JP2004190537A - Hydraulically driving method and device using elastic surface wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulically driving method and a device using an elastic surface wave for improving energy efficiency, and reducing costs. <P>SOLUTION: This hydraulically driving device uses the elastic surface wave, and is provided with a piezoelectric base board 1, a standing wave exciting electrode 2 of the elastic surface wave formed on this piezoelectric base board 1, a reflector 3 arranged on both sides of this exciting electrode 2 and liquid set on the standing wave exciting electrode 2 and the reflector 3. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid driving method and apparatus using a surface acoustic wave.
[0002]
[Prior art]
It is widely known that liquids can be pumped or atomized using radiation pressure from ultrasonic vibrations. Among ultrasonic vibrations, surface acoustic waves have a high energy density and are easy to miniaturize. Therefore, it is considered that a small-sized and high-performance pump or atomizer can be constituted by using this.
[0003]
However, since the surface acoustic wave has an extremely small vibration amplitude of several nanometers, it is mainly used mainly in the communication field, and its application to mechanical applications has not been studied much. In particular, studies applying surface acoustic waves to pumps and the like include those by Higuchi and Kurosawa et al. (See [Patent Document 1] below), those by Shiokawa et al. (See [Non-Patent Document 1] below), and surface acoustic waves. And a spraying method (see [Patent Document 2] below) and a developing method (see [Patent Document 3] below).
[0004]
FIG. 6 is a basic configuration diagram of such a conventional surface acoustic wave pump using a traveling wave, and FIG. 7 is a schematic diagram of the principle of transporting the droplet.
[0005]
In these figures, 101 is a piezoelectric substrate, 102 is a comb-shaped electrode (interdigital), 103 is a surface acoustic wave (travelling wave), 104 is a droplet, 105 is a sound absorber (adhesive), 201 is a piezoelectric substrate, 202 is a surface acoustic wave, and 203 is a droplet.
[0006]
As described above, the surface acoustic waves 103 are excited by the comb-shaped electrodes 102 formed on the piezoelectric substrate 101, and propagate as traveling waves on the piezoelectric substrate 101. When the droplet 104 is placed on the propagation path, the droplet 104 is transported in the wave propagation direction by the radiation pressure of the surface acoustic wave 103 (depending on the type of the droplet, the droplet 104 is transported in a direction opposite to the wave propagation direction). A phenomenon has also been reported). Further, by exciting the strong surface acoustic wave 103, the droplet 104 can be broken into small droplets on the surface of the droplet 104, whereby the droplet 104 can be atomized.
[0007]
[Patent Document 1]
JP-A-7-232114, page 2-3, FIG.
[Patent Document 2]
International Publication WO97 / 05960 FIG. 4
[Patent Document 3]
JP-A-4-337772, page 2-3, FIG. 1 and FIG.
[Non-patent document 1]
“Study on SAW Streaming and it's Applications to Fluid Devices”, Shoko SHIOKAWA, et al. , Japanese Journal of Applied Physics, Vol. 29 (1990) Supplement 29-1 pp. 137-139
[0008]
[Problems to be solved by the invention]
However, previous studies using surface acoustic waves for pumps and atomizers have all used traveling waves.
[0009]
A surface acoustic wave pump using a traveling wave has the following problems.
[0010]
First, energy efficiency is low. The traveling wave traveling on the piezoelectric substrate is reflected when reaching the end face of the piezoelectric substrate, and increases the standing wave ratio on the piezoelectric substrate. Since this is an undesirable phenomenon for a pump using a traveling wave, it is usually desirable to absorb the traveling wave by providing a sound absorber near the end face of the piezoelectric substrate.
[0011]
In a prototype example reported in the past, as shown in FIG. 6, an adhesive 105 is used as a sound absorber, thereby absorbing the traveling wave 103 and converting it into heat. In this configuration, most of the input energy is converted into heat, so that the energy efficiency is extremely low.
[0012]
In addition, there is also a problem that continuous driving cannot be performed because the sound absorber generates heat due to driving, which causes breakage of the piezoelectric substrate.
[0013]
Therefore, as another method, it is conceivable to use an energy regeneration method proposed for a surface acoustic wave motor. This uses a comb-shaped electrode (interdigital electrode) as a sound absorber and regenerates vibration energy as electric energy. Although it is considered that high energy efficiency can be achieved by using this method, there is a disadvantage that the circuit configuration is complicated.
[0014]
Another problem is that a traveling wave propagation path is required. In the case of a surface acoustic wave pump using a traveling wave, a droplet is transported on a propagation path of the traveling wave. Therefore, the propagation path is an essential component. However, since a piezoelectric substrate used for exciting surface acoustic waves is generally expensive, the presence of a propagation path contributes to an increase in the cost of the device. In addition, the existence of the propagation path is not desirable in consideration of miniaturization of the device.
[0015]
The present invention has been made in view of the above circumstances, and has as its object to provide a liquid driving method and apparatus using a surface acoustic wave that can improve energy efficiency and reduce cost.
[0016]
[Means for Solving the Problems]
The present invention, in order to achieve the above object,
[1] A liquid driving method using a surface acoustic wave is characterized in that the liquid is conveyed by radiation pressure due to standing wave vibration of the surface acoustic wave.
[0017]
[2] A liquid driving method using a surface acoustic wave is characterized in that the liquid is atomized by radiation pressure due to standing wave vibration of the surface acoustic wave.
[0018]
[3] A liquid drive device using a surface acoustic wave, comprising a piezoelectric substrate, a means for generating a standing wave vibration of a surface acoustic wave formed on the piezoelectric substrate, and a liquid set on the piezoelectric substrate. It is characterized by doing.
[0019]
[4] In the liquid driving device using the surface acoustic wave according to the above [3], the standing wave vibration generating means is formed at a central portion of the piezoelectric substrate, and an excitation electrode for exciting a surface acoustic wave; A reflector formed on both sides of the excitation electrode and reflecting the surface acoustic wave.
[0020]
[5] The liquid driving device using surface acoustic waves according to [4], wherein the excitation electrode is a pair of comb electrodes.
[0021]
[6] The liquid drive device using surface acoustic waves according to [3], wherein the standing wave vibration generating means has a pump function for radiating liquid upward.
[0022]
[7] The liquid driving apparatus using surface acoustic waves according to [3], wherein the standing wave vibration generating means has a spray function of atomizing the liquid.
[0023]
[8] In the liquid driving device using the surface acoustic wave according to the above [3], a mesh plate is provided on or near the set liquid surface, and the liquid is supplied near the mesh plate by the pressure from the surface acoustic wave. It is characterized by atomization.
[0024]
[9] The liquid driving device using surface acoustic waves according to [4], wherein an insulating film is provided on a surface of the excitation electrode.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0026]
FIG. 1 is a perspective view of a standing wave utilizing pump showing a first embodiment of the present invention, and FIG. 2 is a schematic diagram showing the principle of the standing wave utilizing pump.
[0027]
In FIG. 1, reference numeral 1 denotes a piezoelectric substrate, and reference numeral 2 denotes a surface acoustic wave radiator arranged at the center of the surface of the piezoelectric substrate 1. As shown in FIG. It consists of an exciting electrode for exciting. Reference numeral 3 denotes a reflector disposed on both sides of the surface acoustic wave radiator 2 for reflecting the surface acoustic wave, and reference numeral 5 denotes a power supply for supplying a sine wave applied to the excitation electrode 2. In addition, as the piezoelectric substrate 1, for example, lithium niobate, lithium tantalate, or the like can be used.
[0028]
In FIG. 2, a liquid 4 is set on a surface acoustic wave radiator (excitation electrode) 2 and a reflector 3, and the radiation pressure due to the standing wave vibration generated by the electrode acts on the liquid 4. Thus, the liquid 4 is conveyed, and the pump function is performed.
[0029]
The surface acoustic wave pump configured as described above uses a standing wave instead of a conventional traveling wave. That is, by providing the surface acoustic wave radiator (comb-shaped electrode) 2 on the piezoelectric substrate 1 and providing the vibration reflectors 3 at both ends thereof, a standing wave can be excited on the comb-shaped electrode 2. When a droplet is placed on the comb-shaped electrode 2 on which the standing wave is excited, or when the liquid is filled on the comb-shaped electrode 2, the liquid 4 is applied to the surface of the piezoelectric substrate 1 by the radiation pressure from the standing wave. Flied in a vertical direction.
[0030]
In this method, the problem of the conventional traveling wave pump has been solved in principle. That is, since the standing wave is used, there is no need to install a sound absorber, and the excitation energy can be easily confined on the surface of the piezoelectric substrate 1. Therefore, it is possible to drive continuously with high energy efficiency. Since the Q value of resonance is high, it is possible to drive with a lower voltage. Further, since a force is directly applied to the liquid 4 on the electrode 2 for vibration excitation, a wave propagation path is unnecessary. Therefore, it is much more suitable for miniaturization than before.
[0031]
Next, in order to provide the atomization function, a droplet or a liquid layer is set on the electrode 2 to generate a strong energy density in the electrode 2. Thereby, a droplet or a liquid layer can be atomized.
[0032]
In the conventional atomizer using traveling waves, fog is often generated obliquely upward of the substrate, whereas in the method of the present invention, fog is generated upward of the substrate. it can.
[0033]
Further, as shown in a second embodiment of the present invention described below, by installing a mesh plate on the liquid surface, it is possible to generate mist having a uniform particle diameter.
[0034]
FIG. 3 is a schematic view of a liquid driving apparatus according to a second embodiment of the present invention. The same parts as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.
[0035]
In this figure, reference numeral 6 denotes a mesh plate arranged on the surface of the liquid 4 on the electrode, and 7 denotes mist generated by the apparatus.
[0036]
In the device configured as described above, the mist can be generated near the mesh plate 6 by the radiation pressure from the standing wave of the excitation electrode 2, and the particle size of the generated mist 7 can be made uniform. can do.
[0037]
Also, by applying a potential to the mesh plate 6, charged mist droplets 7 can be generated.
[0038]
FIG. 4 is a schematic view of a liquid driving apparatus according to a third embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
[0039]
In this embodiment, the insulating film 8 is formed on the upper surface of the excitation electrode 2.
[0040]
For example, when the liquid is water (tap water), a sufficient effect cannot be obtained with the configuration in which the electrode 2 is exposed to the liquid as in the first embodiment. In such a case, the performance can be improved by forming the insulating film 8 on the surface of the electrode 2. Although the insulating film 8 is formed only on the upper surface of the excitation electrode 2 in this example, the insulating film may be formed on the entire substrate including the reflective film 3.
[0041]
In experiments to date, it has been observed that the behavior differs greatly depending on the droplet. Although the detailed cause is unknown, it is expected that the conductivity and viscosity of the liquid are important parameters. The property of the insulating film shown in the third embodiment is also an important parameter. For example, it may be possible to improve the performance by making the insulating film hydrophilic.
[0042]
Further, the present invention is not limited to the above-described electrode structure, and various electrode structures and arrangements can be performed. Further, even if the excitation is not a vibration due to only a strict standing wave, but is an excitation in which a traveling wave is mixed, the present invention is also included in the scope of the present invention.
[0043]
In addition, although it has been described that the liquid is driven just above the electrode, this is not always a necessary condition. A structure is provided in which a distance is provided between the excitation electrode and the reflector, and a liquid is driven between them, and as shown in FIG. 5 described below, two or more excitation electrodes are arranged to face each other, and A configuration for driving the liquid is also conceivable.
[0044]
FIG. 5 is a schematic view of a liquid driving apparatus according to a fourth embodiment of the present invention.
[0045]
In this figure, 11 is a piezoelectric substrate, 12 and 13 are comb-shaped electrodes as excitation electrodes disposed on both sides of the surface of the piezoelectric substrate 11, and 14 is a liquid (here, a liquid) placed at the center of the surface of the piezoelectric substrate 1. Droplets), 15 and 16 are power supplies for supplying sinusoidal waves to the comb electrodes 12 and 13, respectively.
[0046]
With this configuration, the liquid 14 can be driven by the radiation pressure due to the standing wave vibration from the comb electrodes 12 and 13 serving as the excitation electrodes acting on the liquid 14.
[0047]
The method and apparatus of the present invention include (1) a liquid transport system in a micro drug delivery system (DDS) or nebulizer in the medical field, a micro TAS system in the chemical / pharmaceutical field, and (2) a pump mechanism in a water cooling device for information equipment. (3) It can be widely used, such as a propulsion mechanism for a micro-submersible robot.
[0048]
It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.
[0049]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
[0050]
(A) The liquid can be transported or atomized by utilizing the standing wave vibration of the surface acoustic wave.
[0051]
(B) Since the liquid can be directly transferred on the excitation electrode, it is suitable for miniaturization.
[0052]
(C) The energy density is high because a standing wave is used. Further, it can be driven with a lower voltage.
[Brief description of the drawings]
FIG. 1 is a perspective view of a standing wave utilizing pump according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing the principle of a standing wave utilizing pump showing an embodiment of the present invention.
FIG. 3 is a schematic view of a liquid driving device according to a second embodiment of the present invention.
FIG. 4 is a schematic view of a liquid drive device according to a third embodiment of the present invention.
FIG. 5 is a perspective view of a liquid driving apparatus according to a fourth embodiment of the present invention.
FIG. 6 is a basic configuration diagram of a conventional surface acoustic wave pump using a traveling wave.
FIG. 7 is a schematic diagram of a conventional droplet transport principle.
[Explanation of symbols]
1,11 Piezoelectric substrate 2,12,13 Surface acoustic wave radiator (Excitation electrode: Comb electrode)
3 Reflector 4,14 Liquid 5,15,16 Power supply (Sine wave supply)
6 Mesh plate 7 Fog droplet 8 Insulation film

Claims (9)

A liquid driving method using surface acoustic waves, wherein the liquid is conveyed by radiation pressure caused by standing wave oscillation of surface acoustic waves. A liquid driving method using a surface acoustic wave, wherein the liquid is atomized by radiation pressure caused by standing wave vibration of the surface acoustic wave. (A) a piezoelectric substrate;
(B) means for generating a standing wave vibration of a surface acoustic wave formed on the piezoelectric substrate;
(C) a liquid driving device using surface acoustic waves, comprising: a liquid set on the piezoelectric substrate. 4. The liquid driving device using surface acoustic waves according to claim 3, wherein the standing wave vibration generating means is formed at a central portion of the piezoelectric substrate, and an excitation electrode for exciting surface acoustic waves; And a reflector formed on both sides and reflecting the surface acoustic wave. 5. The liquid driving device using surface acoustic waves according to claim 4, wherein the excitation electrode is a pair of comb-shaped electrodes. 4. A liquid driving apparatus using surface acoustic waves according to claim 3, wherein said standing wave vibration generating means has a pump function for radiating liquid upward. 4. A liquid driving apparatus using surface acoustic waves according to claim 3, wherein said standing wave vibration generating means has a spray function of atomizing the liquid. 4. The liquid drive device using surface acoustic waves according to claim 3, wherein a mesh plate is provided on or near the set liquid surface, and the liquid is atomized near the mesh plate by pressure from the surface acoustic waves. A liquid driving device using a surface acoustic wave, characterized by the following. 5. The liquid driving device using surface acoustic waves according to claim 4, wherein an insulating film is provided on a surface of the excitation electrode.

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