A thermal regulator using passive all-magnetic actuation

• Published in: Cell reports physical science 2023-09, Vol.4 (9), p.101556, Article 101556
• Main Authors: Castelli, Lorenzo, Garg, Ajay, Zhu, Qing, Sashital, Pooja, Shimokusu, Trevor J., Wehmeyer, Geoff
• Format: Article
• Language: English
• Subjects: contact conductance; thermal management; thermal regulation; thermal switch; thermomagnetic devices
• ISSN: 2666-3864; 2666-3864
• DOI: 10.1016/j.xcrp.2023.101556

Thermal regulators are two-terminal devices used for passive temperature control of electronics, batteries, or buildings. Existing thermal expansion regulators suffer from large thicknesses and substantial hysteresis. Here we report an all-magnetic thermal regulator in which the temperature of the control terminal (Tcontrol) leads to passive steady-state surface mating/demating that enables/blocks heat conduction. The mechanism relies on Tcontrol-dependent magnetic forces between gadolinium and neodymium iron boron magnets when Tcontrol is near gadolinium’s Curie temperature of 21oC. Our centimeter-scale prototype has a thermal switch ratio of 34−13+30 in vacuum and 2.1−0.2+0.2 in air, a vacuum OFF state thermal conductance of 3.5 mW/K, an average switching temperature of 20oC, a small thermal deadband of 5oC, and a relatively compact thickness 2,000 cycles and construct the regulator using commercially available materials, showing that this thermomagnetic device can be used for effective thermal regulation near room temperature. [Display omitted] •Passive two-terminal thermal switching using thermomagnetic actuation•Mechanism utilizes reversible magnetic phase transition of gadolinium foil•Switch ratio >30 in vacuum with switch temperatures ∼20°C and thickness 30x thermal switch ratios, offering potential for applications in aerospace or building thermal management.