Electrowetting device

Abstract

This electrowetting device includes: an array substrate on which working electrodes are arranged; a counter substrate on which counter electrodes are arranged, and which is disposed opposite and away from the array substrate; and a spacer disposed between the array substrate and the counter substrate. The counter substrate has a first opening through which a specimen is injected into a region where the array substrate and the counter substrate are separated from each other, and a second opening through which the specimen is discharged. The spacer has a first sub-spacer on the array substrate side and a second sub-spacer on the counter substrate side. The first sub-spacer and the second sub-spacer have an elongated shape in plan view, and the first sub-spacer and the second sub-spacer overlap such that the longitudinal directions thereof intersect.

Description

Electrowetting Device

[0001] One embodiment of the present invention relates to the design of a device for controlling electrowetting to manipulate flowable analytes.

[0002] In recent years, development of electrowetting devices utilizing the electrowetting effect has been progressing. The electrowetting effect is a phenomenon in which, when a voltage is applied between a liquid and an electrode, the energy at the solid-liquid interface between the electrode surface and the liquid changes, resulting in a change in the surface shape of the liquid. By utilizing this phenomenon, it is possible to construct a liquid delivery device capable of transporting microdroplets (see Patent Documents 1 to 6).

[0003] Japanese Patent Application Publication No. 2018-51685 Japanese Patent Application Publication No. 2012-163956 U.S. Patent No. 6,565,727 U.S. Patent No. 6,911,132 U.S. Patent Application Publication No. 2023 / 0110598 Japanese Patent Application Publication No. 2006-125900

[0004] In an electrowetting device, an analyte is sandwiched between a working electrode arranged on an array substrate and a counter electrode arranged on a counter substrate, and the potential of the working electrode is changed to manipulate the analyte (control the direction of movement). To smoothly manipulate the analyte, it is desirable that the distance between the array substrate and the counter substrate (in other words, the distance between the working electrode and the counter electrode) be constant and stable. It is also desirable that the array substrate and the counter substrate have an appropriate distance depending on the size of the analyte. For example, in an electrowetting device, it may be necessary to simultaneously manipulate analytes of different sizes.

[0005] An electrowetting device according to one embodiment of the present invention includes an array substrate on which working electrodes are arranged, a counter substrate on which a counter electrode is arranged and which is disposed opposite to and spaced apart from the array substrate, and a spacer between the array substrate and the counter substrate. The counter substrate has a first opening for injecting a sample into a region where the array substrate and the counter substrate are separated, and a second opening for discharging the sample. The spacer includes a first sub-spacer on the array substrate side and a second sub-spacer on the counter substrate side. The first sub-spacer and the second sub-spacer have an elongated shape in a plan view, and the first sub-spacer and the second sub-spacer overlap so that their longitudinal directions intersect.

[0006] 1A shows a plan view of an electrowetting device according to an embodiment of the present invention; FIG. 1B shows a cross-sectional structure corresponding to the section A1-A2 shown in FIG. 1A; FIG. 1C shows an arrangement of a working electrode and spacers in an electrowetting device according to an embodiment of the present invention; FIG. 1D shows an equivalent circuit of a cell in an electrowetting device according to an embodiment of the present invention; FIG. 1E shows an equivalent circuit of an active region in an electrowetting device according to an embodiment of the present invention; FIG. 1F shows an operation mechanism of an electrowetting device according to an embodiment of the present invention; FIG. 1G shows an example of a planar layout of a cell in an electrowetting device according to an embodiment of the present invention; FIG. 1H shows a cross-sectional structure corresponding to the section B1-B2 shown in FIG. 6A; FIG. 1J shows an arrangement of a working electrode and spacers in an electrowetting device according to an embodiment of the present invention; FIG. 1J shows a plan view of an electrowetting device according to an embodiment of the present invention; FIG. 1J shows a cross-sectional structure corresponding to the section C1-C2 shown in FIG. 8A; FIG. 1J shows a partial cross-sectional structure of an electrowetting device according to an embodiment of the present invention; FIG. 1J shows a plan view of an electrowetting device according to an embodiment of the present invention; FIG. 1J shows a cross-sectional structure corresponding to the section D1-D2 shown in FIG. 10A; FIG. 1J shows a plan view of an electrowetting device according to an embodiment of the present invention; FIG. 1J shows a cross-sectional structure corresponding to the section E1-E2 shown in FIG.

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different forms, and should not be construed as being limited to the description of the following exemplary embodiments. For clarity of explanation, the drawings may show schematic representations of the width, thickness, shape, etc. of each part compared to the actual form. However, these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those previously described with reference to the preceding drawings are designated by the same reference numerals (or reference numerals with A, B, etc. suffixed thereto), and detailed descriptions may be omitted as appropriate. Furthermore, the letters "first" and "second" attached to each element are convenient labels used to distinguish each element and have no further meaning unless otherwise specified.

[0008] In this specification, when a component or region is referred to as being "on (or under)" another component or region, unless otherwise specified, this includes not only the case where it is directly above (or directly under) the other component or region, but also the case where it is above (or under) the other component or region, i.e., the case where another component is included between the component or region and above (or under) the other component or region.

[0009] 1A and 1B show the configuration of an electrowetting device 100 according to one embodiment of the present invention. FIG. 1A shows a plan view of the electrowetting device 100, and FIG. 1B shows a cross-sectional view corresponding to the line A1-A2 shown in the plan view. The electrowetting device 100 is a device that manipulates a fluid sample by the action of an electric field. The electrowetting device 100 is also called a microchannel chip or a lab-on-a-chip. The electrowetting device 100 can be used to analyze minute amounts of liquid samples, perform chemical reactions, and the like.

[0010] In this embodiment, the "analyte" refers to a substance having fluidity that causes electrowetting, specifically a liquid. In other words, the contact angle of the analyte on the surface it comes into contact with changes as a result of the operation of the electrowetting device 100, and the spread of the analyte on the contact surface also changes. Because the analyte is dropped into the injection port of the electrowetting device 100, it can also be read as a "droplet" in this embodiment.

[0011] Examples of specimens include liquids containing antibiotic-resistant pathogens such as methicillin-resistant Staphylococcus aureus (MESA), globular proteins such as human serum albumin (HSA), vegetative bacteria such as Escherichia coli, bacterial algae such as Bacillus atrophaeus (BG), and viruses such as bacteriophage viruses. Note that these examples are merely examples, and the electrowetting device 100 according to this embodiment can handle a variety of fluid substances.

[0012] The electrowetting device 100 has an array substrate 150 and a counter substrate 152. The array substrate 150 and the counter substrate 152 are disposed opposite each other and fixed together using a sealant 154. The array substrate 150 and the counter substrate 152 are disposed so that their opposing surfaces are spaced apart. A spacer 156 is provided in the space between the array substrate 150 and the counter substrate 152. The spacer 156 is provided to maintain a constant distance between the array substrate 150 and the counter substrate 152. A plurality of working electrodes 102, drive circuits (a first drive circuit 106A, a second drive circuit 106B), a power supply terminal 107, a signal terminal 108, etc. are provided on the surface of the array substrate 150 facing the counter substrate 152. A counter electrode 104 is provided on the counter substrate 152.

[0013] The array substrate 150 and the counter substrate 152 provide physical strength to the electrowetting device 100, as well as surfaces for forming a flow path for the analyte and controlling its flow. The materials for forming the array substrate 150 and the counter substrate 152 are not limited, and insulating substrates such as glass substrates, quartz substrates, plastic substrates containing polymers such as polyimide and polycarbonate, and metal substrates such as aluminum and stainless steel may be used. One or both of the array substrate 150 and the counter substrate 152 may be flexible. It is preferable that one or both of the array substrate 150 and the counter substrate 152 be configured to transmit light in at least a portion of the visible light spectrum. The transparency of one or both of the array substrate 150 and the counter substrate 152 allows the flow of the analyte to be visually observed, and the state of the analyte can be observed and analyzed using an optical microscope or various spectroscopes.

[0014] The sizes of the array substrate 150 and the counter substrate 152 can be determined arbitrarily. The length of one side of the array substrate 150 and the counter substrate 152 can be, for example, 10 mm or more and 200 mm or less. A part of the array substrate 150 is exposed from the counter substrate 152, and the power terminals 107, signal terminals 108, etc. are provided on the exposed part.

[0015] Although there is no limitation on the distance between the array substrate 150 and the counter substrate 152, it is preferable that the distance be in the range of, for example, 10 μm to 30 μm inclusive in order to form a cell sandwiching the sample and ensure smooth sample flow. The size of the internal space formed by the separation between the array substrate 150 and the counter substrate 152 is, to be precise, the distance from the surface of the first insulating layer 116A to the surface of the second insulating layer 116B. However, the thicknesses of the first insulating layer 116A, the second insulating layer 116B, the working electrode 102, the counter electrode 104, and other components are 1 μm or less, which is sufficiently small compared to the size of the gap and can be ignored. Therefore, the size of the internal space formed between the array substrate 150 and the counter substrate 152 can be considered to be the distance from the substrate surface on the array substrate 150 side to the substrate surface on the counter substrate 152 side.

[0016] The electrowetting device 100 can control the flow of an analyte in a region where the working electrodes 102 are arranged. In this embodiment, the region where the working electrodes 102 are arranged is also referred to as an working region 101.

[0017] 1A, spacers 156 are disposed in the working region 101. The spacers 156 are disposed discretely within the working region 101. The spacers 156 are provided to maintain a constant distance between the array substrate 150 and the counter substrate 152 and to stabilize the structure. The spacers 156 are preferably disposed at positions that do not overlap with the working electrodes 102 so as not to impede the flow of the analyte 200.

[0018] The spacer 156 can be formed using a resin material. It is sufficient for the spacer 156 to be provided on one side of the array substrate 150 or the counter substrate 152. However, in a preferred embodiment of the present invention, the spacer 156 is formed of a material provided on both the array substrate 150 and the counter substrate 152. That is, as shown in FIG. 1B , the spacer 156 is formed by combining a first sub-spacer 156A on the array substrate 150 side and a second sub-spacer 156B on the counter substrate 152 side. Because the electrowetting device 100 has a relatively large gap between the array substrate 150 and the counter substrate 152, rather than providing a single spacer, providing sub-spacers on each of the two opposing substrates and stacking them to function as a single spacer allows for the individual sub-spacers to be made smaller, thereby enabling miniaturization. Furthermore, the spacer 156 is made of, for example, an acrylic resin, and its surface is water-repellent. Therefore, the sample is not trapped on the surface of the spacer 156, and its flow is not hindered by the spacer 156.

[0019] The configuration of the sealant 154 that bonds the array substrate 150 and the counter substrate 152 is not limited. FIG. 1A shows a structure in which the sealant 154 is provided along the contour of the counter substrate 152. The sealant 154 may be formed in a continuous pattern as a whole, or may be formed in a partially or entirely discontinuous pattern (dotted line or dot pattern). Since the electrowetting device 100 does not need to constantly retain a sample in the action region 101, the sealant 154 may have a discontinuous structure (e.g., dot or dot pattern). On the other hand, when filling the action space of the electrowetting device 100 with hydrophobic oil or the like, it is preferable that the sealant 154 have a closed shape that forms a continuous contour.

[0020] At least two openings are provided in the opposing substrate 152. Figures 1A and 1B show a structure in which a first opening 114A and a second opening 114B are provided in the opposing substrate 152. In this embodiment, the first opening 114A is used as an inlet for injecting a sample, and the second opening 114B is used as an outlet for discharging the sample. A dropper, pipette, micropipette, syringe, or the like may be used to supply the sample to the first opening 114A and collect the sample from the second opening 114B.

[0021] The first opening 114A and the second opening 114B are formed by through holes provided in the counter substrate 152. The first opening 114A and the second opening 114B may be replaced with cutout portions instead of through holes. The cutout portion is a portion formed by cutting out a part of the counter substrate 152 from the outer periphery, and its outline forms part of the outer periphery of the counter substrate 152.

[0022] The first drive circuit 106A and the second drive circuit 106B are provided on the array substrate 150. The first drive circuit 106A and the second drive circuit 106B are electrically connected to a power supply terminal 107 and a signal terminal 108 by wiring (not shown). The power supply terminal 107 and the signal terminal 108 are electrically connected to an external control circuit board via a flexible printed circuit (FPC) (not shown). A control signal output from the external control circuit board is input to the signal terminal 108, and power for driving the electrowetting device 100 is input to the power supply terminal 107.

[0023] As shown in FIG. 1B , thin film transistors 118 are provided on the array substrate 150. A working voltage is applied to each of the working electrodes 102 individually via the thin film transistors 118. The first driving circuit 106A is a circuit that outputs a signal (selection signal) that controls the on / off of the thin film transistor 118, and the second driving circuit 106B may be a circuit that outputs a working voltage to each of the working electrodes 102 via the thin film transistor 118. An n-channel thin film transistor is preferably used as the thin film transistor 118. N-channel thin film transistors are a preferable choice because they have a lower midgap defect density (deep defect level density) than p-channel thin film transistors.

[0024] An area where one working electrode 102 and one counter electrode 104 form a pair is a basic unit for exerting the function of the electrowetting device 100. Therefore, in this embodiment, an area where one working electrode 102 and one counter electrode 104 form a pair is called a "cell 110."

[0025] Although FIG. 1A illustrates an example in which the first drive circuit 106A is disposed on one side of the working region 101 in which the working electrodes 102 are arranged, the first drive circuit 106A may be disposed on both sides of the working region 101. The first drive circuit 106A and the second drive circuit 106B may be formed by thin-film transistors on the array substrate 150, or may be formed by semiconductor integrated circuit chips (IC chips) mounted on the array substrate 150. Although omitted from FIGS. 1A and 1B , first wiring and second wiring are disposed on the array substrate 150 according to the arrangement of the working electrodes 102. The first wiring may be a selection signal line through which a signal for selecting the working electrode 102 is transmitted, and the second wiring may be a control signal line through which a control signal (working voltage) is applied to the working electrode 102. The selection signal line is connected to the first drive circuit 106A, and the control signal line is connected to the second drive circuit 106B. The relationship between the first wiring and the second wiring and the selection signal line 120 and the control signal line 122 is for convenience, and the above relationship may be reversed.

[0026] 1A and 1B, wiring such as a selection signal line, a control signal line, a common wiring, and a capacitance wiring is disposed in the active region 101. The selection signal line is a wiring extending from the first drive circuit 106A, and the control signal line is a wiring extending from the second drive circuit 106B. The common wiring is a wiring for controlling the potential of the opposing electrode 104, and the capacitance wiring is a wiring connected to a capacitance element described later.

[0027] The working electrodes 102 provided on the array substrate 150 are arranged in a matrix. A counter electrode 104 is arranged on the counter substrate 152. The counter electrode 104 is arranged so as to overlap the entire area in which the working electrodes 102 are arranged, excluding the areas of the first opening 114A and the second opening 114B. The working electrodes 102 and counter electrodes 104 arranged in a matrix form an working region 101 that controls the flow of the sample.

[0028] A first insulating layer 116A is provided on the array substrate 150 to cover the working electrode 102, and a second insulating layer 116B is provided on the counter substrate 152 to cover the counter electrode 104. The counter electrode 104 is provided to extend to (or close to) the opening edges of the first opening 114A and the second opening 114B, and preferably is covered with the second insulating layer 116B in this area to prevent the side edges of the counter electrode 104 from being exposed. This structure prevents corrosion of the counter electrode 104, which may occur depending on the type of analyte or reagent. Note that FIG. 1B shows a structure in which the second insulating layer 116B extends to the inner walls of the first opening 114A and the second opening 114B (the inner wall surfaces of the counter substrate 152). However, the illustrated structure is merely an example, and any structure in which the second insulating layer 116B covers the side edges of the counter electrode 104 may be used; the structure shown in FIG. 1B is not limited to this. The surfaces of the first insulating layer 116A and the second insulating layer 116B are water-repellent. The first insulating layer 116A and the second insulating layer 116B may be formed of a material that is water-repellent itself, or the surfaces may be subjected to a water-repellent treatment.

[0029] 1B shows a structure in which a first sub-spacer 156A is provided on the first insulating layer 116A and a second sub-spacer 156B is provided on the second insulating layer 116B. The first sub-spacer 156A may be disposed below the first insulating layer 116A, and the second sub-spacer 156B may be disposed below the second insulating layer 116B.

[0030] FIG. 2 shows an arrangement of working electrodes 102 arranged in m rows and n columns (m and n are natural numbers greater than or equal to 4). In other words, n working electrodes 102 are arranged along a first direction D1, and m working electrodes 102 are arranged along a second direction D2. A first signal line (selection signal line 120) extending in the first direction D1 and a second signal line (control signal line 122) extending in the second direction D2 are provided corresponding to the arrangement of the working electrodes 102. The working electrodes 102 include working electrodes 102A_1 and 102A_2 arranged in a region overlapping the first opening 114A and the second opening 114B, and working electrode 102B arranged in a region sandwiched between the first opening 114A and the second opening 114B. This arrangement of the working electrodes 102 forms an active region 101 for manipulating an analyte.

[0031] The working electrodes 102A_1 and 102A_2 and the working electrode 102B have different sizes (areas) in a plan view. Specifically, the size (area) of the working electrodes 102A_1 and 102A_2 arranged in the first and mth rows is larger than the size (area) of the working electrodes 102B arranged in the second to m-1th rows. Therefore, even if the working electrode 102A_1 arranged in the first row overlaps with the first opening 114A and the working electrode 102A_2 arranged in the mth row overlaps with the second opening 114B, and thus has an area partially exposed from the counter electrode 104 (see FIGS. 1A and 1B ), other areas can be made to overlap with the counter electrode 104. With such an electrode shape and electrode arrangement, a sample can be injected through the first opening 114A (injection port), and the injected sample can be reliably introduced into the region facing the working electrode 102B and the counter electrode 104 at a distance by utilizing capillary action.

[0032] By individually controlling the voltages applied to the working electrodes 102B arranged in the second to (m-1)th rows, it is possible to manipulate the flow of the specimen in the working region 101 sandwiched between the working electrodes 102B and the counter electrode 104. The flowed specimen can then be moved to the second opening 114B (discharge port), and the specimen can be collected and discharged using a pipette, syringe, or the like.

[0033] 2 schematically shows the arrangement of the spacers 156 (first sub-spacers 156A and second sub-spacers 156B). Here, the first sub-spacer 156A is provided on the array substrate 150 side, and the second sub-spacer 156B is provided on the counter substrate 152 side. The first sub-spacer 156A and the second sub-spacer 156B are arranged to overlap each other, constituting a single spacer 156. The first sub-spacer 156A and the second sub-spacer 156B are arranged in the region where the selection signal line 120 and the control signal line 122 intersect.

[0034] The first sub-spacer 156A and the second sub-spacer 156B preferably have shapes with different lengths in the first direction D1 and the second direction D2. Specifically, the first sub-spacer 156A has a length in the direction in which the selection signal lines 120 extend (length in the first direction D1) that is greater than the length in the direction in which the control signal lines 122 extend (length in the second direction D2), and the second sub-spacer 156B has a length in the direction in which the control signal lines 122 extend (length in the first direction D1) that is greater than the length in the direction in which the selection signal lines 120 extend (length in the first direction D1). The first sub-spacer 156A and the second sub-spacer 156B are arranged so that their longitudinal directions intersect. This configuration ensures that the first sub-spacer 156A and the second sub-spacer 156B can be reliably superimposed even if there is some misalignment when the array substrate 150 and the counter substrate 152 are bonded together. As described above, by making the shapes of the first sub-spacer 156A and the second sub-spacer 156B elongated along the selection signal line 120 and the control signal line 122, it is possible to avoid overlapping with the working electrode 102 and to avoid impeding the movement (flow) of the sample, while ensuring the necessary size as a spacer.

[0035] The areas of the working electrodes 102A_1 and 102A_2 arranged in the first and m-th rows are larger than the areas of the working electrodes 102B arranged in the second to (m-1)-th rows. Therefore, in order to more significantly change the contact angle of the analyte on the working electrode 102A_1 arranged in the first row and more efficiently transfer the analyte to the working electrode 102B in the second row or smoothly transfer the analyte from the working electrode 102B in the (m-1)-th row to the working electrode 102A_2 in the m-th row, it is necessary to drive the working electrodes 102A_1 and 102A_2 arranged in the first and m-th rows so that the rise rate when a working voltage is applied to them is the same as the rise rate when a working voltage is applied to the working electrodes 102B in the second to (m-1)-th rows.

[0036] To this end, the first drive circuit 106A may be configured so that the voltage of the selection signal applied to the working electrodes 102A_1 and 102A_2 arranged in the first and mth rows is greater than the voltage of the selection signal applied to the working electrodes 102B arranged in the second to (n-1)th rows.

[0037] FIG. 3 shows an equivalent circuit of 110. The equivalent circuit shown in FIG. 3 schematically illustrates a configuration in which the working electrode 102 and the counter electrode 104 are arranged opposite each other. The working electrode 102 is connected to a thin-film transistor 118. The thin-film transistor 118 has a gate, a source, and a drain. The selection signal line 120 is a signal line extending from the first drive circuit 106A and connected to the gate of the thin-film transistor 118. The control signal line 122 is a signal line extending from the second drive circuit 106B and connected to one of the source and drain of the thin-film transistor 118. The other of the source and drain is connected to the working electrode 102. In other words, the control terminal (gate) of the thin-film transistor 118 is connected to the selection signal line 120, one of the input / output terminals is connected to the control signal line 122, and the other of the input / output terminals is connected to the working electrode 102.

[0038] A capacitance element 126 is connected to the thin film transistor 118 in parallel with the working electrode 102. The capacitance element 126 is provided to hold the voltage applied to the working electrode 102 for a certain period of time. The counter electrode 104 is connected to the common wiring 124. As described with reference to FIG. 2 , a spacer 156 is provided in the region where the selection signal line 120 and the control signal line 122 intersect.

[0039] The thin film transistor 118 is turned on when a selection signal is input from the selection signal line 120. When a control signal is applied from the control signal line 122 in synchronization with this, an operating voltage is applied to the working electrode 102 via the thin film transistor 118. At the same time, the capacitive element 126 is charged with the operating voltage. Meanwhile, a predetermined voltage is applied to the counter electrode 104 from the common wiring 124. As described with reference to FIG. 2, the working electrodes 102 are arranged in a matrix. In other words, the cells 110 are arranged in a matrix in the working region 101. Each cell 110 has the circuit configuration shown in FIG. 3, and therefore the state of each cell 110 can be individually controlled by the first drive circuit 106A and the second drive circuit 106B.

[0040] FIG. 4 shows an equivalent circuit of the active region 101 in which the cells 110 are arranged in m rows and n columns. The circuit configuration of each cell 110 is the same as that of the equivalent circuit shown in FIG. 3. In the active region 101, selection signal lines 120_1 to 120_m extending from the first drive circuit 106A and control signal lines 122_1 to 122_n extending from the second drive circuit 106B are arranged. Spacers 156 are provided in areas where the selection signal lines 120_1 to 120_m and the control signal lines 122_1 to 122_n intersect. The spacers 156 do not need to be provided at all intersections between the selection signal lines 120_1 to 120_m and the control signal lines 122_1 to 122_n, but can be provided discretely as appropriate.

[0041] The electrowetting device 100 sequentially outputs selection signals from the first drive circuit 106A to the selection signal lines 120_1 to 120_m, and in synchronization with this operation, outputs control signals from the second drive circuit 106B to the control signal lines 122_1 to 122_n, thereby controlling the change in the potential of the working electrode 102 of each cell 110.

[0042] FIG. 5 is a diagram illustrating the operating principle of the electrowetting device 100. FIG. 5 shows a state in which an analyte 200 is sandwiched between the working electrodes 102B_1 to 102B_3 and the counter electrode 104 (actually, between the first insulating layer 116A and the second insulating layer 116B). The working electrodes 102B_1 to 102B_3 are arranged on the array substrate 150, and each working electrode is connected to a corresponding thin-film transistor 118B_1 to 118B_3. The thin-film transistors 118B_1 to 118B_2 are connected to a power source EV1. When any of the thin-film transistors 118B_1 to 118B_3 is turned on, a predetermined working voltage is applied from the power source EV1 to the working electrodes 102B_1 to 102B_3 connected to the transistor. Meanwhile, the counter electrode 104 is connected to a switch SW1, and can be switched between a grounded state and a state connected to a power source EV2 by operating the switch SW1.

[0043] The manipulation (flow control) of the analyte 200 is performed by temporally changing the potentials of the working electrodes 102B_1 to 102B_3 and the counter electrode 104. Fig. 5 shows a state in which the analyte 200 is sandwiched between the array substrate 150 and the counter substrate 152. State A indicated by the dotted line shows a state in which the thin film transistors 118B_1 to 118B_3 are all off, and state B shows a state in which the thin film transistor 118B_1 is off and the thin film transistors 118B_2 and 118B_3 are on.

[0044] The analyte 200 contacts the first insulating layer 116A and the second insulating layer 116B. However, because the first insulating layer 116A and the second insulating layer 116B have water-repellent surfaces, the contact angle of the analyte 200 is large in State A when no voltage is applied to the working electrode 102A_1. On the other hand, when a voltage EV1 is applied to the working electrode 102A_1, as shown in State B, the negative charge of the analyte 200 is attracted toward the working electrodes 102B_1 to 102B_3, making the contact angle relatively smaller than in State A and increasing wettability. As a result, the analyte 200 in State B spreads from the working electrode 102B_1 side to the working electrode 102B_3 side. By such control, the analyte 200 can be moved from the working electrode 102B_1 side to the working electrode 102B_3 side.

[0045] The contact angle of the analyte 200 with respect to the first insulating layer 116A changes reversibly depending on whether or not a voltage is applied to the working electrodes 102B_1 to 102B_3. In other words, the change from state A to state B and the change from state B to state A can be controlled by the voltage applied to the working electrodes 102B_1 to 102B_3.

[0046] Furthermore, when the counter electrode 104 is connected to the power supply EV2 and the potential of the power supply EV1 is made lower than the potential of the power supply EV2, a phenomenon opposite to that described above occurs. That is, the positive charge of the analyte 200 is attracted to the working electrodes 102B_1 to 102B_3, the contact angle of the analyte 200 decreases, and the analyte 200 can be moved in the same manner. The state in which the counter electrode 104 is connected to the power supply EV2 is the opposite state to the state in which the counter electrode 104 is grounded, and therefore can also be called inversion driving. By alternately switching the potential of the counter electrode 104 between the ground potential and a potential based on the power supply EV2, or by intermittently switching it, it is also possible to invert the direction of the electric field acting on the analyte 200.

[0047] In the working region 101 shown in Fig. 4, the working electrodes 102 of the cell 110 can be individually controlled, and therefore the operations on the analyte described in Fig. 5 can be performed in the same manner. That is, the analyte can move freely within the working region 101. When performing such operations, it is preferable to place a spacer 156 in the region between the working electrodes 102 so as not to hinder the flow of the analyte.

[0048] 6A is an example of a planar layout of the cell 110, and shows the arrangement of the working electrode 102, thin film transistor 118, selection signal line 120, control signal line 122, capacitance element 126, and spacer 156 (first sub-spacer 156A, second sub-spacer 156B) provided on the array substrate 150. FIG. 6B shows a cross-sectional structure corresponding to the section B1-B2 shown in FIG. 6A. Note that the counter electrode 104 is omitted in FIG. 6A.

[0049] As shown in FIG. 6B , a thin film transistor 118B is provided on the array substrate 150 directly or via an optional underlying insulating layer 130. The structure of the thin film transistor 118B is not limited, and various structures such as a top-gate type, a bottom-gate type, or a dual-gate type can be applied. The example shown in FIG. 6B illustrates an example in which a top-gate type structure is adopted for the thin film transistor 118B. Specifically, the thin film transistor 118B includes a semiconductor layer 1182, a gate insulating layer 1184 covering the semiconductor layer 1182, and a gate electrode 1186 overlapping the semiconductor layer 1182 via the gate insulating layer 1184.

[0050] The gate electrode 1186 of the thin film transistor 118B is formed from the same conductive layer as the selection signal line 120. FIG. 6A shows a pattern in which the semiconductor layer 1182 is bent so as to intersect with the selection signal line 120. The region where the semiconductor layer 1182 intersects with the selection signal line 120 functions as the gate electrode 1186. The thin film transistor 118B is connected to a first input / output electrode 136 and a second input / output electrode 138. The first input / output electrode 136 is connected to one of the source region and the drain region formed in the semiconductor layer 1182, and the second input / output electrode 138 is connected to the other of the source region and the drain region. The first input / output electrode 136 essentially doubles as the control signal line 122 (see FIG. 3 ). The first input / output electrode 136 and the second input / output electrode 138 are provided via an interlayer insulating layer 132 that covers the gate electrode 1186.

[0051] A planarization layer 134 is provided on the upper layer side of the thin film transistor 118B. By providing the planarization layer 134, structures such as the thin film transistor 118B can be embedded to form a flat surface. The working electrode 102B is provided on the planarization layer 134. The working electrode 102B has a flat surface except for the region of a contact hole that forms a connection with the second input / output electrode 138.

[0052] The capacitance element 126 is formed by the working electrode 102, the capacitance wiring 140, and the planarization layer 134 between the working electrode 102 and the capacitance wiring 140. Note that the structure of the capacitance element 126 shown in Figures 6A and 6B is an example and is not limited to the structure shown. For example, the capacitance element 126 can be formed using the same layer as the semiconductor layer 1182, the gate insulating layer 1184, and the gate electrode 1186, or can be formed using the same layer as the gate electrode 1186, the interlayer insulating layer 132, and the first input / output electrode 136. The capacitance element 126 is provided to maintain the potential of the working electrode 102B.

[0053] A first insulating layer 116A is provided on the array substrate 150 so as to cover the working electrode 102B. The first insulating layer 116A has a water-repellent surface. The first insulating layer 116A is formed of, for example, a silicon nitride film. Alternatively, the first insulating layer 116A may be formed by coating the surface of an insulating film (for example, an inorganic insulating film such as a silicon oxide film or a silicon nitride film, or an organic resin film such as a polyimide or an acrylic resin) with a thin fluorine film by fluorine plasma treatment to form a water-repellent surface, or by coating the surface with a thin hydrocarbon film to form a water-repellent surface.

[0054] A counter electrode 104 is provided on the counter substrate 152. The counter electrode 104 is connected to a common wiring provided on the array substrate 150 by a conductive member (not shown). A second insulating layer 116B is provided on the counter substrate 152 so as to cover the counter electrode 104. The second insulating layer 116B has a water-repellent surface, similar to the first insulating layer 116A.

[0055] A spacer 156 is provided between the array substrate 150 and the counter substrate 152. The spacer 156 is composed of a first sub-spacer 156A on the array substrate 150 side and a second sub-spacer 156B on the counter substrate side. The first sub-spacer 156A and the second sub-spacer 156B are formed of a resin material. The resin material may be an acrylic or polyimide resin material. These resin materials are preferably photosensitive resin materials. Using a photosensitive resin material allows for precise control of the positions of the first sub-spacer 156A and the second sub-spacer 156B. The heights of the first sub-spacer 156A and the second sub-spacer 156B are preferably such that the tops of the two sub-spacers touch when stacked. For example, if the array substrate 150 and the counter substrate 152 are separated by a distance S1, the heights of the first sub-spacer 156A and the second sub-spacer 156B are preferably half the length S1.

[0056] The first sub-spacer 156A and the second sub-spacer 156B preferably have a shape in plan view in which the length in one direction and the length intersecting the one direction are different, such as a rectangle or an oblong, as shown in Fig. 6A. The first sub-spacer 156A and the second sub-spacer 156B are preferably arranged so that their longitudinal directions intersect.

[0057] 6A shows an example in which the longitudinal direction of the first sub-spacer 156A is arranged along the selection signal line 120, and the longitudinal direction of the second sub-spacer 156B is arranged along the control signal line 122. The arrangement of the sub-spacers is not limited to this example, and the first sub-spacer 156A may be arranged along the control signal line 122, and the second sub-spacer 156B may be arranged along the selection signal line 120.

[0058] The layers provided on the array substrate 150 and the counter substrate 152 are formed using the following materials. The semiconductor layer 1182 is formed of a silicon semiconductor such as amorphous silicon or polycrystalline silicon, or an oxide semiconductor including a metal oxide such as indium oxide, zinc oxide, or gallium oxide. The gate insulating layer 1184 and the interlayer insulating layer 132 are formed of an insulating material that can be formed into a thin film. For example, the gate insulating layer 1184 and the interlayer insulating layer 132 are formed using a silicon oxide film or a silicon nitride film, and are formed as a single layer of these films or a stacked structure of these films. The gate electrode 1186 (and the selection signal line 120) is formed using a conductive material, such as molybdenum (Mo), tungsten (W), or an alloy thereof. The first input / output electrode 136 and the second input / output electrode 138 (and the control signal line 122) are formed using a conductive material, such as a titanium (Ti) / aluminum (Al) / titanium (Ti) stacked structure or a molybdenum (Mo) / aluminum (Al) / molybdenum (Mo) stacked structure. The planarization layer 134 may be formed using any material that is flat and insulating after formation, such as an organic insulating material. Examples of organic insulating materials include acrylic resins, epoxy resins, and polyimide materials. The working electrode 102B and the counter electrode 104 are formed using a metal material or a conductive material (transparent conductive film material) that becomes transparent when formed into a thin film. Examples of metal materials include aluminum (Al). Examples of transparent conductive film materials include indium tin oxide (ITO), zinc oxide (ZnO), and indium zinc oxide (IZO).

[0059] By distributing the spacers 156 between the array substrate 150 and the counter substrate 152, it is possible to maintain a constant gap (separation distance) between the array substrate 150 and the counter substrate 152. Even when the gap (separation distance) between the array substrate 150 and the counter substrate 152 is large, such as 10 μm to 30 μm, by configuring the spacer 156 with a first sub-spacer 156A on the array substrate 150 side and a second sub-spacer 156B on the counter substrate 152 side, it is possible to prevent the spacer from becoming thick and to process it into a fine shape.

[0060] When manipulating an analyte using the electrowetting device 100, for example, the analyte is supplied through the first opening 114A, moved in a predetermined direction in the action region 101, and finally discharged through the second opening 114B. In the action region 101, the path along which the analyte moves (flows) can be freely set by controlling the voltage applied to the working electrode 102B. Alternatively, the path along which the analyte moves (flows) in the action region 101 may be predetermined. In such cases, the spacer 156 may be provided to extend along the path along which the analyte moves (flows). For example, as shown in FIG. 7 , first sub-spacers 156A_1 and 156A_2 may be provided extending continuously from the first opening 114A_1 toward the second opening 114B along the second direction D2. By providing such first sub-spacers 156A_1 and 156A_2 and using them as physical partitions, it is possible to prevent the analyte from flowing in an unintended direction.

[0061] FIG. 7 illustrates a structure in which the first sub-spacers 156A_1 and 156A_2 are continuous from the working electrode 102A_1 side to the working electrode 102B_1 side, but the length of the first sub-spacer 156A is not limited. For example, if it is planned to mix two analytes along the path, the first sub-spacer 156A may have a structure in which the path extending in the second direction D2 is interrupted along the path, such as the first sub-spacers 156A_n and 156A_n+1. In this manner, by appropriately adjusting the length of the first sub-spacer 156A, the path along which the analyte flows can be set. Note that while FIG. 7 illustrates a structure in which a flow path is formed by the first sub-spacer 156A, a similar structure may be formed by the second sub-spacer 156B. Furthermore, a similar structure may be formed using both the first sub-spacer 156A and the second sub-spacer 156B.

[0062] 8A and 8B show the electrowetting device 100 provided with an auxiliary spacer 158 in addition to the spacer 156. Fig. 8A shows a plan view of the electrowetting device 100, and Fig. 8B shows a cross-sectional view corresponding to the section C1-C2 shown in the plan view.

[0063] 8A and 8B , spacers 156 are arranged discretely in the active region 101. In addition, auxiliary spacers 158 are arranged discretely. The spacers 156 and auxiliary spacers 158 are arranged in an area that does not overlap with the working electrode 102. The auxiliary spacers 158 are arranged between areas where the spacers 156 are spaced apart in the active region 101 so as not to be close to the spacers 156. Although FIG. 8B shows a structure in which the auxiliary spacers 158 are arranged on the opposing substrate 152 side, the auxiliary spacers 158 may also be provided on the array substrate 150 side.

[0064] As shown in the inset of FIG. 8B , the spacer 156 and the auxiliary spacer 158 have different heights. The spacer 156 is composed of a first sub-spacer 156A and a second sub-spacer 156B. The height T1 at which the two sub-spacers overlap is substantially the same as the distance S1 between the array substrate 150 and the counter substrate 152. Meanwhile, the height T2 of the auxiliary spacer 158 is smaller than the distance S1. Therefore, the spacer 156 contacts both the array substrate 150 and the counter substrate 152, whereas the auxiliary spacer 158 contacts the counter substrate 152 but does not contact the array substrate 150 (when the auxiliary spacer 158 is provided on the array substrate 150 side, it does not contact the counter substrate 152). There are no limitations on the height T2 of the auxiliary spacer 158, but it is preferably 50% to 80% of the height T1 of the spacer 156.

[0065] Although the auxiliary spacers 158 normally contact only one of the substrates, when an external force acts between the array substrate 150 and the counter substrate 152 to narrow the gap S1, the auxiliary spacers 158 come into contact with both the counter substrate 152 and the array substrate 150, generating a counter force against the external force. As a result, excessive deformation of the array substrate 150 and the counter substrate 152 can be prevented, and narrowing of the gap S1 can be suppressed and stabilized. In other words, even when the number of spacers 156 is reduced to a certain extent, the placement of the auxiliary spacers 158 can stabilize the gap S1 between the array substrate 150 and the counter substrate 152.

[0066] On the other hand, since the electrowetting device 100 is a device that moves (flows) the analyte in the gap between the array substrate 150 and the opposing substrate 152, it is desirable to minimize structures that hinder the movement (flow) of the analyte. Because the auxiliary spacer 158 contacts only one of the substrates, it is possible to provide the analyte with space to move (flow) and not hinder the movement (flow).

[0067] In this way, by providing the auxiliary spacer 158 in addition to the spacer 156, the structure of the electrowetting device 100 can be stabilized while ensuring the fluidity of the specimen.

[0068] 9 is a schematic cross-sectional view of the cell 110 of the electrowetting device 100, showing the cross-sectional structure of the region where the working electrode 102A_1 is provided. The working electrode 102A_1 is similar to the working electrode 102B shown in FIG. 6B except for the area in a plan view. Therefore, the thin-film transistor 118A_1 connected to the working electrode 102A_1 has the same configuration as the thin-film transistor 118B shown in FIG. 6B.

[0069] Meanwhile, a first opening 114A is provided in the counter substrate 152 in a region overlapping with the working electrode 102A_1. The working electrode 102A_1 is disposed so as to partially overlap with the first opening 114A. In other words, a portion of the working electrode 102A_1 is exposed to the outside through the first opening 114A. In the region of the working electrode 102A_1 that does not overlap with the first opening 114A, it overlaps with the counter electrode 104. Note that FIG. 9 illustrates a structure in which the end of the counter electrode 104 does not reach the opening edge of the first opening 114A. In other words, the opening edge of the counter electrode 104 is disposed outside the opening edge of the first opening 114A. In such a structure, the second insulating layer 116B can cover the upper surface and side end surfaces of the counter electrode 104 and further contact the upper surface of the counter substrate 152. The second insulating layer 116B can be structured to be in close contact with the opposing substrate 152 in the region adjacent to the opening end of the first opening 114A, thereby preventing peeling and more reliably preventing deterioration of the opposing electrode 104 due to corrosion, etc.

[0070] 9 , the analyte 200 can be placed on the working electrode 102A_1 by dropping the analyte 200 into the first opening 114A. The analyte 200 flows into the gap between the array substrate 150 and the counter substrate 152 by capillary action and comes into contact with the first insulating layer 116A and the second insulating layer 116B. Because the first insulating layer 116A and the second insulating layer 116B have water-repellent surfaces, the contact angle of the analyte 200 becomes large when no voltage is applied to the working electrode 102A_1.

[0071] In the region where the working electrode 102A_1 is provided, the distance S1 formed between the array substrate 150 and the counter substrate 152 is constant. On the other hand, as shown in Fig. 9 , in the vicinity of the first opening 114A, the planarization layer 134 is removed or thinned in the region outside the working electrode 102A_1, thereby providing a region where the distance between the array substrate 150 and the counter substrate 152 is wider. Fig. 9 shows a structure in which the distance between the array substrate 150 and the counter substrate 152 is substantially wider, resulting in a gap S2 (S2 > S1), due to the planarization layer 134 being thinned in the region outside the working electrode 102A_1 (in other words, in the region near the ends of the array substrate 150 and the counter substrate 152).

[0072] Although not shown, a region having a gap S3 wider than the gap S1 can be provided between the array substrate 150 and the counter substrate 152 by thinning the vicinity of the end of the counter substrate 152.

[0073] In this way, by providing a structure that increases the size of the gap (separation distance) formed between the array substrate 150 and the counter substrate 152 near the opening for supplying the sample, it is possible to make it easier to supply the sample and increase the amount of sample supplied. Although not shown in Fig. 9, by providing a sealant 154 on the outer periphery of the array substrate 150 and the counter substrate 152, it is possible to prevent the sample from leaking out.

[0074] 10A and 10B show another example of an electrowetting device 100 according to an embodiment of the present invention, in which Fig. 10A shows a plan view of the electrowetting device 100, and Fig. 10B shows a cross-sectional view corresponding to the section D1-D2 shown in the plan view.

[0075] The electrowetting device 100 shown in Figures 10A and 10B has a first action region 101A and a second action region 101B. The distance between the array substrate 150 and the opposing substrate 152 is different in the first action region 101A and the second action region 101B. Specifically, as shown in Figure 10B, the first action region 101A has a distance S1, whereas the second action region 101B has a distance S3, with S3 being larger than S1. In this way, the electrowetting device 100 shown in Figures 10A and 10B has a multi-gap structure.

[0076] The gaps of different sizes provided in the action area 101 can be realized by varying the thickness of the opposing substrate 152. That is, the opposing substrate 152 has a thickness TS1 in the first action area 101A and a thickness TS3 in the second action area 101B, with TS1 being larger than TS3. In this way, by having the opposing substrate 152 have a structure with different thicknesses, when the gap in the first action area 101A is S1 and the gap in the second action area 101B is S3, S3 can be larger than S1 (S1<S3).

[0077] Spacers 156 (first sub-spacers 156A, second sub-spacers 156B) of different heights are provided depending on the first action region 101A and the second action region 101B. That is, in the first action region 101A, spacers 156 (first sub-spacers 156A_s1, second sub-spacers 156B_s1) corresponding to the spacing S1 are provided, and in the second action region 101B, spacers 156 (first sub-spacers 156A_s3, second sub-spacers 156B_s3) corresponding to the spacing S3 are provided. For example, when the first sub-spacers 156A_s1 and the first sub-spacers 156A_s3 are formed of a photosensitive resin material on the array substrate 150 side, the heights can be controlled by varying the amount of exposure. The same applies to the second sub-spacers 156B_s1 and the second sub-spacers 156B_s3.

[0078] 10A, the sample can be supplied to the first action area 101A through the first opening 114A_1, and the sample can be supplied to the second action area 101B through the first opening 114A_2. In this case, since the gap of the second action area 101B is wider than that of the first action area 101A, a larger amount of sample can be supplied, and a sample with high viscosity can be supplied.

[0079] The shape of the counter substrate 152 shown in Figure 10B can be formed by etching or grinding and polishing a flat substrate. It is also possible to vary the thickness of the substrate on the array substrate 150 side, but from the perspective of the manufacturing process, it is preferable that the array substrate 150 be flat, since thin film transistors 118 and the like are formed on the array substrate 150. While Figures 10A and 10B show two active regions spaced at different intervals, the number of such regions is not limited, and more regions may be provided.

[0080] 11A and 11B show another example of an electrowetting device 100 according to an embodiment of the present invention, in which Fig. 11A shows a plan view of the electrowetting device 100, and Fig. 11B shows a cross-sectional view corresponding to the section E1-E2 shown in the plan view.

[0081] The electrowetting device 100 shown in Figures 11A and 11B has a multi-gap structure, which is realized by using multiple opposing substrates. Specifically, a first opposing substrate 152A is provided in the first action region 101A, and a second opposing substrate 152B is provided in the second action region 101B. The first opposing substrate 152A and the second opposing substrate 152B are physically separated substrates. The spacing S1 in the first action region 101A and the spacing S3 in the second action region 101B are different, with S3 being larger than S1 (S1 < S3). This size difference can be achieved by providing a first sub-spacer 156A_s1 and a second sub-spacer 156B_s1 in the first action region 101A according to the spacing S1, and providing a first sub-spacer 156A_s3 and a second sub-spacer 156B_s3 in the second action region 101B according to the spacing S3.

[0082] In this way, by using a plurality of opposing substrates, it is possible to realize an electrowetting device 100 having a multi-gap structure. Note that, although Figures 11A and 11B show a structure in which two opposing substrates are provided at different intervals, there is no limit to the number of active regions with different gap sizes, and a multi-gap structure can be achieved by providing opposing substrates at different intervals.

[0083] Note that Figure 11B shows a structure in which the first opposing substrate 152A and the second opposing substrate 152B have different heights in a cross-sectional view, but the heights can be made uniform by reducing the thickness of the second opposing substrate 152B.

[0084] The structures shown in FIGS. 11A and 11B allow for the manipulation of different amounts of specimen depending on the working area, and also for the manipulation of specimens with different viscosities and surface tensions.

[0085] The various configurations of the electrowetting device exemplified as one embodiment of the present invention can be combined as appropriate as long as they are not mutually contradictory. Furthermore, electrowetting devices in which a person skilled in the art appropriately adds or deletes components or modifies the design, or adds or omits steps or modifies conditions, based on the electrowetting device disclosed in this specification and drawings, are also included in the scope of the present invention as long as they include the gist of the present invention.

[0086] Even if there are other effects and advantages different from those brought about by the aspects of the embodiments disclosed in this specification, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention.

[0087] 100: electrowetting device, 101: action region, 101A: first action region, 101B: second action region, 102: working electrode, 104: counter electrode, 105: auxiliary electrode, 106A: first drive circuit, 106B: second drive circuit, 107: power supply terminal, 108: signal terminal, 110: cell, 114A: first opening, 114B: second opening, 116A: first insulating layer, 116B: second insulating layer, 118, 118A-1, 118A-2, 118B: thin film transistor, 1182: semiconductor layer, 1184: gate base insulating layer, 1186: gate electrode, 120: selection signal line, 122: control signal line, 124: common wiring, 126: capacitance element, 130: base insulating layer, 132: interlayer insulating layer, 134: planarization layer, 136: first input / output electrode, 138: second input / output electrode, 140: capacitance wiring, 150: array substrate, 152: opposing substrate, 154: sealing material, 156: spacer, 156A: first sub-spacer, 156B: second sub-spacer, 158: auxiliary spacer, 200: specimen, EV1: power supply, EV2: power supply, SW1: switch

Claims

1. An electrowetting device comprising: an array substrate on which working electrodes are arranged; a counter substrate on which a counter electrode is arranged and which is arranged opposite to and spaced apart from the array substrate; and a spacer between the array substrate and the counter substrate, wherein the counter substrate has a first opening for injecting a sample into a region where the array substrate and the counter substrate are separated, and a second opening for discharging the sample, the spacer having a first sub-spacer on the array substrate side and a second sub-spacer on the counter substrate side, wherein the first sub-spacer and the second sub-spacer have an elongated shape in a planar view, and the first sub-spacer and the second sub-spacer overlap so that their longitudinal directions intersect.

2. An electrowetting device as described in claim 1, wherein the array substrate includes first wiring extending in a first direction and second wiring extending in a second direction intersecting the first direction, and the spacer is arranged in a region where the first wiring and the second wiring intersect.

3. An electrowetting device as described in claim 2, wherein the longitudinal direction of the first sub-spacer is arranged parallel to the direction in which the first wiring extends, and the longitudinal direction of the second sub-spacer is arranged parallel to the direction in which the second wiring extends.

4. An electrowetting device as described in claim 1, wherein the working electrode is arranged continuously from the first opening to the second opening, and one of the first sub-spacer and the second sub-spacer has an elongated shape that is continuous from the first opening to the second opening.

5. The electrowetting device according to claim 1, further comprising an auxiliary spacer disposed between the spacers, the spacer being in contact with both the array substrate and the opposing substrate, and the auxiliary spacer being in contact with one of the array substrate and the opposing substrate.

6. The electrowetting device according to claim 1, wherein the array substrate and the opposing substrate have a plurality of regions with different spacing intervals.

7. The electrowetting device according to claim 6, wherein the opposing substrate includes regions with different thicknesses corresponding to the plurality of regions with different spacings.

8. The electrowetting device according to claim 6, comprising a plurality of opposing substrates spaced apart from the array substrate by different distances in accordance with the plurality of regions with different spacings.

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