The present teachings provide a fluid processing device adapted to produce different oligomers in a plurality of respective reaction sites. The fluid processing device can comprise a first manifold for delivering reactants to the plurality of reaction sites, and a second manifold for removing waste from, and optionally delivering wash fluid to, the plurality of reaction sites. Surface tension control valves can be disposed in fluid communication with the first manifold and can selectively allow reactants and/or fluids into the reaction sites. A method of making oligonucleotides is also provided.