Nature Reviews Materials https://doi.org/10.1038/s41578-018-0006-y (2018) Published online 26 April 2018

This article was originally published with incorrect affiliations for Sang Jin Lee, Yuya Morimoto, Shoji Takeuchi and James J. Yoo. Please see below the correct affiliations.

Yuya Morimoto and Shoji Takeuchi: Institute of Industrial Science, University of Tokyo, Tokyo, Japan

Sang Jin Lee and James J. Yoo: Wake Forest Institute for Regenerative Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA

The article was further published with an incorrect colour code in Fig. 2b. This error has been corrected, and uncrosslinked material is now shown in purple and crosslinked material in green.

We apologize to the authors and our readers for these errors.