by the chip structure to drive the polar fluid, and will not affect the programmed driving of the polar fluid. Therefore, this scheme can effectively reduce the influence of the leakage current on the driving of the liquid droplet, and further improve the driving reliability of the digital microfluidic chip.

[0074] In addition, in addition to the first transistor 51 being a double-gate transistor with a W / L greater than that of the second transistor T2, and the second transistor 52 being a single-gate transistor with a W / L of 6 / 4, in some embodiments, the first transistor 51 can also have a low-leakage design to further reduce the leakage current generated by the first transistor 51, including a lightly doped drain (LDD) transistor, etc.; in other embodiments, the first transistor 51 and the second transistor 52 can also be adjusted by designing the second transistor 51 to have an active layer doping concentration less than that of the first transistor 51. Obviously, all other modified embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present disclosure.

[0075] In addition, the driving signal is also optimized to further reduce power consumption. Simulation shows that the Vgh of the ENABLE signal is 60V, the Vgl is -9V, the period is 100us, and the peak width is 50us; the Vdh of the DATA signal is 40V, the Vdl is 0V, the period is 100us, and the peak width is 50us. At this time, the element electrode voltage is 35V, which ensures the driving of the digital microfluidic chip.

[0076] In addition, the second switch 47 can be a resistor with a larger resistance value, and can be other possible electronic elements that can not short circuit and thus derive the leakage current of the first switch 46 and divide the voltage with respect to the first switch 46. Obviously, all other modified embodiments obtained by a person skilled in the art without creative labor fall within the protection scope of the present disclosure.

[0077] FIG. 9A shows the design of an array element circuit according to still other embodiments of the present application. The actuation circuit 46 comprises a first switch 51, and the derivation circuit 46 comprises a second switch 52. The connection relationship of the first switch 51 and the second switch 52 is the same as that of FIG. 7A, and the first switch can be a first transistor T1 and the second switch can be a second transistor T2. In addition, the driving circuit further comprises a memory element 54 connected between the output node 143 and the derivation node 144, and the memory element 54 can be a first capacitor C1; the first capacitor C1 comprises a first plate 541 connected to the derivation node 143; and a second plate 542 connected to the output node 144; and the second plate 542 can be the same conductive plate as the element electrode 3.

[0078] The storage function is explained as follows: when the droplets are controlled in a scanning manner, the scanning frequency of the Gate signal is about 244Hz, that is, the voltage on the element electrode 3 needs to be maintained at more than 30V for more than 4ms. At this time, a storage capacitor needs to be added to the pixel electrode, that is, the storage capacitor can supply power to the pixel electrode for a certain period of time after the pixel is turned off. Specifically, taking the specific design of the array element circuit 14 shown in FIG. 9B as an example: the lower substrate 541 of the first capacitor C1 is made of an SD film layer and is connected with the GND line 144 to form a capacitor with the element electrode 3. According to the capacitor calculation formula: C=ε0εS / d

[0079] wherein ε0 is the vacuum permittivity, ε is the relative permittivity of the capacitor dielectric layer, S is the opposite area of the upper and lower substrates of the first capacitor C1, and d is the distance between the upper and lower substrates of the first capacitor C1.

[0080] When the Gate power supply interval is 40ms and the other characteristics of the Gate and Data signals remain unchanged, the process parameters and the driving signal are the same as the commonly used settings in the foregoing related art.

[0081] When the element electrode 3A is actuated, the driving liquid droplet into the element electrode, that is, both the ENABLE and DATA signals input the braking signal, at this time, the measured element electrode voltage is always greater than 30V, as shown in FIG. 9C, that is, the driving voltage is always greater than 30V, the average driving voltage is greater than the threshold driving voltage required by the chip structure to drive the polar fluid, and the polar fluid can be successfully driven. At this time, since the first transistor (T1) 51 and the second transistor (T2) 52 are connected in series, the control terminal of the second transistor 52 is connected to the Source electrode, so Vds = Vgs, the second transistor 52 cannot be fully opened, and the voltage across the second transistor 52 is greater than the voltage across the first transistor 51. Again, since the second transistor 52 and the element electrode 3A and the upper substrate reference electrode 4 form a driving unit in parallel, the voltage at the element electrode 3A is equivalent to the voltage across the second transistor 52, so that the driving unit voltage is greater than the threshold driving voltage required by the chip structure to drive the polar fluid, and the polar fluid is successfully driven. At the same time, since the second transistor 52 cannot be fully opened, the charge on the pixel electrode cannot be completely conducted away, ensuring the driving sensitivity of the digital microfluidic chip.

[0082] When the liquid droplet moves to the adjacent element electrode 3B, that is, the ENABLE signal on the element electrode 3A remains low, and the Data signal remains unchanged, at this time, as shown in FIG. 9D, the element electrode 3A voltage repeats the waveform, there is no large accumulated voltage, and the peak of the waveform is about 9mV, which is less than the threshold driving voltage required by the chip structure to drive the polar fluid, and will not affect the programmed driving of the polar fluid. Therefore, this scheme can effectively reduce the influence of the leakage current on the driving of the liquid droplet, and further improve the driving reliability of the digital microfluidic chip.

[0083] In summary, in the schematic embodiments shown in FIGS. 5-9, the second switch is configured to, in the off state, conduct the weak leakage current generated by the first switch in the non-actuated state of the element electrode, so that the driving voltage of the element electrode is less than the threshold voltage, thereby placing the element electrode in the non-actuated state. It should be understood that FIGS. 5-9 are only one example of extending the leakage current of the active digital microfluidic chip, and the present disclosure is not limited thereto. Various combinations and extensions of modules can be made according to actual application needs.

[0084] In addition, the second switch can be changed in the circuit design to, in the on state, conduct the weak leakage current generated by the first switch in the non-actuated state of the element electrode, so that the driving voltage of the element electrode is less than the threshold voltage, thereby placing the element electrode in the non-actuated state. In addition, a detection module can also be added to realize the functions of liquid droplet positioning, liquid droplet component detection, etc.

[0085] Figure 10A shows a design of an array element circuit according to some embodiments of the application. The actuation circuit 46 comprises a first switch 51 and the bootstrap circuit 47 comprises a second switch 52. The first switch 51 is connected between a DATA signal 142 and an output node 143, which in turn is connected to the element electrode 3, and the control terminal of the first switch 51 is connected to an ENABLE signal 141. The second switch 52 is connected between the output node 143 and a bootstrap signal line 144. The first switch 51 can comprise a first transistor T1 and a third transistor T3, and the second switch 52 can be a second transistor T2. The control terminal of the second transistor T2 is connected between the first transistor T1 and the third transistor T3.

[0086] In addition, the actuation circuit 46 further comprises a detection module 54 connected between the first switch 51 and the output node 143. The detection module 54 can comprise an auxiliary detection capacitor C2 comprising a first plate 541 connected to a bootstrap node 145 of the first transistor T1, and a second plate 542 connected to the output node 144. The second plate 542 can be the same conductive plate as the element electrode 3.

[0087] The array element circuit 14 performs three functions, namely an actuation function, a bootstrap function and a detection function. The actuation function is explained as follows: The element electrode 3 is connected to the output node 143 of the array element circuit 14. To program data, a voltage is programmed onto the column addressing line 142. The ENABLE line 141 is then taken high to turn on the first transistor T1 and the third transistor T3. The voltage on the DATA 142 is then programmed to the output node 143, which in turn is connected to the element electrode 3.

[0088] The bootstrap function is explained as follows: The second transistor T2 is connected between the output node 143 of the array element circuit 14 and the bootstrap signal line 144. When the ENABLE signal 141 is off and the Data signal 142 is on, charge accumulates at the output node 143 due to leakage current of the first transistor T1 and the third transistor T3. When the charge at the output node 143 accumulates to a certain level, the second transistor T2 turns on and the accumulated charge at the output node 143 is connected to the bootstrap signal line 144 via the second transistor T2, so that a large leakage voltage is not developed across the element electrode 3.

[0089] The detection function is explained as follows: As mentioned before, for driving and sensing purposes, the electrical load 10 behaves in effect as a capacitor whose value depends on whether a droplet 7 is present at a given element electrode 3. In the presence of a droplet, the capacitance is relatively high (typically in the order of picofarads), while if no droplet 7 is present, the capacitance is low (typically in the order of femtofarads). If the droplet partially covers the element electrode 3, the capacitance can be approximated to the degree of coverage of the element electrode 3 by the droplet 7. In the present illustrative embodiment, an auxiliary detection capacitance C2 is connected between the drain node 145 of the first transistor T1 and the output node 143, which is equivalent to being connected in parallel across the third transistor T3, and in series with the electrical load 10. Thus, the high or low value of the electrical load 10 capacitance will affect the voltage division of the electrical load 10 and the auxiliary detection capacitance C2, i.e. whether a droplet 7 is present at the element electrode 3 will affect the voltage division of the electrical load 10 and the auxiliary detection capacitance C2, and by measuring the voltage at the element electrode 3 it is possible to determine whether a droplet 7 is present at the element electrode 3.

[0090] In particular, taking the specific design of the array element circuit 14 shown in Figure 10B as an example: the connection relationship is as follows: the Drain electrode of the first transistor (T1) 51 is connected to the DATA signal 142, the control terminal (Gate electrode) is connected to the ENABLE signal 141, the Source electrode is connected to the Drain electrode of the third transistor (T3) 53, and is connected to the control terminal (Gate electrode) of the second transistor (T2) 52 through the via of GI; the Drain electrode of the third transistor 53 is connected to the Source electrode of the first transistor 51, the control terminal (Gate electrode) is connected to the ENABLE signal 141, and the Source electrode is connected to the output node 143, while being connected to the uppermost element electrode 3 through the PXV via; the Drain electrode of the second transistor 52 is connected to the output node 143, the Source electrode is connected to the GND line 144, and the control terminal (Gate electrode) is connected to the Source electrode of the first transistor T1; the auxiliary detection capacitance (C2) 541 is connected between the drain node 145 of the first transistor 51 and the output node 143. At the same time, the upper substrate reference electrode 4 is connected to the GND line 144. The process parameters, driving signals and commonly used settings in the above related art are the same.

[0091] When the element electrode 3A is actuated, the driving liquid droplet enters the element electrode 3A, that is, the ENABLE and DATA signals are input with actuation signals, at this time, the element electrode 3A voltage is about 35.6V, as shown in FIG. 10C, that is, the driving voltage is about 35.6V, which is greater than the threshold driving voltage required for the chip structure to drive the polar fluid, and the polar fluid can be successfully driven. At this time, since the Source electrode of the first transistor 51 is connected to the control terminal (Gate electrode) of the second transistor 52, the charge caused by the drain current of the first transistor T1 accumulates to the output node 145 of the first transistor 51, when the charge accumulated at the output node 145 of the first transistor 51 is greater than the turn-on voltage of the second transistor 52, the second transistor T2 is turned on, and the charge accumulated at the output node 143 is connected to the discharge signal line 144 through the second transistor 52, so that a large leakage voltage is not generated on the element electrode 3.

[0092] In addition, since the second transistor 52 and the element electrode 3A and the reference electrode 4 form a driving unit in parallel, the voltage at the element electrode 3A is equivalent to the voltage across the second transistor 52, so that the driving unit voltage is about 35.6V, which is greater than the threshold driving voltage required for the chip structure to drive the polar fluid, and the polar fluid is successfully driven, which ensures the driving sensitivity of the digital microfluidic chip.

[0093] When the liquid droplet moves to the adjacent element electrode 3B, that is, the ENABLE signal 141 on the element electrode 3A remains low, and the Data signal 142 remains unchanged, at this time, since the second transistor T2 is turned on when the charge accumulated at the output node 145 of the first transistor is greater than the turn-on voltage of the second transistor 52, the charge accumulated at the output node 145 of the first transistor is introduced into the GND line 144 through the second transistor 52, so that a large leakage voltage is not generated on the element electrode 3A, as shown in FIG. 10D, the voltage at the element electrode 3A repeats the waveform shown in the figure, without a large accumulated voltage, the peak of the waveform shown in the figure is about 0.11V, which is less than the threshold driving voltage required for the chip structure to drive the polar fluid, and does not affect the programmed driving of the polar fluid, therefore, this scheme can effectively reduce the influence of the leakage current on the driving of the liquid droplet, and further improves the driving reliability of the digital microfluidic chip.

[0094] The electric load 10 has a capacitance of the order of picofarad when a droplet 7 is present at the given element electrode 3, and a capacitance of the order of femtofarad when no droplet 7 is present at the given element electrode 3. In the illustrative embodiment, the auxiliary detection capacitance C2 is connected between the leading node 145 and the output node 143 of the first transistor T1, equivalent to being connected in series with the electric load 10. In the illustrative embodiment, the auxiliary detection capacitance C2 forms a capacitor with the element electrode 3 with a capacitance of 50 pf. As shown in FIG. 10E, when no droplet 7 is present at the given element electrode 3, a driving signal is applied to the element electrode 3, and the voltage of the element electrode 3 is measured to be about 35.6 V, which is greater than the threshold driving voltage required for the chip structure to drive the polar fluid, and at the same time, a sharp signal appears at the edge of the waveform, with a voltage of 41.1 V. As shown in FIG. 10F, when a droplet 7 is present at the given element electrode 3, a driving signal is applied to the element electrode 3, and the voltage of the element electrode 3 is measured to be about 35.6 V, which is greater than the threshold driving voltage required for the chip structure to drive the polar fluid, and at the same time, no sharp signal appears at the edge of the waveform. Therefore, the presence or absence of a droplet on the target element electrode can be determined by detecting the difference in the signal, so as to achieve the position monitoring of the droplet. That is, whether a droplet 7 is present at the element electrode 3 can be determined by measuring the voltage of the element electrode 3.

[0095] Furthermore, the embodiments of the present disclosure can reasonably introduce or replace active capacitors as needed. An active capacitor is a device whose capacitance is a function of the voltage between its terminals (i.e., the capacitor has a voltage-dependent capacitance). It can be formed using a conductive gate as the positive terminal and using n-type semiconductor material for the negative terminal. The voltage between the positive and negative terminals can be denoted as V+-. When V+- is negative, the semiconductor is in depletion and contains almost no mobile charge, and the capacitance is small; when V+- is positive, the semiconductor material is in accumulation and contains many mobile charges, and the capacitance is large. By using the active capacitor 110 as a boost capacitor, the circuit is arranged such that the potential of the target point is boosted when desired and is not boosted when not desired.

[0096] It should be understood that FIGS. 10A-10B are only one example of the detection module expansion, and the present disclosure is not limited thereto. Various combinations and expansions of the modules can be made according to actual application needs.

[0097] The following points need to be explained:

[0098] (1) In the drawings of the embodiments of the present disclosure, only the structures related to the embodiments of the present disclosure are involved, and other structures can refer to the usual design.

[0099] (2) The features in the same embodiment and different embodiments of the present disclosure can be combined with each other without conflict.

[0100] The above merely provides the specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto, and any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present disclosure, which should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A driving circuit of a digital microfluidic array element, the driving circuit comprising: a switching module, a bleeding module, wherein the switching module comprises an input node for connection to a data line, an output node for connection to an element electrode, and a first switch connected to a scan line; the bleeding module comprises a bleeding-in node for connection to the output node, a bleeding-out node for connection to a bleeding-out voltage line, and a second switch; the first switch is configured to address the output node according to a data value of the scan line, wherein (i) when the data value of the scan line is a valid level, the first switch electrically connects the input node to the output node, so that a driving voltage of the element is equal to or greater than a threshold voltage required for manipulating a droplet present in the element, thereby placing the element electrode in an actuated state; and (ii) when the data value of the first scan line is an invalid level, the first switch electrically isolates the input node from the output node; the second switch is configured to bleed a weak leakage current generated by the first switch in a first state, so that the driving voltage of the element electrode is less than the threshold voltage, thereby placing the element electrode in a non-actuated state; wherein in the actuated state, the element electrode is configured to actuate a droplet present therein, and in the non-actuated state, the element electrode is configured not to actuate a droplet present therein.

2. The driving circuit of claim 1, wherein: the first state is an off state; a control terminal of the second switch is connected to a first terminal of the second switch, so that the second switch always remains in an off state.

3. The driving circuit of claim 2, wherein: the first switch is connected between the input node and the output node, and a control terminal of the first switch is connected to the first scan line; and the first switch comprises a first transistor; the second switch is connected between the bleeding-in node and the bleeding-out node; and the second switch comprises a second transistor.

4. The driving circuit of claim 3, wherein: a first terminal of the second transistor is connected to the bleeding-in node; and a second terminal of the second transistor is connected to the bleeding-out node.

5. The driving circuit of claim 3, wherein: a first terminal of the second transistor is connected to the bleeding-out node; and a second terminal of the second transistor is connected to the bleeding-in node.

6. The driving circuit of any one of claims 3-5, wherein: the first transistor and the second transistor are of the same channel type.

7. The driving circuit of any one of claims 3-6, wherein: a channel resistance of the second transistor is greater than the first transistor.

8. The driving circuit of claim 7, wherein: a width-to-length ratio of the second transistor is less than a width-to-length ratio of the first transistor; and / or an active layer doping concentration of the second transistor is less than the first transistor.

9. The driving circuit of claim 8, wherein: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The first transistor is a multi-gate transistor. The second transistor is a single-gate transistor.

10. The drive circuit of any one of claims 3-6, wherein: The first transistor has a low leakage design, including a lightly doped drain (LDD) transistor.

11. The drive circuit of any one of claims 1-10, wherein: The drive circuit further comprises a memory element; The memory element is configured to provide a storage signal for the output node; The memory element comprises a first capacitor connected between the output node and the bootstrap node; The first capacitor comprises a first plate connected to the bootstrap node; and a second plate connected to the output node; The second plate is the same conductive plate as the element electrode.

12. The drive circuit of claim 1, wherein: The first state is an on state; The second switch is configured to bootstrap a leakage current generated by the first switch by turning on.

13. The drive circuit of claim 12, wherein: The first switch is connected between the input node and the output node, and a control terminal of the first switch is connected to the first scan line; and The first switch comprises a first transistor and a third transistor; The second switch is connected between the bootstrap node and the bootstrap node; and The second switch comprises a second transistor.

14. The drive circuit of claim 13, wherein: A first terminal of the first transistor is connected to the input node; A first terminal of the third transistor is connected to a second terminal of the first transistor; A second terminal of the third transistor is connected to the output node; Control terminals of the first transistor and the third transistor are connected to the first scan line; and A first terminal of the second transistor is connected to the bootstrap node; A second terminal of the second transistor is connected to the bootstrap node; A control terminal of the second transistor is connected to the first terminal of the third transistor.

15. The drive circuit of any one of claims 12-14, wherein: The switch module further comprises a detection module, The detection module is connected between the first switch and the output node, The detection module comprises an auxiliary detection capacitor, The auxiliary detection capacitor is configured to address a polar fluid, wherein (i) when a voltage of the element electrode output node appears a first target signal, the element electrode is loaded with a polar fluid; and (ii) when a voltage of the element electrode output node appears a second target signal, the element electrode is not loaded with a polar fluid.

16. The drive circuit of claim 15, wherein: The auxiliary detection capacitor is connected between the first terminal of the third transistor and the output node.

17. The drive circuit of claim 16, wherein: The auxiliary detection capacitor has a voltage-dependent capacitance. ​ 18. A digital microfluidic chip, the chip comprising a plurality of manipulation elements, each manipulation element having an element electrode and a reference electrode, the chip further comprising a reference electrode drive circuit and an array element drive circuit as claimed in any one of claims 1-19, the reference electrode drive circuit configured to apply a first reference voltage to the reference electrode, the array element circuit configured to address the element electrodes of respective manipulation elements according to data values of a first scan line.

19. A method of driving a digital microfluidic array element, the digital microfluidic array element having an element electrode and a reference electrode, the method comprising: applying a first reference voltage to the reference electrode; and addressing the element electrode according to a set of data, comprising: (i) when a first scan voltage is applied, a first data voltage is written to the respective array element electrode to define a voltage difference across the array element equal to or greater than an actuation voltage, then the array element is placed in an actuated state; (ii) when a second scan voltage is applied, the first data voltage is removed, and the array element is placed in a non-actuated state; wherein in the actuated state, the element is configured to actuate a droplet present therein, and in the non-actuated state, the element is configured to not actuate a droplet present therein.

20. A method of digital microfluidic array element position monitoring, the digital microfluidic array element having an element electrode and a reference electrode, the method comprising: applying a first reference voltage to the reference electrode; applying an actuation data to the element electrode; collecting a voltage of an element electrode output node; and monitoring the voltage of the element electrode output node for a signal indicative of a polar fluid, comprising: (i) when a first target signal occurs in the voltage of the element electrode output node, then the element electrode is loaded with a polar fluid; and (ii) when a second target signal occurs in the voltage of the element electrode output node, then the element electrode is not loaded with a polar fluid. ​ ​ ​

Images