Dispensing method and apparatus for dispensing very small quantities of fluid

An apparatus for dispensing specified volumes of fluid, the apparatus comprising:

• a fluid dispensing tip, said fluid dispensing tip being configured to contain 1 picoliter to 10 nanoliters of a sample fluid at an end, an air gap positioned above the sample fluid, and a working fluid positioned above said air gap;
• a pump adapted to maintain said working fluid in said fluid-dispensing tip and adapted to aspirate a first volume of said sample fluid into said fluid dispensing tip and expel said first volume of said sample fluid from said fluid dispensing tip;
• a metering station having an inert surface positioned to receive a drop of said sample fluid from said fluid-dispensing tip;
• means for selectively retrieving a second volume of said sample fluid from said drop on said metering station which is smaller than said first volume and dispensing said second volume of said sample fluid at a desired location;
• and
• a means for autofocussing on a drop of sample fluid being expelled from said dispensing tip.

An apparatus for dispensing specified volumes of fluid, the apparatus comprising:

• a fluid dispensing tip;
• a pump for aspirating fluid within said fluid dispensing tip, and for forcing said fluid to be dispensed from said fluid dispensing tip;
• a tape having an inert surface positioned to receive sample fluid in the form of a drop of a first volume from said fluid-dispensing tip, said tape being translatable under said fluid-dispensing tip so as to receive multiple drops of sample fluid at multiple locations;
• and
• means for selectively retrieving a second volume of said sample fluid from said drop on said metering station which is smaller than said first volume and dispensing said second volume of said sample fluid at a desired location.

A method for dispensing volumes of fluid, comprising the steps of:

• aspirating a sample fluid into a fluid dispensing tip;
• dispensing a first volume of said sample fluid onto a surface of a tape which passes under said dispensing tip to form a drop, said tape having a plurality of surfaces on which drops may be dispensed which are separated by a plurality of apertures which pass through said tape;
• aspirating a portion of said drop into said fluid dispensing tip, said portion constituting a second volume of said sample fluid which is smaller than said first volume;
• and
• extending said fluid dispensing tip through at least one perforation in said tape, and dispensing said portion from said fluid dispensing tip.