Oligo Synthesis with Inkjet Printing

The phosphoramidite method is sensitive to humidity. Thus, before synthesis began, N₂ or Ar gas was introduced into the OpenIDS to eliminate humidity and air. When charging the dT and activator into the printhead, the reagents should not come into contact with moisture. To prevent any such contact, 3D printed peristaltic pumps were used to deliver the dT and activator reagent into the inkjet head in an enclosed state. Nozzles in the head must be filled with enough solution, with no empty space or bubbles. Every synthesis step proceeded in the enclosed synthesizer, and low humidity was maintained throughout all steps. the reading values of digital hygrometers surge due to the vaporized dichloromethane during synthesis. So, we used an analog hygrometer. we filled synthesizer with excess Argon gas until reaching the minimum reading value. We then synthesized while injecting excess Argon gas to prevent humidity increase during the synthesis process.
Each cycle of synthesis includes (1) coupling, (2) oxidation, (3) coupling, (4) oxidation, (5) detritylation. Between each step, a 10-second wash is included. Coupling, oxidization and detritylation steps were carried out for 2 min each. For improved synthesis yield, coupling in the first cycle was conducted for 5 min. At each step, 3 ml of oxidation solution and detritylation solution were used. For the wash step, 10 ml of ACN was used per step. The capping step was omitted to save time and simplify the synthesis protocol.
After the synthesis was completed, a solution containing the oligos was obtained from the substrate via ammonia cleavage. The ammonia was spread on the substrate and incubated in a 50-ml conical tube at 60 °C for 6 h. The ammonia was then removed through butanol precipitation of the solution, and the oligos were collected and dried in a desiccator. After drying, they could be used for analysis.