Session: 11-58-01: Nanoscale Thermal Transport

Paper Number: 119733

119733 - A Three-Terminal Magnetic Thermal Transistor 

Three-terminal thermal analogies to electrical transistors have been proposed for use in thermal amplification, thermal switching, or thermal logic, but have not yet been demonstrated experimentally. Electrical field-effect transistors (FETs) are three terminal transconductance devices in which the current flow between source and drain is controlled by the gate-drain or gate-source voltage, while electrical bipolar junction transistors (BJTs) are three-terminal current amplification devices in which the collector current is controlled by the base-emitter current. By analogy with these electrical devices, a thermal transistor is a three-terminal thermal element in which the temperature or heat flow at one terminal controls the heat flow between the other two terminals in a manner that leads to heat flow switching and amplification. Previous researchers have computationally investigated three-terminal thermal transistors using mechanisms based on thermal radiation, nonlinear phonon conduction in nanoscale systems ,  nanoscale confined fluids, quantum electronic systems, and superconducting devices. Despite this prior theoretical interest in three-terminal thermal transistor systems, no thermal transistor devices have been experimentally demonstrated, presumably due to the challenges in fabrication and/or measurement of the previously proposed thermal transistor mechanisms.

Here, we design and fabricate a three-terminal magnetic thermal transistor in which the gate temperature controls the source-drain heat flow by toggling the source-drain thermal conductance from ON to OFF. The centimeter-scale thermal transistor uses gate-temperature dependent magnetic forces to actuate motion of a thermally conducting shuttle, providing thermal contact between source and drain in the ON state while breaking contact in the OFF state. We measure source-drain thermal switch ratios >100 in high vacuum with gate switching temperatures near room temperature. Thermal measurements show that small heat flows into the gate can be used to drive larger heat flows from source to drain with amplification ratios near 30, and that the switching is reversible over >150 thermally driven actuation cycles. We investigate the behavior of the thermal transistor in several thermal circuits and show that the device enables active or passive heat flow routing for applications in controlled power generation and thermal storage. For more speculative applications in thermal computing or thermal sensing, the transistors can be combined in series to create a thermal AND logic gate or combined in parallel to create a thermal OR logic gate. Overall, this magnetic thermal transistor demonstration provides an experimental platform to explore three-terminal thermal switching and amplification of heat flows, and motivates further research implementing thermal transistors for improved control of engineering systems.

Reference: 

Castelli, L., Zhu, Q., Shimokusu, T.J. et al. A three-terminal magnetic thermal transistor. Nat Commun 14, 393 (2023). https://doi.org/10.1038/s41467-023-36056-4

Presenting Author: Geoff Wehmeyer Rice University

Presenting Author Biography: Geoff Wehmeyer is an assistant professor in Mechanical Engineering at Rice University. He received his B.S. in Mechanical Engineering from the University of Texas at Austin in 2013 and his Ph.D. in Mechanical Engineering from the University of California, Berkeley in 2018 before joining the faculty at Rice. His research group uses experimental and theoretical methods to understand and control heat transfer.

Authors:

Lorenzo Castelli Rice University
Qing Zhu Rice University
Trevor Shimokusu Rice University
Geoff Wehmeyer Rice University