Pipette tip for and method of automatically maintaining pipette tip depth in a fluid during a fluid transfer operation

Abstract

A method for automatically maintaining a pipette tip depth in a conductive fluid during a fluid transfer operation, comprising the steps of: providing a pipetting device, comprising: a pipette tip; a first and a second electrode on the outer surface of the pipette tip; a frame supporting an actuator that is operatively connected to the pipette tip; and a controller that is in electrical connection with the first and second electrodes; providing a container fixed in height relative to the frame, the container holding a conductive fluid having a first liquid level; positioning the pipette tip in the container such that at least a portion of the first and second electrodes are submerged in the conductive fluid; measuring by the first and second electrodes a change in resistance relative to the conductive fluid; sending by the first and second electrodes a signal to the controller relative to the change.

1 . A method for automatically maintaining a pipette tip depth in a conductive fluid during a fluid transfer operation, comprising the steps of:
 providing a pipetting device, comprising:
 a pipette tip having a securing end with an opening, a fluid transferring end with an opening, an outer surface, and an inner surface, wherein the outer surface includes an electrically insulating material; 
 a first and a second electrode on the outer surface of the pipette tip, the first and second electrode being separated by the electrically insulating material; 
 a frame supporting an actuator that is operatively connected to the pipette tip, wherein the pipette tip is vertically oriented relative to the frame, and wherein the actuator is adapted to move the height of the pipette tip relative to the frame; and 
 a controller that is in electrical connection with the first and second electrodes; 
   providing a container fixed in height relative to the frame, the container holding a conductive fluid having a first liquid level;   positioning the pipette tip in the container such that at least a portion of the first and second electrodes are submerged in the conductive fluid, wherein the positioning step forms a control loop between the first and second electrodes, the actuator, the controller, and the conductive fluid;   measuring by the first and second electrodes a change in resistance relative to the conductive fluid;   sending by the first and second electrodes a signal to the controller relative to the change, wherein the controller is configured to command the actuator to move the pipette tip vertically in response to the signal.   
     
     
         2 . The method as recited in  claim 1 , further comprising the steps of:
 aspirating by the pipette tip an amount of the conductive fluid, wherein the conductive fluid has a second liquid level following the aspirating step;   commanding by the controller the actuator to move the pipette tip relative to the second liquid level such that the first and second electrodes remain submerged in the conductive fluid.   
     
     
         3 . The method as recited in  claim 1 , further comprising the steps of:
 dispensing by the pipette tip an amount of the conductive fluid, wherein the conductive fluid has a second liquid level following the dispensing step;   commanding by the controller the actuator to move the pipette tip relative to the second liquid level such that the first and second electrodes remain submerged in the conductive fluid.   
     
     
         4 . The method as recited in  claim 1 , further comprising the step of:
 maintaining by the control loop the pipette tip at a constant second liquid level relative to the liquid surface of the conductive fluid.   
     
     
         5 . A pipette tip, comprising:
 a body made from an electrically insulating material, the body comprising:
 an outer surface, and 
 an inner surface; 
   a first electrode disposed on the outer surface; and   a second electrode disposed on the outer surface, the second electrode being separated from the first electrode by the electrically insulating material.   
     
     
         6 . The pipette tip of  claim 5 , wherein the body further comprises:
 an apparatus securing end; and   an fluid transferring end positioned opposite the apparatus securing end, the fluid transferring end comprising a fluid transferring opening.   
     
     
         7 . The pipette tip of  claim 5 , further comprising a third electrode and a fourth electrode disposed on the inner surface. 
     
     
         8 . The pipette tip of  claims 6 , wherein each or all of the electrodes extend along a full longitudinal length of the body from the fluid transferring end to the apparatus securing end. 
     
     
         9 . The pipette tip of  claims 6 , wherein each or all of the electrodes extend a distance less than a full longitudinal length of the body from the fluid transferring end to the apparatus securing end. 
     
     
         10 . The pipette tip of  claims 5 , wherein each of the electrodes are made of copper or an electrically conductive polypropylene. 
     
     
         11 . The pipette tip of  claim 8 , wherein each electrode comprises an electrical contact tab positioned on the apparatus securing end of the electrode. 
     
     
         12 . The pipette tip of  claim 11 , wherein the electrical contact tab extends beyond the apparatus securing end of the pipette tip. 
     
     
         13 . The pipette tip of  claim 7 , wherein each or all of the electrodes extend along a full longitudinal length of the body from the fluid transferring end to the apparatus securing end. 
     
     
         14 . The pipette tip of  claim 7 , wherein each or all of the electrodes extend a distance less than a full longitudinal length of the body from the fluid transferring end to the apparatus securing end. 
     
     
         15 . The pipette tip of  claim 7 , wherein each of the electrodes are made of copper or an electrically conductive polypropylene.