  3D printing allows rapid fabrication of complex objects from digital designs.
One 3D-printing process, direct laser writing, polymerises a light-sensitive
material by steering a focused laser beam through the shape of the object to be
created. The highest-resolution direct laser writing systems use a femtosecond
laser to effect two-photon polymerisation. The focal (polymerisation) point is
steered over the shape of the desired object with mechanised stages or
galvanometer-controlled mirrors. Here we report a new high-resolution direct
laser writing system that employs a resonant mirror scanner to achieve a
significant increase in printing speed over galvanometer- or piezo-based
methods while maintaining resolution on the order of a micron. This printer is
based on a software modification to a commerically available resonant-scanning
two-photon microscope. We demonstrate the complete process chain from hardware
configuration and control software to the printing of objects of approximately
$400\times 400\times 350\;\mu$m, and validate performance with objective
benchmarks. Released under an open-source license, this work makes micro-scale
3D printing available the large community of two-photon microscope users, and
paves the way toward widespread availability of precision-printed devices.
