A Liquid Whose Properties Change with Magnets

Participant Profile

Tatsuo Sawada

Tatsuo Sawada

Tatsuo Sawada (Professor, Department of Mechanical Engineering)

While water and air do not have special functions in themselves, the magnetic fluid introduced here is a liquid that sticks to magnets. When you pour water into a beaker, it naturally collects at the bottom. This is because gravity acts on the water. If you put a magnetic fluid in a beaker and bring a magnet underneath it, the fluid is further drawn to the bottom of the beaker by the magnet. In other words, the fluid is subjected to both gravitational and magnetic forces. This corresponds to an apparent increase in gravity.

So, what happens if you bring the magnet above the beaker? The magnetic fluid inside the beaker is subjected to an upward force by the magnet, counteracting gravity. This means that gravity is apparently reduced. When the magnetic force is comparable in strength to gravity, a state close to zero gravity can be created within the magnetic fluid. This allows us to reproduce a near-zero-gravity state on Earth.

Magnetic fluids contain extremely small magnetic microparticles. Their average diameter is about 10 nanometers. The three figures on the left show what happens when a magnetic field is applied to a magnetic fluid. These are microscope photographs. Figure 1 shows the moment immediately after the magnetic field is applied. You can't see anything. As time passes, thin structures like those shown in Figure 2 and Figure 3 begin to form. This is because clusters of the internal magnetic microparticles align in the direction of the magnetic field, creating chain-like structures. When such distinct structures form within the liquid, its properties also change significantly. I am interested in and conduct research on fluids that exhibit various properties in response to magnetic and electric fields like these.

Now, in a university laboratory, there are young colleagues ranging from undergraduate to graduate students. We conduct research together and sometimes go out for fun, forming strong, lifelong bonds. When we conduct research, we present the results at academic conferences. Figure 4 is a photo from an international conference held in Germany in late August 2008, where a graduate student (an international student from Indonesia) received an award for a poster presentation from among nearly 100 participants from around the world. Figure 5 is a photo from a laboratory ski trip. The one wearing sunglasses is me.

My motto is to conduct research at a world-class level and, when it's time to have fun, to enjoy it to the fullest, just like the students. I believe many high school students are also viewing this website. Please strike a good balance between your studies and recreation to lead a meaningful student life.