WO2014167858A1 - Solvent control method and solvent for electrowetting - Google Patents

Abstract

A solvent control method for controlling the position of a solvent using a solvent control device relating to an embodiment of the present invention, said solvent control device comprising a substrate, multiple electrodes that are disposed on the substrate, a dielectric that is disposed so as to cover the substrate and electrodes, and a water-repellent film that is disposed on the dielectric and has water repellency, wherein the position of a solvent on the water-repellent film is controlled by applying a voltage to the electrodes, and said solvent contains at least one member selected from the group consisting of formamide, ethylene glycol monoethyl ether and tetrabromoethane and has a polarity force component of 3.1-28.8 mN/m inclusive.

Description

Solvent control method and solvent for electrowetting

The present application relates to a solvent control method and a solvent for electrowetting.

[0005] Droplet movement control using “electrowetting (EW)” is known. EW is a technique for controlling the wetting of droplets on a solid surface by applying a voltage.

An example of a control device using EW includes a substrate, a plurality of electrodes disposed on the substrate, and a water repellent film disposed on the plurality of electrodes. A droplet is dropped on the water repellent film, the application of a voltage to each electrode is controlled, and the droplet is moved to move the position of the droplet.

For example, Patent Document 1 discloses that the polar force component of the water repellent coating layer is one of the factors that determine the force acting on the interface between water and the water repellent material.

Patent Documents 2 and 3 disclose various organic solvents and ionic liquids as polar solvents used for electrowetting other than water. Further, it is disclosed that the polar solvent is selected based on the viscosity, the surface tension of the droplet, the conductivity, and the like.

Japanese Patent No. 4370687 Special table 2012-520485 gazette Special table 2013-501259 gazette

In the conventional technology, there has been a demand for a solvent and a control method that can move droplets more reliably by EW. The non-limiting exemplary form of the present application provides a solvent that can move the droplets more reliably and a solvent control method that controls the position of the solvent.

A solvent control method for controlling a position of a solvent using a solvent control device according to an aspect of the present invention, wherein the solvent control device includes a substrate, a plurality of electrodes disposed on the substrate, and the substrate And a dielectric disposed so as to cover the plurality of electrodes, and a water repellent film disposed on the dielectric and having water repellency, and applying a voltage to the plurality of electrodes The position of the solvent on the water-repellent film is controlled, and the solvent contains at least one of amide, glycol, glycerin, amino alcohol, hydroxyamine, polyhydric alcohol, and 3.1 mN / m or more It has a polar force component of 28.8 mN / m or less.

According to the solvent control method according to the present disclosure, it is possible to move droplets more reliably by EW.

It is the figure which looked at an example of the solvent control apparatus 100 from the upper surface. It is the figure which looked at an example of solvent control device 100 from the side. 5 is a diagram illustrating an example of a method for controlling the position of a solvent 203. FIG. 5 is a diagram illustrating an example of a method for controlling the position of a solvent 203. FIG. 5 is a diagram illustrating an example of a method for controlling the position of a solvent 203. FIG. 5 is a diagram illustrating an example of a method for controlling the position of a solvent 203. FIG. It is a figure which shows the relationship between the polar force component of a solvent, and the minimum drive voltage.

Prior to describing the embodiments, the knowledge on which the present invention is based will be described.

The inventors of the present application studied in detail an apparatus or method for controlling the position of a solvent by conventional EW. As a result, for example, depending on the type of the solvent, the solvent can be moved immediately after the solvent is placed in the control device using the EW. However, after the solvent has been placed, the solvent can be moved. It has been found that there are cases where it is not possible to move.

Conventionally, the performance of the water-repellent film of the control device using EW is often evaluated by the contact angle. However, it has been found that among the water-repellent films having the same contact angle, there are a water-repellent film that can move the solvent and a water-repellent film that cannot move the solvent.

The inventors of the present application examined in detail the conditions under which the solvent can be moved by EW from such a viewpoint. As a result, it has been found that the polar force component of the solvent particularly affects whether or not the solvent can be operated according to the time after the solvent is dropped.

Furthermore, the present inventors have not only found out whether or not the solvent operates depending on the polar force component of the water-repellent film, the material of the solvent, and the volume of the solvent, as well as the polar force component of the solvent. Got. Specific contents will be described with reference to embodiments and examples.

The outline of one embodiment of the present invention is as follows.

A solvent control method according to an aspect of the present invention is a solvent control method for controlling the position of a solvent using a solvent control device, and the solvent control device includes a substrate and a plurality of substrates disposed on the substrate. An electrode, a dielectric disposed so as to cover the substrate and the plurality of electrodes, and a water-repellent film disposed on the dielectric and having water repellency, the voltage applied to the plurality of electrodes Is applied to control the position of the solvent on the water-repellent film, and the solvent contains at least one selected from the group consisting of formamide, ethylene glycol monoethyl ether, and tetrabromoethane, and It has a polar force component of 3.1 mN / m or more and 28.8 mN / m or less.

The solvent may contain at least two selected from the group consisting of formamide, ethylene glycol monoethyl ether and water.

The solvent may have a polar force component of 3.1 mN / m or more and 22.0 mN / m or less.

The solvent may have a volume of 3 μL or more and 10 μL or less.

The water repellent film may have a polar force component of 0.2 mN / m or more and 0.3 mN / m or less.

The water repellent film may be made of an amorphous fluororesin.

The electrowetting solvent according to one embodiment of the present invention includes at least two selected from the group consisting of amide, glycol, glycerin, amino alcohol, hydroxyamine, polyhydric alcohol, halogenated hydrocarbon, and water, and It has a polar force component of 3.1 mN / m or more and 28.8 mN / m or less.

The electrowetting solvent may contain at least two selected from formamide, ethylene glycol monoethyl ether, tetrabromoethane, and water.

The electrowetting solvent may contain at least two selected from formamide, ethylene glycol monoethyl ether and water.

The electrowetting solvent may have a polar force component of 3.1 mN / m or more and 22.0 mN / m or less.

(Embodiment)
Hereinafter, embodiments will be described with reference to the drawings.

“Electrowetting (EW)” means a phenomenon in which wetting of a droplet changes or a method of controlling the wettability of the droplet by applying a voltage to a droplet having polarity.

FIG. 1 shows a view of an example of the solvent control device 100 of the present embodiment as viewed from above. FIG. 2 shows a side sectional view of an example of the solvent control device 100.

1 and 2 includes a substrate 204, a plurality of electrodes 201 arranged on the substrate 204, a dielectric 205 provided on the substrate 204 so as to cover the electrodes 201, and a dielectric 205. And a water repellent film 206 provided thereon. In FIG. 1, the dielectric 205 and the water repellent film 206 are omitted. Actually, the dielectric 205 and the water repellent film 206 are disposed on at least the plurality of electrodes 201.

The solvent control apparatus 100 applies a voltage to the plurality of electrodes 201, thereby applying a voltage to the solvent 203 disposed on the electrode 201 via the water repellent film 206, thereby changing the wettability of the solvent 203. The position of 203 is controlled. Each configuration will be described below.

<Substrate 204>
A known insulating material is used for the substrate 204. Examples of the insulating material include glass and sapphire.

As the substrate 204, a substrate in which an insulating material such as SiO ₂ , Al ₂ O ₃ , or a polymer material is coated on a conductive material or a semiconductor material containing silicon or metal may be used.

<Electrode 201>
The plurality of electrodes 201 are disposed inside a dielectric 205 described later. Alternatively, the plurality of electrodes 201 are disposed on the substrate 204 and are disposed so that the dielectric 205 covers the top.

As shown in FIG. 2, each of the plurality of electrodes 201 is disposed at a position separated from each other. The distance between two adjacent electrodes 201 is smaller than the width of the electrode 201. An example of the distance between the two electrodes 201 is desirably 1 mm or less. As shown in FIG. 1, each of the plurality of electrodes 201 is also referred to as an electrode 201a, an electrode 201b, an electrode 201c, an electrode 201d, and an electrode 201e. The electrode 201a, the electrode 201b, the electrode 201c, the electrode 201d, and the electrode 201e are also collectively referred to as the electrode 201.

A voltage is applied to the plurality of electrodes 201. As shown in FIGS. 1 and 2, for example, an electrode wiring 202 is electrically connected to each of the plurality of electrodes 201. For example, the electrode wiring 202a, the electrode wiring 202b, the electrode wiring 202c, the electrode wiring 202d, and the electrode wiring 202e are electrically connected to the electrode 201a, the electrode 201b, the electrode 201c, the electrode 201d, and the electrode 201e, respectively.

The power source (voltage application unit) 207 controls the position of the solvent 203 by applying a voltage to at least one of the plurality of electrodes 201 via the electrode wiring 202. Details will be described later.

The electrode 201 can be a known material having electrical conductivity. An example of the material of the electrode 201 is at least one metal selected from Au, Pt, Cu, Al, and Ag.

In addition, by using the solvent control device 100 for a display device or the like, a transparent conductive material containing ITO (Indium Tin Oxide) or ZnO is used as the electrode 201 when an electrode having optical transparency is required. desirable.

Further, by using Cr or Ti as the material of the electrode 201, the adhesion between the electrode 201 and the substrate 204 or the dielectric 205 can be improved.

The electrode 201 can be formed by using a known film formation method such as an evaporation method or a sputtering method.

The electrode 201 desirably has a thickness of 0.01 μm or more and 2 μm or less.

For example, when the electrode 201 having a thickness larger than 2 μm is formed on the substrate 204, the height of the region where the electrode 201 is formed and the height of the region where the electrode 201 is not formed on the surface of the substrate 204. There is a big difference. As a result, when the dielectric 205 and the water repellent film 206 are formed, regions having different heights may be formed in the dielectric 205 and the water repellent film 206. May have an impact.

The electrode 201 having a thickness smaller than 0.01 μm has high electric resistance, and the electric resistance of the electrode 201 and the electrode wiring 202 is high. That is, since the electric resistance of the portion to which the voltage is applied (the electrode 201 and the electrode wiring 202) is increased, the voltage applied from the voltage applying unit 207 is lost, so that it is difficult to apply a desired voltage to the electrode 201. .

<Dielectric 205>
The dielectric 205 is disposed on the electrode 201. The dielectric 205 may also be disposed on the substrate 204. As the dielectric 205, a known insulating material can be used. An example of the dielectric 205 is an insulating material such as a polymer compound, various oxides of an inorganic compound, a composite oxide, or a nitride.

When a voltage is applied to the electrode 201, the dielectric 205 desirably has a large capacitance. Therefore, the dielectric 205 can be a dielectric material capable of forming a film having a thickness of 1 μm or less, or a material having a high relative dielectric constant.

When the dielectric 205 is made of a polymer compound, the dielectric 205 can be formed using a known method such as a dipping method, a spray coating method, or a spin coating method. In the case where the dielectric 205 is made of an inorganic compound, the dielectric 205 can be formed using a known method such as a sputtering method, a spray coating method, or a spin coating method.

In order to prevent peeling between the dielectric 205 and the water repellent film 206, the surface of the dielectric 205 may be coated with a silane coupling agent or may be subjected to a surface treatment. The silane coupling agent forms a covalent bond between the material constituting the water repellent film 206 and the material constituting the dielectric 205. Examples of the silane coupling agent are propyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, octyltrichlorosilane, and decyltrichlorosilane. A silane coupling agent having a fluoroalkyl chain may be used.

<Water repellent film 206>
The water repellent film 206 is disposed on the dielectric 205. An example of the material of the water repellent film is a compound having a fluoroalkyl chain such as polytetrafluoroethylene (PTFE), Cytop (registered trademark) (manufactured by Asahi Glass), or AF1600 (manufactured by DuPont). That is, the material of the water repellent film is an amorphous fluororesin. Of these water-repellent film materials, those having a silane coupling agent in the molecule can be preferably used since high adhesion to the dielectric 205 can be obtained. The above-described silane coupling agent having a fluoroalkyl group may be used as the water repellent film 206.

Generally, the water repellent film 206 has a high water repellency by having a fluoroalkyl chain. As will be described below, according to detailed examinations by the inventors of the present application, it has been found that an amorphous fluororesin having a polar force component of 0.2 mN / m or more and 0.3 mN / m or less is easily moved by EW. .

Further, since the water repellent film 206 operates the solvent on the surface thereof, it is desirable that the water repellent film 206 has a weak adhesion to the solvent. As a more specific example, the sliding angle is 30 ° or less with respect to the solvent 203.

<Solvent 203>
An example of the solvent 203 is a material including at least one selected from amide, glycol, glycerin, amino alcohol, hydroxyamine, polyhydric alcohol, and halogenated hydrocarbon.

Specific examples of the solvent 203 include at least one selected from formamide, ethylene glycol monoethyl ether, and tetrabromoethane.

As a result of the study by the inventors of the present application, a solvent having a polar force component of 3.1 mN / m or more and 28.8 mN / m or less is easily moved by EW. It was also found that the solvent can be moved over time.

Therefore, an example of the desirable solvent 203 includes at least one selected from formamide and ethylene glycol monoethyl ether, and the polar force component is 3.1 mN / m or more and 28.8 mN / m or less.

More preferable examples of the solvent 203 include at least one selected from formamide and ethylene glycol monoethyl ether, and have a polar force component of 3.1 mN / m or more and 22.0 mN / m or less.

In the embodiment, the specific contents described above will be described in detail.

Formamide can be used particularly preferably because it has a polar force component higher than a predetermined value and a high boiling point, so that the droplet operation by electrowetting occurs stably.

In addition, ethylene glycol monoethyl ether has a polar force component of a predetermined value or more and has a low melting point and a high boiling point, so that it can be preferably used in a droplet operation by electrowetting that requires a low temperature operation.

Generally, solvent transfer technology using EW is used in an environment such as a biochip or outdoors. Further, depending on the purpose of use or the usage environment, the solvent 203 dissolves various solutes, and the dissolved solute and the solvent 203 are mixed and used. Therefore, the solvent 203 may be a single material selected from amide, glycol, glycerin, aminoalcohol, hydroxyamine, and polyhydric alcohol. However, the solute to be dissolved (solute for physiological saline, test) Reagents, inks (colorants), solvent specific gravity control for transport, etc.) and various countermeasures for use environments (reliability represented by temperature, humidity, and light resistance) The composition of 203 may be adjusted.

Formamide and ethylene glycol monoethyl ether can be mixed with various solvents in various compositions, and can be particularly preferably used when the solvent 203 is used as a mixed solvent. For example, a human body or a body fluid sample such as blood used in a biochip is often collected from a human body using alcohol as a solvent in consideration of minimal invasiveness. However, the alcohols have problems such as not operating as the solvent 203 and rapid evaporation as will be described later, and the specimen cannot be used as it is. In contrast, formamide and ethylene glycol monoethyl ether can be mixed with alcohols in various compositions, and are useful as a mixed solvent for the solvent 203 in terms of controlling polar force components and suppressing evaporation.

Tetrabromoethane has a very large specific gravity of 2.97 g / mL, whereas the specific gravity of a common solvent is 0.7-1.2 g / mL. It is useful as a mixed solvent for EW. Fluorocarbon hydrogen, chlorohydrocarbon and iodinated hydrocarbon other than tetrabromoethane can also be used as a solvent having a large specific gravity in the solvent 203.

According to the study by the inventors of the present application, even when two or more solvents are mixed or the solute is dissolved in the solvent, if the polar force component of the solvent is within the range described above by EW, EW It was found that it was easy to move. It was also found that the solvent can be moved over time. For this reason, according to a use, the solvent for EW which can melt | dissolve a solute and can be easily moved by EW can be provided. In other words, even if it is difficult to achieve both solute solubility and movement by EW with a single solvent, solute dissolution can be achieved by mixing two or more solvents so that the solute can be used with the polar force component as an index. Therefore, it is possible to realize a solvent that can achieve both compatibility and movement by EW. Specifically, for example, the polar force component of the solvent after mixing at least two selected from the group consisting of amide, glycol, glycerin, amino alcohol, hydroxyamine, polyhydric alcohol, halogenated hydrocarbon and water is 3 What is necessary is just to mix in the ratio which will be set to 0.1 mN / m or more and 28.8 mN / m or less. More specifically, the solvent for EW may contain at least 2 selected from formamide, ethylene glycol monoethyl ether, tetrabromoethane, and water.

<Solvent control method>
Next, a droplet control method in the solvent control apparatus 100 will be described with reference to FIGS. 3A to 3D.

3A to 3D omit the dielectric 205 and the water-repellent film 206 as in FIG. 1, but actually the dielectric 205 and the water-repellent film 206 are disposed on the electrode 201. FIG.

<FIG. 3A>
As shown in FIG. 3A, a solvent 203 is disposed on the water repellent film 206. The solvent 203 is located on the at least two electrodes 201. In FIG. 3A, the solvent 203 is located on the electrode 201a and the electrode 201b.

<FIG. 3B>
A voltage is applied so that a voltage is applied only to the electrode 201b from the state of FIG. 3A. For example, when the electrode 201b is electrically connected to the electrode wiring 202b and the voltage application unit 207 (not shown), a voltage is applied to the electrode 201b by the power source 207 via the electrode wiring 202b. For example, the electrodes 201a, 201c to 201e other than the electrode 201b are grounded. A portion of the solvent 203 located on the electrode 201b has a small contact angle due to a change in wettability, and a contact area with the water repellent film 206 is increased. As a result, the solvent 203 moves from the current position toward the upper side of the electrode 201b.

Specifically, as shown in FIG. 3B, the solvent 203 moves in the direction of arrow A.

<FIG. 3C>
A voltage is applied so that a voltage is applied only to the electrode 201c from the state of FIG. 3B. For example, the electrodes 201a, 201b, 201d, and 201e other than the electrode 201c are grounded. As a result, the solvent 203 moves in the direction of arrow A as shown in FIG. 3C.

Note that a voltage may be applied to the electrode 201b and the electrode 201c. By applying a voltage only to the electrode 201c after applying a voltage to both the electrode 201b and the electrode 201c, the solvent 203 can be moved above the electrode 201c as shown in FIG. 3C.

<FIG. 3D>
A voltage is applied so that a voltage is applied only to the electrode 201c from the state of FIG. 3C. As a result, as shown in FIG. 3D, the solvent 203 moves in the direction of arrow A.

As described above, when a voltage is applied to the electrode 201 in which at least a part of the solvent 203 is located above, the wettability of the solvent 203 located above the electrode 201 changes. As a result, the position of the solvent 203 moves on the water repellent film 206.

The position of the solvent 203 can be moved (controlled) not only in the direction of the arrow A shown in FIGS. 3A to 3D but also in the direction opposite to the arrow A by controlling the position of the electrode with the voltage.

Hereinafter, the present disclosure will be described in more detail by way of examples.

(Example 1)
A glass substrate was prepared as the substrate 204.

On the substrate 204, an electrode 201 and an electrode wiring 202 made of chromium and gold were formed by photolithography.

Specifically, chromium and gold were deposited on the entire top surface of the substrate 204. A resist was applied to the upper surface of chrome and gold. After applying the resist, exposure was performed using a photomask. After exposure, the resist was removed and etched to form chromium and gold in desired shapes.

As shown in FIG. 1, the shape of the electrode 201 and the electrode wiring 202 was formed. The electrode 201 was 0.5 mm in the width direction and 3 mm in the vertical direction. Here, the width direction is the left-right direction shown in FIG. 1, and is the direction in which the solvent 203 described later moves. The vertical direction is a direction perpendicular to the width direction. Forty electrodes 201 were formed to be aligned in the width direction. The space between the electrodes 201 was 50 μm. Forty electrodes 201 had a length of 41 mm in the width direction.

As the dielectric 205, SiO ₂ having a thickness of 150 nm was formed on the substrate 204, the electrode 201 and the electrode wiring 202 made of chromium and gold by sputtering.

As the water repellent film 206, an amorphous fluorinated polymer thin film (CYTOP (registered trademark) manufactured by Asahi Glass Co., Ltd.) was formed on SiO ₂ using a spin coating method. The film thickness of the water repellent film 206 was about 2 μm.

As the solvent 203, formamide was used. The amount of the solvent 203 was three types: 3 μL, 5 μL, and 10 μL.

After formamide was dropped onto the water-repellent film 206, a voltage of 150 V was applied to the electrode 201 via the electrode wiring 202, and an experiment was conducted as to whether or not the solvent 203 moved.

Simultaneously when formamide was dropped on the water-repellent film 206, application of a voltage to the electrode 201 and switching of the electrode 201 to which the voltage was applied (hereinafter also referred to as switching of voltage application) were started. The voltage application to each electrode 201 was switched every 0.1 second. The voltage is applied from end to end of the 40 electrodes 201 in 4 seconds, and the direction of voltage application is reversed every 4 seconds, and the solvent 203 reciprocates left and right every 4 seconds. Condition. An experiment was conducted as to whether or not formamide operates immediately after the addition of the solvent 203, 5 minutes after the addition, and 10 minutes after the addition.

(Example 2)
The experiment was performed in the same manner as in Example 1 except that ethylene glycol monoethyl ether was used as the solvent 203. Table 1 shows the experimental results.

(Example 3)
The experiment was conducted in the same manner as in Example 1 except that tetrabromoethane (TBE) was used as the solvent. Table 1 shows the experimental results.

(Comparative Example 1)
The experiment was performed in the same manner as in Example 1 except that water was used as the solvent. Table 1 shows the experimental results.

(Comparative Example 2)
The experiment was performed in the same manner as in Example 1 except that ethanol was used as the solvent. Table 1 shows the experimental results.

(Comparative Example 3)
The experiment was conducted in the same manner as in Example 1 except that n-hexadecane, a nonpolar solvent, was used as the solvent. Table 1 shows the experimental results.

<Experimental results in Table 1>
Table 1 shows the experimental results of Examples 1 to 3 and Comparative Examples 1 to 3.

As shown in Table 1, when the solvents of Example 1 and Example 2 were used, the solvent operated regardless of the volume and time of the solvent. In this embodiment, whether or not the solvent has operated is determined by determining whether or not the solvent 203 has operated for 20 mm or more after 4 seconds have elapsed since the time when the operation direction was switched first after that time. When the operation is less than 20 mm, it was determined that “does not work”. It is considered that the same result can be obtained by using a known method as a method for determining whether or not the solvent has been operated.

The TBE of Example 3 was 3 μL, and the solvent operated immediately after dropping, 5 minutes after dropping, and 10 minutes after dropping. The TBE of Example 3 was 5 μL, and the solvent operated immediately after the dropping, 5 minutes after the dropping, and 10 minutes after the dropping.

However, when TBE is 5 μL and immediately after dropping, 5 minutes after dropping, and 10 minutes after dropping, and when TBE is 10 μL, immediately after dropping, 5 minutes after dropping, and 10 minutes after dropping. TBE did not work. TBEs with 5 μL and 10 μL were observed to change wettability when voltage was applied, but did not move.

The water of Comparative Example 1 operated immediately after dropping in any volume. However, water started to evaporate immediately after dropping, and the volume of water decreased. Five minutes after the dropping, the water having a volume of 3 μL and 5 μL was evaporated, and it was judged that it did not operate because almost all of the water was lost. In the case of water having a volume of 10 μL, the volume became less than several μL after 5 minutes, and the device became inoperative. The reason why the device did not operate at several μL despite the same volume is thought to be that dirt (or scale) adhered to the water-repellent film 206 after the water evaporated. It was judged that the water of Comparative Example 1 did not operate because water disappeared after 10 minutes in any volume.

The ethanol of Comparative Example 2 did not operate at any volume and time. When voltage was applied, it was confirmed that ethanol wettability changed on the electrode, but it did not move. This is probably because ethanol has a small polar force component. In addition, ethanol having any volume was evaporated after 5 minutes or 10 minutes from dropping.

The n-hexadecane of Comparative Example 3 did not operate at any volume and time. Even when a voltage was applied, it was not possible to confirm a change in the wettability of n-hexadecane, and n-hexadecane did not operate.

From the above results, in Examples 1 to 3, the solvent operates even after a predetermined time from the dropping of the solvent, whereas in Comparative Examples 1 to 3, the solvent operates after the predetermined time from the dropping of the solvent. There wasn't. In other words, by using formamide, ethylene glycol monoethyl ether, or TBE as a solvent, it was found that the solvent operates even after a predetermined time from the dropping of the solvent.

Furthermore, in Examples 1 and 2, the solvent operated even when the volume of the solvent was large. In other words, it has been found that by using formamide or ethylene glycol monoethyl ether as a solvent, the solvent operates even when the volume of the solvent is large.

Next, according to Examples 4 and 5, an experiment was conducted to determine whether or not the same effect can be obtained even when formamide and ethylene glycol monoethyl ether are mixed.

Example 4
ITO was used as the material of the electrode 201 and the electrode wiring 202.

The electrode 201 and the electrode wiring 202 were formed on the substrate.

As the dielectric 205, SiO ₂ having a thickness of 150 nm was formed on the substrate 204, the electrode 201 made of ITO, and the electrode wiring 202 by sputtering.

As the water repellent film 206, CYTOP (registered trademark, manufactured by Asahi Glass Co., Ltd.) having a thickness of about 2 μm was applied on SiO ₂ by spin coating.

As the solvent 203 of Example 3, a solvent in which formamide and ethylene glycol monoethyl ether were mixed was used. As shown in Table 2, the specific ratio was 36.5% for formamide and 63.5% for ethylene glycol monoethyl ether. The mixing ratio indicates the volume fraction.

An experiment was conducted to determine whether or not the solvent works immediately after dropping 10 μL of the solvent 203 on the water-repellent film 206 and at each time 30 minutes after the dropping. The experimental environment was in the atmosphere. Table 3 shows the experimental results.

(Example 5)
The experiment was performed in the same manner as in Example 4 except that the mixing ratio of formamide and ethylene glycol monoethyl ether was different as the solvent. As shown in Table 2, the specific ratio was 90.7% for formamide and 9.3% for ethylene glycol monoethyl ether. The mixing ratio indicates the volume fraction.

Next, an experiment was conducted according to Example 6 to determine whether the same effect can be obtained even when formamide and water are mixed. Table 3 shows the experimental results.

(Example 6)
The experiment was performed in the same manner as in Example 3 except that the mixing ratio of water and formamide was used as the solvent. The specific ratio was 20% for water and 80% for formamide. The mixing ratio indicates the volume fraction.

In addition, each material of the solvent used in Examples 4 to 6 corresponds to a material having a surface tension of 30 mN / m, 40 mN / m, 50 mN / m, or 60 mN / m as defined in JIS K6768. Table 3 shows the experimental results.

Table 2 shows specific ratios of Examples 4 to 6.

<Experimental results in Table 3>
In addition to Examples 4 to 6, also in Example 2, whether or not the solvent operates immediately after dropping 10 μL of the solvent 203 on the water-repellent film 206 and at each time 30 minutes after the dropping. The experiment was conducted. Table 3 shows the experimental results.

According to the experimental results for the solvents of Examples 2 and 4 to 6, it was found that the solvent operates immediately after dropping and at each time 30 minutes after dropping. When the electrode 201 is made of ITO, the resistance of the electrode 201 is higher than that of the first embodiment. That is, it is a disadvantageous condition when applying a voltage, but there is no change in the operation of the solvent as in Example 1, and the solvent depends on the type of electrode 201 in Example 1 and Example 2 being different. It is considered that the influence on the operation of 203 is small.

In Example 6, it was observed that the volume of the solvent decreased at the time 30 minutes after the dropping. It is thought that water contained in the solvent has evaporated. The solvent of Example 6 worked even when the water contained in the solvent evaporated.

From the results of Examples 4 and 5, it was found that when a mixture of formamide and ethylene glycol monoethyl ether was used as the solvent, the solvent operated by applying a voltage. From this result, it is considered that the solvent of the mixture of the materials of Examples 1 to 3 operates when a voltage is applied.

From the results of Example 6, it was found that when a mixture of ethylene glycol monoethyl ether and water was used as a solvent, the solvent was operated by applying a voltage even 30 minutes after dropping. When the solvent is composed of water, the solvent does not operate by applying a voltage 30 minutes after dropping. That is, in the mixture of the materials of Examples 1 to 3 and a material that does not operate when used as a solvent, it is considered that the solvent operates by applying a voltage even after 30 minutes from dropping. This is considered to be because the polar force component of the mixed solvent became a value of 3.1 mN / m or more and 28.8 mN / m or less by mixing two kinds of solvents as described below. . When ethylene glycol monoethyl ether and water are mixed, if the proportion of water is 20% by volume or less, the polar force component of the solvent after mixing satisfies the above-mentioned range. That is, the mixed solvent of ethylene glycol monoethyl ether and water preferably contains water at a ratio of greater than 0 to 20% by volume or less.

式（２）のｃｏｓθは、接触角を示す。本願明細書では、溶媒の極性力成分（γ_L ^P）（*Ｐが大文字）は、極性成分（γ_L ^p）と水素結合成分（γ_L ^h）の和で表される。同様に、撥水膜の極性力成分（γ_S ^P）（*Ｐが大文字）は、極性成分（γ_S ^p）と水素結合成分（γ_S ^h）の和で表される。 <Calculation of polar force component>
Here, a method for calculating the polar force component (γ ^P ) will be described. Formulas (1) and (1 ′) show Fokes formulas, and formula (2) shows extended Fowkes formulas. The surface tension (γ) can be defined for both the water-repellent film and the solvent. The surface tension (γ _L ) of the solvent can be determined by the Fokes equation shown in the equation (1) according to the dispersion component of the solvent (γ _L ^d ), Polar component (γ _L ^p ), and hydrogen bond component (γ _L ^h ). Similarly, the surface tension (γ _S ) of the water-repellent film is determined by the Fokes equation shown in the expression (1 ′) according to the dispersion component (γ _S ^d ), polar component (γ _S ^p ), and hydrogen bond component of the water-repellent film. Expressed as the sum of (γ _S ^h ).

In the equation (2), cos θ represents a contact angle. In the present specification, the polar force component (γ _L ^P ) (* P is capital letters) of the solvent is represented by the sum of the polar component (γ _L ^p ) and the hydrogen bond component (γ _L ^h ). Similarly, the polar force component (γ _S ^P ) (* P is capital letters) of the water repellent film is represented by the sum of the polar component (γ _S ^p ) and the hydrogen bond component (γ _S ^h ).

^{_{First, γ L, γ L d,}} γ L p, using gamma _L ^h is a known three solvents (A, B, C) and, gamma _S is the known water-repellent film, γ _S ^d, γ _S ^p and γ _S ^h are calculated. Specifically, the contact angles cos θ _A , cos θ _B , and cos θ _C between the three types of solvents (A, B, and C) and the water repellent film are measured. Since each contact angle satisfies the equation (2), the matrix of the following equation (3) is established, and γ _S ^d , γ _S ^p , and γ _S ^h of the water repellent film can be calculated. The subscripts A, B, and C at the lower right of γ indicate three types of solvents, respectively.

This measurement and calculation are performed for three types of water-repellent films X, Y, and Z. Thereby, γ _S ^d , γ _S ^p , and γ _S ^h for the water repellent films X, Y, and Z can be obtained, respectively.

These values of the solvents whose γ _L , γ _L ^d , and γ _L ^h are unknown are obtained by measuring the contact angles cos θ _X , cos θ _Y , and cos θ _Z according to the formula (4), and obtaining the water repellent films X, Y, and Z Can be calculated by using γ _S ^d , γ _S ^p , and γ _S ^h . In Expression (4), subscripts X, Y, and Z at the lower right of γ indicate three types of water-repellent films, respectively.

In this example, water, tetrabromoethane, and hexadecane were used as solvents with known γ _L , γ _L ^d , γ _L ^p , and γ _L ^h . Table 4 shows γ _L , γ _L ^d , γ _L ^p , and γ _L ^h of these solvents.

As the water repellent film, CYTOP, AF1600, polypropylene and FAS-17 (3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9 shown in Table 5 are used. , 10,10,11,11,12,12,12-Henicosafluorododecyloxysilane), and the solvent shown in Table 4 was dropped on them. Since the three solvents show different contact angles, the contact angle of the water-repellent film was measured using a contact angle meter (“DM500” manufactured by Kyowa Interface Chemical Co., Ltd.). Using the obtained contact angle, γ _S , γ _S ^d , γ _S ^p , γ _S ^h , and γ _S ^P of the above-described water-repellent film were obtained by Equation (3). The results are shown in Table 5.

In order to determine the polar force component (γ _L ^P ) of the solvents of Examples 1 to 6 and Comparative Examples 1 to 3, Cytop, Polypropylene and FAS-17 were used as the water repellent film, and Examples 1 to 6 and Comparative Example The solvent of Examples 1 to 3 was dropped on these water-repellent films, and the contact angle was determined. Using the calculated contact angles and γ _S ^d , γ _S ^p , γ _S ^{h of} Cytop, polypropylene and FAS-17, from the formula (4), the solvents of Examples 1 to 6 and Comparative Examples 1 to 3 γ _L , γ _L ^d , γ _L ^p , γ _L ^h , and γ _L ^P were determined. Table 6 shows γ _L and γ _L ^P.

Table 7 shows the surface tension (γ _L ) and the polar force component (γ _L ^P ) of the solvent for Examples 1 to 6 and Comparative Examples 1 to 3 described above. Moreover, immediately after dropping the solvent and 30 minutes after the dropping, a voltage was applied to indicate whether or not the solvent was operated.

<Experimental results of Table 1 and Table 7>
As shown in Table 7, Examples 1 to 6 are at least one selected from amide, glycol, glycerin, amino alcohol, hydroxyamine, and polyhydric alcohol, and 3.1 mN / m or more and 28. It has a polar force component of 8 mN / m or less. More specifically, the materials of Examples 1-6 include at least one selected from formamide, ethylene glycol monoethyl ether, and tetrabromoethane. Thereby, the solvent can be operated even after a predetermined time since the solvent was dropped.

As shown in Table 7, the solvent operated when the volume of tetrabromoethane according to Example 3 was 3 μL. However, as shown in Table 1, the solvent did not work when the volume of tetrabromoethane was 5 μL and 10 μL. That is, even if it contains at least one selected from formamide, ethylene glycol monoethyl ether, and tetrabromoethane, and the polar force component is 3.1 mN / m or more and 28.8 mN / m, the volume of the solvent Depending on the solvent could not be operated.

The polar force component of Example 3 was 3.2 mN / m. On the other hand, the polar force component of Example 2 was 3.3 mN / m, which is substantially the same as the polar force component of Example 3. However, as shown in Table 1, the solvent of Example 2 did not depend on the volume and the solvent operated, but in Example 3, there was a difference in whether or not the solvent operated depending on the volume. It was. That is, according to the study by the present inventors, it has been found that the conditions for moving the solvent by EW may depend not only on the polar force component of the solvent but also on the material of the solvent.

When containing at least one selected from formamide and ethylene glycol monoethyl ether and having a polar force component of 3.1 mN / m or more and 28.8 mN / m or less as in Examples 1, 2, 4 to 6 In addition, the dependency of the volume of the solvent can be reduced, and the solvent can be operated even after a predetermined time after the solvent is dropped.

Moreover, in Example 6, although the solvent could be operated even 30 minutes after the dropping, the volume of the solvent decreased. This result shows that the solvent has a polar force component of a predetermined level or more by containing water, but causes a reduction in volume. By reducing the volume, it may be difficult to arrange on the plurality of electrodes. Therefore, it is desirable to suppress a reduction in the volume of the solvent after the solvent has been dropped.

Therefore, as in Examples 1, 2, 4, and 5, the solvent used for EW includes at least one selected from formamide and ethylene glycol monoethyl ether, and is 3.1 mN / m or more and 22.0 mN. It is more desirable to have a polar force component of / m or less. Thereby, the volume reduction of the solvent can be suppressed, the dependency on the volume of the solvent can be reduced, and the solvent can be operated even after a predetermined time by dropping the solvent. It was found that the same effects can be obtained when the volume of the solvent in Examples 1, 2, 4, and 5 is at least 3 μL or more and 10 μL or less.

<Results of drive voltage>
FIG. 4 shows the results of measuring the minimum driving voltage at which the solvent can be operated using the solvents of Examples 1 to 6. The vertical axis in FIG. 4 is the lowest drive voltage (V), and the horizontal axis is the polar force component (mN / m) of the solvent.

After the solvent 203 was dropped on the water repellent film, the applied voltage was gradually increased, and the voltage at which the solvent 203 started to move was defined as the minimum driving voltage.

As shown in FIG. 4, the minimum driving voltage becomes lower as gamma _S ^P is small. Therefore, it is possible to operate the solvent at a low voltage, gamma _S is desirably ^P is small.

<About the polar force component of the water repellent film>
It was confirmed whether there was a difference in the operation of the solvent depending on the polar force component of the water repellent film. Table 5 shows the water-repellent film used. Table 5 shows γ _S ^d , γ _S ^p , and γ _S ^h of these water-repellent films. The polar force component (γ _S ^P ) of the water repellent film is expressed as the sum of the polar component (γ _S ^p ) of the water repellent film and the hydrogen bond component (γ _S ^h ) of the water repellent film.

3 μL of nine types of liquids of Examples 1 to 6 and Comparative Examples 1 to 3 were dropped on four types of water repellent films, and the behavior of the solvent immediately after the dropping was observed. The results are shown in Table 8. The Cytop data is the same as the data immediately after dropping in (Table 4). ○ indicates that the solvent has moved, and x indicates that it has not moved. These definitions are the same as those described with reference to Table 1.

From Table 8, the operation of polypropylene and FAS-17 having a large polar force component (γ _S ^P ) of the water-repellent film could not be confirmed regardless of the polar force component (γ _L ^P ) of the solvent. On the other hand, when Cytop and AF1600 having a small polar force component of the water repellent film were used, it was found that any of the solvents in Examples 1 to 6 can be used to move the solvent.

The contact angles of FAS-17 and CYTOP with pure water (10 mL) are 105.7 ° and 110 °. From the viewpoint of static wettability, these water-repellent films have comparable wettability. It is thought that there is. However, there is a large difference between the polar force components of FAS-17 and Cytop, and this difference is thought to have caused a difference in the ability of EW to move the solvent.

Thus, it was found that the polar force component of the water-repellent film is preferably small for the movement of the solvent by EW, and preferably has a polar force component of 0.2 mN / m or more and 0.3 mN / m or less.

<Other physical properties>
The formamide of Example 1 had a specific gravity of 1.13 (g / cm ³ ), a boiling point of 210 ° C., a melting point of 2 ° C. to 3 ° C., and a vapor pressure of 0.11 hPa. The ethylene glycol monoethyl ether of Example 2 had a specific gravity of 0.93 (g / cm ³ ), a boiling point of 135 ° C., a melting point of −70 ° C., and a vapor pressure of 0.5 kPa.

Comparative Example 1 had a specific gravity of 1, a boiling point of 100 ° C., a melting point of 0 ° C., and a vapor pressure of 23 hPa. Since the materials of Examples 1 and 2 have a boiling point higher than that of water and have a low vapor pressure, they are difficult to evaporate and have a small volume change. Desirably used in the solvent used in 1.

As described above, since the solvent according to this embodiment can be operated for a long time after the solvent is dropped, it is suitable for a solvent control method (for example, transportation of parts) used in an environment such as a biochip or outdoors. Used for.

The solvent control method according to the present disclosure is useful for stably controlling a solvent by EW. In particular, the removal of a solvent, a reagent, a test sample by a biochip or the like, or solvent removal in an outdoor environment, component transportation Can be used in fields.

201, 201a, 201b, 201c, 201d, 201e Electrode 202, 202a, 202b, 202c, 202d, 202e Electrode wiring 203 Solvent 204 Substrate 205 Dielectric 206 Water repellent film 207 Power supply

Claims (10)

A solvent control method for controlling the position of a solvent using a solvent control device,
The solvent control device includes:
A substrate,
A plurality of electrodes disposed on the substrate;
A dielectric disposed to cover the substrate and the plurality of electrodes;
A water-repellent film disposed on the dielectric and having water repellency;
By applying a voltage to the plurality of electrodes, the position of the solvent on the water repellent film is controlled,
The solvent includes at least one selected from the group consisting of formamide, ethylene glycol monoethyl ether, and tetrabromoethane, and has a polar force component of 3.1 mN / m or more and 28.8 mN / m or less. Control method. The solvent includes at least two selected from the group consisting of formamide, ethylene glycol monoethyl ether, and water.
The solvent control method according to claim 1. The solvent has a polar force component of 3.1 mN / m or more and 22.0 mN / m or less,
The solvent control method according to claim 2. The solvent has a volume of 3 μL or more and 10 μL or less;
The solvent control method according to claim 3. The water repellent film has a polar force component of 0.2 mN / m or more and 0.3 mN / m or less,
The solvent control method according to claim 1. The solvent control method according to claim 5, wherein the water repellent film is made of an amorphous fluororesin. Polarity including at least two selected from the group consisting of amide, glycol, glycerin, aminoalcohol, hydroxyamine, polyhydric alcohol, halogenated hydrocarbon and water, and having a polarity of 3.1 mN / m or more and 28.8 mN / m or less An electrowetting solvent having a force component. The electrowetting solvent includes at least two selected from formamide, ethylene glycol monoethyl ether, tetrabromoethane, and water.
The solvent for electrowetting of Claim 7. The electrowetting solvent includes at least two selected from formamide, ethylene glycol monoethyl ether, and water.
The solvent for electrowetting of Claim 8. The solvent for electrowetting according to claim 9, wherein the solvent for electrowetting has a polar force component of 3.1 mN / m or more and 22.0 mN / m or less.

Images