Contact-Based Passive Thermal Switch with a High Rectification Ratio

Thermal control devices like diodes, regulators, and switches are essential to achieve directional heat flow for numerous applications, such as electronic systems, energy conversion or storage systems, and equipment for buildings. These devices exhibit a controllable thermal conductance that can be manipulated to allow preferential thermal transport. While several design concepts have existed for decades, they are rarely deployed due to some basic practical limitations related to scalability, cost, operating temperature, and/or requirements for external excitation. In this study, we achieved a fundamental breakthrough in developing a passive thermal switch, which has a simple and scalable design, is thermally driven (thus does not require an external stimulus), and exhibits a rectification ratio of 17.5, which is among the highest value reported for passive switches in the literature. Notably, the switch transitions from an effective thermal conductivity of ~1.6 W/m-K (insulator) in the OFF state to ~28 W/m-K (conductor) in the ON state near 50 degrees C. To demonstrate the cost-effective implementation of our technology at a large scale, we developed a self-regulating insulation panel that automatically varies its thermal resistance by using just a few thermal switches occupying less than 10% of the total surface area. Lastly, using a parametric analysis, we establish a promising pathway to further improve the performance and versatility of the proposed technology.