JP2006021067A - Droplet transporting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a droplet transporting apparatus that is capable of reducing the transporting energy of droplets, enhancing the transporting rate and of reducing the damage to the droplets. <P>SOLUTION: An oil membrane 5 is formed on the surface of a substrate 1 having the water repellent treatment applied thereon. For the droplet 6 which becomes easily movable on the substrate 1, the substrate 1 is partially heated by electrically conducting to a heater 2 at the proximity of the droplet 6 and the droplet 6 is transferred in the direction of the lower temperature by means of the stream 7 of the oil membrane 5 by transferring the oil membrane 5 at the heated place to the periphery of the lower temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a droplet transport device, and can be used, for example, as a transport device for a small amount of liquid for confirming a reaction with a small amount of a reagent in chemical analysis or biological examination.

  Conventional chemical analysis and synthesis at the test tube level requires samples and reagents on the order of milliliters, and may be difficult to perform when sampling is difficult or when reagents are expensive. there were. In biopsy, sample collection imposes a burden on the subject, and it is desired that analysis can be performed with a small amount of sample and reagent.

  From this point of view, a system called “lab-on-chip” or “micro-total analysis system” that controls chemical reactions in a small chip and efficiently performs chemical analysis and chemical synthesis has recently been proposed. ing.

  In order to realize this system, a technology for freely transporting a small amount of liquid is indispensable. As this transport technology, for example, attempts have been made to form a very small pipe using a semiconductor process to transport or react a small amount of liquid.

  On the other hand, the method of transporting independent droplets without forming a pipe line is desired by dissolving / mixing different types of reagents and samples in individual droplets or systematically changing the concentration. This is a method for transporting a trace amount of liquid that is suitable for carrying out a reaction by combining droplets in a combination and automating the measurement of the result.

  The droplet itself is an independent container and also a reaction container that can be easily combined and mixed with other droplets. It is also a sample cell for measuring the reaction result. For example, the measurement can be automated by sequentially transporting the droplets to the place where the spectroscopic measurement is performed.

Orlin D. Velev, Brian G. Prevo, Katan H. Bhatt, “On-chip manipulation of free droplets”, Nature, vol. 426, 2003, p. 515-516 Sung Kwon Cho, Hyejin Moon and Chang-Jin Kim, “Creating, Transporting, Cutting, and Merging Liquid Droplets by Electorowetting-Based Actuation for Digital Microfluidic Circuits”, J. Microelectromech. Syst., Vol. 12, 2003, p. 70 -80 Pei Yu Chiou, Hyejin Moon, Hiroshi Toshiyoshi, Chang-Jin Kim, Ming C. Wu, “Light actuation of liquid by optoelectrowetting”, Sensors and Actuators A, vol.104, 2003, p.222-228 Anton A. Darhuber, Joseph P. Valentino, Sandra M. Troian and Sigurd Wagner, “Thermocapillary Action of Droplets on Chemically Patterned Surfaces by Programmable Microheater Arrays”, J. Microelectromech.syst., Vol.12, 2003, p.873- 879

  There have been two types of droplet transports that have been proposed so far: transporting water droplets suspended in oil and transporting only water droplets. The form of transporting only water droplets can be considered as water droplets in the air. Further, it can be classified into a format that uses an electric field as the driving force of the droplet and a format that changes the surface tension according to the electric field or temperature to obtain a driving force.

  In addition, there is a method of transporting water droplets by pumping the oil filling the flow path and placing it on the flow, but in order to perform operations such as coalescence of water droplets, a method of applying force directly to the water droplets is separately provided. Since it is necessary to prepare, it is excluded here.

  The method of transporting water droplets by applying an electric field uses the principle that the presence of a substance with a high dielectric constant in a location where the electric field is strong makes the energy of the system low and stable. Water droplets are transported using the generated force as a driving force (see Non-Patent Document 1 above). In the case of water droplets in oil, it receives force from the electric field due to the difference in dielectric constant between water and oil. Since the specific gravity of water and oil is relatively close, the water droplets exist as spherical droplets in the oil and can be moved in the oil by the action of an electric field.

  In the case where the water droplet does not float in the oil and directly contacts the substrate, it is necessary to perform water repellent treatment on the substrate surface so that the water droplet easily rolls on the substrate surface. Alternatively, non-polar oil or liquid having a specific gravity greater than that of water may be applied to the surface of the substrate so that the water droplets are floated.

  In this way, the water droplet is made to be easily moved, and the water droplet is moved to a location where the electric field is strong due to the difference between the water droplet and the surrounding dielectric constant. This is the same principle as dielectrophoresis in which polarizable fine particles are driven by an electric field, and a spatial gradient of the electric field strength is required.

  In addition, a driving force is generated in the same direction in both a DC electric field and an AC electric field. In general, since the dielectric constant changes depending on the frequency of the AC electric field, the maximum driving force may be obtained when the AC electric field has a specific frequency.

  Electrophoresis is an electrophoretic phenomenon that occurs in charged fine particles and occurs even in a uniform electric field. Although the colloidal particles to be electrophoresed appear to be neutral as a whole, the particles themselves are charged and have opposite polarity ions around them. Electrophoresis occurs under the direction force. Electrophoresis is effective only in a DC electric field and depends on the direction of the electric field.

  A problem of the above-described method of driving a droplet by an electric field is that a required applied voltage is as high as several hundred volts. In addition, in order to facilitate driving, this high voltage may be applied as a high frequency of several hundred KHz, and a large-scale power supply device is required.

  On the other hand, the method for obtaining the driving force by changing the surface tension with an electric field is based on the principle that the effective interfacial energy is reduced by accumulating charges on the contact surface between the liquid and the solid by applying the electric field. (See Non-Patent Documents 2 and 3 above.) Therefore, the water droplet needs to be partially wetted with respect to the substrate (the contact angle of the water droplet with respect to the substrate is higher than 0 degree and lower than 180 degree). Further, it is required that the water droplets have conductivity and that the contact surface between the water droplets and the substrate constitutes a parallel plate capacitor.

  When an electric field is applied to a part of the water droplet, the surface tension of the liquid-solid interface in the portion to which the electric field is applied decreases, and the contact angle of the water droplet decreases. Therefore, the water droplet moves to the side where the electric field is applied. This method can be driven at a lower voltage than the method of directly driving with an electric field, but still requires a voltage of several tens of volts.

  As a method of driving at a low voltage, it has been proposed to give a temperature gradient to a droplet (see Non-Patent Document 4 above). In the method of applying a temperature gradient by a heating means such as a heater, the voltage applied to the heater can be lowered to several volts by designing the heater resistance. Since this method utilizes the fact that the surface tension of the gas-liquid interface of the droplet is lowered by heating, it is necessary to heat the droplet itself.

  In addition, since the driving force is generated only when the contact angle of the liquid whose surface tension is reduced by heating becomes 0 degrees and the substrate is completely wetted, the driving force is weak, Although the power consumption is large, there is a problem that the moving speed of the droplet is extremely slow. According to Non-Patent Document 4, the droplet moving speed at a heater output of 240 mW is as slow as 0.27 mm / s. Furthermore, since this method heats the droplet, there is a problem in that it cannot be applied when the drug or test sample dissolved in the droplet is susceptible to thermal damage.

  The present invention has been made in view of the above situation, and reduces the energy (low voltage, low power consumption) at the time of droplet transportation, increases the transportation speed, and damages the droplet and the medicine in the droplet. An object of the present invention is to provide a droplet transport device that can be transported without being given.

The droplet transport device according to the present invention for solving the above problems is as follows.
In a droplet transport device that transports aqueous droplets on the surface of a substrate,
The surface of the substrate is water-repellent and an oily film is formed on the surface.
The droplet transporting apparatus is characterized in that a heating means for generating a local temperature gradient is provided on the surface of the substrate.

The droplet transport device according to the present invention for solving the above problems is as follows.
In a droplet transport device that transports oily droplets on the surface of a substrate,
The surface of the substrate is treated with oil repellency, and an aqueous film is formed on the surface.
The droplet transporting apparatus is characterized in that a heating means for generating a local temperature gradient is provided on the surface of the substrate.

  In the above invention, the substrate surface is subjected to a surface treatment that repels the droplets to be transported, and a liquid film having properties opposite to those of the droplets (for example, oil and water) is formed on the substrate surface. A droplet placed on the surface is transported by using a force (thermocapillary phenomenon) generated by a temperature change in the surface tension of a liquid film-air interface around the droplet.

Moreover, in the droplet transport device,
There is another substrate provided opposite to the substrate, the surface of the other substrate is subjected to the same kind of treatment as the surface of the substrate, and the same kind of film is formed,
The liquid droplet transporting apparatus is characterized in that the liquid droplet moves in a space sandwiched between the substrate and the other substrate.

Moreover, in the droplet transport device,
The contact angle of the film to the substrate surface is approximately 0 degrees;
The droplet is a droplet transport device characterized in that a contact angle with the substrate surface in the film is larger than 90 degrees.

  Regarding the properties of the surface of the substrate, the properties of the liquid film, and the properties of the droplets, the substrate surface is easily wetted by the liquid film, and the substrate surface and the liquid film are easy to repel the droplets. Make it easy to move.

Moreover, in the droplet transport device,
In at least one of the surface of the substrate and the surface of the other substrate, a guide groove is formed along the transport direction of the droplet.

Moreover, in the droplet transport device,
The guide groove is a droplet transporting device having a width substantially equal to the radius of the droplet.

Moreover, in the droplet transport device,
The guide groove is a droplet transport device characterized by being intermittently formed along the transport direction of the droplet.

Moreover, in the droplet transport device,
In at least one of the surface of the substrate or the surface of the other substrate, a groove for adjusting the thickness of the film is formed.

  By using the droplet transport device of the present invention, water droplets (or oil droplets) can be transported on the substrate surface at high speed with low voltage and low power consumption. In addition, as for the effect of heating during transportation, the system is driven by heating the surrounding oil film (or water film), so even if heat is applied to the water droplet (or oil droplet), it is indirectly through the oil film (or water film). In addition, the water droplet (or oil droplet) is moved so as to avoid a place where the temperature is high, so that it is less affected by heat. Therefore, damage to water droplets (or oil droplets) and a sample or chemical liquid melted / mixed therein by heating can be reduced.

<First Embodiment>
1 and 2 are explanatory diagrams for explaining the principle of movement of a droplet in the droplet transport device according to the first embodiment. FIG. 1 shows the basic principle and FIG. 2 shows the principle of continuous movement. Yes. Hereinafter, the principle of moving a droplet will be described based on these drawings.

  As shown in FIG. 1, a heater 2 for generating a local temperature gradient on the substrate surface is provided inside the lower substrate 1 and is operated by a power source 4 and a switch 3. Further, the surface of the lower substrate 1 is subjected to water repellent treatment and an oil film 5 is formed.

  In this state, when the water droplet 6 is placed on the surface of the substrate 1, the water droplet 6 receives a downward force F pressed against the surface of the substrate 1 due to the surface tension of the oil film. Furthermore, since the contact angle θ of the water droplet 6 with respect to the substrate 1 in oil is larger than 90 degrees, the water droplet 6 can easily move on the substrate 1.

  When the heater 2 is energized and the substrate 1 is partially heated, the oil film 5 at the heated location moves to a low temperature environment (the moving direction 7 of the oil film by heating) due to the thermocapillary phenomenon. When the heated location is in the vicinity of the water droplet 6, the water droplet 6 also moves in the direction of lower temperature due to the flow 7 of the oil film.

  FIG. 2 is a diagram showing the principle of transporting water droplets continuously. As shown in the figure, a plurality of heaters 2a to 2d are arranged linearly inside the lower substrate 1, and by energizing the heater 2a by the switch 3a to heat the upper oil film 5, As a result of the generation of the flow 7a in the oil film 5, a force that moves in the direction 8 acts on the water droplet 6a ((a) in the figure). As a result, the water droplet 6a moves to the position of the water droplet 6b ((b) in the figure).

  Next, by energizing the heater 2b by the switch 3b to heat the upper oil film 5, a flow 7b is generated in the oil film 5, and as a result, a force that moves in the direction 8 acts on the water droplet 6b ((b) in the figure). . As a result, the water droplet 6b moves to the position of the water droplet 6c ((c) in the figure). Further, by energizing the heater 2c by the switch 3c to heat the upper oil film 5, a flow 7c is generated in the oil film 5, and as a result, a force that moves in the direction 8 acts on the water droplet 6c ((c) in the figure).

  As described above, the heaters 2a to 2d are operated in conjunction with the movement of the water droplet 6, and the temperature gradient is continuously applied to the vicinity of the water droplet 6 so that the water droplet 6 can be moved in a desired direction and distance. .

  FIG. 3 is a schematic plan view of the droplet transport device according to the first embodiment. As shown in the figure, the droplet transport device 10 includes a lower substrate 11, guide grooves 19, 19 a, 19 b that are intentionally formed on the surface of the substrate 11, and the substrate 11 along the guide grooves. The heaters 12, 12a to 12g are systematically arranged inside, and an oil film amount adjusting groove 20 formed on the surface of the substrate 11 in the vicinity of the guide groove.

  The water droplets 16, 16a, 16b to be transported are transported by moving in the guide groove, and the size thereof is about 0.5 mm to 2 mm in diameter. The liquid volume is on the order of microliters. The heaters 12 and 12a to 12g are arranged at intervals similar to the diameters of these water droplets, the heaters and their wirings are covered with an insulating layer, and guide grooves are formed in the insulating layer. .

  The surface of the lower substrate 11 is subjected to water repellent treatment. When oil is applied, the surface gets wet well with oil, and the entire surface is thinly covered with an oil film. The oil film amount adjusting groove 20 is a plurality of thin grooves (grooves having a dimension width sufficiently smaller than the diameter of the water droplet) for adjusting the thickness of the oil film.

  When a water droplet to be transported is placed on the guide groove and heated by energizing a heater in the vicinity of the water droplet, the water droplet moves away from the heating location as described with reference to FIGS. For example, when the water droplet 16a is placed on the guide groove 19a and the heater 12a near the water droplet 16a is energized and heated, the water droplet 16a moves toward the heater 12b along the guide groove 19a. By sequentially operating the heaters 12b to 12d in conjunction with the movement of the water droplet 16a, the water droplet 16a can be continuously moved along the guide groove 19a (from left to right in FIG. 3).

  Further, when the water droplets move to the intersection of the guide grooves, if the heater arranged in the guide groove shape different from the moved guide grooves is energized, the water droplets are transferred to another guide groove and transported. For example, when the water droplet 16b moves to the intersection of the guide groove 19a and the guide groove 19b by moving the guide groove 19a, when the heater 12e is energized, the water droplet 16b is transferred to the guide groove 19b and moves toward the heater 12g. To do.

  As illustrated in FIG. 1, the water droplet is pressed against the substrate surface by the oil film, and when the guide groove is formed on the substrate, the water droplet is more stable in the guide structure lower than the substrate surface. Can be moved along the guide groove in the form of being dropped into the guide groove.

  In addition, since the force that drives the water droplets due to the temperature gradient works to move away from the center of the heated part, the water droplets need to be located on a straight line between the heating position and the target position to be moved, If it deviates from this linear shape, the moving direction will easily deviate from the intended direction. Therefore, if the guide groove is formed in the substrate and moved along the guide groove, the guide groove can be reliably moved in the target direction.

  When the width of the guide groove is wider than the diameter of the water droplet, it is clear that the force for restoring the position of the water droplet to the center of the guide groove does not work. Further, when the width of the guide groove is extremely narrow, the restoring force hardly acts.

  This restoring force is the difference between the lengths of the left and right edges of the guide groove cut by the circumference of the water drop (the length of the two edge portions of the guide groove crossing the water drop when the water drop is on the guide groove) Proportional to the difference). Therefore, the greatest restoring force works when the width of the guide groove is close to the radius of the water droplet, and the water droplet can be held at the center of the guide groove. As a result, in combination with a means for providing a temperature gradient, water droplets can be transported on a target track.

  The depth of the guide groove needs to be optimized depending on the size of the water droplet to be transported. For example, the depth of the water droplet having a diameter of 1 mm is about 50 μm to 20 μm. If it is too deep, for example, it becomes difficult to cross the intersection of the guide grooves with a driving force due to a temperature gradient. This is because the restoring force for maintaining the water droplet located at the intersection of the orthogonal guide grooves at the center of the intersection becomes relatively large, and it becomes difficult to move the water droplet over the intersection. On the other hand, if it is too shallow, the restoring force is insufficient and water droplets are likely to come off from the guide groove. From the above, the depth of the guide groove has to be deeper as the water droplet is larger, and the depth of the guide groove has to be shallower as the water droplet is smaller.

  When the water droplets are located at the intersection of the guide grooves, if the four heaters surrounding the water droplets are simultaneously driven with the same output, the driving forces due to the surface tension cancel each other and the water droplets remain in that position. If the heating by the heater is continued, the water droplet can be heated. For example, when the water droplet 16b is located at the intersection of the guide groove 19a and the guide groove 19b, when the four heaters 12d, 12e, 12f, and 12g surrounding the water droplet 16b are simultaneously driven with the same output, the water droplet 16b remains in that position. become. If heating by these four heaters is continued, the water droplet 16b can be heated.

  In the droplet transport device 10 according to the present embodiment, when the droplet is transported, the water droplet is not directly heated, but is heated through the surrounding oil film, so that thermal damage to the sample contained in the water droplet is prevented. Can be suppressed. On the other hand, the position of the water droplet can be fixed and heated by the method described above.

  Furthermore, since the surface of the water droplet is exposed to the space, the water in the water droplet can be evaporated. By combining methods such as heating a water droplet with a heater and promoting evaporation by lowering the atmospheric pressure around the water droplet, it is possible to concentrate the sample or drug contained in the water droplet. This function cannot be realized in a transportation method in which water droplets are completely immersed in oil. Similar to the conventional droplet transport technology, the coalescence of droplets is achieved by transporting one droplet to a position where the other droplet exists.

  The thickness of the oil film on the substrate surface is determined by the amount of oil supplied per area, but by forming a large number of narrow grooves on the substrate surface that do not affect the movement of the water droplets (oil film amount adjusting groove 20), Regardless of the amount of oil supplied, the thickness of the oil film can be adjusted to a dimension defined by the groove width.

  If the amount of oil is such that it does not fill all of the oil film amount adjusting groove 20, the oil film pressure is always kept lower than the external pressure, and excess oil is absorbed by the oil film amount adjusting groove 20. As a result, the substrate surface can be kept thin and covered with an oil film. As a result, the amount of oil clinging around the water droplets can be kept to a minimum, and at the same time, an oil film necessary for driving can be maintained on the substrate surface.

<Second Embodiment>
FIG. 4 is a partial schematic cross-sectional side view of the droplet transport device according to the second embodiment. As shown in the figure, thin film heaters 42a and 42b and wirings 42-1 and 42-2 were formed on a glass substrate 41 by photolithography. If the heaters are arranged in a grid, wiring is complicated, so the GND lines common to each heater, the heaters, and the individual wirings are formed as different layers. The wirings 42-1 and 42-2 were made of gold, and the thin film heaters 42a and 42b were made of chrome, each having a thickness of about 5000 angstroms. A 5000 angstrom silica layer was deposited as an insulating layer between the two layers.

  Furthermore, on the plurality of thin film heater elements, the whole was filled with a silica layer of about 1 μm, and thereafter, guide grooves 49a, 49b, 49c having a depth of 20 μm were formed by etching. The guide grooves 49a, 49b, and 49c are not the continuous guide grooves described in the first embodiment, but are formed in spaces between the heaters without the thin film heaters 42a and 42b and the wirings 42-1 and 42-2. .

  The water droplets 46 can be moved by one section of the heater array by the guide grooves 49a, 49b, and 49c formed in a predetermined manner with a predetermined interval. That is, when the water droplet 46 located in the guide groove 49b is heated by energizing the thin film heater 42a, a force that moves the water droplet 46 in the direction 48b is applied to the adjacent guide groove 49c. Can be moved. On the contrary, when the thin film heater 42b is energized and heated, a force to move the water droplet 46 in the direction 48a is applied and can be moved to the adjacent guide groove 49a.

  The thin film heaters 42a and 42b are formed in a meandering shape and have a resistance value of about 1 KΩ. The heater applied voltage required to move the water droplet 46 in one section was 3.8 V, and the moving time was 1 second. The power consumption is 15 mW. The moving speed is as fast as 1 mm / second, and the power consumption is an order of magnitude lower than that of the conventional method.

  The water repellent treatment of the substrate surface was performed by applying silicon oil diluted with a solvent to the surface and baking it at 300 degrees. Other examples of the water repellent treatment include a method of applying a commercially available water repellent, spin-coating Teflon (registered trademark) dissolved in a solvent, or depositing Teflon by sputtering. . The water repellent treated surface is easily wetted with non-polar oil, and when silicone oil is dropped, a thin oil film 45 is formed over the entire surface.

  The oil to be applied to the surface may be any nonpolar liquid that does not mix with water. Silicon oil (dimethylpolysiloxane), fluorinate (perfluorohexane, fluorinated solvent), edible oil (rapeseed oil, etc.) Can be used). In particular, silicon oil is suitable because it has a low vapor pressure and therefore has a small amount of evaporation. Although not shown in FIG. 4, grooves that absorb an excessive amount of oil are formed on the substrate surface so that the oil film 45 does not become thick, and these are formed by etching together with the guide grooves.

<Third Embodiment>
FIG. 5 is a partial schematic cross-sectional side view of the droplet transport device according to the third embodiment. In the first and second embodiments, the water droplets to be transported are positioned on the substrate with the upper portion of the water droplets exposed in the space. It may be preferable to transport water droplets.

  As shown in FIG. 5, in the present embodiment, the upper substrate 60 is disposed in parallel with the lower substrate 51, and water droplets 56 exist in the space between the lower substrate 51 and the upper substrate 60. Yes. On the lower substrate 51, heaters 52a and 52b are arranged in the same manner as in the above-described embodiment. On the other hand, guide grooves 59a, 59b, 59c are formed in the upper substrate 60, and the surfaces of the upper and lower substrates are subjected to water repellent treatment, and an oil film 55 is thinly applied.

  The water droplets 56 are in contact with the opposing surfaces of the upper and lower substrates 51 and 60. As a result, the water droplets 56 are not hemispherical as in the above-described embodiment, but are cylindrical. The water droplets 56 are attracted to the upper and lower substrates 51 and 60 by the surface tension of the oil film 55, respectively, and the guide grooves 59a, 59b and 59c formed in the upper substrate 60 can effectively perform their functions.

  In the third embodiment, as the guide grooves 59a, 59b, 59c formed in the upper substrate 60, straight grooves are formed in a lattice shape by cutting. The upper substrate 60 was overlapped so as to correspond to the heater arrangement of the lower substrate 51, and fixed with a spacer around. Since the space where the water droplet 56 exists is a space sandwiched between the upper and lower substrates 51 and 60, evaporation of moisture in the water droplet 56 can be suppressed. Furthermore, it is easy to make a sealed space by closing the periphery. Also in the third embodiment, water droplets could be transported along the guide groove with substantially the same power and moving speed as in the above-described embodiment.

<Other embodiments>
In each of the above-described embodiments, as a means for generating a local temperature gradient, the metal thin film heater formed on the substrate has been described, but in addition to this, as a heating element, carbon or metal is embedded in the substrate, Or these may be disperse | distributed as microparticles | fine-particles, and you may make it heat locally from the outside with a laser, an alternating electric field, or an alternating magnetic field, and may give a temperature gradient. Furthermore, in order to simplify the wiring of the heater, a semiconductor element such as a diode or a transistor may be incorporated adjacent to each heater to control ON / OFF of the heater.

  The purpose of transporting the water droplets is to mix the desired chemicals or sample into the water droplets and transport them. Water-soluble drugs and samples can be transported by dissolving them directly in water droplets. On the other hand, in the case of a drug that is not water-soluble, for example, the drug can be transported by adsorbing the drug or the like on porous silica and mixing it with water droplets.

  For example, when limonene, which is one of the fragrances, is adsorbed on porous silica and mixed with water droplets, the silica surface is hydrophilic and is trapped inside the water droplets, and the water droplets are collected by a droplet transport device. Even when transported, the oil film did not escape. For limonene adsorbed with silica, no release of limonene was observed during transportation, but when the position of the water droplet was fixed and the water droplet was heated, the release of limonene was observed.

  FIG. 6 is a graph showing changes in limonene release over time due to droplet heating. The experiment was performed by mixing water droplets having a diameter of 2 mm with porous silica spheres (average particle size: 170 μm) on which limonene was adsorbed. In order to heat while maintaining the position of the water droplet, the surrounding four heaters were energized and heated simultaneously (see, for example, the water droplet 16b in FIG. 3). The heating power was 400 mW in total, and the heating time was 5 seconds. Limonene was detected using a measuring device based on the principle of ionization of fragrant molecules by ultraviolet rays.

  As shown in FIG. 6, it can be seen that limonene was released with a delay of several seconds by the first heating. Furthermore, it is hardly detected by the second heating performed continuously, and it can be seen that most of the limonene was released by the first heating.

  As described above, the output of the heater necessary for transporting the droplet is 15 mW, which is an order of magnitude less than the heating necessary for releasing limonene (400 mW). Further, since the water droplets moved away from the heating position, the water droplets themselves were not heated, and limonene was not released during transportation. In this way, by using a kind of hydrophilic capsule called porous silica, it is possible to transport a non-water-soluble drug such as a perfume or to participate in a chemical reaction.

  In each of the above-described embodiments, an example in which a water-repellent treatment is performed on the substrate surface and an oil film is formed to form water droplets as a transport target has been described. On the contrary, an oil-repellent treatment is performed on the substrate surface. In addition, an aqueous film may be formed and oily droplets may be transported. Since the principle in this case is the same principle as each embodiment mentioned above, description is abbreviate | omitted. Since the surface tension of oil is as low as a fraction of that of water, it has a property that is unlikely to be a spherical shape like a water droplet, but this is also in balance with the droplet diameter, and the diameter is about 100 μm or less. It becomes possible to maintain a spherical shape by forming a droplet.

It is explanatory drawing explaining the movement principle of the droplet in the droplet transport apparatus which concerns on 1st Embodiment. It is explanatory drawing explaining the movement principle of the droplet in the droplet transport apparatus which concerns on 1st Embodiment. 1 is a schematic plan view of a droplet transport device according to a first embodiment. It is a partial schematic sectional side view in the droplet transport apparatus which concerns on 2nd Embodiment. It is a partial schematic sectional side view in the droplet transport apparatus which concerns on 3rd Embodiment. It is a graph which shows the time change of limonene discharge | release by the heating of a droplet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lower board | substrate 2 Heater 2a-2d Heater 3 Switch 3a-3d switch 4 Power supply 5 Oil film 6 Water droplet 6a-6c Water droplet 7 Oil film movement direction by heating 8 Water droplet movement direction

θ Contact angle of water droplet to substrate in oil F Surface tension of oil film acting on water droplet

DESCRIPTION OF SYMBOLS 10 Droplet transport apparatus 11 Lower substrate 12 Heater 12a-12g Heater 16 Water droplet 16a, 16b Water droplet 19 Guide groove 19a, 19b Guide groove 20 Oil film amount adjustment groove

41 Lower substrate 42a, 42b Heater
42-1 Wiring
42-2 Interlayer wiring 45 Oil film 46 Water droplets 48a, 48b Movement direction of water droplets 49a-49c Guide grooves

51 Lower substrate 52a, 52b Heater
52-1 Wiring
52-2 Interlayer wiring 55 Oil film 56 Water droplets 58a, 58b Movement direction of water droplets 59a to 59c Guide groove 60 Upper substrate

Claims (8)

In a droplet transport device that transports aqueous droplets on the surface of a substrate,
The surface of the substrate is water-repellent and an oily film is formed on the surface.
A droplet transporting device, wherein a heating means for generating a local temperature gradient is provided on the surface of the substrate. In a droplet transport device that transports oily droplets on the surface of a substrate,
The surface of the substrate is treated with oil repellency, and an aqueous film is formed on the surface.
A droplet transporting device, wherein a heating means for generating a local temperature gradient is provided on the surface of the substrate. In the droplet transport device according to claim 1 or 2,
There is another substrate provided opposite to the substrate, the surface of the other substrate is subjected to the same kind of treatment as the surface of the substrate, and the same kind of film is formed,
The droplet transporting apparatus, wherein the droplet moves in a space sandwiched between the substrate and the other substrate. In the droplet transport device according to any one of claims 1 to 3,
The contact angle of the film to the substrate surface is approximately 0 degrees;
The droplet transport device according to claim 1, wherein a contact angle of the droplet with the substrate surface in the film is larger than 90 degrees. In the droplet transport device according to any one of claims 1 to 4,
At least one of the surface of the substrate or the surface of the other substrate is provided with a guide groove along the droplet transport direction. In the droplet transport device according to claim 5,
The droplet transport device according to claim 1, wherein the guide groove is a groove having a width substantially equal to a radius of the droplet. In the droplet transport device according to claim 5 or 6,
The droplet transport device according to claim 1, wherein the guide groove is formed intermittently along the transport direction of the droplet. In the droplet transport device according to any one of claims 1 to 7,
A droplet transporting device, wherein a groove for adjusting the thickness of the film is formed on at least one of the surface of the substrate and the surface of the other substrate.

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