T.N. Eren, J. Liang, J.L.G.Schneider, M. Wegener, J. Bauer, K. Ehrmann, F. Feist, and C. Barner-Kowollik

Adv. Funct. Mater. e02876 (2025)

Abstract:

Manufacturing three-dimensional (3D) microstructures with multi-material properties via two-photon 3D laser printing (2PLP) remains a significant challenge due to restrictions inherent to conventional chain-growth photoresins. Herein, an additive- and initiator-free resin formulation is introduced that allows for the printing of 3D microstructures with disparate mechanical properties via the step-growth photopolymerization-based self-dimerization of visible-light-active ortho-methylbenzaldehydes (oMBA) within a single fabrication step in 2PLP by altering the printing parameters (i.e., laser power, scan speed). It is established that the laser exposure dose (D_exp) directly influences the material properties by varying the degree of crosslinking. While stiff materials with a Young's modulus above 1300 MPa at the higher edge of the D_exp can be produced, soft materials with a Young's modulus of < 10 MPa at the lower edge of the D_exp can also be fabricated. Thus, the herein pioneered resin offers a very broad material property window – spanning more than two orders of magnitude in Young's modulus – for multi-material printing via 2PLP, which is not achievable with conventional resins. The capabilities of the advanced resin are demonstrated by printing structures with hard and soft segments in a single fabrication step, visualizing their unique mechanical response to compression via in situ measurements.