Fluidic arrays and method of using

A method of promoting interaction, comprising:

• providing a fluidic system comprising first, second and third fluid paths, wherein at least one fluid path of the fluidic system comprises a cross-sectional dimension of less than one millimeter and a first interaction material patterned therein;
• flowing at least a portion of a first fluid from a first fluid source into the first fluid path;
• partitioning portions of a second fluid from a second fluid source into each of the second and third fluid paths;
• mixing at least a portion of the first fluid with the portion of second fluid in the second fluid path to form a third fluid;
• mixing at least a portion of the third fluid with the portion of second fluid in the third fluid path to form a fourth fluid,
• wherein at least one of the first, second, third or fourth fluids comprises a second interaction material;
• and
• allowing interaction between the first and second interaction materials.