Infrared camera on a butterfly's wing

Thermal cameras were constructed long ago, but working principles and complex technologies still limit their resolution, total number of pixels, and sensitivity. We address the problem of finding a new sensing mechanism surpassing existing limits of thermal radiation detection. Here we reveal the new mechanism on the butterfly wing, whose wing-scales act as pixels of an imaging array on a thermal detector. We observed that the tiniest features of a Morpho butterfly wing-scale match the mean free path of air molecules at atmospheric pressure - a condition when the radiation-induced heating produces an additional, thermophoretic force that deforms the wing-scales. The resulting deformation field was imaged holographically with mK temperature sensitivity and 200 Hz response speed. By imitating butterfly wing-scales, the effect can be further amplified through a suitable choice of material, working pressure, sensor design, and detection method. The technique is universally applicable to any nano-patterned, micro-scale system in other spectral ranges, such as UV and terahertz.