We report the demonstration of an optically activated shutter based upon a short-pitch chiral nematic liquid crystal (LC) device sandwiched between crossed polarizers. This LC is comprised of photo-active chiral dopants. In the trans-state, the LC appears dark between crossed polarizers due to the very short pitch. As the pitch is extended through exposure to ultraviolet light, the device becomes transmissive reaching a maximum for a particular value of the pitch. As a result, it is possible to switch between the light and dark states by subjecting the device to visible light so as to cause a cis-trans photo-isomerisation.

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This chapter delivers an outline of the strategies and techniques that are used and developed for the fabrication of membrane techniques/methods for application in environmental engineering. Human activities are the cause of increased hazardous gases in atmosphere mainly in soil and water. Nanotechnology deals the ability to control matter at the nano-scale level. Materials prepared are in nano level and thus they will possess some special properties to deal with specific functions. One of the major aspects of nanotechnology is nanomembrane fabrication which is mainly employed for water purification plants. The chapter is specifically offers a full understanding of the technologies and laws used to synthesize membranes. The chapter also provides an introduction to techniques to characterize nanomembranes.