JP4505624B2 - Non-contact filtering method and apparatus using ultrasonic waves - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention controls the trajectory of a minute object in a liquid medium flowing in a flow path, and allows ultrasonic waves to be condensed continuously by passing an arbitrary part in the flow path. The present invention relates to a non-contact filtering method and an apparatus thereof.
[0002]
[Prior art]
Conventionally, factory wastewater, household wastewater, and the like contain a large amount of solids. This is a causative agent that pollutes the environment and should be removed as much as possible. However, if the solid content is large, it can be easily filtered using a net-like filter. However, in the case of fine particles, it is difficult to filter this and discharge only the liquid medium. Of course, it is possible to remove finer fine objects using a fine mesh filter, but there are problems such as clogging, and maintenance is difficult. Further, there is a limit to the size that can be removed by the filter.
[0003]
In addition, chemicals and the like are added to the waste water to agglomerate and coagulate the solid content, but a new chemical is released together with the waste water, which is preferable in view of the environmental impact. Absent. In addition, the discharge of wastewater containing harmful chemical substances is prohibited. In the factory, septic tanks are installed, decomposed using microorganisms, etc., detoxified and discharged. However, useful microorganisms are also discharged at that time.
[0004]
In contrast to conventional filtering using a mesh filter or chemicals, those using ultrasonic waves can be used in a medium that propagates sound waves, and the target object has an acoustic impedance that is acoustically different from that of the medium. If it reflects or absorbs, the force by acoustic radiation pressure acts. As for the action range of the force, it is possible to apply the force at a minute interval on the order of half wavelength by forming a standing wave sound field. In addition, regarding the safety of the ultrasonic generator for the human body, since an ultrasonic wave is blocked if an air layer exists between the liquid medium and the human body, it is easy to consider the leakage of the ultrasonic wave.
[0005]
It has long been known that an object that is sufficiently small compared to the wavelength in a standing wave sound field (hereinafter referred to as a micro object) receives a force from the antinode of sound pressure toward a node. Since the nodes and antinodes of the sound pressure are alternately present in the sound wave propagation direction at quarter-wave intervals, the mechanical stable point at which the minute object is captured in the sound propagation direction is limited to a very small region. In addition, with respect to the vertical plane in the sound propagation direction, the force application range is distributed over a relatively wide area corresponding to the transducer area, and the minute object can freely move in the direction in which the medium flows.
[0006]
More specifically, as shown in FIG. 1, a standing wave sound field is placed between the ultrasonic transducer and the reflecting plate by placing the ultrasonic transducer and the reflecting plate in parallel and applying a voltage in water. Is generated. The generated standing wave sound field is limited to a minute region surrounded by the vibrator and the reflector, and in the standing wave sound field, as shown in FIG. A minute object floating alternately in the sound field receives a force from the sound pressure antinode to the node, and is captured by the sound pressure nodes existing at half-wavelength intervals. The standing wave sound field can be easily generated by installing the vibrator and the reflector in parallel.
[0007]
Techniques for manipulating minute objects in a non-contact manner are required in the fields of micromachines and biotechnology, for example. To exert a force in a non-contact, but studies using radiation pressure of electrostatic and laser light is performed a number, it is also possible to use an acoustic release morphism pressure of the ultrasonic waves. In a minute region, in order to avoid contamination with fine dust or the like, it is necessary to carry out in a sealed container if it is in a liquid. Since ultrasonic waves can exert a force from a distance if there is a propagating medium, it is considered that a force can be applied in a non-contact manner by irradiating an ultrasonic wave from the outside into a sealed container.
[0008]
The present inventor has so far worked on the realization of non-contact three-dimensional micromanipulation using ultrasonic acoustic radiation pressure for the purpose of manipulating individual particles floating in water. Clean non-contact micromanipulation technology is also required for body purification. In that case, it is necessary to continuously operate a group of particles flowing in a large amount in the pipeline. The present inventor made a prototype of a rectangular vibrator having a plurality of electrodes for the purpose of concentrating and filtering fine particles flowing in a fluid, and controlling the direction of flow of particles by changing the phase of a voltage applied between the electrodes. However, there was a problem that the moving speed did not follow the movement of the sound field. This is because, in the standing wave field by a plane wave, with respect to the propagation direction of the waves, the force acting in a direction perpendicular is considered weak. In order to apply a powerful force, the force acting from the antinode of the sound pressure toward the node should be used in the propagation direction of the sound wave.
[0009]
[Problems to be solved by the invention]
The inventor of the present invention uses a concave-type vibrator to place a reflector at the focal position of a standing wave sound field, and changes individual frequencies to capture the minute objects captured in the sound pressure node by changing the frequency. Results of an attempt to control the flow direction of particles by moving the particles in the direction of sound wave propagation by continuously changing the frequency while studying the method of moving in one dimension on the axis The present invention has been completed by successfully developing the manipulation of particles flowing in the fluid together with the medium.
That is, the problem to be solved by the present invention is to provide a non-contact filtering method and apparatus for performing a one-dimensional movement operation and concentrating minute objects captured in a node of sound pressure and arranged in layers. There is.
[0010]
[Means for Solving the Problems]
The present invention for solving the above-described problems comprises the following technical means.
(1) A non-contact filtering method using ultrasonic waves. 1) In a flow path filled with a liquid medium, a predetermined interval is maintained between the ultrasonic transducer and the reflector along the flow path. Installed in parallel, drives the ultrasonic transducer with a predetermined electrical signal, radiates the ultrasonic wave with the transducer, the reflected ultrasonic wave is reflected by the reflector and resonates between the transducer and the reflector The sound field of the standing wave is generated without taking into consideration the above, and the minute object dispersed in the liquid medium is captured at the node of the sound pressure of the standing wave field generated in the flow path or the antinode of the sound pressure, and 2 ) The wavelength of the sound wave emitted from the vibrator is controlled by changing the electrical signal applied to the ultrasonic vibrator, and the frequency of the ultrasonic wave applied to the ultrasonic vibrator is continuously increased or decreased from the initial value. , then, a predetermined reflector or transducer side by repeating the operation of returning to the initial value instantaneously Performs moving operation of attracting the position to change the trajectory of the minute object, captured in succession small objects aligned in layers, 3), characterized in that, taken out as a concentrate of micro-material in the medium is moved An ultrasonic non-contact filtering method.
(2) The ultrasonic non-contact filtering method according to (1), wherein the ultrasonic transducer is an elongated rectangle.
(3) The ultrasonic non-contact filtering method according to (2), wherein a standing wave is generated without considering resonance and frequency change is possible.
(4) The ultrasonic non-contact filtering method according to (1), wherein the micro object dispersed in the liquid medium is concentrated by continuously changing the trajectory of the captured object and passing through the flow path.
( 5 ) An apparatus used in the method according to (1), wherein an ultrasonic transducer and a reflector arranged in parallel with a predetermined distance on the wall surface of the flow path of the liquid medium, the ultrasonic vibration means for supplying a predetermined electric signal to the child, means for continuously controlling the frequency of the ultrasonic wave, saw including a micro-material in the above SL medium means for taking as a concentrate, as components, electrical supplies to the transducer By continuously increasing or decreasing the signal frequency and then repeatedly returning to the initial value instantaneously, the ultrasonic sound field is electrically controlled and the position of the node of the sound pressure is controlled. An ultrasonic non-contact filtering device characterized in that the minute objects in the medium collected on the reflecting plate or vibrator side, continuously captured and moved to a predetermined position are taken out as a concentrated liquid .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in more detail.
In the non-contact filtering method according to the present invention, an ultrasonic transducer and a reflector are arranged in parallel at a predetermined distance along a flow path in a liquid medium in which minute objects are dispersed and flowing, and the ultrasonic transducer is arranged in a predetermined manner. The small object in the medium is captured in the sound pressure node in the sound field in the generated standing wave sound field by driving with the electrical signal of Then, it is characterized in that these are concentrated by performing a moving operation in one dimension.
[0012]
Further, the non-contact filtering device according to the present invention provides an electrical signal to the ultrasonic transducer and the reflector, and the plurality of transducers arranged at predetermined intervals on the wall surface of the flow path of the liquid medium in which the minute object is dispersed. Means for continuously controlling the frequency of the ultrasonic wave, and means for taking out a minute object in the medium moved to a predetermined position as a concentrated liquid, using the emitted ultrasonic wave It is characterized in that a minute object in the medium is captured and concentrated in a node of sound pressure in the generated standing wave sound field.
[0013]
Hereinafter, the present invention will be described with reference to the drawings.
FIG. 3 is an explanatory diagram showing the principle and basic device of a non-contact filtering method using ultrasonic waves according to the present invention. An ultrasonic transducer and a reflecting plate are arranged in parallel at predetermined intervals on a wall surface in a flow path in which a large number of minute objects are dispersed and a floating liquid medium flows from top to bottom. When a predetermined electric signal is supplied to the ultrasonic vibrator, the vibrator emits ultrasonic waves, and a standing wave sound field is formed between the reflector and the reflector. A flat rectangular ultrasonic transducer is used as the ultrasonic transducer.
[0014]
In the present invention, as shown in the embodiments described later, a sine wave alternating current having a frequency of about 2.0 MHz is generated by a function generator, amplified by a power amplifier, supplied to an ultrasonic transducer, and formed standing wave sound. When a suspension of alumina particles having an average diameter of 16 μm was injected into the field from above using a pipette, it was confirmed that the alumina particles flowed down along the sound pressure node layer. Note that the nodes of sound pressure are generated at intervals of a half wavelength between the vibrator and the reflector.
[0015]
When the sound speed in water is 1500 m / s, the half wavelength in the case of 2.0 MHz is 0.375 mm. Therefore, the interval between the layers corresponds to the half wavelength, and it is trapped by the sound pressure node and flows down. I can say that. If a particle outlet is prepared under each layer of the sound pressure node, a high-density particle suspension can be collected. However, it is difficult to prepare an outlet for each layer. By the way, by changing the frequency of the electric signal supplied to the vibrator, the ultrasonic sound field can be electrically controlled and the position of the node of the sound pressure can be controlled. When the frequency is changed, the wavelength changes, and the interval between the nodes of the sound pressure changes, so that the captured particles can be moved.
[0016]
Therefore, as shown in the examples described later, next, the frequency of the ultrasonic wave is continuously changed from 1.9 MHz to 2.1 MHz, and thereafter, it is instantaneously returned to the initial value of 1.9 MHz. And produced a sound field. FIG. 5 is a photograph of the behavior of particles when alumina particles are introduced into the sound field from the upper left. It is confirmed that it flows from the upper left to the lower right. Since the particles have a specific gravity of 4, the particles settle down under their own weight in a situation where no force acts. However, since there is a standing wave due to ultrasonic waves, it is trapped in the node of sound pressure and aggregates in layers. Further, as the frequency changes, the interval between the nodes of the sound pressure changes, the node of the sound pressure in the center moves from left to right, and the captured particles also move to the right while sinking. .
[0017]
FIG. 6 shows the movement of the sound pressure node by calculation when the frequency changes. Compared to 1.9 MHz, there are three nodes of sound pressure because the wavelength is shorter at 2.1 MHz. Then, after changing the frequency continuously between 1.9 MHz and 2.1 MHz, the operation of returning from 2.1 MHz to 1.9 MHz instantaneously is performed once, so that three sound pressure nodes are reflected on the reflector. Move towards By repeating this operation at a high speed, all particles can be collected in the vicinity of the reflector, and if a take-out port is provided in the vicinity of the reflector, a high-concentration suspension can be collected. That is, concentration of the suspension can be realized. Conversely, if the frequency is continuously decreased from 2.1 MHz to 1.9 MHz and the operation is instantaneously returned to 2.1 MHz, particles can be collected on the vibrator side contrary to what has been shown so far. .
[0018]
In the present invention, the minute object is applicable to any kind of object as long as it is a sufficiently small object compared to the wavelength in standing wave sound waves. In the present invention, the type, form and installation method of the ultrasonic transducer and reflector, the means for supplying the electrical signal of the transducer, the means for continuously controlling the frequency of the ultrasonic wave, and the minute object in the medium The means for taking out the concentrate as a concentrated solution is not particularly limited, and the specific configuration thereof can be appropriately designed according to the purpose of use. Further, the various conditions in the above method are not particularly limited, and can be arbitrarily changed according to the purpose of use.
[0019]
【Example】
EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by the following Examples.
Example 1
In this example, a suspension of fine particles was put into a sound field, and an attempt was made to concentrate the particles using the acoustic radiation pressure of ultrasonic waves. A rectangular transducer was used to generate a uniform sound field over a long distance along the channel. Then, by emitting ultrasonic waves, generating a standing wave between the reflector and changing the frequency, the captured particles are moved on the sound axis, and the particles passing through the sound field are attracted to one side. Tried.
[0020]
(1) Apparatus and method of operation The vibrator is made of ceramics and has a 40 × 22 mm rectangle, a resonance frequency of 2.0 MHz, and a back electrode of 40 × 6 mm. In addition, a part of the front surface electrode in contact with the medium water was folded back and the lead wires of both electrodes were drawn from the back surface. In order to insulate the back electrode and fix the vibrator, the vibrator was fixed to an acrylic frame with silicon rubber. A sine wave signal of about 2 MHz generated by a function generator (NF circuit design block, 1946, hereinafter abbreviated as FG) is amplified by an amplifier (ENI, 325LA) and applied to the vibrator. A vibrator is fixed in parallel to the glass wall surface (thickness 3 mm) at a distance of 10 mm in a glass water tank filled with water, and a standing wave sound field is generated between the wall surface. Then, alumina particles (average diameter 16 μm, specific gravity 4) were introduced as suspension from above, and the behavior when flowing down under its own weight was photographed with a CCD camera and observed. Since particles are distributed also in the depth direction, only a vertical surface of the portion where the back electrode of the vibrator is applied is observed using a sheet-like slit light having a width of about 5 mm as illumination. In order to observe the behavior of particles, the shutter of the CCD camera was set to 1/1000 s.
[0021]
(2) Filtering method and result When a sound field was generated by applying a voltage to the vibrator and alumina particles were introduced from above, it was observed that the particles flowed down in layers. FIG. 4 is a photograph of the behavior of particles at a frequency of 2.0 MHz. It is confirmed that the sound waves fall down in a layered manner at equal intervals corresponding to the half wavelength (0.375 mm) of the sound wave. Since the specific gravity of the alumina particles is about 4, large particles settle immediately after charging, but small particles float in water for a while and then sink. The small particles are thought to be trapped in the sound pressure node. If the standing wave is an ideal plane wave, a uniform sound field is generated and no force is generated in the direction of gravity. However, in this embodiment, since it is a standing wave by a flat sound source with a finite size, non-uniformity occurs in the layer of the sound pressure node, and thus force acts also in the direction of gravity and particles are trapped. It is thought. Note that the distance between the vibrator and the reflecting plate is 10 mm, and it is considered that a standing wave is generated in the near field.
[0022]
Next, in order to control the flowing particles, an attempt was made to change the frequency applied to the sound source by controlling the FG in the sweep mode. Since it is desirable to drive the vibrator at the resonance frequency, the vibration is changed by about 10% near the resonance frequency, and is changed between 1.9 and 2.1 MHz. Moreover, after continuously changing the frequency linearly, the frequency was returned to the initial frequency and continuously changed again. By doing so, it becomes possible to continue changing the frequency continuously in the same direction, although it becomes partially discontinuous. A schematic diagram of particle movement is shown in FIG. By continuously changing the frequency from f = f _min → f _min + Δf → f _max , the interval between the nodes of the sound pressure is gradually narrowed, and particles captured at the same time are also (a) → (b) → ( c) and move. Then, when f = f _max is reached, when f = f _min is instantaneously returned, the particles trapped in the sound pressure node move to the nearest sound pressure node as shown in (c) → (d). Will do. As is clear from comparison between (a) and (d) having the same frequency, it can be seen that the particles have moved to the right sound pressure node in this series of operations.
[0023]
Regarding the timing of the frequency change performed in this example, the operation of linearly increasing the frequency f from 1.9 MHz to 2.1 MHz and then instantaneously returning it to 1.9 MHz was repeated at 50 ms intervals. FIG. 5 is a photograph showing an example of the experimental results. Suspension is introduced from the upper left pipette. It can be seen that the particles are moving from left to right at the same time as they flow down under their own weight. Also, it is unclear how many frequencies in this range are from 1.9 to 2.1 MHz, but they are trapped in the sound pressure section because they are striped at equal intervals corresponding to half-wavelength intervals. It is confirmed that Eventually, it was confirmed by experiments that particles gathered in a layer of two or three sound pressure nodes at the right end. On the other hand, as a result of reducing the frequency from 2.1 to 1.9 MHz, it was confirmed that the wavelength was shortened, and the movement from the right to the left was confirmed. That is, the particles can be moved to the right by increasing the frequency, and the particles can be moved to the left by decreasing the frequency, and the suspension can be concentrated.
[0024]
In addition, changing the frequency continuously at high speed was realized using the sweep mode of FG. Since this is an FG composed of a digital circuit, strictly speaking, the frequency changes stepwise every 200 μs. That is, since the frequency is changed from 1.9 to 2.1 MHz during this 50 ms, the frequency changes by 0.0008 MHz every 200 μs.
[0025]
In the above method, the vibrator applied voltage was about 10 to 50 Vpp. This is because the output of the FG is constant, but changes due to load fluctuations. The distance between the vibrator and the reflector is 10 mm so that the entire distance from the vibrator to the reflector can be observed and the distance between the nodes of the sound pressure can be observed in detail, but is not limited to 10 mm. , 20 mm, and 30 mm, similar results were obtained. Although the time for changing the frequency is shown for 0.05 s in the above, the experiment was conducted for 0.1 s, 0.2 s, 0.5 s, and 1.0 s. The particle flow trajectory became a vertical flow (Fig. 8).
[0026]
【The invention's effect】
As described above, the present invention relates to a non-contact filtering method and apparatus using ultrasonic waves. According to the present invention, 1) a micro object is captured in a liquid medium in a non-contact manner, and a sound pressure is obtained. 2) The sound pressure node can be moved by changing the frequency, and the minute object can pass through the end in the flow path. After the frequency is continuously changed, the minute object can be concentrated by repeatedly performing the operation of instantaneously returning the initial value to the initial value.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of the distribution of sound pressure nodes when a vibrator and a reflector are arranged in parallel.
FIG. 2 is an explanatory diagram showing the movement of particles captured in a node of sound pressure when the frequency changes.
FIG. 3 is an explanatory diagram of an example of a filtering device.
FIG. 4 shows alumina particles trapped in a sound pressure node layer and flowing down in layers.
FIG. 5 shows alumina particles that move to the right with frequency changes.
FIG. 6 shows the movement of a node of sound pressure when the frequency changes.
FIG. 7 is an explanatory diagram of particle movement due to frequency change.
FIG. 8 shows a particle flow trajectory when the frequency velocity is changed.

Claims (5)

A non-contact filtering method using ultrasonic waves, wherein (1) in a flow path filled with a liquid medium, an ultrasonic transducer and a reflector are parallel to each other along the flow path at a predetermined interval. Installed, drives the ultrasonic transducer with a predetermined electrical signal, radiates ultrasonic waves with the transducer, the reflected ultrasonic waves are reflected by the reflector, and resonance is considered between the transducer and the reflector Without generating a standing wave sound field, and capturing a minute object dispersed in the liquid medium at the node of the sound pressure of the standing wave sound field generated in the flow path or the antinode of the sound pressure, (2) By controlling the wavelength of the sound wave emitted from the vibrator by changing the electrical signal applied to the ultrasonic vibrator , the frequency of the ultrasonic wave applied to the ultrasonic vibrator is continuously increased or decreased from the initial value , then, instantaneously predetermined reflector or transducer side by repeating the operation of returning to the initial value By changing the trajectory of the minute object, captured successively collected on location performs moving operation of the micro-objects aligned in layers, and to retrieve the minute object in the medium is moved (3) as a concentrate An ultrasonic non-contact filtering method.   2. The ultrasonic non-contact filtering method according to claim 1, wherein the ultrasonic transducer is an elongated rectangle.   The ultrasonic non-contact filtering method according to claim 2, wherein a standing wave is generated without considering resonance and frequency change is possible.   The ultrasonic non-contact filtering method according to claim 1, wherein the micro object dispersed in the liquid medium is concentrated by continuously changing the trajectory of the captured object and passing through the flow path. An apparatus for use in the method according to claim 1, wherein an ultrasonic transducer and a reflector arranged in parallel with a predetermined interval on a wall surface of the flow path of the liquid medium, It means for supplying an electrical signal, means for continuously controlling the frequency of the ultrasonic wave, means for extracting the minute object in the above SL medium as concentrates, see containing as components, the frequency of the electrical signal supplied to the transducer By continuously increasing or decreasing, and then repeatedly performing the operation of instantaneously returning to the initial value, the ultrasonic sound field is electrically controlled, and the position of the sound pressure node is controlled by controlling the position of the reflector or An ultrasonic non-contact filtering apparatus characterized in that a minute object in the medium collected on the vibrator side, continuously captured and moved to a predetermined position is taken out as a concentrated liquid .

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