Yusuke Goto

A novel patterning method of liquid crystal alignment by azimuthal anchoring control

A novel patterning technique of the liquid crystal (LC) alignment by controlling the azimuthal anchoring energy is proposed. The uniformly rubbed polyvinyl cinnamate (PVCi) surface is irradiated with nonpolarized UV light to increase the anchoring energy. The uniformly rubbed polyimide (PI) surface with strong anchoring is prepared as a counter alignment substrate. When the easy axes of the two substrates are perpendicular, LC molecules twist at about 90° on the PVCi surface irradiated with UV light. On the other hand, the homogeneous orientation is observed on the surface without the UV irradiation, since the anchoring is too weak to form twisted orientation.

Liquid crystal alignment surface with two easy axes induced by unidirectional rubbing

We report the liquid crystal (LC) alignment surface which has two orthogonal easy axes induced by a unidirectional rubbing treatment. When the photoreactive polymer with chalconyl sidechains is irradiated with nonpolarized UV light and subsequently rubbed with a cloth, LCs align parallel and perpendicular to the rubbing direction on the UV irradiated and nonirradiated surfaces, respectively. The polarized UV absorption of the polymer and the sign of the dichroism are measured to explain the alignment mechanism. The micropatterning of the LC alignment is successfully demonstrated through the simple process using a photomask and nonpolarized UV irradiation technique.

Patterning Properties of Liquid Crystal Alignment by Anchoring Control

A patterning method of the liquid crystal (LC) alignment by controlling a polar or an azimuthal anchoring energy of the alignment surface is proposed. The LC cell is assembled with a patterned substrate with strong and weak anchoring. We can experimentally control the azimuthal anchoring of the uniformly rubbed polyvinyl cinnamate (PVCi) surface by irradiating with a non-polarized UV light. The domain on the PVCi surface without the UV irradiation shows the homogeneous alignment of which direction is determined by the easy axis of the counter substrate, even if the easy axes of two substrates are perpendicular to each other. On the other hand, the surface with the UV irradiation shows a strong anchoring and TN orientation can be obtained in that domain.

Identification of four single-stranded DNA homopolymers with a solid-state nanopore in alkaline CsCl solution

DNA sequencing via solid-state nanopores is a promising technique with the potential to surpass the performance of conventional sequencers. However, the identification of all four nucleotide homopolymers with a typical SiN nanopore is yet to be clearly demonstrated because a guanine homopolymer rapidly forms a G-quadruplex in a typical KCl aqueous solution. To address this issue, we introduced an alkaline CsCl aqueous solution, which denatures the G-quadruplex into a single-stranded structure by disrupting the hydrogen-bonding network between the guanines and preventing the binding of the K+ ion to G-quartets. Using this alkaline CsCl solution, we provided a proof-of-principle that single-stranded DNA homopolymers of all four nucleotides could be statistically identified according to their blockade currents with the same single nanopore. We also confirmed that a triblock DNA copolymer of three nucleotides exhibited a trimodal Gaussian distribution whose peaks correspond to those of the DNA homopolymers. Our findings contribute to the development of practical DNA sequencing with a solid-state nanopore.