1. Department of Stomatology, Dental Digital Medicine and 3D Printing Engineering Laboratory of Qingdao University, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266003, P.R. China
2. Department of Burn and Plastic Surgery, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266003, P.R. China
3. Department of Physical and Biological Sciences, University of California, Santa Cruz, CA 95064, USA