The key for this magic trick is physics and PCM—phase change material—an extraordinary substance used in construction and winter clothing. PCM is capable of storing and releasing heat or cold.
In its original state it is a solid but then, when it receives heat, it absorbs it like a sponge liquifying into a gooey wax. As the PCM solidifies it releases the energy at a steady pace, keeping any liquid or room at the perfect temperature. In houses, they achieve this by filling hollow walls with PCM, which absorbs heat from the sun, and then releases it as the atmosphere cools down, keeping the room at a perfect temperature.
The perfect mug follows the same principle: It is made of hollow ceramics. Inside there's an aluminium structure—as you can see in the image above—which gets filled with PCM. When you pour in your hot coffee, the heat gets absorbed reaching your personal optimum level based on the amount of PCM in the cup's interior. According to Klaus Sedlbauer, head of the Fraunhofer Institute for Building Physics, you can customise this on manufacturing. Their perfect cup, however, keeps it at 58 degrees Celsius:
Warm drinks — like coffee or tea — are best enjoyed at 58 degrees Celsius. In order to reach and maintain this temperature, we fill the mug with a type of PCM that becomes a liquid at exactly 58 degrees Celsius. Under ideal circumstances, the optimal temperature can be maintained for 20-30 minutes.
I don't know about you, for for me they are not putting this into the market soon enough. [Spiegel]