Virtual Surfaces, Director Domains and the Freedericksz Transition in Polymer Stabilized Nematic Liquid Crystals

The critical field of the Freedericksz transition and switching dynamics are investigated for polymer stabilized nematic liquid crystals as a function of polymer concentration. A simple phenomenological model is proposed to describe the observed critical field and dynamic response time behaviors as a function of concentration. In this model the polymer fibrils form director domains, which are bounded by virtual surfaces with a finite anchoring energy. The Freedericksz transition occurs independently within each of these domains

The Composite Supercapacitor

Inspired by the design of composite materials, we propose a new composite supercapacitor that comprises an integrated cell with high-power- and high-energy-related electrode materials. The composite electrochemical double-layer capacitor (EDLC) is the equivalent circuit of a high-power EDLC of power P1 and energy E1 and a high-energy EDLC of power P2 and energy E2 connected in parallel. A methodology is proposed and validated in this study for the design of an application-specific composite supercapacitor of power P and energy E with P1/E1>P/E>P2/E2. The methodology was tested successfully in medium- and large-sized application-specific composite supercapacitors, which were fabricated in the form of pouch cells using an organic electrolyte. The application-specific composite supercapacitors offered weight reductions of 40–60 % compared with supercapacitors based on the high-power- or on high-energy-related electrode materials only

Active liquid crystal tuning of metallic nanoantenna enhanced light emission from colloidal quantum dots

A system comprising an aluminum nanoantenna array on top of a luminescent colloidal quantum dot waveguide and covered by a thermotropic liquid crystal (LC) is introduced. By heating the LC above its critical temperature, we demonstrate that the concomitant refractive index change modifies the hybrid plasmonic-photonic resonances in the system. This enables active control of the spectrum and directionality of the narrow-band (similar to 6 nm) enhancement of quantum dot photoluminescence by the metallic nanoantennas

All-optical control of a single plasmonic nanoantenna–ITO hybrid

We demonstrate experimentally picosecond all-optical control of a single plasmonic nanoantenna embedded in indium tin oxide (ITO). We identify a picosecond response of the antenna–ITO hybrid system, which is distinctly different from transient bleaching observed for gold antennas on a nonconducting SiO2 substrate. Our experimental results can be explained by the large free-carrier nonlinearity of ITO, which is enhanced by plasmon-induced hot-electron injection from the gold nanoantenna into the conductive oxide. The combination of tunable antenna–ITO hybrids with nanoscale plasmonic energy transfer mechanisms, as demonstrated here, opens a path for new ultrafast devices to produce nanoplasmonic switching and control.<br/

Go West: Stories

GO WEST is a collection of short stories that are not only set in the American West—several of them are set in the town of Grand Junction in western Colorado—but also that explore the idea of “west” as a symbol: west as moving on, west as healing, west as the unknown. These stories are meant to take a more positive look at the American West and the people who populate it than many stories of the West that have come before. In “Canned Peaches, or The Real World Goes Like,” a woman learns more about her grandfather’s suicide in order to begin her healing journey. A young woman finds a friend in difficult times in “This Story Ends in the Emergency Room.” And siblings are reunited in order to lay their father to rest in “Sunset Point.” None of these stories could be set anywhere else, however, since their settings are just as particularized as the people within. These are stories of the American West

Branching of colloidal chains in capillary-confined nematics.

We report on the observation of colloidal chain assembly and branching inside capillaries filled with a nematic liquid crystal. Because of the homeotropic anchoring of liquid crystalline molecules on the capillary and colloidal droplet surfaces, the assembly of droplets along the capillary axis is expected, producing a transformation of the nematic director field from an escape-radial to quasiradial configuration. However, the subsequent over time branching of the straight colloidal chains is counterintuitive. By numerical simulations, we demonstrate that chain branching can occur by overcoming an energy barrier and can at least dwell as a metastable configuration. Moreover, manipulation of colloidal chains by electric fields and their gradients demonstrates various regimes of chain behavior in electric fields

Virtual Surfaces, Director Domains and the Freedericksz Transition in Polymer Stabilized Nematic Liquid Crystals

The critical field of the Freedericksz transition and switching dynamics are investigated for polymer stabilized nematic liquid crystals as a function of polymer concentration. A simple phenomenological model is proposed to describe the observed critical field and dynamic response time behaviors as a function of concentration. In this model the polymer fibrils form director domains, which are bounded by virtual surfaces with a finite anchoring energy. The Freedericksz transition occurs independently within each of these domains