[1] In April 2015 Italian researchers at CNR announced development of a working thermal diode,[2] publishing results in Nature Nanotechnology.
A sensor device embedded on microprocessors used to monitor the temperature of the processor's die is also known as a "thermal diode".
As the sensor is located directly on the processor die, it provides most local and relevant CPU and GPU temperature readings.
Thus the junction temperature can be determined by passing a set current through the diode and then measuring voltage developed across it.
As of 2009 a team at MIT is working for construction of thermal diodes that convert heat to electricity at lower temperatures than before.