Ken Marshall is developing new flakes called polymer cholesteric liquid crystals (pCLC) that reflect visible to near-infrared wavelengths. By altering the composition of the liquid crystal films, the research engineer and his team at the University of Rochester create a range of flakes, each of which reflects a different color. "Most devices that generate color do so either by absorbing or emitting certain wavelengths of light," says Marshall. "Cholesteric liquid crystals function by reflecting only a narrow wavelength bandwidth of light." His findings could form the basis of a new type of color display. "The crystal molecules are organized in the form of a helix," he explains. Each of the components is circularly polarized. One component twists in the same direction as the helix and is completely reflected. The other component twists in the opposite direction and is completely transmitted. This effect only occurs when the wavelength of the incident light equals the helix pitch of the cholesteric LC (the distance along the helix it takes to rotate 360 degrees) times the average refractive index of the CLC material. "So, if the helix of the CLC material is about equal to that of green light around 543 nm, then only circularly polarized green light of the same orientation as the CLC helix is reflected," says Marshall. The pCLC flakes, each about 40 microns across, are dispersed in a host fluid such as silicone oil. When an electric field is applied to the device, the flakes rotate and the bright reflection color is extinguished. When red, green, and blue flakes are combined together in a host fluidówith each color type treated differently so as to respond to a different voltage or frequency of the driving electric fieldócolors can be displayed individually or in combinations. The applications for this technology are much broader in scope than just information displays, according to Marshall. They include e-paper; color filters; optical retardation or modulation elements for polarized light in military security and camouflage; and document security and anti-counterfeiting. Contact Marshall at firstname.lastname@example.org.
More and more robots are becoming more autonomous all the time. Now Lockheed Martin has completed a demo mission with two completely autonomous robotic vehicles performing resupply, reconnaissance, surveillance, and target acquisition.
Producing high-quality end-production metal parts with additive manufacturing for applications like aerospace and medical requires very tightly controlled processes and materials. New standards and guidelines for machines and processes, materials, and printed parts are underway from bodies such as ASTM International.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.