* Corresponding authors

^a WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
E-mail: hxchang@wpi-aimr.tohoku.ac.jp

^b Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan

^c Graduate School of Environmental Studies, Tohoku University, Sendai 980-8579, Japan

^d Centre for Stem Cell Research, A unit of the Institute for Stem Cell Biology and Regenerative Medicine, Christian Medical College Campus, Vellore 632002, India

^e Institut National de la Santé Et de la Recherche Médicale U977, Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg 67085, France

^f Department of Chemistry, The Hong Kong University of Science and Technology, Clear water Bay, Hong Kong

^g Department of Medicine, Center for Biomedical Engineering, Brigham and Women's Hospital, Harvard Medical School, Cambridge, Massachusetts 02139, USA

^h Harvard–MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

ⁱ Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts 02115, USA

^j Department of Maxillofacial Biomedical Engineering and Institute of Oral Biology, School of Dentistry, Kyung Hee University, Seoul 130-701, Republic of Korea
E-mail: alik@rics.bwh.harvard.edu