Electrostatic flexible film based smart window: Optical design, performance and residual charge investigation

The authors report the design and performance of a dynamic polymeric window shade (smart window) based on electrostatic flexible film with rolling electrode. The device consists of a transparent glass substrate, a low-E conductive fixed electrode, an insulating dielectric polyimide layer and a coiled spiral conductive layer used as a rolling electrode. The application of a voltage in this device creates an electrostatic force that unrolls the curled film, reducing the intensity of radiation passing through the window. The influence of the dielectric layer thickness on operating voltage at different temperatures has been investigated and agrees with the simulated results. It is shown that the device carries residual charges after 2400 cycles of repeatable extension and retraction testing. Measurement results show that the residual surface potential increased with the thickness of dielectric layers as well as the temperature in dynamic polymeric window shade. The possible residual charge storage generation mechanism, namely, ionization based on modified Panchen law, is introduced in the paper, which shows good agreement with experimental results at higher dielectric layer thickness.