Direct ink writing of anisotropic luminescent materials

Luminescent solar concentrators are relatively inexpensive devices proposed to collect, convert, and redirect incident (sun)light for a variety of potential applications. In this work, dichroic dyes are embedded in a liquid crystal elastomer matrix and used as feedstock for direct ink writing. Direct ink writing is a promising and versatile application technique for arbitrarily aligning the dichroic dyes over glass and poly(methyl methacrylate) lightguide surfaces. The resulting prints display anisotropic edge emissions, and suggest usage as striking visual objects, combining localized color and intensity variations when viewed through a polarizer

Functionalizing the rear scatterer in a luminescent solar concentrator

Luminescent solar concentrators (LSCs) are presented that use a rear scattering layer made of a phosphorescent material for improving the use of the incident solar light spectrum. Besides simply scattering incident light that passes through the waveguide proper, the phosphor can absorb blue light and emit this light at a wavelength more amenable to absorption by the fluorescent dye. Integrated emission energies from the LSCs may be increased using the phosphor scatterer 4%–40% depending on the concentration of dye in the waveguide when compared to standard white scatterers

Switching between 3D surface topographies in liquid crystal elastomer coatings using two-step imprint lithography

While dynamic surface topographies are fabricated using liquid crystal (LC) polymers, switching between two distinct 3D topographies remains challenging. In this work, two switchable 3D surface topographies are created in LC elastomer (LCE) coatings using a two-step imprint lithography process. A first imprinting creates a surface microstructure on the LCE coating which is polymerized by a base catalyzed partial thiol-acrylate crosslinking step. The structured coating is then imprinted with a second mold to program the second topography, which is subsequently fully polymerized by light. The resulting LCE coatings display reversible surface switching between the two programmed 3D states. By varying the molds used during the two imprinting steps, diverse dynamic topographies can be achieved. For example, by using grating and rough molds sequentially, switchable surface topographies between a random scatterer and an ordered diffractor are achieved. Additionally, by using negative and positive triangular prism molds consecutively, dynamic surface topographies switching between two 3D structural states are achieved, driven by differential order/disorder transitions in the different areas of the film. It is anticipated that this platform of dynamic 3D topological switching can be used for many applications, including antifouling and biomedical surfaces, switchable friction elements, tunable optics, and beyond

Color-tunable triple state 'smart' window

Materials that rapidly change their optical properties in response to external stimuli are crucial for displays and “smart” window applications. Herein, a fluorescent red dye modified with liquid crystal (LC) side chains is described to be interactive with a LC host, resulting in a color‐tunable triple‐state smart window. The dye solubilizes in the LC matrix with increasing temperature, resulting in a red‐colored, absorbing state, recovering transparency again by reaggregation of the dye within minutes upon cooling. This dye is used to fabricate a device that can be electrically switched from a red‐colored, absorbing state to an intermediate scattering state and at greater electrical fields, a transparent state. Using a second dichroic fluorescent dye, heating the device transitions the window's color from yellow/green to red. The multiresponsive optical changes could find applications in many fields, including displays, smart windows, electricity generation, and signage