Dielectrophoresis device

Abstract

To make it easy to transport or sort minute materials by providing a conductance changing film having large changes of conductance.MEANS FOR SOLVING THE PROBLEM: A silicon semiconductor layer arranged between a first electrode and a second electrode includes: a first silicon layer of a first conductivity type which has first impurity concentration; a second silicon layer of a second conductivity type different from the first conductivity type which is in contact with the first silicon layer, and has second impurity concentration smaller than the first impurity concentration; and a third silicon layer of the first conductivity type which is in contact with the second silicon layer, and has third impurity concentration larger than the second impurity concentration. A first photodiode having first polarity is formed by the first silicon layer and the second silicon layer, and a second photodiode which has second polarity and is connected in series to the first photodiode is formed by the second silicon layer and the third silicon layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dielectrophoretic device. [Background technology]

[0002] Dielectrophoresis devices are known as devices capable of manipulating minute objects such as cells and microparticles in a liquid (here, "minute objects" refers to inorganic or organic objects with diameters of approximately several nm to 100 μm). Dielectrophoresis devices are devices that change the conductivity of a conductivity variable film by irradiating the film with light, and also generate the dielectrophoresis phenomenon by applying an AC voltage signal between opposing electrodes. Dielectrophoresis allows the minute objects to be moved or sorted to a desired position.

[0003] The conventional dielectrophoresis devices disclosed in Non-Patent Document 1 and Patent Document 1 use an amorphous silicon film as a conductivity-varying film whose conductivity changes with light. When exposed to light, amorphous silicon has a conductivity of 1.0 × 10 -10 S / m to 5×10 -6 S / m. On the other hand, the conductivity of solvents such as pure water is 2.0×10 -4 In this case, the conductivity ratio is about 100 times, so the voltage required for dielectrophoresis can be applied to the solvent.

[0004] However, the conductivity of buffer solutions used in cell culture, such as phosphate-buffered saline (PBS) and Dulbecco's Modified Eagle Medium (DMEM), is 1.6 S / m, which is approximately 10 times lower than the conductivity of the amorphous silicon film. 6 Because of this large difference in conductivity between the two, when an amorphous silicon film as in Patent Document 1 is used as a conductivity-changing film, it is not possible to apply a desired voltage to the solvent, making it difficult to perform dielectrophoresis.

[0005] In order to increase the range of change in the conductivity of an amorphous silicon film, Patent Document 2 discloses a dielectrophoresis device equipped with a multilayer film that constitutes a phototransistor. However, the phototransistor structure has a problem in that the circuit will not function unless the base layer is in a thin film state. A thin-film base layer has a small depletion layer region (width in the height direction) that changes the conductivity, and has poor light absorption efficiency, resulting in a small change in conductivity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2007-537729 [Patent Document 2] Special Publication No. 2016-505349 [Non-patent literature]

[0007] [Non-Patent Document 1] Shuailong et al., Small 2018, 14, 1803342, Patterned Optoelectronic Tweezers: A New Scheme for Selecting, Moving, and Storing Dielectric Particles and Cells [Non-patent document 2] Hsu et al., Lab Chip, 2010, 10, 165-172, Phototransistor-based optoelectronic tweezers for dynamic cell manipulation in cell culture media Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a dielectrophoresis device that can easily move and sort minute materials by providing a variable conductivity film that exhibits large changes in conductivity. [Means for solving the problem]

[0009] To achieve the above object, a dielectrophoresis device according to the present invention includes a solvent holding unit containing a solvent containing micro-objects to be manipulated, a first electrode disposed on a first surface of the solvent holding unit, a second electrode disposed on a second surface of the solvent holding unit, and a silicon semiconductor layer disposed between the first and second electrodes. The silicon semiconductor layer includes a first silicon layer of a first conductivity type having a first impurity concentration, a second silicon layer of a second conductivity type different from the first conductivity type and in contact with the first silicon layer and having a second impurity concentration lower than the first impurity concentration, and a third silicon layer of the first conductivity type in contact with the second silicon layer and having a third impurity concentration higher than the second impurity concentration. The first silicon layer and the second silicon layer form a first photodiode having a first polarity, and the second silicon layer and the third silicon layer form a second photodiode having a second polarity opposite to the first polarity and connected in series with the first photodiode. [Effects of the Invention]

[0010] According to the present invention, a dielectrophoretic device can be provided that can easily move and sort minute materials by providing a variable conductivity film that exhibits a large change in dielectric. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating a dielectrophoresis device according to a first embodiment. [Figure 2] FIG. 10 is a schematic diagram illustrating a dielectrophoresis device according to a second embodiment. [Figure 3] FIG. 10 is a schematic diagram illustrating a dielectrophoresis device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be designated by the same numerals. Note that the accompanying drawings show embodiments and implementation examples according to the principles of the present disclosure, but these are for understanding the present disclosure and are not to be used to interpret the present disclosure in a limiting manner. The descriptions in this specification are merely typical examples and are not intended to limit the scope or application of the present disclosure in any way.

[0013] Although the present embodiment has been described in sufficient detail to enable those skilled in the art to implement the present disclosure, it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.

[0014] [First embodiment] Next, a dielectrophoresis device 1 according to a first embodiment will be described with reference to Fig. 1. The dielectrophoresis device 1 includes, for example, an electrophoresis unit 10, an AC power supply 20, a light source 30, a CCD camera 40, and a control unit 50.

[0015] The migration section 10 is a section for separating micro-objects (e.g., cells PT) in the migration section 10 by utilizing the dielectrophoresis phenomenon. The AC power supply 20 supplies AC power to cause the dielectrophoresis phenomenon in the migration section 10. The light source 30 irradiates light to change the conductivity of the silicon layer, which is a conductivity-changing film, in the migration section 10. The CCD camera 40 is an imaging device for capturing images of the migration section 10 and determining the positions of the separated cells PT, etc. The control section 50 analyzes the images captured by the CCD camera 40 and controls the entire dielectrophoresis device 1.

[0016] The migration section 10 is composed of a solvent holding section 11, a first electrode 12, a second electrode 13, and silicon layers 14 to 16. As will be described later, the conductivity of the silicon layers 14 to 16 can be partially changed by being irradiated with light from a light source 30.

[0017] The electrophoresis unit 10 includes a solvent holding unit 11 that contains a solvent containing micro-objects PT (such as cells) to be manipulated. When the micro-objects PT are cells, the solvent holding unit 11 holds PBS (Phosphate-buffered saline) or DMEM (Dulbecco's Modified Eagle Medium) as a solvent SL (buffer solution) inside, and contains cells PT as micro-objects in the solvent SL. The cells PT can be separated and identified by moving them to a desired position in the solvent holding unit 11 using the dielectrophoresis phenomenon.

[0018] A first electrode 12 (ITO electrode) 12 is disposed on the lower surface (first surface) of the solvent holding section 11, and a second electrode 13 (P-type silicon substrate) is disposed on the upper surface (second surface) via silicon layers 14 to 16 (described later). The first electrode 12 is a transparent electrode formed from a material such as indium tin oxide (ITO). AC power is supplied between the first electrode 12 and the second electrode 13 from an AC power source 20. Light is also irradiated onto the solvent holding section 11 from a light source 30 via the first electrode 12. This changes the conductivity of the solvent SL at the light irradiation position, allowing cells PT to be separated using the dielectrophoresis phenomenon.

[0019] Between the second surface of the solvent holding portion 11 and the second electrode 13 (p-type silicon substrate), a p-type silicon layer 14 (highly doped p-type silicon layer), an n-type silicon layer 15 (lightly doped n-type silicon layer), and a p-type silicon layer 16 (highly doped p-type silicon layer) are deposited in this order from below, and these three silicon layers form a conductivity change film. The p-type silicon layers 14 and 16 have a higher impurity concentration than the n-type silicon layer 15. The n-type silicon layer 15 is in contact with the p-type silicon layer 14, forming a pn junction therebetween. The p-type silicon layer 16 is in contact with the n-type silicon layer 15 on the opposite surface, forming a pn junction therebetween.

[0020] The p-type silicon layer 14 and the n-type silicon layer 15 form a first photodiode D1, whose forward direction is from bottom to top. The p-type silicon layer 16 and the n-type silicon layer 15 form a second photodiode D2, whose forward direction is from top to bottom. The first photodiode D1 and the second photodiode D2 are connected in series (their cathodes are connected to each other) and have opposite polarities. When an AC voltage is applied between the first electrode 12 and the second electrode 13, one of the first photodiode D1 and the second photodiode D2 is in a forward bias state, and the other is in a reverse bias state.

[0021] For example, the thickness of the p-type silicon layer 14 and the p-type silicon layer 16 in the stacking direction is about 1000 to 2000 Å, and the impurity concentration is 1×10 18 cm -3 The thickness of the n-type silicon layer 15 in the stacking direction is thicker than that of the p-type silicon layers 14 and 16, for example, about 5000 Å to 1 μm, and the impurity concentration is 1×10 lower than that of the p-type silicon layers 14 and 16. 15 cm -3The width of the depletion layer in the n-type silicon layer 15 can be increased by increasing the thickness of the n-type silicon layer 15 and decreasing the impurity concentration. The increased width of the depletion layer can increase the difference in conductivity of the silicon layer between when irradiated with light from the light source 30 and when not irradiated with light, which can facilitate the occurrence of dielectrophoresis.

[0022] The operation of the dielectrophoresis device 1 of the first embodiment will be described. In dielectrophoresis, an AC voltage is applied from the AC power supply 20 to the migration section 10 via the first electrode 12 and the second electrode 13.

[0023] While a positive AC voltage is applied to the second electrode 13 (p-type silicon substrate), a voltage is applied in the forward direction of the diode to the second photodiode D2 formed by the p-type silicon layer 16 and the n-type silicon layer 15. Meanwhile, a voltage is applied in the reverse direction of the diode to the photodiode D1 formed by the n-type silicon layer 15 and the p-type silicon layer 14. The resistance of the photodiode D1 increases, and a voltage is applied to that portion, while no voltage is applied to the solvent holding portion 11. When light is irradiated from the light source 30 onto the portion where the voltage has increased, the irradiated light is absorbed by a depletion layer formed in the n-type silicon layer of the photodiode D1 to which a reverse bias is applied, generating electron-hole pairs. These electron-hole pairs cause a current to flow specifically in the irradiated portion, applying a voltage to the solvent SL. This generates a local electric field, resulting in dielectrophoresis.

[0024] Meanwhile, while a positive AC voltage is applied to the first electrode 12, a voltage is applied in the forward direction of the first photodiode D1, which is formed by the p-type silicon layer 14 and the n-type silicon layer 15. Meanwhile, a voltage is applied in the reverse direction of the diode to the photodiode D2, which is formed by the n-type silicon layer 15 and the p-type silicon layer 16. The resistance of the photodiode D2 increases, and a voltage is applied to that portion, while no voltage is applied to the solvent holding portion 11. When light is irradiated from the light source 30 onto the portion where the voltage has increased, the irradiated light is absorbed by a depletion layer formed in the n-type silicon layer 15 of the photodiode D2, which is reverse-biased, generating electron-hole pairs. These electron-hole pairs cause a current to flow specifically in the irradiated portion, applying a voltage to the solvent SL. This creates a local electric field, which can induce dielectrophoresis.

[0025] As described above, in the dielectrophoresis device 1 of the first embodiment, the silicon layers 14-16 have a P / N / P structure, forming photodiodes D1 and D2 connected in series with opposite polarity. Therefore, the conductivity of the silicon layers 14-16 is increased at the position irradiated with light from the light source 30, allowing dielectrophoresis to occur in the solvent in the increased conductivity area. With this configuration, the P / N / P structure allows the width of the depletion layer to be adjusted to a desired length, thereby enabling the electrode resistance to be adjusted to a desired value. As a result, adverse effects on the cells PT, which are the target of separation, can be reduced. Since dielectrophoresis is possible under lower applied voltage conditions and in solvents with high conductivity, the number of cell types to which dielectrophoresis technology can be applied can be increased, and the operating environment can be more flexibly configured.

[0026] [Second embodiment] Next, a dielectrophoresis device 1 according to a second embodiment will be described with reference to Fig. 2. In Fig. 2, components common to the first embodiment are given the same reference numerals as in Fig. 1, and therefore, redundant description will be omitted below. The second embodiment differs from the first embodiment in the structure of the silicon layer serving as the conductivity change film.

[0027] The silicon layer constituting the conductivity change film of the second embodiment is formed by sequentially laminating an n-type silicon layer 14A, a p-type silicon layer 15A, and an n-type silicon layer 16A. That is, the silicon layer of the dielectrophoresis device of the second embodiment has an N / P / N structure, which is different from the first embodiment.

[0028] Specifically, the n-type silicon layer 14A and the p-type silicon layer 15A form a first photodiode D3 whose forward direction is from top to bottom. The n-type silicon layer 16A and the p-type silicon layer 15A form a second photodiode D4 whose forward direction is from bottom to top. The first photodiode D3 and the second photodiode D4 are connected in series (their cathodes are connected together) and have opposite polarities.

[0029] The thickness of the n-type silicon layer 14A and the n-type silicon layer 16A in the stacking direction is about 1000 to 2000 Å, and the impurity concentration is 1×10 18 cm -3 The thickness of the p-type silicon layer 15A in the stacking direction is thicker than that of the n-type silicon layers 14A and 16A, for example, about 5000 Å to 1 μm, and the impurity concentration is 1×10 lower than that of the n-type silicon layers 14A and 16A. 15 cm -3 By increasing the thickness of the p-type silicon layer 15A and lowering the impurity concentration, a large potential difference is generated between the portion of the solvent SL in the solvent holding part 11 that is irradiated with light and the portion that is not irradiated with light, which may facilitate the occurrence of dielectrophoresis.

[0030] This configuration can achieve the same effect as the first embodiment. That is, when an AC voltage is applied between the first electrode 12 and the second electrode 13, a forward voltage is applied to one of the first photodiode D3 and the second photodiode D4, and a reverse voltage is applied to the other, causing an increase in resistance. However, when light is irradiated from the light source 30, electron-hole pairs are generated in the depletion layer in the irradiated portion, causing dielectrophoresis.

[0031] [Third embodiment] Next, a dielectrophoresis device 1 according to a third embodiment will be described with reference to Fig. 3. In Fig. 3, components common to the first embodiment are given the same reference numerals as in Fig. 1, and therefore, redundant description will be omitted below. The third embodiment differs from the first embodiment in the structure of the silicon layer serving as the conductivity change film.

[0032] In the silicon layer constituting the conductivity change film of the third embodiment, an i-type silicon layer 17 (intrinsic silicon layer) not containing impurities is formed between the p-type silicon layer 14 and the n-type silicon layer 15, and an i-type silicon layer 18 is formed between the n-type silicon layer 15 and the p-type silicon layer 16. That is, the silicon layer of the third embodiment has a P / I / N / I / P structure, which differs from the above-described embodiments. Here, "not containing impurities" and "intrinsic" do not mean limited to a silicon layer containing absolutely no impurities, but rather mean a silicon layer in which the numbers of free electrons and holes generated by thermal energy or the like are approximately equal and the number of free electrons generated from impurities is negligibly small.

[0033] The n-type silicon layer 15 contacts the p-type silicon layer 14 via the i-type silicon layer 17, forming a pin junction therebetween. The n-type silicon layer 16 contacts the p-type silicon layer 15 on the opposite surface via the i-type silicon layer 18, forming a pin junction therebetween.

[0034] The p-type silicon layer 14, the i-type silicon layer 17, and the n-type silicon layer 15 form a first photodiode D5 whose forward direction is from bottom to top. The p-type silicon layer 16, the i-type silicon layer 18, and the n-type silicon layer 15 form a second photodiode D6 whose forward direction is from top to bottom. The first photodiode D5 and the second photodiode D6 are connected in series (their cathodes are connected together) and have opposite polarities.

[0035] According to the third embodiment, substantially the same effects as those of the first embodiment can be obtained. In the third embodiment, the silicon layer includes i-type silicon layers 17 and 18, and two pin-type photodiodes D5 and D6 are formed in series with opposite polarities. This allows a depletion layer to be formed over a wide area in the photodiode to which a reverse bias is applied, facilitating the generation of electron-hole pairs when irradiated with light. Although not shown, it is also possible to adopt a silicon layer with an N / I / P / I / N structure instead of the P / I / N / I / P structure.

[0036] [others] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0037] 1...Dielectrophoresis device 10...Electrophoresis section 11...Solvent holding section 12...1st electrode 13...Second electrode 14...p-type silicon layer 14A...n-type silicon layer 15...n-type silicon layer 15A...p-type silicon layer 16...p-type silicon layer 16A...n-type silicon layer 17...i-type silicon layer 18...i-type silicon layer 20...AC power supply 30...light source 40...CCD camera 50...Control unit D1~D6...Photodiodes PT...Cell SL...solvent

Claims

1. a solvent holding section that holds a solvent containing a micro object to be manipulated; a first electrode disposed on a first surface side of the solvent holding portion; a second electrode disposed on a second surface side of the solvent holding portion; a silicon semiconductor layer disposed between the first electrode and the second electrode; Including, The silicon semiconductor layer is a first silicon layer of a first conductivity type having a first impurity concentration; a second silicon layer of a second conductivity type different from the first conductivity type, the second silicon layer being in contact with the first silicon layer and having a second impurity concentration lower than the first impurity concentration; a third silicon layer of the first conductivity type in contact with the second silicon layer and having a third impurity concentration higher than the second impurity concentration; Including, the first silicon layer and the second silicon layer form a first photodiode having a first polarity; The second silicon layer and the third silicon layer form a second photodiode having a second polarity opposite to the first polarity and connected in series with the first photodiode. A dielectrophoresis device characterized by:

2. a fourth silicon layer that is an intrinsic semiconductor layer formed between the first silicon layer and the second silicon layer; a fifth silicon layer which is an intrinsic semiconductor and is formed between the second silicon layer and the third silicon layer; The dielectrophoresis device according to claim 1 , further comprising:

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