Tunable Thermal Link
APPLICATIONS OF TECHNOLOGY:
- Electronic and thermal circuit design and operation - Solar energy collection - Heat pumps and internal combustion engines - Hybrid biological/inorganic systems - Phononic information processing - Energy-efficient buildings and appliances, such as refrigerators
- Provides adjustable thermal conduction, a thermal analog to rheostats - Can control heat flow in nanoscale or microscale devices and thermal logic devices - Thermal conductance can be cycled at rapid rates, e.g., in the GHz range - Extremely durable, wears well - Very little friction
Thermal links are incorporated into everything from frying pans to internal combustion engine spark plugs and heat sinks on integrated circuit boards. Typically, the link’s thermal resistance is fixed and cannot be tuned after manufacture. While the ability to tune electrical resistors is widespread, virtually no tunable thermal resistance link exists, which has held back the development of thermal systems.
Alex Zettl, Arun Majumdar and their teams at Lawrence Berkeley National Laboratory have developed telescoped multiwall nanotubes that can be variably controlled, providing the first step toward a fully functional thermal transistor, and removing the main obstacle for heat management and for the processing of phonons as information carriers.
Multiwall nanotubes have a very high intrinsic thermal conductance. If a nanotube is geometrically damaged, its thermal conductance is decreased. The thermal conductance of an individual multiwall carbon nanotube can be controllably and reversibly adjusted by sliding the outer shells in and out of the inner core. The conductance drops dramatically (by 85 percent of the original value) after the length of the tube is extended as the nanotube is telescoped out and the core tubes slide from the remaining “housing.” An exponential increase in the thermal resistance occurs with telescoping distance.
The invention would typically include numbers of multiwall nanotubes connected to a heat source and a heat drain and various means of tuning the overall thermal conductance. Although at present controlled by mechanical actuation, it could also be controlled by a thermal gate utilizing thermal expansion of materials.
Tunable nanoscale thermal links have immediate implications for nano- to macroscale thermal management, biosystems, and phononic information processing.
Alex Zettl, Arun Majumdar
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