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Nature Communications 5, Article number: 4512. 2014.
M. De Volder, S. Park, S. Tawfick, A. J. Hart.
Institute for Manufacturing, Department of Engineering, University of Cambridge, 17 Charles Babbage Road, Cambridge CB3 0FS, UK &
IMEC, Kapeldreef 75, 3001 Heverlee, Belgium &
Department of Mechanical Engineering, Katholieke Universiteit Leuven, 3001 Leuven, Belgium &
Department of Mechanical Engineering, University of Michigan, 2350 Hayward Street, Ann Arbor, Michigan 48109, USA &
Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA &
Mechanical Science and Engineering, University of Illinois at Urbana Champaign, Urbana, Illinois 61822, USA.
ABSTRACT
The skins of many plants and animals have intricate microscale surface features that give rise to properties such as directed water repellency and adhesion, camouflage, and resistance to fouling. However, engineered mimicry of these designs has been restrained by the limited capabilities of top–down fabrication processes. Here we demonstrate a new technique for scalable manufacturing of free form microstructures via strain-engineered growth of aligned carbon nanotubes (CNTs). Offset patterning of the CNT growth catalyst is used to locally modulate the CNT growth rate. This causes the CNTs to collectively bend during growth, with exceptional uniformity over large areas. The final shape of the curved CNT microstructures can be designed via finite element modeling, and compound catalyst shapes produce microstructures with multidirectional curvature and unusual self-organized patterns. Conformal coating of the CNTs enables tuning of the mechanical properties independently from the microstructure geometry, representing a versatile principle for design and manufacturing of complex microstructured surfaces.
