Fig. 2: Sample fabrications.

a Flow chart of the fabrication process on an Au/SiO₂/Si chip. b Camera image of a pinwheel array with area of 500 × 500 μm² before wet etching. c SEM images of i pinwheels after wet etching and ii the below SiO₂ supporters after removing the top gold with FIB (Supplementary Fig. 2g). d Schematic of 2D and deformed 3D spirals in simulations. Image sizes: 2.5 × 2.5 μm². The 2D spirals consist of four arcs with angles of (i) 180°, (ii) 270°, and (iii) 360°, respectively, which are deformed into 3D by exerting upward stresses of 3, 3, and 1 GPa in simulations. e, f SEM images of three spirals and the pinwheels after wet etching and subsequent low-dose FIB irradiation. The images agree well with simulations except the type-iii spirals, which are stuck to the bottom substrate due to the capillary force and its weak stiffness (Supplementary Fig. 3). g Top-view SEM images of 2D and deformed 3D pinwheels under V = 65 V. Corresponding side-view images are shown in Fig. 1e–f. Structural parameters: d = 300 nm in c, e, f and d = 500 nm in g. Scale bars: 1 µm.