Array printing

A method of introducing reagent compositions into a plurality of capillary tubes, which includes

• arranging a plurality of capillary tubes, each having at least one open end, alongside one another such that the open ends of the tubes are aligned;
• simultaneously locating the open end of each tube in its own trough, towards a first end thereof;
• and
• introducing a reagent composition into each trough and allowing it to flow along the trough to the first end thereof where it enters the capillary tube.

A printing apparatus for printing, onto a substrate, an array of spots of reagent compositions for use in chemical and/or biochemical analysis, which apparatus includes

• an array of capillary tubes arranged alongside one another and each having at least one open end, with the open ends of the tubes being aligned;
• displacement means for displacing the array of capillary tubes from an inoperative position to an operative position and back to the inoperative position;
• and
• substrate holding means for holding a substrate so that, in use, when the array of capillary tubes is displaced into its operative position, the open ends of the capillary tubes can simultaneously impinge against a substrate held by the substrate holding means with at least some reagent composition from the capillary tubes being deposited on the substrate as spots, thereby to form an array of spots of the reagent compositions on the substrate.