Applications of Diamond-like Carbon (DLC) in a variety of fields

The keyword in the Tetsuya Suzuki Laboratory of the Department of Mechanical Engineering at Keio University is ''nanomaterials''. The researchers in the Suzuki Lab are working to develop high-performance thin-film materials and to analyze such materials at the atomic level. In particular, Diamond-like Carbon, or DLC for short, is the main target. The researchers improve the DLC films and apply them in a variety of fields.

DLC is an amorphous carbon film with the same quality as diamond. It is superior in terms of hardness, smoothness, gas barrier performance and biocompatibility. It's already applied to some fields such as PET bottles and automotive components.

"We synthesize films from gases and apply them in a variety of fields. It's only been about 30 years since researchers were able to synthesize DLC from gases. It's synthesized by decomposing hydrocarbon gases and stacking individual atoms. And DLC is similar in structure to diamond. Diamond we know as a gemstone has mechanical properties that make it useful as more than just a gemstone. It's extremely hard, the best conductor of heat. Moreover, it doesn't let gases pass through because it is high-density. DLC also has those properties. Our research is the application of the DLC films which has those properties in a variety of fields."

One issue in many applications of DLC is reducing the cost of synthesizing DLC films. To synthesize DLC films quickly and at low cost, the Suzuki Lab is working to synthesize them at atmospheric pressure without vacuum equipment previously needed. However, it's been pointed out that the DLC films synthesized at atmospheric pressure have lower performance than those synthesized under vacuum conditions. So, the researchers are improving the performance of DLC films synthesized at atmospheric pressure.

"We place a great emphasis on international competitiveness. I think one problem of researches in universities is that researchers make good things regardless of high cost. Even when a researcher comes out with a new product, it won't be widely accepted if it costs ten times as much as an old one to perform twice as well. It is not until we develop a higher-performance product than an old one at about the same low price that it will attract many companies from different industries and it can be applied in a variety of fields."

The stent, which is a medical instrument, is one of the applications of DLC films. The Suzuki Lab is currently developing DLC-coated stents as commercial products. Stents play a role in dilating narrow blood vessels. It's been confirmed that DLC-coated stents are smoother, which inhibits clotting.

In addition, the Suzuki Lab develops low-cost solar cells using DLC films, cutting tools coated with hard films and sliding components coated with diamond films.

"For example, DLC films have been applied in the automotive window which is accounts for a large part in the heavy. Automakers have used plastic for the windshield and rear window which inevitably get scratched for a long time. And coating the windows with DLC films can prevent them getting scratched, by either fingernails or grit. One way to coat a large area cheaply with the DLC is a thin-film-forming technology using atmospheric-pressure plasma. To sum up, as I often mention in research papers, improving three characteristics of DLC - hardness, gas barrier performance and antithrombogenicity - lead to contribute to society in the various fields, I think."