UCLA researchers have achieved a significant milestone in thermal energy management by developing an electrically-controlled transistor capable of precisely regulating heat flow. This innovative device showcases an impressive heat-flow on-off ratio of over 13:1, controllable with a modest ±2.5V base bias at room temperature.
High-Efficiency Voltage-Flow Characteristics
Characterized by an almost linear voltage-flow curve, the transistor demonstrates efficient performance. Remarkably, it has successfully operated at frequencies up to 1MHz, indicating its potential for high-speed thermal management applications.
Aspiring to Control Heat Flow Precision
Yongjie Hu, a professor of engineering at UCLA, emphasizes the long-standing goal of physicists and engineers to precisely control heat flow through materials. This novel design brings that dream closer to reality by manipulating heat movement with an electric field, akin to the way electrical transistors have functioned for decades.
Nano-Scale Construction of the Device
The transistor is a product of nanotechnology, starting with an atomically-flat gold coating on a substrate. A self-assembling monolayer of carboranethiol cage molecules is applied next. These multifaceted cage-like molecules stand upright on the gold surface, anchored by a sulfur atom.
Graphene Integration and Control Mechanism
A layer of single-sheet graphene is placed over this molecular forest, held approximately 1nm from the gold by the cage molecules. The control potential bias is applied between the gold and a top contact above the graphene, influencing the thermal conductivity.
Understanding the Operation
The operation involves a shift in the atoms shared by the sulfur and gold to form their bond, influenced by the applied electric control field. This shift alters the strength of the bond, thereby varying the local thermal conductivity. A similar mechanism occurs at the graphene interface, relying on Van der Waals attraction rather than covalent bonding.
Impact on Thermal Conductivity
The thermal conductivity of this transistor can vary significantly, ranging from below 10MW/m2/K to over 130MW/m2/K. This wide range of conductivity control presents new possibilities in thermal management across various applications.
UCLA’s development of an electrically-controlled transistor for thermal energy marks a substantial advance in thermal management technology. Its ability to control heat flow with precision and efficiency opens up new avenues for innovation in thermal regulation across diverse sectors.