Nanoscale Assembly of Complex Structures via Harnessing of an Elastic Instability in Polymer Gels
The demand for higher density, faster speed, and lighter devices drives the need for developing inexpensive fabrication tools that create ever more complex patterns with smaller features . Many current fabrication techniques rely upon top-down processes; Nature, on the other hand, provides us with examples of intrinsic, bottom-up effects from the phyllotactic growth of plants, to animal stripes, and to fingerprints. In those systems, instabilities, packing constraints, and simple geometries drive the formation of delicate, detailed, and beautiful patterns. Recently mechanical instabilities in soft materials, such as dewetting, swelling, and buckling, have been exploited to assemble complex patterns, to fabricate novel devices, and to provide a metrology in ultrathin film characterization . However, little is known about the spontaneous pattern formation in complex geometries, such as on curved surfaces, and on nanoscales. In addition, the lack of control over large areas has limited the realization of the full potential of such self-assembled structures.
Recently, we have developed a one-step, repeatable method for the production of functional nanoscale motifs with adjustable features, size and shape using a single elastomeric master with microscale perforations. The technology takes advantage of the elastic instability of a widely used, flexible polymer, poly(dimethylsiloxane), or PDMS, and the subsequent triggering of the pattern transformation via solvent, leading to reduction of feature sizes by a factor of ten. The resulting structural anisotropy could be used to generate anisotropic magnetic, photonic, phononic, and plasmonic properties. While the preliminary results are promising, the potential of exploiting elastic instabilities to produce large area, complex structures has only just begun to be realized.
Zhu, X., Zhang, Y., Chandra, D., Cheng, S.-C., Kikkawa, J. M. and Yang, S. *, “Two-dimensional photonic crystals with anisotropic unit cells imprinted from poly(dimethylsiloxane) membranes under elastic deformation”, Appl. Phys. Lett. , 2008 , 93 (16), 161911. URL
Zhang, Y. Matsumoto, E. A., Peter, A., Lin, P., Kamien, R. D.*, and Yang, S.*, “One-step nanoscale assembly of complex structures via harnessing of an elastic instability”, Nano Lett. 2008 , 8 (4), 1192-1196. DOI.