Thermoelectric microprobes

Originally one of the most widely used temperature measurement instruments, the miniaturized version of the thermocouple, known as the "microthermocouple", appeared in the second half of the 20th century to meet the needs of industry on the one hand, and research on the other.

The miniaturization of thermocouples offers three advantages:

• reduction in sensor response time ;

• reducing its intrusiveness;

• and improved spatial resolution.

It's easy to see that these developments represent a potentially significant improvement in terms of measurement uncertainty.

Microthermocouples are beginning to play a major role in research sectors and are gradually emerging in industry. They can be used to improve production techniques or integrated into manufactured products. In research, they are now found in the family of local probes for near-field microscopy. Used to measure temperatures (passive mode) or thermal characteristics (active mode), they are generally obtained by modifying the probes used for atomic force microscopy (AFM). The acronym SThM stands for "Scanning Thermal Microscopy".

In this article, we present the state of the art in microthermocouples since their first appearance, starting with a reminder of the different types, the technological means used to manufacture them, and their main characteristics and application principles. The heat transfer phenomena involved will be described in detail, distinguishing between the two main modes of implementation: contact and non-contact. The notion of spatial resolution will be addressed, followed by static and dynamic calibration techniques. The specific fields of application of microthermocouples are mentioned throughout this article, but will be recalled in the conclusion, in order to give an indication of the future developments that can be expected.