PRADEEP RANA | NEW DELHI Indian scientists have developed a new type of screen from the discarded groundnut shells that can turn transparent or foggy depending on the heat and light conditions. The cellulose-based "smart screen" developed by scientists of Centre for Nano and Soft Matter Sciences, Bangalore, is set to find a lot of applications ranging from protecting one's privacy to energy conservation by reducing the air-conditioning load. A group of researchers led by Prof. S. Krishna Prasad and Dr Shankar Rao said the screen employed the same principle that causes fog in the winter mornings. This happens when the water droplets of varying size are floating in the air. The incoming light hits these droplets of different refractive indices and gets scattered, giving a foggy effect. The screen material could be developed from any cellulose or agricultural waste. But due to certain properties, the screen developed from groundnut waste has been found to be most efficient. Smart screen works on system of confining liquid crystal molecules in a polymer matrix. The matrix was developed by Prof. Yuvraj Singh Negi's team at IIT Roorkee, using cellulose nanocrystals(CNC) from discarded groundnut shells. Difference in refractive indices of the polymer and the liquid crystal results in scattering of light. Refractive index of the liquid crystal molecules changes on passing the electric current. The liquid crystal molecules change direction and result in the matching of refractive indices which make screen transparent almost instantly. When the current is turned off, the screen becomes foggy again. This switching between transparent and foggy state comes handy in using it for privacy purpose and regulating the heat in an AC enclosure. The original intention was privacy, but the screen can be used for a whole range of applications, especially in energy conservation by controlling the light that is permitted to pass through window.