1. Department of Nano-Mechanics, Korea Institute of Machinery & Materials (KIMM), 156 Gajungbuk-ro, Yuseong-gu, Daejeon 305-343, South Korea
2. Department of Organic Materials & Fiber Engineering, Chonbuk National University, Jeonju 561-756, South Korea
3. School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, South Korea
4. Department of Ultra-Precision System, Korea Institute of Machinery & Materials (KIMM), 156 Gajungbuk-ro, Yuseong-gu, Daejeon 305-343, South Korea