JP2803163B2 - Infusion pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infusion pump for supplying a liquid, particularly a chemical solution, in small amounts and with high precision, and more particularly to an infusion pump using an electrochemical method. is there.

2. Description of the Related Art In recent years, various infusion pumps have been used to inject a small amount of a drug solution into a human body with high accuracy.

Conventional infusion pumps are classified into four types: syringe pumps, beristaltic (rotor type) pumps, finger pumps, and bellows pumps, depending on the type of the infusion pump. Of these, those other than the bellows pump use a motor such as a stepping motor, a rotary solenoid motor, or a DC motor as a drive source for pushing out the chemical solution, and employ a complicated control mechanism for the discharge amount of the chemical solution. As a result, their weight and size are generally too large, and because of their high cost they are commonly used at hospital bedsides, making them unsuitable for portable or disposable use. In addition, the bellows pump uses a vaporization pressure of the freon gas to press the bellows, thereby discharging the chemical solution.However, it is difficult to control the vaporization pressure of the freon gas. In the case of injection, there is a problem in the injection accuracy.

On the other hand, in recent years, an electrochemical infusion pump has been proposed as a new system. (H, J, R, Mugget, U.S. Pat.
522,698). This electrochemical infusion pump supplies hydrogen to the anode of an electrochemical cell in which a porous gas diffusion electrode is joined to both sides of a water-containing ion exchange membrane that functions as an electrolyte, and a direct current flows between the positive and negative electrodes. It utilizes the following electrochemical reaction that occurs when the reaction occurs.

^{_{Anode: H 2 → 2H + + 2e}} - (1) ^{cathode: 2H + + 2e - → H} 2 (2) i.e., providing each sealed gas chamber on the back of the anode and the cathode, the anode gas chamber becomes vacuum, The cathode gas chamber is pressurized. That is, this electrochemical cell has both a pressure reducing mechanism and a pressure increasing mechanism. Accordingly, if the polarity of the electrochemical cell is alternately reversed, one of the electrodes becomes an anode or a cathode, and at the same time, the other gas chamber becomes a depressurized state or a pressurized state. Then, if a piston is attached to the tip of one of the gas chambers, the piston moves back and forth by repeating decompression and pressurization of the gas chamber, and if the tip of the piston is connected to the liquid reservoir, when the piston retreats The liquid is sucked, and the liquid is discharged when the piston advances.

It is also possible to use oxygen or air instead of hydrogen as the reaction gas of this electrochemical cell. In this case, anode: 2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ (3) Cathode: O ₂ ^{+ 4H + + 4e - → 2H} 2 O (4) made reaction occurs.

In any case, these electrochemical infusion pumps can control gas pressure and the amount of movement (from one electrode side to the other electrode side) very precisely by the current value flowing through the electrochemical cell, and in general, Since it is small in size and uses a battery as a power source, it is particularly excellent as a portable type.

When hydrogen is used as a gas in the above-described system, 420 ml of hydrogen is transferred in terms of 0 ° C. and 1 atm per 1 Ah, and 210 ml is transferred in the case of oxygen.

The critical problem of the infusion pump proposed in the above mentioned U.S. patent is that one electrode of the electrochemical cell can be operated as both an anode and a cathode by alternately reversing the polarity. It is in the point. That is, in a reaction system in which the above-mentioned gas is electrochemically transferred from one electrode side to the other electrode side, a gas-consuming electrode (an anode when hydrogen is used as a reactant, and a cathode when oxygen is used). ) A reaction and an electrode that generates gas (a cathode when using hydrogen, an anode when using oxygen) occur, but the forms of both reactions are essentially different, and the optimal material for one electrode is And it is difficult to balance the structure and the material and structure that are optimal for the other electrode,
If one electrode is to be provided with both gas-consuming and gas-generating functions, one encounters the problem of having to sacrifice either a successful reaction or a longevity.

Means for Solving the Problems The present invention prepares two sets of electrochemical cells each including an electrode intended only for a gas consumption reaction and an electrode intended only for a gas generation reaction. The above-described problem is not solved by providing only the pressurizing function and providing only the other set with the depressurizing function.

The hydrogen consumption reaction according to the above equation (1) or (4)
The electrode most suitable for the oxygen consumption reaction according to the formula is called a gas diffusion electrode, and is usually manufactured by binding with a catalyst powder and a water-repellent binder such as fluororesin. This is because the gas consumption reaction occurs at the contact point between the electrode and the gas and the hydrated ion exchange group, so that the electrode needs to have appropriate hydrophilicity and appropriate water repellency. In addition, a binder is indispensable for bonding an electrode to an ion exchange membrane as an electrolyte. As the catalyst powder, a powder of a platinum group metal or a powder obtained by supporting a platinum group metal on carbon powder for the hydrogen consumption reaction according to the formula (1) is preferable. Catalysts suitable for hydrogen consumption are also used, but other metals such as carbon, porphyrin, lanthanum strontium cobaltite (La _1-
xSrxCoO ₃ ) is also suitable. However, when carbon is used, it is essential to mix an ion exchange resin in the electrode.

On the other hand, an electrode suitable for the reaction for generating hydrogen according to the above-mentioned formula (2) or the reaction for generating oxygen according to the above-mentioned formula (3) is made of a platinum group metal used in a form integrally joined to an ion exchange membrane by a so-called electroless plating method. Or a screen metal electrode (net-like or expanded metal) having an opening.

In the case of the gas generating electrode, as in the case of the gas diffusion electrode described above, the reaction site is not delicate, and the reaction occurs only at the contact point between the ion exchange membrane and the electrode, so that not only water repellency is not particularly required, When attempting to impregnate the ion exchange membrane with water from the pores or openings of the gas generating electrode, the water repellency of the electrode is rather an obstacle.

The use of the same material and structure for both the cathode and anode of an electrochemical cell, as in the aforementioned U.S. Pat. For example, when an electrode optimal for the gas consumption reaction as described above is used, firstly, it is difficult for water to permeate the ion exchange membrane due to its high water repellency, and conversely, during operation of the electrochemical cell. In addition, there is a problem that the conductivity of the ion-exchange membrane is inferior because water is easily evaporated.
In addition, the polarity is alternately reversed to make a gas consuming electrode,
While being used as a gas generating electrode, the gas generated at the interface between the electrode and the ion-exchange membrane is likely to be separated from the ion-exchange membrane due to the gas generated at the interface between the electrode and the ion-exchange membrane. If used, the life is shortened due to the oxidation of the electrode during the gas generation reaction process (this tendency is particularly remarkable when carbon powder is used as the electrode material).

In addition, when the electrodes optimal for the gas generation reaction as described above are used for both the cathode and the anode, the gas consumption reaction does not proceed at all, or even if it proceeds, the reaction speed is extremely slow. In other words, since the operating current density must be reduced, the electrode area must be increased accordingly.

As described in detail above, there is too much problem in creating a depressurized state and a pressurized state by periodically inverting the polarity in one electrochemical cell as in the conventional method.

The above-mentioned U.S. Patent also describes the use of a plurality of electrochemical cells, but this is to increase the amount of movement of the electrochemical gas, and the operation of periodically inverting the polarity is performed. There is no difference in adopting the method.

On the other hand, as in the present invention, first, the electrochemical cell is composed of an electrode suitable for a gas consuming reaction and an electrode suitable for a gas generating reaction, and two such electrochemical cells are prepared. Without reversing any polarity, if one set of them is used only for the pressurizing system for moving the piston forward and the other set is used only for the depressurizing system for moving the piston backward, gas The chemical transfer reaction is fast enough, so that even with two sets of electrochemical cells, the infusion pump is smaller and the life of the electrochemical cells is smaller than when the polarity is reversed by one set of electrochemical cells. Is also long enough.

In the infusion pump of the present invention, the gas generating electrode chamber of the first electrochemical cell section, the gas diffusion electrode chamber of the second electrochemical cell section, and the gas chamber of the piston type infusion means communicate with each other. In addition, the gas diffusion electrode chamber of the first electrochemical cell section and the second
It is better to provide a bellows as a gas pressure buffer in the chamber formed from the gas generating electrode chamber of the electrochemical cell unit, but it may not be necessary in some cases. On the other hand, when air is used as the reactant, the cathode side of the electrochemical cell for pressurization is opened to the atmosphere, the anode side of the electrochemical cell for depressurization is opened to the atmosphere, and oxygen generated from the anode is released. May be released to the atmosphere.

In addition, the electrochemical cell section and the injection cylinder section including the piston may be integrated, or may be separated when the infusion pump is not used, and may be configured to be combined when used.

Embodiment 1 FIG. 1 shows a sectional structure of an electrochemical infusion pump using hydrogen as a reactant according to a first embodiment of the present invention.

The infusion pump can be roughly divided into the first electrochemical cell unit 1, the second
It is composed of an electrochemical cell part 2, a syringe barrel part 3, a liquid reservoir 4, and a bellows 5.

The first electrochemical cell unit 1 includes a first cell frame 6, a first cell body 7, a gas generating electrode chamber 41, and a first inlet 8 for hydrogen and water.
Further, the first cell main body 7 includes an anode 9, an ion exchange membrane 10, and a cathode 11. The second electrochemical cell unit 2 includes a second cell frame 12, a second cell body 13, a gas diffusion electrode chamber 42, and a second inlet 14 for hydrogen and water. The configuration is exactly the same as that of the cell main body 7, that is, it comprises an anode 9 ', an ion exchange membrane 10' and a cathode 11 '.

The injection tube part 3 includes an outer tube 15, an inner tube 16, a discharge port 17, and a liquid injection valve 18. Liquid is stored in the liquid reservoir 4, and is connected to the syringe barrel 3 via a liquid reservoir valve 19. The gas generating electrode chamber of the first electrochemical cell section, the gas diffusion electrode chamber of the second electrochemical cell section, and the gas chamber of the piston-type infusion means communicate with each other and are filled with hydrogen. I have.
A bellows 5 is attached to a chamber formed from the gas diffusion electrode chamber of the first electrochemical cell section and the gas generating electrode chamber of the second electrochemical cell section, and is filled with hydrogen.

The first cell body 7 and the second cell body 13 are manufactured as follows. That is, first, on one side of the ion exchange membranes 10 and 10 'made of perfluorocarbon sulfonic acid,
Cathode 11,1 made of platinum by so-called electroless plating
1 'is joined, and then a mixture of activated carbon powder carrying 10% platinum on the other side, a polytetrafluoroethylene as a binder, a lower aliphatic alcohol of perfluorocarbonsulfonic acid, and a mixed solvent solution of water is used. The anodes 9, 9 'are joined by hot pressing.

The electrochemical infusion pump having such a structure operates as follows. That is, first, the first electrochemical cell unit 1
Hydrogen and water are injected from the first injection port 8 of the first embodiment and the second injection port 14 of the second electrochemical cell unit 2, and the respective injection ports are closed. By this operation, the gas generating electrode chamber of the first electrochemical cell unit, the gas diffusion electrode chamber of the second electrochemical cell unit, and the gas chamber of the piston type infusion means which are communicated with each other are filled with hydrogen.
Further, a chamber formed from the gas diffusion electrode chamber of the first electrochemical cell section and the gas generation electrode chamber of the second electrochemical cell section is also filled with hydrogen. Cathode in which water is porous and hydrophilic
It permeates the ion exchange membranes 10 and 10 'through the pores of 11 and 11'.

Next, when a direct current is applied between the anode 9 and the cathode 11 of the first electrochemical cell unit 1 (while the second electrochemical cell unit 2 is not energized during this time), the back surface of the anode 9 (see FIG. left)
At the same time as the hydrogen is consumed, hydrogen is generated from the cathode 11, pressurized and pushes the piston 16, and the liquid in the syringe barrel 3 is discharged from the discharge port 17 through the injection valve 18. During this time, the pressure on the back side of the anode 9 is reduced, and the bellows 5 shrinks.

Next, when the power supply to the first electrochemical cell unit 1 is stopped and a direct current is applied between the anode 9 'and the cathode 11' of the second electrochemical cell unit 2, hydrogen is supplied to the anode 9 '. It is consumed and hydrogen is generated at the cathode 11 '. That is, the pressure of hydrogen on the back surface of the anode 9 ′ (right side in the figure) decreases, the piston 16 moves backward (moves to the left side in the figure), and the liquid reservoir valve 19 opens (in the meantime, the liquid injection valve 18 (Closed), the liquid in the liquid reservoir 4 is sucked into the syringe barrel 3. Also, during this time,
The system on the back side of the cathode 11 'is pressurized, and the bellows 5 expands.

Thus, the first electrochemical cell part 1 is used only for moving the piston 16 forward, and the second electrochemical cell part 2 is used only for moving the piston 16 backward. These operations may be performed only once or may be repeated.

Example 2 In Example 1, the first electrochemical cell unit 1 and the second
When injecting oxygen instead of injecting hydrogen into the electrochemical cell section 2 and using the anodes 9, 9 'as cathodes and the cathodes 11, 11' as anodes, an infusion pump using oxygen as a reactant is obtained.

Embodiment 3 FIG. 2 shows a sectional structure of an electrochemical cell part of an electrochemical infusion pump using air as a reactant according to a third embodiment of the present invention.

The electrochemical cell section includes a first electrochemical cell 20 and a second electrochemical cell 21.

The first electrochemical cell 20 includes a first cell frame 22 and a first cell body.
23, an air inlet 24, and a first inlet 25.
The cell body 23 is composed of a cathode 26 made of exactly the same material and structure as the anode described in the first embodiment, an ion exchange membrane 27, and an anode 28 of expanded titanium plated with platinum.

The second electrochemical cell 21 includes a second cell frame 29 and a second cell body.
30, an oxygen discharge port 31, and a second injection port 32.
The cell body 30 includes a cathode 26 ', an ion exchange membrane 27', and an anode 28 ', which are completely the same as the first cell body 23.

The gas diffusion electrode chamber 43 of the first electrochemical cell section 20, the gas generating electrode chamber 44 of the second electrochemical cell section, and the gas chamber (not shown) of the piston type infusion means are in communication.

The operation of this electrochemical cell is performed as follows. That is, first, water is injected from the first water inlet 25 and the twenty-second water inlet 32, respectively, and then closed. Next, when a direct current is applied between the cathode 26 and the anode 28 of the first electrochemical cell 20, oxygen in the air introduced from the air inlet 24 is
It is consumed at 26 and oxygen is generated at the anode 28. This oxygen advances the piston of the syringe barrel (connected to the right side of the figure). During this time, the operation of the second electrochemical cell 21 is stopped. Next, when the first electrochemical cell 20 is stopped and a direct current is supplied to the second electrochemical cell 21, oxygen on the back (right side) of the cathode 26 'is consumed by the cathode 26' for the consumption reaction, and the cathode 2 '
The system on the back side of 6 'is depressurized, and the piston is retracted. During this time, pure oxygen generated from the anode 28 'is released to the atmosphere via the oxygen outlet 31. Therefore, in this case, the bellows as described in the first embodiment becomes unnecessary.

Effect The infusion pump obtained in Example 1 was designated as A, and in Example 1, the electrochemical cell part was made into one set, the anode was also an electrode made of the same material and structure as the cathode, and one electrochemical cell was used. B is a conventional infusion pump in which the polarity is periodically inverted, and in Example 1, the cathode is also an electrode made of the same material and structure as the anode, and the polarity is periodically inverted in one electrochemical cell. The infusion pump A was repeatedly tested for forward and backward movement of the piston with each infusion pump assuming that the conventional infusion pump was C, and the infusion pump A was able to discharge the liquid (water) even after repeating 1000 times. In the case of infusion pump B,
The liquid was not discharged at 0 times, and in the case of the infusion pump C, the piston could not be advanced even once. In the case of the infusion pump B, when the disassembly inspection was performed after the liquid stopped being discharged, the cathode was separated from the ion exchange membrane. The reason why the infusion pump C did not operate at all was that the anode in which platinum was electrolessly plated on the ion exchange membrane was ineffective for the hydrogen consumption reaction.

On the other hand, the infusion pump obtained in Example 2 was designated as D, and in Example 2, the anode was also an electrode made of the same material and structure as the cathode, and a pressurized and depressurized state was created with one electrochemical cell. A conventional infusion pump was designated as E, and the same test was performed as in the case of hydrogen described above.
In the case of D, no abnormality was found even after repeated tests 1000 times, whereas in the case of E, the liquid stopped discharging after 12 times, and the disassembly inspection showed that the anode carbon was strongly corroded. I was

As described above in detail, it is clear that the infusion pump of the present invention shows superior performance as compared with the conventional type.

[Brief description of the drawings]

FIG. 1 shows a cross-sectional structure of an infusion pump according to a first embodiment of the present invention, and FIG. 2 shows a cross-sectional structure of an electrochemical cell part of an infusion pump according to a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... 1st electrochemical cell part 2 ... 2nd electrochemical cell part 3 ... Syringe part 4 ... Liquid reservoir 5 ... Bellows 20 ... 1st electrochemical cell 21 ... 2nd electrochemical cell 24 …… Air inlet, 31… Pure oxygen outlet

Claims (1)

(57) [Claims] A first electrochemical cell, a second electrochemical cell, and a piston type infusion means, wherein the first electrochemical cell comprises a gas diffusion electrode, an electrolyte comprising an ion exchange membrane, and a gas generating electrode. A cell body, a cell frame, and a gas generating electrode chamber, and a second electrochemical cell comprises a cell body, a cell frame, and a gas comprising an electrolyte comprising a gas diffusion electrode and an ion exchange membrane, and a gas generating electrode. A piston-type infusion means having a gas chamber and a liquid chamber separated by a piston, wherein the gas generation electrode chamber, the gas diffusion electrode chamber, and the gas chamber communicate with each other; When the gas chamber is pressurized by the gas generated by the operation of the cell, the piston moves to the liquid chamber side, and when the gas chamber is depressurized by the operation of the second electrochemical cell, the piston moves to the liquid chamber side. Do Infusion pump according to claim.