Cyclic Ketene Acetals as Additives for the Formulation of Subtractive Manufacturing Resists

Direct laser writing (DLW) is an innovative technology based on two-photon polymerization processes which allow the 3D printing of architectures with arbitrary complexity at the (sub)micrometer scale. As such, this platform is becoming increasingly appealing for the fabrication of MEMS, metamaterials, and functional surfaces. While most of the research interest in this field relies on additive manufacturing, subtractive approaches can be extremely helpful in nano/microfabrication, allowing the preparation of expendable scaffolds, repleceable parts, and protection for fragile structures. In this study, we show that the simple addition of cyclic ketene acetal compounds to a series of different acrylate-based photoresists results in functional formulations that allow the 3D-printing of degradable poly(ester-co-acrylate) microsctrucutres via DLW. These latter could be degraded reliably under mild conditions compatible with other photoresists and materials of common use in the fabrication of MEMS, thus opening new opportunities to design novel fabrication procedures. In particular, we show the potential of these photoresists in the fabrication of shadowing masks on 3D objects and their selective degradation employing a photobase.