Fig. 3.

Characterization of suspended hollow microstructures in fused silica. a, b SEM of rectangular channel cross-section with an aspect ratio of 0.1 and 10 (scale: 100 µm). c–f SEM of spherical, triangular, trapezoidal, and rectangular channel cross-sections (scale: 10 µm). All templates were fabricated using direct laser writing. The flattened side of the “spherical” channel cross-section is due to the 2-photon polymerization 3D printing process of the template. Structures are printed on glass slides and a certain contact area is required to prevent the structure from detaching from the glass. g, h SEM and white light interferometry of the channel structure from a with a mean roughness of Ra ~20 nm (scale: 10 µm)