Uncooled bolometers consist of thermally isolated microbridges, with a temperature sensitive material deposited on top. The temperature sensitive material can be V2O5, a-Si or poly-SiGe. The microbridges are surface-micromachined directly on the CMOS circuits (see figure below).

Combining thermal detector elements with an integrated circuit raises the problem of interfacing the detector elements and the IC. One of the more serious problems arises because thermal detector elements must be heated, or allowed to cool, due to the radiation to be detected. Therefore, for optimum performance, the detectors must be thermally isolated from their surroundings. This precludes the simple depositing or mounting of the detectors directly on the IC - because Si is a good thermal conductor. Otherwise, the detectors would become so thermally loaded that it would adversely affect their performance as thermal detectors.

Therefore, the microbridges are surface-micromachined directly on the CMOS circuits. This permits the fabricating of contact supports that establish a compromise between a good electrical contact, which is needed to read out the detector element, and a poor thermal contact, which prevents thermal leakage of the absorbed radiation.