We combined experimental and theoretical means to study the buckling mechanics in silicon nanowires (SiNWs) on elastomeric substrates. The system involves randomly oriented SiNWs grown using established procedures on silicon wafers, and then transferred and organized into aligned arrays on prestrained slabs of poly(dimethylsiloxane) (PDMS). Releasing the prestrain leads to nonlinear mechanical buckling processes that transform the initially linear SiNWs into sinusoidal (i.e., “wavy”) shapes. We observed for the first time that the displacements associated with these waves lie in the plane of the substrate, unlike previously observed behavior in analogous systems of silicon nanoribbons and carbon nanotubes where motion occurs out-of-plane. Theoretical analysis indicates that the energy associated with this in-plane buckling is slightly lower than the out-of-plane case for the geometries and mechanical properties that characterize the SiNWs. An accurate measurement of the Young’s modulus of individual SiNWs, between ∼170 and ∼110 GPa for the range of wires examined here. A simple strain gauge built using SiNWs in these wavy geometries demonstrates one area of potential application.
References:
S.Y. Ryu, J. Xiao, W.I. Park, K.S. Son, Y.Y. Huang, U. Paik, and J.A. Rogers, Lateral Buckling Mechanics in Silicon Nanowires on Elastomeric Substrates, Nano Letters 9, 3214-3219 (2009).
J. Xiao, S.Y. Ryu, Y. Huang, K.-C. Hwang, U. Paik and J.A. Rogers, Mechanics of nanowire/nanotube in-surface buckling on elastomeric substrates, Nanotechnology 21, 085708 (2010).