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Indian Institute of Technology (IIT) Roorkee 
A dielectric elastomer based electrically tunable reflector with variable focal length 
M.M. Joglekar, Katik Kashyap, Nitesh Arora, Chinmay Jivani, Parmod Kumar and Atul Kumar Sharma 
Indian Institute of Technology (IIT) Roorkee 
Application type:
Applied - 2020-02-11 
Application Number:
Applied at:
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Indian Institute of Technology (IIT) Roorkee 
The basic aspect of present invention, an electroactive polymer-based tunable reflector is provided for optical applications. The variable 15 focal length reflector assembly admits both concave and convex configurations of the reflector by changing the bias pressure. Furthermore, in a given configuration (concave or convex), the curvature of the reflector can be varied by varying the applied electric potential. The dielectric elastomer is the electroactive polymer that is used in the design according to the invention. The EAPs are essentially the deformable capacitors, which do not allow the passage of electric current. Therefore, the power consumption in the proposed design is minimal. Both concave and convex reflector profiles can be obtained in the same setting, by changing the bias pressure. A focal length variation of 2000 microns has been demonstrated experimentally for the concave reflector, while that of 4500 microns has been achieved in case of a convex reflector. The variable focal length reflector assembly consists of Small rubber ring, Plastic flange, Carbon coated membrane, Valve, Large rubber ring, Nut and bolt, Reflective coating, Metallic flange, Metallic ring, Pressure chamber, Cover plate, Pin, Valve extender. Reflective and carbon coated membrane constitute movable parts, where carbon coated membrane functions as dielectric elastomer actuator and reflective coating provides reflecting properties to passive membrane. Reflective coating is initially fabricated through silver sputtering. Metallic ring and flange are used for clamping the membrane in between, providing flat surface after application of loads. Rubber rings are used to avoid leakage. Flanges, nut and bolt generate outward bending of cover plate, facilitating compression of rubber ring. Pin transfers the current to one of the electrodes. Pressure chamber combines all of the components, and facilitates transfer of electro-pneumatic actuation. 

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