MICROFLUID DEVICE AND MICROPARTICLE MEASURING SYSTEM

Abstract

A microfluidic device comprises a microfluidic chip. The microfluidic chip has a channel extending in one direction in its plane. The microchannel has a gate of reduced width, separating a first part and a second part. If the length of the gate is denoted as L and the width of the gate as W, then the relational expression 1 ≤ L / W < 2 is satisfied.

Description

REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Patent Application No. 2023-109531, filed on July 3, 2023, the entire contents of which are incorporated herein by reference, and claims the benefit of priority thereof. BACKGROUND 1. Technical field

[0002] The present disclosure relates to a microfluidic device. 2. Background information

[0003] A method for measuring particle size distribution, known as the electrical scanning zone method (Coulter principle), is already known. In this measurement method, an electrolyte solution containing a particle is passed through a pore called a nanopore. As the particle passes through, the electrolyte solution is present in the pore, its amount reduced by the volume of the particle, increasing the electrical resistance. The volume (or particle size) of the particle can therefore be determined by measuring the electrical resistance of the pore.

[0004] Fig. Figure 1 is a block diagram showing a microparticle measurement system 1R that employs the electrical sensing zone method. The microparticle measurement system 1R includes a pore device 100R, a measurement device 200R, and a data processor 300.

[0005] The interior of the pore device 100R is filled with an electrolyte solution 2 containing particles 4 to be detected. The interior of the pore device 100R is divided into two spaces by a pore chip 102, in which an electrode 106 and an electrode 108 are separately provided. The pore chip 102 has a pore 104 formed therein. Under the potential difference generated between the electrode 106 and the electrode 108, an ion current flows between the electrodes, and the particles 4 migrate from one space through the pore 104 into the other space, driven by electrophoresis.

[0006] The measuring device 200R generates a potential difference between a pair of electrodes 106, 108 and acquires information correlated with the resistance Rp between the electrode pair. The measuring device 200R includes a transimpedance amplifier 210, a voltage source 220, and a digitizer 230. The voltage source 220 is configured to generate a potential difference Vb between the pair of electrodes 106, 108. The potential difference Vb represents a driving force for electrophoresis and provides a bias signal for measuring the resistance Rp.

[0007] A microcurrent Is flows between the pair of electrodes 106, 108, which is inversely proportional to the resistance of the pore 104. Is=Vb / Rp

[0008] The transimpedance amplifier 210 converts the microcurrent Is into a voltage signal Vs. With the conversion gain denoted by r, the following equation applies. Vs=−r×Is

[0009] By substituting equation (1) into equation (2) we get equation (3). Vs=−Vb×r / Rp

[0010] The digitizer 230 converts the voltage signal Vs into digital data Ds. As can be seen, the measuring device 200R can obtain the voltage signal Vs, which is inversely proportional to the resistance Rp of the pore 104.

[0011] Fig. Figure 2 is an example waveform diagram of the microcurrent Is measured by the 200R meter. Note that the ordinates and abscissas of the waveform diagrams or timing charts referred to herein are enlarged or reduced accordingly for ease of understanding, and the waveforms shown here are also simplified, exaggerated, or emphasized for ease of understanding.

[0012] For a short period of time during the passage of the particles, the resistance Rp of pore 104 increases. The current Is therefore decreases in pulses each time a particle passes. The amplitude of each current pulse correlates with the particle size. The data processor 300 processes the digital data Ds and typically analyzes the number or particle size of the particles 4 contained in the electrolyte solution 2. Part of the data processor 300 can be hosted on a server or in a cloud.

[0013] The prior pore chip 102 is constructed to form an opening (pore) in a membrane, with a thickness t that is significantly smaller than the diameter (opening) d of the pore (t < d). The present applicants have investigated such a low-aspect-ratio pore device and identified the following problems.

[0014] In the low-aspect-ratio pore device, the intensity of the electric field within the pore exhibits a large position dependence in the radial direction. Therefore, different signals are observed between cases depending on whether the particle passes through the center of the pore or the outer perimeter of the pore, thereby compromising the measurement accuracy.

[0015] Related documents Patent Document 1: JP2009-014702A Patent Document 2: JP2017-120257A SUMMARY

[0016] The present disclosure has been achieved in consideration of such circumstances, so that an exemplary embodiment thereof is to provide an apparatus whose measurement accuracy can be improved.

[0017] A microfluidic device in one embodiment of the present disclosure includes a microfluidic chip. The microfluidic chip has a channel formed in one in-plane direction. The channel has a gate with a reduced width and a first part and a second part separated by the gate. With the length of the gate, denoted as L, and the width of the gate, denoted as W, the relationship 1 ≤ L / W < 2 is satisfied.

[0018] It should be noted that free combinations of these components, as well as all components and expressions exchanged between the method, the apparatus, and the system, are also considered to be the present disclosure or modes of the present disclosure. It should also be noted that the description of this section (SUMMARY OF THE INVENTION) does not describe all essential features of the present disclosure, and therefore subcombinations of these features described herein may also constitute the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Embodiments will now be described by way of example only with reference to the accompanying drawings, which are intended to be illustrative and not restrictive, and in which like elements are numbered alike in several figures, in which: Fig. 1 is a block diagram showing a microparticle measurement system using the electrical scanning zone method; Fig. 2 is an exemplary waveform diagram of the microcurrent measured by the meter; Fig. 3 is a cross-sectional view showing a prior pore chip; Fig. Figure 4 is a graph showing a histogram generated from the measurement of a standard particle using the previous pore chip; Fig. 5 is a schematic drawing explaining a cause of the histogram splitting in the prior art; Fig. 6 is a perspective view showing a microfluidic device according to the first embodiment; Fig. 7A is a plan view showing a microfluidic device; Fig. 7B is a cross-sectional view showing the microfluidic device in Fig. 7A along the line AA'; Fig. 8 is an enlarged view illustrating a gate and the surroundings of the microfluidic chip; Fig. 9 is a drawing showing a microparticle measuring system with the microfluidic device; Fig. Figure 10 is a diagram illustrating the potential at the gate and in the vicinity of the microfluidic device; Fig. 11 is a diagram illustrating an electric field at the gate and in the vicinity of the microfluidic device; Fig. 12 is a graph showing the electric field distribution of a microfluidic chip with a size of W = H = L = 3 µm; Fig. Figure 13 is a graph illustrating the electric field distribution of a microfluidic chip with dimensions W = H = 3 µm and L = 50 nm; Fig. 14 is a graph showing the dependence of the aspect ratio of the electric field strength distribution in the y-direction; Fig. 15 is a cross-sectional view showing a microfluidic device of Modified Example 1; Fig. 16 is a perspective view showing a microfluidic device according to Modified Example 2; Fig. 17A is a plan view showing the microfluidic device in Fig. 16 represents; Fig. 17B is a cross-sectional view showing the microfluidic device in Fig. 17A along the line AA'; Fig. 18 is an enlarged view showing a gate and the vicinity of a microfluidic chip according to Modified Example 3; Fig. 19 is a cross-sectional view showing a microfluidic device according to Modified Example 4; Fig. 20 is a plan view showing a microfluidic device according to the second embodiment; Fig. 21 is a plan view showing the microfluidic device in Fig. 20 shows; and Fig. 22 contains a plan view showing the microfluidic device in Fig. 21, and a cross-sectional view along the line A-A'. DETAILED DESCRIPTIONOverview of embodiments

[0020] The following outlines some exemplary embodiments of the present disclosure. This overview is intended to briefly outline some concepts of one or more embodiments to provide a basic understanding of the embodiments, as an introduction before the subsequent detailed description, without limiting the scope of the invention or disclosure. This overview is not a comprehensive overview of all possible embodiments and is therefore not intended to indicate key elements of all embodiments, nor to delimit the scope of some or all embodiments. For convenience, the term "one embodiment" may be used to refer to a single embodiment (example or modified example) or a plurality of embodiments (examples or modified examples) disclosed in the present description.

[0021] The microfluidic device according to one embodiment has a microfluidic chip. The microfluidic chip has a channel formed in one in-plane direction. The channel has a gate with a reduced width and a first part and a second part separated by the gate. If the length of the gate is denoted as L and the width of the gate as W, the relationship 1 ≤ L / W < 2 is satisfied.

[0022] This structure can generate an electric field in the gate that is essentially uniform in both the width and height directions. The structure can generate electrical signals of the same strength as each particle passes through the gate, regardless of the path, and can therefore improve measurement accuracy.

[0023] In one embodiment, the cross-sectional shape of the gate may be rectangular.

[0024] In one embodiment, the cross-section of the gate may have a width and a length that are substantially equal.

[0025] In one embodiment, the microfluidic chip can be made of polydimethylsiloxane. Polydimethylsiloxane has the advantage over other materials of being easier to process and less expensive. Alternatively, the microfluidic chip can also be made of a resin based on a cyclic olefin, such as COP (cyclic olefin polymer) or COC (cyclic olefin copolymer).

[0026] In one embodiment, the microfluidic chip may have an inlet port structured to connect the outside of the microfluidic chip to the first part and an outlet port structured to connect the outside of the microfluidic chip to the second part.

[0027] In one embodiment, the microfluidic chip may have a first inflow port structured to connect the outside of the microfluidic chip to the first part; a second inflow port structured to connect the outside of the microfluidic chip to the second part; a first outflow port structured to connect the outside of the microfluidic chip to the first part; and a second outflow port structured to connect the outside of the microfluidic chip to the second part.

[0028] The microfluidic chip may further comprise a first electrode opening structured to connect a bottom surface of the microfluidic chip to the first part; and a second electrode opening structured to connect a bottom surface of the microfluidic chip to the second part. The microfluidic device may further comprise an electrode plate on whose surface the microfluidic chip is stacked. The electrode plate may have on its surface a first electrode extended through the first electrode opening and a second electrode extended through the second electrode opening.

[0029] A microparticle measurement system according to one embodiment may comprise one of the above-mentioned microfluidic devices and a measurement device connected to the microfluidic device and configured to measure an electrical signal. Embodiments

[0030] Preferred embodiments are explained below with reference to the accompanying drawings. All similar or equivalent components, elements, and processes shown in the individual drawings are provided with the same reference numerals to avoid redundant explanations. The embodiments are for illustrative purposes only and are not limiting of the disclosure or the invention. All features and combinations thereof described in the embodiments are not always essential to the disclosure or the invention.

[0031] The dimensions (thickness, length, width, etc.) of the individual elements shown in the drawings may be enlarged or reduced accordingly for clarity. Furthermore, the dimensions of the plurality of elements do not necessarily indicate the size relationship between them, so that a particular element A shown thicker than another element B in a drawing may actually be thinner than that element B.

[0032] In the present specification, a “state in which an element A is coupled to an element B” includes a case in which the element A and the element B are physically and directly coupled, and a case in which the element A and the element B are indirectly coupled by placing another element therebetween that does not substantially affect the electrically coupled state or deteriorate the function or effect exhibited by the coupling.

[0033] Similarly, a “state where an element C is provided between the element A and the element B” includes a case where the element A and the element C or the element B and the element C are directly coupled, and a case where they are indirectly coupled while interposing another element that does not substantially affect the electrically coupled state between the elements or deteriorate the function or effect exhibited by the elements.

[0034] In this description, reference numerals attached to electrical signals such as voltage and current signals or circuit elements such as resistors, capacitors and inductors represent voltage values, current values ​​or circuit constants (resistance, capacitance and inductance) of the individual components, as appropriate.

[0035] Before describing a microfluidic device 400 according to an embodiment, a previous pore chip and its relevant problems are described.

[0036] Fig. 3 is a cross-sectional view showing a prior pore chip 800. The pore chip 800 has a membrane 810, and a pore (opening) 812 is formed in the membrane 810. In the prior pore chip 800, the membrane 810 with a thickness t of several tens of nanometers was used. This is because (i) the membrane has high crystallinity and can be manufactured in a short time by reducing the thickness t, (ii) the thin membrane is more readily available due to its lower cost and shorter delivery time, and (iii) the thin membrane is typically more processable in post-processing processes such as dry etching.

[0037] When using such a membrane 810 with a thickness t of a few tens of nanometers, a relationship between the diameter d of the pore 812 (referred to as pore diameter) and the thickness t of the membrane 810 is as follows: d > t. If the aspect ratio of the pore is defined as t / d, it is assumed that the previous pore chip 800 has a low aspect ratio.

[0038] Fig. Figure 4 is a graph showing a histogram generated from the measurement of a standard particle using a previous Pore Chip 800. The Pore Chip 800 used in the experiment has d = 3 µm and an aspect ratio of 0.017 (t = 0.050 µm). The standard particle has a diameter of 0.9 µm. The abscissa of the histogram represents the particle size, estimated from the electric current measured as the particle passes through the pore, and the ordinate represents the number of particles.

[0039] Although the histogram should ideally be unimodal, since the standard particle has a uniform diameter, the measurement results showed two split peaks, indicating strong bimodality. The bimodality of the histogram complicates particle size estimation and degrades measurement accuracy.

[0040] The present disclosure focuses on the electric field strength in the pore 812 as a possible reason for the bimodality observed when using the prior pore chip 800.

[0041] Fig. Figure 5 is a schematic diagram explaining one reason for the histogram split in the prior art. The pore chip 800 is enclosed in a housing 900. The housing 900 is divided into two chambers 902, 904 by the pore chip 800. The chambers 902, 904 are filled with the electrolyte solution 2 containing the particles 4. The particles 4 can take different paths on their way through the pore 812. Fig. Figure 5 shows two representative paths (i) and (ii). If the electric field strength in pore 812 is uniform, the measured signals have the same strength regardless of the passage path. However, if the electric field strength in pore 812 is not uniform, the measured signals would have different strengths depending on the passage path, even if the particles 4 are of uniform size. This resulted in a splitting of the histogram.

[0042] The problem of the prior art has already been described. The following sections explain a microfluidic device 400 according to embodiments that can solve the problem. First embodiment

[0043] Fig. 6 is a perspective view showing a microfluidic device 400 according to the first embodiment. Fig. 7A is a top view showing the microfluidic device 400. Fig. 7B is a cross-sectional view of the microfluidic device 400 in Fig. 7A, taken along line AA'.

[0044] In the microfluidic device 400, a microfluidic chip 410, an electrode plate 440, and a support substrate 460 are stacked. The microfluidic chip 410 has a microchannel 412 formed in the plane (in the xy plane). Although the microchannel 412 may have a size on the order of micrometers (a channel width of several to several hundred micrometers), the width at the gate may locally be in the submicron or nanometer range, as the width is designed taking into account the particles to be measured, as described later.

[0045] The microfluidic chip 410 may be made of polydimethylsiloxane. Alternatively, the microfluidic chip 410 may be made of a cyclic olefin-based resin, such as COP (cyclic olefin polymer) or COC (cyclic olefin copolymer). The method for forming the microchannel 412 may rely on any known or future available technology, without particular limitation.

[0046] The microchannel 412 extends in the x-direction, with one end connected to an inlet 424 and the other end connected to an outlet 426. The inlet 424 or the outlet 426 can be used as an inflow opening for the electrolyte solution containing the microparticles, and the other as a vent opening. The inlet 424 connects the first space 420 to the top of the microfluidic chip 410, while the outlet 426 connects the second space 422 to the top of the microfluidic chip 410.

[0047] The first electrode opening 428 connects the first space 420 to the bottom of the microfluidic chip 410. The second electrode opening 430 connects the second space 422 to the bottom of the microfluidic chip 410.

[0048] A first electrode E1 and a second electrode E2 are formed on the electrode plate 440. The first electrode E1 is drawn outward through the first electrode opening 428, while the second electrode E2 is drawn outward through the second electrode opening 430.

[0049] The first electrode E1 has a first channel-side electrode 442, a first junction 444, and a first meter-side electrode 446. The first meter-side electrode 446 is formed at a location that does not overlap the microfluidic chip 410. At the same time, the first channel-side electrode 442 is formed at a position that overlaps the first electrode opening 428 and is exposed in the first space 420. The first junction 444 connects the first channel-side electrode 442 and the first meter-side electrode 446.

[0050] Similarly, the second electrode E2 includes a second channel-side electrode 448, a second junction 450, and a second meter-side electrode 452. The second meter-side electrode 452 is formed at a location that does not overlap the microfluidic chip 410. At the same time, the second channel-side electrode 448 is formed at a position that overlaps the second electrode opening 430 and is exposed in the second space 422. The second junction 450 connects the second channel-side electrode 448 and the second meter-side electrode 452.

[0051] The first electrode E1 and the second electrode E2 are electrically connectable to a measuring device (not shown) at their first measuring device-side electrode 446 and at their second measuring device-side electrode 452, respectively.

[0052] Fig. 8 is an enlarged view showing a gate 414 and the surroundings of the microfluidic chip 410. The sidewalls S1 and S2 of the microchannel 412 protrude toward the center at a portion of the gate 414 to form partition walls 416. A portion located between the two partition walls 416 forms the gate 414 with a narrow width (length in the y-direction). At the gate 414, the microchannel 412 is divided into the first space 420 and the second space 422. The gate 414 is also referred to as a narrowed portion. In this embodiment, the gate 414 has a rectangular cross-section defined by the width W and the height H.

[0053] If the length of the gate 414 is denoted by L, the relationship 1 ≤ L / W < 2 is satisfied. Similarly, the relationship 1 ≤ L / H < 2 is satisfied. The width W and the height H can be substantially the same or different. The ratio L / W is called the aspect ratio.

[0054] The structure of the microfluidic device 400 has already been explained. Next, the measurement of microparticles using the microfluidic device 400 will be described.

[0055] Fig. Figure 9 is a diagram showing a microparticle measurement system 1 with a microfluidic device 400. The microparticle measurement system 1 includes a measurement device 200, a data processor 300, and a microfluidic device 400.

[0056] The 200 measuring device is similar to the 200R measuring device in Fig. 1 and includes the voltage source 220, the transimpedance amplifier 210, and the digitizer 230. The voltage source 220 applies a bias voltage Vb between the first electrode E1 and the second electrode E2 of the microfluidic device 400. The interior of the microchannel 412 of the microfluidic chip 410 is filled with an electrolyte solution containing the microparticles 2. When the bias voltage Vb is applied, the current Is flows from the first electrode E1 to the second electrode E2. The transimpedance amplifier 210 converts the current Is into a voltage signal Vs. The digitizer 230 converts the voltage signal Vs into digital data Ds.

[0057] The current Is flowing from the first electrode E1 to the second electrode E2 is inversely proportional to the impedance Z between the first electrode E1 and the second electrode E2. The microparticles 2 are positively or negatively charged and migrate, driven by an electric field (electrophoresis) generated between the first electrode E1 and the second electrode E2. When the microparticles 2 pass through the gate 414, the impedance Z between the first electrode E1 and the second electrode E2 increases, and the current Is decreases.

[0058] That is, in the microfluidic device 400, the gate 414 acts as pore 104 in the former pore device 100R.

[0059] To verify the superiority of the microfluidic device 400, the results of an electromagnetic field simulation are described.

[0060] Fig. Figure 10 is a graph showing the potential at gate 414 and the surroundings of the microfluidic device 400. In the simulation, the dimensions of gate 414 were specified as W = H = L = 3 µm.

[0061] Fig. 11 is a diagram showing an electric field at the gate 414 and in the vicinity of the microfluidic device 400.

[0062] Fig. Figure 12 is a graph showing the electric field distribution of a microfluidic chip 410 with a size of W = H = L = 3 µm. The abscissa represents the position in the longitudinal direction (x-axis) of the microchannel 412, where x = 0 represents the center of the gate 414. The ordinate represents the position in the width direction (y-axis) of the microchannel 412, where y = 0 represents the center of the gate 414. The gradation corresponds to the strength of the electric field, and the arrows indicate the direction of the electric field.

[0063] In the device with the aspect ratio given by L / W = 1, the electric field vectors inside the gate 414 appear parallel with no component in the y-axis direction, indicating a uniform distribution of the electric field.

[0064] For comparison, the same simulation was performed with the length L of gate 414 set to 50 nm.

[0065] Fig. Figure 13 is a graph showing the electric field distribution of a microfluidic chip 410 with dimensions W = H = 3 µm and L = 50 nm. At L = 50 nm, the aspect ratio L / W is 0.017, which does not satisfy the relationship 1 ≤ L / W < 2. The electric field vectors in this case have components in the y-axis direction at the end of the gate 414, causing the electric field distribution to become uneven.

[0066] Fig. Figure 14 is a graph showing the dependence of the aspect ratio on the electric field intensity distribution in the y-direction. The abscissa represents the position in the width direction (y-axis), and the ordinate represents the electric field intensity. At lower aspect ratios L / W, the electric field intensity increases as the position is further from the center or closer to the sidewall. This means that, unfortunately, in the device with a low aspect ratio, the electric field is concentrated at the end of the gate 414. In contrast, a uniform electric field intensity distribution can be achieved in a region with an aspect ratio L / W of 1 or more.

[0067] When the aspect ratio L / W is set to 1 or more, this embodiment can achieve a uniform distribution of the electric field at the gate 414. The same signal strength level is achieved regardless of the particle passage path. This results in a highly unimodal histogram while preventing histogram splitting. This successfully improves the detection accuracy of particle size or particle type.

[0068] If the aspect ratio L / W is increased or the length L of the gate 414 is extended, the gate 414 is more likely to become clogged and have a plurality of particles in it at the same time, which deteriorates the measurement accuracy of the particle size distribution. Now, let φ be the diameter of the particle, and when L < 2 × φ, the number of particles that can be in the gate 414 at the same time is considered to be 1. Now, the diameter φ of the particle that can pass through the gate 414 is limited by the width W of the gate 414, with a relationship of φ < W. Therefore, when L < 2 × W, that is, L / W < 2, the probability that multiple particles are in the gate 414 at the same time can be reduced, thereby improving the measurement accuracy.Similarly, since φ < H, the probability that multiple particles can be in the gate 414 at the same time can be reduced if a relationship L < 2×H, ie, L / H < 2, holds, whereby the measurement accuracy can be improved.

[0069] Next, a modification of the microfluidic device 400 of the first embodiment will be explained.

[0070] Fig. 15 is a cross-sectional view showing a microfluidic device 400A of Modified Example 1. In this modified example, the height of the first space 420 and the second space 422 gradually decreases toward the gate 414. This makes it easier for the first space 420 and the second space 422 to be filled with the electrolyte solution containing the particles. Also, the particles can more easily reach the gate 414 during measurement.

[0071] Fig. 16 is a perspective view showing a microfluidic device 400B of Modified Example 2. Fig. 17A is a plan view showing the microfluidic device 400B in Fig. 16 shows. Fig. 17B is a cross-sectional view of the microfluidic device 400B in Fig. 17A, along line A-A'. In this modified example, the first electrode opening 428 is provided at the same position as the inlet 424 and the second electrode opening 430 is provided at the same position as the outlet 426.

[0072] The height of the first room 420 and the second room 422 decreases continuously and gradually towards the gate 414.

[0073] Fig. Fig. 18 is an enlarged view showing the gate 414 and the surroundings of a microfluidic chip 410C of modified example 3. In this modification, the shape of the partition walls 416C is different from that of the partition walls 416 in Fig. 8. In particular, the partition walls 416C are shaped to continuously narrow the width of the first space 420 and the second space 422 toward the gate 414.

[0074] Fig. 19 is a cross-sectional view showing a microfluidic device 400D of Modified Example 4. The microfluidic device 400D lacks the electrode plate 440. The microfluidic chip 410D also lacks the first electrode opening 428 and the second electrode opening 430. The inlet 424 and the outlet 426 are structured to accommodate the rod-shaped first electrode E1 and the second electrode E2 inserted therein. In the microfluidic device 400 described in the first embodiment, when the width W (and / or height H) of the gate 414 is up to a few micrometers (e.g., 3 μm), the first space 420, the gate 414, and the second space 422 can be filled with the liquid by injection through the inlet 424. However, the liquid injected through the inlet 424 is less likely to enter the gate 414 with a width W of less than 3 µm.

[0075] The following sections describe the second embodiment of a microfluidic device with a small cross-sectional area of ​​the gate 414, which is suitable for the detection of other smaller microparticles. Second embodiment

[0076] Fig. 20 is a plan view showing a microfluidic device 400E of the second embodiment. In the second embodiment, a first space 420E and a second space 422E each have a U-shape. The first space 420E and the second space 422E may alternatively have a V-shape, a J-shape, or a horseshoe shape, without particular limitation.

[0077] On the side of the first chamber 420E are a first inlet 431 and a first outlet 432. The first inlet 431 connects one end of the first chamber 420E to the top of the microfluidic chip 410E. The first outlet 432 connects the other end of the first chamber 420E to the top of the microfluidic chip 410E.

[0078] Similarly, a second inlet 433 and a second outlet 434 are provided on the side of the second space 422E. The second inlet 433 connects one end of the second space 422E to the top of the microfluidic chip 410E. The second outlet 434 connects the other end of the second space 422E to the top of the microfluidic chip 410E.

[0079] The first room 420E and the second room 422E are connected to each other, with a gate 414E in between.

[0080] Fig. 21 is a plan view showing the microfluidic device 400E in Fig. 20 shows.

[0081] Before measurement, the liquid is injected through the first inlet 431 into the first space 420E to fill its interior from the first inlet 431 to the first outlet 432. Similarly, the liquid is injected through the second inlet 433 into the second space 422E to fill its interior from the second inlet 433 toward the second outlet 434. When the liquid in the first space 420E and the second space 422E reaches the gate 414E, the gate 414E is also filled with the liquid by capillary action.

[0082] Also in the second embodiment, the internal heights of the first space 420E and the second space 422E may be gradually stepped.

[0083] Fig. 22 includes a plan view illustrating the microfluidic device 400E in Fig.21, and a cross-sectional view taken along line AA'. The height of the first space 420E and the second space 422E is higher at the inner periphery of the U-shape and becomes lower toward the outer periphery, i.e., toward the gate 414E. The first space 420E and the second space 422E are, for example, 1 mm wide, with the depth being graded in three steps of 200 µm, 50 µm, and 20 µm. The gate 414E is approximately 3 µm high.

[0084] The modification described in the first embodiment can also be applied to the second embodiment. For example, in the second embodiment, the first electrode opening 428 and the second electrode opening 430 may be omitted, and instead, the rod-shaped first electrode E1 and the second electrode E2 may be inserted into the first inlet 431 and the second inlet 433, respectively.

[0085] After describing the present disclosure using specific terms relating to the embodiments, the embodiments merely illustrate the principle and applications of the present disclosure, allowing a variety of modifications and layout changes without departing from the spirit of the present disclosure defined by the claims. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2023-109531

[0001] JP 2009-014702A

[0015] JP 2017-120257A

[0015]

Claims

[1] A microfluidic device comprising a microfluidic chip, the microfluidic chip having a channel formed in one direction in the plane thereof, the channel having a gate with a reduced width and a first part and a second part separated by the gate, and a length of the gate is denoted as L and a width of the gate is denoted as W, satisfying a relational expression 1 ≤ L / W < 2. [2] The microfluidic device according to claim 1, wherein a cross section of the gate has a rectangular shape. [3] The microfluidic device of claim 2, wherein the cross-section of the gate has a width and a length that are substantially equal. [4] A microfluidic device according to any one of claims 1 to 3, wherein the microfluidic chip is formed from polydimethylsiloxane. [5] Microfluidic device according to one of claims 1 to 3, wherein the microfluidic chip comprises: - an inlet opening structured to connect the outside of the microfluidic chip to the first part; and - an outflow opening structured to connect the outside of the microfluidic chip to the second part. [6] Microfluidic device according to one of claims 1 to 3, wherein the microfluidic chip comprises: - a first inlet opening structured to connect the outside of the microfluidic chip to the first part; - a second inlet opening structured to connect the outside of the microfluidic chip to the second part; - a first outflow opening structured to connect the outside of the microfluidic chip to the first part; and - a second outlet opening structured to connect the outside of the microfluidic chip to the second part. [7] A microfluidic device according to any one of claims 1 to 3, wherein the microfluidic chip further comprises: - a first electrode opening structured to connect a bottom surface of the microfluidic chip to the first part; and - a second electrode opening structured to connect a bottom side of the microfluidic chip to the second part, - the microfluidic device further comprises an electrode plate on the surface of which the microfluidic chip is stacked, and - the electrode plate has on its surface a first electrode which is drawn out through the first electrode opening and a second electrode which is drawn out through the second electrode opening. [8] Microparticle measurement system comprising: - the microfluidic device according to any one of claims 1 to 3; and - a measuring device connected to the microfluidic device and designed to measure an electrical signal.

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