Mission Possible/Bimetallic strip

A bimetallic strip is composed of two different kinds of metals that have been bonded to each other in a strip. Since the metals react to changes in temperature differently, the strip will curl in one direction or the other (or curl and uncurl, if it is formed into a coil). This can be used to make a transfer that reliably reacts to changes in temperature.

=Acquisition= Any digital device is likely to be using a thermistor or thermocouple to detect changes in temperature, not a bimetallic strip, so analog devices are your best bet for finding these.

Thermometers
The common 'rotary dial' analog thermometers use bimetallic strips that are formed into a coil. One end remains fixed while the other end controls the dial's movement. The common outdoor dial thermometers, oven dial thermometers, and hopefully any other rotary dial analog thermometer should have a coil of bimetallic strip in them. Shouldn't cost more than $5.

Thermostats
'Some' analog thermostats contain bimetallic strips. There is an equal or better chance that any given analog thermostat will use a mercury switch, which isn't of any use to you (mercury counts as a hazardous substance).

=Usage=
 * Heating - increasing the temperature of the strip is easy and fast.
 * Nichrome wire
 * Matches/Candles
 * Peltier device


 * Cooling - it is usually easier to cool the strip down to ambient temperature from a higher temperature
 * Fans (cooling to ambient)
 * Peltier device (active cooling)