1. Field of the Invention
The present invention relates to a device utilized at the time of mixing together trace amounts of gases, trace amounts of liquids, or trace amounts of gas and liquid and observing a mixed state or a combined state of the resultant mixture.
2. Description of the Related Art
Recent progress in nanotechnology and ultramicro processing techniques is remarkable, and combination of these technologies is henceforth expected to evolve into various applications.
A technology pertaining to a micro-electromechanical system (MEMS) into which a semiconductor chip and a microactuator are assembled; that is, a so-called micromachine, gains attention as one of such merged technologies. This MEMS technology is for packaging, in a chip measuring millimeters per side, an LSI and an actuator which performs actual work. Combination of a microhydraulic circuit and an LSI circuit is expected to yield another amalgam.
Such a conventional chip, or the like, is a mere incorporation, on a substrate in an easily-mountable arrangement, of a micropump, channels thereof, sensors, microvalves, and an LSI circuit to be used for activating them. In other words, the chip is to be discarded after a single use. The channels have flow passages which are essentially on the order of micrometers to hundreds of micrometers. The micropump is basically influenced by the size of the flow passages. Accordingly, the micropump must assume a ultrafine structure isolated from the structure of an ordinary pump. Further, the micropump must be slim so as to be mounted on a chip. Although the micropump is ultra small, the pump must have superior transfer ability and responsiveness. If control of the micropump is neither easy nor accurate, the pump cannot be used as an element for the hydraulic circuit. Moreover, a high sealing characteristic must be maintained before, during, and after mounting of the micropump, and the micropump must be easy to assemble.
For these reasons, a pump using a piezoelectric element has been proposed as such a micropump, and a method for manufacturing the pump has also been proposed (see JP-A-5-306683).
FIG. 27 is a block diagram of the conventional micropump. In FIG. 27, reference numeral 401 designates a silicon substrate; 402 designates a thermal oxide film; 403, 404 designate glass substrates; 405 designates a piezoelectric element; 406 designates a pipe; 407 designates a thin layer of sodium chloride; and 408 designates influent fluid.
This micropump has a structure embodied by sandwiching the silicon substrate 401 between the glass substrates 403, 404 or the like, wherein a diaphragm, flow passages, and a valve section are fabricated on the silicon substrate 401. Improvements in priming and debubbling characteristics of liquid and continuation of stable action after lapse of time must be attained. For these reasons, after fabrication of the micropump, liquid containing at least one kind of water-soluble salt or polyhydric alcohol is injected into the pump, and the pump is then dried in order to cause the substances to adhere to an interior surface of the micropump. The water-soluble salts or polyhydric alcohols adhering to the interior surface portion have wettability against a water solution, and hence inflow of liquid into the pump can be performed with considerable ease, thereby improving the ability to discharge bubbles.
However, the micropump performs a pumping action by means of actuating the minute diaphragm formed in the silicon substrate 401 through use of the micro-piezoelectric element 405. Hence, there are achieved only a small pumping characteristic, a low delivery pressure, and low discharge capacity. The piezoelectric element 405 is mounted on the silicon substrate 401. If liquid to be ejected is changed while such a pump having a fine and complicated structure is used, the entire micropump must be discarded, because cleansing of the inside of the pump is not easy, and would incur high running costs.
The size of the micropump is also basically dominated by the size of the piezoelectric element. An attempt to increase the stroke of the diaphragm through use of a piezoelectric element also encounters a limitation. Increasing the delivery pressure and the discharge capacity requires another drive source. For this reason, attention has been paid to an electrochemical-cell-drive pump which generates a gas by means of electrochemical reaction (see JP-A-8-295400).
FIG. 28 is a block diagram of a conventional electrochemical-cell-drive pump.
In FIG. 28, reference numeral 511 designates a first sheet; 512 designates a second sheet; 513 designates a third sheet; 514 designates a first chamber; 515 designates a second chamber; 516 designates fluid stored in the first chamber 514; 517 designates a fluid supply port attached to the first chamber 514; 518 designates a gas inlet pipe attached to the second chamber 515; 519 designates an electrochemical cell; 520 designates a power source; and 521 designates a switch.
This conventional electrochemical-cell-drive pump is constituted of a bag-shaped member and the electrochemical cell 519, wherein the bag-shaped member is constituted of three sheets; that is, the first sheet 511, the second sheet 512, and the third sheet 513. The first sheet 511 is given rubber elastic stress larger than that of the third sheet 513, and the third sheet 513 is given rubber elastic stress larger than that of the second sheet 512. The first sheet 511 and the second sheet 512 constitute the first chamber 514 serving as a fluid storage section, and the second sheet 512 and the third sheet 513 constitute the second chamber 515 serving as a gas pressurizing section. The first chamber 514 is equipped with the fluid ejection port 517. A gas produced as a result of application of a d.c. current to the electrochemical cell 519 is introduced into the second chamber 515, thereby discharging fluid from the fluid ejection port 517.
The conventional electrochemical-cell-drive pump provides a compact, lightweight fluid supply device having superior usability and operability. However, the conventional electrochemical-cell-drive pump basically fails to have a structure suitable for mounting the pump on a chip. Hence, adoption of this electrochemical-cell-drive pump as a micropump is difficult.
In addition to the pump, a microreactor chip for chemosynthesis purpose has also been proposed heretofore (see JP-A-2002-27984). FIG. 29 is a block diagram of a conventional microreactor chip for chemosynthesis.
In FIG. 29, reference numeral 630 designates a microreactor chip for chemosynthesis; 631 designates a chip substrate; 631a designates a surface layer; 632 designates a thin film member; 633 designates an aperture section; and 634 designates a flow passage.
The chip substrate 631 constituting the conventional microreactor chip 630 for chemosynthesis is formed from material to be readily processed. However, the surface layer 631a, whose material does not cause chemical reaction with a sample flowing through the flow passage 634, is formed over the surface of the chip substrate 631 on which the thin film member 632 is to be affixed (i.e., the surface which comes into contact with a sample) so as to avoid exertion of an influence on synthetic reaction. The thin film member 632 is set to the same plane size as that of the chip substrate 631, and the thickness of the thin film member 632 is set within the range of 3 μm to 500 μm. Further, one surface of the thin film member 632 is coated with an adhesive, and the thus-coated surface of the thin film member 632 is affixed to the chip substrate 631. The aperture section 633 is formed so as to penetrate through the thin film member 632, by means of laser processing or punching.