1. AFM cantilever as load sensor Figure S-1 shows the shape of the AFM cantilever used in the buckling tests. As can be seen from Fig. S-1(a), there are two long and two short cantilevers aligned on one side. In our experiments, NWs were pushed against the long cantilever, as shown in Fig. S-1(b). The deflection can be measured with the neibouring long cantilever as a reference. A similar setup was used for the tension tests.