ribbon in a spatially invariant periodic geometry (2 μm thick, 50 μm wide; schematic top-view illustration in the upper panel of Fig. 1B). Here, selective bonding to an assembly platform that is strained uniaxially to εpre = 90% yields a uniform, single-helical coil (Fig. 1B). The experimental results are in quantitative agreement with FEA (Fig. 1Band fig. S4) and with analytical parametric equations developed by exploring key characteristics of the deformations (33) (fig. S5). Such models establish the relationship between geometric configurations and εpre, indicating that the heights of the helices increase with εpre while the widths remain largely unchanged, as might be expected. Modifying the structure of the 2D precursor within this theme while changing the distribution of the bonding sites enables access to dual helices (Fig. 1C), nested coaxial structures (Fig. 1D), helices with opposite chirality (Fig. 1E), and even structures whose chirality changes abruptly at selected locations (Fig. 1F). In all of the examples in Fig. 1, the maximum principal strains in the silicon (from ~0.34% to 0.90%) occur at locations of large