Ink‐Jet Printing: Ink‐Jet Printed Nanoparticle Alignment Layers: Easy Design and Fabrication of Patterned Alignment Layers for Nematic Liquid Crystals (Part. Part. Syst. Charact. 2/2014)

Abstract

Ink‐jet printing of monolayer‐capped nanoparticles is introduced as a versatile and highly efficient means to pattern the alignment of nematic liquid crystals. As discussed by Torsten Hegmann and co‐workers on page 257, any homeotropic alignment patterns that can be switched by applying AC or DC electric field can quickly be created with high accuracy ranging in size from a few micron (>850 dpi) to several square inch.

A color-changing plasmonic actuator based on silver nanoparticle array/liquid crystalline elastomer nanocomposites

“…Based on these observations, it appears that the Ag NPs array layer has an obvious vertical alignment effect on mesogens similar to that seen in the previous study. 49 This behavior may be consistent with the molecular structures of oleylamine and oleic acid as ligands of Ag NPs, i.e. their long alkyl chains that are similar to those of DMOAP are assumed to induce the LC molecules to orient vertically.…”

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“…[59] Building on this strategy, we developed the patterning Au NP alignment layers by ink-jet printing. [53] This approach allows us to generate binary patterns of homeotropic or planar N-LC alignment in a continuum of either planar or homeotropic alignment provided by conventional alignment layers such as rubbed polyimides or obliquely evaporated SiO x , which should permit the design of sensor devices if the NP surface chemistry is reactive and the reaction gives rise to an LC anchoring transition.…”

“…Top glass slides were treated with a polyimide alignment layer inducing weak homeotropic anchoring conditions. In many cases, this approach reduces degenerate alignment on the opposite substrate, which leads overall to higher and more homogeneous contrast [53] -i.e. better readability of the sensor devices.…”

“…With available printing resolutions ranging from about 340 to 850 dpi, adjustable dot spacing, and overprinting patterns of practically any desired shape, form or text are easily selectable and printed with individual feature sizes as small as 30 μm if smaller (1 pL) piezoelectric print head cartridges are used. [53] Since the viscosity and surface tension of the NP ink require precise adjustment for the piezoelectric printer nozzles, the NP concentration and carrier fluid have to be adjusted (see Methods Section). Considering a specific concentration of Au NPs, the number of NP layers printed (or created by over-printing) can be reasonable precisely calculated and on average three NP layers are printed in each printing run.…”

“…The n-alkylthiolate-capped Au NPs (Figure 2a), as demonstrated previously, locally induce homeotropic anchoring conditions with anchoring energies approaching those of commercially available homeotropic polyimide alignment layers (~ 6.8 × 10 −4 J m −2 ). [53] This approach is independent of the chemical structure of the N-LC, which in other approaches was limited to cyano-or pyridine-terminated N-LCs, which can actually bind to gold surfaces. [73] After the decomposition reaction with Cl 2 gas, the residual Au remaining as layer on the SiO x -or polyimide-coated glass slide now serves locally as a planar alignment layer.…”