1. Institute of Polymer Science and Engineering; National Taiwan University; No. 1, Sec. 4 Roosevelt Road Taipei 10617 Taiwan R.O.C.
2. Department of Mechanical Engineering; National Central University; Taoyuan 32001 Taiwan R.O.C.
3. Research Center for Developmental Biology and Regenerative Medicine; National Taiwan University; Taipei 10617 Taiwan R.O.C.