Résumé
Nanotube-based patterns and films have exciting potential applications in electronics and optoelectronics.One of the key issues to optimize the electrical and optical properties of nanotubearrays is the control of their orientation. So far, orientation of nanotubes in thin films wasachieved i) directly during CVD growth [1], ii) using liquid dispersions: by dielectrophoresis [2],in an hydrodynamic flow [3,4], in the field of an host liquid crystal [5], by formation of a liquidcrystal in concentrated suspensions [6], or iii) by stretching composites [7]. However, versatileand industry-compatible methods are still needed, and inkjet printing appears to be a goodcandidate. Recently, Denneulin et al. reported an heterogeneous orientation of SWNT in inkjetprinted lines, with a preferential orientation parallel to the lines at the edges and perpendicularin the sub-surface [8]. On the other hand, Beyer et al. reported an homogeneous alignmentparallel to the lines for inkjet printed SWNT, and assigned it to the formation of a nematic phasefor special printing rates [9].Here, we present a coupled Raman/SEM study of the alignment of SWNT during inkjet printingof aqueous suspensions as a function of temperature, nanotube concentration and printingconditions. We report a very good alignment of the nanotubes, especially at the edges of theprinted patterns, and we discuss the contributions of hydrodynamics and thermodynamics to theorientation.References[1] K. Hata et al, Science (2004), 306, 132002 ; [2] S. Shekhar et al. ACS Nano (2011), 5, 1739; [3] C. Zamora-Ledezma et al, Nano Lett., (2008), 8 (12), 4103 ; [4] Q. Li et al, J. Phys. Chem.B (2006), 110, 13926 ; [5] N. Ould-Moussa et al, Liq. Cryst. (2013), 40, 12 ; [6] C. Zamora-Ledezma et al, Phys. Rev. E. (2011), 84, 062701 ; [7] C. Zamora-Ledezma et al, Phys. Rev. B.(2009), 80, 113407 ; [8] A. Denneulin et al, Carbon (2011), 49, 2603 ; [9] S.T. Beyer et al.Langmuir (2012), 28, 8753.