Sungkyunkwan University team develops nanocomposite material with enhanced thermal conductivity

A Sungkyunkwan University research team has developed a novel nanocomposite material with enhanced electrical and thermal conductivity.

The university said Tuesday that the team, led by professors Baik Seung-hyun and Choi Joon-myung of the School of Mechanical Engineering, developed the material and successfully applied it to a heat-dissipation technology for foldable smartphones.

The findings were published online on Aug. 24 in the international journal Advanced Functional Materials under the title “Ballistic-like Thermal Transport Between Fillers in Highly Conductive Stretchable Nanocomposites.”

Baik served as the corresponding author. Research professor C. Muhammed Ajmal and researcher Cheon Seong-su served as co-first authors.

“The significance of this study lies in discovering a unique physical phenomenon in which thermal conductivity increases as the material is stretched through precise control of energy barriers between particles at the nanoscale,” Baik said.

“The study also demonstrated that this phenomenon can be applied to thermal management in flexible electronic devices, such as foldable smartphones.”

The university noted that smartphones and other electronic devices generate significant amounts of heat during operation, and if the heat is not dissipated effectively, devices may malfunction or have a shortened lifespan.

Next-generation flexible electronics that can be folded or stretched face an even greater challenge, as heat cannot easily escape when the devices are bent.

Normally, when a material is stretched like a rubber band, the particles inside move farther apart, reducing both thermal and electrical conductivity.

The research team, however, designed a material that overturns this conventional understanding.

The research team uniformly dispersed silver nanoparticles measuring 3.4 nanometers — several tens of thousands of times thinner than a human hair — in highly stretchable silicone rubber, maintaining an exceptionally narrow interparticle spacing of 4.1 nanometers.

By reducing the spacing between the nanoparticles to less than 10 nanometers, the team induced quantum tunneling, a phenomenon in which electrons can pass through an energy barrier.

Even when the material was stretched, it exhibited a phenomenon similar to ballistic transport, in which heat is transmitted without being scattered by obstacles, resulting in increased thermal conductivity.

The research team also found that the material could be further developed into a thermal switching material capable of controlling heat transfer under different conditions by precisely tuning the spacing between particles and the chemical properties of the rubber.

Through computer simulations, Choi demonstrated the microscopic mechanism underlying this phenomenon: As the material is stretched, the polymer chains within the material become aligned in a specific direction, enabling heat to be transferred more efficiently.

The research was funded by the Ministry of Education and the Ministry of Science and ICT. It was supported by the National Research Foundation of Korea, the Korea Institute of Science and Technology and the Commercialization Promotion Agency for R&D Outcomes.