Peculiarly, some ultra-small heat sources lose heat when you pack them closer to each other. University of Colorado (CU) Boulder physicists have recently discovered the cause behind this confusing nanoscale phenomenon. Their research, published in the journal Proceedings of the National Academy of Sciences (PNAS), may be applied in the technology industry in the future to create the next generation of tiny, fast electronic devices.
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The Challenge of Overheating for Electronic Devices
Heat presents challenges for electronic device manufacturers and designers because it leads to slower computer processing and faster wear and tear. There are many factors that influence electronic devices' likelihood to overheat and are often outside of the manufacturers' control.
Materials and structure of housing components, wiring and electronic component layout, inadequate power supply, as well as environmental factors such as a lack of ventilation or a high ambient temperature all contribute to device overheating.
Controlling heat transmission in devices is complicated. Minute manufacturing defects or design oversights in items like computer processing chips can unexpectedly raise the device's temperature, negatively impacting the device's performance and longevity.
Heat transmission is also not fully understood at a nanoscale level. The mechanism for heat to transfer and dissipate over relatively large objects is known and can be used to design larger electronics to accommodate optimized heat flow. Desktop computers made for gaming and high-speed Formula 1 cars, for example, optimize performance by manipulating airflow to prevent overheating.
However, at nanoscale sizes, phonons (vibrations of atoms that carry heat in solid form) become more relevant, yet their behavior is not fully understood. Considering this and the fact that modern transistors are becoming as small as 5 nm across, improving knowledge of heat transfer at the nanoscale is essential to optimize devices.
Understanding how phonons work on the nanoscale means understanding how heat moves atomic-by-atom across minuscule spaces and through molecules of matter.
Managing The Flow of Heat
The CU Boulder physicists behind this research set out to understand how phonons work so that they can effectively manage the flow of heat through materials and space.
An unexplainable observation kicked off the research in 2015, when CU Boulder scientists Margaret Murnane and Henry Kapteyn conducted experiments with thin-film metal bars on a silicon substrate.
The metal bars, by themselves, did not dissipate heat quickly. However, when they were packed closely together, they were able to cool down very quickly after the researchers heated them with lasers.
The CU Boulder physics department then set out to understand the fundamental physics involved in this phenomenon to create electronic and other devices in the future that can manage heat flow effectively.
The latest study shows how this phenomenon works. Computer simulations were used to track heat's passage through the nano-sized metal bars. When placed closely together, bars vibrated with energy from the heat that interfered with vibrations from the other bars, scattering it away from the material and cooling all of the bars down quickly.
As heat scattered away from the vibrating nano-sized metal bars, its energy was forced into a uniform direction away from the bars. Its intensity was also increased, and it moved away from the bars more rapidly. The physicists have dubbed this phenomenon "directional thermal channelling."
What Does This Mean for the Electronics Industry?
The results of this research highlight challenges as well as opportunities for electronics manufacturers. Heat does not behave as expected at the tiniest scales of size, with manufacturers likely to enter unknown territory as they produce smaller and smaller devices. Still, it could also present an opportunity to overcome current overheating limitations in tiny devices by manipulating the directional thermal channelling effect.
Manufacturers and developers of nanoscale devices like quantum chips and sensors, thermoelectrics, and nanoelectronics will be interested in this research. Considering how it could be applied to research and development operations will likely dictate the potential relevance of this research in a range of industrial sectors.
Continue reading: Could Copper Nanowires Improve Semiconductor Thermal Conductivity?
References and Further Reading
Honarvar, H. et al. (2021) Directional thermal channeling: A phenomenon triggered by tight packing of heat sources. PNAS. Available at: https://doi.org/10.1073/pnas.2109056118.
Strain, D. (2021) Cool it: Nanoscale discovery could help prevent overheating in electronics. CU Boulder. Available at: https://www.colorado.edu/today/2021/09/20/cool-it-nano-scale-discovery-could-help-prevent-overheating-electronics.