With current 2D techniques, one typically irradiates a liquid crystal film that contains added photoresponsive dye molecules, with uniform polarized light. This controls the net liquid crystal alignment via the interaction of the dye dipole and the polarization axis of light. The drawback with these systems is the need for adding strong dyes, which can discolor or degrade optical and stability properties. Thus, a dye-free method is highly desired in the engineering industry.
Currently, only two approaches to dye-free methods have been explored. The first is a two-step alignment method, in which the liquid crystal materials are coated over a very thin dye-containing photoalignment layer and then aligned or fixed by polymerization.
While this method has proven very successful in achieving stimuli-responsive 2D aligned liquid crystals and elastomers used in photonics, solar energy harvesting, microfluidics, and soft-robotic devices, it is expensive and time-consuming.
The creation of a film with microscopic arrays of microalignment patterns requires precise and dynamic control of the polarized direction of incident light in each pixel, so this method is unsuitable for aligning patterns on the nanoscale over large areas.
The second approach to the development of a dye-free system uses surface topography to overcome the limitations of conventional photoalignment. In this method, the liquid crystals are aligned over a surface topography template through lithography, nanoimprinting, or inkjet techniques among others.
While this method allows for 2D micropatterning of molecular alignment, it still requires multi-step processing, making it costly and time-consuming. Due to the surface roughness from the topographic templates, this method proves difficult in the production of thin films.
A research group led by Atsushi Shishido at Tokyo Tech has reported the development of a new method of scanning wave photopolymerization that utilizes spatial and temporal scanning of focused guided light. As the polymerization reaction proceeds, a mass flow in the film is triggered, and this results in alignment of the liquid crystals with the incident light patterns. The desired alignment is achieved through a single step by light triggered mass flow.
This new method generates arbitrary alignment patterns with fine control over larger areas in a wide variety of liquid crystal materials without the need for strong dyes or additional processing steps, something that previous methods were unable to achieve. This method has the additional advantage of unlimited complexity in 2D patterns that would, in principal, only be restricted by the light diffraction limits.
This new concept of scanning wave photopolymerization is currently limited to photopolymerizable liquid crystal systems with a thickness below tens of micrometers. However, further investigation can expand material systems that could be used such as nanorods, nanocarbons, and proteins.
Scanning wave photopolymerization can be readily introduced into existing photoproduction facilities, allowing for great economic advantages. The scientists at Tokyo Institute of Technology see this method as a powerful pathway for the simple creation of highly functional organic materials with arbitrary, fine molecular alignment patterns on the nanoscale over large areas.
Emiko Kawaguchi | EurekAlert!
DGIST achieves the highest efficiency of flexible CZTSSe thin-film solar cell
19.09.2019 | DGIST (Daegu Gyeongbuk Institute of Science and Technology)
Researchers produce synthetic Hall Effect to achieve one-way radio transmission
13.09.2019 | University of Illinois College of Engineering
How long the battery of your phone or computer lasts depends on how many lithium ions can be stored in the battery's negative electrode material. If the battery runs out of these ions, it can't generate an electrical current to run a device and ultimately fails.
Materials with a higher lithium ion storage capacity are either too heavy or the wrong shape to replace graphite, the electrode material currently used in...
To process information, photons must interact. However, these tiny packets of light want nothing to do with each other, each passing by without altering the...
Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.
The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.
At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.
Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...
Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....
19.09.2019 | Event News
10.09.2019 | Event News
04.09.2019 | Event News
20.09.2019 | Life Sciences
20.09.2019 | Life Sciences
20.09.2019 | Life Sciences