Patent Application
20060166373
1. Field of the Invention
The present invention relates to a chemical analysis apparatus and a chemical analysis device for analyzing a sample, and in particular to a chemical analysis apparatus and a chemical analysis device for processing a sample and a reagent in utilization of Electro-wetting phenomenon.
2. Description of the Related Art
Medical or experimental automated analysis apparatuses which are used widely at present, have to have a complicated system incorporating therein many mechanisms, and accordingly, they have limits to miniaturization and lowing of costs thereof.
Meanwhile, in a flow-type μ-TAS analysis device, a reagent is fed into chips from a plurality of inlets of analysis devices while a sample is fed into the chips, the reagent and the sample continuously flowing through passages in the analyzing device so as to be mixed with each other on the passage's way, and thus, an optical absorbance or the like of the thus obtained mixture is detected by a detector. Thus, a rotary mechanism and an agitating mechanism are not required so that the configuration thereof can be simplified.
However, the passages have to be flushed, resulting in a serious problem of contamination. Further, due to feed and replacement of several kinds of liquid, the provision of pumps and valves are required for the respective kinds of liquid, and accordingly, these devices have to use a system which is practically difficult in view of its reliability and costs. Accordingly, in the current flow type u-TAS analysis device, a number of inspection items for one chip is small, and liquid drive means such as the pumps or the like are provided outside of the device. Thus, the medical analysis apparatus or the like cannot satisfy the requirements of cost reduction.
For example, WO 2004/030820 A2 discloses a method in which a voltage is applied to electrodes provided in an analysis device so as to change the electric wettability EWOD (ElectroWetting On Dielectric), and thereby, displacing a liquid drop. Variation in EWOD is a phenomenon caused by variation in the surface tension or interfacial tension. With the use of the EWOD as stated above, the analysis device has a structure and a mechanism which are greatly simplified.
However, the example disclosed in the WO 2004/030820 A2 can hardly pipette a sample and a reagent, accurately by predetermined quantities, and accordingly, cannot carry out various processes in order to inspect the sample by an inspection unit.
An object of the present invention is to provide a system which can accurately pipette a predetermined amount of a sample and a reagent so as to carry out various processes in order to inspect the sample by an inspection unit
To the end, according to the present invention, there is provided an analysis apparatus that comprises a common electrode formed on an upper board and drive electrodes including a train of plural electrodes formed on a lower board. Oil is filled into a space between the two boards, in which liquid drops of a sample, a reagent or the like are made to be formed, and the common electrode is applied thereto with a negative voltage or is grounded while a positive voltage is applied to an electrode on the drive electrode side. Thus, there is decreased an contact angle of the oil in a zone where the voltage is applied, resulting in an increase in the wettability, and thereby, it is possible to displace the liquid drops.
The drive electrodes comprises circular electrodes, including a train of electrodes arranged along a passage for the liquid drops, and electrodes arranged on both sides of the train, and the adjacent electrodes are formed to be overlapped with each other. Thus, predetermined amounts of the liquid drops of the sample and the reagent are pipetted, and are displaced and mixed. The thus obtained reacted solution is displaced along a predetermined path.
According to the invention, the predetermined amount of the sample and the reagent can be pipetted accurately so as to carry out various processes, thereby it is possible to inspect the sample by an inspection unit.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.
Explanation will be hereinbelow made of an embodiment according to the present invention with reference to
The sample pipetting portion comprises nozzle 61 extended vertically, an arm 62 supporting the nozzle 61 in a horizontal direction, a pillar 63 vertically extending and supporting the arm 62, a drive mechanism (which is not shown) for rotating the arm 62 around the pillar 63 and moving the same up and down along the pillar 63, and a pump 65. A tube 66 connecting the nozzle 61 and the pump 65 is provided with an inlet valve 64. The nozzle 61 is provided at its distal end with a liquid level sensor (which is not shown).
The working liquid reserving portion 3 has a working liquid container 32 for reserving working liquid 321. A tube 37 connecting the pump 65 with the working fluid container 32 is provided with an outlet valve 36. Pump systems used in other embodiments according to the invention have configurations similar to the pump system in this embodiment. In this embodiment, the pump 65 is a syringe pump. The syringe pump is adapted to suck and discharge fluid into and from a pump chamber by taking a plunger of a syringe which is sealed by O-rings or the like in and out of the pump chamber having a certain volume so as to change the space volume in the pump. In the case of feeding the fluid in one direction, for example, from the inlet side to the outlet side, an inlet valve is opened while an outlet valve is closed, and then the plunger is made to go back from the inside of the pump chamber to the outside so as to suck the fluid through the inlet valve. Then, the inlet valve is closed while the outlet valve is opened, and then the plunger is made to go forward in the pump chamber so as to discharge the fluid through the outlet valve. Thus, the fluid is displaced from the inlet side to the outlet side. In order to feed the fluid in the reverse direction, the opening and closing of the valve are reversely carried out. The following explanation will be made in such a condition that the fluid is displaced in a designated direction by driving the pump, without specifically explaining the operation of the valves.
As the working fluid 321 in the pump system is used a kind of liquid which cannot be resolved by and mixed into the sample 121 and the reagent. In this embodiment, the working liquid 321 is oil.
The analysis device 2 has a structure in which boards are stacked one upon another, having an upper access board 201, an upper electrode board 23 underneath the above, a spacer board 22 underneath the upper electrode board 23, a lower electrode board 21 further underneath the spacer board 22, and a lower access board 202 on a lower side. The spacer board 22 is cut out at the predetermined area, so as to define therein a space. In
The space formed by cutting out the spacer board 22 is filled therein with the oil. The drive electrode 211 has a function of a passage for displacing liquid drops of the sample 121 and the reagent within the oil. The drive of the sample 121 and the reagent in the oil, as mentioned above, is carried out with the use of the EWOD which will be detailed later.
In one or both of the upper access board 201 and the lower access board 202 are incorporated a Peltier element, a heater or the like which can be controlled by control means not shown, so as to control the temperature of the analysis device 2.
The upper access board 201 is provided with a sample port 11, reagent ports 41, a waste port 51, an oil level detecting port 791, a detector 95 and an inclination sensor 91. The oil level detecting port 791 is provided therein with an oil level sensor 792 for detecting the level of the oil retained in the space of the analysis device 2. As the oil level sensor, there may be used any type of well-known technology for detecting a liquid level, such as an optical type for detecting a distance from a liquid surface in view of a reflected quantity of light radiated thereto, an ultrasonic type for detecting a distance from a liquid surface in view of a time by which an ultrasonic wave emitted to the liquid surface is returned or an electrostatic type for detecting an increase in an electrostatic capacity depending upon a contacting length of liquid making contact with an electric wire submerged in the liquid. As the detector 95, there may be used a device for measuring an optical characteristics, such as a light absorbance measuring unit, a fluorescence measuring device or the like. However, there may be also used a device for measuring another physical value such as an electric or magnetic value. In this embodiment, a device for measuring optical characteristics is used.
The lower access board 202 is provided with an oil supply port 71, an oil drain port 81 and an inclination adjusting portion 90.
The above-mentioned ports 11, 41, 51, 791, 71, 81 have cylindrical shapes, each having a cylindrical part defined therein with a cavity piercing through the access boards so as to be communicated with the space.
The inclination adjusting portion 90 may hold the analysis device 2 horizontally or may incline the same at a desired angle. An inclined angle signal obtained by the inclination sensor 91 is delivered to an attitude control mechanism which is not shown and which drives the inclination adjusting mechanism 90 so as to horizontally hold the analysis device 2 or to incline the same at a desired angle.
The altitude control mechanism holds the analysis device horizontally during, for example, a normal operation mode such as a pipetting mode or a measuring mode. When a surface on which the analysis device is mounted is unexpectedly inclined, the analysis device 2 is inclined so as to cancel out the inclination of the surface. In the case of expelling bubbles trapped in the liquid retained in the space in the analysis device 2, in the case of maintenance for replacing oils and so forth, the analysis device is inclined by the attitude control mechanism.
The reagent pipetting portion 4 includes reagent containers 42 for reserving reagents, and nozzles 43 incorporating valves 44 are connected to the bottoms of the reagent containers 42, respectively. The tip ends of the nozzles 43 are located in the reagent ports 41, respectively. It is noted that the reagent pipetting portion 4 may be provided therein with a pump. The waste liquid discharging portion 5 has a waste liquid pump 55 for pumping out waste liquid, which is connected, at its bottom, thereto with a nozzle 53 provided with a valve 54. The tip end of the nozzle 53 is located in the waste liquid port 51. The waste liquid pump 55 is connected with a tube 57 incorporating a valve 56. The oil supply portion 7 includes an oil container 72 for reserving the oil 721, which container is connected to the oil supply port 71 by a tube 77 incorporating a valve 76 and a tube 73 incorporating a pump 75 and a valve 74. The oil separating portion 8 has a separator 88 for separating oil from waste liquid and a waste liquid container 82 for reserving waste liquid. The separator 88 is connected to the oil drain port 81 by a tube 83 incorporating a valve 84. The separator 88 is also connected to the waste liquid pump 55 by a tube 57 incorporating a valve 56. The separator 88 separates oil from the waste liquid by utilizing a conventional technology such a specific weight difference, centrifuge, filtering or the like.
As the oil 721, there may be used a liquid which cannot be dissolved and mixed into the sample 121 and the reagents. As the liquid which is not mixed with the sample 121, there may be used a liquid having a specific weight which is larger and or lower than that of the sample 121. For example, in the case of analyzing a water based solution such as blood as the sample 121, silicon oil or hydrocarbon oil may be used. In such a case that the sample 121 is a liquid other than a fluorine system liquid containing fluorine, perfluorocarbon oil is desirably used, having a specific weight greater than 1. Incidentally, the working fluid 321 may be equal to the oil 721. Explanation will be hereinbelow made in such a condition that the working fluid 321 is equal to the oil 721.
In this embodiment, as the oil 721 or the working fluid 321, fluorine oil having a specific weight greater than 1 is used.
At first, the oil is fed from the oil supply portion 7 into the analysis device 2. The oil supply pump 75 is driven so as to feed the oil 721 from the oil container 72 to the oil supply port 71 from which the oil flows into the space in the analysis device 2. The air occupied in the space is discharged outside from the sample port 11, the reagent port 41, the waste liquid port 51 and the like in the upper access board 201. Thus, the air in the space in the analysis device 2 is replaced with the oil 721. The level of the liquid surface of the oil 721 in the space is detected by the oil level sensor 792 provided in the oil level detecting port 791. When the level of the oil 721 in the space comes up to a predetermined height, the operation of the oil supply pump 75 is stopped by a control device which is not shown. It is noted that oil level sensor 792 always monitors an oil level in the oil level detecting port 791, and accordingly, when it detects that the oil level lowers, it informs the control device of this fact. Thus, the control means drives the oil supply pump 75 in order to replenish the space with the oil. Accordingly, the level of the liquid surface of the oil retained in the space in the analysis device 2 is always maintained to be constant.
The sample port 11 has a bore diameter which is larger than the outer diameter of the nozzle 61 which can be therefore inserted into the sample port 11. When the nozzle 61 is inserted into the sample port 11, the tip end of the nozzle 61 dips into the oil retained in the space in the analysis device 2. Thus, the inner surface of the tip end of the nozzle 61 is covered thereover with the oil 721. Further, the pump 65 is driven so as to suck the oil into the nozzle 61 and then discharge it. Accordingly, the inner surface of the nozzle 61 is covered with the oil 721. Thus, when the sample 121 is sucked into the nozzle 61, the oil repels the sample 121 so as to prevent contamination to the surface of the nozzle 61. Thereby, the pipetting of the sample 121 is carried out after the tip end of the nozzle 61 is covered with the oil 721.
Next, the sample pipetting portion 6 pipettes the sample into the analysis device 2. The arm 63 is pivoted around the pillar 63 by the drive mechanism, and when the nozzle 61 comes to a position of a desired sample cup 12, the arm 62 is lowered along the pillar 63. The liquid level sensor provided in the nozzle 61 detects the liquid surface of the sample 121, and the nozzle 61 is sunk thereinto to a predetermined depth. The pump 65 is driven to suck a predetermined quantity of the sample 121, and thereafter, the operation of the pump 65 is stopped. The arm 62 is raised by the drive mechanism, and is then rotated. When the nozzle 61 is located at the position of the sample port in the analysis device 2, the arm 62 is lowered along the pillar 63. When the nozzle 61 is located in the sample port 11, the pump 65 is driven to discharge the sample 121 into the sample port 11. The sample 121 fed into the sample port 11 is laid on the oil without being mixed with the oil.
Next, the reagent pipetting portion 4 pipetts the reagent into the analysis device 2. When the vale 44 is opened, the reagent is discharged from the reagent container 42 into the reagent port 41. The reagent fed into the reagent port 42 is laid on the oil without being mixed therewith.
A valve (which is not shown) is provided on the upper surface of each of the reagent containers 42 of which the inside is therefore communicated with the atmosphere, and accordingly, a reagent in the reagent container 42 flows into the reagent port 41 under the gravitation. When a flow volume of the reagent is adjusted depending upon an opening time of the valve 44. When the reagent is fed into space in the analysis device 2, the liquid level in the oil liquid level detecting port 791 varies. The thus obtained variation value is detected by the oil level sensor 792 so as to calculate a quantity of the reagent having flown into, and when a desired quantity of the reagent is fed, the valve 11 may be closed.
The sample 121 fed into the sample port 11 and the reagent fed into the reagent port 41 are processed by using the EWOD. That is, they are displaced along the drive electrode 211 in the form of liquid drops. The sample and the reagent are mixed with each other in a predetermined zone on the drive electrode 211 so as to execute a predetermined chemical reaction. After the completion of the chemical reaction, they are fed to the detector 95.
The detector 95 measures predetermined optical characteristics such as a degree of light absorbance of the reacted solution or a degree of fluorescence. In this embodiment, the detector 65 detects a light quantity, and accordingly, holes are formed in the upper and lower access boards 201, 202 at a position where the detector 95 is located. One or both of the upper and lower electrode boards 23, 21 are made of transparent electric materials such as ITO (Indium-Tin-Oxide).
Waste liquid having been measured by the detector 95 is displaced along the drive electrode 211, and is fed into the waste liquid port 51.
Next, the waste liquid is discharged from the analysis device 2 by the waste liquid discharging portion 5. The waste liquid comes up in the waste liquid port 51 with a specific weight different between itself and the oil, and stagnates therein.
The waste liquid pump 55 is driven so as to pump up the waste liquid from the waste liquid port 51 into the separator 88 for separating the oil from the waste liquid. The separated oil is recovered into the oil container 72 while the remaining waste liquid is discharged into the waste liquid container 82.
If the specific weight of the oil 721 is less than that of the waste liquid, a waste liquid port (which is not shown) is formed in the lower access board 202. The waste liquid descends with the specific weight difference between itself and the oil, and stagnates. The waste liquid is sucked up by a waste liquid pump (which is not shown) through a tube (which is not shown) connected to the waste liquid port 51, and is then fed into the oil separating portion 8.
In the case of discharging all oil 721 from the analysis device 2 during maintenance or the like, it is sufficient to open the valve 84. The oil 721 in the analysis device 2 is discharged under the gravitation by way of the oil drain port 81, and is then fed into the separator 88 for removing the waste liquid contained in the oil, and accordingly, the oil is recovered into the oil container 72 while the waste liquid is discharged into a waste liquid container 82. The analysis device 2 is inclined by the inclination adjusting portion 90 so that the oil drain port 81 takes its lowermost potion. Thus, the oil in the analysis device 2 is completely discharged.
In this embodiment, before the sample is pipetted by the sample pipetting portion 6, the tip end of the nozzle 61 can be covered with the oil so as to prevent the sample from sticking to the nozzle 61. Accordingly, the sample sucked into the nozzle 61 is prevented from being mixed with a sample which was pipetted during the last measurement, thereby it is possible to enhance the degree of accuracy of measurement. Further, since the nozzle is prevented from being contaminated with the sample, it is not necessary to wash the nozzle. Thus, no nozzle washing mechanism is required, thereby it is possible to miniaturize the chemical analysis apparatus and to reduce the costs thereof.
In this embodiment, since the oil level sensor 792 is provided in the oil level detecting port 791, the quantity of a solution such as the sample or the reagent fed into the analysis device can be precisely controlled. Thus, it is possible to enhance the accuracy of pipetting into the analysis device.
Further, it is possible to detect a decrease and a consumption of the oil by the oil level sensor 792, and accordingly, the oil quantity in the analysis device can be maintained to be constant. Thus, even though the analysis device in the embodiment is used for a long time, the oil quantity in the analysis device is always maintained to be always constant, air bubbles can be prevented from being mingled into the oil, and simultaneously, the oil can be automatically updated. Further, with the provision of the oil separating portion, the oil can be recovered, thereby it is possible to reduce the consumption of the oil.
The essential feature of the present invention is the provision of the analysis device, and accordingly, the components other than this device may be replaced with suitable ones. For example, a sample may be pipetted into the sample port 11 manually, instead of using the sample pipetting portion 6. Further, the reagent may be pipetted manually, instead of using the reagent pipetting portion 4. Similar to the sample disc 1, the reagent may be pipetted from a rotatable reagent disc carrying thereon a plurality of reagent containers with the use of the sample pipetting portion 6.
Detailed explanation will be hereinbelow made of the structure of the analysis device 2 with reference to
The insulator film 212 may be a dielectric film, being made of Parylen (Trade Name) or SiO2 by means of a CVD process. The water repelling film 213 may be a coating of a fluorine system repellant such as AF1601 (Trade Name).
Between the upper electrode board 23 and the lower electrode board 21, there is arranged a spacer board 22 which is removed or cut out in its predetermined zone. The zone where the spacer board 22 is cut out, defines a space 24. As shown, the oil 721 is filled in this space 24, and is contained therein with a liquid drop 1211 of the sample. The liquid drop 1211 is laid on the electrode 211a and covers in part over the electrode 211b adjacent thereto. A negative voltage is applied to the common electrode 214. When a positive voltage having been applied to the electrode 211a is cut off while a positive voltage is applied to the adjacent electrode 211b, the wettability of the insulator film 212 on the electrode 211b becomes higher so as to decrease the contact angle. Accordingly, the liquid drop 1211 is attracted to the adjacent electrode 211b which is applied with the positive voltage. As a result, the liquid drop 1211 is displaced onto the adjacent electrode 211b. With the repetitions of the above-mentioned steps between the adjacent electrodes, the liquid drop 1211 is successively displaced along the drive electrode 211.
In this specification, the above-mentioned phenomenon will be referred to as “EWOD”. The EWOD is defined as a phenomenon that the contact angle between an insulator film on an electrode and a liquid is decreased by applying a voltage between two electrodes between which the liquid such as water to be polarized is interposed, and accordingly, the wettability is enhanced. Thus, in this embodiment, the sample and the reagent can be displaced along the drive electrode 211 by the EWOD technology and mixed with each other in a predetermined zone. The mixture of the sample and the reagent is transferred below the detector 95 for detecting light.
Next, explanation will be made of the sample pipetting portion 6. The oil 721 is reserved in the working fluid container 32. The syringe pump 75 is driven so as to fill the oil 721 up to a position in the vicinity of the tip end of the nozzle 61. The nozzle 61 is inserted into an arbitrary sample cup 12 on the sample disc 1 and the syringe pump 65 is driven so as to suck the sample 121 into the nozzle 61. The nozzle 61 is shifted to a position above the sample port 11, and then, the syringe pump 65 is driven so as to discharge the sample 121. A pipetting quantity of the sample 121 may be adjusted, depending upon a displacement of the plunger in the syringe pump 65.
The specific weight of the fluorine oil is about 2 while the specific weight of the water based sample 121 is about 1. Since the oil 721 and the sample 121 are never mixed with each other, the sample 121 led into the sample port 11 floats on the oil 721. Before the sample 121 is pipetted, the liquid level in the sample port 11 is equal to the level of the oil in the oil level detecting port 791. After the sample 121 is pipetted, the level of the liquid surface in the sample port 11 is higher than the level of the oil in the oil level detecting port 791. Accordingly, the height of the sample port 11 is set to a predetermined value which can prevent the sample 121 from overflowing from the sample port 11 after the sample 121 is pipetted.
Next, the syringe pump 75 in the oil supply portion 7 is driven so as to suck the oil 721 in the space 24 in the analysis device 2 so as to return the oil into the oil container 72. Thus, the liquid level in the sample port 11 is lowered, and accordingly, the interface between the sample and the oil comes to the upper electrode board 23. The level of the oil in the oil level detecting port 791 is also lowered. The liquid level in the sample port 11 is above the level of the oil in the oil level detecting port 791, but the interface between the sample and the oil in the sample port 11 is below the level of the oil in the oil level detecting port 791.
With the assumption that the lower electrode board 21 is horizontal, heights of the liquid levels are measured from the position of the lower electrode board 21 as a reference. It is noted that affection by meniscus is negligible, and it is estimated that the liquid surfaces are horizontal. The following formula is obtained:
ρS*hS+ρ0*h0S=ρ0*h0 (1)
where ρS is a specific weight of the sample 121, hS is a length of a liquid column of the sample 121, ρ0 is a specific weight of the oil 721, h0S is a height of the interface between the oil 721 and the sample 121, and h0 is a level of the oil in the oil level detecting port 791.
Thus, a difference between the height h0S of the interface between the oil 721 and the sample 121, and the level of the oil h0 in the oil level detecting port 791 is exhibited by the following formula:
h0−h0S=(ρS/ρ0)*hS (2)
That is, the difference between the height h0S of the interface and the level h0 of the oil is about one half of the length of the liquid column of the sample. Thus, until the liquid level is lowered by a half of the length of the liquid level of the sample, the oil 721 may be sucked. Further, if the oil 721 in the space 24 within the analysis device 2 is continuously sucked, the sample 121 enters into the space 24 in the analysis device 2, passing by the connection between the lower end of the sample port 11 and the upper electrode board 23. If the quantity of the sample fed into the sample port 11 is sufficient, no air enters into the space in the analysis device 2 from the oil level detecting port 791 even thought the liquid level in the oil level detecting port 791 is lowered. The sample 121 having entered in the space in the analysis device 2 is laid on the drive electrode 211 on the lower electrode board 21, and accordingly, it may be displaced by the above-mentioned EWOD.
Thus, a predetermined quality of the sample 121 is pipetted into the space in the analysis device 2. After completion of pipetting of the sample, the syringe pump 75 in the oil supply portion 7 is driven so as to fill the oil 721 into the space in the analysis device 2 from the oil supply port 71. Accordingly, the liquid level in the sample port 11 and the oil level in the oil level detecting port 791 come up. The sample remaining in the sample port 11 overflows from the upper end of the sample port 11 and then falls onto the upper access board 201. If the height of the sample port 11 is lower than that of the oil level detecting port 791, all sample remaining in the sample port 11 may be discharged. A discharge channel may be provided on the upper access board 201 around the sample port 11. The sample and the oil having fallen in this discharge channel are led into the oil separating portion 8. Alternatively, the sample remaining in the sample port 11 may be sucked by the nozzle 61 of the sample pipetting portion 6 so as to discard it into an external waste liquid container.
In this embodiment, the sample and the oil respectively form separate layers in the sample port 11, and they are never mixed with each other. Accordingly, unnecessary sample may be discarded or recovered through simple operation. In this description, explanation has been made of the pipetting operation of the sample 121, and the reagent may be also pipetted by a similar operation.
Explanation will be hereinbelow made of another embodiment of the sample pipetting portion 6 according to the present invention with reference to
Referring to
A positive voltage is applied to the electrode on the lower electrode board 21 while a negative voltage is applied to the nozzle 61. Instead of applying the negative voltage to the nozzle 61, the nozzle 61 may be grounded.
Thus, the sample 121 is attracted to the drive electrode on the lower electrode board 21 under the EWOS phenomenon, and is then advanced along the drive electrode in the space within the analysis device 2.
After a predetermined quantity of the sample 121 is pipetted by into the space in the analysis device 2, as shown in
The sample 121 in the space within the analysis device 2 is retracted while it is attracted from the drive electrode side to the nozzle 61 side, and is returned into the nozzle 61, being separated from the drive electrode. When the sample is separated from the drive electrode, a slight variation in potential or current occurs. Thus, by detecting the variation in potential or current, it is found that the sample 121 is separated from the drive electrode. After the sample 121 is separated from the drive electrode, the operation of the syringe pump 65 is stopped so as to stop the suction of the sample 121.
The nozzle 61 is lifted up from the sample port 11 and is shifted into a sample discarding place which is not shown, and the syringe pump 65 is driven so as to discharge the sample 121 from the nozzle 61. In this embodiment, since the oil 721 is used as the working fluid 321, the syringe pump is continuously driven until the oil 721 is discharged from the tip end of the nozzle 61, and accordingly, the sample 121 is completely discharged from the nozzle 61.
According to this embodiment, by enhancing the wettability of the surface of the nozzle under the EWOD during the discharge of the sample, the sample is attracted to the nozzle so as to be smoothly returned. Thus, no sample remains in the analysis device so as to prevent affection upon measurement for another sample, thereby it is possible to enhance the accuracy of measurement.
Explanation will be hereinbelow made of the configuration and operation of the reagent pipetting portion 4 according to the invention with reference to FIGS. 5 to 9. The structure of the analysis device 2 is the same as that explained with reference to
The nozzle 43 at the lower end of the reagent container 42 is inserted into the reagent port 41 so that the tip end of the nozzle 43 is adjacent to the lower electrode board 21.
The nozzle 43 is coated over its upper end surface, inner surface and lower end surface with an insulator film 431 formed of a dielectric thin film. Further, the insulator film 431 on the nozzle 43 and the outer surface of the nozzle 43 are coated thereover with a fluorine system water repelling film 432. Thus, the nozzle 43 which is coated thereover with the insulator film 431 and the water repelling film 432 is attached to the lower end of the reagent container 42 by bonding or the like.
The nozzle 43 and the reagent container 42 which are made of conductive materials such as stainless steel, are electrically isolated from each other by the insulator film 431. The nozzle 43 is electrically isolated from the common electrode 214 by the insulator film 431.
The reagent container 42 is provided at its upper surface with a valve (which is not shown) which is normally closed. When this valve is opened, the reagent container 42 is communicated with the atmospheric pressure or a pressure source (which is not shown).
In this embodiment, the reagent container 42 serves as a common electrode while the nozzle 43 serves as a drive electrode. Accordingly, the reagent container 42 is connected to a negative electrode of a power source through a switch 461. The nozzle 43 is connected to a positive electrode of the power source through a switch 462. The electrodes 2111, 2112 are connected to a positive electrode of the power source through switches 463, 464, respectively. The common electrode 214 at the inner surface of the upper electrode board 23 is connected to the negative electrode of the power source.
In the case of the reagent container 42 which is made of nonconductive materials, a terminal (which is not shown) is provided in the reagent container 42, making contact with the reagent 421, and is connected to the negative electrode of the power source by a lead wire led out from the terminal to the outside, through a switch 461.
Referring to
As shown in
Next, as shown in
As shown in
Next, as shown in
In this embodiment, control for a hydraulic pressure and a surface tension is important. At first, consideration will be made of the displacement of the liquid in the nozzle 43. A ratio Pσ/Ph between a vertical component Pσ of the surface tension and a vertical force Ph obtained by the hydraulic pressure is exhibited by the following formula:
Pσ/Ph=2πrσ cos θ/πr2P=2σ cos θ/rP (3)
where r is a bore diameter of the nozzle 43, σ is an interfacial tension between the reagent 421 and the oil 721, θ is a contact angle and P is a hydraulic pressure at the interface between the reagent 421 and the oil 721.
In such a case that the above-mentioned ratio is greater than 1 while the interfacial tension acts upward, the reagent 421 comes up through the nozzle 43. The inner diameter of the reagent container 42 is sufficiently larger than the bore diameter of the nozzle 43, and accordingly, an ascent of the level of the liquid surface in the reagent container 42 due to an ascent of the reagent 421 is negligible. Thus, the hydraulic pressure (water head difference) at the interface between the reagent 421 and the oil 721 decreases corresponding to the distance that the reagent 421 comes up in the nozzle 43. The smaller the hydraulic pressure (water head difference) at the interface is, the smaller the ratio exhibited by the formula 3 is, and the reagent 421 within the nozzle 43 returns into the reagent container 42. Since the diameter abruptly increases at a joint which is a transition from the nozzle 43 into the reagent container 42, the ratio exhibited by the formula 3 abruptly decreases, becoming not greater than 1, and accordingly, the oil 721 is never displaced from the nozzle 43 to the reagent container 42.
Further, in such a case that the ratio exhibited by the formula 3 is less than 1, the reagent 421 comes down through the nozzle 43. A descent of the level of the liquid surface in the reagent container 42 due to the descent of the reagent 421 is negligible. Accordingly, the hydraulic pressure (water head difference) at the interface becomes large, corresponding to a distance that the reagent 421 comes down. The larger the hydraulic pressure (water head difference) at the interface is, the smaller the ratio exhibited by the formula 3 is, and the reagent 421 comes down, through the nozzle 43, to the lower end of the nozzle 43. An increment of the hydraulic pressure at the lower end of the nozzle 43 is in proportion to a length L of a liquid column of the reagent in the nozzle 43. Thus, the hydraulic pressure at the lower end of the nozzle 43 becomes P0+kL where P0 is a hydraulic pressure at the interface, and k is a proportional constant.
The contact angle θ is from 130 to 140 deg., in the case of application of no voltage. In such a case that the interface between the reagent and the oil is located in the inlet at upper end of the nozzle 43 and no voltage is applied to the nozzle 43, the ratio exhibited by the formula 3, that is, (vertical component of the interfacial tension)/(hydraulic pressure (nozzle)), is not less than 1. When a positive voltage is applied to the nozzle 43, the contact angle θ is decreased so that the vertical component Pσ of the interfacial tension decreases. If the contact angle θ becomes smaller than a predetermined value, the ratio exhibited by the formula 3 becomes smaller than 1. If the contact angle θ is set to θ0 with which the ratio exhibited by the formula 3 is smaller than 1, the contact angle θ=θ0 satisfies the following formula 4:
θ=θ0<cos−1(rP0/2σ) (4)
Thus, the nozzle 43 is applied with a voltage so that the contact angle θ becomes θ0. Thus, the reagent comes down through the nozzle 43, and enters into the space in the analysis device 2 where it spreads over in a circular shape. When the circle of the reagent has a radius R, and a gap (height) between the upper common electrode 214 and the lower drive electrode 211 is H, a ratio between an interfacial tension Hσ and a hydraulic pressure Ph is given from the following formula, with such assumption that the gap (height) H is sufficiently smaller than the water head difference and the hydraulic pressure is uniform in the space within the analysis device 2:
Hσ/Ph=2×2πRσ cos θ/2πRHP=2ρ cos θ/HP (5)
If the ratio is larger than 1, the reagent 421 cannot spread over in the space within the analysis device 2. If the ratio is smaller than 1, the reagent 421 spreads over in the space within the analysis device 2. In order to set the ratio to a value greater than 1, the contact angle θ is set to be larger than a predetermined value. At the end, a condition in which the reagent comes down through the nozzle 43 but does not spread over in the space within the analysis device 2 is such that the contact angle θ has to satisfy the following formula 6:
cos−1{H(P0+kL)/2σ}<θ<cos−1(rP0/2σ) (6)
where (P0+kL) is a hydraulic pressure in the space within the analysis device 2.
By detecting a variation in the voltage, the electric capacity or the like between the reagent 421 and the electrode 211, entrance of the reagent 421 into the space in the analysis device is determined. As shown in
Thus, the reagent 421 is separated so as to form a liquid drop 4211 of the reagent on the electrode 2112. The drop of the reagent is further separated into a predetermined quantity of the liquid drops through the pipetting operation under the EWOD.
For example, estimation is made such that the bore diameter r of the nozzle 43 is 0.2 mm, the interfacial tension σ is 0.07 N/m which is substantially equal to that of the water, and the water head P is 10 mmH2O. When no voltage is applied to the nozzle 43, the ratio exhibited by the formula 3, that is, (vertical component of interfacial tension)/(hydraulic pressure (nozzle)) is =5.3 if the contact angle is θ=140 deg. Thus, the reagent 421 does not come down through the nozzle 43.
Next, the nozzle 43 is applied thereto with a voltage so that the contact angle is θ<99 deg., and accordingly, the hydraulic pressure overcomes the interfacial tension. Thus, the ratio exhibited by the formula 5, that is, (vertical component of interfacial tension)/(hydraulic pressure) is <1. Thus, the reagent 421 comes down through the nozzle 43.
Further, it is estimated that the gap between the upper common electrode 214 and the lower drive electrode 211 is H=0.3 mm, and the length of the nozzle 43 is L=10 mm. When no voltage is applied to the drive electrode 2113 on the lower electrode board 21, the contact angle is θ=140 deg., and accordingly, (interfacial tension)/(hydraulic pressure (device)) is =1.8. Thus, the reagent 421 does not enter into the space in the analysis device 2.
When a voltage is applied to the drive electrode 213 so that the contact angle is θ<116 deg., (interfacial tension)/(water pressure (device)) becomes less than 1, and accordingly, the reagent 421 enters into the space in the analysis device 2.
In this embodiment, the electrodes are used in the mechanism for pipetting the reagent, and the wettability of the electrodes are controlled, depending upon a voltage applied to the electrodes. Thus, a desired quantity of the reagent or the like may be pipetted. Accordingly, no moving component is present, thereby it is possible to simplify the mechanism and to miniaturize the apparatus.
Explanation will be made of the configuration and the operation of the reagent pipetting portion 4 in the chemical analysis apparatus according to the present invention, with reference to
The reagent pipetting portion 4 in this embodiment has a reagent container 42 which reserves therein the reagent, and a nozzle 43 incorporating a valve 44 and connected to the bottom of the reagent container 42. The tip end of the nozzle 43 is located in the reagent port 41.
The reagent container 42 is provided for each reagent port 41. The reagent 421 is fed in response to opening and closing of the valve 44. The feed quantity of the reagent 421 may be adjusted through the detection of variation of the level of the liquid surface by means of an oil level sensor 792 provided in the oil level detecting port 791. It is noted that the time of opening and closing the valve 44 may be set depending upon data obtained from a relationship between an opening time of the valve 44 and the feed quantity, which has been previously obtained. Further, a potential or a current between the electrode 2111 and the reagent 421 in the space within the analysis device 2 may be measured in order to detect a flow-down quantity of the reagent 421. Further, with the provision of a micropump, as disclosed in JP-11-082309 A, at the bottom of the reagent container 42, the reagent 421 may be fed after discharging it in the air.
In the embodiment shown in
Next, referring to
Brief explanation will be hereinbelow made of the flow of the liquid. Detailed explanation thereof will be made later with reference to
The sizes of the electrodes correspond to the quantity of the liquid drops retained thereby. Accordingly, the electrodes at the ports are large. Further, the crossing point electrodes are relatively large since they retain thereon the mixture of two liquid droplets.
In each electrode train, electrodes are provided on opposite sides of each of the electrode having odd number, except those at the ports. These opposite side electrodes have a function of separating the liquid drop. Detailed explanation will be made later. Further, two adjacent electrodes are formed in a comb-like shape so that they are telescopically arranged at their joint. This configuration will be also explained in detail later with reference to
Referring to
As shown in
The circumferential length of a circle shape is shortest among those of other shapes. Thus, with equal volume of liquid, a circular liquid drop has a smallest surface energy so as to be stable. Thus, in this embodiment, the liquid may be stably retained on the electrode.
In consideration of separation of the liquid drop, when a voltage is applied to the opposite end electrodes while no voltage is applied to the center one, the wettability of the opposite end electrodes is enhanced, and accordingly, the liquid drop (in a hatched part in the figure) is pulled apart by the opposite end electrodes as shown in the figure, and accordingly, the liquid drop is separated.
In the case of the electrodes having an equal area, the circumferential length of the liquid drop shown in
Upon serration, as shown, the liquid remains on the center electrode. The liquid reaming on the center electrode in the case shown in
Detailed explanation will be hereinbelow made of a method of pipetting the reagent, according to the present invention, with reference to
Next, as shown in
The liquid on the third electrode 2113 on which the application of the voltage is cut off, is attracted to the adjacent second electrode 2112 and the opposite electrodes 2119, 2119. A substantial part of the liquid on the fourth electrode 2114 on which the application of the voltage is cut off is attracted to the opposite electrodes 2119, 2119 by way of the adjacent third electrode 2113. The remaining liquid on the fourth electrode 2114 is joined with the liquid on the fifth electrode 2115, and is then attracted to the opposite electrodes 2120, 2120.
Finally, as shown in
Next, when a positive voltage is applied to the third electrode 2113 while the voltages applied to the opposite electrodes 2119, 2119 are cut off, the liquid on the electrodes 2119, 2119 are displaced onto the third electrode 2113. Next, when the voltages applied to the third electrode 2113 and the second electrode 2113 are successively cut off, the liquid on the third electrode 2113 and the second electrode 2112 is attracted to the first electrode 2111. Thus, all liquid are joined together on the first electrode 2111, leaving the liquid remaining on the fifth and seventh electrodes 2115, 2117.
Next, a process for displacing the liquid on the seventh electrode 2117 onto the eighth electrode 2118 is executed. A positive voltage is applied to the eighth electrode 2118 while the voltage applied to the seventh electrode 2117 is cut off. Thus, the wettability of the eighth electrode 2118 is enhanced while that of the seventh electrode 2117 is lowered. Thus, the liquid on the seventh electrode 2117 is displaced onto the eighth electrode 2118.
Finally, a process for collecting the liquid on the fifth electrode 2115 into large liquid drop on the first electrode 2111 is executed. When a positive voltage is applied to the adjacent fourth electrode 2114 while the voltage applied to the fifth electrode 2115 is cut off, the wettability of the fourth electrode 2114 is enhanced but the wettability of the fifth electrode 2115 is lowered. Thus, the liquid on the fifth electrode 2115 is displaced onto the fourth electrode 2114. With the repetitions of these steps for the third electrode 2113, the second electrode 2112 and the first electrode 2111, the liquid may be collected.
Although explanation has been hereinabove made of the process of pipetting the reagent, the process of pipetting the sample may be carried out, similar to that for the reagent. With the use of the processes, the sample may be mixed with the reagent as already explained with reference to
Referring to
In an example shown in
As stated above, in this embodiment, the two adjacent electrodes have overlapped zones, and accordingly, the liquid drop may be smoothly displaced.
Although explanation has been made of several embodiments of the present invention, the present inventions should not be limited to these embodiments, and various modifications may be made thereto within the technical scope of the present invention which will be defined by the appended claims.
It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-014493 | Jan 2005 | JP | national |
