This is Heat Flux HF-10S Sensor (MTI.AWS.EK.HF.10S). A heat flux sensor is a thermopile, an electronic device that translates thermal energy into an electrical voltage proportional to the temperature gradient across its thermocouples' hot and cold junctions. 
EKO Instruments offers a selection of thin substrate heat-flux sensors in a range of different sizes and thicknesses, an ideal option for research and engineering applications as well as manufacturing control and monitoring processes.
At only 0.5mm thick, the HF-10S is super-thin and weather-proofed, with incredibly low thermal resistance, making it an ideal option for research applications and manufacturing control processes.