When Ki Yeong Kim fine-tuned the first hollow silicon nanotubes in a lab at POSTECH in Pohang, South Korea, the tiny structures were no wider than a few thousandths of a human hair—but their potential was enormous. Inside those minuscule tubes, heat moves 70% more slowly than in solid silicon nanowires, a breakthrough that could transform how we reclaim wasted energy from data centers, electric vehicles, and industrial plants. Led by Professor Chang-Ki Baek of POSTECH’s Department of Electrical Engineering, Kim and his team have unlocked a path to high-efficiency thermoelectric devices using one of Earth’s most abundant materials: silicon.
Thermoelectric technology, which converts temperature differences directly into electricity, has long been limited by material constraints. Most high-performance thermoelectrics rely on rare and expensive elements like bismuth and tellurium, whose supply chains are fragile and prices volatile. Silicon, by contrast, is everywhere—and already the backbone of global semiconductor manufacturing. Yet its thermoelectric efficiency has historically been too low for practical use. The challenge has always been this: reducing heat flow without also crippling electrical conductivity. Like trying to quiet a room without suffocating it, both goals are essential but hard to achieve together.
The POSTECH team’s innovation lies in the hollow design of their silicon nanotubes. Think of them not as solid rods, but as microscopic pipes. In direct comparison with solid nanowires, these nanotubes reduced thermal conductivity by 70%. Even more remarkable, when the researchers equalized the surface area between the two structures, the nanotubes still conducted 33% less heat—proof that the hollow geometry itself disrupts heat flow in a fundamental way. The reason? Phonon localization. Phonons are the vibrations that carry heat through solids, and in these nanotubes, they become trapped, like ocean waves pinned behind a breakwater. This phenomenon was once thought to occur only at extremely low temperatures or in exotic materials, but the team demonstrated it at near-room temperature in a simple, scalable structure.
Published in Nano Energy, their work doesn’t just advance theory—it aligns perfectly with real-world manufacturing. Because the nanotubes can be fabricated using existing semiconductor processes, the leap from lab to factory could be swift. No rare metals. No overhaul of production lines. Just smarter nanoengineering.
“This technology is highly compatible with current chipmaking techniques,” said Professor Baek, “meaning we can improve energy efficiency without reinventing the wheel.” If scaled, these nanotubes could power everything from self-cooling batteries to silent, solid-state generators on industrial exhaust pipes. In a world where data centers alone consume more electricity than some countries, every watt recovered from waste heat is a step toward a leaner, cleaner energy future. And it might all start with a tiny tube, born in a lab in Pohang.