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Fabrication of high-aspect-ratio polymer microstructures and hierarchical textures using carbon nanotube composite master molds
Davor Copic, Sei Jin Park, Sameh Tawfick, Michael F. L. De Volder, and A. John Hart. Lab on a Chip 11(10):1831-1837, 2011. [http://dx.doi.org/10.1039/c0lc00724b] [PDF] Scalable and cost effective patterning of polymer structures and their surface textures is essential to engineer material properties such as liquid wetting and dry adhesion, and to design artificial biological…
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Fabrication and electrical integration of robust carbon nanotube micropillars by self-directed elastocapillary densification
M. De Volder, S.J. Park, S. Tawfick, A.J. Hart. Journal of Micromechanics and Microengineering 21:045033, 2011. [http://dx.doi.org/10.1088/0960-1317/21/4/045033] [PDF] Vertically aligned carbon nanotube (CNT) ‘forest’ microstructures fabricated by chemical vapor deposition (CVD) using patterned catalyst films typically have a low CNT density per unit area. As a result, CNT forests have poor bulk properties and…
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Sameh Tawfick receives Rackham Predoctoral Fellowship
March 2011: Sameh Tawfick receives a Rackham Predoctoral Fellowship, and the Michigan Ivor K. McIvor Award for outstanding research and scholarship in applid mechanics.
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Multidirectional hierarchical nanocomposites made by carbon nanotube growth within layer-by-layer assembled films.
J. Li, S. Srivastava, J.G. Ok, Y. Zhang, M. Bedewy, N.A. Kotov, A.J. Hart. Chemistry of Materials 23:1023-1031, 2011. [http://dx.doi.org/10.1021/cm1030443] [PDF] We demonstrate fabrication of multidirectional and hierarchical carbon nanotube (CNT) films on diverse substrates, using nanocomposite catalyst films prepared by layer-by-layer (LBL) assembly. CNT density and yield are controlled by the thickness of a…
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Carbon nanotube composite optoacoustic transmitters for strong and high frequency ultrasound generation
H.W. Baac, J.G. Ok, H.J. Park, T. Ling, S.L. Chen, A.J. Hart, L.J. Guo. Applied Physics Letters 97:234104, 2010. [http://dx.doi.org/10.1063/1.3522833] [PDF] We demonstrate carbon nanotube (CNT) composite-based optoacoustic transmitters that generate strong and high frequency ultrasound. The composite consists of CNTs grown on a substrate, which are embedded in elastomeric polymer used as an acoustic…
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Multiple alkynes react with ethylene to enhance carbon nanotube synthesis, suggesting a polymerization-like formation mechanism
D.L. Plata*, E.R. Meshot* (*equal contribution), C.M. Reddy, A.J. Hart, P.M. Gschwend. ACS Nano 4(10):7185-7192, 2010. [http://dx.doi.org/10.1021/nn101842g] [PDF] Thermal treatments of feedstock gases (e.g., C2H4/H2) used during carbon nanotube (CNT) synthesis result in the formation of a complex mixture of volatile organic compounds and polycyclic aromatic hydrocarbons. Some of these are likely important CNT…
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Bending of nanoscale filament assemblies by elastocapillary densification
Z. Zhao, S. Tawfick, S.J. Park, M. De Volder, A.J. Hart, W. Lu. Physical Review E 82:041605, 2010. [http://dx.doi.org/10.1103/PhysRevE.82.041605] [PDF] We report a mechanism by which nanoscale filaments self-assemble into asymmetric aggregates by elastocapillary action. Specifically, capillary rise of liquid into an asymmetric pattern of vertically aligned filaments causes the filaments to deflect laterally…
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Precursor gas chemistry determines the crystallinity of carbon nanotubes synthesized at low temperature
G.D. Nessim, M. Seita, D.L. Plata, K.P. O’Brien, A.J. Hart, E.R. Meshot, C.M. Reddy, P.M. Gschwend, C.V. Thompson. Carbon 49(3):804-810, 2011. [http://dx.doi.org/10.1016/j.carbon.2010.10.018] [PDF] Despite significant progress in carbon nanotube (CNT) synthesis by thermal chemical vapor deposition (CVD), the factors determining the structure of the resulting carbon filaments and other graphitic nanocarbons are not well…
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John Hart will receive a FY2011 AFOSR Young Investigator (YIP) award
October 2010: John Hart will receive a FY2011 AFOSR Young Investigator (YIP) award.
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Characterizing the failure processes that limit the storage of energy in carbon nanotube springs under tension
F.A. Hill, T.F. Havel, A.J. Hart, C. Livermore. Journal of Micromechanics and Microengineering 20:104012, 2010. [http://dx.doi.org/10.1088/0960-1317/20/10/10401] [PDF] We report measurements of the mechanical properties and energy storage capabilities of carbon nanotube (CNT) springs under tensile loading, including correlated measurements of their cyclic loading and electrical resistance behavior. Tests are conducted on fibers of multi-walled…