Covalent attachment of splint oligonucleotides for molecular array generation using ligation

A method for providing an array, comprising:

• (a) irradiating a substrate comprising an unmasked first region and a masked second region, whereby a photoresist in the first region is degraded to render an oligonucleotide molecule in the first region available for ligation, whereas an oligonucleotide molecule in the second region is protected by a photoresist in the second region from ligation;
• (b) contacting the oligonucleotide molecule in the first region with (i) a first oligonucleotide comprising a first barcode sequence and (ii) a first splint comprising a photo-crosslinkable moiety, wherein the first splint hybridizes to the oligonucleotide molecule in the first region;
• (c) ligating the first oligonucleotide molecule to the oligonucleotide molecule in the first region using the first splint as a template to generate a barcoded oligonucleotide molecule in the first region, wherein the oligonucleotide molecule in the second region does not receive the first barcode sequence;
• and
• (d) irradiating the first oligonucleotide, thereby crosslinking the first splint to the barcoded oligonucleotide molecule in the first region,
• thereby providing on the substrate an array comprising oligonucleotide molecules having different sequences in the first and second regions.