A new e-beam resist

Professor Sunghwan Kim at Ajou University has developed a way of using natural silk extracted from cocoons in nano processes. Natural silk is expected to replace the harmful chemical materials that are now being used in nano unit processes since natural silk is harmless to the human body and comparable in performance. Professor Kim’s discovery was posted on Nature's website Nature Nanotechnology on March 23rd, with the title of "All-water-based electron-beam lithography using silk as a resist." Professor Sunghwan Kim is the first author of the paper, and a team led by Professor Fiorenzo Omenetto of Biomedical Engineering from Tufts University in the U.S., also participated in the research. In the paper, Professor Kim and the Professor Omenetto-led team showed that natural silk protein extracted from cocoons can be used in nano-level processes. The only material involved in the process is water, which demonstrates that eco- and bio-friendly processes can be achieved. Lithography utilized in the first phase for making nano elements requires a material called “resist” that reacts to an electronic beam or light, and the team led by Professor Kim used natural silk as the resist. Harmful chemical materials such as benzene or hydrofluoric acid are currently used in nano processes, including those for making semi-conductors. This has been a substantial challenge to overcome in applying nano technology to bio fields. In the paper, Professor Kim confirmed that, in terms of performance, silk did not fall behind the artificial synthetic resists already commercialized as resist materials for electron-beam lithography. When silk is used in electron-beam lithography for nano processes, it allows up to 10 nano meter patterning, which is the same level as existing resists. In addition to the comparable development performance, silk is also competitive in terms of cost, since it can use over 70 percent of cocoons as they are. During the research, the team also discovered that silk resist can be combined with biological functional materials such as enzymes to use in nano unit bio sensors or bio markers. According to the paper, by utilizing silk, they can make highly efficient bio devices that react even to the slightest body fluid or blood. Professor Kim said: “There has been active research of silk as a base material enabling eco-friendly nano elements,” adding that “This paper is significant in that it identified silk as a natural element and base material helping the convergence with biotechnology (BT) as well as with nano technology (NT) and information technology (IT).”