Influence of oxygen plasma on the material properties of Two-Photon polymerized microstructures

• O 2 plasma etching refines 2PL microstructures, but its impact on material properties must be considered during design. • O 2 plasma increases roughness, material stiffening and promotes hydrophilicity. O 2 plasma exposure is a convenient postprocessing method for refining 3D microstructures fabricated by two-photon polymerization, which provides an effective way to achieve sub-micrometer resolution with remarkable feature control. Unlike pyrolysis, which despite being a widespread methodology to decrease feature size, it alters the properties of the bulk material, O 2 plasma etching primarily modifies the surface. In this work, we explore the influence of plasma etching treatments on the material properties of 3D microstructures. We examine the resulting modifications to key parameters relevant to various applications: surface roughness, mechanical properties, and material composition. Our findings reveal a two-stage effect: low exposure times reduce surface roughness, while prolonged exposure leads to an increase in roughness. Nanomechanical properties are strongly affected, with the Young’s modulus of the surface increasing by an order of magnitude, indicating a stiffening effect. Raman spectroscopy evidences that the observed stiffening is not due to the formation of a carbonized layer but rather due to further crosslinking. These results highlight the need to carefully evaluate the impact of O 2 plasma etching on the final properties of 2PP microstructures when designing fabrication processes to ensure the necessary physical and chemical properties for the desired application.