Flexible and Emissivity-Adjustable Heat Flow Sensor Comprising a Carbon Nanotube/Polymer Composite

Heat flow sensors allow the straightforward measurement of the heat flow emitted from an object by attaching the sensor to the object. However, the inability of this method to control the surface emissivity of the sensor over a wide range lowers the measurement accuracy of a heat flow sensor. This study introduces a flexible heat flow sensor whose surface emissivity can be adjusted over a wide range. This sensor integrates a heat flow detector (HFD), which harnesses the Seebeck effect of a carbon nanotube/polymer composite to convert heat flow into voltage. This conversion exhibits a linear relationship with the heat flow, characterized by a proportional coefficient of 0.6556 mV·W^-1. The sensor features an emissivity-controlling layer (ECL), comprising a thin Al film deposited on a flexible polymer film substrate. The surface emissivity of the layer can be adjusted between 0.06 and 0.88 by modulating the thickness of the Al coating. The ECL can be easily attached to and detached from the HFD. The proposed sensor enables the measurement of heat flow from heat sources with various emissivities by simply affixing it to the source. This study shows that the deployment of such sensors is useful for the advanced thermal management of diverse facilities.