Abstract:
In order to provide a method for collecting a droplet attached on an external surface of a needle into a capillary tube, the present invention is a method for collecting a droplet attached on an external surface of a needle into a capillary tube, the method comprising steps of: (a) preparing a substrate comprising a capillary tube; a flexible thin film; a liquid-repellent film; and a hole; (b) moving the needle in the Z-direction to move the droplet from the external surface of the needle to the surface of the liquid-repellent film; (c) allowing the droplet to arrive at an inlet of the capillary tube by moving the needle more in the Z-direction, so as to suck the droplet into the capillary tube by a capillary phenomenon.

Description:
This is a continuation of International Application No. PCT/JP2012/004912, with an international filing date of Aug. 2, 2012, which claims priority of Japanese Patent Application No. 2012-044960, filed on Mar. 1, 2012, the contents of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a method for collecting a droplet attached on an external surface of a needle into a capillary tube. 
     BACKGROUND ART 
     Patent Literature 1 discloses a method for attaching a very small amount (e.g., 1 microliter) of a condensate on an external surface of a needle by an electrostatic atomizing method. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Publication No. 4620186 (Family: U.S. Pat. No. 8,056,395) 
     SUMMARY OF INVENTION 
     The purpose of the present invention is to provide a method for collecting a droplet attached on an external surface of a needle into a capillary tube. 
     The present invention is a method for collecting a droplet  206  attached on an external surface of a needle  107  into a capillary tube  80 , the method comprising steps of: 
     (a) preparing a substrate  14  comprising: 
     a capillary tube  80 ; 
     a flexible thin film  95 ; 
     a liquid-repellent film  96 ; and 
     a hole  100 ; wherein 
     the substrate  14  comprises the capillary tube  80  on the surface thereof or in the inside thereof; 
     the longitudinal direction of the capillary tube  80  is parallel to a surface of the substrate  14 ; 
     the liquid-repellent film  96  is formed on the flexible thin film  95 ; 
     the liquid-repellent film  96  and the flexible thin film  95  has widths WA and WB, respectively, when viewed in a cross-sectional view which appears by cutting the substrate  14  along a Z-direction; 
     the Z-direction represents a normal direction of the substrate  14 ; 
     the widths WA and WB satisfy the following relationship (I):
 
WA≦WB  (I);
 
     the hole  100  is formed in the Z-direction; 
     an upper end of the hole  100  is covered by the liquid-repellent film  96  and the flexible thin film  95 ; and 
     (b) moving the needle  107  in the Z-direction in such a manner that the needle  107  penetrates the liquid-repellent film  96  and the flexible thin film  95  in this order, so as to move the droplet  206  from the external surface of the needle  107  to the surface of the liquid-repellent film  96 ; wherein 
     the droplet which has been disposed on the surface of the liquid-repellent film  96  has a width WL in the cross-sectional view; and 
     (c) allowing the droplet  206  which has been disposed on the surface of the liquid-repellent film  96  in the step (b) to arrive at an inlet of the capillary tube  80  by moving the needle  107  more in the Z-direction with an increase of the width WL, so as to suck the droplet  206  into the capillary tube  80  by a capillary phenomenon. 
     The substrate  14  may comprise the capillary tube  80  in the inside thereof: 
     the substrate  14  may be composed of a first plate  14   a , a second plate  14   b , and a third plate  14   c;    
     the second plate  14   b  may be interposed between the first plate  14   a  and the third plate  14   c;    
     a slit or a groove  88  may be formed on the second plate  14   b ; and 
     the capillary tube  80  may be formed of the slit or the groove  88 . 
     The flexible thin film  95  may be interposed between the first plate  14   a  and the second plate  14   b ; and 
     the flexible thin film  95  may be disposed not only at the upper end of the hole  100  but also in the inside of the capillary tube  80 . 
     The second plate  14   b  may comprise a first through-hole  87   a;    
     the first through-hole  87   a  may overlap with the liquid-repellent film  96  and with the hole  100 ; 
     a cross-sectional area of the first through-hole  87   a  may be greater than an area of the liquid-repellent film  96 ; 
     the third plate  14   c  may comprise a second through-hole  87   b ; and 
     the second through-hole  87   b  may overlap with the first through-hole  87   a , the liquid-repellent film  96 , and the hole  100 . 
     The first through-hole  87   a  may have a width WC in the cross-sectional view; 
     the widths WA and WC satisfies the following relationship (II);
 
WA≦WC  (II);
 
     the liquid-repellent film  96  may be not disposed in the inside of the capillary tube  80 ; and 
     the flexible thin film  95  may comprise a hydrophilic surface, except for a portion where the liquid-repellent film  96  is formed. 
     The area of the first through-hole  87   a  may be equal to the area of the second through-hole  87   b.    
     The flexible thin film  95  may have the same area as the first plate  14   a.    
     The flexible thin film  95  may have a smaller area than the first plate  14   a.    
     The substrate  14  may comprise the capillary tube  80  on the surface thereof. 
     The capillary tube  80  may be a glass tube or a plastic tube. 
     A ring surrounding the liquid-repellent film  96  may be provided on the surface of the substrate  14 ; and 
     the capillary tube  80  may be inserted in the ring  99 . 
     An inlet of the capillary tube  80  may be located at a portion of an internal wall of the ring  99 . 
     The flexible thin film  95  may comprise a hydrophilic surface, except for a portion where the liquid-repellent film  96  is formed. 
     The droplet  206  may be an aqueous solution. 
     The droplet  206  contains a chemical substance; and 
     the substance contained in the droplet  206  which has been collected in the inside of the capillary tube  80  may be detected optically or electrochemically after the step (c). 
     The droplet  206  may be an aqueous solution containing the chemical substance. 
     The present invention provides a method for collecting the droplet which attached to the outer surface of the needle in a capillary. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a substrate  14  according to the embodiment 1. 
         FIG. 2  shows an exploded view of the substrate  14  according to the embodiment 1. 
         FIG. 3  shows a cross-sectional view of A-A line included in  FIG. 1 . 
         FIG. 4  shows a variation of  FIG. 2 . 
         FIG. 5  shows a variation of  FIG. 3 . 
         FIG. 6  shows a substrate  14  according to the embodiment 2. 
         FIG. 7  shows a variation of  FIG. 6 . 
         FIG. 8  shows a schematic diagram of the step (b). 
         FIG. 9  shows a schematic diagram of the step (b), subsequently to  FIG. 8 . 
         FIG. 10  shows an inappropriate example. 
         FIG. 11  shows a schematic diagram of the step (c). 
         FIG. 12  shows a schematic diagram of the step (c), subsequently to  FIG. 11 . 
         FIG. 13  shows a schematic diagram of the step (c), subsequently to  FIG. 12 . 
         FIG. 14  shows a movement of the droplet  206  on the flexible thin film  95  having a hydrophilic surface according to the embodiment 1. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The embodiment of the present invention is described below with reference to the drawings. 
     Embodiment 1 
     (Step (a)) 
     First, a substrate  14  is prepared. 
       FIG. 1  shows the substrate  14 .  FIG. 2  shows an exploded view of the substrate  14 .  FIG. 3  shows a cross-sectional view of A-A line included in  FIG. 1 . 
     As shown in  FIG. 1  to  FIG. 3 , this substrate  14  comprises a first plate  14   a , a second plate  14   b , and third plate  14   c.    
     A flexible thin film  95  is interposed between the first plate  14   a  and the second plate  14   b.    
     The first plate  14   a  comprises a hole  100 . This hole  100  has a central axis parallel to the normal direction of the substrate  14 , namely, Z-direction in  FIG. 1 . 
     The flexible thin film  95  comprises a liquid-repellent film  96  on the surface thereof. The upper end of the hole  100  is covered by the flexible thin film  95 . Accordingly, the area of the flexible thin film  95  is greater than the cross-sectional area of the hole  100 . To be more exact, the phrase “cross-sectional area of the hole  100 ” means a cross-sectional area of the hole  100  which appears by cutting the substrate  14  along the direction perpendicular to the Z-direction. The detail of the liquid-repellent film  96  is described later. It is desirable that the hole  100  is a through-hole. However, the hole  100  may comprise a bottom. As described above, the liquid-repellent film  96  overlaps with the hole  100 . The area of the liquid-repellent film  96  may be greater or smaller than the cross-sectional area of the hole  100 , and may be equal to the cross-sectional area of the hole  100 . The liquid-repellent film  96  is located at the upper end of the hole  100  through the flexible thin film  95 . 
     As shown in  FIG. 3 , the liquid-repellent film  96  and the flexible thin film  95  has a width WA and a width WB, respectively, in the cross-sectional view which appears by cutting the substrate  14  along the Z direction. The width WA and the width WB satisfy the following formula (I).
 
WA≦WB  (I)
 
     It is desirable to satisfy the following formula (Ia).
 
WA≦WB  (Ia)
 
     The second plate  14   b  comprises a first through-hole  87   a  and a slit  88 . One end of the slit  88  is communicated with the side of the first through-hole  87   a . It is desirable that the cross-sectional area of the first through-hole  87   a  is greater than the area of the liquid-repellent film  96 . The phrase “cross-sectional area of the first through-hole  87   a ” means a cross-sectional area of the first through-hole  87   a  which appears by cutting the substrate  14  along the direction perpendicular to the Z-direction. The first through-hole  87   a  overlaps with the liquid-repellent film  96  and the hole  100 . Instead of the slit  88 , the second plate  14  may comprises a groove. 
     The third plate  14   c  comprises a second through-hole  87   b . The second through-hole  87   b  overlaps with the first through-hole  87   a , the liquid-repellent film  96 , and the hole  100 . It is desirable that the area of the second through-hole  87   b  is equal to the area of the first through-hole  87   a . The third plate  14   c  comprises an air hole  36 . 
     As shown in  FIG. 2 , it is desirable that the first plate  14   a , the flexible thin film  95 , the second plate  14   b , and the third plate  14   c  have the same size. 
     It is desirable that the flexible thin film  95 , the second plate  14   b , and the third plate  14   c  are laminated on the first plate  14   a  in this order to form the substrate  14 . In this way, the capillary tube  80  is formed in the inside of the substrate  14  with the slit  88 . One end of the slit  88  forms the inlet of the capillary tube  80 . As is clear from  FIG. 1 , this capillary tube  80  is parallel to the surface of the substrate  14 . 
       FIG. 4  and  FIG. 5  show a variation of the substrate  14 . As shown in  FIG. 4  and  FIG. 5 , the flexible thin film  95  may have a smaller size than any of the first plate  14   a  to the third plate  14   c . Anyway, the flexible thin film  95  covers the upper end of the hole  100  completely. In  FIG. 4  and  FIG. 5 , the formula (I) is also satisfied. It is desirable that the formula (Ia) is satisfied. 
     In  FIG. 4  and  FIG. 5 , the small flexible thin film  95  having the liquid-repellent film  96  on the surface thereof is affixed to the first plate  14   a  in such a manner that the small flexible thin film  95  covers the upper end of the hole  100  completely. Subsequently, the second plate  14   b  and the third plate  14   c  are laminated on the first plate  14   a  in this order. In  FIG. 4  and  FIG. 5 , the liquid-repellent film  96  is also located at the upper end of the hole  100 . 
     Alternatively, after the second plate  14   b  and the third plate  14   c  are laminated on the first plate  14   a  in this order, the small flexible thin film  95  having the liquid-repellent film  96  on the surface thereof is affixed to the first plate  14   a  through the first through-hole  87   a  and the second through-hole  87   b . In this way, the upper end of the hole  100  may be covered by the flexible thin film  95 . 
     It is desirable that the liquid-repellent film  96  is not disposed in the inside of the capillary tube  80 . This is because the liquid-repellent film  96  placed in the inside of the capillary tube  80  prevents the droplet  206  which has arrived at the inlet of the capillary tube  80  from being sucked into the inside of the capillary tube  80 . 
     Except for the portion where the liquid-repellent film  96  is formed, it is desirable that the flexible thin film  95  has a hydrophilic surface. This is because the flexible thin film  95  having the hydrophilic surface promotes the collection of the droplet  206  into the inside of the capillary tube  80 . See  FIG. 14 . It is more desirable that the flexible thin film  95  located in the inside of the capillary tube  80  has a hydrophilic surface. 
     (Detail of the Liquid-Repellent Film  96 ) 
     The liquid-repellent film  96  may be composed of a fluoroalkyl group formed on the flexible thin film  95  having a hydrophilic property. In more detail, fluoroalkyl trialkoxy silane or fluoroalkyl trihalogened silane is supplied to the flexible thin film  95  having hydroxyl groups so as to form such a liquid-repellent film  96  on the flexible thin film  95 . An example of the flexible thin film  95  is a rubber film. 
     It is desirable that the liquid-repellent film  96  has a contact angle of not less than 90 degrees and not more than 110 degrees. It is desirable that the flexible thin film  95  has a contact angle of not less than 0 degrees and not more than 30 degrees. The term “contact angle” used in the instant specification means a contact angle with respect to water. 
     (Step (b)) 
     The step (b) is performed after the step (a). 
     In the step (b), as shown in  FIG. 8 , a needle  107  having a droplet  206  on the external surface thereof is moved in the Z direction so that the needle  107  penetrates the liquid-repellent film  96  and the flexible thin film  95 . In this way, a through-hole  91  penetrating the flexible thin film  95  is formed by the needle  107 . The flexible thin film  95  is pushed and bent in the Z direction by needle  107 . 
     As shown in  FIG. 9 , when the needle  107  is moved in the Z direction more, the droplet  206  is attached to the liquid-repellent film  96 . The droplet  206  which has attached to the liquid-repellent film  96  has a width WL. Here, the term “width” means a width of droplet  206  which appears by cutting the substrate  14  in the Z-direction. 
     If the substrate  14  does not have the liquid-repellent film  96 , as shown in  FIG. 10 , the droplet  206  leaks from an interspace formed between the through-hole  91  and the needle  107 . Therefore, the liquid-repellent film  96  is necessary. 
     In  FIG. 9 , a point of the needle  107  is sharp. In other words, the cross-sectional area of the needle  107  is decreased gradually toward the point thereof. Here, the phrase “the cross-sectional area of the needle  107 ” means the cross-sectional area of the needle  107  which appears by cutting the needle  107  in the direction perpendicular to the Z-direction. 
     (Step (c)) 
     The step (c) is performed after the step (b). It is desirable that the step (c) is performed continuously after the step (b). 
     As shown in  FIG. 11 , the needle  107  is moved more in the Z-direction, and the droplet  206  is moved from the liquid-repellent film  96  to the flexible thin film  95 . In this way, the width WL is increased, and the droplet  206  arrives at the inlet of the capillary tube  80 . 
     When the droplet  206  arrives at the inlet of the capillary tube  80 , as shown in  FIG. 12 , the droplet  206  is sucked into the capillary tube  80 . In this way, the droplet  206  is collected in the inside of the capillary tube  80  by a capillary phenomenon. 
     As shown in  FIG. 13 , it is desirable that the substrate  14  comprises a first electrode  85  and a second electrode  86  which are exposed to the inner surface of the capillary tube  80 . It is desirable that the collected droplet  206  is subjected to an electrochemical analysis at the inside of the capillary tube  80  using the first electrode  85  and the second electrode  86 . In this way, a chemical substance contained in the droplet  206  is detected. Instead of the electrochemical analysis, an optical analysis may be used. 
     It is desirable that the droplet  206  is an aqueous solution containing a chemical substance. 
     It is desirable that all of the following relationships (a) to (c) are satisfied. 
     (a) The width WA of the liquid-repellent film  96  is smaller than the width WC of the first through-hole  87   a.    
     (b) The liquid-repellent film  96  is not disposed in the inside of the capillary tube  80 . 
     (c) The flexible thin film  95  has a hydrophilic surface, except for the portion of the liquid-repellent film  96 . 
     If the all of the relationships (a) to (c) are satisfied, as shown in  FIG. 14 , the droplet  206  which has been moved from the liquid-repellent film  96  to the flexible thin film  95  moves along the internal peripheral wall of the first through-hole  87  on the flexible thin film  95 , so as to arrive at the inlet of the capillary tube  80 . In this way, the droplet  206  can be collected more into the capillary tube  80 . In  FIG. 14 , note that the third plate  14   c  is not illustrated. 
     Embodiment 2 
     As shown in  FIG. 6 , the capillary tube  80  may be formed on the surface of the substrate  14  without using the first, second, and third plates  14   a  to  14   c . An example of this capillary tube  80  is a glass tube or a plastic pipe. In  FIG. 6 , the hole  100  is formed in the substrate  14 . The upper end of hole  100  is covered completely by the flexible thin film  95  having the liquid-repellent film  96  on the surface thereof. 
     It is desirable that a ring  99  is provided on the surface of the substrate  14  or the surface of the flexible thin film  95 . Similarly to the description about  FIG. 14 , the droplet  206  which has been moved from the liquid-repellent film  96  to the flexible thin film  95  moves along the internal wall of the ring  99  on the flexible thin film  95  and arrives at the inlet of the capillary tube  80 . 
     The capillary tube  80  is inserted in the ring  99 . It is desirable that the inlet of the capillary tube  80  is formed at a portion of the internal wall of the ring  99 . 
     In  FIG. 6 , the small flexible thin film  95  having the liquid-repellent film  96  on the surface thereof is affixed to the surface of the substrate  14  so as to cover the hole  100  completely. Instead of  FIG. 6 , as shown in  FIG. 7 , the flexible thin film  95  may have the same size as the substrate  14 . 
     As one example, it is desirable that the liquid-repellent film  96  has a shape of a circle. 
     It is desirable that the first through-hole  87   a  has a shape of a circle. It is desirable that the second through-hole  87   b  is the same as the first through-hole  87   a.    
     It is more desirable that the needle  107  has a shape of an inverted corn. 
     It is desirable that the needle  107  penetrates the center of the circular liquid-repellent film  96 . 
     INDUSTRIAL APPLICABILITY 
     The present invention provides a method for collecting a droplet attached on an external surface of a needle into a capillary tube. 
     REFERENCE MARK IN THE DRAWINGS 
     
         
         
           
               14  substrate 
               14   a  first plate 
               14   b  second plate 
               14   c  third plate 
               80  capillary tube 
               87   a  first through-hole 
               87   b  second through-hole 
               88  slit or groove 
               99  ring 
               95  flexible thin film 
               96  liquid-repellent film 
               100  hole 
               107  needle 
               206  droplet