A methodology for two-photon polymerization micro 3D printing of objects with long overhanging structures

3D printing by two-photon polymerization (TPP) is a well-established manufacturing approach for realizing 3D polymer structures at the micro- and nanoscale. However, an important shortcoming of 3D printing by two-photon polymerization is that it is extremely challenging to print 3D objects with long overhanging features, which severely limits the application space of this technology. Here, we introduce a methodology for 3D printing by two-photon polymerization that allows the realization of 3D objects with long overhanging structures that cannot be printed using conventional printing strategies. Our methodology combines different printing approaches for realizing the overhanging structure, including locally adjusted printing block sizes and a mix of the Shell & Scaffold and Solid printing modes. As a result, objects with long overhanging parts can be printed without the need for added support structures. Using this approach, we demonstrate successful printing of overhanging cantilevers with a quadratic cross-section of 50 µm x 50 µm and lengths of up to 1000 µm. Thus, our printing modality substantially extends the capabilities and application space of 3D printing by two-photon polymerization and removes current design limitations regarding 3D printed objects with long overhanging structures.