Patent Publication Number: US-2019195905-A1

Title: Dispensing method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority based on 35 USC 119 from prior Japanese Patent Application No. 2017-250234 filed on Dec. 26, 2017, entitled “DISPENSING METHOD”, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The disclosure relates to a dispensing method, more particularly to a dispensing method executed in a robot system. 
     There has heretofore been known a dispensing method executed in a robot system. Such a dispensing method is proposed, for example, in a dispensing system disclosed in Japanese Patent Application Publication No. 2016-212077 (Patent Literature 1). 
     The dispensing system disclosed in Patent Literature 1 includes: a robot that moves a dispenser to aspirate a dispensing target liquid; a camera that captures an image containing a tip portion of the dispenser, the liquid surface of the liquid, and a non-dispensing target positioned below the liquid surface; an image processor that acquires positional information on the liquid surface, positional information on a boundary between the liquid and the non-dispensing target, and positional information on the tip portion of the dispenser, based on the image; and a descent controller that controls the robot to lower the dispenser based on the three pieces of positional information for aspiration of the liquid into the dispenser. 
     Incidentally, in the dispensing method disclosed in Patent Literature 1 executed in the robot system and other dispensing methods according to a related art executed in a robot system, a liquid L adheres to the outer surface of a tip  3  after the liquid L is aspirated into the tip  3 , as illustrated in  FIGS. 7A to 7C . This could make it difficult to accurately dispense a desired amount of liquid. Here, Patent Literature 1 proposes that the dispenser is lowered based on the positional relationship between the liquid surface and the distal end portion of the dispenser (point portion of a tip), determined from the image, thereby keeping the distal end portion of the dispenser at a shallow position from the liquid surface, and thus the amount of the liquid adhering to the tip portion of the dispenser is reduced. However, the dispensing system disclosed in Patent Literature 1 needs the camera or the like to capture the image, leading to a problem that the device configuration of the robot system becomes complicated. 
     In view of such a problem, one or more embodiments may provide a dispensing method which is executed in a robot system with a simple device configuration and also enables accurate dispensing of a desired amount of liquid. 
     SUMMARY 
     A method according to one or more aspects may be a dispensing method executed in a robot system, wherein the robot system includes: a pipette; a tip attached to the pipette; a container including a bottom surface, an inside surface, and an opening; a liquid contained in the container; and a robot including a robot arm, an end effector attached to a leading end of the robot arm, and a robot controller that performs operations on the pipette and the tip by controlling the robot arm and the end effector. The method may include: making the end effector hold the pipette and the tip attached to the pipette; dipping at least a point of the tip attached to the pipette in the liquid and aspirating the liquid into the tip; bringing an outer surface of the tip attached to the pipette into contact with a part of the container, wherein the part of the container is at least one of an edge of the opening and the inside surface; and pulling the pipette and the tip attached to the pipette out of the container through the opening. 
     A method according to one or more aspects may be a dispensing method to be executed in a robot system. The method may include: attaching a tip to a held pipette; moving the pipette so as to dip the tip in a liquid contained in a container, and aspirating the liquid into the tip; moving the pipette so as to bring the tip holding the aspirated liquid into contact with the container, thereby removing the liquid adhering to a side surface of the tip; and moving the pipette after bringing the tip into contact with the container, and discharging the liquid from the tip. 
    
    
     
       BRIEF Description of Drawings 
         FIG. 1  is a diagram illustrating a schematic view of an overall configuration of a robot system in which a dispensing method according to one or more embodiments is executed; 
         FIG. 2  is a diagram illustrating an external perspective view of an 8-channel pipette and tips attached thereto used in a dispensing method according to one or more embodiments; 
         FIG. 3A  is a diagram illustrating a schematic view of a first step of a dispensing method according to one or more embodiments, and  FIG. 3B  is a diagram illustrating a schematic view of a second step of a dispensing method according to one or more embodiments; 
         FIG. 4A  is a diagram illustrating a schematic view of a third step of a dispensing method according to one or more embodiments, and  FIG. 4B  is a diagram illustrating a schematic view of a fourth step of a dispensing method according to one or more embodiments; 
         FIG. 5A  is a diagram illustrating a schematic view of a third step of a dispensing method according to a first modification, and  FIG. 5B  is a diagram illustrating a schematic view of a fourth step of a dispensing method according to a first modification; 
         FIG. 6A  is a diagram illustrating a schematic view of a third step of a dispensing method according to a second modification, and  FIG. 6B  is a diagram illustrating a schematic view of a fourth step of a dispensing method according to a second modification; and 
         FIGS. 7A to 7C  are diagrams illustrating schematic views of how a liquid is aspirated into a tip in a related art dispensing method executed in a robot system. 
     
    
    
     DETAILED DESCRIPTION 
     A dispensing method according to a first aspect is a dispensing method executed in a robot system, wherein the robot system includes: a pipette; a tip attached to the pipette; a container including a bottom surface, an inside surface, and an opening; a liquid contained in the container; and a robot including a robot arm, an end effector attached to a leading end of the robot arm, and a robot controller that controls the robot arm and the end effector to perform operations on the pipette and the tip, the method including: making the end effector hold the pipette and the tip attached to the pipette; dipping at least a point of the tip attached to the pipette in the liquid and aspirating the liquid into the tip; bringing an outer surface of the tip attached to the pipette into contact with a part of the container, wherein the part of the container is at least one of an edge of the opening and the inside surface; and pulling the pipette and the tip attached to the pipette out of the container through the opening. 
     According to the above configuration, the liquid adhering to the outer surface of the tip can be wiped off by pulling the pipette and the tip attached thereto out of the container through the opening after bringing the outer surface of the tip attached to the pipette into contact with a part of the container, which is at least one of the edge of the opening and the inside surface. As a result, the dispensing method according to a first aspect is executed in the robot system with a simple device configuration and also enables accurate dispensing of a desired amount of liquid. 
     The pulling the pipette and the tip attached to the pipette out of the container through the opening may include pulling the pipette and the tip attached to the pipette out of the container through the opening while sliding the outer surface of at least the point of the tip attached to the pipette against the part of the container. 
     According to the above configuration, the liquid adhering to the outer surface of the tip can be surely wiped off. 
     For example, the opening may be formed across an entire top surface of the container, and a part of the container may be a curved portion positioned at an upper end of the inside surface or in a vicinity of the upper end of the inside surface. 
     For example, the opening may be formed across an entire top surface of the container, and a part of the container may be a portion of the inside surface, the portion extending in a height direction of the inside surface. 
     The dipping at least the point of the tip attached to the pipette in the liquid and aspirating the liquid into the tip may include dipping at least the point of the tip attached to the pipette in the liquid by bringing the point of the tip attached to the pipette into contact with or close to the bottom surface of the container. 
     According to the above configuration, at least the point of the tip attached to the pipette can be surely dipped in the liquid regardless of the height position of the liquid surface. 
     A dispensing method according to a second aspect is a dispensing method to be executed in a robot system, including: attaching a tip to a held pipette; moving the pipette so as to dip the tip in a liquid contained in a container, and aspirating the liquid into the tip; moving the pipette so as to bring the tip holding the aspirated liquid into contact with the container, thereby removing the liquid adhering to a side surface of the tip; and moving the pipette after bringing the tip into contact with the container, and discharging the liquid from the tip. 
     The dispensing method according to a second aspect is executed in the robot system with a simple device configuration and also enables accurate dispensing of a desired amount of liquid. 
     Embodiments are explained with referring to drawings. In the respective drawings referenced herein, the same constituents are designated by the same reference numerals and duplicate explanation concerning the same constituents may be omitted. All of the drawings are provided to illustrate the respective examples only. No dimensional proportions in the drawings shall impose a restriction on the embodiments. For this reason, specific dimensions and the like should be interpreted with the following descriptions taken into consideration. In addition, the drawings include parts whose dimensional relationship and ratios are different from one drawing to another. 
     (Overall Configuration) 
     With reference to the drawings, description is given below of a dispensing method according to one or more embodiments. Note that these embodiments do not limit the invention. 
     (Robot System  10 ) 
       FIG. 1  is a schematic view illustrating an overall configuration of a robot system in which a dispensing method according to one or more embodiments is executed. A robot system  10  according to one or more embodiments is used to automate enzyme-linked immunosorbent assay (ELISA) that has heretofore been manually performed, for example. Here, generally speaking, ELISA is assay to detect and quantify a target antigen and the like contained in a specimen by dispensing reagents and the like to cause antigen-antibody reaction. 
     As illustrated in  FIG. 1 , the robot system  10  includes an 8-channel pipette  18  (multichannel pipette), tips  30  attached to channels of the 8-channel pipette  18 , respectively, a container  100 , a liquid L contained in the container  100 , and a robot  50 . 
     (Robot  50 ) 
     The robot  50  includes a base  51 , a robot arm  60  connected to the base  51 , an end effector  70  attached to a leading end of the robot arm  60 , and a robot controller  90  that performs operations on pipettes  20  and the tips  30  by controlling the robot arm  60  and the end effector  70 . 
     (Robot Arm  60 ) 
     As illustrated in  FIG. 1 , the robot arm  60  is a multi-joint arm that includes six joints JT 1  to JT 6  and six links  65   a  to  65   f  sequentially connected by the joints JT 1  to JT 6 . The joints JT 1  to JT 6  of the robot arm  60  each include a motor and an encoder. 
     A connected body of the links and joints including the first joint JT 1 , the first link  65   a , the second joint JT 2 , the second link  65   b , the third joint JT 3 , and the third link  65   c  serves as a first arm section  61  of the robot arm  60 . To be more specific, the first joint JT 1  connects the base  51  to a base end of the first link  65   a  in a rotatable manner about an axis extending in a vertical direction. The second joint JT 2  connects a leading end of the first link  65   a  to a base end of the second link  65   b  in a rotatable manner about an axis extending in a horizontal direction. The third joint JT 3  connects a leading end of the second link  65   b  to a base end of the third link  65   c  in a rotatable manner about an axis extending in the horizontal direction. 
     A connected body of the links and joints including the fourth joint JT 4 , the fourth link  65   d , the fifth joint JT 5 , the fifth link  65   e , the sixth joint JT 6 , and the sixth link  65   f  serves as a second arm section  62  of the robot arm  60 . To be more specific, the fourth joint JT 4  connects a leading end of the third link  65   c  to a base end of the fourth link  65   d  in a rotatable manner about an axis extending in a longitudinal direction of the third link  65   c . The fifth joint JT 5  connects a leading end of the fourth link  65   d  to a base end of the fifth link  65   e  in a rotatable manner about an axis extending in a direction orthogonal to a longitudinal direction of the fourth link  65   d . The sixth joint JT 6  connects a leading end of the fifth link  65   e  to a base end of the sixth link  65   f  in a torsionally rotatable manner. Then, the end effector  70  is attached to a leading end of the sixth link  65   f.    
     (End Effector  70 ) 
     The end effector  70  includes a pipette holder  71  that holds the 8-channel pipette  18  and a pusher (not illustrated) that pushes a plunger of the 8-channel pipette  18  held by the pipette holder  71 . The end effector  70  according to one or more embodiments holds the 8-channel pipette  18 , thereby holding 8 channels (hereinafter referred to as the “pipettes  20 ” to avoid complicated description). 
     (Robot Controller  90 ) 
     A specific configuration of the robot controller  90  is not particularly limited. For example, the robot controller  90  may have a configuration realized by a publicly known processor (such as a CPU) operating according to a program stored in a storage unit (memory). The robot controller  90  executes the dispensing method according to one or more embodiments by controlling operations of the robot arm  60  based on pre-stored coordinate information and the like regarding distal ends of the pipettes  20  held by the end effector  70 . 
     (Pipette  20 ) 
       FIG. 2  is an external perspective view illustrating the 8-channel pipette and the tips attached thereto used in the dispensing method according to one or more embodiments. As illustrated in  FIG. 2 , the 8-channel pipette  18  includes the eight pipettes  20 , a housing  21  that houses central portions of the eight pipettes  20 , and the plunger (not illustrated) provided at an upper end of a member extending upward from a top surface of the housing  21 . The 8-channel pipette  18  is configured to aspirate the liquid L such as a reagent into the tips  30  attached to the eight pipettes  20  or to discharge the liquid L aspirated into the tips  30  by having the plunger pushed by the pusher of the end effector  70 . 
     The 8-channel pipette  18  may further include a tip injector (not illustrated) to remove the tips  30  attached to the pipettes  20 , an injector button (not illustrated) to activate the tip injector, and an amount setting scale (not illustrated) to set the amount of the liquid to be aspirated into the tips  30 . 
     (Tip  30 ) 
     In one or more embodiments, the robot system  10  includes at least eight tips  30  attached to the 8-channel pipette  18 . As for each of the tips  30  according to one or more embodiments, at least the point or distal end thereof and its vicinity portion have a hollow conical shape having its diameter increase from the point to the base or proximal end (see  FIG. 2  and the like). The tip  30  has an opening formed at its base end, and is attached to the pipette  20  by inserting the distal end portion of the pipette  20  from the opening. Note that the attachment of the tips  30  to the pipettes  20  may be automated in the robot system  10  or may be manually performed in advance. 
     (Container  100 ) 
     The container  100  according to one or more embodiments is a container (so-called reservoir) widely used for dispensing, which is highly resistant to a reagent and the like. As illustrated in  FIG. 3A  and the like, the container  100  includes a bottom plate  110 , a side plate  120  provided upright from an edge of the bottom plate  110 , and an opening  130  formed across the entire top surface. On an inner surface of the side plate  120  (an inside surface of the container  100 ), a curved portion  120   a  is provided, which is curved outward when seen from the bottom plate  110  (bottom surface of the container  100 ). As illustrated in  FIG. 3A  and the like, as for the curved portion  120   a  according to one or more embodiments, an outer edge of the upper end portion of the side plate  120  is formed into an arc shape protruding upward, and a lower end of the arc-shaped portion on the inner surface side serves as the curved portion  120   a . More specifically, the curved portion  120   a  is provided near the upper end of the inner surface of the side plate  120  in one or more embodiments. 
     (Liquid L) 
     The liquid L according to one or more embodiments is a reagent or the like used in a dispensing step for ELISA executed in the robot system  10 . 
     (Dispensing Method) 
     With reference mainly to  FIGS. 3A to 4B , description is given of an example of the dispensing method according to one or more embodiments executed in the robot system  10  described above.  FIGS. 3A and 3B  are schematic views illustrating first and second steps of the dispensing method according to one or more embodiments,  FIG. 3A  illustrating the first step and  FIG. 3B  illustrating the second step.  FIGS. 4A and 4B  are schematic views illustrating third and fourth steps of the dispensing method according to one or more embodiments,  FIG. 4A  illustrating the third step and  FIG. 4B  illustrating the fourth step. 
     (First Step) 
     First, as illustrated in  FIG. 3A , the end effector  70  holds the pipettes  20  and the tips  30  attached thereto. In one or more embodiments, the pipette holder  71  of the end effector  70  holds the 8-channel pipette  18 , thereby allowing the end effector  70  to hold the eight pipettes  20  and the tips  30  attached thereto. The first step is thus performed in one or more embodiments. 
     (Second Step) 
     Next, the robot arm  60  and the end effector  70  move the pipette  20  and the tip  30  attached thereto in the arrow direction (direction toward the inside of the container  100  along the axis direction of the tip  30 ) illustrated in  FIG. 3A  to dip at least the point of the tip  30  attached to the pipette  20  in the liquid L, thereby aspirating the liquid L into the tip  30  as illustrated in  FIG. 3B . Note that, in one or more embodiments, the point of the tip  30  attached to the pipette  20  is brought into contact with or close to the inner surface of the bottom plate  110  of the container  100  (the bottom surface of the container  100 ), and thus at least the point of the tip  30  attached to the pipette  20  is dipped in the liquid L. The second step is thus performed in one or more embodiments. 
     (Third Step) 
     The robot arm  60  and the end effector  70  further move the pipette  20  and the tip  30  attached thereto in the arrow direction (horizontal direction) illustrated in  FIG. 3B , thereby bringing the outer surface of the tip  30  attached to the pipette  20  into contact with the curved portion  120   a  (part of the container) formed on the inner surface of the side plate  120  as illustrated in  FIG. 4A . Note that, in one or more embodiments, the posture of the tip  30  after the third step is performed (that is, a predetermined angle or the like formed between the axis direction of the tip  30  and the vertical direction) is the same as that when the second step is performed. However, the invention is not limited thereto, but the posture of the tip  30  may be changed as needed. The third step is thus performed in one or more embodiments. 
     (Fourth Step) 
     Lastly, the robot arm  60  and the end effector  70  move the pipette  20  and the tip  30  attached thereto in the arrow direction (direction toward the outside of the container  100  along the axis direction of the tip  30 ) illustrated in  FIG. 4A  to pull the pipette  20  and the tip  30  attached thereto out of the container  100  through the opening  130  as illustrated in  FIG. 4B . In one or more embodiments, the pipette  20  and the tip  30  attached thereto are pulled out of the container  100  through the opening  130  while sliding the outer surface of at least the point of the tip  30  attached to the pipette  20  against the curved portion  120   a  in the fourth step. The fourth step is thus performed in one or more embodiments. 
     Advantageous Effects 
     In the dispensing method according to one or more embodiments, the liquid L adhering to the outer surface of the tip  30  can be wiped off by pulling the pipette  20  and the tip  30  attached thereto out of the container  100  through the opening  130  after bringing the outer surface of the tip  30  attached to the pipette  20  into contact with the curved portion  120   a  (part of the container). In other words, the tip  30  is attached to the held pipette  20 , and the pipette  20  is moved so as to dip the tip  30  attached to the pipette  20  in the liquid L contained in the container  100 , thereby aspirating the liquid L into the tip  30 . Then, the pipette  20  is moved in such a manner that the tip  30  holding aspirated liquid L is brought into contact with the container  100  to remove the liquid L adhering to the side surface of the tip  30 . Thereafter, the pipette  20  is moved, after the tip  30  is brought into contact with the container  100 , to discharge the liquid L from the tip  30 . Thus, the liquid L is prevented from adhering to the outer surface of the tip without acquiring a positional relationship between the point of the tip and the liquid surface by using a camera or the like as in the related art method, and keeping the point of the tip at a shallow position from the liquid surface based on the positional relationship, and the like. As a result, the dispensing method according to one or more embodiments is executed in the robot system  10  with a simple device configuration, and also enables accurate dispensing of a desired amount of liquid L. 
     In one or more embodiments, the liquid L adhering to the outer surface of the tip  30  can be surely wiped off by pulling the pipette  20  and the tip  30  attached thereto out of the container  100  through the opening  130  while sliding the outer surface of at least the point of the tip  30  attached to the pipette  20  against the curved portion  120   a  (part of the container) in the fourth step. 
     In one or more embodiments, the point of the tip  30  attached to the pipette  20  is brought into contact with or close to the inner surface of the bottom plate  110  of the container  100  (the bottom surface of the container  100 ) in the second step. Thus, at least the point of the tip  30  attached to the pipette  20  can be surely dipped in the liquid L without recognizing a height position of the liquid surface by complicated image processing or the like, for example. Moreover, even when the amount of the liquid L is decreased and the height position of the liquid surface comes close to the inner surface of the bottom plate  110 , failure to dip the tip  30  in the liquid L does not occur. Accordingly, the liquid L can be used up to the last drop. 
     In one or more embodiments, the point of the tip  30  attached to the pipette  20  is brought into contact with or close to the bottom plate  110  of the container  100  in a state where the axis direction of the tip  30  attached to the pipette  20  is tilted by a predetermined angle with respect to the vertical direction, as illustrated in  FIG. 3B , in the second step. Thus, the opening in the point of the tip  30  can be prevented from being crushed or closed by the point of the tip  30  being pushed against the bottom plate  110 , compared with the case where the point of the tip  30  is brought into contact with or close to the bottom plate  110  of the container  100  in a state where the axis direction of the tip  30  extends along the vertical direction, for example. 
     (Modification) 
     From the above description, many variations and other embodiments of the disclosure will be apparent to one skilled in the art. Therefore, the above description is to be construed as illustrative only, and is provided to teach one skilled in the art the best mode of implementing the invention. Details of the structures and/or functions can be substantially changed without departing from the spirit of the invention. 
     In the above embodiments, the description is given of the case where the outer surface of the tip  30  attached to the pipette  20  is brought into contact with the curved portion  120   a  formed on the inner surface of the side plate  120  (the inside surface of the container  100 ) in the third step and the case where the tip  30  attached to the pipette  20  is pulled out of the container  100  through the opening  130  while sliding the outer surface of at least the point of the tip  30  attached to the pipette  20  against the curved portion  120   a  in the fourth step. However, the invention is not limited thereto. For example, a first modification illustrated in  FIGS. 5A and 5B , a second modification illustrated in  FIGS. 6A and 6B , and the like are conceivable. 
       FIGS. 5A and 5B  are schematic views illustrating third and fourth steps of a dispensing method according to a first modification,  FIG. 5A  illustrating the third step and  FIG. 5B  illustrating the fourth step. 
     As illustrated in  FIG. 5A , in the third step according to a first modification, the outer surface of the tip  30  attached to the pipette  20  may be brought into contact with a portion of the inner surface of the side plate  120  (the inside surface of the container  100 ), the portion extending in a height direction of the inner surface of the side plate  120  (the inside surface of the container  100 ). To be more specific, the outer surface of the tip  30  may be brought into contact with approximately the entire area in the height direction of the inner surface of the side plate  120  (the inside surface of the container  100 ), for example. Then, the pipette  20  and the tip  30  attached thereto may be moved in the arrow direction (direction toward the outside of the container  100  along the axis direction of the tip  30 ) illustrated in  FIG. 5A  and pulled out of the container  100  through the opening  130  while sliding the outer surface of at least the point of the tip  30  attached to the pipette  20  against the portion extending in the height direction of the inner surface of the side plate  120  in the fourth step. 
       FIGS. 6A and 6B  are schematic views illustrating third and fourth steps of a dispensing method according to a second modification,  FIG. 6A  illustrating the third step and  FIG. 6B  illustrating the fourth step. 
     In a second modification, the tip  30  attached to the pipette  20  may be pulled out of the container  100  through the opening  130  (without sliding the outer surface of the tip  30  attached to the pipette  20  against a part of the container  100 ), after bringing the outer surface of the tip  30  attached to the pipette  20  into contact with the inner surface of the side plate  120  (the inside surface of the container  100 ) in the third step according to a second modification as illustrated in  FIG. 6A . Even through such procedure, the liquid L adhering to the outer surface of the tip  30  can be wiped off by the surface tension of the inside surface of the container  100  as illustrated in  FIGS. 6A and 6B . 
     In the above embodiments, the description is given of the case where the outer edge of the upper end portion of the side plate  120  is formed into an arc shape protruding upward, and the lower end of the arc-shaped portion on the inner surface side serves as the curved portion  120   a . However, the invention is not limited thereto. For example, when the side plate  120  has a simple flat plate shape and the outer edge of the upper end portion of the side plate  120  has a square shape, the inner-side upper end of the square shape portion (that is, the inner-side corner of the square shape portion or the edge of the opening  130  of the container  100 ) may serve as the curved portion  120   a . In such a case, the edge of the opening  130  of the container  100  and the inner surface of the side plate  120  are both included as a part of the container in the third and fourth steps. 
     In the above embodiments, the description is given of the case where the opening  130  is formed across the entire top surface of the container  100 . However, the invention is not limited thereto. More specifically, the container  100  may further include a top plate, and an opening may be formed by drilling a through-hole in the top plate. In such a case, an edge of the opening formed in the top plate is included as a part of the container in the third and fourth steps. 
     In the above embodiments, the description is given of the case where the outer surface of the tip  30  is brought into contact with a part of the container, which is the curved portion  120   a  of the inner surface of the side plate  120  (the inside surface of the container  100 ) or the portion extending in the height direction of the inner surface of the side plate  120  (the inside surface of the container  100 ). In this event, the outer surface of the tip  30  may be pushed against a part of the container  100  to the extent that the tip  30  slightly bends, for example. Thus, the outer surface of the tip  30  can be surely brought into contact with a part of the container  100 . In this way, the outer surfaces of all the tips  30  can be surely brought into contact with a part of the container  100  even in case of misalignment of the tips  30  attached to the eight channels when the dispensing method according to disclosure is performed using a multi-channel pipette such as the 8-channel pipette  18  in the above embodiments. 
     In the above embodiments, the description is given of the case where the axis direction of the tip  30  attached to the pipette  20  is tilted by a predetermined angle with respect to the vertical direction so as to approach the side plate  120  from the point to the base, as illustrated in  FIG. 3A , in the first step of making the end effector  70  hold the pipette  20  and the tip  30  attached thereto. However, the invention is not limited thereto. More specifically, in the first step, the axis direction of the tip  30  attached to the pipette  20  may be tilted by a predetermined angle with respect to the vertical direction so as to get away from the side plate  120  from the point to the base, or the axis direction of the tip  30  attached to the pipette  20  may extend along the vertical direction. 
     In the above embodiments, the description is given of the case where the tip  30  attached to the pipette  20  is moved into the container  100  along the axis direction of the tip  30  after the axis direction of the tip  30  attached to the pipette  20  is tilted by a predetermined angle with respect to the vertical direction so as to approach the side plate  120  from the point to the base, as illustrated in  FIGS. 3A and 3B , in the second step of aspirating the liquid L into the tip  30  by dipping at least the point of the tip  30  attached to the pipette  20  in the liquid L. However, the invention is not limited thereto. More specifically, the tip  30  attached to the pipette  20  may be moved into the container  100  along the axis direction of the tip  30  after the axis direction of the tip  30  attached to the pipette  20  is tilted by a predetermined angle with respect to the vertical direction so as to get away from the side plate  120  from the point to the base. Alternatively, the tip  30  attached to the pipette  20  may be moved into the container  100  along the axis direction of the tip  30  after the axis direction of the tip  30  attached to the pipette  20  is set so as to extend along the vertical direction. Alternatively, the tip  30  attached to the pipette  20  may be moved into the container  100  in a direction that does not follow the axis direction of the tip  30 . 
     In the above embodiments,  FIGS. 3A to 4B , and the like illustrate the case where the bottom plate  110  of the container  100  is placed along the horizontal plane. However, the invention is not limited thereto. For example, the bottom plate  110  may be placed on an inclined plane that is tilted downward toward the side plate  120 . Thus, the liquid L is accumulated in the vicinity of the connection between the bottom plate  110  and the side plate  120 . Therefore, even when the amount of the liquid L is reduced, the pipette  20  and the tip  30  attached thereto can easily aspirate the liquid L. Accordingly, the liquid L in the container  100  can be used up to the last drop. Note that, in such a case, it may be preferable that the axis direction of the tip  30  extend along the vertical direction or be tilted by a predetermined angle with respect to the vertical direction so as to get away from the side plate  120  from the point to the base. Thus, the point of the tip  30  can be moved to the connection between the bottom plate  110  and the side plate  120  without getting hindered by the side plate  120 . As a result, the advantageous effects described above can be surely achieved. 
     In the above embodiments, the description is given of the case where the end effector  70  holds the 8-channel pipette  18 . However, the invention is not limited thereto. More specifically, the end effector  70  may hold a single-channel pipette (or one pipette  20 ) or may hold a multi-channel pipette other than the 8-channel pipette (that is, a multi-channel pipette with two to seven channels or a multi-channel pipette with nine or more channels). The robot system  10  may include the tip or tips  30  corresponding to the one pipette  20  or the number of channels (that is, pipettes  20 ) included in the multi-channel pipette. 
     In the above embodiments, the description is given of the case where the robot arm  60  is the multi-joint arm with a six-axis structure. However, the invention is not limited thereto. More specifically, the robot arm  60  may be a multi-joint arm with at least one axis or may be a multi-joint arm with a seven-axis structure. Alternatively, the robot arm  60  may be an arm with a linear-motion axis. 
     The invention includes other embodiments in addition to the above-described embodiments without departing from the spirit of the invention. The embodiments are to be considered in all respects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. Hence, all configurations including the meaning and range within equivalent arrangements of the claims are intended to be embraced in the invention.