Alignment of liquid crystals using submicrometer periodicity gratings

Flanders, D. C.; Shaver, David C.; Smith, Henry I.

doi:10.1063/1.89864

Cited by 117 publications

(38 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[7] In the late 1970s, with progress in lithography, studies of topography-induced orientation in crystalline materials, including inorganic crystals such as potassium chloride, silicon, and germanium, as well as liquid crystals, were carried out by Smith's group. [8][9][10][11][12] For example, a 1D amorphous surface-relief template was used to preferentially align the <100> direction of silicon parallel to the grooves following recrystallization from the melt. Preferential crystallographic alignment resulting from surface patterning was named "graphoepitaxy" to distinguish its mechanism from "epitaxy", where the assembling units are guided by the chemical forces arising from a nominally flat crystalline substrate having the same characteristic periodicities as the crystalline sample.…”

Section: Tsa Phenomena In Crystalline Materialsmentioning

confidence: 99%

Templated Self‐Assembly of Block Copolymers: Top‐Down Helps Bottom‐Up

et al. 2006

View full text Add to dashboard Cite

One of the key challenges in nanotechnology is to control a self‐assembling system to create a specific structure. Self‐organizing block copolymers offer a rich variety of periodic nanoscale patterns, and researchers have succeeded in finding conditions that lead to very long range order of the domains. However, the array of microdomains typically still contains some uncontrolled defects and lacks global registration and orientation. Recent efforts in templated self‐assembly of block copolymers have demonstrated a promising route to control bottom‐up self‐organization processes through top‐down lithographic templates. The orientation and placement of block‐copolymer domains can be directed by topographically or chemically patterned templates. This templated self‐assembly method provides a path towards the rational design of hierarchical device structures with periodic features that cover several length scales.

show abstract

Section: Tsa Phenomena In Crystalline Materialsmentioning

confidence: 99%

Templated Self‐Assembly of Block Copolymers: Top‐Down Helps Bottom‐Up

et al. 2006

View full text Add to dashboard Cite

show abstract

“…[7] Although UHV methods and methods of micro-and nanofabrication provide a range of potentially useful surface structures for biological assays based on liquid crystals, the equipment needed to fabricate these structures is not widely accessible to biochemical laboratories. In addition, when using conventional materials for semiconductor fabrication, it is not easy to design surfaces that possess the needed nanometerscale structure as well as present appropriate surface functional groups that inhibit non-specific adsorption of proteins and bind target proteins.…”

mentioning

confidence: 99%

Rubbed Films of Functionalized Bovine Serum Albumin as Substrates for the Imaging of Protein-Receptor Interactions Using Liquid Crystals

Kim

Abbott²

2001

Adv. Mater.

View full text Add to dashboard Cite

“…Understanding and controlling defects in LCs are important to many technological applications (e.g., displays and optical switches). Because the defects are considered to be anomalies in the LC structure, general efforts have been directed at minimizing or annealing the defects, including by using microstructures (grooves and gratings) (6)(7)(8). However, defect domains possess unique rheological and optical properties, which could potentially be exploited to make novel materials.…”

mentioning

confidence: 99%

Ordered patterns of liquid crystal toroidal defects by microchannel confinement

Choi

Pfohl

Zhang

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

105

113

View full text Add to dashboard Cite

In this article we present experimental results demonstrating an approach to controlling the size and spatial patterning of defect domains in a smectic liquid crystal (LC) by geometric confinement in surface-modified microchannels. By confining the LC 4-octyl-4-cyanobiphenyl in m-sized rectangular channels with controlled surface polarity, we were able to generate defect domains that are not only nearly uniform in size but also arranged in quasi-2D ordered patterns. Atomic force microscopy measurements revealed that the defects have a toroidal topology, which we argue is dictated by the boundary conditions imposed by the walls of the microchannel. We show that the defects can be considered to be colloidal objects, which interact with each other to form ordered patterns. This method opens the possibility for exploiting the unique optical and rheological properties associated with LC defects to making new materials. For example, the control of the shape, size, and spatial arrangement of the defects at the mesoscale suggests applications in patterning, templating, and when extended to lyotropic LCs, a process leading to uniform-sized spherical particles for chemical encapsulation and delivery. S mectic (Sm) liquid crystals (LCs) are composed of elongated molecules that are aligned and arranged in layers. Local disruptions in the orientational, positional (layering), or morphological (bending) order in a Sm LC result in defects, which, when observed under crossed polarizers, exhibit complex textural patterns. The texture, which results from the highly anisotropic polarization of the molecules, has been extensively characterized and categorized based on the type of the LC structure (1-5). Understanding and controlling defects in LCs are important to many technological applications (e.g., displays and optical switches). Because the defects are considered to be anomalies in the LC structure, general efforts have been directed at minimizing or annealing the defects, including by using microstructures (grooves and gratings) (6-8). However, defect domains possess unique rheological and optical properties, which could potentially be exploited to make novel materials. The prerequisite for doing so would be the control of the type, size, and spatial distribution of the defects, which had not been well addressed in previous studies.In this article we present experimental results demonstrating the control of the size and spatial distribution of toroidal defects in the Sm LC 4Ј-octyl-4-cyanobiphenyl (8CB) by using surfacemodified microchannels. By changing the depth and width of the m-scale channels with a controlled surface polarity, we were able to generate focal conic defects that are not only nearly uniform in size but also arranged in 2D ordered patterns. This process is analogous to colloidal crystallization, except here the ''colloids'' are the ''soft'' m-sized defects within the LC. In addition, whereas the ordering in colloids is caused by interparticle interactions, here the defect ordering results from the competitio...

show abstract

Alignment of liquid crystals using submicrometer periodicity gratings

Cited by 117 publications

References 8 publications

Templated Self‐Assembly of Block Copolymers: Top‐Down Helps Bottom‐Up

Templated Self‐Assembly of Block Copolymers: Top‐Down Helps Bottom‐Up

Rubbed Films of Functionalized Bovine Serum Albumin as Substrates for the Imaging of Protein-Receptor Interactions Using Liquid Crystals

Ordered patterns of liquid crystal toroidal defects by microchannel confinement

Contact Info

Product

Resources

About