An imager pixel comprising a micro-platform supported by phononic nanowires, the nanowires providing an extreme-level of thermal isolation from a surrounding substrate. The micro-platform in embodiments comprises thermal sensors sensitive to heat from absorbed incident longwave/shortwave photonic irradiation. In embodiments, the pixel photonic sensing structure comprises both a thermal sensor together with a separate photodiode/phototransistor/photogate for sensing RGB and NIR wavelengths. Some embodiments comprise a micro-platform with an integral Peltier thermoelectric element permitting in situ refrigeration to cryogenic temperatures.