Additive Manufacturing of Nanostructures That Are Delicate, Complex, and Smaller than Ever

Additive manufacturing with two‐photon polymerization (TPP) has opened new opportunities for the rapid fabrication of 3D structures with sub‐micrometer resolution, but there are still many fabrication constraints associated with this technique. This study details a postprocessing method utilizing oxygen‐plasma etching to increase the capabilities of TPP. Underutilized precision in the typical fabrication process allows this subtractive technique to dramatically reduce the minimum achievable feature size. Moreover, since the postprocessing occurs in a dry environment, high aspect ratio features that cannot survive the typical fabrication route can also be achieved. Finally, it is shown that the technique also provides a pathway to realize structures that otherwise are too delicate to be fabricated with TPP, as it enables to introduce temporary support material that can be removed with the plasma. As such, the proposed approach grants access to a massively expanded design domain, providing new capabilities that are long sought in many fields, including optics, biology, robotics, and solid mechanics. Subtractive post‐processing can overcome fabrication limitations of two‐photon polymerization. Two techniques are demonstrated which exploit the combination of controlled material removal with oxygen plasma etching and the geometric freedom of additive manufacturing. In the first, features are modified by the plasma to reach smaller dimensions, while in the second sacrificial material is removed to realize exceedingly delicate small scale structures.