Fig. 1. 3D printing of silica-glass micro-structures by direct laser writing.

a Preparation of hydrogen silsesquioxane (HSQ) by drop casting. b Direct writing in the HSQ using the focus of the sub-picosecond laser beam. c Development of the 3D-printed structures by dissolving the unexposed HSQ. The inset SEM image shows a 3D-printed KTH logo (scale bar, 1 µm). d, e SEM images of 3D-printed structures: a glass goblet and a conical spiral (scale bars, 1 µm). f, g SEM images of an array of 500 nm diameter needles and of a pillar with a longitudinal twist (scale bars, 1 µm). h, i SEM images of a cantilever that is 750 nm wide and 540 nm thick taken from a 45-degree angle. The roughness on the top surface originates from a deposited gold layer for reducing charging effects during imaging (scale bars, 1 µm). j Scanning TEM image of an as-printed silica glass structure. The dark region on the bottom-left corner is the metal layer deposited during sample preparation, and the interface between the glass and metal is marked with a dashed line (scale bar, 50 nm). k Electron diffraction pattern of the TEM sample. The pattern consists of concentric rings, showing that the printed material is amorphous (scale bar, 5 nm⁻¹).