Self Regulating Hot Drink Cup

When I take a mug of coffee into the workshop, it's too hot to drink, so I put it down. When I remember it an hour later, it's cold. So I got myself an insulated stainless steel mug. My coffee remains scalding hot all day long.

What is needed (apart from the memory of a younger man) is a cup which will permit rapid cooling to a target temperature, then limit further cooling to maintain that temperature.

I propose a modification of the twin walled stainless steel mug:

Lining the outside wall are alternating vertical strips of copper and fibrous insulator. On the outside face of the inner wall are similar strips, so that small rotations of the inner relative to the outer can produce alignment or misalignment of similar strips.

When like strips are aligned, the contents will cool quickly.

A bimetal coil in the base rotates the inner when the target temperature is achieved, aligning each copper strip with an insulated strip, thus maintaining the contents at a more stable temperature.

The target temperature can be adjusted using a dial in the base of the mug, which adjusts preload on the bimetal coil.