1. Bioinspired Soft Matter Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa 904-0495 Japan
2. Imaging Section, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan
3. SM Application Group, JEOL Ltd., Akishima, Tokyo 196-8558, Japan