Force Output, Control of Film Structure, and Microscale Shape Transfer by Carbon Nanotube Growth under Mechanical Pressure

• Published in: Nano letters Vol. 6; no. 6; pp. 1254 - 1260
• Main Authors: Hart, Anastasios John, Slocum, Alexander H
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.06.2006
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystallization - methods; Elasticity; Exact sciences and technology; Materials science; Materials Testing; Membrane Fluidity; Membranes, Artificial; Methods of deposition of films and coatings; film growth and epitaxy; Molecular Conformation; Molecular Motor Proteins - chemistry; Nanoscale materials and structures: fabrication and characterization; Nanotechnology - methods; Nanotubes; Nanotubes, Carbon - chemistry; Nanotubes, Carbon - ultrastructure; Other topics in nanoscale materials and structures; Particle Size; Physics; Pressure; Stress, Mechanical; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of film growth; Thin film structure and morphology; Actuators; Patterning; Carbon nanotubes; Template reaction; Energy density; Thin films; Multiwalled nanotube; Three dimensional structure; Experimental design; Growth mechanism; Microstructure; Polymers; Nanostructured materials; Nanomaterial synthesis
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl0524041

We demonstrate that a film of vertically aligned multiwall carbon nanotubes (CNTs) can exert mechanical energy as it grows, and in our experiments the average force output is approximately 0.16 nN per CNT, for CNTs having an outer diameter of 9 nm and five walls. The film thickness after a fixed growth time and the alignment of CNTs within the film decrease concomitantly with increasing pressure which is applied by placing a weight on the catalyst substrate prior to growth, and CNTs grown under applied pressure exhibit significant structural faults. The measured mechanical energy density of CNT growth is significantly less than the energies of primary steps in the CNT formation process yet, based on the film volume, is comparable to the energy density of muscle and based on the volume of CNTs is comparable to hydraulic actuators. We utilize this principle to fabricate three-dimensional structures of CNTs which conform to the shape of a microfabricated template. This technique is a catalytic analogue to micromolding of polymer and metal microstructures; it enables growth of nanostructures in arbitrarily shaped forms having sloped surfaces and nonorthogonal corners and does not require patterning of the catalyst before growth.