This materials-driven study considers the potential of micro-encapsulated leuco dyes. These reversible thermochromic smart materials change color, from opaque to transparent, when they reach a predetermined transition temperature.

Wang’s “Back In A Bit” chair cushion uses this thermochromic material to inform others that you’ve just left your seat, a few minutes ago. If you don’t return soon, then the message fades away.

The cushion can serve this function, because the thermochromic dyes that color the cushion become transparent as you sit on the cushion, warming it up with your body heat, to reveal the “Back In A Bit” message that’s printed beneath the opaque thermochromic coating.

The message will soon disappear, as the thermochromics cool to room temperature again, and become opaque. Therefore, this project had to address how long the message can stay on the cushion, since the thermochromic leuco dyes would only stay clear for about a minute after they are activated. Hence, the cushion consists of many layers, including a layer that retains heat for a few minutes.

The bottom layer is a silicone friction pad that makes sure that the cushion doesn’t slide around on a chair or stool. On top of that, there is a layer of foam that increases comfort while sitting. Then, there is a layer of encapsulated hydrogels, which can effectively retain heat for a known period of time. Then the leuco dyes and, finally, on top of the leuco dye layer, the cushion is coated with waterproof PU, to protect the cushion from staining.