Privacy Window

Privacy is such a valuable thing—we all need privacy now and then. Whenever I work, I like to go to a quiet place where no one is around, but sometimes solitude can be elusive.


There is a large glass door in the room where I work through which passersby may easily see what I am doing. To give myself more private space, I decided to create something that can block people from seeing through the glass.


There are many traditional ways to block a window, but the electro-chromic film maximizes my view out the door without sacrificing my privacy.

The principle behind this material is simply liquid crystal molecules. When the plastic film is "off," meaning that there's no electric current, the liquid crystal molecules inside are randomly oriented. This scatters incidental light, making the film opaque. However, when the film is "on," the molecules line up and let the incidental light pass through, making the film clear.


I connected the film to an infrared sensor, which can detect invisible thermal radiation emitted from people. The sensor switches the film, so when it detects someone nearby, it opens the circuit, making the film opaque, and when no one is around, it closes the circuit, enabling the liquid crystal molecules to line up and let light come through.

I attached the film to my glass door, and here's how it looks: