To fill this gap, we have envisioned lactate esters as a promising source for establishing a new family of bio-based monomers for light-based 3D printing. Lactate esters are excellent candidates due to their wide availability, low toxicity 34 and low cost. Additionally, the variation of their alkyl chain length enables the tunability of material properties and their high content of ester groups allows for targeted degradation and chemical recycling/upcycling. Thus, we here propose a printable system based on lactate esters (Figure ) that implements an end-of-life strategy by choosing a crosslinking unit for the ink formulation, which can be obtained by upcycling the printed structures and then reused in a new ink formulation. Methacrylic anhydride (³ 94%, containing 2,000 ppm topanol A as inhibitor, Sigma-Aldrich); Methyl lactate (>98.0%, TCI); NaSO4 (³ 99%, Acros Organics); NaCl (99%, Honeywell Fluka); NaHCO3 (99%, Grüssing GmbH); Phenyl-bis-(2,4,6-trimethylbenzoyl)-phosphinoxid (BAPO) (97%, Sigma Aldrich). All chemicals were used as purchased without further purification unless otherwise stated. Amberlyst® 15 was washed three times with ethyl acetate and dried with air prior to its first usage and washed once with DCM after each usage.