**Acknowledgements**

Research described here was financially supported by the Ministry of Education, Japan through Grant‐in‐Aid for Scientific Research on the Priority‐Research‐Areas "Molecular NanoDynamics" and "Soft Matter Physics". We greatly appreciate the active participation of former graduate students at the beginning of the project: Kyosuke Inoue, Satonori Komatsu, Ken Ohdomari and Kazuhiro Sorioka. This experiment would not be successful without their great effort and elaboration.
