Infrared vision

Pit viper snakes like pythons and boas have specialized infrared-detecting pit organs with TRPA1 (transient receptor potential ankyrin 1) gene variants. These thermoreceptive TRPA1 channels are highly thermal sensitive that can detect temperature differences as small as 0.003 celsius. these receptors probably need to sit far away from vasculature so that they respond to radiant heat instead of internal body temperature variations.

The thermosensitive pit organ in snake has an external face membrane that looks out toward the air, and an internal face membrane that looks toward the underlying air-filled chamber. Warm arterial blood is prohibited from reaching the membrane. The temperature difference across the two faces is what the snake's thermosensitive receptors are measuring.

Fire-seeking jewel beetle (Melanophila acuminata) carries arrays of photo-mechanosensitive "infrared sensilla". Infrared warms a nanostructure, causing tiny mechanical changes that gate a mechanoreceptor. The principle is based on thermal expansion of many small dome-enclosed fluid-filled cavity converting infrared flux into a mechanosensory signal transduced via stretch-activated ion channels on a protein-chitin receptor membrane. Beetles can detect forest fires from many kilometers away. Various other insects have similar thermoception capabilities.

The infrared sensilla of the fire-seeking jewel beetle Melanophila acuminata are dome-shaped cuticular depressions, 12–15 µm in diameter, each housing a single, 200 µm-long, fluid-filled sensory organ composed of ≈70 mechanosensory neurons whose dendrites terminate on a thin (≈200 nm) protein–chitin receptor membrane that is mechanically deformed by the rapid (≈5 ms) thermal expansion of a fluid-filled cavity beneath the dome, converting minute (≈25 mK) infrared flux into a mechanosensory signal transduced via stretch-activated ion channels.

A microbolometer is a tiny, uncooled thermal sensor that detects infrared radiation by measuring the temperature-induced resistance change in a suspended microstructure. Can we make one out of proteins attached to an ion channel? infrared optogenetics? possibly a protein for this purpose could be evolved via in vitro directed evolution. could an aptamer do it? use knowledge of protein engineering, optogenetics, cytochrome C, chlorophyll, photosystems, etc.

maybe thermoresponsive elastin-like polypeptide (ELP) can be attached to a mechanosensitive channel (Piezo1). these ELPs have been used as genetically encoded thermosensors (ELP-TEMP) and as thermogenetic actuators in cells.

cytochrome c protein as a potential sensing material for long-wavelength bolometers -- "We simulated and experimentally proved high infrared absorption of cytochrome c in the wavelength between 8 μm and 14 μm."

maybe use triplet-triplet annihilation in a protein assembly like in "Photon upconversion supramolecular assemblies", however this seems to be mostly near-infrared-excitable not infrared-excitable.