Probing Tiny "Heat" with Great Passion

Participant Profile

Yoshihiro Taguchi

Yoshihiro Taguchi

Yoshihiro Taguchi (Assistant Professor, Department of System Design Engineering)

Many people have probably experienced low-temperature burns from using a hot laptop on their laps. When a computer gets too hot, a so-called thermal runaway can occur, rendering it unusable. The CPUs (Central Processing Units) in modern computers, in particular, have hundreds of millions to over a billion tiny transistors densely integrated. It is said that their heat generation density (heat flow per unit time and unit area, or heat flux) is comparable to the surface of a rocket during a space shuttle launch or even the surface of the sun. (Some people have even fried an egg using the heat from a computer's CPU). However, no one has yet actually seen what the temperature distribution of a CPU looks like, because there is no method to observe such a minute temperature distribution.

As materials are made smaller or thinner, they exhibit a problematic property where heat carriers (phonons and electrons) are scattered, making it more difficult for heat to be transferred. On the other hand, single-walled carbon nanotubes (Figure 1), with diameters on the nanometer scale (less than 1/10,000th the diameter of a human hair), are predicted to have an interesting property called ballistic conduction, where heat carriers conduct at ultra-high speeds. However, it is extremely difficult to visualize invisible phenomena like the thermal properties (such as thermal conductivity) of extremely small materials.

Figure 1: Carbon nanotube. A nanomaterial formed by rolling up a six-membered ring network of carbon atoms. They exhibit various properties depending on how they are rolled.

In our laboratory, we are developing original techniques to visualize the temperature and thermal properties of extremely small areas using light, such as lasers. For example, we are attempting to measure temperature by exciting nanometer-sized particles of light called near-field light and using these light particles (Figure 2). Probing "heat" in small areas requires tremendous enthusiasm and effort. Faculty and students are working together "passionately" as a team to elucidate new phenomena and properties (Figure 3).