Micro heat flux sensor using copper

A micro heat flux sensor which can measure the thermal energy transfer per unit area has been designed, fabricated, and calibrated in a convective environment. The sensor which is based on a circular foil gage is composed of thermal paths and a thermopile. The thermal path is made in a LIGA-like process of SU-8 high aspect ratio microstructures and electroplated copper layers. The thermopile, a series of thermocouples, is used to amplify the output signal as a thermometer. When the sensor is placed on a high-temperature wall, heat flux from the wall flows through thermal paths and drains out to the environment, producing a temperature difference along its paths. Heat flux is obtained by calibrating this temperature difference in the thermopile of Ni–Cr or Al–Chromel pairs. The sensitivity of the heat flux sensor of Ni–Cr and Al–Chromel pairs is in the range of 0.1–2.0 and 0.4–2.0 µV mW−1 cm−2, respectively, in the heat flux range of 0–180 mW cm−2. (Some figures in this article are in colour only in the electronic version; see www.iop.org) 1