Nature Reviews Materials (2019) https://doi.org/10.1038/s41578-019-0135-y Published online 16 August 2019

This article was originally published with two errors in the main text. In the second paragraph of the introduction, kPa should have been Pa; and in the footnote for Table 3, ‘matrix metalloprotease’ should have been ‘matrix metalloproteinase’. This has been corrected both in the PDF and in the HTML versions of the article.