Liquid crystal (LC) alignment layers commonly feature some type of anisotropy that induces a preferred orientation of the LC director on the surface. Unidirectionally rubbed polyimides are the most widely used [1]. Photoalignment and obliquely evaporated inorganic materials are alternative techniques that are utilized as well [2]. Although these processes have demonstrated robustness and have been implemented in large-scale production environments, they often require several fabrication steps, high processing temperatures, and sometimes, high vacuum environment.We demonstrated that doping nematic LCs with a small quantity of thiolate capped gold nanoparticles (NPs) can lead to the induction of homeotropic alignment [3]. A similar effect is achieved if NPs are deposited onto the surface before preparing sandwiched LC films between conductiove ITO-on-glass substrates. This leads to a uniform coverage of the surface with the NPs and, in turn, uniform vertical alignment of the LC over the entire area. The homeotropic anchoring of the LC molecules on the NPs is accompanied by a contrast inversion effect, i.e. under the action of a low-frequency electric field, ?e > 0 LCs effectively acts as ?e < 0 LCs and undergo a transition from the homeotropic to the planar state.To demonstrate the next level of control over NP-induced LC alignment, we established the use ink-jet printing of gold NPs to obtain full coverage as well as patterned alignment of nematic LCs as a quick, simple, highly versatile, and adaptable LC alignment technique. Striking features of the ink-jet printing process are the variability of the NPs (metal, metal chalcogenide, carbon-based), the substrates, the simplicity of pattern creation, and the scalability of the process [4].[1] (a) J. van Haaren, Nature 411 , 29-30 (2001); (b) J. Hoogboom, T. Rasing, A. E. Rowan, R. J. M. Nolte, J. Mater. Chem. 16 , 1305-1314 (2006).[2] For a recent review, see: O. Yaroshchuk, Y. Reznikov, J. Mater. Chem. 22 , 286-300 (2012).[3] (a) H. Qi, B. Kinkead, T. Hegmann, Adv. Funct. Mater. 18 , 212-221 (2008); (b) H. Qi, T. Hegmann, ACS Appl. Mater. Interf. 1 , 1731-1738 (2009); (c) M. Urbanski, B. Kinkead, H. Qi, T. Hegmann, H.-S. Kitzerow, Nanoscale 2 , 1118-1121 (2010).[4] M. Reznikov, A. Sharma, T. Hegmann, Part. Part. Syst. Charact., in press (2013).

Inkjet-printed gold nanoparticle alignment layers: A novel approach for the patterned alignment of nematic liquid crystals

247th National Meeting (2014)

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