Resistance measurement device

Abstract

Provided is technology that can improve measurement accuracy and observability in resistance measurements of biological samples. The present invention is a resistance measurement device (1) for measuring the electrical resistance of a biological sample. The resistance measurement device (1) comprises: a device body; a measurement chamber (10) that is located in the interior of the device body and is capable of storing a liquid; a membrane (20) that is located within the measurement chamber (10) and holds a biological sample; a transparent first electrode (21) that is located above and spaced apart from the membrane (20) and covers the upper side of the measurement chamber (10); and a transparent observation portion that is located above the first electrode (21).

Description

Resistance measurement device

[0001] The subject matter disclosed in this specification relates to a resistance measurement device.

[0002] As a method for evaluating the barrier function of a cell layer forming a membrane structure, the trans-epithelial electrical resistance (TEER) measurement method is widely used. In TEER measurement, cells are cultured in an insert of a porous membrane installed in a culture plate, electrodes are inserted into the plate and the insert to apply a current, and the resistance value of the cell layer is measured by measuring the potential difference.

[0003] Patent Document 1 shows a measuring device equipped with chopstick-type electrodes. However, chopstick-type electrodes require an opening above the culture part and have the limitation that they cannot be applied to devices for culturing cells inside a flow path. Therefore, Patent Documents 2 and Non-Patent Document 1 show methods of providing electrodes on the lid part of a culture container, arranging electrodes above and below the cell culture part in a cell culture flow path device, and performing measurement while maintaining the culture environment. Patent Document 3 also shows a culture device in which planar electrodes are mounted in a flow path by laminating a base material such as a PET material with a metal film formed thereon.

[0004] Japanese Unexamined Patent Application Publication No. 2005-137307, Japanese Patent Application Laid-Open No. 2017-513483, Japanese Unexamined Patent Application Publication No. 2020-137492

[0005] Booth R, Kim H. Characterization of a microfluidic in vitro model of the blood-brain barrier (mu BBB) Lab Chip. 2012;12:1784-1792.

[0006] Conventional devices generally use gold (Au) as electrodes. However, because Au is an impermeable material, it was necessary to leave an area above the cell layer where no electrodes were placed in order to observe the cell layer with a microscope or other means. In this case, the presence of areas not covered by electrodes reduces the uniformity of the electric field. Therefore, due to the non-uniformity of the current density distribution, it may be difficult to accurately measure the average resistance value of the entire cell layer. Thus, with conventional devices using Au electrodes, there is a trade-off between measurement accuracy and cell observationability, and it has been difficult to improve both simultaneously.

[0007] The purpose of this disclosure is to provide a technology that can improve measurement accuracy and observability in resistance measurement of biological samples.

[0008] To solve the above problems, the first embodiment is a resistance measuring device for measuring the electrical resistance of a biological sample, comprising: a device body; a measuring chamber located inside the device body and capable of storing liquid; a holding part located inside the measuring chamber and holding a biological sample; a transparent first electrode located away from the holding part on one side in a first direction and covering one side of the measuring chamber in the first direction; and a transparent observation part located on one side of the first electrode in the first direction.

[0009] A second embodiment is the resistance measuring device of the first embodiment, wherein the first electrode is larger than the measuring chamber in a second direction intersecting the first direction.

[0010] A third embodiment is a resistance measuring device according to the first embodiment, further comprising a second electrode located away from the holding portion on the other side in the first direction and covering the other side of the measuring chamber in the second direction.

[0011] A fourth embodiment is a resistance measuring device according to the first embodiment, further comprising: a flow path communicating with the measuring chamber; a third electrode positioned away from the holding portion on one side in the first direction and arranged in the flow path; and a fourth electrode positioned away from the holding portion on the other side in the first direction and arranged in the flow path.

[0012] A fifth embodiment is a resistance measuring device according to the fourth embodiment, wherein the flow path includes a first flow path located on one side of the holding portion in the first direction and a second flow path located on the other side of the holding portion in the first direction, the third electrode is arranged in the first flow path and the fourth electrode is arranged in the second flow path.

[0013] The sixth aspect is the resistance measuring device of the first aspect, wherein the first electrode is made of indium tin oxide.

[0014] The seventh embodiment is a resistance measuring device according to any one of the first to sixth embodiments, comprising: a first layer on which the measuring chamber is formed; a second layer on which the first electrode is formed and which closes one side of the measuring chamber in the first direction; and a third layer which closes the lower side of the measuring chamber.

[0015] According to the resistance measuring devices of the first to seventh embodiments, since the first electrode is a transparent electrode, the biological sample can be observed even with the first electrode present. Furthermore, since one side of the measurement chamber is covered by the first electrode, the uniformity of the electric field formed within the measurement chamber can be improved. Therefore, the accuracy of resistance measurement and the ability to observe can be improved.

[0016] According to the resistance measuring device of the second embodiment, the allowable range of misalignment of the first electrode with respect to the measuring chamber in the second direction can be expanded during device fabrication.

[0017] According to the resistance measuring device of the third embodiment, a uniform electric field can be formed between the first electrode and the second electrode.

[0018] According to the resistance measuring device of the fourth embodiment, the resistance value can be measured with high accuracy using the four-terminal method.

[0019] According to the resistance measuring device of the sixth embodiment, a transparent electrode with high transmittance of visible light and high conductivity can be formed.

[0020] This is a perspective view of a resistance measuring device according to an embodiment. This is an exploded view of the resistance measuring device shown in Figure 1. This is a cross-sectional view of the resistance measuring device 1 at the position A-A in Figure 1. This is a cross-sectional view of the resistance measuring device 1 at the position B-B in Figure 1. This is a cross-sectional view of the resistance measuring device 1 at the position C-C in Figure 1. This is a bottom view of the second substrate shown in Figure 1. This is a top view of the fifth substrate shown in Figure 1. This is a diagram showing the equivalent circuit when measuring electrical resistance using the resistance measuring device.

[0021] Embodiments of the present invention will be described below with reference to the attached drawings. Note that in the drawings, the dimensions and number of parts may be exaggerated or simplified for ease of understanding.

[0022] In the following explanation, the surface of the membrane 20 of the resistance measuring device 1 is used as a reference point. Two directions parallel to this surface and perpendicular to each other are defined as the X direction (second direction) and the Y direction (third direction), while the direction perpendicular to this surface (normal direction) is defined as the Z direction (first direction). In addition, the direction in which the tip of the arrow shown in each figure points is defined as the + (plus) direction, and the opposite direction is defined as the - (minus) direction. Furthermore, the +Z direction is defined as upward, and the -Z direction is defined as downward. Note that these directions are used for the purpose of facilitating understanding and are not intended to limit the positional relationship of the resistance measuring device.

[0023] Expressions indicating relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) shall, unless otherwise specified, not only strictly represent the positional relationship but also represent a state in which the object has been displaced relative to an angle or distance within a tolerance or a range in which an equivalent function can be obtained. Similarly, expressions indicating shape (e.g., "quadrilateral" or "cylindrical") shall, unless otherwise specified, not only strictly represent the geometrically precise shape but also represent shapes with features such as concaves and chamfers, to a range in which an equivalent effect can be obtained.

[0024] <1. Embodiments> Figure 1 is a perspective view of a resistance measuring device 1 according to an embodiment. Figure 2 is an exploded view of the resistance measuring device 1 shown in Figure 1. Figure 3A is a cross-sectional view of the resistance measuring device 1 at the position A-A in Figure 1. Figure 3B is a cross-sectional view of the resistance measuring device 1 at the position B-B in Figure 1. Figure 3C is a cross-sectional view of the resistance measuring device 1 at the position C-C in Figure 1. Figure 4 is a bottom view of the second substrate 12 shown in Figure 1. Figure 5 is a top view of the fifth substrate 15 shown in Figure 1. In Figure 4, the first measurement chamber 10a, the upper first channel 41, and the upper second channel 43 formed in the third substrate 13 are shown by dashed lines. Also, in Figure 5, the second measurement chamber 10b, the lower first channel 45, and the lower second channel 47 formed in the fourth substrate 14 are shown by dashed lines.

[0025] The resistance measuring device 1 is an apparatus applicable to TEER measurement, which measures the electrical resistance (resistance, inductance, and impedance) of biological samples such as cells using a four-terminal method. The biological samples to be measured are not limited to cells, but include various biological samples such as biological tissues. The resistance measuring device 1 is equipped with a measurement chamber 10 inside. The measurement chamber 10 is configured as a space that can accommodate the biological sample along with a liquid for resistance measurement (physiological buffer solution, culture medium, etc.).

[0026] The resistance measuring device 1 comprises, in order from bottom to top, a first substrate 11, a second substrate 12, a third substrate 13, a fourth substrate 14, and a fifth substrate 15. The first to fifth substrates 11, 12, 13, 14, and 15 are transparent plate-like members and have a roughly rectangular shape of the same size when viewed from above. The first to fifth substrates 11, 12, 13, 14, and 15 are made of materials such as PET, polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), glass, or silicon. The second to fifth substrates 12, 13, 14, and 15 are examples of the device body. The first to fifth substrates 11 to 15 are integrated together by fasteners such as bolts or clamp members.

[0027] The resistance measuring device 1 has a membrane 20. The membrane 20 is sandwiched between the third substrate 13 and the fourth substrate 14 in the Z direction. The membrane 20 is a sheet-like member capable of holding cells. The membrane 20 has a large number of fine through-holes, allowing liquid to pass through in the thickness direction (Z direction). The membrane 20 is made of, for example, PC (polycarbonate), PTFE (polytetrafluoroethylene), PET (polyethylene terephthalate), etc. The membrane 20 is preferably translucent. The upper surface of the membrane 20 has enhanced cell adhesion properties through surface treatment such as collagen coating.

[0028] The membrane 20 has a holding region 20a that supports the biological sample. The portion of the membrane 20 corresponding to the holding region 20a divides the measurement chamber 10 into an upper first measurement chamber 10a and a lower second measurement chamber 10b. The upper surface of the holding region 20a is exposed to the upper first measurement chamber 10a in the measurement chamber 10. The membrane 20 is an example of a holding portion.

[0029] The membrane 20 is larger than the measurement chamber 10 when viewed from above, and in this example, it is the same size as the third substrate 13 and the fourth substrate 14. However, the membrane 20 may be smaller than the third substrate 13 or the fourth substrate 14 when viewed from above.

[0030] The first substrate 11 is positioned at the top of the resistance measuring device 1. The first substrate 11 has a greater thickness (dimension in the Z direction) than any of the second to fifth substrates 12, 13, 14, and 15. The first substrate 11 has an observation opening 110 that penetrates vertically. The observation opening 110 has a rectangular shape when viewed from above. The observation opening 110 overlaps with the measurement chamber 10 when viewed from above.

[0031] The lower surface of the second substrate 12 is provided with a first electrode 21, a third electrode 23, a first connection pad 25, and a second connection pad 27.

[0032] The third substrate 13 has a roughly Z-shaped first through groove 31 that penetrates in the Z direction. The upper opening of the first through groove 31 is blocked by the second substrate 12, and the lower opening is blocked by the membrane 20. This forms the first measurement chamber 10a, the upper first channel 41, and the upper second channel 43.

[0033] The upper opening of the first through groove 31 in the third substrate 13 is blocked by the second substrate 12. The lower opening of the first through groove 31 is blocked by the membrane 20 and the fourth substrate 14. This forms the first measurement chamber 10a and the upper first channel 41 and upper second channel 43 that communicate with the first measurement chamber 10a. The upper first channel 41 extends in the -X direction from the +Y side end of the first measurement chamber 10a. The upper second channel 43 extends in the +X direction from the -Y side end of the first measurement chamber 10a. The inner width (inner dimension in the Y direction) of the upper first channel 41 and upper second channel 43 is smaller than the inner width (inner dimension in the X direction) of the first measurement chamber 10a. That is, the upper first channel 41 and upper second channel 43 are narrower than the first measurement chamber 10a.

[0034] The fourth substrate 14 has a roughly Z-shaped second through groove 32. The upper opening of the second through groove 32 is blocked by the membrane 20, and the lower opening is blocked by the fifth substrate 15. This forms a second measurement chamber 10b and a lower first channel 45 and a lower second channel 47 that communicate with the second measurement chamber 10b.

[0035] In the resistance measuring device 1, the third substrate 13 and the fourth substrate 14 correspond to the first layer on which the measurement chamber 10 is formed. The second substrate 12 has the first substrate 11 formed on it and corresponds to the "second layer" that closes the upper side of the first measurement chamber 10a. Furthermore, the fifth substrate 15 corresponds to the third layer that closes the lower side of the measurement chamber 10 (specifically, the second measurement chamber 10b).

[0036] The lower first channel 45 extends in the -X direction from the -Y side end of the second measurement chamber 10b. The lower second channel 47 extends in the +X direction from the +Y side end of the second measurement chamber 10b. The inner width (inner dimension in the Y direction) of the lower first channel 45 and the lower second channel 47 is smaller than the inner width (inner dimension in the X direction) of the second measurement chamber 10b. In other words, the lower first channel 45 and the lower second channel 47 are narrower than the second measurement chamber 10b.

[0037] The upper surface of the fifth substrate 15 is provided with the second electrode 22 and the fourth electrode 24.

[0038] The first electrode 21 has a first working electrode portion 211, a first working pad portion 212, and a wiring portion that connects them electrically. "Conductivity" means that they are electrically connected. The wiring portion of the first electrode 21 is thinner than the first working electrode portion 211 and the first working pad portion 212 (Figure 4).

[0039] The first working electrode portion 211 has a substantially rectangular shape when viewed from above. The first working electrode portion 211 is located above the membrane 20. The first working electrode portion 211 is positioned to cover the entire upper side of the first measurement chamber 10a. That is, the first working electrode portion 211 covers the entire upper side of the measurement chamber 10. In both the X and Y directions, the first working electrode portion 211 is larger than the first measurement chamber 10a of the measurement chamber 10 (Figures 3A-C and 4). However, in both the X and Y directions, the first working electrode portion 211 may be the same size as the first measurement chamber 10a.

[0040] The second electrode 22 has a second working electrode portion 221, a second working pad portion 222, and a wiring portion that conducts these. The wiring portion of the second electrode 22 is thinner than the second working electrode portion 221 and the second working pad portion 222 (Figure 5).

[0041] The second working electrode portion 221 has a substantially rectangular shape when viewed from above. The second working electrode portion 221 is located below the membrane 20. The second working electrode portion 221 covers the entire lower side of the second measurement chamber 10b (Figure 5). That is, the second working electrode portion 221 is arranged to cover the entire lower side of the measurement chamber 10. In both the X and Y directions, the second working electrode portion 221 is larger than the second measurement chamber 10b in the measurement chamber 10 (Figures 3A-C and 5). However, in both the X and Y directions, the second working electrode portion 221 may be the same size as the second measurement chamber 10b.

[0042] The first working electrode part 211 and the second working electrode part 221 are arranged to face each other vertically (Figs. 3A to 3C). The first working electrode part 211 and the second working electrode part 221 have the same size and the same shape (here, a substantially rectangular shape) as each other.

[0043] The third electrode 23 includes a first reference electrode part 231, a first reference pad part 232, and a wiring part that conducts between them. The wiring part of the third electrode 23 is thinner than the first reference electrode part 231 and the first reference pad part 232 (Fig. 4).

[0044] The first reference electrode part 231 extends in the Y direction and has a substantially rectangular shape in a top view. The first reference electrode part 231 is provided above the upper first flow path 41. The first reference electrode part 231 is arranged to intersect the upper first flow path 41 that extends in the X direction in a top view (Fig. 4).

[0045] The fourth electrode 24 includes a second reference electrode part 241, a second reference pad part 242, and a wiring part that conducts between them. The wiring part of the fourth electrode 24 is thinner than the second reference electrode part 241 and the second reference pad part 242 (Fig. 5).

[0046] The second reference electrode part 241 extends in the Y direction and has a substantially rectangular shape in a top view. The second reference electrode part 241 is provided below the lower second flow path 47. The second reference electrode part 241 is arranged to intersect the lower second flow path 47 that extends in the X direction in a top view (Fig. 5).

[0047] The first electrode 21, the second electrode 22, the third electrode 23, the fourth electrode 24, the first connection pad 25, and the second connection pad 27 are formed, for example, by forming a conductive thin film by sputtering, vapor deposition, or plating using a conductive material, and patterning by photolithography or etching or the like.

[0048] The first electrode 21 is a transparent electrode. However, the portions other than the first working electrode portion 211 may be non-transparent electrodes. Note that the second electrode 22, the third electrode 23, the fourth electrode 24, the first connection pad 25, and the second connection pad 27 may be either transparent electrodes or non-transparent electrodes. Also, among the first electrode 21, the portions other than the first working electrode portion 211 may be non-transparent electrodes.

[0049] As the conductive material of the transparent electrode, for example, indium tin oxide (ITO) can be used. ITO has a very high light transmittance in the visible light region, can ensure transparency, and has high conductivity. Also, ITO is suitable for thin film formation techniques such as sputtering and evaporation, and can create a uniform thin film. Note that as the conductive material of the transparent electrode, aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), graphene or carbon nanotubes, a metal mesh, or a conductive polymer may be used. Also, as the conductive material of the non-transparent electrode, for example, gold (Au) or copper (Cu) can be used.

[0050] When the user observes the cells in the measurement chamber 10, the user can observe the cells on the membrane 20 from above the observation opening hole 11 in the first substrate 11 through the second substrate 12 and the first working electrode portion 211 of the first electrode 21. Among the second substrate 12, the transparent portion 121 that closes the opening below the observation opening hole 110 and is located above the first electrode 21 (the first working electrode portion 211) corresponds to the observation portion.

[0051] The resistance measurement device 1 has a first liquid supply hole 51, a second liquid supply hole 52, a third liquid supply hole 53, and a fourth liquid supply hole 54. The first liquid supply hole 51 and the second liquid supply hole 52 are holes that penetrate the first substrate 11 and the second substrate 12 vertically. The first liquid supply hole 51 is fluidly connected to the upper first flow path 41. The second liquid supply hole 52 is fluidly connected to the upper second flow path 43.

[0052] The third liquid delivery hole 53 and the fourth liquid delivery hole 54 are holes that penetrate vertically through the first substrate 11, the second substrate 12, the third substrate 13, and the membrane 20, respectively. The third liquid delivery hole 53 is connected to the lower first flow path 45. The fourth liquid delivery hole 54 is connected to the lower second flow path 47.

[0053] Liquids such as culture medium are supplied to the first measurement chamber 10a from the outside, for example, via the first liquid delivery port 51 and the upper first flow channel 41, and discharged to the outside via the upper second flow channel 43 and the second liquid delivery port 52. Similarly, liquids such as culture medium are supplied to the second measurement chamber 10b from the outside, for example, via the third liquid delivery port 53 and the lower first flow channel 45, and discharged to the outside via the lower second flow channel 47 and the fourth liquid delivery port 54.

[0054] The resistance measuring device 1 has a first conductive member 61 and a second conductive member 62. The first conductive member 61 and the second conductive member 62 are conductive members. The first conductive member 61 provides electrical conductivity between a second working pad portion 222 provided on the fifth substrate 15 and a first connecting pad 25 provided on the second substrate 12. The second conductive member 62 provides electrical conductivity between a second reference pad portion 242 provided on the fifth substrate 15 and a second connecting pad 27. The first conductive member 61 and the second conductive member 62 are arranged in through holes provided in the third substrate 13, the membrane 20, and the fourth substrate 14. The first conductive member 61 and the second conductive member 62 are formed using, for example, silver paste.

[0055] The resistance measuring device 1 has a first conduction hole 71, a second conduction hole 72, a third conduction hole 73, and a fourth conduction hole 74. The first to fourth conduction holes 71, 72, 73, and 74 are holes that penetrate the fifth substrate 15, the fourth substrate 14, the membrane 20, and the third substrate 13 in the Z direction, and the upper openings of each are closed by the second substrate 12. Conductive pins 9 that have conductivity can be individually inserted into the first to fourth conduction holes 71, 72, 73, and 74 from below. The conductive pins 9 are connected to external equipment such as a resistance measuring device.

[0056] At the innermost part of the first conduction hole 71 is the first working pad portion 212 of the first electrode 21 provided on the second substrate 12. When the tip of the conduction pin 9 inserted into the first conduction hole 71 contacts the first working pad portion 212, the first electrode 21 becomes electrically connected to the external device.

[0057] At the innermost part of the second conduction hole 72 is the first reference pad portion 232 of the third electrode 23 provided on the second substrate 12. When the tip of the conduction pin 9 inserted into the second conduction hole 72 contacts the first reference pad portion 232, the third electrode 23 becomes electrically connected to the external device.

[0058] The first connection pad 25, provided on the second substrate 12, is positioned at the innermost part of the third conduction hole 73. When the tip of the conduction pin 9 inserted into the third conduction hole 73 contacts the first connection pad 25, the second electrode 22 becomes electrically connected to an external device via the first connection pad 25 and the first conductive member 61.

[0059] A second connection pad 27, provided on the second substrate 12, is positioned at the innermost part of the fourth conduction hole 74. When the tip of the conduction pin 9 inserted into the fourth conduction hole 74 contacts the second connection pad 27, the fourth electrode 24 becomes electrically connected to an external device via the second connection pad 27 and the second conductive member 62.

[0060] Thus, in the resistance measuring device 1, electrical conductivity between each electrode and the outside is achieved by inserting pins into the conductivity holes provided at the bottom of the resistance measuring device 1. This prevents objects that would obstruct cell observation from being placed above the resistance measuring device 1. As a result, it becomes possible to effectively observe cells while simultaneously measuring their electrical resistance.

[0061] <Principle of Electrical Resistance Measurement> Figure 6 shows the equivalent circuit when measuring electrical resistance using a resistance measuring device. As shown in Figure 6, when measuring resistance, a power supply 91 and a voltmeter 92 are connected to the resistance measuring device 1. The output terminal of the power supply 91 is electrically connected to the contact portion of the first electrode 21 (first working pad portion 212) and the contact portion of the second electrode 22 (second working pad portion 222) via a conductor 94a. The input terminal of the voltmeter 92 is electrically connected to the contact portion of the third electrode 23 (first reference pad portion 232) and the contact portion of the fourth electrode 24 (second reference pad portion 242) via a conductor 94b.

[0062] In measuring the electrical resistance of a cell layer, monolayer-cultured cells are placed on the upper surface of the holding area 20a of the membrane 20. During measurement, a liquid for resistance measurement is introduced into the measurement chamber 10 through the first liquid delivery port 51 and the third liquid delivery port 53. The liquid is then discharged through the second liquid delivery port 52 and the fourth liquid delivery port 54. This maintains a steady flow in the first measurement chamber 10a and the second measurement chamber 10b.

[0063] In the equivalent circuit shown in Figure 6, Rm represents the sum of the electrical resistance in the holding region 20a of the membrane 20 and the electrical resistance of the cell layer formed thereon. Rw1 represents the solution resistance between the first working electrode portion 211 of the first electrode 21 and the cell layer. Rw2 represents the solution resistance between the second working electrode portion 221 of the second electrode 22 and the cell layer. Rr1 represents the solution resistance between the first reference electrode portion 231 of the third electrode 23 and the cell layer. Rr2 represents the solution resistance between the second reference electrode portion 241 of the fourth electrode 24 and the cell layer.

[0064] In the measurement, a constant current is applied between the first electrode 21 and the second electrode 22 by the power supply 91, and at the same time, the potential difference between the third electrode 23 and the fourth electrode 24 is measured by the voltmeter 92. The total resistance value is calculated from the obtained voltage value based on Ohm's law, and the pure transepithelial electrical resistance (Rm) of the cell layer is determined by further subtracting the blank value (resistance value in the absence of cells).

[0065] In the working electrode pair, the first electrode 21 and the second electrode 22, electrode polarization occurs due to an electrochemical reaction when current is applied, and the resulting formation of an electric double layer may cause the effective voltage to differ from the applied voltage. In this device, by employing potential difference measurement using the reference electrode pair, the third electrode 23 and the fourth electrode 24, this effect can be eliminated, and highly accurate resistance measurement can be achieved.

[0066] <Effects> As described above, the structure of the resistance measuring device 1 allows for improved uniformity of the electric field generated within the measurement chamber 10 by covering the entire upper part of the measurement chamber 10 with the first working electrode portion 211 of the first electrode 21. Furthermore, by making the first working electrode portion 211 of the first electrode 21 a transparent electrode, the observability of the cells held in the holding region 20a can be maintained even if the entire upper part of the holding region 20a is covered with the first working electrode portion 211. Therefore, resistance measurement accuracy and observability can be improved.

[0067] Furthermore, by covering the entire lower side of the holding area 20a within the measurement chamber 10 with the second working electrode portion 221 of the second electrode 22, the distance (shortest distance) between the first working electrode portion 211 and the second working electrode portion 221 can be made the same at any position in the X and Y directions within the measurement chamber 10. This makes it possible to generate a uniform electric field throughout the entire measurement chamber 10. As a result, the accuracy of resistance measurement can be improved.

[0068] Furthermore, by making the dimensions of the first working electrode portion 211 of the first electrode 21 larger than the dimensions of the measurement chamber 10 in the X and Y directions, the allowable range of misalignment of the first electrode 21 relative to the measurement chamber 10 during device fabrication can be increased. That is, as long as the relative misalignment between the first working electrode portion 211 and the measurement chamber 10 is within the allowable range, the first working electrode portion 211 can cover the entire holding area 20a in the measurement chamber 10. This design improves the reproducibility and reliability of measurements and improves the yield during manufacturing. Also, by making the dimensions of the second working electrode portion 221 of the second electrode 22 larger than the dimensions of the measurement chamber 10 in the X and Y directions, the allowable range of misalignment of the second electrode 22 relative to the measurement chamber 10 during device fabrication can be increased.

[0069] Furthermore, by increasing the dimensions of the first working electrode portion 211 and the second working electrode portion 221, the risk of wire breakage of the first electrode 21 and the second electrode 22 is reduced. As a result, the yield can be improved by avoiding wire breakage.

[0070] Furthermore, since the uniformity of the electric field can be increased within the first measurement chamber 10a and the second measurement chamber 10b, the degree of freedom in arranging the first reference electrode section 231 and the second reference electrode section 241, which are reference electrodes for measuring electric potential, can be improved.

[0071] In the above embodiment, the first reference electrode portion 231 is located in the upper first channel 41, but it may also be located in the upper second channel 43. Similarly, the second reference electrode portion 241 is located in the lower second channel 47, but it may also be located in the lower first channel 45.

[0072] Although this invention has been described in detail, the above description is illustrative in all respects, and the invention is not limited thereto. It is understood that countless variations not illustrated can be conceived without falling outside the scope of this invention. The components described in each of the above embodiments and variations can be combined or omitted as appropriate, as long as they do not contradict each other.

[0073] 1: Resistance measuring device 10: Measurement chamber 12: Second substrate (second layer) 13: Third substrate (first layer) 14: Fourth substrate (first layer) 15: Fifth substrate (third layer) 20: Membrane (holding part) 21: First electrode 22: Second electrode 23: Third electrode 24: Fourth electrode 41: Upper first channel (first channel) 47: Lower second channel (second channel)

Claims

1. A resistance measuring device for measuring the electrical resistance of a biological sample, comprising: a device body; a measuring chamber located inside the device body and capable of storing liquid; a holding portion located inside the measuring chamber and holding a biological sample; a transparent first electrode located away from the holding portion in one direction in a first direction and covering one side of the measuring chamber in that first direction; and a transparent observation portion located further to the first electrode in that first direction.

2. A resistance measuring device according to claim 1, wherein in a second direction intersecting the first direction, the first electrode is larger than the measuring chamber.

3. A resistance measuring device according to claim 1 or claim 2, further comprising: a second electrode located away from the holding portion on the other side in the first direction and covering the other side of the measuring chamber in the second direction.

4. A resistance measuring device according to any one of claims 1 to 3, further comprising: a flow path communicating with the measuring chamber; a third electrode positioned away from the holding portion on one side in the first direction and disposed in the flow path; and a fourth electrode positioned away from the holding portion on the other side in the first direction and disposed in the flow path.

5. A resistance measuring device according to claim 4, wherein the flow path includes a first flow path located on one side of the holding portion in the first direction, and a second flow path located on the other side of the holding portion in the first direction, the third electrode being disposed in the first flow path, and the fourth electrode being disposed in the second flow path.

6. A resistance measuring device according to any one of claims 1 to 5, wherein the first electrode is made of indium tin oxide.

7. A resistance measuring device according to any one of claims 1 to 6, comprising: a first layer on which the measuring chamber is formed; a second layer on which the first electrode is formed and which closes one side of the measuring chamber in the first direction; and a third layer which closes the lower side of the measuring chamber.

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