Analysis of heating and cooling rates of polar bear hair by means of phosphor thermometry: A feasibility study

To survive within the extreme habitats of the Arctic, Polar bears (Ursus maritimus) have evolved numerous thermoregulatory adaptations. One such adaptation is the structure of their hair which is hollow in nature. Using the natural variation between polar and brown bears, we investigate the thermoregulatory properties of bear hair, specifically heating/ cooling rates using phosphor thermometry techniques. Polar bear hair strands were uniformly coated with La₂O₂S:Eu phosphor particles. A 405 nm diode laser firing at 20 Hz and of 30 µs duration excited the luminescence. A photomultiplier (PMT) with an intervening bandpass filter of 515 nm of 10 nm full-width half-maximum was used for signal detection, while attached to a fiber bundle situated 1.5 cm above the emitting region. Decay characteristics at and above room temperature were collected with decay times correctly reflecting the set temperature. This study paves the way for customized and accurate thermometry on a scale appropriate for microscopic evaluation of thin specimens.