SEARCH Articles Figures Tables In situ synthesis of DNA probes on a silicon substrate. An example of a 3 X 3 array is shown in which 3-mers are synthesized in three different locations of the array. Defined locations on the surface of a silicon wafer are activated via a photolithography process using a mask, and subsequently exposed to an activated nucleic acid nucleotide which bears at the same time a photoactivatable protection group for further coupling reactions. With each exposure step a new nucleotide can be synthesized into a defined location. [Publishers Imprint]