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Sub-millisecond nematic liquid crystal switches using patterned command layer
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View: Figures


Image of FIG. 1.
FIG. 1.

(a) Optical microscopy images of square pattern LCs cells with periodicity of 10 μm and square width of 4 μm, viewed in white-light transmission between crossed polarizer and analyzer and a chromatic filter with boundary lines at 0°/90° to the polarizer. The inset underlines the four stable alignment configurations. (b) Viewed with boundary lines at 45° to the polarizer. (c) and (d) represent a schematic view of the cell section when an external electric field of 0 V and 5 V is applied, respectively. The insets are the planar views of the cell when 0 V and 5 V are applied, observed with the optical microscope between crossed polarizer and analyzer without the chromatic filter.

Image of FIG. 2.
FIG. 2.

Deionized water contact angle measurements for clean ITO (blue triangle), uniform SAM-on-ITO (full squares), and patterned SAM-on-ITO surfaces (empty squares). Baked and not baked SAM CA measurements are also differently underlined with black and red symbols, respectively.

Image of FIG. 3.
FIG. 3.

Optical polarizing microscopy images of a not thermal treated (a)and a thermal treated (b) sample (square pattern 4 × 4 μm2), viewed in white light transmission between crossed polarizer and analyzer, with boundary lines at 0°/90° to the polarizer. The insets underline the alignment of a single square in both cases. The difference in resolution between the two images is related to different objective magnifications, Olympus X40 for image (a) and Nikon oil immersion 100 × for image (b).

Image of FIG. 4.
FIG. 4.

Comparison of electro-optical performances between LCs cells with SAM thermal treated (red symbols) and not (black symbols), together with patterned (crossed symbols) and not patterned (full symbols) LC cells. In detail, the average response time τoff, the relaxation time τon, and the voltage required to reach the 50% of transmission are presented.

Image of FIG. 5.
FIG. 5.

Schematic view of the distribution of the LC molecules onto a SAM patterned with only one square. LC molecules are represented by prolate spheroids aligned planarly into the SAM UV exposed square blue area, and homeotropically in the surrounding orange frame. Such LC planar organization was deduced from optical microscopy images reported in Figures 1(a) and 1(b) .

Image of FIG. 6.
FIG. 6.

(a) Transmission optical images of the switching of two different samples by applying a square wave signal (amplitude 0-5 V and frequency of 10 Hz) and illuminating with polarized white light. (a) and (a’) correspond to the square 4 × 4 μm2 pattern at 0 and 5 V and P-in at 45°; and (b)and (b’) show the square 2 × 2 μm2 pattern at 0 and 5 V and P-in at 135°. (c) The average response time τon (filled squares), relaxation time τoff (empty squares), and voltage (red circles) at 50% of transmission (V50%), as a function of the pattern size 4 × 4 μm2, 2 × 2 μm2 and 1 × 1 μm2, respectively.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Sub-millisecond nematic liquid crystal switches using patterned command layer