Search NASA⌕ Search

SEARCH · Search NASA

Results for “Active nematics”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Electronically tuned optical filters

A detailed account is given of efforts to develop a three layer, polychromic filter that can be tuned electronically. The operation of the filter is based on the cooperative alignment of pleochroic dye molecules by nematic liquid crystals activated by electric fields. This orientation produces changes in the optical density of the material and thus changes in the color of light transmitted through the medium. In addition, attempts to improve materials and devices which employ field induced changes of a cholesteric to a nematic liquid crystal are presented.

Castellano, J. A.↗
NASA NTRS1986

Liquid crystals for high-altitude in-flight boundary layer flow visualization

A novel method for visualization of laminar to turbulent boundary layer transition in flight is presented, in which liquid crystal coatings are used to indicate the transition by a change of color (in response to the changes in the wall shear and the temperature). The liquid crystals applied to the wing surfaces were either cholesteric crystals formulated to be active between temperatures of 30 and 100 F or a sample of chiral nematic liquid crystals formulated to be active between -18 and -22 F. Liquid crystal coatings were shown to provide visualization data at flight altitudes and temperatures at which data could not be obtained previously. Flight evaluations were successfully conducted on a T-34C and a Learjet research aircraft at Mach numbers of up to 0.8 and altitudes of up to 50,000 ft. The time response during oscillating sideslip tests was very rapid. In wind tunnel tests, a hysteresislike behavior was observed in the liquid crystal coatings, possibly because of the lower dynamic pressures in wind tunnels as compared to flight.

Gall, P. D.↗
NASA NTRS1975

A new real-time non-coherent to coherent light image converter - The hybrid field effect liquid crystal light valve

A new, high-performance device has been developed for application to real-time coherent optical data processing. The new device embodies a CdS photoconductor, a CdTe light-absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The noncoherent image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the ac voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state and the optical birefringence effect to create the bright on-state. The liquid crystal modulates the polarization of the coherent read-out light so an analyzer must be used to create an intensity modulated output beam.

Grinberg, J.↗
NASA NTRS1977

Reflective liquid crystal light valve with hybrid field effect mode

There is disclosed a high performance reflective mode liquid crystal light valve suitable for general image processing and projection and particularly suited for application to real-time coherent optical data processing. A preferred example of the device uses a CdS photoconductor, a CdTe light absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The non-coherent light image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the AC voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state (voltage off the liquid crystal) and the optical birefringence effect to create the bright on-state. The liquid crystal thus modulates the polarization of the coherent read-out or projection light responsively to the non-coherent image. An analyzer is used to create an intensity modulated output beam.

Boswell, Donald D.↗