Infrared receptors of pyrophilous jewel beetles as model for new infrared sensors

Abstract

Purpose – Early detection of forest fires offers the chance to put the fire out before it gets out of control. The purpose of this paper is to look into nature and to learn how certain insects detect remote forest fires. A small group of highly specialized insects that have been called pyrophilous is attracted by forest fires and approaches fires sometimes from distances of many kilometers. As a unique feature some of these insects are equipped with infrared (IR) receptors, which in case of two species of jewel beetles (family Buprestidae) are used for fire detection. Design/methodology/approach – The paper has investigated the IR receptors of the pyrophilous beetles with various morphological techniques including scanning electron microscopy, transmission electron microscopy, neuroanatomy and the paper also investigated the thermo-/mechanical properties of the IR receptors by nanoindentation. Data were used for subsequent modeling of a biomimetic technical sensor. Finally, a macroscopic prototype was built and tested. Findings – This biological principle was transferred into a new kind of uncooled technical IR receptor. A simple model for this biological IR sensor is a modified Golay sensor in which the gas has been replaced by a liquid. Here, the absorbed IR radiation results in a pressure increase of the liquid and the deflection of a thin membrane. For the evaluation of this model, analytical formulas are presented, which permits the calculation of the pressure increase in the cavity, the deformation of the membrane and the time constant of an artificial leak to compensate ambient temperature changes. Some organic liquids with high thermal expansion coefficients may improve the deflection of the membrane compared to water. Originality/value – Results so far obtained suggest that it seems promising to take the photomechanic IR receptors of pyrophilous jewel beetles as models for the building of new uncooled IR sensors. The beetle receptors have been shaped by evolution since thousands of years and, therefore, can be considered as highly optimized sources of inspiration for new technical sensors suitable for remote fire detection.