Kwang Sup Lee

Improvement of Spatial Resolution in Nano-Stereolithography Using Radical Quencher

The improvement of spatial resolution is a fundamental issue in the two-photon, polymerization-based, laser writing. In this study, a voxel tuning method using a radical quencher was proposed to increase the resolution, and the quenching effect according to the amount of radical quencher was experimentally investigated. Employing the proposed method, the lateral resolution of the line patterns was improved almost to 100 nm. However, a shortcoming of the quenching effect was the low mechanical strength of polymerized structures due to their short chain lengths. Nano-indentation tests were conducted to evaluate quantitatively the relationship between mechanical strength and the mixture ratio of the radical quencher into the resins. The elastic modulus was dramatically reduced from an average value of 3.015 to 2.078 GPa when 5 wt% of radical quencher was mixed into the resin. Threedimensional woodpile structures were fabricated to compare the strength between the resin containing radical quencher and the original resin.

Improvement of two-photon induced photoreduction by using a metal ion solution with a high concentration of silver ions

Fabrication of three-dimensional metallic microstructures is an important issue for various applications in electronics and nanophotonics. Precise metallic micropatterns were fabricated by the two-photon induced photoreduction (TPPR) process. The process employs the photoreduction of silver ions in a metal ion solution composed of silver nitrate (AgNO3) and water-soluble polymer (poly(4-styrenesulfonique acid)). To improve the resolution and the uniformity of metallic micropatterns, a metal ion solution with a high concentration of silver ions was used, and the continuous forming window (CFW) of fabrication conditions was obtained by considering the mechanism of TPPR and heat effects during the process. Through this work, continuous silver lines and micropatterns with a minimum width of 560 nm were fabricated and their quality was verified.