Apparatus and methods for liquid sample handling based on capillary action

Abstract

The present invention comprises a removable capillary tip insert which provides for replacement of an individual capillary in the dispensing head of an automated liquid handling apparatus. In some embodiments, the insert has been designed to accept variable capillary lengths while maintaining a constant length protruding from the insert. In a preferred embodiment, the removable capillary insert of the invention comprises a head adapted to accept an insertion tool and tapered to seat in the dispense head; a shaft with external threads which form a threaded collar that permits the insert to be screwed into the dispense head; a lumen running internally from the proximal to the distal ends of the head and shaft which forms a hollow interior in the insert in which a capillary resides; and a capillary tube of user-selected liquid capacity. One embodiment, without limitation, comprises a molded plastic part with an integral capillary tube. Other embodiments comprise dispensing heads with various configurations of capillary inserts and methods for automated liquid dispensing using the same.

1 . A removable capillary tip insert for an automated liquid dispensing apparatus, comprising:
 a head,   a shaft with external threads,   an internal lumen extending the lengths of the head and the shaft, and   a capillary tube joined to the distal end of the shaft.   
     
     
         2 . The insert of  claim 1 , wherein the capillary tube is joined to the distal end of the shaft by molding the shaft around a portion of the capillary tube. 
     
     
         3 . The insert of  claim 1 , wherein the head is adapted to fit a tool for insertion into a mounting block. 
     
     
         4 . The insert of  claim 1 , wherein the head is tapered on at least some portion so that the head is not of uniform diameter. 
     
     
         5 . The insert of  claim 1 , wherein the liquid capacity of the capillary tube is between 1 nanoliter and 10,000 nanoliters, inclusive. 
     
     
         6 . The insert of  claim 5 , wherein the head and shaft of the insert are comprised of polystyrene. 
     
     
         7 . The insert of  claim 5 , wherein the head and shaft of the insert are comprised of polypropylene. 
     
     
         8 . A mounting block for an automated liquid dispensing apparatus, comprising:
 one or more inserts of  claim 1 ;   a surface comprising a plurality of holes configured to accept the external threads and shapes of the inserts; and   one or more orifices for the application of air pressure to one or more of the inserts.   
     
     
         9 . The mounting block of  claim 8 , further comprising a plurality of inserts of  claim 1  in which the plurality of inserts comprise more than one color. 
     
     
         10 . The mounting block of  claim 8 , wherein the plurality of inserts are color-coded. 
     
     
         11 . The mounting block of  claim 8 , further comprising a plurality of inserts of  claim 1  wherein the plurality of inserts comprise more than two or more capillary tubes of different liquid capacity. 
     
     
         12 . A method for automated dispensing of liquid samples, comprising the steps of:
 providing the mounting block of  claim 8 ;   providing a source substrate containing one or more liquid samples;   providing a destination substrate for one or more liquid samples;   providing an automated liquid dispensing apparatus comprising:
 a dispensing head; 
 means to cycle the dispensing head between source and destination substrates; and 
 means to selectively apply air pressure to one or more of the inserts of  claim 1 ; 
   configuring the mounting block to fasten to the dispensing head; and   cycling the mounting block between the source substrate and the destination substrate,   such that a portion of one or more samples from the source substrate is taken up by one or more inserts on the mounting plate by capillary action and dispensed onto the destination substrate by selective application of air pressure to the insert.