Indian scientists have developed an eco-friendly smart screen from groundnut shells that could help not only in preserving privacy but also in energy conservation by controlling light and heat passing through it and reducing air conditioning load.
Led by Prof S Krishna Prasad, along with Dr Shankar Rao of the Centre for Nano and Soft Matter Sciences (CeNS), Bangalore, an autonomous institute of the Department of Science & Technology, Government of the researchers developed smart screen application, liquid crystal molecules which were confined in a polymer matrix.
“The matrix was built using cellulose nanocrystals (CNC) which were prepared from discarded groundnut shells by Prof Yuvraj Singh Negi’s team at IIT Roorkee. The refractive index of the liquid crystal molecules along a particular direction were altered by the application of an electric field.
“In the absence of the electric field, there was a mismatch between refractive indices between those of the polymer and the liquid crystal, leading to the scattering of light. Upon application of a few volts of an electric field, the liquid crystal molecules underwent a direction change resulting in the matching of refractive indices, and the device became transparent almost instantaneously.
“When the field was turned off, the system quickly recovered the scattering state. This reversible change between the two states available at the flip of a switch occurred over thousands of cycles, with essentially no change in contrast or switching speed,” said the scientists about the device which has been described in a recent issue of Applied Physics Letters.
Pragnya and Dr Srividhya, students who worked on the device, emphasised that the protocol for the CNC preparation plays a key role in controlling the device contrast with the IIT Roorkee material outperforming the CNC available from commercial sources.
The scientists said that while, in principal, the device could be developed from any cellulose or agricultural waste, due to certain properties of groundnut waste, the smart screen developed from groundnut waste has been found to be most efficient.