It is thrilling when you see something you have never seen before - The micro-nano world

Hedong Zhang
Associate Profressor

【Graduate School of Informatics】
Department of Complex Systems Science
【School of Informatics】
Department of Natural Informatics

Thin liquid film technology that provides a one nanometer gap between the disk and head in a hard disk drive

-Please tell us about your research.

My research is clarifying physical phenomena in the micro-nano domain and then creating devices and systems that have new functions and performance. More specifically, I want to contribute towards developing technology in the fields of precision equipment industry and medical treatment that uses the flow, wetting, lubrication and friction of thin film liquids through my research which clarifies and controls the characteristics of "thin liquid films" on solid surfaces.

As an example of research application, there is the hard disk drive (hereafter HDD). We have achieved an advanced information society due to the spread of the internet. The huge body of information accumulated on networks has allowed this to happen. Approximately 80% of digital information is stored on the HDD. However, operating a HDD consumes several watts of power per unit. During this rapid increase in digital information, the power consumption due to information equipment is expected to reach 20% of the total amount of domestic power generated in the year 2025. It is said that HDD must become more energy efficient to sustain the advancement of our advanced information society. For example, if the recording capacity of a single HDD increased by a factor of 30, you would be able to use a single HDD unit where 30 units were previously required. This means if you can store lots of information on a single HDD, the power consumption will decrease.

A HDD is mainly constructed from a disk and head of which the disk can be thought of as a writing pad and the head, which writes data, as a pen. Currently, the gap between the disk and head is 4 nm (a single nanometer is a billionth of a meter). The disk is made up of a collection of small magnets and decreasing the area of the magnet will increase the number of magnet which then allows the recording capacity of the HDD to increase. However, decreasing the magnets will weaken the magnetic force so the gap between the disk and head has to be decreased. Micronizing the gap from 4 nm to 1 nm is believed to allow the recording capacity to increase by a factor of around 30. However, this increases the risk of the disk breaking if the head makes contact with it as the disk is rotating at a speed of 100 km per hour. To prevent this type of risk, it is necessary to operate the disk with a thin liquid film of around 1 nm thickness sandwiched between the head and disk and coated on the surface of the disk. Therefore, it is necessary to ensure the thin liquid film is durable and has low adhesion and low friction properties.

The thin liquid film is exposed to ultra-violet rays through a mask that has sections that allow ultra-violet rays to penetrate and sections that don't allow this in order to provide the film with the necessary characteristics. The exposed sections become a hard film that is difficult to peel but the sections that are not exposed maintain the fluidity of the liquid and in case it peels off, the liquid is able to flow into the section and repair itself. By combining these two types of functions, we have improved the durability of the thin liquid film. In addition, we were successful in creating stability on the uneven surface of the liquid. The uneven surface reduces the contact surface with the head and provides the thin liquid film with low adhesion and low friction properties.

Creating new value through fusion

-What type of knowledge and awareness do you need?

When talking about "information", we tend to think of information on the internet. However, information can also be perceived as "information" as the structure of matter from the perspective of natural information. For example, we can say that this structure is available so this function is available. We can also perceive the "structure" itself as "information" with regards to the function. Natural science informatics is not just social phenomena but it is also the attempt to extract and analyze information contained in social phenomena and it creates new value by further fusing and combining information.

"Fusion" is very effective. By applying a relatively old idea from one field in a different field, new value can be created. The Department of Natural Science Informatics listens to what researchers who study various matters are saying. I think it is very important to actively acquire knowledge and a broad outlook that will become the foundation for "fusion" taking advantage of this type of environment.

It is interesting to discover something you have never seen before

-Why have you set your sights on this research?

I think many people like to travel. This is because they are highly motivated to see something they have never seen before. Research is the same. When you step into the micro-nano world, there are thrills that make you feel you are in a world of dreams different to the world we normally experience. This is appealing to me and I will never stop studying it.

I originally wanted to advance in the sciences and I find research itself, even if it is not my current research, to be interesting. I wanted to discover something that nobody had ever seen. There are many things we do not understand such as why does this phenomenon occur? It is fun to think in one's own way "Is this the reason it happens?" and then discover "Ah, that's why it happens." The process of looking for the answer is fun.

Confronting problems opens the door to a new world

-Do you have a message for students wishing to join the newly established school?

Research is here to resolve problems. I would like them to be conscious of the fact that solving a certain problem will lead to a certain type of future. However, the future is the accumulation of the present. I think it is important to act in the present while focusing on the future. I believe there are many things you cannot understand now and many problems to face. However, it is important to believe "This problem is a door to a new world!" and bravely challenge such problems. Even if you fail, there's always something you can learn from. It is always better than doing nothing. I want to tell them "Don't be afraid!" more than anything else.

Nagoya University is valued for its initiatives in supporting and cultivating female researchers and was selected in the top 10 universities that promote gender equality by the UN Women organization along with such universities as Oxford University in England. During my own time as a student, I was responsible for my own future. I thought I would fulfill my responsibility to society as a single person within it. I would like my students to have this kind of sense of responsibility that has no regard for gender. Also, when I became a mother, I felt strongly about creating a better future for my daughter. I take pride in saying "I also have contributed towards society even a little". I would also like all my students to have this type of pride for those people who follow their own generation.