Gold nanoparticles may help producing greener and faster LCD

LQ13486 - Can liquid crystal displays (LCD) be greener and faster? Physicists are now developing a new approach to do both. In a LCD, LC molecules are well aligned, with the first layer of LC molecules anchored on a substrate. Strong anchoring is important for high contrast display, but higher voltage is necessary to get the display to work, and the display responds slowly. People used to believe that anchoring strength is fixed once a device is packaged. Physicists have now found that, by placing gold nanoparticles on substrate and using an effect called localized surface plasmon resonance, it is possible to manipulate the anchoring by orders of magnitude with a weak light beam, because the light excites gold nanoparticles and boosts the light intensity in its neighborhood. The strong local field effectively lowers the anchoring strength at will. The dynamic reduction of anchoring strength also helps in speeding-up the response of LC display.

Water jets always break with the same conical shape

LQ13656E - Water trickling from a faucet, drops splashing from a puddle, the fringe of a breaking wave or the jet squirted by the archer fish: all involve a stream of water which breaks into drops. It turns out that underlying this process is a fascinating curiosity of nature. The precise conical shape of the liquid thread just before it breaks, whatever its origin and history, is always exactly the same, with an angle of 36 degrees. This phenomenon is known as self-similarity, and the angle was predicted theoretically in 1998. Now for the first time researchers have measured that angle in accurate experiments, for a wide range of starting conditions, and have found that the theory is indeed correct. They used a high-speed camera to study what happens in the last few millionths of a second before the jet breaks, and studied the behavior for both water and alcohol (ethanol). They also verified another prediction of the theory, about the speed with which the threads thins down. Theories for the behavior of liquid jets and drops are vital for improved technologies from ink-jet printing to crop spraying, and this new experimental work proves how accurate the current theories are.