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when S Krishna Prasad and co-workers at the Centre for Light Crystal Research in Bangalore shone a light on a class of liquid crystals, it induced the crystal molecules to change shape on a quick time-scale. This finding suggests that the system is a potential candidate for storage of images or other optical data.
Phase transitions of shape, induced by temperature, are common in nature; for example ice is transformed to water when it is heated. In recent years, however, it has been found that light can mimic the role played by temperature in bringing about a phase transition. This occurs in certain materials with properties that are in between that of a solid and liquid, namely liquid crystals.
Prasad and his colleagues discovered that the key to such phase transitions in these materials (like azobenzene) is the change in shape driven by light. In its ground state, the azobenzene molecule, for instance, exists in an arrangement known as trans conformation. But when it is irradiated with light of suitable wavelength (365 nanometre), it undergoes a conformational change to the cis state.
Along with this conformational transformation, the molecule changes shape