Ansa Bio uses an engineered terminal deoxynucleotidyl transferase (TdT) enzyme to synthesize the oligos themselves, rather than using phosphoramidite chemistry. Each enzyme is tethered to a single nucleotide, allowing it to extend the DNA strand by exactly one base. The tether is then cleaved and the cycle repeats.

This works in aqueous solution under mild conditions and enables synthesis of much longer oligos (~1,000 bases), which can subsequently be assembled into 50 kbp constructs.

Not sure about that inkjet printer analogy.