Program Highlights

Collective Buckling of Periodic Soft Nanostructures on Surfaces

Haojing Lin, Jiashi Yang, and Li Tan
Nebraska MRSEC
and
Jie Xu and Zheng Li
Department of Mechanics and Engineering Sciences, Peking University

Mechanical instability of periodic soft nanostructure on surfaces presents a unique type of buckling problem associated with polymer-based materials. Current understanding of the phenomenon is rather limited. A key finding in this collaborative work between researchers at the Nebraska MRSEC and at the Department of Mechanics and Engineering Sciences, Peking University (H. Lin et al., J. Phys. Chem. C 111, 13348) is the discovery of multiple buckling modes associated with periodic nanostructures.
This work derives conditions for a collective instability among periodic soft nanostructures. Our theoretical model includes many interacting nanostructures on an elastic substrate. Nontrivial solutions to achieve static equilibrium for all these structures suggest multiple modes of buckling. Also, each individual case of the buckling is associated with a distinctive potential energy. A good match between experimental results and theoretical predictions validates our approximation of buckling in elastic beams with rotation of rigid ones. Furthermore, this work reports a pathway to selectively promote certain modes of nanostructure buckling and utilize for nanolithography. One typical example includes reducing feature size in a selectively buckled grating from a pitch of 200 to 130 nm. Successful demonstration of this strategy in nanolithography suggests impact to areas where both structure integrity and material flexibility are desired without compromise. Thus, the reported work should be valuable to general fields of soft lithography, device fabrication, and design of sensors and actuators.

This research is supported by the National Science Foundation, Division of Materials Research, Materials Research Science and Engineering Program, Grant 0213808.