Standardized Material Characterization of Two-Photon Polymerized Materials on the Macroscopic Scale

Two-photon polymerization 3D printing (2PP) [1] is a powerful high-resolution manufacturing technique that covers fabrication on a broad range of dimensions, including the nano-, micro- and mesoscale. 2PP utilizes the nonlinear absorption of femtosecond laser pulses to induce cross-linking in photo-polymers with a high temporal and spatial control. By scanning a pulsed laser through a microscope objective, a photopolymer resin is cured within a distinct volume, the polymerization voxel, around the laser focal spot.[2] The dimensions of the polymerization voxel determine the achievable feature resolution as well as the throughput, which is defined as the time needed to polymerize a desired object volume. Those two characteristics show a reciprocal correlation and need to be balanced in accordance with the aimed fabrication. [3] Due to the high spatial resolution the fabrication process used to be very time consuming and typically, the overall sizes of the produced structures were within the micro-scale. However, recent advances in the field of 2PP enable an increased throughput and allow the fabrication of up-scaled objects reaching the meso- and even macro-scale while maintaining feasible processing times (Fig. 1 a).